Abstract
The observation of homolytic SCH 3 bond cleavage in (Ph 2P( o-C 6H 4)SCH 3) 2Ni 0 under photochemical conditions has prompted further investigation of nickel(0) complexes and their stability. Tetradentate P 2S′ 2 donor ligands (S′ = thioether type S donor) with aromatic rings incorporated into the P to S links, Ph 2P( o-C 6H 4)S(CH 2) 3S( o-C 6H 4)PPh 2 (arom-PSSP), or the S to S links, Ph 2P(CH 2) 2SCH 2( o-C 6H 4)CH 2S(CH 2) 2PPh 2 (PS-xy-SP), have been used to form four-coordinate, square planar nickel(II) complexes, [(arom-PSSP)Ni](BF 4) 2 ( 2) and [(PS-xy-SP)Ni](BF 4) 2 ( 3). The bidentate and tetradentate ligands, Ph 2P( o-C 6H 4)SCH 2CH 3 (arom-PSEt) and Ph 2P(CH 2) 2S(CH 2) 3S(CH 2) 2PPh 2 (PSSP), give similar complexes, [(arom-PSEt) 2Ni](BF 4) 2 ( 1) and [(PSSP)Ni](BF 4) 2 ( 4), respectively. Cyclic voltammograms of the Ni 11 complexes in CH 3CN show two reversible redox events assigned to Ni 11 1 and Ni 1 0 . The one-electron reduction product produced by stoichiometric amounts of Cp 2Co can be characterized by EPR. At 100 K rhombic signals show hyperfine coupling to two phosphorus atoms. Complete bulk chemical reduction of complexes 1, 2, 3 and 4 with Na/Hg amalgam provided the corresponding nickel(0) complexes 1 R, 2 R, 3 R and 4 R which were isolated as red solutions or solids characterized by magnetic resonance properties and reaction products. Photolysis of these nickel(0) complexes leads to S-dealkylation to produce alkyl radicals and dithiolate nickel(II) complexes. Complex 3 crystallized in the monoclinic space group P 2 t / c with a=20.740(5), b=9.879(3), c=17.801(4) a ̊ A , ß=92.59(2)°, V=3644(2) A ̊ 3 and Z=4 ; complex 4: P2 1/c with a=13.815(4), b=13.815(4), c=15.457(5) a ̊ A , V=3365.4(14) Å 3 and Z=4.
Published Version
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