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PROFESSOR: OK, let's just
take 10 more seconds

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00:00:48,540 --> 00:01:02,950
on the clicker question.

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00:01:02,950 --> 00:01:09,650
OK, 76, I think that says, %,
which is not bad, but we

11
00:01:09,650 --> 00:01:12,580
should be at 100%.

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00:01:12,580 --> 00:01:17,210
So, when you're past the
equivalence point, so you've

13
00:01:17,210 --> 00:01:20,830
converted all of your weak,
in this case, acid to its

14
00:01:20,830 --> 00:01:25,420
conjugate base, and because it
was a weak acid, the conjugate

15
00:01:25,420 --> 00:01:28,550
base is going to be a weak
based and so it's not

16
00:01:28,550 --> 00:01:31,900
contributing a whole lot it'll
make the solution basic, but

17
00:01:31,900 --> 00:01:35,740
it's nothing compared to adding
strong base in there.

18
00:01:35,740 --> 00:01:38,720
So even though you have the
weak base around, at this

19
00:01:38,720 --> 00:01:41,320
point it's really a strong
base problem.

20
00:01:41,320 --> 00:01:45,760
So you would calculate this by
looking at how many mils of

21
00:01:45,760 --> 00:01:49,400
the strong base you've added
past, and figure out the

22
00:01:49,400 --> 00:01:52,860
number of moles that there
are, and divide

23
00:01:52,860 --> 00:01:54,460
by the total volume.

24
00:01:54,460 --> 00:01:57,960
So this was like one of the
problems on the exam, and one

25
00:01:57,960 --> 00:02:00,230
thing that I thought was
interesting on the exam is

26
00:02:00,230 --> 00:02:03,200
that more people seemed to get
the hard problem right than

27
00:02:03,200 --> 00:02:05,840
this, which was the
easy problem.

28
00:02:05,840 --> 00:02:10,770
So we'll see on the final, there
will be an acid based

29
00:02:10,770 --> 00:02:14,450
titration problem on the
final, at least one.

30
00:02:14,450 --> 00:02:19,390
So let's see if we can get,
then, the easy and the hard

31
00:02:19,390 --> 00:02:20,140
ones right.

32
00:02:20,140 --> 00:02:22,770
So you've mastered the hard ones
and let's see if you can

33
00:02:22,770 --> 00:02:29,100
learn how to do the easy ones
as well for the final exam.

34
00:02:29,100 --> 00:02:33,390
OK, so we're going to continue
with transition metals.

35
00:02:33,390 --> 00:02:37,040
We were talking about crystal
field theory and magnetism,

36
00:02:37,040 --> 00:02:40,880
and you should have a handout
for today, and you should also

37
00:02:40,880 --> 00:02:47,610
have some equipment to make
models of orbitals and

38
00:02:47,610 --> 00:02:51,420
coordination complexes --
these are not snacks.

39
00:02:51,420 --> 00:02:59,970
They can be snacks later, right
now they're a model kit.

40
00:02:59,970 --> 00:03:05,440
All right, so I'm going to
introduce you to some terms

41
00:03:05,440 --> 00:03:09,150
that we're going to come back
you at the end of today's

42
00:03:09,150 --> 00:03:12,650
lecture, and then we're going
to talk about the shapes of

43
00:03:12,650 --> 00:03:14,890
coordination complexes.

44
00:03:14,890 --> 00:03:18,050
So, magnetism.

45
00:03:18,050 --> 00:03:21,780
So we talked last time, before
the exam, if you remember,

46
00:03:21,780 --> 00:03:24,130
about high spin and
low spin, unpaired

47
00:03:24,130 --> 00:03:26,570
electrons and paired electrons.

48
00:03:26,570 --> 00:03:29,700
Well, compounds that have
unpaired electrons are

49
00:03:29,700 --> 00:03:32,850
paramagnetic, they're attracted
by a magnetic field,

50
00:03:32,850 --> 00:03:36,580
and those where the electrons
are paired are diamagnetic are

51
00:03:36,580 --> 00:03:38,560
repelled by a magnetic field.

52
00:03:38,560 --> 00:03:43,450
So you can tell whether a
coordination complex is

53
00:03:43,450 --> 00:03:46,110
paramagnetic or diamagnetic,
you can test the magnetism,

54
00:03:46,110 --> 00:03:51,390
and that'll give you some
information about the electron

55
00:03:51,390 --> 00:03:53,930
configuration of the
d orbitals in that

56
00:03:53,930 --> 00:03:55,930
coordination complex.

57
00:03:55,930 --> 00:03:59,380
And that can tell you
about the geometry.

58
00:03:59,380 --> 00:04:02,280
And so you'll see that by the
end we're going to talk about

59
00:04:02,280 --> 00:04:06,100
different types of energy
orbitals when you have

60
00:04:06,100 --> 00:04:07,560
different geometries.

61
00:04:07,560 --> 00:04:09,670
So why might you care about the

62
00:04:09,670 --> 00:04:11,860
geometry of a metal center.

63
00:04:11,860 --> 00:04:14,510
Well, people who study proteins
that have metal

64
00:04:14,510 --> 00:04:17,350
centers care a lot about
the geometry of them.

65
00:04:17,350 --> 00:04:20,280
So let me just give
you one example.

66
00:04:20,280 --> 00:04:25,210
We talked a lot about energy in
the course this semester,

67
00:04:25,210 --> 00:04:28,330
so we need catalysts for
removing carbon monoxide and

68
00:04:28,330 --> 00:04:31,090
carbon dioxide from
the environment.

69
00:04:31,090 --> 00:04:35,020
And nature has some of these --
they have metal cofactors

70
00:04:35,020 --> 00:04:37,650
and proteins that can do this,
and people have been

71
00:04:37,650 --> 00:04:40,730
interested in mimicking that
chemistry to remove these

72
00:04:40,730 --> 00:04:43,060
gases from the environment.

73
00:04:43,060 --> 00:04:47,380
So let me tell you these enzymes
are organisms. And

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00:04:47,380 --> 00:04:52,870
this is pretty amazing, some of
these microorganisms. So,

75
00:04:52,870 --> 00:04:55,030
over here there's one
-- it basically

76
00:04:55,030 --> 00:04:57,110
lives on carbon monoxide.

77
00:04:57,110 --> 00:05:00,550
I mean that's -- you know
alternative sources of energy

78
00:05:00,550 --> 00:05:02,710
are one thing, but that's really
quite a crazy thing

79
00:05:02,710 --> 00:05:03,880
that this guy does.

