Structural and spectroscopic studies of cobalt(II) complexes incorporating the bidentate phosphine ligand Ph2PCH2Si(CH3)2CH2PPh2
摘要:
A series of cobalt(II) complexes of general formula [CoX2L2] (X = Cl, Br, I, NO3, ClO4, NCS; L-2 = Ph2PCH2Si(CH3)(2)CH2PPh2) have been synthesised and characterised by electronic and infrared spectroscopy and by magnetic moment studies. The bidentate phosphine ligand is an analogue of 1,3-bis(diphenylphosphino)propane (dppp). X-ray analysis of the [CoBr2L2] complex proves tetrahedral geometry at the metal centre with the bidentate phosphine exhibiting a bite angle of 101.54(6)degrees. A range of evidence supports the existence of tetrahedral geometry about the metal in all the complexes in both the solid state and solution. Electronic spectroscopy is diagnostic for the tetrahedral d(7) metal ion in each case, with the nu(2) and nu(3) transitions clearly visible. Calculations of D-q and B', the RACAH parameter, have been performed for each complex; the relative magnitudes of B' indicate that the metal-phosphorus bonds are of increased covalency in comparison with Co(dppp) analogues. Magnetic moment studies show values of mu(B), in the range 4.4-4.9 B.M., as expected for tetrahedral cobalt(II). IR studies show that the nitrate and perchlorate ions in the respective complexes are bound in monodentate fashion, while the [Co(NCS)(2)(L-2)] complex exhibits N-bonded thiocyanate groups. (C) 1997 Elsevier Science Ltd.