作者:Surajit Chattopadhyay、Chittaranjan Sinha、Partha Basu、Animesh Chakravorty
DOI:10.1021/om00050a053
日期:1991.4
The first platinum(IV) cyclometalates of azobenzene, Pt(IV)(RL)Cl3 (R = H, Me), have been synthesized by oxidation of Pt(II)(RL)Cl by chlorine or m-chloroperbenzoic acid (Pt(RL) = cycloplatinated 2-(methylthio)azobenzene fragment). The X-ray structures of Pt(MeL)Cl3 and Pt(MeL)Cl are reported. In both cases the organic moiety acts as a planar tridentate (C,N,S) ligand and the lattice consists of loose dimers held by nonbonded S...S interactions. The Pt-C distances are equal in the two molecules, but the other metal-ligand distances are longer (e.g., Pt-S by approximately 0.09 angstrom) in Pt(MeL)Cl3. Weakening of back-bonding upon metal oxidation may be one of the reasons. In H-1 NMR spectra, the 3J coupling constant between Pt-196 and H-1(SMe) increases from 12.3 Hz in Pt(MeL)Cl3 to 20.1 Hz in Pt(MeL)Cl, in accord with the increase in 6s character of the metal hybrid orbitals. The complexes Pt(MeL)Cl and Pd(MeL)Cl are isomorphous, with very similar bond parameters. However, chlorine and mCPBA, which oxidize the metal in Pt(RL)Cl, attack the Pd-C bond (in effect the coordinated ligand is attacked) in Pd(RL)Cl, leaving the metal oxidation state unchanged. The reactivity difference corresponds to the nucleophilicity orders Pt(II) >> Pd(II) and Pd-C >> Pt-C. Crystal data for Pt(MeL)Cl3: space group P2(1)/n; a = 7.436 (2) angstrom, b = 18.613 (4) angstrom, c = 12.335 (2) angstrom, beta = 104.66 (2)-degrees; Z = 4, V = 1651.6 (6) angstrom3. Crystal data for Pt(MeL)Cl: space group P1BAR; a = 7.421 (5) angstrom, b = 8.830 (5) angstrom; c = 11.083 (6) angstrom, alpha = 105.44 (4)-degrees, beta = 92.05 (5)-degrees, gamma = 97.16 (5)-degrees; Z = 2, V = 692.7 (7) angstrom3. Crystal data for Pd(MeL)Cl: space group P1BAR; a = 7.424 (3) angstrom, b = 8.833 (4) angstrom, c = 11.127 (4) angstrom, alpha = 105.44 (3)-degrees, beta = 93.26 (3)-degrees, gamma = 96.81 (3)-degrees; Z = 2, V = 695.4 (5) angstrom3.