80
00:05:03,880 --> 00:05:06,840
So, you can grow it up in these
big vats and pump in

81
00:05:06,840 --> 00:05:11,730
carbon monoxide and it's like
oh, food, and they grow and

82
00:05:11,730 --> 00:05:14,690
multiply, and they're very,
very happy in this carbon

83
00:05:14,690 --> 00:05:16,350
monoxide environment.

84
00:05:16,350 --> 00:05:19,880
There are also microorganisms
that live on carbon dioxide as

85
00:05:19,880 --> 00:05:23,120
their energy and a
carbon source.

86
00:05:23,120 --> 00:05:27,120
And so these organisms have
enzymes in them that have

87
00:05:27,120 --> 00:05:30,760
metal centers, and those metal
centers are responsible for

88
00:05:30,760 --> 00:05:34,800
the ability of these organisms
to live on these kind of

89
00:05:34,800 --> 00:05:37,820
bizarre greenhouse gases
and pollutants.

90
00:05:37,820 --> 00:05:41,090
So people would like to
understand how this works.

91
00:05:41,090 --> 00:05:43,870
So microbes have been estimated
to remove hundred, a

92
00:05:43,870 --> 00:05:46,870
million tons of carbon monoxide
from the environment

93
00:05:46,870 --> 00:05:50,640
every year, producing about
one trillion kilograms of

94
00:05:50,640 --> 00:05:53,840
acetate from these
greenhouse gases.

95
00:05:53,840 --> 00:05:56,600
And so, what do these catalysts
look like and these

96
00:05:56,600 --> 00:05:59,340
enzymes, what do these metal
clusters look like that do

97
00:05:59,340 --> 00:06:00,480
this chemistry.

98
00:06:00,480 --> 00:06:03,990
And this was sort of a rough
model of what they look like,

99
00:06:03,990 --> 00:06:06,820
and they thought it had iron and
sulfur and then a nickel

100
00:06:06,820 --> 00:06:09,770
in some geometry, but they had
no idea sort of where the

101
00:06:09,770 --> 00:06:12,590
nickel was and how it
was coordinated.

102
00:06:12,590 --> 00:06:15,150
And so before there was any
kind of three dimensional

103
00:06:15,150 --> 00:06:18,170
information, they used
spectroscopy, and they

104
00:06:18,170 --> 00:06:21,110
considered whether it was
paramagnetic or diamagnetic to

105
00:06:21,110 --> 00:06:24,070
get a sense of what the geometry
around the metal was.

106
00:06:24,070 --> 00:06:26,300
So we're going to talk about
different coordination

107
00:06:26,300 --> 00:06:30,860
geometries and how many unpaired
or paired electrons

108
00:06:30,860 --> 00:06:33,930
you would expect, depending
on those geometries today.

109
00:06:33,930 --> 00:06:38,220
And so, crystal field theory,
again, can help you help

110
00:06:38,220 --> 00:06:42,190
explain/rationalize the
properties of these transition

111
00:06:42,190 --> 00:06:46,350
metal complexes or coordination
complexes.

112
00:06:46,350 --> 00:06:50,940
So, to help us think about
geometry, I always find for

113
00:06:50,940 --> 00:06:54,810
myself that it's helpful
to have models.

114
00:06:54,810 --> 00:07:01,410
So not everyone can have such
large models as these, but you

115
00:07:01,410 --> 00:07:06,580
can all have your own little
models of these geometries.

116
00:07:06,580 --> 00:07:10,670
So, what we have available
to you are some mini

117
00:07:10,670 --> 00:07:14,400
marshmallows, which, of course,
as we all know, are

118
00:07:14,400 --> 00:07:19,160
representative of d orbitals,
and jelly beans, which we all

119
00:07:19,160 --> 00:07:22,800
know are useful for making
coordination complexes.

120
00:07:22,800 --> 00:07:27,580
So, what you can do with your
mini marshmallows is you can

121
00:07:27,580 --> 00:07:30,610
put together to make your
different sets.

122
00:07:30,610 --> 00:07:37,520
And so, over here we have -- oh,
actually it says gum drops

123
00:07:37,520 --> 00:07:39,810
-- you don't have gum drops this
year, I changed up here,

124
00:07:39,810 --> 00:07:41,120
I forgot to change
it down here.

125
00:07:41,120 --> 00:07:42,960
We have mini marshmallows.

126
00:07:42,960 --> 00:07:47,440
Dr. Taylor went out and tried
to purchase enough gum drops

127
00:07:47,440 --> 00:07:50,890
to do this experiment, and
discovered that Cambridge only

128
00:07:50,890 --> 00:07:54,580
had 300 gum drops,
so we have mini

129
00:07:54,580 --> 00:07:56,690
marshmallows instead today.

130
00:07:56,690 --> 00:07:57,850
But this gives you the idea.

131
00:07:57,850 --> 00:08:02,660
You can take one toothpick and
you can make d z squared,

132
00:08:02,660 --> 00:08:06,120
putting on your orbitals, you
have your donut in the middle,

133
00:08:06,120 --> 00:08:09,500
and then your two lobes, which
run along the z-axis.

134
00:08:09,500 --> 00:08:16,450
And then for your other sets
of orbitals, you can take

135
00:08:16,450 --> 00:08:21,800
these two toothpicks and put
on these sets of mini

136
00:08:21,800 --> 00:08:26,620
marshmallows, and handily, you
can just have one for all of

137
00:08:26,620 --> 00:08:30,410
the other d orbitals, because
depending on how you hold it,

138
00:08:30,410 --> 00:08:32,910
it can represent all
of the other d

139
00:08:32,910 --> 00:08:35,190
orbitals just very well.

140
00:08:35,190 --> 00:08:38,240
So, you can just have one of
these for all the others and

141
00:08:38,240 --> 00:08:40,330
then your d z squared.

142
00:08:40,330 --> 00:08:44,410
So what we're going to do when
we have our orbitals set up,

143
00:08:44,410 --> 00:08:49,080
then we can think about how
ligands in particular

144
00:08:49,080 --> 00:08:52,870
positions, in particular
geometries would clash with

145
00:08:52,870 --> 00:08:56,000
our orbitals -- where there'd
be big repulsions or small

146
00:08:56,000 --> 00:08:59,230
repulsions.

147
00:08:59,230 --> 00:09:04,030
So, any other people missing
their jelly beans or their

148
00:09:04,030 --> 00:09:05,900
marshmallows?

149
00:09:05,900 --> 00:09:34,650
Please, raise your hand,
we have extras.

150
00:09:34,650 --> 00:09:36,870
So, those of you who have
them, go ahead and start

151
00:09:36,870 --> 00:10:08,730
making your d orbitals.

