Heterometallic phosphinidene-bridged complexes derived from the phosphanyl complexes syn-[MCp(PHR*)(CO)2] (M = Mo, W; R* = 2,4,6-C6H2tBu3)

Abstract

The title phosphanyl complexes were prepared upon photolysis of equimolar mixtures of dimers [M2Cp2(CO)6] and PH2R* (R* = 2,4,6-C6H2tBu3). They were converted into the corresponding chlorophosphanyl derivatives syn-[MCp(PClR*)(CO)2] upon reaction with CCl4, while its deprotonation (M = Mo) yielded the phosphinidene Li[MoCp(PR*)(CO)2]. These mononuclear precursors were tested for the synthesis of heterometallic PR*-bridged derivatives by following three synthetic strategies. Photochemical reactions between phosphanyl complexes and dimers [M´2(CO)2n] or [M´2Cp2(CO)2n] (M’ = Mn, Re, Fe, Ru, Co) gave binuclear derivatives of types [MM´Cpx(μ-PR*)(CO)n+2] and [MoM´Cpx(μ-PR*)(CO)n+1] (x = 1,2), but yields were very poor except for the WRe complexes. Combinations with Co, Mn, and Re were best made through reaction between carbonylates [M’(CO)n]− and chlorophosphanyl complexes, to give respectively the pentacarbonyl [MoCoCp(μ-PR*)(CO)5] and the heptacarbonyls [MM´Cp(μ-PR*)(CO)7] (MM’ = MoRe, MoMn, WMn). The latter were easily decarbonylated thermally to give hexacarbonyls [MM´Cp(μ-PR*)(CO)6], which display heterometallic single bonds and short M−P distances of ca. 2.27 Å formulated as double M=P bonds, and rearranged upon thermal or photochemical activation to give the hydride-phosphanyl derivatives [MM´Cp(μ-H){μ-P(CH2CMe2)C6H2tBu2}(CO)6]. This process was suppressed in the photochemical reactions by using a THF/NCMe (10:1) mixture as solvent, but then the acetonitrile complexes [MoM´Cp(μ-PR*)(CO)5(1κ-NCMe)] were formed. Combinations with Fe and Ru were best prepared by reacting Li[MoCp(PR*)(CO)2] with halide complexes [MXCp(CO)2], to give the tetracarbonyls [MoM´Cp2(μ-PR*)(CO)4] (M’ = Fe, Ru), a method also useful to prepare the gold complex [MoAuCp(μ-PR*)(CO)2{P(p-tol)3}] upon reaction with [AuCl{P(p-tol)3}]. The above tetracarbonyl complexes were decarbonylated photochemically to give the metal-metal bound tricarbonyls [MoM´Cp2(μ-PR*)(CO)3].