Atoms-in-molecules analysis of extended hypervalent five-center, six-electron (5c-6e) C2Z2O interactions at the 1,8,9-positions of anthraquinone and 9-methoxyanthracene systems

Article abstract of DOI:10.1002/chem.200600471

To clarify the nature of five-center, six-electron (5c-6e) C ₂Z₂O interactions, atoms-in-molecules (AIM) analysis has been applied to an anthraquinone, 1,8-(MeZ)₂ATQ (1 (Z = Se), 2 (Z = S), and 3 (Z = O)), and a 9-methoxyanthracene system, 9-MeO-1,8-(MeZ) ₂ATC (4 (Z = Se), 5 (Z = S), and 6 (Z = O)), as well as 1-(MeZ)ATQ (7 (Z = Se), 8 (Z = S), and 9 (Z = O)) and 9-MeO-1-(MeZ)ATC (10 (Z = Se), 11 (Z = S), and 12 (Z = O)). The total electronic energy density (H_b(r _c)) at the bond critical points (BCPs), an appropriate index for weak interactions, has been examined for 5c-6e C₂Z₂O and 3c-4e CZO interactions of the n_p(O)...σ*(Z-C) type in 1-12. Some hydrogen-bonded adducts were also re-examined for convenience of comparison. The total electronic energy densities varied in the following order: O...O (3: H_b(r_c) = 0.0028 au) = O...O (6: 0.0028 au) > O...O (9: 0.0025 au) ≥ NN...HF (0.0024 au) ≥ O...O (12: 0.0023 au) ? H₂O...HOH (0.0015 au) > S...O (8: 0.0013 au) = S...O (2: 0.0013 au) > S...O (11: 0.0012 au) = S...O (5: 0.0012 au) > HF...HF (0.0008 au) = Se...O (10: 0.0008 au) = Se...O (4: 0.0008 au) ≥ Se...O (1: 0.0007 au) ≥ Se...O (7: 0.0006 au) ? HCN...HF (-0.0013 au). H_b(r_c) values for S...O were predicted to be smaller than the hydrogen bond of H₂O...HOH and H_b(r _c) values for Se...O are very close to or slightly smaller than that for HF...HF in both the ATQ and 9-MeOATC systems. In the case of Z = Se and S, H_b(r_c) values for 5c-6e C₂Z ₂O interactions are essentially equal to those for 3c-4e CZO if Z is the same. The results demonstrate that two n_p(O) ...σ*(Z-C) 3c-4e interactions effectively connect through the central n_p(O) orbital to form the extended hypervalent 5c-6e system of the σ*(C-Z)-n_p(O)...σ* (Z-C) type for Z = Se and S in both systems. Natural bond orbital (NBO) analysis revealed that n_s(O) also contributes to some extent. The electron charge densities at the BCPs, NBO analysis, and the total energies calculated for 1-12, together with the structural changes in the PhSe derivatives, support the above discussion.

Full text of DOI:10.1002/chem.200600471

FULL PAPER
DOI: 10.1002/chem.200600471
Atoms-in-Molecules Analysis of Extended Hypervalent Five-Center, Six-
Electron (5c–6e) C2Z2O Interactions at the 1,8,9-Positions of Anthraquinone
and9-Methoxyanthracene Systems
Waro Nakanishi,*[a] Takashi Nakamoto,[a] Satoko Hayashi,[a] Takahiro Sasamori,[b] and
Norihiro Tokitoh[b]
Abstract: To clarify the nature of five-
center, six-electron (5c–6e) C2Z2O in-
teractions, atoms-in-molecules (AIM)
analysis has been applied to an anthra-
quinone, 1,8-(MeZ)2ATQ (1 (Z=Se), 2
(Z=S), and 3 (Z=O)), and a 9-me-
thoxyanthracene system, 9-MeO-1,8-
(MeZ)2ATC (4 (Z=Se), 5 (Z=S), and
6 (Z=O)), as well as 1-(MeZ)ATQ (7
(Z=Se), 8 (Z=S), and 9 (Z=O)) and
9-MeO-1-(MeZ)ATC (10 (Z=Se), 11
(Z=S), and 12 (Z=O)). The total
electronic energy density (Hb(rc)) at
the bond critical points (BCPs), an ap-
propriate index for weak interactions,
has been examined for 5c–6e C2Z2O
and 3c–4e CZO interactions of the
ꢁ
ties varied in the following order:
O···O (3: Hb(rc)=0.0028 au)=O···O (6:
0.0028 au)>O···O (9: 0.0025 au)ꢀ
close to or slightly smaller than that for
HF···HF in both the ATQ and 9-
MeOATC systems. In the case of Z=
Se and S, Hb(rc) values for 5c–6e
C2Z2O interactions are essentially
equal to those for 3c–4e CZO if Z is
the same. The results demonstrate that
ꢁ
NN···HF
(0.0024 au)ꢀO···O
(12:
0.0023au) @H2O···HOH (0.0015 au)>
S···O (8: 0.0013au) =S···O (2:
0.0013au) ꢀS···O (11: 0.0012 au)=
S···O (5: 0.0012 au)>HF···HF
(0.0008 au)=Se···O (10: 0.0008 au)=
Se···O (4: 0.0008 au)ꢀSe···O (1:
0.0007 au)ꢀSe···O (7: 0.0006 au)@
HCN···HF (ꢁ0.0013au). Hb(rc) values
for S···O were predicted to be smaller
than the hydrogen bond of H2O···HOH
and Hb(rc) values for Se···O are very
two np(O)···s*(Z C) 3c–4e interactions
effectively connect through the central
np(O) orbital to form the extended hy-
G
ꢁ
pervalent 5c–6e system of the s*
ACHTREUNG
ꢁ
Z)···np(O)···s*
ACHTREUNG
and S in both systems. Natural bond or-
bital (NBO) analysis revealed that
ns(O) also contributes to some extent.
The electron charge densities at the
BCPs, NBO analysis, and the total en-
ergies calculated for 1–12, together
with the structural changes in the PhSe
derivatives, support the above discus-
sion.
Keywords: ab initio calculations ·
np(O)···s*
(Z C) type in 1–12. Some
anthracenes
(AIM) theory
hypervalent compounds
·
atoms-in-molecules
hydrogen-bonded adducts were also re-
examined for convenience of compari-
son. The total electronic energy densi-
·
chalcogens
·
Introduction
electron bonds (3c–4e), are of current interest.[1d,5–8] Our
strategy to construct mc–ne (mꢀ4) bonds is to employ non-
bonded interactions containing lone-pair orbitals.[2–4] We
have previously reported the formation of extended hyper-
valent 4c–6e Z4 (Z=Se, S, and Br),[2,4] 5c–6e C2Z2O (Z=Se
and S),[3] 6c–8e Se2Br4, and 7c–10e Se2Br5 bonds,[4] as well as
their nature. Linear alignments of four atoms have also
been reported by others, although they are not recognized
as extended hypervalent bonds.[9] Weak interactions control
the fine structures of compounds and create highly function-
alized materials. Information on the weak interactions will
also be supplied through the elucidation of the nature of ex-
tended hypervalent mc–ne (mꢀ4) bonds.
Extended hypervalent bonds, mc–ne (mꢀ4),[1–4], which are
s-type linear bonds that are greater than three-center, four-
[a] Prof. Dr. W. Nakanishi, T. Nakamoto, Dr. S. Hayashi
Department of Materials Science and Chemistry
Faculty of Systems Engineering, Wakayama University
930 Sakaedani, Wakayama 640-8510 (Japan)
Fax : (+81)73-457-8253
E-mail: nakanisi@sys.wakayama-u.ac.jp
[b] Dr. T. Sasamori, Prof. Dr. N. Tokitoh
Institute for Chemical Research, Kyoto University
Uji, Kyoto 611-0011 (Japan)
The formation of 5c–6e C2Z2O systems was established on
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
ꢁ
ꢁ
the basis of the linear alignment of five C Z···O···Z C
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
255

atoms (Z=Se and S) in 1,8-bis(phenylselanyl)anthraquinone
(I), 9-methoxy-1,8-bis(phenylselanyl)anthracene (II), and
their derivatives. The quantum chemical (QC) calculations,
incorporating the energy-lowering effect of linear alignment,
the direction of the charge transfer (CT), and the orbital in-
teraction maps, support the formation of 5c–6e C2Z2O in I
and II. The linear alignment of the 5c–6e C2Z2O entity is a
typical example of an extended hypervalent bond.[3]
Scheme 1 shows the molecular orbital approximation of 5c–
determination of the structures by means of X-ray crystallo-
graphic analysis. Of plausible structures such as AA and BB,
compounds 1–3 adopt the BB structure, according to our
ꢁ
definition, with both Z CMe bonds lying in the ATQ plane,
similar to the cases of I and II (Scheme 2). p–p conjugation
Scheme 2. AA and BB structures in 1 and 4.
of the np(Z)–p(ATQ)–np(Z) type must play an important
N
role in stabilizing 5c–6e C2Z2O (BB). No such p–p conjuga-
tion is present in the 9-methoxyanthracene (9-MeOATC)
Scheme 1. Molecular orbital approximation of 5c–6e Z5.
system,
9-methoxy-1,8-bis(methylchalcogeno)anthracenes
6e Z5. Indeed, the simple bonding scheme enables us to vis-
ualize how molecular orbitals are constructed from the
atomic orbitals in 5c–6e Z5, but it never provides informa-
tion on the nature of the bonding. We were very interested
in the real nature of the bonding in 5c–6e C2Z2O. However,
the nature of the bonding between the oxygen and chalco-
(9-MeO-1,8-(MeZ)2ATC : 4 (Z=Se), 5 (Z=S), and 6 (Z=
O)), owing to the lack of a suitable np(O) orbital. Therefore,
the purer 5c–6e C2Z2O nature will be clarified by examining
the bonding nature in 4–6. AIM analysis was also applied to
4–6. Scheme 3shows how extended hypervalent 5c–6e
ꢁ
ꢁ
gen atoms in 5c–6e C Z···O···Z C (Z=Se and S) has not
been clarified yet.
