A series of di-nuclear rhodium(i) complexes with trialkylstibines as bridging ligandsDedicated to Professor Wolfgang Malisch, a respected colleague and creative scientist, on the occasion of his 60th birthday.

Abstract

Metathetical reactions of [Rh2Cl2(μ-CPh2)2(μ-SbiPr3)] 1 with NaBr and NaI afforded the corresponding di-nuclear complexes [Rh2X2(μ-CPh2)2(μ-SbiPr3)] (X = Br 2, I 3) in practically quantitative yields. Analogous displacement reactions of 1 with equimolar amounts of the sodium salts of acetylacetone (acacH), trifluoracetylacetone (acac-f3-H) and dipivaloylmethane (dpmH) led to the formation of the unsymmetrical rhodium(I) compounds [Rh2(X)Cl(μ-CPh2)2(μ-SbiPr3)] (X = acac 4, acac-f35, dpm 6). From 1 and excess of Na(acac) and Na(dpm), the symmetrical complexes [Rh2X2(μ-CPh2)2(μ-SbiPr3)] (X = acac 7, dpm 8) were formed. Treatment of 7 with acetic acid and trifluoracetic acid in the molar ratio of 1 ∶ 1 gave the unsymmetrical compounds [Rh2X(acac)(μ-CPh2)2(μ-SbiPr3)] (X = CF3CO29, CH3CO210), while with an excess of CR3CO2H the symmetrical complexes [Rh2(κ2-O2CR3)2(μ-CPh2)2(μ-SbiPr3)] (R = F 11, H 12) were obtained. The X-ray crystal structure analysis of 12 revealed that analogously to 1 the stibine ligand occupies a symmetrical bridging position. The reactions of 1, 4 and 7 with SbEt3 and Sb(CH2Ph)3 led to bridge-ligand exchange and gave the di-nuclear compounds [Rh2(acac)Cl(μ-CPh2)2(μ-SbEt3)] 13 and [Rh2X(X′)(μ-CPh2)2{μ-Sb(CH2Ph)3}] (X = X′ = Cl 14, X = Cl, X′ = acac 15, X = X′ = acac 16) without cleavage of the [Rh2(μ-CPh2)2] core fragment.