SEMI-QUINONE RADICAL-ANION COORDINATION TO DIVALENT COBALT AND NICKEL - STRUCTURAL FEATURES OF THE BIS(3,5-DI-TERT-BUTYL-1,2-SEMIQUINONE)COBALT(II) TETRAMER

The complex Co(O2C6H2O-Bu)2)2 has been prepared by treating CO2(CO)8 with 3, 5-di-tert-butyl-1, 2-benzoquinone in benzene solution. The dark green complex has been shown by a crystallographic molecular structure determination to be tetrameric, Co4(O2C6H2(t-Bu)2)8, with octahedrally coordinated metal ions. Crystals form as benzene solvates in the triclinic space group P$$ with one independent centrosymmetric complex molecule per unit cell. Unit cell dimensions are a = 15.594 (5) Å, b = 15.902 (7) Å, c = 15.972 (5) Å, a = 94.34 (2)°, = 107.92 (3)°, γ = 118.48 (3)°, and V= 3193.1 Å3. Cobalt-oxygen bond lengths within the coordination sphere are typical for high-spin Co(II) and carbon-oxygen lengths of the ligands are of the value found for complexed semiquinone ligands. The related nickel complex Ni4(O2C6H2(t-Bu)2)8 is isostructural with the cobalt analogue. Spectral similarities between complexes of Ni and Co prepared with tetrachloro-l, 2-benzoquinone, 9, 10-phenanthrenequinone, and 3, 5-di-rm-butyl-1, 2-benzoquinone with related tris(semiquinone) complexes of V, Fe, and Cr indicate that these should be formulated as bis(semiquinone) complexes of the divalent metal ions likely having oligomeric structures with octahedrally coordinated metal ions. The room-temperature magnetic susceptibilities of these compounds are discussed in terms of an antiferromagnetic metal-ligand exchange interaction similar to that found for the tris complexes. © 1979, American Chemical Society. All rights reserved.