Coordination of bis(azol-1-yl)methane-based bisphosphines towards Ru, Rh, Pd and Pt: synthesis, structural and catalytic studies.

The coordination chemistry of bisphosphine ligands assembled on the five-membered heterocyclic platform of bis(azol-1-yl)methane viz.: bis(2-diphenylphosphinoimidazol-1-yl)methane (1), bis(5-diphenylphosphinopyrazol-1-yl)methane (2) and bis(5-diphenylphosphino-1,2,4-triazol-1-yl)methane (3) with Ru, Rh, Pd and Pt is described. The bisphosphines 1-3 react with elemental selenium to give the corresponding bis-selenoyl derivatives 4-6. The reactions of 1-3 with transition metal derivatives produce complexes with different coordination modes. Bisphosphine 1 showed a preference for the κ-P,P mode of coordination, whereas bisphosphines 2 and 3, besides the κ-P,P mode also showed a head-to-tail κ-P,N coordination mode resulting in the formation of binuclear complexes [Rh(COD){(CH(1,2-CHNPPh))-κP,N}][BF] (14), [Rh(COD){(CH(1,2,4-CHNPPh))-κP,N}][BF] (15), [Pd(η-CH){(CH(1,2-CHNPPh))-κP,N}][BF] (21) and [Pd(η-CH){(CH(1,2,4-CHNPPh))-κP,N}][BF] (22). Several of these complexes have also been structurally characterized. The in situ generated Rh complex of bisphosphine 1 showed moderate to good selectivity in the hydroformylation of various styrene derivatives.