Bader proposed a method to analyze chemical bonds, as
well as their nature, that is known as the AIM (atoms-in-
molecules) method.[10] The method can be applied to weak
bonds as well as classical chemical bonds.[11–16] Some criteria
have been proposed to enable weak interactions to be rec-
ognized, separate from the classical bonds, based on the
nature of the bond critical points (BCPs).[10]
We applied the AIM method to the extended hypervalent
5c–6e C2Z2O (Z=Se, S, and O) unit in the anthraquinone
(ATQ) system, 1,8-bis(methylchalcogeno)anthraquinones
(1,8-(MeZ)2ATQ : 1 (Z=Se), 2 (Z=S), and 3 (Z=O)) after
Scheme 3. Formation of 5c–6e X2Z2Y through the connection of two
3c–4e XZY entities through the central np(Y) orbital.
ꢁ
ꢁ
C2Z2O interactions of the s*
can be formed starting from two hypervalent 3c–4e interac-
G
G
ꢁ
tions of the np(O)···s*
through the central np(O) orbital. AIM analysis was also car-
A
ꢁ
ried out for the 3c–4e O···Z C interactions in 1-(MeZ)ATQ
(7 (Z=Se), 8 (Z=S), and 9 (Z=O)) and 9-MeO-1-
(MeZ)ATC (10 (Z=Se), 11 (Z=S), and 12 (Z=O)) for
convenience of comparison.
Herein, we report the results of the AIM analysis of 5c–
6e C2Z2O in 1–6, as well as 3c–4e CZO in 7–12, which clari-
fies the nature of the bonds. To the best of our knowledge
this is the first AIM treatment of extended hypervalent
256
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
FULL PAPER
Table 2. Selected interatomic distances [Š], angles [8], and torsional angles [8] in 1–3.
bonds. The contribution of CT
to 5c–6e C2Z2O in 1–6 and 3c–
4e CZO interactions in 7–12
has also been evaluated by
using natural bond orbital
(NBO) analysis. The results
demonstrate that the CT in 5c–
6e C2Z2O in 1–6 and 3c–4e
CZO in 7–12 controls the total
energies. The results confirm
that the energy-lowering effect
is responsible for the forma-
tion of extended hypervalent
bonds.
1
2 (S-A)
2 (S-B)
3[a]
interatomic distances
ꢁ
Z(1) O(1)
2.6356(13)
2.6344(13)
1.9100(19)
1.950(2)
1.9176(19)
1.955(2)
2.6364(11)
2.6485(11)
1.7631(14)
1.8055(15)
1.7642(14)
1.8085(15)
1.2266(17)
2.6495(11)
2.6392(11)
1.7610(14)
1.8063(15)
1.7655(14)
1.8119(15)
1.2296(17)
2.6169(15)
2.6129(15)
1.3590(16)
1.4357(17)
1.3565(16)
1.4334(17)
1.2209(17)
ꢁ
Z(2) O(1)
ꢁ
Z(1) C(1)
ꢁ
Z(1) C(15)
ꢁ
Z(2) C(11)
ꢁ
Z(2) C(16)
ꢁ
O(1) C(13)
1.233(2)
angles
Z(1)-O(1)-Z(2)
C(1)-Z(1)-C(15)
C(11)-Z(2)-C(16)
O(1)-Z(1)-C(15)
O(1)-Z(2)-C(16)
C(12)-C(13)-O(1)
C(14)-C(13)-O(1)
C(14)-C(1)-Z(1)
C(12)-C(11)-Z(2)
C(2)-C(1)-Z(1)
C(10)-C(11)-Z(2)
150.72(6)
100.19(8)
99.68(9)
158.21(4)
102.43(7)
102.83(7)
179.75(7)
176.08(6)
120.07(12)
120.10(12)
120.95(10)
121.36(10)
120.47(11)
120.86(11)
157.97(4)
102.67(7)
102.71(7)
178.49(5)
171.98(6)
120.24(12)
119.99(12)
121.06(10)
120.97(10)
120.51(11)
120.91(11)
150.15(6)
117.90(11)
118.19(11)
155.05(9)
151.15(9)
121.39(13)
120.44(12)
117.57(12)
117.83(12)
122.57(12)
122.26(12)
174.68(7)
174.33(7)
120.25(16)
119.70(16)
120.80(13)
120.43(13)
120.70(14)
120.79(14)
Results andDiscussion
Structures of 1,8-(MeZ)2ATQ
(Z=Se, S, andO: 1–3) : The
X-ray crystallographic analysis
was carried out on suitable
single crystals of 1–3, which
were obtained by slow evapo-
ration of solutions of the com-
pounds in benzene containing
10–30% v/v ethanol. Crystals
of 1 and 3 contain only one
type of structure, whereas crys-
tals of 2 contain two types of
structures (2 (S-A) and 2 (S-
torsional angles
C(15)-Z(1)-C(1)-C(14)
C(16)-Z(2)-C(11)-C(12)
O(1)-C(13)-C(14)-C(5)
O(1)-C(13)-C(12)-C(7)
C(6)-C(5)-C(14)-C(1)
C(6)-C(7)-C(12)-C(11)
C(6)-C(5)-C(14)-C(13)
C(6)-C(7)-C(12)-C(13)
175.74(15)
ꢁ178.42(15)
ꢁ177.73(17)
ꢁ176.95(17)
ꢁ179.53(16)
ꢁ179.33(16)
1.7(3)
178.72(11)
ꢁ173.14(11)
ꢁ177.62(12)
177.52(12)
179.32(12)
ꢁ179.10(12)
ꢁ0.50(19)
177.66(11)
170.27(11)
175.31(12)
176.10(12)
179.32(12)
ꢁ179.54(12)
0.69(19)
168.01(12)
177.92(12)
ꢁ159.35(14)
ꢁ161.48(14)
172.96(11)
ꢁ177.95(11)
ꢁ10.82(19)
6.44(19)
ꢁ0.1(3)
0.70(18)
0.87(19)
[a] Z(1) and Z(2) are O(3) and O(4), respectively.
B)). The crystallographic data is collected in Table 1 and se-
lected interatomic distances, angles, and torsional angles are
reported in Table 2. Figures 1, 2, and 3show the structures
of 1, 2 (S-A), and 3, respectively. The structure of 2 (S-B) is
given in the Supporting Information.
The structures of 1, 2 (S-A), and 2 (S-B) are very close to
C2v symmetry, although the oxygen atom at the 9-position
flips slightly from the ATQ plane in each molecule. The
structure of 3 is rather close to Cs symmetry, with the
oxygen atom at the 9-position flipping from the ATQ plane
and the MeO groups moving
in the opposite directions from
the plane, although the magni-
Table 1. Crystallographic data for 1–3.
1
2
3
tudes are not the same. The
structures around the Z atoms
in 1–3 are all BB by our defini-
formula
Mr
T [K]
crystal system
space group
a [Š]
C16H12O2Se2
394.18
103(2)
C16H12O2S2
300.38
103(2)
C16H12O4
268.26
103(2)
ꢁ
tion, with the Z CMe bonds in
monoclinic
P21/c (no. 14)
9.332(2)
15.862(4)
9.451(2)
107.483(3)
1334.3(6)
4
1.962
768
8865
2479 (Rint =0.0199)
2479/0/229
1.081
monoclinic
P121/n1 (no. 14)
14.171(3)
12.058(2)
16.221(3)
111.3621(19)
2581.3(9)
8
1.546
1248
22316
5021 (Rint =0.0141)
5021/0/457
1.118
monoclinic
P21/a (no. 14)
12.6272(12)
6.6216(4)
15.6593(14)
112.844(4)
1206.61(17)
4
1.477
560
8103
2352 (Rint =0.0193)
2352/0/229
1.113
the ATQ plane (Figures 1, 2,
and 3; see also Scheme 2).[3,17]
The planarity of the anthraqui-
b [Š]
c [Š]
ꢁ
nonyl group, containing the Z
b [8]
CMe bonds, is very good for 1
and 2, but the structure is
slightly bent in 3, as shown in
Figures 1, 2, and 3and by the
data in Table 2.
V [Š3]
Z
1calcd [gcmꢁ3
]
F
A
no. of reflections collected
no. of independent reflections
no. of data/restraints/params
goodness of fit, F2
The nonbonded O(1)···Se(1)
and O(1)···Se(2) distances in 1
R1, wR2
0.0177, 0.0422
0.0300, 0.0853
0.0403, 0.0990
are
2.6356(13)
and
A
A
ACHTREUNG
2.6344(13) Š,
which are 0.78–0.79 Š shorter
respectively,
ꢁ3
largest diff. peak [eŠ
]
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
257

W. Nakanishi et al.
derline for the formation of
the linear bond, but the central
px orbital at the O(1) atom will
work to form a 5c–6e system
because the deviation is
around 158 on each side of the
px orbital if the Se···Se direc-
tion is set to the x axis.
The nonbonded O···S distan-
ces in 2 (S-A) are 2.6364(11)
and 2.6485(11) Š,[19] which are
0.67–0.68 Š shorter than the
sum of the van der Waals radii
of the atoms (3.32 Š).[18] The
Figure 1. Structure of 1: a) side view and b) top view (thermal ellipsoids are shown at the 50% probability
level).
O(1A)-S(1A)-C
O(1A)-S(2A)-C
C
and
for 2 (S-A) are 179.75(7) and
176.08(6)8,
respectively,[19]
which are close to 1808 and de-
sirable for the formation of a
linear bond. The S(1A)-
O(1A)-S(2A) angle for 2 (S-A)
is 158.21(4)8,[19] which is more
suitable for the central px orbi-
tal at the O(1) atom to form a
linear 5c–6e C2S2O system than
is the case of 1.
