X!ray crystal structures
3198
atoms were theoretically added to the adjacent O hinders m!S atom to form further superamolecular
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atoms "O2ÐH2B and O3ÐH7A distances are 9[74 A\ interaction ð03Ł\ so the two molecules of III are packed
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O6ÐH2B and O3ÐH7A are 0[73 A#\ according to the into the cell with a symmetric center ð13Ł[ Similarly\
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distance "1[58 A# of both O2ÐO6 and O3ÐO7\ we can six SÐS interactions are found in IV[ S0\ as well as S5\
deduce that the two H atoms H2B and H7A are can form two SÐS interactions with another two S
roughly linear and situated in the same plane with the atoms[
four O atoms and strong H!bonds are formed[ The
IR spectra for clusters III and IV were measured ð19Ł
20P NMR
as listed in Table 4[ A broad absorption at 2199 cm−0
was assigned to nOH for compound III and a sharp
20P NMR spectra of III and IV\ "Fig[ 4#\ were mea!
absorption at 1867 cm−0\ which overlaps with the phe!
sured in acetone!d5[ The assignment of the 20P res!
nyl absorption\ was assigned to the nOH for IV[ This is
onances is consistent with the literature ð2Ł[ The
consistent with the crystal structural results that the
resonance "T0# at 009[97 ppm for III was assigned to
the two coalesced DTP ligands coordinated to Mo1
and Mo2\ respectively^ the other resonance "T1# at
H!bond in IV is linear and much stronger than that
in III[ The dihedral angles calculated between the two
phenyl planes "plane 1 and 3# is 81[9"1#> as shown in
000[22 ppm was assigned to the DTP coordinated to
Table 3\ indicate that the two phenyl planes are aligned
Mo0[ Similarly\ the resonance "T0# at 009[71 ppm in
perpendicularly in the lattice[
The mean MoÐO bond length 1[131"4# A "to phthal!
IV was assigned to the four DTP ligands coordinated
to Mo1 and Mo2\ Mo3 and Mo5^ the other resonance
"T1# at 009[19 ppm was assigned to the DTP ligand
coordinated to Mo0\ Mo4[
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ate ligands# in IV is longer than that of the similar
aliphatic carboxylate cluster compounds ð08Ł and
these four MoÐO bonds\ listed in Table 2\ di}er con!
siderably from each other[ This di}erence is even gre!
ater than that of the corresponding MoÐO in cluster
III as shown in Table 1[ This distortion of the coor!
dinated ÐCOO groups is caused by crystalline packing
e}ects[ The alignment of the bulky Mo2S3 core and
the neighboring DTP ligand distort Mo1Mo2O0C6O1
and Mo3Mo5O5CO6O4 planes and also twist the H!
bonding plane as shown by the following data]
O3O7O2 013[4"7#>¼O6OO7O7 013[5"8#>\ C7ÐO2
Experimentally\ the loosely coordinated ligand L
a}ects the NMR spectrum by its dynamic dissociation
in the solution and the carboxylate does so by the
long!distance electron delocalization[ Normally\ the
pyridine substitution for acetonitrile will broaden
NMR linewidths considerably ð2Ł\ so signi_cant line!
broadening in the spectra of compound IV is expected[
For this series of trinuclear clusters\ the relative
position of T0 and T1 is determined by the type of
the loosely coordinated ligand L[ For compound III\
LꢀCH2CN\ T1 is situated at the lower _eld to T0^ on
the contrary\ T1 is situated at the higher _eld in the
spectra of compound IV\ Lꢀpyridine[ Nevertheless\
L can only a}ect the chemical shift of T1 considerably\
it does little to the chemical shift of T0\ so the chemical
shift di}erences between T0 and T1 are mainly attri!
buted to aromatic substituents ÐOH and ÐCO1H[ This
leads to the conclusion that the Mo2S3 core and the
superconjugation translate the electron e}ect to DTP
ligands ð14Ł[ A more systematic 20P NMR spec!
troscopic study on more cluster compounds will soon
follow[
Ä
Ä
Ä
"0[161"09# A#¼C97ÐO7 "0[156"00# A# and C7ÐO3
Ä
"0[143"09# A#¼C97ÐO6 "0[142"09# A#[ As re~ected by
the dihedral angles between plane 0 and 1\ 2 and 3
"Table 3#\ the RCO1 group is no longer coplanar as
opposed to the case in cluster III[
SÐS interactions
The intramolecular SÐS interactions ð10\ 11Ł in
ðMo2S3Ł!type "MꢀMo\ W# clusters are important in
crystal packing along with the ligand substitutional
e}ect discussed above[ For both III and IV\ SÐS inter!
actions\ which are all considerably shorter than the
corresponding van der Waals contacts ð11\ 12Ł\ were
calculated as shown in Fig[ 3 and were listed in Table
5[ In cluster III\ the SÐS interactions favor the opposite
alignment of the two molecules in the cell[ On the
Acknowled`ments*We are grateful for the _nancial support
to the Foundation of the Chinese National Natural Sciences
"No[ 18292914#\ the Foundation of Fujian Provincial Natu!
ral Sciences "No[ 869022# and the Foundation of the Chinese
other side of the molecule\ the phenyl ring sterically State Key Laboratory of Structural Chemistry "No[ 869984#[
Table 4[ IR vibration of complexes III and IV "cm−0
#
NnMoÐ"m2−S#
nMoÐ"m!S#
nMoÐ"m!O#
n"OÐH#
n"CÐO#
nC5H5
III
IV
IR
IR
341
340
379
371
530
531
2199
1867
0058
0048
2999Ð2929
2999Ð2949
Wu, Ling