152
00:10:08,730 --> 00:10:54,410
All right, so if you're finished
with your two d

153
00:10:54,410 --> 00:11:01,990
orbitals, you can start making
an octahedral complex.

154
00:11:01,990 --> 00:11:05,670
So in your geometries set,
you'll have a big gum which

155
00:11:05,670 --> 00:11:11,100
can be your center metal --
you'll have a big jelly bean

156
00:11:11,100 --> 00:11:13,540
-- sorry, big jelly beans and
small jelly beans are our

157
00:11:13,540 --> 00:11:17,470
ligands, or our negative point
charges, and you can set up

158
00:11:17,470 --> 00:13:05,900
and make an octahedral
geometry here.

159
00:13:05,900 --> 00:13:10,610
OK, so as you're finishing this
up, I'm going to review

160
00:13:10,610 --> 00:13:13,480
what we talked about before the
exam -- so this isn't in

161
00:13:13,480 --> 00:13:15,820
today's lecture handouts, it
was in last time, which we

162
00:13:15,820 --> 00:13:17,100
already went over.

163
00:13:17,100 --> 00:13:20,040
But sometimes I've discovered
that when there's an exam in

164
00:13:20,040 --> 00:13:23,340
the middle, there needs to be
a bit of a refresher, it's

165
00:13:23,340 --> 00:13:28,470
hard to remember what happened
before the exam, and you have

166
00:13:28,470 --> 00:13:31,050
your models to think
about this.

167
00:13:31,050 --> 00:13:34,360
So, before the exam, we had
talked about the octahedral

168
00:13:34,360 --> 00:13:38,850
case, and how compared to a
spherical situation where the

169
00:13:38,850 --> 00:13:41,080
ligands are everywhere
distributed around the metals

170
00:13:41,080 --> 00:13:45,570
where all d orbitals would be
affected/repulsed by the

171
00:13:45,570 --> 00:13:50,580
ligands in a symmetric fashion
equally, when you have them

172
00:13:50,580 --> 00:13:54,580
put as particular positions in
geometry, then they're going

173
00:13:54,580 --> 00:13:57,000
to affect the different d
orbitals differently.

174
00:13:57,000 --> 00:14:00,600
And so, if you have your d z
squared made, and you have

175
00:14:00,600 --> 00:14:03,930
your octahedral made, you can
sort of hold these up and

176
00:14:03,930 --> 00:14:08,680
realize that you would have
repulsion from your ligands

177
00:14:08,680 --> 00:14:12,080
along the z-axis directly
toward your

178
00:14:12,080 --> 00:14:14,410
orbitals from d z squared.

179
00:14:14,410 --> 00:14:16,560
So that would be highly
repulsive.

180
00:14:16,560 --> 00:14:20,490
The ligands are along the
z-axis, the d orbitals are

181
00:14:20,490 --> 00:14:23,580
along the z-axis, so the
ligands, the negative point

182
00:14:23,580 --> 00:14:25,100
charge ligands are going
to be pointing

183
00:14:25,100 --> 00:14:27,960
right toward your orbitals.

184
00:14:27,960 --> 00:14:34,000
And if you hold up this as a d
x squared y squared orbital

185
00:14:34,000 --> 00:14:38,670
where the orbitals are right
along the x-axis and right

186
00:14:38,670 --> 00:14:41,660
along the y-axis and you hold
that up, remember, your

187
00:14:41,660 --> 00:14:43,720
ligands are right along
the x-axis and

188
00:14:43,720 --> 00:14:45,390
right along the y-axis.

189
00:14:45,390 --> 00:14:49,620
So, you should also have
significant repulsion for d x

190
00:14:49,620 --> 00:14:53,940
squared minus y squared, and
octahedrally oriented ligands.

191
00:14:53,940 --> 00:15:01,500
In contrast, the ligands set
that are 45 degrees off-axis,

192
00:15:01,500 --> 00:15:08,130
so d y z, d x z, and d x y,
they're all 45 degrees off.

193
00:15:08,130 --> 00:15:12,880
Your ligands are along the axis,
but your orbitals are 45

194
00:15:12,880 --> 00:15:14,610
degrees off-axis.

195
00:15:14,610 --> 00:15:16,840
So if you look at that together,
you'll see that

196
00:15:16,840 --> 00:15:19,530
whichever one you look at, the
ligands are not going to be

197
00:15:19,530 --> 00:15:22,210
pointing directly toward
those d orbitals.

198
00:15:22,210 --> 00:15:24,930
The orbitals are off-axis,
ligands are on-axis.

199
00:15:24,930 --> 00:15:29,790
So there will be much smaller
repulsions there.

200
00:15:29,790 --> 00:15:36,970
And that we talked about the
fact that for d x squared

201
00:15:36,970 --> 00:15:40,360
minus y squared and d z squared,
they're both have

202
00:15:40,360 --> 00:15:43,410
experienced large repulsions,
they're both degenerate in

203
00:15:43,410 --> 00:15:47,010
energy, they go up in energy,
whereas these three d

204
00:15:47,010 --> 00:15:50,750
orbitals, smaller repulsion,
and they're also degenerate

205
00:15:50,750 --> 00:15:53,780
with respect to each other,
and they're stabilized

206
00:15:53,780 --> 00:15:55,420
compared to these
guys up here.

207
00:15:55,420 --> 00:15:58,680
So you can try to hold those up
and convince yourself that

208
00:15:58,680 --> 00:16:01,750
that's true for the
octahedral case.

209
00:16:01,750 --> 00:16:04,050
So, that's what we talked about
last time, and now we

210
00:16:04,050 --> 00:16:07,740
want to -- oh, and I'll just
remind you we looked at these

211
00:16:07,740 --> 00:16:09,950
splitting diagrams as well.

212
00:16:09,950 --> 00:16:13,010
We looked at the average energy
of the d orbitals -- d

213
00:16:13,010 --> 00:16:16,250
z squared and d x squared
minus y squared go up in

214
00:16:16,250 --> 00:16:18,970
energy, and then the
other three d

215
00:16:18,970 --> 00:16:24,310
orbitals go down in energy.

216
00:16:24,310 --> 00:16:28,250
So now we want to consider what
happens with different

217
00:16:28,250 --> 00:16:31,850
geometries.

218
00:16:31,850 --> 00:16:36,040
So now you can turn your
octahedral case into a square

219
00:16:36,040 --> 00:16:42,040
planar case, and how am
I going to do that?

220
00:16:42,040 --> 00:16:45,440
Yeah, so we can just take off
the top and the bottom and we

221
00:16:45,440 --> 00:16:51,910
have our nice square planar
case, and try to make a

222
00:16:51,910 --> 00:16:57,020
tetrahedral complex as well.

