Mono‐ and Dinuclear Rhenium Polyhydride Complexes Bearing the Chelating Ligand 1,2‐Bis(dicyclohexylphosphanyloxy)ethane

Variable‐temperature NMR spectroscopic studies of new rhenium polyhydride compounds of the type [ReH 7 (dcype)] ( 1 ), [Re 2 H 8 (dcype) 2 ] ( 3 ) and [ReH 5 (dcype)L] ( 5a − f ) [dcype = Cy 2 PO(CH 2 ) 2 OPCy 2 ; L = PPh n (OR) 3− n , n = 0−2, R = Me, Et] show them to be highly fluxional classical hydride complexes. In the case of the ethoxy compounds 5b , 5d and 5f , three hydride interchange processes were observed in the temperature range 283−173 K and their activation parameters were determined by NMR line‐shape analysis. A mechanism is proposed for each. Protonation of 1 and 5 with HBF 4 ·OMe 2 gave the nonclassical hydrides [ReH 8 (dcype)]BF 4 ( 2 ) and [ReH 6 (dcype)L]BF 4 ( 6 ) which are relatively stable. Compound 2 decomposes at 273 K in solution releasing H 2 ,whereas compound 6 can be stored at room temperature for more than 24 h without decomposition. Protonation of 3 with HBF 4 ·OMe 2 gave the classical dinuclear hydride [Re 2 H 9 (dcype) 2 ]BF 4 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)