The syntheses of mononuclear complexes
cis-MoVOXL (X = Cl, Br, OMe, OEt, OPh,
SPh, NCS, OSiMe3) and
two binuclear complexes
MoV
2O3L2 of the title
ligand LH2 are reported. Two forms of MoOClL, with
cis oxo
and chloro ligands, were crystallized, one in space group
P21/n, with a =
10.440(2) Å, b = 14.260(2) Å, c
=
12.041(2) Å, β = 102.76(2)°, V =
1748(1) Å3, and Z = 4, and the other in
P21/c, with a =
13.564(4) Å, b =
7.172(2) Å, c = 18.242(6) Å, β =
95.19(1)°, V = 1767(2) Å3, and
Z = 4. MoO(OSiMe3)L crystallizes in
space
group P21/c, with a =
15.923(3) Å, b = 11.141(2) Å, c =
14.186(2) Å, β = 112.64(2)°, V =
2323(1) Å3, and
Z = 4, while MoO(NCS)L crystallizes in
Pna21, with a = 22.471(2) Å,
b = 12.136(2) Å, c = 7.138(1)
Å, V =
1947(1) Å3, and Z = 4. The four
structures reveal two possible conformations for ligand L: one with
trans S
atoms (cis,trans-MoOClL and
-MoO(OSiMe3)L) and one with cis S atoms
(cis,cis-MoOClL and -MoO(NCS)L).
The cis,cis isomers are converted to the
cis,trans forms under reflux in MeCN at 80 °C.
Only the cis,trans forms
could be isolated for bulkier ligands X (OPh, SPh, OSiMe3).
A short H3C···X interaction is present in the
cis,cis
forms: C···Cl = 3.07 Å and C···N = 2.93 Å, for
X = Cl and NCS, respectively. Infrared and electronic
spectral
data provide unambiguous identification of the stereochemistry of
ligand L in mononuclear complexes MoOXL.
Effective removal of ligand X = OR from
cis,cis-MoO(OR)L (R = Me, Et) led to two
binuclear complexes
(MoVOL)2(μ-O) of
C
i
and C
1
point symmetries.
C
i
-(MoOL)2(μ-O)·thf
crystallizes in space group P21/c,
with a
= 8.5650(5) Å, b = 15.1862(9) Å,
c = 16.8038(9) Å, β = 100.183(1)°,
V = 2157.1(8) Å3, and Z = 2,
while
C
1-(MoOL)2(μ-O)·CH2Cl2
crystallizes in space group P21/c,
with a = 12.5250(5) Å, b =
24.673(1) Å, c =
12.7253(6) Å, β = 108.070(4)°, V =
3738.6(3) Å3, and Z = 4.
C
i
-(MoOL)2(μ-O)·thf
features two cis,trans-MoVOXL centers with X = μ-O, while
C
1-(MoOL)2(μ-O)·CH2Cl2
contains a cis,trans and a cis,cis
center. In the
latter, the Mo−O−Mo link is asymmetric, allowing relief of steric
crowding on the cis,cis side of the
molecule.
