Synthesis and crystal and molecular structure of [Fe2Rh2(µ-PPh2)4(µ-CO)2(CO)6], an unusual straight-chain tetranuclear compound

Abstract

Reaction of [{Rh(η³-C₃H₅)₂Cl}₂] with [Fe(CO)₄(PPh₂H)] in alcohol in the presence of carbon monoxide affords an unusual straight-chain compound, [Fe₂Rh₂(µ-PPh₂)₄(µ-CO)₂(CO)₆], the structure of which has been determined by X-ray methods. The complex crystallizes in space group P2₁/c with a= 12.468(5), b= 13.354(5), c= 17.293(7)Å, β= 95.43(1)°, and Z= 2. The metal-atom skeleton is a centrosymmetric Fe–Rh–Rh–Fe chain with the metal atoms being linked through closed Fe–P–Rh and Rh–P–Rh bridge bonds. The ³¹P-{¹H} n.m.r. spectral data for the compound have been interpreted in terms of the presence of two isomeric forms in solution.