Molecular Structure of Gaseous Oxopivalate Co(II): Electronic States of Various Multiplicities

Synchronous electron diffraction/mass spectrometry was used to study the composition and structure of molecular forms existing in a saturated vapor of cobalt(II) oxopivalate at T = 410 K. It was found that monomeric complexes Co₄O(piv)₆ dominate in the vapor. The complex geometry possesses the C₃ symmetry with bond lengths Co-O_c = 1.975(5) Å and Co-O = 1.963(5) Å, as well as bond angles O_c-Co-O = 111.8(3)°, Co-O_c-Co = 110.4(6)°, O-Co-O = 107.1(3)° in the central O_cCo₄ fragment and four O_cCoO₃ fragments. The presence of an open 3d shell for each Co atom leads to the possibility of the existence of electronic states of the Co₄O(piv)₆ complex with Multiplicities 1, 3, 5, 7, 9, 11, and 13. For them, the CASSCF and XMCQDPT2 calculations predict similar energies, identical shapes of active orbitals, and geometric parameters, the difference between which is comparable with the error of determination by the electron diffraction experiment. QTAIM and NBO analysis show that the Co-O_c and Co-O bonds can be attributed to ionic (or coordination) bonds with a significant contribution of the covalent component. The high volatility and simple vapor composition make it possible to recommend cobalt (II) oxopivalate as precursors in the preparation of oxide films or coatings in the CVD technologies. The features of the electronic and geometric structure of the Co₄O(piv)₆ complex allows for the conclude that only a very small change in energy is required for the transition from antiferromagnetically to ferromagnetically coupled Co atoms.