MOT : complicated bonding analyses

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MOT complicated bonding analyses
BF3 B 2s 2px 2py 2pz F 2s 2px 2py 2pz
?????????????? BF3 ??????????????????
interactions ??????? 4 aos ??? B ??? 12 LGOs ???
D3h F3 fragment LGOs ???? 12 ????????? LGO(1)
???????????????
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Ligand group Boron atomic orbital
Comment orbital
On symmetry grounds, each LGO may be matched
to an atomic orbital of the boron atom, but the
net interaction is a non-bonding one.
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??????????????????? LGOs ?????????????? aos ???
B ????? B ??????????? ??????????????????
????????????????? MO diagram ????????? symmetry
matching ?????????????????????????????????????????
??????? - ??????????????????????????????????
basis set - lobe ???????????? (spatial
properties) ???? LGO(1) ??? LGO(4) ??????????
interact ??? B 2s ??? net overlap integral
?????????????? - MO ?? BF3 ?????????????? LGO
????????????????????? ????????????????????????????
?? LGO(1) ??? LGO(4)
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????????????? ?????????????????????????????? BF3
?????????? MO ????? bonding character ???????
interactions ??????? - LGO(1) ??? B 2s ao gt y1
(LGO(4) ??????????????????????) - LGO(2) ??? B
2py ao gt y2 (y2 also contains LGO(11)
character) - LGO(3) ??? B 2px ao gt y3 (y3 also
contains LGO(12) character) - LGO(5) ??? B 2pz ao
gt y4 (B-F p-bonding character)
??????????????????????????????????????? LGO(4),
LGO(11)??? LGO(12), ???? interact ??? B 2s, 2py
??? 2pz ????????????????????????? MOs ?????????
LGO(1), LGO(2) ??? LGO(3), ????????
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???? LGO(6), LGO(7), LGO(8), LGO(9) ???
LGO(10) ???? non-bonding MOs ????????????????
overlap ??????? LGO(6)B 2py ??? LGO(7)B
2px ????????? (???? ? ??? interactions allowed)
y1 , y2 ??? y3 MOs ??????????? B-F s-bonding
orbital ???????????? delocalized ?????? 3 B-F
interactions ???? y4 ?? B-F p-bonding character
delocalized ?????? 4 ????? ?????? p-bond order
per B-F bond 1/3 ?????????????????????????? p
??????? (partial p-character) ??????? B-F bond
????????????????????????? BF3 131 pm
?????????????????? rcov(B) rcov(F) 159 pm
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????????????????????? MO ?????????????????????????
??????????????????????????????????????? ?
?????????????????????????
?????? MOT ?????????????????????? (learning to
use the theory objectively)
?????????????????????????????????????????
MO model ???????????????????????????????????????
? ?????????????? MO diagram ???????
(?????????????) ?????????? ???????????????????????
????????????? bonding features ????????
?????????????????????????? partial MO treatments
??????????????????????????????????????????????????
??????????????????????????????????????????????
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CO2
???????????????????????????? sp hybrid
orbitals ??????? 2p orbitals ???????????
2 localized CO p-bonds ?????? z ???????????????
p-bond ????????????? overlap ??? C 2px ??? O
2px ??? p-bond ??????????????? overlap ??? C
2py ??? O 2py
?????? 4.3
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MOT ????????????? p-bonds ?? CO2
?????????? ??? LGO approach ??????? interaction
??????? aos ??? C ??? LGOs ??? O---O fragment
(????? O ???????????????? z) ?????????????????????
?? p-system ????????? interactions
???????????????? 2px ??? 2py aos ???????? ???????
partial MO diagram
?????? 4.21
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LGO ??????? O---O fragment ???????????????
in-plane??? out-of-plane ??? O 2px ????? LGO(1)
??????????????????????????????? overlap ??? C 2px
??? gt MOs y1 p-bonding ??? y3
p-antibonding MO ???? LGO(2) ???? non-bonding
?????????? 4 valence electrons ??????? MOs y1 ???
y2 (????? electrons ??????????????????? valence
electrons ?? CO s-bonding MOs
???????????????????) ????????? overlap ??? 2py
????????????? p-interaction ??????????????????????
???????????????
