Mono- and bi-nuclear complexes of rhodium with functionalised diphosphine ligands

Abstract

Treatment of [RhCl(PPh₃)₃] with R₂PCH₂CH₂PR₂(R = C₆H₄SMe-2 or C₆H₄SPrⁱ-2) gives the ionic complexes [Rh(R₂PCH₂CH₂PR₂)]Cl A. When R = C₇H₄NS (benzothiazolyl) or C₈H₇N₂(N-methylbenzimidazolyl), however, the partially substituted complexes [RhCl(PPh₃)(R₂PCH₂CH₂PR₂)]B result. Treatment of B(R = C₇H₄NS) with CHCl₃ results in oxidation and disproportionation to the salt [(RhCl)₂(µ-dbtpe)₂][RhCl₄(dbtpe)]₂C[dbtpe =(C₇H₄NS)₂PCH₂CH₂P(SNC₇H₄)₂]. X-Ray diffraction analysis of C shows the cation to have a structure with a P–P chelated dbtpe ligand on each RhCl unit spanning the two metals by P,N ligation. The anion has regular octahedral co-ordination. Reaction of dbtpe with [{RhCl(cod)}₂](cod = cycloocta-1,5-diene) or [{RhCl(CO)₂}₂] gives [(RhCl)₂(µ-dbtpe)₂]D which also has two P–P chelated RhCl units linked by P,N ligation, as shown by an X-ray crystal structure analysis. Full spectroscopic details are given for these compounds and their possible inter-relationship is discussed.