Characteristics of nickel(0), nickel(I), and nickel(II) in phosphino thioether complexes: Molecular structure and S-dealkylation of (Ph(2)P(o-C6H4)SCH3)(2)Ni-0
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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. Cristallographic parameters for the three compounds are as follows: 1, monoclinic space group C2/c with a = 11.467(2) , b = 17.613(3) , c = 15.733(2) , = 96.450(10), V= 3157.5(9) 3, and Z = 4; [2](BF4)2, monoclinic space group P21/c with a = 9.417(4) , b = 14.822(9) , c = 13.773(2) , = 98.55(3), V = 9101(14) 3, and Z = 2; and 3, monoclinic space group P21/c with a = 9.651(2) , b = 12.971(8) , c= 12.540(2) , = 110.46(2), V = 1470.7(11) 3, 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, [(Ph2(o-C6H4)SCH3) 2NiI]+, characterized at 100 K by an axial EPR signal with gx, = gy = 2.10 and gz= 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)(Ph 2P(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.
