Nickel(II) complexes containing 1,1,4,7,10, 10-hexaphenyl-1,4,7,10-tetraphosphadecane: First X-ray structures of nickel-tetraphos-1 complexes

Article abstract of DOI:10.1016/0277-5387(95)00475-0

Mono- and bimetallic Ni^II complexes of rac-or meso-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, ³¹P{¹H} NMR spectroscopy, elemental analyses and melting points. The first two X-ray structures of Ni-tetraphos-1 complexes show distorted square planar coordinations in rac-[NiP4](BPh₄)₂ (2) and rac-[Ni₂Cl₄P4] (5). In 2 the mean deviation of the phosphorus atoms from a least-squares plane through the phosphorus atoms and the nickel atom is 0.224 A. The nickel atom deviates 0.034 A from this plane. In 5 the mean deviation of the phosphorus and chlorine atoms from the corresponding plane is 0.023 A, the nickel atom deviating 0.028 A from this plane. The mean chelate P - Ni - P angle of 84.75° in 2 significantly deviates from the chelate angle of 86.90(11)° in 5, which is an open-mode dimer with a Ni - Ni distance of 6.339(1) A and a cis chelating and bridging P4 configuration. The two coordination planes of 5 include an angle of 7.2°. In contrast to rac-[NiP4]Cl₂ (1), the P4 coordination in 2 shows a pronounced solvent dependence. In neither meso-[NiP4]Cl₂ (3) nor meso-[NiP4](BPh₄)₂ (4) does a similar solvent effect occur. However, an easy transition between rac-or meso-[NiP4](NiCl₄) and rac-(5) or meso-[Ni₂Cl₄P4] (6) is possible, depending on the solvent. This transition is discussed in view of the X-ray structures of 2 and 5. Furthermore, a comparison of the structures of 2 and 5 with the known X-ray structures of rac-or meso-[PtP4](BPh₄)₂, rac-or meso-[Pt₂Cl₄P4] and meso-[PdP4]Cl₂ is given.