The molecular structure of a nickel(0) complex with P,S-donor
atom ligands has been characterized by
X-ray crystallography. Complex 1,
(Ph2P(o-C6H4)SCH3)2Ni0,
prepared by Na/Hg amalgam reduction of the
NiII
complex
[(Ph2P(o-C6H4)SCH3)2Ni](BF4)2
([2](BF4)2), degrades
photochemically with loss of CH3 radicals to
yield
complex 3,
(Ph2P(o-C6H4)S)2NiII.
Crystallographic parameters for the three compounds are as
follows: 1, monoclinic
space group C2/c with a =
11.467(2) Å, b = 17.613(3) Å, c =
15.733(2) Å, β = 96.450(10)°, V =
3157.5(9) Å3,
and Z = 4;
[2](BF4)2, monoclinic space
group P2
1
/
c
with a = 9.417(4) Å, b = 14.822(9)
Å, c = 13.773(2) Å, β =
98.55(3)°, V = 9101(14) Å3, and
Z = 2; and 3, monoclinic space group
P21/c with a =
9.651(2) Å, b = 12.971(8)
Å, c = 12.540(2) Å, β = 110.46(2)°,
V = 1470.7(11) Å3, and Z =
2. While complex 1 has a distorted
tetrahedral
geometry, complexes [2](BF4)2
and 3 are square planar with trans
stereochemistry. The cyclic voltammogram of
[2](BF4)2 in
CH3CN shows two redox events assigned to
NiII/I and NiI/0, whereas the thiolate
3 reveals only one
reversible wave assigned to NiII/III. The chemical
reduction of [2](BF4)2 with
Cp2Co provided a NiI species,
[(Ph2P(o-C6H4)SCH3)2NiI]+,
characterized at 100 K by an axial EPR signal with
g
x
=
g
y
= 2.10 and
g
z
= 1.96.
Hyperfine
spectral features resulting from coupling to two 31P nuclei
suggests a retention of substantially square planar
geometry.
In contrast the isotropic character of the EPR signal of
[(Ph2P(o-C6H4)SCH3)(Ph2P(o-C6H4)S)NiI],
presumed to be
the first product of the photochemical demethylation of 1
ultimately yielding the doubly demethylated complex
3,
suggested the intervening thioether/thiolate NiI species to
be pseudotetrahedral. Protonation of the nickel(0)
species
1 produced a five-coordinate nickel hydride complex,
[(H)(arom-PSMe)2Ni]BF4,
4.