PD-II AND PT-II COMPLEXES CONTAINING 1,4,7,10,10-HEXAPHENYL-1,4,7,10-TETRAPHOSPHADECANE - FIRST X-RAY STRUCTURE OF A PD-TETRAPHOS COMPLEX

Pd-II and Pt-II complexes of meso- or 1,4,7,10,10-hexaphenyl-1,4,7,10- tetraphosphadecane (tetraphos-1, P4) have been prepared and characteri zed by X-ray diffraction methods, NMR spectroscopy (Pt-195{H-1}, P-31{ H-1}), elemental analyses and melting points. The first X-ray structur e of a Pd-tetraphos complex shows a strongly distorted square planar c oordination in meso-[PdP4]Cl-4 (1). The Pd-atom deviates 0.231 Angstro m A from the best plane through the phosphorus atoms leading to an ang le of 17.4 degrees between the planes through Pd and the phosphorus at oms of the PPh(2), and through Pd and the phosphorus atoms of the PPh groups, respectively. Rac-[PdClP4]Cl (2) shows a trigonal bipyramidal coordination. The destabilization of a square planar P4 arrangement in 2 is discussed in view of the X-ray structure of 1. Meso-(3) and rac- [Pd2Cl2(mu-Cl)P4]Cl (4) contain P4 in a chelating and bridging mode. I n the case of Pt(II) three further derivatives of the earlier reported complexes meso- or rac-[Pt2Cl2(mu-Cl)P4]Cl have been prepared: rac-[P t2Cl2(mu-Cl)(mu-t-dppe)P4]Cl (5), where t-dppe is trans-1,2-bis(diphen ylphosphino)ethylene, and meso- (6) and rac-[Pt2Cl2(mu-Cl)(mu-pyrimidi ne)P4](PF6) (7). The compounds 5-7 are rare examples of triply bridged Pt(II) dimers containing two five-coordinate Pt(II) centres.