Figure 2. Structure of 2 (S-A): a) side view and b) top view (thermal ellipsoids are shown at the 50% probabil-
ity level).
In the case of 3, the
O(1)···O(3) and O(1)···O(4)
nonbonded
distances
are
2.6169(15) and 2.6129(15) Š,
which are 0.42–0.43Š shorter
than the sum of the van der
Waals radii of the atoms
(3.04 Š).[18] The O(1)-O(3)-
C(15), O(1)-O(4)-C(16), and
O(3)-O(1)-O(4) angles are
155.05(9),
151.15(9),
and
150.15(6)8, respectively, which
deviate from 1808 by about
308. The deviations of all three
angles are borderline for the
formation of the 5c–6e C2O2O
Figure 3. Structure of 3: a) side view and b) top view (thermal ellipsoids are shown at the 50% probability
level).
than the sum of the van der Waals radii of the atoms
(3.42 Š).[18] The O(1)-Se(1)-C(15) and O(1)-Se(2)-C(16)
angles are 174.68(7) and 174.33(7)8, respectively, which are
close to 1808 and desirable for the formation of a linear
bond. The Se(1)-O(1)-Se(2) angle is 150.72(6)8, which is a
deviation of about 308 from 1808. The angle is mainly deter-
system in 3. Similarly, the O···O nonbonded distances of
2.613–2.617 Š would also be borderline for the interaction.
Therefore, the 5c–6e C2O2O interaction would be weak in 3,
even if it forms.
AIM analysis: The BB forms observed for 1–3[3,17] must be
ꢁ
ꢁ
ꢁ
ꢁ
mined by the O(1) C(13), Se(1) C(1), and Se(2) C(11) dis-
tances, as well as the angles around the atoms. If nonbonded
more stable than the AA forms; the Z CMe bonds are in the
ATQ plane in BB and are almost perpendicular to the plane
ꢁ
3c–4e np(O)···s*
sides of the central np(O) orbital and the two interactions
are connected effectively through the common np(O) orbi-
(Se C)-type interactions occur on both
in AA (Scheme 2). The structures of 1–3 were optimized by
[20]
employing the Gaussian 03program
with the 6-311+G-
AHCTREUNG
ꢁ
ꢁ
tal, the resulting nonbonded s*
teraction leads to the formation of the 5c–6e C2Se2O system.
(C Se)···np(O)···s*
U
ACHTREUNG
hydrogen atoms. Calculations were performed at the density
functional theory (DFT) level of the Becke three-parameter
Indeed, a 308 deviation of aSe(1)O(1)Se(2) would be bor-
258
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
hybrid functionals with the
FULL PAPER
Lee–Yang–Parr
correlation
functional (B3LYP). The BB
forms of 1–3 were optimized
as the global minima, which
reproduce well the observed
structures of 1–3. The AA
forms are local ones. The
structures of AA and BB in 4–
6 and A and B in 7–12 were
also optimized by using the
method applied to 1–3.
AIM analysis was performed
by applying the AIM2000 pro-
gram[21] to the optimized BB
structures of 1–6 and B struc-
tures of 7–12 using the Gaussi-
an 03program. Table 3shows
the results of the AIM analy-
sis, giving the electron charge
density and the total electronic
energy density at the BCP be-
tween the Z and oxygen atoms
&
*
Figure 5. a) BCPs ( ), ring critical points ( ), and bond paths of 4 and b) the partial contour map of 1b(rc) of 4
in the O1-Se2-C9 and O1-Se1-C9 planes. The contours [eaoꢁ3] are at 2l (l=ꢂ8, ꢂ7, …0), 0.3028, 0.0216 (dotted
line), and 0.0047 (heavy line).
(1b(rc) and Hb(rc), respectively). Table 3also gives the natu-
ral charges at the Z and oxygen atoms (Qn(Z) and Qn(O),
respectively), calculated by the natural population analy-
sis.[22] Figures 4 and 5 exhibit BCPs, bond paths, and the con-
tour maps of 1b(rc) drawn on the optimized structures of 1
and 4, respectively. Table 4 summarizes some of the data re-
lating to the BCPs of the weak interactions reported in this
work.[10a,11,13a] Table 4 also gives data recalculated by a
method similar to that used in this work, using the 6-311++
B3LYP/6-311++G(2df,2p) method were employed to gain
A
a better understanding of the nature of the interactions.
Before discussing the results for the 5c–6e C2Z2O interac-
tions in 1–6, it may be instructive to start with a discussion
of the 3c–4e CZO interactions in 7–12.
AIM analysis of 3c–4e CZO in 7–12 with 1b(rc): The charge
densities at the BCP (1b(rc)) between the nonbonded Z···O
atoms in 7 (Z=Se) and 8 (Z=S) of the ATQ system were
ꢁ3
G
(2df,2p) basis set at the B3LYP and/or MP2 levels, for con-
evaluated to be 0.027 and 0.025 eao (ao =0.52177 Š), re-
venience of comparison.[23] The values recalculated with the
spectively (Table 3). While the 1b(rc) values for 7 and 8 are
smaller than that for HCN···HF (0.034 eaoꢁ3), they are
larger than those for H2O···HOH (0.024 eaoꢁ3) and HF···HF
(0.025 eaoꢁ3), although the 1b(rc) value for 8 is essentially
equal to the latter (Table 4).[10a] The results suggest that the
Z···O interactions in 7 (Z=Se) and 8 (Z=S) are stronger
than the hydrogen bond in H2O···HOH (and HF···HF), but
weaker than the bond in HCN···HF.[10a] The values for 10
(Z=Se) and 11 (Z=S) of the 9-MeOATC system are 0.022
and 0.021 eaoꢁ3, respectively (Table 3), which are smaller
than that for H2O···HOH, but larger than that for NN···HF
(0.018 eaoꢁ3) (Table 4).[10a] The Z···O interactions in 10 (Z=
Se) and 11 (Z=S) are substantially stronger than the hydro-
gen bond in NN···HF, but weaker than the hydrogen bond in
H2O···HOH.[10a] In the case of Z=O, the 1b(rc) values for 9
and 12 are 0.017 and 0.018 eaoꢁ3, respectively. These values
are slightly smaller than that for NN···HF, but are apparent-
ly larger than those corresponding to the van der Waals in-
teractions in Ne···HF and Ar···HF (1b(rc)=0.006 and
0.008 eaoꢁ3, respectively) (Table 4).[10a] The results are sum-
marized in Equation (1).
Figure 4. Contour map of 1b(rc) of 1 in the anthraquinone plane, together
&
*
with BCPs ( ), ring critical points ( ), and bond paths. The contours
[eaoꢁ3] are at 2l (l=ꢂ8, ꢂ7, …0), 0.3028, 0.0269 (dotted line), and 0.0047
(heavy line).
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
259

W. Nakanishi et al.
260
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
Table 4. Results of the AIM analysis of weak interactions.
FULL PAPER
ꢁ3
2
ꢁ5
Adducts
BCP
(A, B)
Distance [Š]
(A, B)
1b(rc) [eao
]
5 1b(rc) [eao
]
Hessian eigenvalue
Hb(rc) [au]
Qn(A)
Qn(B)
G
r
G
jl1 j/l3
van der Waals
[a,b]
ꢁ
Ne HF
U
2.110
2.3211
2.562
0.0099
0.0058
0.0077
0.0079
0.0484
0.0295
0.0311
0.0302
0.180
0.161
0.170
0.174
[c,d]
ꢁ
Ne HF
0.0014
0.0016
0.0009
0.0031
0.5513
0.5508
[a,b]
ꢁ
Ar HF
[c,d]
ꢁ
Ar HF
2.5573
hydrogen bonds
[a,b]
ꢁ
NN HF
U
2.076
2.0639
2.039
1.9521
1.9576
1.778
1.8440
1.8291
1.881
0.0169
0.0175
0.0198
0.0233
0.0236
0.0262
0.0233
0.0250
0.0284
0.0338
0.0647
0.0636
0.0623
0.0832
0.0801
0.1198
0.0936
0.0939
0.0920
0.0944
0.200
0.209
0.223
0.214
0.222
0.204
0.213
0.224
0.236
0.266
[c,d]
ꢁ
NN HF
0.0024
ꢁ0.0468
0.5567
[b,e]
[c,f]
[c,d]
A
G
0.0012
0.0015
ꢁ0.9365
ꢁ0.9334
0.4854
0.4831
U
[b,e]
(HF)2
(HF)2
(HF)2
[c,f]
0.0007
0.0008
0.5541
0.5604
ꢁ0.5487
ꢁ0.5550
[c,d]
[a,b]
[c,d]
ꢁ
HCN HF
HCN HF
ꢁ
1.8200
ꢁ0.0013
ꢁ0.3801
0.5649
trihalide linear anions
[Br3]ꢁ[c,d,g]
[Cl3]ꢁ[g–i]
N
A
2.6212
2.3459
0.0579
0.0668
0.295
ꢁ0.0107
ꢁ0.0180
ꢁ0.0060
ꢁ0.1010
ꢁ0.1086
ꢁ0.1018
ꢁ0.4495
ꢁ0.4457
ꢁ0.4491
N
0.0630.117
0.0762
0.100
0.1099
0.022
0.259
G
0.0951
0.539
0.5404
0.058
0.311
0.199
0.217
0.266
[F3]ꢁ[g–i]
[F3]ꢁ[c,d,g]
13 (C2v)[j,k]
1.7275
2.431
[a] With the MP2/6-311G
ACHTREUNG
G
A
ACHTREUNG
of the Gaussian 03program. [g] The central atom being called A and the outside ones B. [h] With the 6-311 ++G** method. [i] See ref. [11]. [j] With the
6-31G(d) method at the DFT (B3PW91) level of the Gaussian 98 program. [k] See ref. [13a].
