A new synthetic route to ligands of the general composition R2PCH2ER′2 (E = P, As) and some rhodium complexes derived thereof

Abstract

Symmetrical and unsymmetrical bis(phosphino)methanes R₂PCH₂PR′₂ (8–16) as well as the arsino(phosphino) analogues R′₂AsCH₂PR₂ (21–25) with bulky alkyl, cycloalkyl or aryl groups R and R′ were prepared from the stannylated phosphines R₂PCH₂SnR″₃ (3–5, 6, 7) via metalation with MeLi or PhLi in the presence of tetramethylethylenediamine and subsequent treatment with R′₂PCl or R′₂AsCl, respectively. Compound 25 [R′ = Cy, R = (R)-menthyl] is the first arsino(phosphino)methane which has been structurally characterized. The bis(phosphino)methanes R₂PCH₂PR₂ (R = Prⁱ 17, Cy 18) and R₂PCH₂PR′₂ (12, 19, 20) were also obtained by thermal reaction of R₂PCH₂SnPh₃ and the corresponding chlorophosphine R₂PCl or R′₂PCl in the absence of solvent. The bis(cyclooctene) derivative [RhCl(C₈H₁₄)₂]₂ 26 reacted with excess Prⁱ₂PCH₂PPrⁱ₂ to give [Rh(κ²P,P′-Prⁱ₂PCH₂PPrⁱ₂)₂]Cl 27, while treatment of 26 with Ph₂PCH₂PPrⁱ₂ yielded the chloro-bridged dimer [RhCl(κ²P,P′-Ph₂PCH₂PPrⁱ₂)]₂ 28. The reaction of the cationic species [Rh(C₈H₁₄)₂(OCMe₂)₂]PF₆ 29 with Cy₂PCH₂PPrⁱ₂ in benzene or toluene afforded the half-sandwich-type complexes [(η⁶-C₆H₆)Rh(κ²P,P′-Cy₂PCH₂PPrⁱ₂)]PF₆ 30, [(η⁶-C₆H₅CH₃)Rh(κ²P,P′-Cy₂PCH₂PPrⁱ₂)]PF₆ 31, of which the latter was characterized by X-ray crystallography.