Multinuclear nuclear magnetic resonance and X-ray crystallographic investigation of some mixed ligand alkylisocyanide platinum(II) complexes

ingle crystal X-ray diffraction structure determination of tetra-n-butylammonium tricyanomethylisocyanideplatinate(II) (1) show that the complex does not feature stacking of the anions or significant Pt-Pt orbital interactions. The cis-dicyanobismethylisocyanideplatinum(II) (2) and cis-dicyanobisethylisocyanideplatinum(II) (3) complexes do crystallize with the platinum atoms collinear with one another but with a Pt-Pt separation distance on the order of 3.5 angstrom, which is too great for significant orbital overlap. In each of the complexes studied, the Pt-CNR bond lengths of the isocyanides are shorter than the Pt-CN bond lengths of the cyanide ligands. Additionally, each of these complexes have Pt-CNR bond distances marginally shorter than in the parent complex, [Pt(CNR)(4)][BF4](2) (5). The shortened Pt-CNR distances in the mixed complexes are consistent with the isocyanide ligand being a stronger pi-acid than the cyanide ligand, resulting in a preferred cis configuration of the mixed ligand complexes. In solution, the NMR spectra of these complexes are unusual because they display (195)pt-(14) N and H-1- N-14 coupling with high resolution. The NMR parameters of these complexes are compared with those of Pt(CN)(4) (2-) and Pt(CNR)(4)(2+) (R = CH3 or C2H5). (c) 2005 Elsevier B.V. All rights reserved.