The palladium-catalysed reaction between [Re2(CO)10] and phosphines and the crystal and molecular structure of diaxial [Re2(CO)8(PMe2Ph)2]

The reaction between [Re2(CO)10] and PR3[PR3= PPh3, PMePh2, PMe2Ph, PMe3, P(CH2Ph)3, or P(OMe)3] in xylene is catalysed by Pd/C, Pd/CaCO3, and PdO and yields the complexes [Re2(CO)10–n(PR3)n](n=1 or 2) as the major products (15–80%). Attempts to synthesise [Re2(CO)10–n(PR3)n] from [Re2(CO)10] and PR3in the presence of NMe3O under milder conditions (e.g. refluxing CH2Cl2) also gave the above products with n=1 or 2 as well as high yields of fac[ReCl(CO)3(PR3)2]. An X-ray crystal structure determination of diaxial [Re2(CO)8(PMe2Ph)2] was carried out: space group C2/c, Z= 4, a= 22.779(9), b= 7.1 66(3), c= 17.249(7)Å, β= 95.13(3)°, R= 0.0602. The structure has a staggered geometry with torsion angles deviating by ± 6° from the ideal (45°). The Re–Re bond length was found to be 3.044(1)Å, cf., 3.041(1)Å for [Re2(CO)10], indicating that this parameter is almost invariant on substitution of CO by PMe2Ph.