137867-96-0Relevant articles and documents
Electronic Paramagnetic Resonance Studies of Radical Pairs ->2 (M = Cr, Mo, W) trapped in Single Crystals of PPh4+HM(CO)5-
Hynes, Rosemary C.,Preston, Keith F.,Springs, Jerry J.,Tse, John S.,Williams, Antony J.
, p. 3121 - 3128 (1991)
γ-Irradiated single crystals of PPh4+HM(CO)5- (M = Cr, Mo, W) exhibit powerful EPR spectra due to two distinct interacting pairs of M(CO)5- radicals. g-and fine-structure (D) matrices were determined from measurements at 77 K of EPR spectra obtained as a function of angle in the ac and aa' planes of crystallographically aligned single crystals of the Mo and W compounds.The data are compared with those obtained previously for the Cr compound.In all three cases, g and one of the D-tensors are aligned with the tetragonal c-axis of the crystal, and the principal g-values are appropriate for d7 square-pyramidal M(CO)5- radicals.Classical dipolar calculations show that the two radical pairs correspond to the closest and next-closest pair of undamaged anions in the crystals, the former lying along a skew direction.The D-values for the Mo and W closest pairs indicate a substantial contribution from anisotropic exchange to the coupling of the two unpaired electrons.