Tris dimethylphenylphosphine pentahydridorhenium V

The reduction of mer-trichlorotris(dimethylphenylphosphine)rhenium-(III)1 3 with sodium tetrahydroborate(l —), as described below, provides a clean synthesis of tris(dimethylphenylphosphine)pentahydridorhenium(V), 

A suspension of 3.83 g (5.4 mmol) of mer-trichlorotris(dimethylphenyl-phosphine)rhenium(HI) (or its benzene solvate)1 and 2.48 g (65 mmol) of sodium tetrahydroborate(l —) in 100 mL of absolute ethanol is heated under nitrogen on a steam bath until the orange complex dissolves to give a colorless suspension. The solvent is evaporated under reduced pressure, and the residue is extracted with three 75-mL portions of benzene. The benzene extract is evaporated, and the residue is crystallized from 60 mL of absolute ethanol to give prisms of tris(dimethylphenylphosphine)pentahydrido-rhenium(V) the yield is 2.2 g (67%). Anal. Calcd. for C24H38P3Re C, 47.59 H, 6.32 P, 15.34. Found (checkers values) C, 47.60 H, 6.24 P, 15.51. 

Tris(dimethylphenylphosphine)pentahydridorhenium(V) is a white, crystalline solid, mp 97-98°. It may be remelted several times without apparent decomposition and is stable for several months at 20°. It is soluble in cold benzene but much less soluble in cold ethanol or light petroleum ether. The rhenium-hydrogen stretching vibrations, v(Re—H), are (in Nujol mull) 1949 (w, sh), 1931 (m), 1905 (m), and 1852 (m) (in benzene solution) 1969 (sh), 1898, 1855, 1817 (sh) cm-1. In the nmr spectrum (benzene at 34°) the hydridic hydrogens are apparently equivalent (fluxional molecule) 

Snbmltted by M. A. ANDREWS, S. W. K1RTLEY, and H. D. KAESZ Checked by C. R COOPER, lilt 

The THF used in this synthesis was dried by distillation under nitrogen from calcium hydride. All operations should be carried out under an atmosphere of nitrogen6 until the product is isolated in solid form. 

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