Geometry, bonding, and optical and magnetic properties of Cu(CO)3. A theoretical study

A detailed analysis of the geometry, bonding, and optical and magnetic properties of copper tricarbonyl is presented. The molecule is shown to be planar, with D_3h symmetry. The calculations show good agreement with optical spectral data and with the observed ⁶³Cu and ¹³C hyperfine tensors. Spin-orbit and spin-polarization effects contribute to the axial departure of the ¹³C and ¹⁷O hyperfine tensors. Spin-orbit effects are modelled through a four-component relativistic molecular orbital formalism, and core spin-polarization effects are estimated from quasi-relativistic spin-unrestricted calculations. Spin-orbit effects introduce significant ligand orbital mixings, split the metal-based 3d orbitals by ∼0.15 eV, and introduce small but nonnegligible "orbital" contributions to the hyperfine tensors at the Cu, C, and O sites. The calculations predict that the unpaired electron spends most of its time on the CO ligand and has about 25% copper 4p_z character.