?????????? MO treatment ???????? 2 orthogonal
p-bonding interactions ?? CO2 ???? delocalized
?????? O-C-O ????? electrons 2 ???????????????????
interactions ???????? ??????? net p -bond order
per C-O interaction 1
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XeF2
XeF2 ???? linear molecule ?????? valence
bond approach ??????????????????????? localized
picture ?????? 2 Xe-F bonds ??? 2c-2c
????????????????????????????????? MO
????????????????????? (different interpretation)
??????????????????????? XeF2
F 2s, 2px, 2py, 2pz Xe 5s, 2px, 2py, 2pz
??????????????????????????????????????????
????????? s-bonding interactions ??????????? z
?????????????????????????????? ????? LGOs ???
F--F fragment ?????? 2s ??? 2pz??????
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?????? 4.22
???????????????? LGOs ????? F 2p character
??????????????? Xe 5s ??? 5p ??? LGOs ????? F 2s
character ???????????????????????????? interact
?????????????????? aos ??? Xe ?????????????
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LGO(1) ??? LGO(2) ???? non-bonding MOs ????????
valence electrons ??????? (4 ????????? Xe ??? 3
?????? ??? F) ??????? MOs ??????? 2 bonding MOs
??? 1 antibonding MO ???????? ??????? net bond
order per Xe-F 1/2 ????????? net bonding
character ??????? 1 MO ?????????????? bonding
interact ??? three-centre two- electron (3c-2e)
In a 3c-2e bonding interaction, two electrons
occupy a bonding MO which is delocalized over
three atomic centres
??????? ??????????????????????? p-type
interaction ??? bonding model ??? XeF2 Xe 5px ???
5py ??? interact ??? LGOs ??? F..F fragment
??????????????? F 2px ??? 2py ??????? doubly
degenerate set ??? p-bonding MOs, degenerate set
??? p-type non-bonding Mos
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(centred on F atoms) ??? degenerate set ???
p-MOs ??? ???????????????????? CO2 ????
XeF2 ????? valence electrons ?????????????????
p-type MOs ?????????? ???????? net p-bonding ??
XeF2
NO3-
????????????????????? VB approach 3
resonance structures ?????????????? ???????????
N-O (1 ?? 3 ?????????)
?????? 4.4
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??????? net bond order per N-O bond 1.33
??????? N-O p-system ????????? delocalized
interactions ?????? MOT
?????? 4.23
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??????? axis set ???? NO3- (D3h) ??????????????
xy ????????????????????? p-interaction ?? NO3-
????????? interaction ??????? N2pz ??? LGOs 3
orbitals ??????????????????????? 2pz ??? O 3
????? ???????????? F3 fragment ?? BF3 (????
LGO(5), LGO(8) ??? LGO(9) ??? BF3) partial MO
diagram ??????????? p-type orbitals ????????
interaction ??????? N 2pz ??? LGO(1) ?????
p-bonding MO ??? p MO ???? LGO(2) ??? LGO(3) ????
non-bonding MOs ????? electrons ???? 6 ???????? 3
MOs ???????????????????????? (?????????? 24
valence electrons ?? NO3- ??? 6 ?????????????
s-bonding MOs ??? 12 ????????????? non-bonding
MOs ?????????? O-centred LGOs ???????? 6
???????????? p-type MOs)
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MOT ????????????????????? NO3- ??????????? 1
p-type MO ????? electron ????????? ???
delocalized ?????? 4 ????? ????? N-O p-bond order
????? 1/3 ??????????????? VBT
???????????????????????????????????????
delocalized ???????????????????? resonance
??????? 3 ????????? ?????????????? isoelectronic
species CO32- ??? BO33- (D3h ???????)
??????????????????????????
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SF6
VB model ??? octahedral SF6
???????????????????????? six equivalent S-F bonds
?????? sp3d2 hybridization ??? valence electrons
????????? S ?????????????????????????????????????
3d orbital ???????????????????????????? 3d
??????????????????????????????????????????????????
???????????????????????? 3s ??? 3p
???????????????? MOT ?????????????????????????????
???????????????? 3d orbital ????????? S-F bonds
????????? 3s ??? 3p ??? S ???? SF6 ???????
hypervalence molecule
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?????? 4.5
??????????????? partial MO diagram ???????????