223
00:16:57,020 --> 00:16:59,450
And here's an example of
a tetrahedral one.

224
00:16:59,450 --> 00:17:02,200
Again, you can take a jelly bean
in the middle, and big

225
00:17:02,200 --> 00:17:05,070
jelly bean, and then the smaller
ones on the outside.

226
00:17:05,070 --> 00:17:08,560
So what angles am I going for
here in the tetrahedral case?

227
00:17:08,560 --> 00:17:10,590
109 .

228
00:17:10,590 --> 00:17:11,410
5.

229
00:17:11,410 --> 00:17:16,190
So you can go ahead and make
your tetrahedral complex, and

230
00:17:16,190 --> 00:17:17,890
don't worry so much
about the 0 .

231
00:17:17,890 --> 00:18:36,430
5, but we'll see if people can
do a good job with the 109.

232
00:18:36,430 --> 00:18:40,730
OK, how are your tetrahedral
complexes coming?

233
00:18:40,730 --> 00:18:46,660
Do they look like
this sort of?

234
00:18:46,660 --> 00:18:49,830
So let me define for you how
we're going to consider the

235
00:18:49,830 --> 00:18:52,090
tetrahedral case.

236
00:18:52,090 --> 00:18:56,860
So, in the tetrahedral case,
we're going to have the x-axis

237
00:18:56,860 --> 00:19:00,700
comes out of the plane, the
y-axis is this way, z-axis

238
00:19:00,700 --> 00:19:02,130
again, up and down.

239
00:19:02,130 --> 00:19:05,000
We're going to have one ligand
coming out here, another going

240
00:19:05,000 --> 00:19:08,120
back, and then these two are
pretty much in the plane of

241
00:19:08,120 --> 00:19:09,140
the screen.

242
00:19:09,140 --> 00:19:11,510
So this is sort of how I'm
holding the tetrahedral

243
00:19:11,510 --> 00:19:18,420
complex with respect to the x,
z, and y coordinate system.

244
00:19:18,420 --> 00:19:21,910
So, there is a splitting, energy
splitting, associated

245
00:19:21,910 --> 00:19:25,050
with tetrahedral, and it's
going to be smaller than

246
00:19:25,050 --> 00:19:29,880
octahedral because none of these
ligands will be pointing

247
00:19:29,880 --> 00:19:31,510
directly toward the orbitals.

248
00:19:31,510 --> 00:19:36,590
But let's consider which
orbitals are going to be most

249
00:19:36,590 --> 00:19:42,850
affected by a tetrahedral
case.

250
00:19:42,850 --> 00:19:48,480
So, let's consider
d z squared.

251
00:19:48,480 --> 00:19:49,780
What do you think?

252
00:19:49,780 --> 00:19:51,790
Is that going to be particularly
-- are the

253
00:19:51,790 --> 00:19:55,280
ligands pointing toward
d z squared?

254
00:19:55,280 --> 00:19:57,340
No.

255
00:19:57,340 --> 00:20:02,010
And d x squared minus y squared,
we can think of, what

256
00:20:02,010 --> 00:20:04,310
about that one?

257
00:20:04,310 --> 00:20:06,680
No, not really.

258
00:20:06,680 --> 00:20:12,320
What about d x y, d
y z, and d x y?

259
00:20:12,320 --> 00:20:17,090
Moreso.

260
00:20:17,090 --> 00:20:20,320
So, if you try holding up your
tetrahedral in our coordinate

261
00:20:20,320 --> 00:20:25,720
system, and then hold your d
orbitals 45 degrees off-axis,

262
00:20:25,720 --> 00:20:28,710
it's not perfect, they're not
pointing directly toward them,

263
00:20:28,710 --> 00:20:31,840
but it's a little closer than
for the d orbitals that are

264
00:20:31,840 --> 00:20:36,080
directly on-axis.

265
00:20:36,080 --> 00:20:41,180
So, if we look at this, we see
that the orbitals are going to

266
00:20:41,180 --> 00:20:46,230
be split in the exact opposite
way of the octahedral system.

267
00:20:46,230 --> 00:20:50,040
In the octahedral system, the
ligands are on-axis, so the

268
00:20:50,040 --> 00:20:53,940
orbitals that are on-axis, d x
squared minus y squared and d

269
00:20:53,940 --> 00:20:56,520
z squared are going to
be the most affected.

270
00:20:56,520 --> 00:21:00,170
But with tetrahedral, the
ligands are off-axis, so the d

271
00:21:00,170 --> 00:21:02,750
orbitals that are also off-axis
are going to be the

272
00:21:02,750 --> 00:21:03,820
most affected.

273
00:21:03,820 --> 00:21:06,720
But they're not going to be as
dramatically affected, so the

274
00:21:06,720 --> 00:21:09,980
splitting is actually smaller
in this case.

275
00:21:09,980 --> 00:21:14,030
So here, with tetrahedral, you
have the opposite of the

276
00:21:14,030 --> 00:21:16,080
octahedral system.

277
00:21:16,080 --> 00:21:19,690
And you can keep these and try
to convince yourself of that

278
00:21:19,690 --> 00:21:25,570
later if you have trouble
visualizing it.

279
00:21:25,570 --> 00:21:29,270
So, you'll have more repulsion
between the ligands as

280
00:21:29,270 --> 00:21:32,350
negative point charges, and
the d orbitals that are 45

281
00:21:32,350 --> 00:21:36,240
degrees off-axis than you do
with the two d orbitals that

282
00:21:36,240 --> 00:21:39,960
are on-axis.

283
00:21:39,960 --> 00:21:44,110
So here, d x squared minus y
squared and d z squared have

284
00:21:44,110 --> 00:21:46,720
the same energy with respect
to each other, they're

285
00:21:46,720 --> 00:21:47,980
degenerate.

286
00:21:47,980 --> 00:21:54,920
And we have our d y z, x z, and
x y have the same energy

287
00:21:54,920 --> 00:21:58,490
with respect to each other,
they are also degenerate.

288
00:21:58,490 --> 00:22:02,780
So it's the same sets that are
degenerate as with octahedral,

289
00:22:02,780 --> 00:22:08,480
but they're all affected
differently.

290
00:22:08,480 --> 00:22:13,660
So now let's look at the energy
diagrams and compare

291
00:22:13,660 --> 00:22:17,350
the octahedral system with
the tetrahedral system.

292
00:22:17,350 --> 00:22:21,280
Remember an octahedral, we had
the two orbitals going up and

293
00:22:21,280 --> 00:22:22,880
three going down.