ꢁ3
Ar Á Á Á HF ð1bðrcÞ ¼ 0:008 e ao Þ ꢃ O Á Á Á O ð12 : 0:016Þ ꢄ
(Z=Se: e=0.21) and 11 (Z=S: 0.21) of the 9-MeOATC
system. The values are also much larger than those for
O Á Á Á O ð9 : 0:017Þ ꢄ NN Á Á Á HF ð0:018Þ < S Á Á Á O ð11 :
0:021Þ ꢄ Se Á Á Á O ð10 : 0:022Þ < H2O Á Á Á HOH ð0:024Þ ꢄ
S Á Á Á O ð8 : 0:025Þ ¼ HF Á Á Á HF ð0:025Þ < Se Á Á Á O ð7 :
0:027Þ ꢃ HCN Á Á Á HF ð0:034Þ
H2C=Se (e=0.13) and H2C=S (e=0.05),[12] although the
basis sets used for the calculations were not the same. The
ꢁ
results show that p–p conjugation is significant in the C1
Z
bonds of 7, 8, 10, and 11. The values for 9 (Z=O: e=0.04)
and 12 (Z=O: 0.05) are similar to the value of the ellipticity
of H2C=O (0.04).[12,24] The values of the ellipticity in the
Z···O interactions in 7 (Z=Se: e=0.09) and 8 (Z=S: 0.07)
are similar to those in 10 (Z=Se: e=0.08) and 11 (Z=S:
0.07). The magnitude of the p character of the Z···O bonds
in 7 and 8 is comparable to that in 10 and 11, although 10
and 11 seem to have no suitable p orbitals with which to
ð1Þ
2
ꢁ5
The 5 1b(rc) values for 7–12 are 0.070–0.084 eao (Table 3).
The values lie in the range of hydrogen-bonded adducts
(0.064–0.094 eaoꢁ5). In general, negative values of 5 1b(rc)
2
appear at the BCPs of covalent bonds, whereas positive
values correspond to ionic bonds.[10] The positive values of
construct the p(Z···O) interactions. The values for the Z···O
R
2
5 1b(rc) in 7–12 are well understood based on this generali-
interactions in 7, 8, 10, and 11 are larger than that for H2C=
S and smaller than that for H2C=Se.[12] While the ellipticity
of the O···O interactions in 9 (e=0.07) is very close to the
values for 8 and 11, that for 12 (0.04) is smaller.
After elucidation of the nature of the BCPs in 7–12, we
extended this study to the BCPs of the 5c–6e C2Z2O interac-
tions in 1–6.
zation. The ionic nature of the nonbonded Z···O interactions
for Z=Se and S are well understood based on the CT of hy-
ꢁ
pervalent np(O)!s*
C
AIM analysis of 5c–6e C2Z2O in 1–6 with 1b(rc): The opti-
mized structures of 1–3 are of C2v symmetry and those of 4–
6 are of Cs symmetry.[25] Therefore, the nature of the two
ꢁ
The contributions of p character to the C1 Z bonds of 7–
12 were examined. The ellipticities of the p–p conjugation
ꢁ
ꢁ
ꢁ
of p(Z) p
(ATQ) type in 7 (Z=Se: l1/l2ꢁ1=e=0.23) and 8
BCPs in the nonbonded C Z···O···Z C interactions in 1–6 is
the same. One of them is listed in Table 3.
(Z=S: 0.23) of the ATQ system are larger than those of 10
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
261

W. Nakanishi et al.
ꢁ
ꢁ
The 1b(rc) values for the nonbonded C Z···O···Z C inter-
(1,2-C6H4O2B)-1,8-(MeO)2C14H7 (13).[13]
The 1b(rc) value is 0.022 eao for the
ꢁ3
ꢁ3
actions in 1 (Z=Se) and 2 (Z=S) are 0.027 and 0.026 eao
,
respectively, and those for 4 (Z=Se) and 5 (Z=S) are both
C2v symmetric structure. While the
1b(rc) value for 13 is larger than those
for the O···O interactions in 3 and 6, it
is smaller than those for the O···Z (Z=
Se and S) interactions in 1, 4, 2, and 5,
although the method of calculation was
not the same. Because the conforma-
tion around the MeO groups in 13 is
BB, the ns(O) orbitals must act as
donors in 13. The conformations around Me Z (Z=Se, S,
and O) in 1–6 are all BB, therefore, the np(O) orbital of the
central oxygen atom will play an important role in 1–6 as
the donor. The direction of CT in 1–6 is completely different
from that in 13: CT in 1–6 is of the s*
ꢁ3
ꢁ
ꢁ
0.022 eao . The values of the C O···O···O C interactions in
3 and 6 are both 0.018 eaoꢁ3. The results for the 5c–6e
C2Z2O interactions of 1–6 are summarized in Equation (2),
along with the data for some hydrogen-bonded adducts.
ꢁ3
NN Á Á Á HF ð1bðrcÞ ¼ 0:018 e ao Þ ¼ O Á Á Á O ð3 : 0:018Þ ¼
O Á Á Á O ð6 : 0:018Þ < S Á Á Á O ð5 : 0:022Þ ¼ Se Á Á Á O ð4 :
0:022Þ < H2O Á Á Á HOH ð0:024Þ ꢄ HF Á Á Á HF ð0:025Þ ꢄ
S Á Á Á O ð2 : 0:026Þ ꢄ Se Á Á Á O ð1 : 0:027Þ ꢃ
ꢁ
HCN Á Á Á HF ð0:034Þ
!
ð2Þ
ꢁ
(C Z) np(O)!s*-
ꢁ
A
!
The results show that the values of 1b(rc) for 1 and 2 of the
ATQ system are larger than those for H2O···HOH and
HF···HF, whereas those for the 9-MeOATC system with Z=
Se and S are smaller than that for H2O···HOH. The values
for the O···O interactions are essentially equal to that for
NN···HF.
np(B) ns(O) type.[26,27]
Linear trihalide ions, X3 , are typical examples of 3c–4e
ꢁ
ꢁ
ꢁ
ꢁ
interactions. The 1b(rc) values for F3 , Cl3 , and Br3 are
0.110, 0.076, and 0.058 eaoꢁ3, respectively (Table 4). These
values are about four, three, and two times larger than that
of 1, respectively. The values decrease in the order F3
ꢁ
>
ꢁ
ꢁ
Equations (1) and (2) were combined to give Equa-
tion (3). The characteristics of the 5c–6e C2Z2O and 3c–4e
CZO interactions of 1–12, predicted on the basis of the
values of 1b(rc), are as follows: 1b(rc) values for 5c–6e Z2C2O
for Z=Se and S are essentially equal to those for 3c–4e
ZCO, respectively, if the system is the same, whereas the
former is slightly larger than the latter for Z=O. The results
are in accord with the expectation that the Z···O interactions
in 5c–6e C2Z2O (Z=Se, S, and O) are very similar to those
in 3c–4e CZO. No saturation effect was detected in 5c–6e
C2Z2O, relative to 3c–4e CZO, on the basis of the 1b(rc)
values. These results demonstrate that the extended hyper-
ꢁ
Cl3ꢁꢁ>Br3 . The stability of X3 relative to X2 and Xꢁ, (DE-
ꢁ
(X3 )=E
(X3 )ꢁE(X2)ꢁE(Xꢁ)) were evaluated to be
ꢁ142.0, ꢁ124.1, and ꢁ137.7 kJmolꢁ1, for X=F, Cl, and Br,
respectively. The stabilization energies do not correlate well
with 1b(rc), which shows that 1b(rc) does not reflect the sta-
bility in some cases.
After examination of the nature of the 5c–6e C2Z2O and
3c–4e CZO interactions based mainly on 1b(rc) values, the
next step was to employ the total electronic energy density
at the BCP (Hb(rc)), which will be a more appropriate index
for the weak interactions.
valent 5c–6e interactions in 1–6 of the s*
A
AIM analysis on 5c–6e C2Z2O and3c–4e CZO with Hb(rc):
The total electronic energy density at the BCP (Hb(rc)) is
the sum of the electronic potential (V) and kinetic energy
(G) densities at the BCP (Hb(rc)=Gb(rc)+Vb(rc)).[28] The
values of Hb(rc) for 5c–6e C2Z2O and 3c–4e CZO interac-
tions in 1–12 are also collected in Table 3. Gb(rc) and Vb(rc)
are positive and negative, respectively, although not shown
in Table 3. Because the magnitudes of Gb(rc) are slightly
larger than the corresponding Vb(rc) values, Hb(rc) values for
1–12 show a slightly positive nature. As also recognized in
Table 3, Hb(rc) values are negative for classical chemical
ꢁ
A
(Z C) elements effectively through the central np(O) orbi-
tal.
ꢁ3
Ar Á Á Á HF ð1bðrcÞ ¼ 0:008 e ao Þ ꢃ O Á Á Á O ð12 : 0:016Þ ꢄ
O Á Á Á O ð9 : 0:017Þ ꢄ NN Á Á Á HF ð0:018Þ ¼ O Á Á Á O ð3 :
0:018Þ ¼ O Á Á Á O ð6 : 0:018Þ < S Á Á Á O ð11 : 0:021Þ ꢄ
S Á Á Á O ð5 : 0:022Þ ¼ Se Á Á Á O ð4 : 0:022Þ ¼ Se Á Á Á O ð10 :
0:022Þ < H2O Á Á Á HOH ð0:024Þ ꢄ HF Á Á Á HF ð0:025Þ ¼
S Á Á Á O ð8 : 0:025Þ ꢄ S Á Á Á O ð2 : 0:026Þ ꢄ Se Á Á Á O ð1 :
0:027Þ ¼ Se Á Á Á O ð7 : 0:027Þ ꢃ HCN Á Á Á HF ð0:034Þ
ꢁ
bonds in 1–12. The values for X3 (X=F, Cl, and Br) and
HCN···HF are also negative. However, those for the van der
Waals and hydrogen-bonded adducts in Table 4 are positive,
except in the case of HCN···HF: the positive values of
Hb(rc) correspond to the ionic interactions.[11,12] The Hb(rc)
ð3Þ
ꢁ
values for the nonbonded O···Z C interactions in 1–12 are
all positive (Table 3). The Hb(rc) values will clarify the
The p character of the nonbonded Z···O interactions in 5c–
6e C2Z2O is essentially the same as that in 3c–4e CZO, and
nature of the interactions.
