Preparation and reactivity of hydrazine complexes of rhenium:: Synthesis of 1,2-diazene (NH=NH) and methyleneimine (CH2=NH) derivatives

The hydrazine complexes [Re(RNHNH2)(CO)(n)P5-n]BPh4 [R = H, CH3, Ar; n = 1-4; P = P(OEt)(3), PPh(OEt)(2), PPh2OEt] were prepared by allowing the hydride species [ReH(CO)(n)P5-n] to react first with a Bronsted acid and then with hydrazine. The reaction of either [Re(NH2NH2)(CO)(n)P5-n]BPh4 or [Re(ArNHNH2)(CO)(n)P5-n]BPh4 with Pb(OAc)(4) at -40 degreesC proceeds with the selective oxidation of the hydrazine ligand to yield either [Re(NH=NH)(CO)(n)P5-n]BPh4 or [Re(ArN=NH)(CO)(n)P5-n]BPh4. The oxidation of [Re-(CH3NHNH2)(CO)(n)P5-n]BPh4 (n = 1, 2) with Pb(OAc)(4) at -40 degreesC gives both [Re(CH3N=NH)(CO)(n)P5-n]BPh4 and [Re(eta(1)-NH=CH2)(CO)(n)P5-n]BPh4. Reduction reactions of both hydrazine and diazene complexes with Zn amalgam were also studied and yielded ammonia in moderate yield (20-25%). (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.