New Nitrosylrhenium Hydrides as Precursors of “Diazo” Complexes: Preparation of Hydrazine and Diazene Derivatives

The reaction of [ReCl 2 (OCH 3 )(NO)(PPh 3 ) 2 ] with phosphane in the presence of NaBH 4 gives different dihydride [ReH 2 (NO){PPh 2 (OEt)} 3 ] ( 1 ) and alkoxy‐hydride [ReH(OR 1 )(NO)P 3 ] ( 2 , 3 ) [R 1 = CH 3 , C 2 H 5 ; 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 Brønsted acid were performed and led to thermally unstable [Re(OR 1 )(η 2 ‐H 2 )(NO)P 3 ] + ( 2* , 3* ) dihydrogen cations. Hydrazine complexes [ReH(RNHNH 2 )(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 4 ) (R = H, CH 3 ,C 6 H 5 ) and [Re(OR 1 )(RNHNH 2 )(NO)P 3 ]BPh 4 ( 5 , 6 ) [R 1 = CH 3 , C 2 H 5 ; R = H, CH 3 ,C 6 H 5 ; P = PPh(OEt) 2 ] were prepared by allowing the hydrides [ReH 2 (NO)P 3 ] and [ReH(OR 1 )(NO)P 3 ] 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(OC 2 H 5 )(NH 2 NH 2 )(NO){PPh(OEt) 2 } 3 ]BPh 4 ( 5a ). Oxidation of the hydrazine complexes 4 − 6 was studied with Pb(OAc) 4 at −30 °C and, depending on the nature of the hydrazine and the stoichiometry of the complexes, led to aryldiazene [ReH(C 6 H 5 N=NH)(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 7c ), [Re(OC 2 H 5 )(C 6 H 5 N=NH)(NO){PPh(OEt) 2 } 3 ]BPh 4 ( 8c ), methyldiazene [ReH(CH 3 N=NH)(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 7b ) and a mixture of methyldiazene [Re(OCH 3 )(CH 3 N=NH)(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 9b ) and methyleneimine [Re(OCH 3 )(η 1 ‐NH=CH 2 )(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 9*b ) derivatives. Mono‐ and binuclear aryldiazene complexes [ReH(ArN=NH)(NO){PPh 2 (OEt)} 3 ]BPh 4 ( 10 ), [{ReH(NO)[PPh 2 (OEt)] 3 } 2 (µ‐HN=NAr−ArN=NH)](BPh 4 ) 2 ( 11 ), [Re(OR 1 )(ArN=NH)(NO)P 3 ]BPh 4 ( 12 , 14 , 16 ) and [{Re(OR 1 )(NO)P 3 } 2 (µ‐HN=NAr−ArN=NH)](BPh 4 ) 2 ( 13 , 15 ) [R 1 = CH 3 , C 2 H 5 ; P = PPh(OEt) 2 , P(OEt) 3 ; Ar = C 6 H 5 , 4‐CH 3 C 6 H 4 ; Ar‐Ar = 4,4′‐C 6 H 4 ‐C 6 H 4 ] were also prepared by allowing hydrides [ReH 2 (NO)[PPh 2 (OEt)} 3 ] and [ReH(OR 1 )(NO)P 3 ] to react with mono‐ and bis‐aryldiazonium cations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)