Synthesis and structural characterisation of [Mo(NNPh2)(NPh2)(mesityl)(2)(OC6F5)] and {[W(NNPh2)(NPh2)(OSiMe3)](2)(mu-Cl)(2)(mu-O)}: isodiazene complexes with bulky amide groups arising via N-N bond cleavage

Reaction of [Mo(NNPh2)Cl-3] with mesitylMgCl (mesityl = 2,4,6-Me3C6H2) foll owed by addition of pentafluorophenol affords the bis(alkylated) complex [M o(NNPh2)(NPh2)(mesityl)(2)(OC6F5)] (1) in poor yield (20-30%). In the case of [WO2Cl2(dme)], reaction with Ph2NNH2. HCl in refluxing triethylamine/tri methylsilylchloride affords the binuclear complex {[W(NNPh2)(NPh2)(OSiMe3)] (2)(mu -Cl)(2)(mu -O)} (2) in good yield (approximately 75%). The crystal s tructures of 1 and 2 have been determined. In 1, the trigonal-bipyramidal M o atom is coordinated by an axial linear isodiazene group trans to a pentaf luorophenoxide ligand, whilst equatorial positions are occupied by two mesi tyl groups and an amide (NPh2) group. For 2, the molecule is best described as possessing a triply bridging (2x mu -Cl, mu -O) confacial bioctahedral geometry, with the longer bridging bonds trans to the isodiazene group The amide groups (NPh2) in each structure must arise through N-N bond cleavage. (C) 2001 Elsevier Science B.V. All rights reserved.