New nitrosylrhenium hydrides as precursors of "diazo" complexes: Preparation of hydrazine and diazene derivatives

The reaction of [ReCl2(OCH3)(NO)(PPh3)21 with phosphane in the presence of NaBH4 gives different dihydride [ReH2(NO)(PPh2(OEt))(3)] (1) and alkoxy-hydride [ReH(OR1)-(NO)P-3] (2, 3) [R-1 = CH3, C2H5; P = PPh(OEt)(2), P(OEt)(3)] derivatives depending on the nature of the phosphane and the solvent used. The protonation reactions of the new hydrides with Bronsted acid were performed and led to thermally unstable [Re(OR1)(eta(2) -H-2)(NO)P-3](+)(2*, 3*) dihydrogen cations. Hydrazine complexes [ReH(RNHNH2)(NO){PPh2(OEt)}(3) BPh4 (4) (R= H, CH3,C6H5) and [Re(OR1)(RNHNH2)(NO)P-3]Bph(4) (5, 6) [R-1 = CH3, C2H5; R = H, CH3,C6H5; P = PPh(OEt)21 were prepared by allowing the hydrides [ReH2(NO)P3] and [ReH(OR')(NO)P:3j to react first with triflic acid and then with hydrazine. The complexes were characterized spectroscopically and by the X-ray crystal structure determination of [Re(OC2H5)(NH2NH2)(NO){PPh(OEt)(2)}(3)]-BPh4 (5a). Oxidation of the hydrazine complexes 4-6 was studied with Pb(OAc)(4) at -30 degreesC and, depending on the nature of the hydrazine and the stoichiometry of the complexes, led to aryldiazene [ReH(C6H5N=NH)(NO){PPh2(OEt)}(3)]BPh4 (7c), [Re(OC2H5)(C6H5N=NH)(NO){PPh(OEt)(2)}(3)]BPh4 (8C), methyldiazene [ReH(CH3N=NH)(NO){PPh2(OEt)}(3)]BPh4 (7b) and a mixture of methyldiazene [Re(OCH3)(CH3N= NH)(NO){PPh2(OEt)}(3)]PPh4 (9b) and methyleneimine [Re-(OCH3)(eta(1)-NH=CH2)(NO){PPh2(OEt)}(3)]BPh4 (9*b) derivatives. Mono- and binuclear aryldiazene complexes [ReH(ArN=NH)(NO){PPh2(OEt)}(3)]BPh4 (10), [ReH(NO)-[PPh2(OE')](3)}(2)(mu-HN=NAr-ArN=NH)](BPh4)(2) (11), [Re(OR1)-(ArN=NH) NO)P-3]BPh4 (12, 14, 16) and [{Re(OR1)(NO)P-3}(2)(mu- HN=NAr-ArN=NH)](PPh4)(2) (13, 15) [R-1 = CH3, C2H5; P = PPh(OEt)(2), P(OEt)(3); Ar = C6H5, 4-CH3C6H4; Ar-Ar = 4,4'C6H4-C6H4] were also prepared by allowing hydrides [ReH2(NO)[PPh2(OEt)}(3)] and [ReH(OR1)(NO)P-3] to react with mono- and bis-aryldiazonium cations. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)