| Abstract
| - The molecular structure of a nickel(0) complex with P,S-donoratom ligands has been characterized byX-ray crystallography. Complex 1,(Ph2P(o-C6H4)SCH3)2Ni0,prepared by Na/Hg amalgam reduction of theNiIIcomplex[(Ph2P(o-C6H4)SCH3)2Ni](BF4)2([2](BF4)2), degradesphotochemically with loss of CH3 radicals toyieldcomplex 3,(Ph2P(o-C6H4)S)2NiII.Crystallographic parameters for the three compounds are asfollows: 1, monoclinicspace 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 spacegroup P21/cwith a = 9.417(4) Å, b = 14.822(9)Å, c = 13.773(2) Å, β =98.55(3)°, V = 9101(14) Å3, andZ = 2; and 3, monoclinic space groupP21/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 distortedtetrahedralgeometry, complexes [2](BF4)2and 3 are square planar with transstereochemistry. The cyclic voltammogram of[2](BF4)2 inCH3CN shows two redox events assigned toNiII/I and NiI/0, whereas the thiolate3 reveals only onereversible wave assigned to NiII/III. The chemicalreduction of [2](BF4)2 withCp2Co provided a NiI species,[(Ph2P(o-C6H4)SCH3)2NiI]+,characterized at 100 K by an axial EPR signal withgx =gy = 2.10 andgz= 1.96.Hyperfinespectral features resulting from coupling to two 31P nucleisuggests a retention of substantially square planargeometry.In contrast the isotropic character of the EPR signal of[(Ph2P(o-C6H4)SCH3)(Ph2P(o-C6H4)S)NiI],presumed to bethe first product of the photochemical demethylation of 1ultimately yielding the doubly demethylated complex3,suggested the intervening thioether/thiolate NiI species tobe pseudotetrahedral. Protonation of the nickel(0)species1 produced a five-coordinate nickel hydride complex,[(H)(arom-PSMe)2Ni]BF4,4.
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