摘要
The stable mononuclear Ni(III)-thiolate complexes [Ni III (L) (P(C 6 H 3 -3-SiMe 3 -2-S) 3 )] - (L = SePh (2), Cl (3), SEt (4), 2-S-C 4 H 3 S (5), CH 2 CN (7)) were isolated and characterized by UV-vis, EPR, IR, SQUID, CV, 1 H NMR, and single-crystal X-ray diffraction. The increased basicity (electronic density) of the nickel center of complexes [Ni III (L)-(P(C 6 H 3 -3-SiMe 3 -2-S) 3 )] - modulated by the monodentate ligand L and the substituted groups of the phenylthiolate rings promotes the stability and reactivity. In contrast to the irreversible reduction at -1.17 V (vs Cp 2 Fe/Cp 2 Fe + ) for complex 3, the cyclic voltammograms of complexes [Ni III (SePh)(P(o-C 6 H 4 S) 3 )] - , 2, 4, and 7 display reversible Ni III/II redox processes with E 1/2 = -1.20, -1.26, -1.32, and -1.34 V (vs Cp 2 Fe/Cp 2 Fe + ), respectively. Compared to complex 2 containing a phenylselenolate-coordinated ligand, complex 4 with a stronger electron-donating ethylthiolate coordinated to the Ni(III) promotes dechlorination of CH 2 Cl 2 to yield complex 3 (k obs = (6.01 ± 0.03) × 10 -4 s -1 for conversion of complex 4 into 3 vs k obs = (4.78 ± 0.02) × 10 -5 s -1 for conversion of complex 2 into 3). Interestingly, addition of CH 3 CN into complex 3 in the presence of sodium hydride yielded the stable Ni(III)-cyanomethanide complex 7 with a Ni III -CH 2 CN bond distance of 2.037(3) Å. The Ni III -SEt bond length of 2.273(1) A in complex 4 is at the upper end of the 2.12-2.28 Å range for the Ni III -S bond lengths of the oxidized-form [NiFe] hydrogenases. In contrast to the inertness of complexes 3 and 7 under CO atmosphere, carbon monoxide triggers the reductive elimination of the monodentate chalcogenolate ligand of complexes 2, 4, and 5 to produce the trigonal bipyramidal complex [Ni II (CO)(P(C 6 H 3 -3-SiMe 3 -2-S) 3 )]- (6). © 2006 American Chemical Society.