Water soluble phosphine rhenium complexes

Reduction of [NMe4]2[ReBr5(NO)] (1) with zinc in acetonitrile leads to the known trisacetonitrile compound [ReBr2(CH3CN)3(NO)] (2). Attempts to turn 2 into a dihydrogen or a hydride complex applying direct reaction with H2 or with H2 and a base were unsuccessful. Complex 2 could be transformed into [ReBr(BF4)mer-(CH3CN)3(NO)] (2a) with AgBF4 in acetonitrile and was used as a starting material in a ligand exchange reaction with the water soluble phosphine 1,3,5-triaza-7-phosphadamantane (PTA) to obtain the complex [ReBr2(NO)(PTA)3] (3). When the reduction of 1 with zinc was carried out in the presence of PTA in acetonitrile, the disubstituted complex [ReBr2(CH3CN)(NO)(PTA)2] (4) was formed. The olefin-coordinated rhenium complexes [ReBr2(NO)(CH2double bond; length as m-dashCH2)(PTA)2] (5a) and [ReBr2(NO)(PhCHdouble bond; length as m-dashCH2)(PTA)2] (5b) were obtained from the reaction of 4 with the corresponding olefins. Complex 4 reacts further with NaHBEt3 in THF to give the dihydride [ReH2(THF)(NO)(PTA)2] (6). In the presence of ethylene 6 is transformed into the ethyl hydride complex [ReH(CH2CH3)(η2-C2H4)(NO)(PTA)2] (7). Complexes 6 showed catalytic activity in the hydrogenation of olefins.