294
00:22:22,880 --> 00:22:25,570
The splitting, the energy
difference between them was

295
00:22:25,570 --> 00:22:26,930
abbreviated.

296
00:22:26,930 --> 00:22:29,440
The octahedral crystal field
splitting energy, with a

297
00:22:29,440 --> 00:22:31,350
little o for octahedral.

298
00:22:31,350 --> 00:22:35,370
We now have a t for tetrahedral,
so we have a

299
00:22:35,370 --> 00:22:37,410
different name.

300
00:22:37,410 --> 00:22:41,000
And so here is now our
tetrahedral set.

301
00:22:41,000 --> 00:22:44,470
You notice it's the opposite of
octahedral, so the orbitals

302
00:22:44,470 --> 00:22:49,880
that were most destabilized in
the octahedral case are now

303
00:22:49,880 --> 00:22:54,190
more stabilized down here, so
we've moved down in energy.

304
00:22:54,190 --> 00:22:58,670
And the orbitals that are
off-axis, 45 degrees off-axis,

305
00:22:58,670 --> 00:23:02,670
which were stabilized in the
octahedral system, because

306
00:23:02,670 --> 00:23:05,430
none of ligands were pointing
right toward them, now those

307
00:23:05,430 --> 00:23:09,200
ligands are a bit closer so they
jump up in energy, and so

308
00:23:09,200 --> 00:23:15,260
we have this swap
between the two.

309
00:23:15,260 --> 00:23:18,760
So, we have some new
labels as well.

310
00:23:18,760 --> 00:23:24,390
So, we had e g up here as an
abbreviation for these sets of

311
00:23:24,390 --> 00:23:27,800
orbitals, and now that's
just referred to as e.

312
00:23:27,800 --> 00:23:32,140
Notice the book in one place has
an e 2, but uses e in all

313
00:23:32,140 --> 00:23:35,136
the other places, so just
use e, the e 2 was a

314
00:23:35,136 --> 00:23:36,440
mistake in the book.

315
00:23:36,440 --> 00:23:42,250
And then we have t 2 g
becomes t 2 up here.

316
00:23:42,250 --> 00:23:45,400
So we have this slightly
different nomenclature and we

317
00:23:45,400 --> 00:23:49,320
have this flip in direction.

318
00:23:49,320 --> 00:23:53,860
So, the other thing that is
important to emphasize is that

319
00:23:53,860 --> 00:23:57,520
the tetrahedral splitting energy
is smaller, because

320
00:23:57,520 --> 00:24:00,400
none of those ligands are
pointing directly toward any

321
00:24:00,400 --> 00:24:01,610
of the d orbitals.

322
00:24:01,610 --> 00:24:05,930
So here there is a much larger
difference, here there is a

323
00:24:05,930 --> 00:24:09,310
smaller difference, so that's
why it's written much closer

324
00:24:09,310 --> 00:24:14,300
together, so that's smaller.

325
00:24:14,300 --> 00:24:19,920
And because of that, many
tetrahedral complexes are high

326
00:24:19,920 --> 00:24:21,620
spin, and in this course,
you can assume that

327
00:24:21,620 --> 00:24:23,030
they're all high spin.

328
00:24:23,030 --> 00:24:25,400
So that means there's a weak
field, there's not a big

329
00:24:25,400 --> 00:24:31,540
energy difference between
those orbital sets.

330
00:24:31,540 --> 00:24:35,500
And again, we're going to --
since we're going to consider

331
00:24:35,500 --> 00:24:39,280
how much they go up and down in
energy, the overall energy

332
00:24:39,280 --> 00:24:40,480
is maintained.

333
00:24:40,480 --> 00:24:45,040
So here we had two orbitals
going up by 3/5, three

334
00:24:45,040 --> 00:24:47,770
orbitals going down by 2/5.

335
00:24:47,770 --> 00:24:50,600
So here, we have three orbitals
going up, so they'll

336
00:24:50,600 --> 00:24:54,490
go up in energy by 2/5, two
orbitals go down, so they'll

337
00:24:54,490 --> 00:24:57,580
be going down in
energy by 3/5.

338
00:24:57,580 --> 00:25:01,460
So again, it's the opposite
of the octahedral system.

339
00:25:01,460 --> 00:25:03,850
It's opposite pretty much in
every way except that the

340
00:25:03,850 --> 00:25:06,970
splitting energy is much
smaller, it's not as large for

341
00:25:06,970 --> 00:25:11,450
the tetrahedral complex.

342
00:25:11,450 --> 00:25:15,680
All right, so let's look at an
example, and we're going to

343
00:25:15,680 --> 00:25:20,190
consider a chromium, and like
we did before, we have to

344
00:25:20,190 --> 00:25:26,030
first figure out the d count,
so we have chromium plus 3.

345
00:25:26,030 --> 00:25:32,570
So what is our d count here?

346
00:25:32,570 --> 00:25:36,610
You know where chromium is, what
its group number -- here

347
00:25:36,610 --> 00:25:42,720
is a periodic table.

348
00:25:42,720 --> 00:25:45,420
So what is the d count?

349
00:25:45,420 --> 00:25:46,560
3.

350
00:25:46,560 --> 00:25:53,090
So we have 6 minus 3,
3 -- a d 3 system.

351
00:25:53,090 --> 00:25:58,490
And now, why don't you tell me
how you would fill in those

352
00:25:58,490 --> 00:26:02,880
three electrons in a
tetrahedral case.

353
00:26:02,880 --> 00:26:56,340
Have a clicker question there.

354
00:26:56,340 --> 00:27:00,040
So, notice that in addition to
having electron configurations

355
00:27:00,040 --> 00:27:02,140
that are different, the d
orbitals are labelled

356
00:27:02,140 --> 00:27:29,130
differently.

357
00:27:29,130 --> 00:27:44,020
OK, 10 more seconds.

358
00:27:44,020 --> 00:27:47,410
OK, very good, 80%.

359
00:27:47,410 --> 00:27:49,720
So, let's take a look at that.

360
00:27:49,720 --> 00:27:53,230
So down here, we're going to
have then our d x squared

361
00:27:53,230 --> 00:27:58,100
minus y squared, d z squared
orbitals up in the top, we

362
00:27:58,100 --> 00:28:05,420
have x y and x z and y z.

363
00:28:05,420 --> 00:28:10,320
Again, the orbitals that are
on-axis are repelled a little

364
00:28:10,320 --> 00:28:13,040
less than the orbitals
that are off-axis in

365
00:28:13,040 --> 00:28:14,690
a tetrahedral case.

366
00:28:14,690 --> 00:28:18,590
And then we put in our
electrons, we start down here.

