Preparation and Characterization of Bis[(μ-acetato)halo(μ-bis(diphenylphosphino)amine)molybdenum(II)] Complexes

Molecules of the formula
Mo2X2(OAc)2(μ-dppa)2
(X = Cl (2), Br (3), I (4); dppa =
bis(diphenylphosphino)amine; OAc = CH3COO-) can be
synthesized by the reaction of Mo2(OAc)4
(1) with dppa and (CH3)3SiX.
All
three compounds were characterized by IR and UV−visible spectroscopy,
mass spectrometry, and 31P{1H}
NMR
spectroscopy. Single-crystal diffraction studies yield the
following pertinent crystal data:  for
2·2EtOH,
orthorhombic Pbca (No. 61), a = 16.830(2)
Å, b = 20.310(4) Å, c = 16.751(2)
Å,V = 5726(2) Å3, Z = 4;
for
3·2(toluene), monoclinic C2/c
(No. 15), a = 22.481(2) Å, b =
19.151(9) Å, c = 14.358(2) Å, β =
95.19(2)°, V
= 6156(3) Å3, Z = 4; for
4·EtOH·CH3CN, monoclinic
P21/c (No. 14), a =
20.607(9)Å, b = 16.020(3) Å, c
=
17.189(5) Å, β = 95.81(2)°, V = 5645(3)
Å3, Z = 4. The Mo−Mo distances for
compounds 2−4 are 2.158(1),
2.176(1), and 2.164(1) Å, respectively. Both
crystallographic data and physical measurements indicate that
2
and 3 have nearly identical Mo−X bond distances while
those in 3 and 4 differ more significantly; the
spectroscopic
data bear this out. The Mo−O and Mo−P distances are very
similar in all three of the complexes reported.