Pd(II) AND Pt(II) COMPLEXES CONTAINING 1,1,4,7,10,10- HEXAPHENYL-1,4,7,10-TETRAPHOSPHADECANE: FIRST X-RAY STRUCTURE OF A Pd-TETRAPHOS COMPLEX

Pd ii and Pt n complexes of meso- or rac- 1,1,4,7,10,10-hexaphenyl- 1,4,7,10-tetraphosphadecane (tetraphos-1, P4) have been prepared and characterized by X-ray diffraction methods, NMR spectroscopy (~gsPt{~H}, 31p{1H}), elemental analyses and melting points. The first X-ray structure of a Pd-tetraphos complex shows a strongly distorted square planar coordination in meso-[PdP4]Cl 2 (1). The Pd-atom deviates 0.231 ~ from the best plane through the phosphorus atoms leading to an angle of 17.4 ° between the planes through Pd and the phosphorus atoms of the PPh2, and through Pd and the phosphorus atoms of the PPh groups, respectively. Rac-[PdC1P4]C1 (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-[Pd2C12(#-C1)P4]CI (4) contain P4 in a chelating and bridging mode. In the case of Pt(II) three further derivatives of the earlier reported complexes meso- or rac-[Pt2C12(#-CI)P4]C1 have been prepared: rac-[Pt2C12(#- C1)(p-t-dppe)P4]Cl (5), where t-dppe is trans-l,2-bis(diphenylphosphino)ethylene, and meso- (6) and rac-[Pt2Cl2(#-C1)(#-pyrimidine)P4](PF6) (7). The compounds 5-7 are rare examples of triply bridged Pt(II) dimers containing two five-coordinate Pt(lI) centres.