367
00:28:18,590 --> 00:28:21,520
And then one of the questions
is do we keep down here and

368
00:28:21,520 --> 00:28:26,240
pair up or go up here, and
the answer is that

369
00:28:26,240 --> 00:28:27,670
you would go up here.

370
00:28:27,670 --> 00:28:31,330
Does someone want to tell me
why they think that's true?

371
00:28:31,330 --> 00:28:31,550
Yeah.

372
00:28:31,550 --> 00:28:33,930
STUDENT: [INAUDIBLE]

373
00:28:33,930 --> 00:28:34,420
PROFESSOR: Right,
because it has a

374
00:28:34,420 --> 00:28:36,100
smaller splitting energy.

375
00:28:36,100 --> 00:28:38,530
So, the way that we were
deciding before with the weak

376
00:28:38,530 --> 00:28:41,500
field and the strong field, if
it's a weak field, it doesn't

377
00:28:41,500 --> 00:28:43,270
take much energy to
put it up there.

378
00:28:43,270 --> 00:28:45,780
So you go they don't want to
be paired, there's energy

379
00:28:45,780 --> 00:28:47,370
associated with pairing.

380
00:28:47,370 --> 00:28:50,990
But if there's a really huge
splitting energy, then it

381
00:28:50,990 --> 00:28:54,140
takes less energy to pair them
up before you go that big

382
00:28:54,140 --> 00:28:55,560
distance up there.

383
00:28:55,560 --> 00:28:58,570
But in tetrahedral cases, the
splitting energy's always

384
00:28:58,570 --> 00:29:02,690
small, so you're just going to
always fill them up singly to

385
00:29:02,690 --> 00:29:05,850
the fullest extent possible
before you pair.

386
00:29:05,850 --> 00:29:08,670
So this is like a weak field
case for the octahedral

387
00:29:08,670 --> 00:29:11,690
system, and all tetrahedral
complexes are sort of the

388
00:29:11,690 --> 00:29:14,430
equivalent of the weak field,
because the splitting energy

389
00:29:14,430 --> 00:29:17,640
is always small in an octahedral
case, because none

390
00:29:17,640 --> 00:29:20,570
of the ligands' negative point
charges are really pointing

391
00:29:20,570 --> 00:29:24,260
toward any of those orbitals
that much, so it's not that

392
00:29:24,260 --> 00:29:25,730
big a difference.

393
00:29:25,730 --> 00:29:30,300
So, here we have this and now we
can practice writing our d

394
00:29:30,300 --> 00:29:33,760
to the n electron
configuration.

395
00:29:33,760 --> 00:29:38,420
So what do I put here?

396
00:29:38,420 --> 00:29:42,280
What do I put first?

397
00:29:42,280 --> 00:29:46,460
So we put the e and then what?

398
00:29:46,460 --> 00:29:47,630
Yup.

399
00:29:47,630 --> 00:29:51,630
There are two electrons in the
e set of orbitals, and in the

400
00:29:51,630 --> 00:29:55,280
t 2 orbitals, there's one.

401
00:29:55,280 --> 00:29:59,040
So that is our d n electron
configuration.

402
00:29:59,040 --> 00:30:03,010
And then we're also asked how
many unpaired electrons.

403
00:30:03,010 --> 00:30:16,160
Unpaired electrons and
that is three.

404
00:30:16,160 --> 00:30:16,690
All right.

405
00:30:16,690 --> 00:30:21,680
So that's not too bad, that's
the tetrahedral case.

406
00:30:21,680 --> 00:30:23,350
The hardest part is
probably making

407
00:30:23,350 --> 00:30:27,710
your tetrahedral complex.

408
00:30:27,710 --> 00:30:31,350
Now square planar.

409
00:30:31,350 --> 00:30:34,430
So again, with the square
planar set you have your

410
00:30:34,430 --> 00:30:38,830
square planar model -- we have
a bigger one down here.

411
00:30:38,830 --> 00:30:43,260
And the axes is defined such
that we have ligands right

412
00:30:43,260 --> 00:30:46,780
along x -- one coming out at
you and one going back, and

413
00:30:46,780 --> 00:30:50,060
also ligands right
along the y-axis.

414
00:30:50,060 --> 00:30:53,470
So as defined then, we've gotten
rid of our ligands

415
00:30:53,470 --> 00:30:56,150
along the z-axis.

416
00:30:56,150 --> 00:30:57,740
So, what do you predict?

417
00:30:57,740 --> 00:31:04,320
Which two of these will be the
most destabilized now?

418
00:31:04,320 --> 00:31:05,650
What would be the most

419
00:31:05,650 --> 00:31:09,160
destabilized, what do you guess?

420
00:31:09,160 --> 00:31:13,300
You can hold up your
little sets here.

421
00:31:13,300 --> 00:31:16,140
What's the most destabilized,
what's going to go up the most

422
00:31:16,140 --> 00:31:19,740
in energy here?

423
00:31:19,740 --> 00:31:22,790
Yeah, d z squared
minus y squared.

424
00:31:22,790 --> 00:31:26,670
What do you predict might be
next, in terms of most

425
00:31:26,670 --> 00:31:29,110
unfavorable?

426
00:31:29,110 --> 00:31:30,990
Yeah, the x y one.

427
00:31:30,990 --> 00:31:35,380
So these two now are going to be
the most destabilized, with

428
00:31:35,380 --> 00:31:39,020
d x squared minus y squared
being a lot more destabilized

429
00:31:39,020 --> 00:31:42,260
than just the x y, because
again, those d orbitals are

430
00:31:42,260 --> 00:31:47,340
on-axis and these ligands
are on-axis.

431
00:31:47,340 --> 00:31:51,570
So, let's take a look at
all of these again.

432
00:31:51,570 --> 00:31:55,220
So in the octahedral case,
these were degenerate.

433
00:31:55,220 --> 00:31:59,190
That's no longer true, because
there are no ligands along the

434
00:31:59,190 --> 00:32:00,450
z-axis anymore.

435
00:32:00,450 --> 00:32:03,040
So we took those off in going
from the octahedral to the

436
00:32:03,040 --> 00:32:07,030
square planar, so you have much
less repulsion, but with

437
00:32:07,030 --> 00:32:11,010
the d x squared minus y squared,
you still have a lot

438
00:32:11,010 --> 00:32:12,620
repulsion.

439
00:32:12,620 --> 00:32:16,810
so then if we start building up
our case, and this diagram

440
00:32:16,810 --> 00:32:19,025
is, I think, on the next page of
your handout, but I'm going

441
00:32:19,025 --> 00:32:21,830
to start building it
all up together.

