Coordination behaviour in transition metal complexes of asymmetric NPN ligands

Two bicyclic, chiral aminophosphine ligands, namely 4R, 9R-1,3-bis(pyridin-2-ylmethyl)-2-(2-propyl)octahydro-1H-1,3,2-benzodiazaphosphole (1) and 4R, 9R-1,3-bis(pyridin-2-ylmethyl)-2-(2-ethoxy)octahydro-1H-1,3,2-benzodiazaphosphole (2) have been prepared from 1R, 2R-diaminocyclohexane and the appropriate dichlorophosphine and the nature of their coordination to a number of transition metals explored. Ligand 1 coordinates to Pd(II) and Pt(II) as a terdentate donor to give complexes of the type [M(kappa(3)-N,P,N-1)Cl](+) whereas ligand 2 favours bidentate kappa(2)-P,N coordination to give the complexes M(kappa(2)-P,N-2)Cl-2. The study of the coordination chemistry of the NPN ligand 1 is frustrated by its ready decomposition to an unknown species which appears to be promoted by transition metals. The ligand 2 does not undergo such a transformation and its metal chemistry is more readily examined. Aside from the Pt(II) and Pd(II) complexes above, 2 has been coordinated to Cr(0) and Mo(0) in the octahedral complexes M(kappa(2)-P,N-2)(CO)(4) and Au(I) in linear Au(kappa(1)-P-2)Cl. All the complexes have been fully characterised by spectroscopic and analytical techniques including a single-crystal X-ray structure analysis of [Pt(kappa(3)-N,P,N-1)Cl]Cl, 3. (C) 2010 Elsevier Ltd. All rights reserved.