Molybdenum and tungsten mono-isodiazene complexes with alkyl ligands as ring-opening metathesis polymerisation procatalysts.: Crystal and molecular structures of [Mo(CH2CMe2Ph)3(NNPh2)(OC6F5)], [W(CH2SiMe3)3(NNPh2)(OC6F5)] and [WCl2(NNPh2)(OC6F5)2(thf)]

Reaction of [M(NNPh2)Cl-4] with RMgCl followed by addition of pentafluorophenol afforded the tris-alkyl complexes [MoR3(NNPh2)(OC6F5)] [M = Mo, R = CH2CMe2Ph 1; M = W, R = CH2SiMe3 2] in moderate yields. At ca. 80 degrees C in chlorobenzene 1 and 2 are active for the ring-opening metathesis polymerisation of norbornene; intermediate alkylidene complexes are not observed. The crystal structures of 1 and 2 have been determined; the metal centres adopt trigonal bipyramidal geometries in which the isodiazene and pentafluorophenoxide groups are apical. The crystal structure of [WCl2(NNPh2)(OC6F5)(2)(thf)] 3 is also reported.