442
00:32:21,830 --> 00:32:26,300
So now d x squared, y squared
is really high up, it's very

443
00:32:26,300 --> 00:32:29,390
much more destabilized
than anybody else.

444
00:32:29,390 --> 00:32:32,280
D z squared, on the other
hand, is down.

445
00:32:32,280 --> 00:32:35,870
It's not -- it would be
stabilized compared -- it's

446
00:32:35,870 --> 00:32:40,560
not nearly as destabilized
as the other system.

447
00:32:40,560 --> 00:32:44,070
So then we go back and
look at these.

448
00:32:44,070 --> 00:32:49,820
You told me that d x y would
probably be next, and that's a

449
00:32:49,820 --> 00:32:50,730
very good guess.

450
00:32:50,730 --> 00:32:52,890
You see you have more repulsion
than in the other

451
00:32:52,890 --> 00:32:55,030
two, because the other
orbitals have some z

452
00:32:55,030 --> 00:32:56,450
component in them.

453
00:32:56,450 --> 00:33:00,100
So you have less repulsion
than d x squared minus y

454
00:33:00,100 --> 00:33:03,400
squared, because it's 45 degrees
off, but still that

455
00:33:03,400 --> 00:33:07,100
one is probably going to be up
a little bit more in energy

456
00:33:07,100 --> 00:33:08,830
than the other set.

457
00:33:08,830 --> 00:33:13,380
These two here are stabilized
compared to the others, so

458
00:33:13,380 --> 00:33:14,830
they're somewhere down here.

459
00:33:14,830 --> 00:33:18,950
Now the exact sort of
arrangement can vary a little

460
00:33:18,950 --> 00:33:22,840
bit, but the important points
are that the d x squared minus

461
00:33:22,840 --> 00:33:26,550
y squared is the most
destabilized, d x y would be

462
00:33:26,550 --> 00:33:31,120
next, and the other are
much lower in energy.

463
00:33:31,120 --> 00:33:34,250
And we're not going to do this
how much up and down thing,

464
00:33:34,250 --> 00:33:39,150
like the 3/5 and the 2/5 because
it's more complicated

465
00:33:39,150 --> 00:33:40,190
in this case.

466
00:33:40,190 --> 00:33:43,700
So just the basic rationale you
need to know here, not the

467
00:33:43,700 --> 00:33:52,520
exact energy differences in
this particular case.

468
00:33:52,520 --> 00:33:58,910
OK, so now we've thought about
three different kinds of

469
00:33:58,910 --> 00:34:00,910
geometries -- octahedral,
tetrahedral,

470
00:34:00,910 --> 00:34:02,450
and the square planar.

471
00:34:02,450 --> 00:34:07,910
You should be able to
rationalize, for any geometry

472
00:34:07,910 --> 00:34:10,310
that I give you, what
would be true.

473
00:34:10,310 --> 00:34:14,080
If I tell you the geometry and
how it compares with our

474
00:34:14,080 --> 00:34:18,800
frame, with our axis frame of
where the z-axis is, you

475
00:34:18,800 --> 00:34:21,660
should be able to tell me which
orbital sets would be

476
00:34:21,660 --> 00:34:24,140
the most destabilized.

477
00:34:24,140 --> 00:34:28,260
And to give you practice,
why don't you try

478
00:34:28,260 --> 00:34:29,660
this one right here.

479
00:34:29,660 --> 00:34:35,210
So we have a square pyramidal
case as drawn here with the

480
00:34:35,210 --> 00:34:40,440
axes labeled z, y and x, coming
in and coming out.

481
00:34:40,440 --> 00:34:46,940
Tell me which of the following
statements are true.

482
00:34:46,940 --> 00:34:51,760
And if you want, you can take
your square planar and turn it

483
00:34:51,760 --> 00:35:54,560
into the geometry
to help you out.

484
00:35:54,560 --> 00:36:10,150
Let's just take 10
more seconds.

485
00:36:10,150 --> 00:36:11,030
All right.

486
00:36:11,030 --> 00:36:13,510
That was good.

487
00:36:13,510 --> 00:36:15,590
People did well on
that question.

488
00:36:15,590 --> 00:36:25,180
So, if we consider that we had
the top two are correct.

489
00:36:25,180 --> 00:36:29,630
So, if we consider the d z
squared, now we've put a

490
00:36:29,630 --> 00:36:33,710
ligand along z, so that is going
to cause that to be more

491
00:36:33,710 --> 00:36:37,450
destabilized for this geometry
rather than square planar,

492
00:36:37,450 --> 00:36:42,250
which doesn't have anything in
the z direction. ah And then

493
00:36:42,250 --> 00:36:47,540
in terms, also, other orbitals
that have a component along z

494
00:36:47,540 --> 00:36:52,030
are going to be affected a
little bit by that, but our

495
00:36:52,030 --> 00:36:56,370
other one here is not going to
be true, so we just have all

496
00:36:56,370 --> 00:36:58,930
of the above is not correct,
so we have this one.

497
00:36:58,930 --> 00:37:02,730
So if we had up those, that's
actually a pretty good score.

498
00:37:02,730 --> 00:37:07,250
And so you could think about,
say, what would be true of a

499
00:37:07,250 --> 00:37:11,190
complex that was linear along
z, what would be the most

500
00:37:11,190 --> 00:37:13,320
stabilized, for example.

501
00:37:13,320 --> 00:37:16,540
So these are the kinds of
questions you can get, and I

502
00:37:16,540 --> 00:37:20,360
think there are a few
on the problem-set.

503
00:37:20,360 --> 00:37:24,850
All right, so let's come back
together now and talk about

504
00:37:24,850 --> 00:37:26,440
magnetism again.

505
00:37:26,440 --> 00:37:30,760
So, we said in the beginning
that magnetism can be used to

506
00:37:30,760 --> 00:37:35,090
figure out geometry in, say, a
metal cluster in an enzyme,

507
00:37:35,090 --> 00:37:39,180
and let's give an example of
how that could be true.

508
00:37:39,180 --> 00:37:44,050
So, suppose you have a nickel
plus 2 system, so that would

509
00:37:44,050 --> 00:37:49,150
be a d 8 system, so we have
group 10 minus 2 or d 8, and

510
00:37:49,150 --> 00:37:51,490
it was found to be
diamagnetic.

511
00:37:51,490 --> 00:37:56,210
And from that, we may be able to
guess, using these kinds of

512
00:37:56,210 --> 00:37:59,790
diagrams, whether it has
square planar geometry,

513
00:37:59,790 --> 00:38:03,410
tetrahedral geometry, or
octahedral geometry.