3s ??? 3p orbitals ???? basis set ???????? S
???????????????????????????????? F ????????? x, y
??? z ??????? LGOs ???????? F6 fragment ??????
2s, 2px, 2py ??? 2pz ?????????? LGOs ?????
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????????? F 2s ?????????????????????????????
interact ??? aos ??? S ??? ?????????????????????
LGOs ?????????????? F 2p ??? 2p 18 ????????? (3
?????????????????????? F) ??????????? LGOs ??? 18
????????? ??????????????? 4 LGOs ???????
s-interactions ??? 3s ??? 3p ??? S ?????????
???????? 14 LGOs ???? non-bonding MOs partial MO
diagram ?????? SF6 ??????
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?????????????????? ?????????? interactions
??????? 3s ??? LGO(1) 3pz ??? LGO(2) 3py ???
LGO(3) ??? 3px ??? LGO(4) ??? 4 bonding MOs
??????????? 1 unique MO ??? triply degenerate set
??? MOs ??????? 4 antibonding MOs ???????????
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??? SF6 ?? valence electrons ??????? 48 ??????
(6 ????????? S ??? 7 ????????? F)
?????????????????????????????? MOs ??????????????
F 2s ??????????????????????????????????????
???????????? MOs y1-y4 ?????????????? s MOs
??????????????? valence electrons
????????????????? F-centred non-bonding MOs
???????????????? partial MO diagram ??? ??? (a)
???????????????????? basis set ?????????? 3s ???
3p ??? S ????? 4 bonding MOs ??? y1 MO ?? bonding
character delocalized ?????? 6 interactions
????y2 y3 ??? y4 ????? MO ????? bonding character
delocalized ?????? 2 S-F bonds ???????????????
set ????? y2 y3 ??? y4 ???????? 6
????????????????????????? ????????????????????????
?? S-F bonds ????????????????????? bond order
????????????? 2/3 (4 ?????? electrons ?????? 6
S-F bonding interactions)
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?????????? basis set ??? S ?????? 3d ???? ??? 14
LGOs ??? F6 fragment ?????????????????? bonding
model????? 2 LGOs (LGO(5) ??? LGO(6))
???????????????????????????? 2 orbitals??? 3d
(3dz2 ??? 3dx2-y2) ?????????? interaction ???????
dz2 ??? LGO(5) ?????????? 3dx2-y2 ??? LGO(6) ???
MO diagram ????? ? ?????? (b) ?????? (a) ????????
interaction ??????? S 3s ??? 3p aos ???
LGO(1)-LGO(4) ???? interactions ???????? 2
bonding ??? 2 antibonding MOs ???? 3d
????????????????? 3 ???? ????? (dxy dyz dzx)
???? non-bonding MOs ?????????????????? valence
electrons ????????????????? bonding MOs
???????????? (b) ?? electrons ?????????
??????????????????? 3d ???????????????????????????
??????????????? S-F bond order ????? 1
??????????? 6 bonding MOs ????? bonding character
delocalized ?????? 6 S-F bonds
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?????????????????????? MOT ??? SF6
?????????????????????? basis set ????? 3d
????????? 3d ????? ???????????????????? real
bonding picture ?????????????? ???????????????????
????????????????? ? ????
B2H6
??????????????????????????????????????
????????? B ?????????????????????????? 3 ?????
???????????? H ?????????????? ????????????????????
?????????????????????????????? VBT ????????????
B2H6 (D2h) ?????? ????????????????????????????????
??
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?????? 4.26
- ?????????? H ??????????? B 2 ????? ????????
valence electron ????? 1 ?????????????? -
?????????? B ?????????????? H 4 ?????????????
valence electron ????? 3 ??????
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- ???????????? B-H ??????????????????????
????????? B-H bonding interactions 2 ????
B2H6 ????????????? electron deficient
????????????? dimer ??? BH3 ????? 12 valence
electrons ???????????? B-H-B ?????????? ???
terminal B-H interaction ???? localized 2c-2e bond
?????? 4.6
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???????? bridging unit ???? 3c-2e interaction
????????????????? 3c-2c interaction
?????????????????? 2c-2e bond ????????????????????
?????????????????????????? ?????????????????????
B2H6 ???????? sp3 ???? sp2 hybridized B centre
????????????????????????????????
?????? 4.27
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?????? 4.28
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