Complexes of the platinum metals. Part 22 [1]. Synthesis and molecular dynamics of 1,3-diaryltriazenido derivatives

Abstract

1,3-Diaryltriazenes, ArN = NNHAr (Ar = Ph, p-MeC 6H 4 and p-MeOC 6H 4) react with platinum metal halide complexes in the presence of triethylamine to afford products containing mono- or bi-dentate (chelate or bridging) 1,3-diaryltriazenide ligands. Complexes prepared in this manner include derivatives of ruthenium(II), ▪ 2(PPh 3) 2] and ▪(CO)(PPh 3) 2]; rhodium(I), ▪ 2], ▪(C 8H 12)(PPh 3)] and ▪(CO)(PPh 3) 2]; palladium(II) ▪L 2] (X = Cl, L = PPh 3, PEt 3, AsPh 3, PMePh 2; X = Br, L = PMePh 2; X = I, L = PMe 2Ph), and ▪ 2(PMe 2Ph) 2]; and platinum(II(, [PtCl ▪L 2] (L = PPh 3, PEt 3, and PEt 2Ph; L = C 8H 12). The intramolecular N(1)–N(3) exchange process: ▪ displayed by the monodentate 1,3-diaryltriazenido derivatives of rhodium(I), palladium(II) and platinum(II) have been studied by dynamic proton NMR spectroscopy, and thermodynamic parameters of activation have been determined. ΔH ≠ values were found to lie within the range ca. 32–44 kJ mol −1 for the palladium(II) and platinum(II) complexes, ΔS ≠ values are all negative.