NICKEL(II) COMPLEXES CONTAINING 1,4,7,10,10-HEXAPHENYL-1,4,7,10-TETRAPHOSPHADECANE - FIRST X-RAY STRUCTURES OF NICKEL-TETRAPHOS-1 COMPLEXES

Mono- and bimetallic Ni-II complexes of rac- or meso-1,1,4,7,10,10-hex aphenyl-1,4,7, 10-tetraphosphadecane (tetraphos-1, P4) have been prepa red and characterized by Xray diffraction methods, P-31{H-1} NMR spect roscopy, elemental analyses and melting points. The first two X-ray st ructures of Ni-tetraphos-1 complexes show distorted square planar coor dinations in rac-[NiP4](BPh(4))(2), (2) and rac-[Ni(2)Cl(4)P4] (5). In 2 the mean deviation of the phosphorus atoms from a least-squares pla ne through the phosphorus atoms and the nickel atom is 0.224 Angstrom. The nickel atom deviates 0.034 Angstrom from this plane. In 5 the mea n deviation of the phosphorus and chlorine atoms from the correspondin g plane is 0.023 Angstrom, the nickel atom deviating 0.028 Angstrom fr om this plane. The mean chelate P-Ni-P angle of 84.75 degrees in 2 sig nificantly deviates from the chelate angle of 86.90(11)degrees in 5, w hich is an open-mode dimer with a Ni-Ni distance of 6.339(1) Angstrom and a cis chelating and bridging P4 configuration. The two coordinatio n planes of 5 include an angle of 7.2 degrees. In contrast to rac-[NiP 4]Cl-2 (1), the P4 coordination in 2 shows a pronounced solvent depend ence. In neither meso-[NiP4]Cl-2 (3) nor meso-[NiP4](BPh(4))(2) (4) do es a similar solvent effect occur. However, an easy transition between rac- or meso-[NiP4](NiCl4) and rac-(5) or meso-[Ni(2)Cl(4)P4] (6) is possible, depending on the solvent. This transition is discussed in vi ew of the X-ray structures of 2 and 5. Furthermore, a comparison of th e structures of 2 and 5 with the known X-ray structures of rac- or mes o-[PtP4](BPh(4))(2), rac- or meso-[Pt(2)Cl(4)P4] and meso-[PdP4]Cl-2 i s given.