514
00:38:03,410 --> 00:38:08,690
We can predict the geometry
based on that information.

515
00:38:08,690 --> 00:38:11,690
Let's think about
how that's true.

516
00:38:11,690 --> 00:38:14,460
We have a d 8 system.

517
00:38:14,460 --> 00:38:17,510
Think about octahedral
for a minute.

518
00:38:17,510 --> 00:38:24,230
Are there two options for how
this might look in this case?

519
00:38:24,230 --> 00:38:26,360
Is there going to be a
difference in electron

520
00:38:26,360 --> 00:38:32,880
configurations if it's a weak
field or a strong field?

521
00:38:32,880 --> 00:38:36,790
So, write it out on your handout
and tell me whether it

522
00:38:36,790 --> 00:38:54,030
would be true, think
about it both ways.

523
00:38:54,030 --> 00:38:58,280
Is there a difference?

524
00:38:58,280 --> 00:39:00,650
So, you would end up getting
the same thing in this

525
00:39:00,650 --> 00:39:01,910
particular case.

526
00:39:01,910 --> 00:39:05,370
So if it's a weak field and you
put in 1, 2, 3, then jump

527
00:39:05,370 --> 00:39:09,810
up here, 4, 5, and then you have
to come back, 6, 7, 8.

528
00:39:09,810 --> 00:39:13,350
Or you could pair up all the
ones on the bottom first and

529
00:39:13,350 --> 00:39:16,550
then go up there, but you
actually get the same result

530
00:39:16,550 --> 00:39:19,430
no matter which way you
put them in, the

531
00:39:19,430 --> 00:39:21,430
diagram looks the same.

532
00:39:21,430 --> 00:39:24,190
So it doesn't matter in this
case if it is a weak or strong

533
00:39:24,190 --> 00:39:27,560
field, you end up with those
number of electrons with the

534
00:39:27,560 --> 00:39:31,870
exact same configuration.

535
00:39:31,870 --> 00:39:33,690
So, we know what that
looks like.

536
00:39:33,690 --> 00:39:36,050
Well, what about
square planar.

537
00:39:36,050 --> 00:39:38,860
So let's put our electrons
in there.

538
00:39:38,860 --> 00:39:41,590
We'll start at the bottom,
we'll just put them in.

539
00:39:41,590 --> 00:39:44,090
I'm not going to worry too much
about whether we can jump

540
00:39:44,090 --> 00:39:47,820
up or not, we'll just go and
pair them up as we go down

541
00:39:47,820 --> 00:39:51,140
here, and then go up here,
and now we've put

542
00:39:51,140 --> 00:39:52,560
in our eight electrons.

543
00:39:52,560 --> 00:39:56,730
So, how close these are, we're
just going to put them all in.

544
00:39:56,730 --> 00:39:59,540
We're just going to be very
careful not to bump up any

545
00:39:59,540 --> 00:40:04,540
electrons there unless we
absolutely have to, because d

546
00:40:04,540 --> 00:40:08,185
x squared minus y squared is
very much more destabilized in

547
00:40:08,185 --> 00:40:10,850
the square planar system, so
we're going to want to pair

548
00:40:10,850 --> 00:40:15,660
all our electrons up in those
lower energy orbitals.

549
00:40:15,660 --> 00:40:18,910
So even if we sort of did it
a different way, that's

550
00:40:18,910 --> 00:40:19,990
what we would get.

551
00:40:19,990 --> 00:40:22,990
So we're going to want to pair
everything up before we go up

552
00:40:22,990 --> 00:40:25,220
to that top one there.

553
00:40:25,220 --> 00:40:26,460
So there's our square planar.

554
00:40:26,460 --> 00:40:28,040
Well, what about tetrahedral.

555
00:40:28,040 --> 00:40:31,680
How are we going to
fill these up?

556
00:40:31,680 --> 00:40:37,070
Do we want to pair first, or we
do want to put them to the

557
00:40:37,070 --> 00:40:40,290
full extent possible singly?

558
00:40:40,290 --> 00:40:42,820
Single, right, it's going to be
a weak field, there's not a

559
00:40:42,820 --> 00:40:45,900
big splitting here between
these, so we'll put them in,

560
00:40:45,900 --> 00:40:53,050
there's 1, 2, 3,
4, 5, 6, 7, 8.

561
00:40:53,050 --> 00:40:55,420
All right, so now we can
consider which of these will

562
00:40:55,420 --> 00:40:58,120
be paramagnetic and which
will be diamagnetic.

563
00:40:58,120 --> 00:41:01,960
What's octahedral?

564
00:41:01,960 --> 00:41:05,000
It's paramagnetic, we have
unpaired electrons.

565
00:41:05,000 --> 00:41:08,350
What about square planar?

566
00:41:08,350 --> 00:41:10,350
Square planar's diamagnetic.

567
00:41:10,350 --> 00:41:11,930
And what about tetrahedral?

568
00:41:11,930 --> 00:41:14,610
Paramagnetic.

569
00:41:14,610 --> 00:41:20,180
So, if the experimental data
told us that a nickel center

570
00:41:20,180 --> 00:41:23,600
in an enzyme was diamagnetic,
and we were trying to decide

571
00:41:23,600 --> 00:41:26,720
between those three geometries,
it really seems

572
00:41:26,720 --> 00:41:31,400
like square planar is going
to be our best guess.

573
00:41:31,400 --> 00:41:34,820
And so, let me show you
an example of a

574
00:41:34,820 --> 00:41:39,040
square planar system.

575
00:41:39,040 --> 00:41:44,910
And so this particular nickel is
in a square planar system.

576
00:41:44,910 --> 00:41:50,340
It has four ligands that are all
in the same plane, and it

577
00:41:50,340 --> 00:41:53,380
is a square planar center
for a nickel,

578
00:41:53,380 --> 00:41:54,770
so that's one example.

579
00:41:54,770 --> 00:41:57,510
And this is a cluster
that's involved in

580
00:41:57,510 --> 00:42:01,280
life on carbon dioxide.

581
00:42:01,280 --> 00:42:04,480
All right, so that's different
geometries,

582
00:42:04,480 --> 00:42:05,750
you're set with that.

583
00:42:05,750 --> 00:42:09,230
Monday we're going to talk about
colors of coordination

584
00:42:09,230 --> 00:42:11,660
complexes, which all have
to do with the different

585
00:42:11,660 --> 00:42:15,140
geometries, paired and unpaired
electrons, high

586
00:42:15,140 --> 00:42:19,300
field, low spin, strong
field, weak field.

587
00:42:19,300 --> 00:42:21,020
Have a nice weekend.