ꢁ
ꢁ
so are the C1 Z and C=O bonds (Table 3).
Yamamoto and co-workers reported the AIM analysis of
the O···B···O 3c–4e interactions at the 1,8,9-positions of 9-
The values of Hb(rc) for the nonbonded O···Z C interac-
tions of 1–12 are summarized in Equation (4), together with
those for hydrogen-bonded adducts. The nonbonded O···Z
262
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
FULL PAPER
interactions are classified into three groups by their Hb(rc)
The points for 1–12 appear along with the dotted line in
Figure 6. They form three groups: g(a), g(b), and g(c).
Groups g(a) and g(b) consist of the ATQ system with Z=Se
and S (1, 7, 2, and 8) and the 9-MeOATC system with Z=
Se and S (4, 5, 10, and 11), respectively. On the other hand,
the ATQ and 9-MeOATC systems with Z=O (3, 6, 9, and
12) belong to g(c) (=g(O)). The points for H2O···HOH and
HF···HF appear very near those in g(a). Therefore, the
nature of the 5c–6e C2Z2O and 3c–4e CZO interactions in
g(a) must be similar to hydrogen bonds. This expectation is
also supported by the fact that the slope of the points in
g(a) is almost parallel to that of the dotted line. The nature
of 5c–6e C2Z2O and 3c–4e CZO interactions in g(b) was an-
alyzed similarly. However, the points for g(c) are near that
of NN···HF, the top of the dotted line, and seem to be on
the down slope leading to Ar···HF and Ne···HF. Consequent-
ly, it would be difficult to analyze the linear C2Z2O and
CZO (Z=O) interactions in g(c) similarly to the cases of
g(a) and g(b) (Z=Se and S) on the basis of the values of
Hb(rc). Groups g(a) and g(b) can be reclassified as g(Se) and
g(S), as shown in Figure 6.
Why is the saturation effect not observed in the formation
of 5c–6e C2Z2O interactions from a pair of 3c–4e CZO inter-
actions? We noted the bond distances of the compounds
predicted by the QC calculations. Shorter Z···O distances
were predicted for 1 (2.649 Š) versus 7 (2.652 Š) (Z=Se), 2
(2.626 Š) versus 8 (2.640 Š) (Z=S), and 3 (2.578 Š) versus
9 (2.612 Š) (Z=O) in the ATQ system. The differences in-
crease in the order: Dr(1, 7: ꢁ0.003Š) <Dr(2, 8:
ꢁ0.014 Š)<Dr(3, 9: ꢁ0.034 Š). The smaller distances in 5c–
6e C2Z2O relative to 3c–4e CZO must operate to prevent
saturation. On the other hand, the Z···O distances in the 9-
MeOATC system were predicted to be longer in 4 (2.765 Š)
versus 10 (2.755 Š) (Z=Se) and in 5 (2.714 Š) versus 11
(2.720 Š) (Z=S). The flexible MeO group at the 9-position
must be responsible for the elongation of the bonds.
values. 0.0028ꢀHb
Z=S)ꢀ0.0012, and 0.0008ꢀHb
fore, Hb
(rc: Z=O)ꢅHb(rc: NN···HF), Hb(rc: H2O···HOH)ꢀ
Hb (rc:
A
N
AHCTREUNG
ACHTREUNG
A
ACHTREUNG
Z=S). Hb(rc) values for the O···Z interactions decrease in
the order Z=O@S>Se. It has been demonstrated that the
ꢁ
ꢁ
s*
A
ACHTREUNG
ꢁ
formed by the connection of two np(O)···s*
A
tities through the central np(O) orbital, again based on
values of Hb(rc).
O Á Á Á O ð3 : HbðrcÞ ¼ 0:0028 auÞ ¼ O Á Á Á O ð6 : 0:0028Þ >
O Á Á Á O ð9 : 0:0025Þ ꢀ NN Á Á Á HF ð0:0024Þ ꢀ O Á Á Á O ð12 :
0:0023Þ ꢆ H2O Á Á Á HOH ð0:0015Þ > S Á Á Á O ð8 : 0:0013Þ ¼
S Á Á Á O ð2 : 0:0013Þ ꢀ S Á Á Á O ð11 : 0:0012Þ ¼ S Á Á Á O ð5 :
0:0012Þ > HF Á Á Á HF ð0:0008Þ ¼ Se Á Á Á O ð10 : 0:0008Þ ¼
Se Á Á Á O ð4 : 0:0008Þ ꢀ Se Á Á Á O ð1 : 0:0007Þ ꢀ Se Á Á Á O ð7 :
0:0006Þ ꢆ HCN Á Á Á HF ðꢁ0:0013Þ
ð4Þ
To clarify the relation between Hb(rc) and 1b(rc) in 1–12,
Hb(rc) was plotted versus 1b(rc) for the compounds given in
Equation (3). Figure 6 shows the results. The plots for the
hydrogen-bonded and van der Waals adducts are represent-
ed by an upward convex curve, shown by the dotted line.
The point for NN···HF is very near to the top. While the
points for the hydrogen-bonded adducts are on the right-
side down slope, those for the van der Waals adducts are on
the left-side down slope.[29]
Figure 7 shows the optimized structures of 4 (BB) and 10
(B). The larger flip angle for the MeO group at the 9-posi-
tion of 4 (BB), relative to that of 10 (B), results in the
longer Se···O distance for 4 (BB) relative to 10 (B). The tor-
ꢁ
sional angle of the O CMe bond with respect to the ATC
plane in 4 (BB) is f
A
right angle than in the case of 10 (B) (101.78). The observed
structural features in 4 (BB) and 10 (B) must be controlled
Figure 6. Plots of Hb(rc) versus 1b(rc) for 1–12 as well as hydrogen-
bonded (HCN···HF (i), HF···HF (ii), H2O···HOH (iii), and NN···HF (iv))
and van der Waals adducts (Ar···HF (v) and Ne···HF (vi)). The plot for
i–vi is connected by a smooth dotted line. The slope for 1–12 and i–iv is
shown by a solid line (correlation: y=ꢁ0.21x+0.0060; r=0.91). The
ATQ system with Z=Se and S construct g(a) and the 9-MeOATC
system with Z=Se and S form g(b). Groups g(a) and g(b) have been re-
classified into g(Se) and g(S). Points for Z=O in both systems belong to
g(c) (=g(O)).
Figure 7. Optimized structures of a) 4 (BB) and b) 10 (B). The optimized
torsional angles (f
101.78, respectively.
A
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
263

W. Nakanishi et al.
by the weak interactions, such as the steric repulsions and
attractive interactions in the molecules, which are closely re-
lated to the stabilities.
with aZOZ=151–1588 than expected based on the 3c–4e
CZO interactions.
Energy-lowering effect by 5c–6e C2Z2O and3c–4e CZO :
Table 6 collects the energies and selected bond distances
and angles optimized for AA and BB in 1–6 and A and B in
7, 8, and 10.[30]
NBO analysis of 5c–6e C2Z2O and3c–4e CZO : How are the
5c–6e C2Z2O and 3c–4e CZO interactions stabilized? The
second-order perturbation of the NBO analysis[22] was exam-
ꢁ
ꢁ
ined for the s*
G
U
The energy differences between BB and AA (DE(n)=E-
ꢁ
A
A
G
8. The stabilization energy, E(2), associated with the delocal-
ization of the NBO (i)!NBO (j) type, is estimated by Equa-
tion (5), in which qi is the donor orbital occupancy, ei and ej
values of DE(1), DE(2), DE(4), and DE(5) are ꢁ49.9, ꢁ38.9,
ꢁ33.1, and ꢁ25.2 kJmolꢁ1, respectively. The differences
must be a reflection of the stabilization in 5c–6e C2S2O rela-
tive to 5c–6e C2Se2O and the p–p conjugation of np(Se)–p-
are the orbital energies of diagonal elements, and F(i,j) is
N
the off-diagonal NBO Fock matrix element. Table 5 shows
the results, with the values for 5c–6e C2Z2O corresponding
to half of the 5c–6e interactions.
C
G
2
Eð2Þ ¼ qiFði,jÞ =ðejꢁeiÞ
ð5Þ
ATQ system if
same.[31]
Z
is the
ꢁ
Table 5. Contributions of donor–acceptor interactions of the n(O)···s*(Z C) type in 5c–6e C2Z2O and 3c–4e
CZO (Z=Se and S) systems.
A
The nonbonded Z···O dis-
tances in BB are shorter than
[a]
NBO (i)
1 (BB)[d]
np(O)
NBO (j)
E(2) [kJmolꢁ1
]
DE [au][b]
F
N
Character
those in AA (Dr(n)=r
A
ꢁ
s*
s*
N
)
)
18.5
10.6
0.40
0.81
0.039
0.041
5c–6e
ns!s*
BB)ꢁr(n: AA)<0, for n=1–
AHCTREUNG
ns(O)
2 (BB)[e]
np(O)
6). The values of Dr(1), Dr(2),
Dr(4), and Dr(5) are ꢁ0.336,
ꢁ0.308, ꢁ0.270, and ꢁ0.239 Š,
respectively. The large steric
repulsion in AA must be re-
duced by the longer r(AA).
