Platinum(II) co-ordination chemistry of bis(diphenylphosphino)amine

Abstract

A spectroscopic and structural examination of the platinum(II) co-ordination chemistry of bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)methylamine (dppma) has been made. The complexes [Pt(dppa)Cl₂], [Pt(dppma)Cl₂], [Pt(dppa)(CN)₂], [Pt(dppma)(CN)₂], [Pt(dppa)₂]²⁺ and [Pt(dppma)₂]²⁺ as the chloride, iodide and tetrafluoroborate salts, [Pt(Ph₂PNPPh₂)₂], trans-[Pt-(dppa-P)₂(CN)₂] and [Pt₂(µ-dppa)₂(CN)₂] have been prepared. The solid-state structures of [Pt(dppa)₂][BF₄]₂·MeCN,[Pt(dppma)₂][BF₄]₂ and trans-[Pt(dppa-P)₂(CN)₂] have been determined by X-Ray crystallography. The crystallographic examination permits a critical evaluation of the nature of the strain in the four-membered rings formed by ligand chelation to a transition-metal centre. Structural and theoretical data suggest that bis(diphenylphosphino)amine chelate complexes should be more strained than the corresponding bis(diphenylphosphino)methane (dppm) complexes. The preference of Pt^II for binding to dppa rather than dppm implies the formation of a stronger Pt–P bond in complexes of the former ligand.