Bis(isodiazene) and related complexes of molybdenum(VI). Syntheses and structures of [Mo(OTf)(2)(NNPh2)(2)(py)(2)], [MoCl(OTf)(NNPh2){NC5H3(CH2C(O)Ph-2)(2)-2,6}], [{MoCl(NNPh2)(2)(mu-Cl)(NH2But)}(2)] and [MoTp ' Cl(NNPh2)(2)] [OTf = O3SCF3, Tp ' = tris(3,5-dimethylpyrazolyl)hydroborate]

Possible routes to [Mo(NNPh2)(2)R-2], where R = alkyl or aryl groups, have been investigated including the interaction of [MoCl2(NNPh2)(2)(dme)] 1 (dm e = 1,2-dimethoxyethane) with the standard alkylating agents LiR, RMgX, R2M g or R2Zn under various conditions of solvent and temperature. There was, h owever, no evidence to suggest alkylation had taken place. Treatment of 1 w ith two equivalents of silver trifluoromethanesulfonate, silver triflate (A gOTf), in the presence of pyridine gave the golden-yellow bis(triflate) com plex [Mo(OTf)(2)(NNPh2)(2)(py)(2)] 2 in good yield. In the presence of an e xcess of bipy (2,2'-bipyridine) the known dicationic species [Mo(NNPh2)(2)( bipy)(2)](2+) was isolated as its PF6- salt. Attempts to replace triflate b y alkyl groups in 2 were unsuccessful. A similar reaction of 1 with silver triflate in the presence of the bulky tridentate alkoxide 2,6-bis(2-hydroxy -2,2-diphenylethyl)pyridine (H2L) led to loss of an NNPh2 group (presumably as hydrazine) and formation of the green mono-isodiazene complex [MoCl(OTf )(NNPh2)(L)] 3. The compound [Mo(CH2CMe2Ph)(2)(NBut)(2)] underwent partial imido ligand exchange with an excess of 1,1-diphenylhydrazine hydrochloride to give the brown bis(isodiazene) chloro-bridged dimer [{MoCl(NNPh2)(2)(mu -Cl)(NH2But)}(2)] 4. A chloride substitution reaction of 1 with potassium t ris(3,5-dimethylpyrazolyl)hydroborate, (KTp') afforded the bis(isodiazene) complex [MoTp'Cl(NNPh2)(2)] 5. The crystal and molecular structures of 2-5 have been determined. The complexes all contain linear isodiazene groups wi th Mo-N distances in the range 1.755(6) to 1.768(7) Angstrom. In 2 the moly bdenum(VI) centre has a pseudo octahedral geometry with axial pyridines and cis-triflate groups. In six-co-ordinate 3 the pyridinediolate ligand has a meridional donor atom arrangement with an equatorial isodiazene ligand. Th e binuclear compound 4 has slightly asymmetric chloro bridges coplanar with the terminal isodiazene ligands. Complex 5 is octahedral, having a faciall y co-ordinated Tp' ligand and linear NNPh2 ligands.