Preparation and reactivity with azo-species of hydride and dihydrogen complexes of osmium stabilised by tris(pyrazolyl)borate and phosphite ligands

摘要

Mixed-ligand OsCl(Tp)L(PPh3) complexes 1 [Tp = hydridotris(pyrazolyl)borate; L = P(OMe)(3), P(OEt)(3) and PPh(OEt)(2)] were prepared by allowing OsCl(Tp)(PPh3)(2) to react with an excess of phosphite. Treatment of chlorocomplexes 1 with NaBH4 in ethanol afforded hydride OsH(Tp)L(PPh3) derivatives 2. Stable dihydrogen [Os(eta(2)-H-2)(Tp)L(PPh3)]BPh4 derivatives 3 were prepared by protonation of hydrides 2 with HBF4.Et2O at -80 degrees C. The presence of the eta(2)-H-2 ligand is supported by short T-1 (min) values and J(HD) measurements on the partially deuterated derivatives. Treatment of the hydride OsH(Tp)[P(OEt)3](PPh3) complex with the aryidiazonium salt [4-CH3C6H4N2]BF4 afforded aryldiazene [Os(4-CH3C6H4N = NH)(Tp){P(OEt)(3)](PPh3)]BPh4 derivative 4. Instead, aryldiazenido [Os(4-CH3C6H4N2)(Tp)[P(OEt)(3)](PPh3)](BF4)(2) derivative 5 was obtained by reacting the hydride OsH(Tp)[P(OEt)3](PPh3) first with methyltriffate and then with aryldiazonium [4-CH3C6H4N2]BF4 salt. Spectroscopic characterisation (IR, N-15 NMR) by the N-15-labelled derivative strongly supports the presence of a near-linear Os-N N-Ar aryldiazenido group. Imine [Os{eta(1)-NH=CH)Ar}(Tp) P(OEt)(3)}(PPh3)]BPh4 complexes 6 and 7 (Ar = C6H5, 4-CH3C6H4) were also prepared by allowing the hydride OsH(Tp)[P(OEt)(3)](PPh3) to react first with methyltriflate and then with alkylazides. (c) 2007 Elsevier B.V. All rights reserved.