On the other hand, the en-
larged steric repulsion caused
by the shorter r(BB) would be
compensated by the energy-
lowering effect through the
formation of a 5c–6e C2Z2O in-
teraction, together with p–p
conjugation.
ꢁ
s*
s*
N
)
)
13.4
8.0
0.45
0.86
0.035
0.031
5c–6e
ns!s*
ns(O)
7 (B)[f]
np(O)
ꢁ
s*
s*
N
)
)
24.6
8.0
0.40
0.80
0.044
0.035
3c–4e
ns!s*
ns(O)
8 (B)[g]
np(O)
ꢁ
s*
s*
N
)
)
15.4
4.4
0.45
0.86
0.037
0.027
3c–4e
ns!s*
ns(O)
[a] Second-order perturbation energy in the NBO analysis. [b] DE=E(j)ꢁE(i). [c] F
NBO Fock matrix element. See Equation (5). [d] aC9OSe=104.268, aOSeCMe =173.738, aSeOSe=151.488.
[e] aC9OS=101.078, aOSCMe =179.798, aSOS=157.858. [f] aC9OSe=103.578, aOSeCMe =173.958.
[g] aC9OS=99.958, aOSCMe =179.968.
ꢁ
Contributions of CT from both np(O) and ns(O) to s*
A
in 1, 2, 7, and 8 are 58.2, 42.8, 32.6, and 19.8 kJmolꢁ1, re-
spectively. The values are close to the evaluated energy dif-
ferences between BB and AA (or B and A) for these com-
pounds, which are ꢁ49.9, ꢁ38.9, ꢁ25.5, and ꢁ19.7 kJmolꢁ1,
respectively (see Table 6). CT is mainly responsible for DE,
although the magnitudes of DE are smaller than the CT
contributions.
The energy differences between B and A (DE(n)=E
A
B)ꢁE
The DE(7), DE(8), and DE(10) values are ꢁ25.5, ꢁ19.7, and
ꢁ10.8 kJmolꢁ1, respectively. Whereas the DE(1) and DE(2)
values are nearly twice as large as DE(7) and DE(8), respec-
tively, DE(4) is about three times as large as DE(10). The
flexibility around the MeO group must be responsible for
!
ꢁ
Note that ns(O), as well as np(O), contribute much to the
these predictions (see Figure 7). The s*
A
ꢁ
ꢁ
ꢁ
s*
A
(Z C) 5c–6e and n(O)···s*
(Z C) 3c–4e
(Z C) 5c–6e interaction is demonstrated to operate effec-
ꢁ
interactions. The contributions of ns(O), relative to np(O),
are 57, 60, 33, and 29% for 1 (BB), 2 (BB), 7 (B), and 8
(B), respectively (Table 5). These ratios must essentially be
controlled by aZOC9 and aOZCMe, as well as aZOZ. The
ratios for 5c–6e C2Z2O (Z=Se and S) are about twice as
large as those for 3c–4e CZO (Z=Se and S), respectively.
The results show that there is a greater chance of ns(O)
tively by the connection of two np(O)!s*
C
Scheme for the formation of 5c–6e C2Z2O interactions: Ex-
ꢁ
tended hypervalent 5c–6e C2Z2O interactions of the s*
A
ꢁ
ꢁ
ꢁ
taking part in the s*
(C Z)···n(O)···s*
(Z C) interactions
Z)···np(O)···s*
(Z C) type will form when two hypervalent
264
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
FULL PAPER
Scheme 4. Formation of 5c–6e C2Se2O starting from 1c–2e np(Se), exem-
plified by phenylselanyl derivatives.
3c–4e CZO interactions are connected effectively through
the central np(O) orbital, as shown in Scheme 3. Scheme 4
shows a scheme for the formation of 5c–6e C2Se2O interac-
tions, as exemplified by the formation of I,[3] starting from
the np(Se) orbital (1c–2e) in 1-(phenylselanyl)anthracene
(III).[32] Path a shows a process via 1-(phenylselanyl)anthra-
quinone (IV)[33] and path b a process via 1,8-bis(phenylsela-
nyl)anthracene (V).[3]
When the two hydrogen atoms at the 9,10-positions in III
are replaced by carbonyl oxygen atoms in path a, III (A)
changes to IV (B) with the formation of 3c–4e CSeO inter-
actions.[33] Anthraquinone I (BB) forms if the hydrogen
atom at the 8-position of IV (B) is then substituted by a
PhSe group in path a. The 3c–4e CSeO interaction in IV (B)
changes to a 5c–6e C2Se2O interaction in this substitution
ꢁ
with two Se CPh bonds and an oxygen atom at the 1,8,9-po-
sitions of I (BB). On the other hand, anthracene III (A)
with a np(Se) orbital (1c–2e) is transformed to V (AA) with
two independent np(Se) orbitals (a couple of 1c–2e) in path
b when the hydrogen atom at the 8-position in III (A) is
substituted by another PhSe group. Anthracene V (AA)
changes to I (BB) by replacement of the hydrogen atoms at
the 9,10-positions in V (AA) with carbonyl oxygen atoms.
In this process, the two independent np(Se) orbitals (a pair
of independent 1c–2e) in V (AA) are incorporated into the
5c–6e C2Se2O interaction in I (BB). A similar scheme can
be drawn for II.
ꢁ
ꢁ
AIM analysis of 1–12 revealed the nature of C Z···O···Z
ꢁ
C 5c–6e (Z=Se, S, and O) and C Z···O 3c–4e interactions.
NBO analysis and the energies calculated for 1–12 support
the discussion. The structural change from III (A) to I (BB)
in Scheme 4 shows how 5c–6e C2Se2O interactions are con-
structed from a np(Se) orbital (1c–2e) through 3c–4e CSeO
interactions or two independent np(Se) orbitals (a pair of in-
dependent 1c–2e).
Conclusion
ꢁ
The nature of BCPs in the np(O)···s*
(Z=Se, S, and O) in 1–12 has been examined by using the
AIM method after determination of the structures of 1–3 by
A
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
265

W. Nakanishi et al.
300) and acidic and basic alumina (E. Merk). Flash column chromatogra-
phy was performed with 300—400 mesh silica gel and acidic and basic
alumina. Analytical thin-layer chromatography was performed on pre-
coated silica gel plates (60F-254) using the systems (v/v) indicated. Ele-
mental analyses were performed by using a J-Science Lab Co., Ltd.,
JM10 Micro Corder.
means of X-ray crystallographic analysis. The 1b(rc) values
ꢁ
of the np(O)···s*
A
12 are summarized in Equations (1)–(3). The 1b(rc) and
2
5 1b(rc) values of the BCPs in the nonbonded Z···O···Z in-
teractions in 1–6 are, respectively, very close to those corre-
sponding to the O···Z interactions in 7–12. Consequently,
1,8-Bis(methylselanyl)anthraquinone (1): A suspension of dimethyl dise-
lenide (1.00 g, 5.32 mmol) and sodium hydride (0.49 g, 12.77 mmol) in
dry DMF (60 mL) was heated at 1108C for 1 h. Then 1,8-dibromoanthra-
quinone (1.47 g, 5.32 mmol) and CuI (2.33 g, 12.23 mmol) were added to
the solution at 1108C. After stirring for 3h at 140 8C, the solution was
subjected to dry chromatography on silica gel (dichloromethane as
eluent) and concentrated under vacuo. The product was purified by using
chromatography on silica gel (benzene as eluent) and recrystallized from
benzene/ethanol. Compound 1 was obtained as a red solid (0.12 g, 5.7%
ꢁ
the two np(O)···s*
onstrated to be connected effectively at the central np(O) or-
bital to form extended hypervalent 5c–6e interactions of the
A
ꢁ
ꢁ
s*
of s*
A
ACHTREUNG
!
ꢁ
ACHTREUNG
also applied to the 5c–6e C2Z2O and 3c–4e CZO systems in
1–12, which must be a more appropriate index of weak in-
teractions. The results emphasize that the strength of the in-
teractions increase in the order: O···O !S···O<Se···O.
The contributions of CT to 5c–6e C2Z2O and 3c–4e CZO
were evaluated by using NBO analysis. The results have
been related to the energy differences between structures
BB and AA, which were also calculated. The DE(1) value
1
yield). M.p. 267.5–268.98C; H NMR (300.40 MHz, CDCl3/TMS): d=2.53
(s, 6H; CH3Se), 7.62–7.71 (m, 4H), 8.08 ppm (dd, 3J(H,H)=6.8 Hz, 4J-
G
A
(CH3Se), 124.0, 130.7, 132.6, 132.6, 134.8, 141.8, 183.1 (C=O), 184.2 ppm
(C=O); 77Se NMR (57.25 MHz, CDCl3/MeSeMe): d=315.7 ppm; elemen-
tal analysis calcd (%) for C16H12O2Se2: C 48.75, H 3.07; found: C 48.75,
H 3.17.
1,8-Bis(methylthio)anthraquinone (2): Following a method similar to that
for 1, compound 2 was obtained as orange needles (0.28 g, 23% yield).
