A. P. Ginsberg

Magnetic Exchange in Transition Metal Complexes. VII. Spin Coupling in μ4‐Oxohexa‐μ‐halotetrakis [(Triphenylphosphine Oxide or Pyridine) Copper(II)]: Evidence for Antisymmetric Exchange

Magnetic susceptibility measurements are reported for a group of tetrameric Cu(II) complexes Cu4OX6L4 with X = Cl, L = (C6H5)3PO and X = Br, L = (C6H5)3PO or C5H5N. All samples show an effective magnetic moment μeff per copper ion which exhibits a maximum in the 40–60°K temperature range and which, in general, cannot be quantitatively accounted for by simple Heisenberg theory. The results contrast with those observed for the closely related anionic cluster [Cu4OCl10]4− which exhibits a monotonic variation of μeff with temperature and is compatible with simple Heisenberg theory. It is suggested that the difference may be due to a different relative arrangement of 3d Cu(II) energy levels in the anionic cluster, leaving an orbital singlet state lowest in the [Cu4OCl10]4− environment but an orbitally degenerate level lowest in the other complexes. To test the hypothesis the copper‐pair exchange Hamiltonian is derived for the orbitally degenerate case and shown, for the tetramer environment, to contain a large...

Electric Deflection of Molecular Beams of Carbon Suboxide and Carbon Subsulfide

The deflection behavior of molecular beams of C3O2 at 200 and 300°K and C3S2 at 300°K has been studied in inhomogeneous electric fields. Both species show net defocusing of the scattered beam with applied field. By comparison with the bent molecule NO2 whose electric dipole moment is known, upper limits of 0.15 D were placed on the electric moments of C3O2 and C3S2. These limits, coupled with extimates of the integrated absorption intensities obtained from published spectra for the ν7 vibration, permit upper limits of 0.15 rad to be placed on the bending angle. The most probable configuration is thus linear.

The electronic structure and the optical and photoelectron spectra of carbon subsulfide

Carbon subsulfide, the linear molecule S=C=C=C=S, has been investigated by self‐consistent field‐Xα‐scattered wave calculations (overlapping spheres), optical (650–230 nm), and photoelectron [He(I) and He(II)] spectroscopy. The ground state valence level electronic configuration is found to be (6σ+g)2(5σ+u)2(7σ+g)2(6σ+ u)2 (7σ+u)2(8σ+g)2(2πu)4(2πg)4(3πu)4. Comparison of the photoelectron band positions with the calculated ionization potentials, and analysis of their vibrational structure, allows assignments to be made. The experimental ionization potentials (ev) are 3πu(9.09), 2πg(11.24), 2πu(12.87), 8σ+g(14.47), 7σ+u(14.87), 6σ+u(18.2), 7σ+g(19.3), 5σ+u(20.5), 6σ+g(21.9). Agreement between calculated and experimental ionization potentials is very good for the π levels, fair for the 8σ+g and 7σ+u levels and poor for the remaining (low lying) σ levels, although the splittings between the low lying σ levels are correctly calculated. There are two principle features in the optical spectrum, a weak band at 20...

Dependence of iridium Mössbauer isomer shifts on oxidation state: an inversion for low valent carbonyl complexes

Abstract The 193 Ir Mossbauer isomer shifts of a set of closely related iridium carbonyl chloride complexes with oxidation states +1, +1.1, +1.4, and +2 have been found to decrease with increasing oxidation state. This is the inverse of the normal trend due to decreased shielding of the s electrons from the nuclear charge by removal of d electrons, and is attributed to the combined effect of strong π-backbonding and 6s character in the nominally 5d electrons removed in changing the oxidation state. An inverted isomer shift-oxidation state dependence is predicted for d m ( m > 7) metal complexes with strong π-acceptor ligands.

Magnetic exchange in transition metal complexes. X. Parallel spin coupling in di‐μ‐chloro‐octachlorodimolybdenum(V)

A measurement and analysis has been made of the temperature dependence of the magnetic susceptibility of dimeric Mo2Cl10. Ferromagnetic exchange is found within the dimer, a result which is anomalous by comparison with the antiferromagnetic coupling found in other d1 dimers. A crystal field analysis is given of Mo5+ in the local C2ν environment of the dimeric configuration, and an explanation of the ferromagnetic coupling proposed. The resultant interdimer interaction is also found to be ferromagnetic, though small, and suggests that a ferromagnetic or ferrimagnetic ordering of the essentially fully aligned (spin triplet) dimers occurs at low temperatures.