The Beauty and Complexity of the Mixed-Ligand Pd(II)-containing Monomers, Oligomers and Polymers Built upon Diphosphines and 1,8-Diisocyano- p -menthane

The starting materials Pd(diphos)Cl 2 where diphos = bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)propane (dppp), bis(diphenylphosphino)butane (dppb), and Pd 2 (diphos′) 2 Cl 4 where diphos′ = bis(diphenylphosphino)pentane (dpppen) and bis(diphenylphosphino)hexane (dpph) were reacted with the bridging ligand 1,8-diisocyano- p -menthane (dmb) to form species of the type {Pd 2 (diphos) 2 (dmb) 2 4+ } n and {Pd(diphos′) 2 (dmb) 2 4+ } n . Except for Pd 2 (dppe) 2 (dmb) 2 4+ , which was characterized by X-ray crystallography, the identity of the other weakly soluble dmb-containing materials were exhaustively characterized in solution and in the solid state by 31 P NMR (Magic Angle Spinning), chemical analyses, MALDI-TOF, DSC, TGA, IR and T 1 /NOE ( 31 P NMR spin-lattice relaxation time and nuclear overhauser enhancement constant measurements). Model compounds such as Pd(diphos)(CN-tBu) 2 2+ (diphos = dppe, dppp, dppb) and Pd 2 (diphos′) 2 (CN-tBu) 4 4+ (diphos′ = dpppen, dpph; as BF 4 − or PF 6 − salts), were prepared and also characterized by X-ray crystallography. Evidence for mono- (model complexes only of the type dppe, dppp, and dppb) and dinuclear complexes, as well as oligomers and polymers, are obtained for most cases, as well as the presence of monomer–oligomer (or polymer) equilibrium. During the course of this study, the complexes [Pd(dppp)(CN-tBu) 2 ](TCNQ)(Cl), [Pd 2 (dpppen) 2 (CN-tBu) 2 (Cl) 2 ](PF 6 ) 2 , and [Pd 2 (dpppen) 2 (CN-tBu) 2 (CN) 2 ](TCNQ) 2 (TCNQ − = tetraquinodimethane anion) were isolated and characterized by X-ray crystallography.