M.p. 234.5–235.88C; 1H NMR (300.40 MHz, CDCl3/TMS): d=2.32 (s,
(=E
N
N
ꢁ38.9 kJmolꢁ1, DE(4)=ꢁ33.1 kJmolꢁ1, and DE(5)=
ꢁ25.2 kJmolꢁ1. The differences must reflect the stabilization
of 5c–6e C2S2O relative to 5c–6e C2Se2O and the p–p conju-
6H; CH3S), 7.65 (t, 3J
C
ACHTREUNG
A
(74.45 MHz, CDCl3/TMS): d=65.6 (CH3S), 122.8, 129.2, 129.5, 132.6,
134.2, 145.9, 183.2 (C=O), 184.1 ppm (C=O); elemental analysis calcd
(%) for C16H12O2S2: C 63.97, H 4.03; found: C 63.85, H 4.13.
gation of the np(Se)–p
A
p
ACHTREUNG
(3):[34]
Sodium
hydride
(0.83g,
are 0.76–0.78, which shows that the energy-lowering effect
of 5c–6e C2S2O is about three quarters that of 5c–6e C2Se2O,
if the system is the same. The ratios of DE(4)/DE(1) and
DE(5)/DE(2) are 0.65–0.66, which shows that the effect in
the 9-MeOATC system is about two thirds that in the ATQ
group, if Z is the same. Nonbonded Z···O distances were
also examined: r(AA) is longer than the corresponding
r(BB) distance in 1–6. The large steric repulsion must be re-
duced in AA by the longer r(AA) and the increased steric
repulsion caused by the shorter r(BB) would be compensat-
ed by the energy-lowering effect through the formation of
5c–6e C2Z2O as well as the p–p conjugation.
The structures of the phenylselanyl derivatives of ATQ
provide a scheme detailing the formation of the 5c–6e
C2Se2O system, starting from np(Se) (1c–2e), by two path-
ways. One is by way of the 3c–4e CSeO system and the
other is through two independent np(Se) orbitals (a pair of
independent 1c–2e). The scheme clarifies how weak interac-
tions such as 5c–6e C2Se2O determine the fine structures of
compounds.
1,8-Bis
G
21.68 mmol) was added to a solution of chrysazin (2.00 g, 8.33 mmol) in a
mixture of dry THF (40 mL) and dry DMF (20 mL). The solution was
stirred for 30 min and then left at reflux for 30 min. Methyl iodide
(1.56 mL, 24.98 mmol) was added to the solution cooled to room temper-
ature. Then the solution was stirred for 2 h at this temperature. As the re-
action was initiated by heating, methyl iodide (1.56 mL, 24.98 mmol) was
added to the solution at 608C. After cooling to 258C, sodium hydride
(0.45 g, 11.62 mmol) was added. The reaction mixture was left at reflux
for 30 min, stirred at room temperature overnight, and then concentrat-
ed. The crude product was purified by using chromatography on silica gel
(dichloromethane as eluent) and recrystallized from benzene/ethanol.
Compound 3 was obtained as yellow needles (1.79 g, 78% yield). M.p.
225.8–226.88C; 1H NMR (300.40 MHz, CDCl3/TMS): d=4.01 (s, 6H;
CH3O), 7.30 (d, 3J
(H,H)=8.1 Hz, 2H),
7.83ppm (d, 3J(H,H)=7.5 Hz, 2H); 13C NMR (74.45 MHz, CDCl3/TMS):
d=56.5 (CH3O), 118.0, 118.8, 123.9, 133.8, 134.7, 159.4, 182.8 (C=O),
184.0 ppm (C=O); elemental analysis calcd (%) for C16H12O4: C 71.64, H
4.51; found: C 71.62, H 4.54.
X-ray structure determination: Single crystals of red prisms of 1, orange
needles of 2, and yellow needles of 3 were obtained by slow evaporation
of solutions of the compounds dissolved in benzene containing ethanol.
X-ray diffraction data for 1–3 were collected on a Rigaku/MSC Mercury
CCD diffractometer equipped with a graphite-monochromated MoKa ra-
diation source (l=0.71070 Š) at 103(2) K. The structures of 1–3 were
solved by direct methods (SIR97),[35] and refined by the full-matrix least-
squares method on F2 for all reflections (SHELXL-97).[36] All non-hydro-
gen atoms were refined anisotropically; hydrogen atoms were refined iso-
tropically.
Experimental Section
CCDC-603371 (1), CCDC-603372 (2), and CCDC-603373 (3) contain the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from the Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
General: Manipulations were performed under nitrogen or argon using
standard vacuum-line techniques. Glassware was dried at 1308C over-
night. Solvents and reagents were purified by standard procedures as nec-
essary. Melting points were measured with a Yanako MP-S3and uncor-
rected. NMR spectra were recorded at 258C with a JEOL JNM-AL 300
spectrometer (1H, 300 MHz; 13C, 75.45 MHz; 77Se, 57.25 MHz). The 1H,
13C, and 77Se chemical shifts are given in parts per million relative to
those of Me4Si, internal CDCl3, and external MeSeMe, respectively.
Column chromatography was performed on silica gel (Fuji Silysia BW-
MO calculations: Ab initio molecular orbital calculations were per-
formed on a Silent-SCC T2 (Itanium2) computer by employing the Gaus-
[20]
sian 03program
with the 6-311+G
(2d,p) basis set for carbon and hy-
drogen atoms. Calculations were performed on structures BB and AA of
A
and selenium atoms and the 6-311+G
ACHTREUNG
266
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268

Extended Hypervalent 5c–6e C2Z2O Interactions
FULL PAPER
1–6, structure B of 7–12, and structure A of 7, 8, and 10 at the density
functional theory (DFT) level of the Becke three-parameter hybrid func-
tional combined with the Lee–Yang–Parr correlation functional
(B3LYP). AIM analysis was performed with the AIM2000 program[20]
after optimization of the structures.
metallics 2002, 21, 884–892; g) J. R. Anacona, J. Gomez, D. Lorono,
Acta Crystallogr., Sect. C 2003, 59, o277–o280; h) G. Mugesh, H. B.
Singh, R. J. Butcher, Eur. J. Inorg. Chem. 1999, 1229–1236; i) R.
Kaur, H. B. Singh, R. P. Patel, J. Chem. Soc., Dalton Trans. 1996,
2719–2726; j) G. Mugesh, H. B. Singh, R. J. Butcher, J. Organomet.
Chem. 1999, 577, 243–248; see also, k) D. Shimizu, N. Takeda, N.
Tokitoh, Chem. Commun. 2006, 177–178.
[10] a) Atoms in Molecules. A Quantum Theory (Ed.: R. F. W. Bader),
Oxford University Press, Oxford, 1990; b) R. F. W. Bader, T. S. Slee,
D. Cremer, E. Kraka, J. Am. Chem. Soc. 1983, 105, 5061–5068;
c) R. F. W. Bader, Chem. Rev. 1991, 91, 893–926; d) R. F. W. Bader,
J. Phys. Chem. A 1998, 102, 7314–7323; e) F. W. Biegler-Kçnig,
R. F. W. Bader, T. H. Tang, J. Comput. Chem. 1982, 3, 317–328;
f) R. F. W. Bader, Acc. Chem. Res. 1985, 18, 9–15; g) T. H. Tang,
R. F. W. Bader, P. MacDougall, Inorg. Chem. 1985, 24, 2047–2053;
h) F. Biegler-Kçnig, J. Schçnbohm, D. Bayles, J. Comput. Chem.
2001, 22, 545–559; i) F. Biegler-Kçnig, J. Schçnbohm, J. Comput.
Chem. 2002, 23, 1489–1494.
[11] J. Molina, J. A. Dobado, Theor. Chem. Acc. 2001, 105, 328–337.
[12] J. A. Dobado, H. Martinez-Garcia, J. Molina, M. R. Sundberg, J.
Am. Chem. Soc. 2000, 122, 1144–1149.
[13] a) M. Yamashita, Y. Yamamoto, K.-y. Akiba, D. Hashizume, F. Iwa-
saki, N. Takagi, S. Nagase, J. Am. Chem. Soc. 2005, 127, 4354–4371;
b) Y. Yamamoto, K.-y. Akiba, Yuki Gosei Kagaku Kyokaishi 2004,
62, 1128–1137.
Acknowledgements
This work was partially supported by a Grant-in-Aid for Scientific Re-
search (No. 16550038) from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan.
[1] a) J. C. Martin, M. M. Chau, J. Am. Chem. Soc. 1974, 96, 3319–3321;
b) S. Alvarez, F. Mota, J. Novoa, J. Am. Chem. Soc. 1987, 109,
6586–6591; c) W. B. Farnham, D. A. Dixon, J. C. Calabrese, J. Am.
Chem. Soc. 1988, 110, 8453–8461; d) W. Nakanishi, “Hypervalent
Chalcogen Compounds” in Handbook of Chalcogen Chemistry: New
Perspectives in Sulfur, Selenium and Tellurium (Ed.: F. A. Devillano-
va), Royal Society of Chemistry, Cambridge, Chapter 10.3, 2006, in
press.
[2] a) W. Nakanishi, S. Hayashi, S. Toyota, Chem. Commun. 1996, 371–
372; b) W. Nakanishi, S. Hayashi, S. Toyota, J. Org. Chem. 1998, 63,
8790–8800; c) W. Nakanishi, S. Hayashi, T. Arai, Chem. Commun.
2002, 2416–2417.
[3] a) W. Nakanishi, S. Hayashi, N. Itoh, Chem. Commun. 2003, 124–
125; b) W. Nakanishi, S. Hayashi, N. Itoh, J. Org. Chem. 2004, 69,
1676–1684; c) W. Nakanishi, S. Hayashi, T. Furuta, N. Itoh, Y. Nishi-
na, M. Yamashita, Y. Yamamoto, Phosphorus Sulfur Silicon Relat.
Elem. 2005, 180, 1351–1355.
[14] S. K. Ignatov, N. H. Rees, B. R. Tyrrell, S. R. Dubberley, A. G. Razu-
vaev, P. Mountford, G. I. Nikonov, Chem. Eur. J. 2004, 10, 4991–
4999.
[15] H. M. Muchall, ARKIVOC 2001, 7, 82–86.
[16] S. K. Tripathi, U. Patel, D. Roy, R. B. Sunoj, H. B. Singh, G. Wolmer-
shꢁuser, R. J. Butcher, J. Org. Chem. 2005, 70, 9237–9247.
