THE CLEAVAGE OF THE N-N BOND OF N,N-DISUBSTITUTED HYDRAZINES ON RHENIUM - THE PREPARATION, REACTIONS AND X-RAY CRYSTAL-STRUCTURES OF [RECL2(NH3)(NNCOC6H4-4-R)(PPH3)2] (R = H, -OME, -NO2), [RECL3(NNPH2)(PPH3)2], [RECL2(N)(NNPH2)(PPH3)] AND [RECL(N)(ME2CNNCOPH)(PPH3)2]

Reaction of the N,O-chelated complexes [ReCl2(N2COC6H4-4-R)(PPh3)2] (R = H, Me, NO2) with N,N- and certain N-substituted hydrazines gave the ammine complexes [ReCl2(NH3)(NNCOC6H4-4-R)(PPh3)2] [R = H (1), R = Me (2), R = NO2 (3)]. The mechanism is believed to involve intermolecular homolytic cleavage of the N-N bond. The X-ray structure of 1 revealed a pseudo-octahedral geometry with trans-phosphines. The ammine ligand is cis to the benzoyldiazenido group and the ammine hydrogens are hydrogen-bonded to the carbonyl oxygen. Reaction of [ReOCl3(PPh3)2] with excess Ph2NNH2.HCl in ethanol gave both [ReCl3(NNPh2)(PPh3)2] (6) and [ReCl2(N)(NNPh2)(PPh3)] (7). In the presence of base the rhenium(VII) cation [ReCl2(NNPh2)2(PPh3)+ was formed. The geometry of 7 was shown by X-ray structural determination to be a distorted square-based pyramid, with the nitride in the apical position. Attempted derivatization of 7 led to N-N bond cleavage and the generation of nitrido complexes. The nitrido complex [ReCl(N)(Me2CNNCOPh)(PPh3)2] (8) was unexpectedly formed in the reaction of [ReOCl3(PPh3)2] with Me2C=NNHCOPh in ethanol in the presence of HCl. The X-ray crystal structure of 8 showed a pseudo-octahedral geometry with the nitride ligand trans to the oxygen of the N,O-chelated hydrazonato(1-) ligand. The possible mechanisms of N-N bond cleavage are discussed.