99705-72-3Relevant academic research and scientific papers
Phosphorus-31 NMR studies and X-ray structures of five-coordinate cobalt(I) and nickel(II) complexes of tris(2-(diphenylphosphino)ethyl)phosphine
Hohman, William H.,Kountz, Dennis J.,Meek, Devon W.
, p. 616 - 623 (2008/10/08)
Two series of low-spin five-coordinate Co(I) and Ni(II) complexes of the tripod ligand tris(2-(diphenylphosphino)ethyl)phosphine, PP3, were synthesized and characterized by elemental analyses, electronic absorption spectra, and 31P{1H} NMR spectra. The complexes have trigonal-bipyramidal geometries in which the PP3 ligand occupies four of the five sites and a monodentate ligand occupies the fifth position. The 31P NMR spectral patterns are consistent with AX3 spin systems and trigonal-bipyramidal structures in solution. Several new complexes of the formulas [Co(PP3)(PR3)]X and [Ni(PP3)(PR3)]X2 were prepared. Generally, these pentaphosphorus complexes displayed first-order AMX3 (occasionally second-order ABX3) 31P NMR splitting patterns at 36.43 MHz; they were studied to determine the effect of the fifth ligand on the chemical shift of the bridgehead phosphorus atom of PP3. The complex [Co(PP3)(P(OMe)3)]BF4·1.5H2O crystallizes in the cubic space group P43n with a = 21.048 (3) A? and Z = 8. The cation [Co(PP3)(P(OMe)3)]+ (1) and the counterion BF4- lie on a crystallographic 3-fold axis. The isoelectronic complex [Ni(PP3)(P(OMe)3)](AsF6) 2·MeOH was also characterized by X-ray crystallography: C46H55As2F12NiO4P 5 crystallizes in the monoclinic space group P21/n with a = 13.263 (2) A?, b= 19.929 (5) A?, c =19.046 (4) A?, β = 96.15 (1)°, and Z = 4. The cation [Ni(PP3)(P(OMe)3)]2+ (2) and two AsF6- counterions lie in general crystallographic positions. Both the Co(I) and Ni(II) cations have similar structures, which are slightly distorted trigonal bipyramids; the most significant difference between the two geometries is the equatorial phosphorus to metal distances Co-P, 2.211 (6) A?, and Ni-P(av), 2.294 (2) A?.
