BINUCLEAR PLATINUM(II) COMPLEXES OF 1,4,7,10,10-HEXAPHENYL-1,4,7,10-TETRAPHOSPHADECANE (P4) CONTAINING VARIOUS BRIDGING LIGANDS AS SPACERS BETWEEN THE P4 COORDINATION UNITS

The former reported complex cis,meso-[Pt2Cl4P4] (1), where P4 is 1,4,7 ,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane and which contains a chl oro bridge only in solution, is fully characterized by an X-ray struct ure analysis: triclinic, P1BAR; a = 8.395(2), b = 11.675(2), c = 13.71 7(3) angstrom, alpha = 92.54(3), beta = 98.93(3), gamma = 109.28(3)-de grees, R = 0.059 for 2872 observed reflections (F > 6.0(F)). It shows an open-mode dimer with a Pt-Pt distance of 6.916(1) angstrom and a ci s P4 configuration. A comparison with the X-ray structure of cis,rac-[ Pt2Cl4P4] (2) is given. 2 also contains a chloro bridge only in soluti on, and these chloro bridges of 1 or 2 are replaced by hydride in rac- [Pt2H2(mu-H)P4](BF4) (3), by pyridine in rac-[Pt2Cl2(mu-C5H5N)P4](BPh4 )2 (4), by pyrazolate (Pz) in rac-[Pt2Cl2(mu-Pz)P4](BPh4) (5), and by imidazolate (Im) in meso-[Pt2Cl2(mu-Im)P4](BPh4) (6) and rac-[Pt2Cl2(m u-Im)P4](BPh4) (7). In rac-[Pt2Cl2(mu-dppa)P4](BPh4) (8), where dppa i s 1,2-bis(diphenylphosphino)acetylene, an additional dppa bridge occur s. The complexes have been characterized by Pt-195{H-1}, P-31{H-1} and H-1 NMR spectroscopy, elemental analyses and melting points. 3, 4, 5, 7 and 8 show that rac-P4 is flexible enough to allow the reaction wit h bridging ligands of very different sizes, whereas in the case of mes o-P4 only the incorporation of imidazolate (6) is possible. This diffe rent behavior of meso- and rac-P4 is discussed with respect to the X-r ay structures of 1 and 2, showing that completely different rotation i somers could be responsible for the observed reactivity. In meso-[Pt2C l(mu-Cl)(SnCl3)P4](BPh4) (9) the oxidative addition of SnCl2 is only p ossible at a terminal Pt-Cl bond.