ic961265a_si_001.cif (24.51 kB)
Download fileH+/AuPPh3+ Exchange for the Hydride Complexes CpMoH(CO)2(L) (L = PMe3, PPh3, CO). Formation and Structure of [Cp(CO)2(PMe3)Mo(AuPPh3)2]+[BF4]-
dataset
posted on 1997-07-02, 00:00 authored by Rossana Galassi, Rinaldo Poli, E. Alessandra Quadrelli, James C. FettingerThe reaction of CpMoH(CO)2L with
AuPPh3+BF4- in
THF at −40 °C proceeds directly to the MoAu2
cluster
compounds
[CpMo(CO)2L(AuPPh3)2]+BF4-
(L = PMe3 (1), PPh3
(2)) with release of protons. A 1:1
reaction
leaves 50% of the starting hydride unreacted. At lower
temperature, however, the formation of a
[CpMo(CO)2(PMe3)(μ-H)(AuPPh3)]+
intermediate is observed. This compound evolves to the cation of
1 and CpMoH(CO)2(PMe3) upon warming and is deprotonated by 2,6-lutidine to
afford
CpMo(CO)2(PMe3)(AuPPh3).
The X-ray
structure of 1 can be described as a four-legged piano stool
with the PMe3 and the
“η2-(AuPPh3)2” ligands
occupying
relative trans positions.
[Cp(CO)2(PMe3)Mo(AuPPh3)2]+[BF4]-
(Mr = 1298.41): monoclinic, space group
P21/n, a = 18.1457(13) Å, b =
9.7811(7) Å, c = 26.096(2) Å, β =
105.086(5)°, V = 4472.0(5) Å3,
Z = 4. The
reaction of CpMoH(CO)2(PMe3) with 3
equiv of AuPPh3+ affords a MoAu3
cluster,
[CpMo(CO)2(PMe3)(AuPPh3)3]2+ (3), in
good yields under kinetically controlled conditions. Under
thermodynamically controlled
conditions, 3 dissociates extensively into 1 and
free AuPPh3+. It is proposed that the
hydride ligand helps build
higher nuclearity Mo−Au clusters. The difference in reaction
pathways for the interaction of AuPPh3+
with
CpMoH(CO)2L when L = PR3 or CO and for
the interaction of CpMoH(CO)2(PMe3)
with E+ when E = H, Ph3C
or AuPPh3 is discussed. The lower acidity and greater
aurophilicity of the
[CpMo(CO)2L(μ-H)(AuPPh3)]+
intermediate when L = PMe3 favor attack by
AuPPh3+ before deprotonation.