[17] Structures of the naphthalene system 8-G-1-(ArSe)C10H6 are well
classified by type A (A), type B (B), and type C (C) structures, with
ꢁ
the Se CAr bond located almost perpendicular to the naphthyl plane
[4] W. Nakanishi, S. Hayashi, S. Yamaguchi, K. Tamao, Chem.
Commun. 2004, 140–141.
in A and in the naphthyl plane in B, whereas C is a structure inter-
mediate between A and B (see ref. [38] and also Scheme 2).
[18] A. Bondi, J. Phys. Chem. 1964, 68, 441–451.
[5] a) G. C. Pimentel, J. Chem. Phys. 1951, 19, 446–448; b) J. I. Musher,
Angew. Chem. 1969, 81, 68–83; Angew. Chem. Int. Ed. Engl. 1969,
8, 54–68; c) R. J. Hatch, R. E. Rundle, J. Am. Chem. Soc. 1951, 73,
4321–4324; d) R. E. Rundle, J. Am. Chem. Soc. 1963, 85, 112–113.
[6] a) M. M. L. Chen, R. Hoffmann, J. Am. Chem. Soc. 1976, 98, 1647–
1653; b) P. J. Hay, J. Am. Chem. Soc. 1977, 99, 1003–1012; c) W.
Kutzelnigg, Angew. Chem. 1984, 96, 262–286; Angew. Chem. Int.
Ed. Engl. 1984, 23, 272–295; d) A. E. Reed, F. Weinhold, J. Am.
Chem. Soc. 1986, 108, 3586–3593; e) A. E. Reed, P. von R. Schleyer,
J. Am. Chem. Soc. 1990, 112, 1434–1445; f) M. M. L. Chen, R. Hoff-
mann, J. Am. Chem. Soc. 1976, 98, 1647–1653; g) P. A. Cahill, C. E.
Dykstra, J. C. Martin, J. Am. Chem. Soc. 1985, 107, 6359–6362;
h) N. C. Baenziger, R. E. Buckles, R. J. Maner, T. D. Simpson, J.
Am. Chem. Soc. 1969, 91, 5749–5755.
[7] a) R. A. Hayes, J. C. Martin, “Sulfurane Chemistry” in Organic
Sulfur Chemistry: Theoretical and Experimental Advances (Eds.: F.
Bernardi, I. G. Csizmadia, A. Mangini), Elsevier, Amsterdam, 1985,
Chapter 8; b) J. Bergman, L. Engman, J. Siden, “Tetra- and Higher-
Valent (Hypervalent) Derivatives of Selenium and Tellurium” in
The Chemistry of Organic Selenium and Tellurium Compounds,
Vol. 1 (Eds.: S. Patai, Z. Rappoport), Wiley, New York, 1986, Chap-
ter 14; c) The Organic Chemistry of Tellurium (Ed.: K. J. Irgolic),
Gordon and Breach, New York, 1974.
[19] The nonbonded O···S distances in
2 (S-B) are 2.6495(11) and
ꢁ
ꢁ
ꢁ
ꢁ
2.6392(11) Š. The O(1B) S(1B) C
angles in 2 (S-B) are 178.49(5) and 171.98(6)8, respectively. The
G
G
ꢁ
ꢁ
S(1B) O(1B) S(2B) angle is 157.97(4)8.
[20] Gaussian 03, Revision B.05, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomer-
y, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyen-
gar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C.
Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cio-
slowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaro-
mi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.
Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wall-
ingford CT, 2004.
[8] Chemistry of Hypervalent Compounds (Ed.: K.-y. Akiba), Wiley-
VCH, New York, 1999.
[21] AIM2000 program (version 2.0) employed to analyze and visualize
atoms in molecules: F. W. Biegler-Kçnig, J. Schçnbohm, D. Bayles,
J. Comput. Chem. unpublished results.
[22] NBO (version 3.1), E. D. Glendening, A. E. Reed, J. E. Carpenter,
F. Weinhold, Theoretical Chemistry Institute, University of Wiscon-
sin, Madison, 2001.
[9] a) G. Mugesh, A. Panda, H. B. Singh, N. S. Punekar, R. J. Butcher,
Chem. Commun. 1998, 2227–2228; b) J. E. Drake, M. B. Hurst-
house, M. Kulcsar, M. E. Light, A. Silvestru, Phosphorus Sulfur Sili-
con 2001, 169, 293–296; c) G. Mugesh, A. Panda, H. B. Singh, N. S.
Punekar, R. J. Butcher, J. Am. Chem. Soc. 2001, 123, 839–850; d) S.
Tomoda, M. Iwaoka, J. Chem. Soc., Chem. Commun. 1990, 23 1–
233; e) J. E. Drake, M. B. Hursthouse, M. Kulcsar, M. E. Light, A.
Silvestru, J. Organomet. Chem. 2001, 623, 153–160; f) G. Mugesh,
A. Panda, S. Kumar, S. D. Apte, H. B. Singh, R. J. Butcher, Organo-
[23] The MP2 level with the same basis sets also gave similar results (see
Table 4).
[24] Contributions of p(C=O) character to 7 and 8 are also predicted to
N
ꢁ
be very small (l1/l2ꢁ1=0.07 for both). The ionic C+
nature of
ꢁ
O
Chem. Eur. J. 2007, 13, 255 – 268
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
267

W. Nakanishi et al.
the C=O bond must be very large, as the (Qn(C), Qn(O)) values are
(0.552, ꢁ0.565) for 7 and (0.551, ꢁ0.558) for 8.
[33] W. Nakanishi, S. Hayashi, D. Shimizu, M. Hada, Chem. Eur. J. 2006,
12, 3829–3846.
[34] H. Quast, H.-L. Fuchsbauer, Chem. Ber. 1986, 119, 2414–2429.
[35] A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C. Giaco-
vazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R. Spagna, J.
Appl. Crystallogr. 1999, 32, 115–119.
[25] The energies of the structures with C2v symmetry are slightly lower
than those with C2 symmetry for 1–3.
[26] Two factors may operate to determine the conformation of the
MeO group in the 1,8-positions of the anthracene 13. One is the
energy-lowering effect by CT in the O···B···O interaction: the np(O)
orbital must be more effective for CT, which requires the OMe
groups to adopt the AA conformation. Another factor is the p–p
[36] SHELXL-97, Program for the Refinement of Crystal Structures,
G. M. Sheldrick, University of Gçttingen, Gçttingen, 1997.
[37] Gaussian98 (RevisionA.9), M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski,
J. A. Montgomery, R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J.
Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli,
C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q.
Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari,
J. B. Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefa-
nov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts,
R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A.
Nanayakkara, C. Gonzalez, M. Challacombe, P. M. W. Gill, B. G.
Johnson, W. Chen, M. W. Wong, J. L. Andres, M. Head-Gordon,
E. S. Replogle, J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 1998.
[38] a) W. Nakanishi, S. Hayashi, T. Uehara, Eur. J. Org. Chem. 2001,
2001, 3933–3943; b) S. Hayashi, W. Nakanishi, J. Org. Chem. 1999,
64, 6688–6696; c) W. Nakanishi, S. Hayashi, H. Yamaguchi, Chem.
Lett. 1996, 947–948; d) W. Nakanishi, S. Hayashi, A. Sakaue, G.
Ono, Y. Kawada, J. Am. Chem. Soc. 1998, 120, 3635–3640; e) W.
Nakanishi, S. Hayashi, J. Org. Chem. 2002, 67, 38–48; f) W. Naka-
nishi, S. Hayashi, T. Uehara, J. Phys. Chem. A 1999, 103, 9906–9912.
conjugation of n(O)–p(ATC) type, which places the groups in the
G
ATC plane (the BB conformation). If the p–p conjugation contrib-
utes more than CT, the OMe groups will adopt the BB conforma-
tion. The BB structure of 13 shows that the p–p conjugation does
indeed contribute more than CT to 13, although the crystal-packing
effect must also be considered.
ꢁ3
[27] The 1b(rc) value was reported to be 0.022 eao for [9-(MeO)2C-1,8-
(MeO)2C14H7]+ (see ref. [13a]).
[28] a) E. Espinosa, E. Molins, C. Lecomte. Chem. Phys. Lett. 1998, 285,
170–173; b) E. Espinosa, M. Souhassou, H. Lachekar, C. Lecomte,
Acta Crystallogr., Sect. B 1999, 55, 563–572; c) E. Espinosa, C. Le-
comte, E. Molins, Chem. Phys. Lett. 1999, 300, 745–748; d) E. Espi-
nosa, I. Alkorta, I. Rozas, J. Elguero, E. Molins, Chem. Phys. Lett.
2001, 336, 457–461; e) C, Gatti, L. Bertini, Acta Crystallogr. Sect.
A 2004, 60, 438–449.
[29] The reasons for the variation in values of Hb(rc) of the hydrogen-
bonded and van der Waals adducts, as well as g(O), in the plots in
Figure 6 are of interest. Studies are in progress and will be discussed
elsewhere.
[30] The 5c–6e interactions in 1, 2, 4, and 5 are well demonstrated based
on the molecular orbitals, although not shown (cf. Scheme 1). Mol-
Studio R3.2, Rev. 1.0, NEC Corporation, 1997–2003.
[31] DE(I) and DE(II) are ꢁ60.6 and ꢁ36.5 kJmolꢁ1
, respectively
Received: April 4, 2006
Revised: July 25, 2006
Published online: October 26, 2006
(DE(II)/DE(I)=0.60) (see ref. [3]). The values are larger than DE(1)
and DE(4), respectively, although the basis sets for the calculations
are not the same.
[32] The structure of III was determined by means of X-ray crystallo-
graphic analysis: W. Nakanishi S. Hayashi, unpublished results.
Please note: Minor changes have been made to this manuscript since its
publication in Chemistry—A European Journal Early View. The Editor.
268
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 255 – 268