The syntheses, spectroscopic properties, and structures of the monovalent cobalt complexes, [PhTt(tBu)]Co(L), 1-L {PhTt(tBu) = phenyltris[(tert-butylthio)methyl]borate; L = PPh3, PMe3, PEt3, PMe2Ph, PMePh2, P(OPh)(3), CNBut}, are described. Complexes 1-L are prepared via the sodium amalgam reduction of [PhTt(tBu)]CoCl in the presence of L. The complexes display magnetic moments and paramagnetically shifted H-1 NMR spectra consistent with triplet, S = 1, ground states. The molecular geometries, determined by X-ray diffraction methods, reveal that some of the complexes display structures in which the L donor is moved off of the inherent 3-fold axis. In the most extreme cases (e.g., 1-P(OPh)(3) or 1-CNBut), the geometries can be described as cis-divacant octahedra. The origin of the geometric distortions is a consequence of the electronic characteristics of L as first deduced by Detrich et al. for [Tp(Np)]Co(L) (J. Am. Chem, Soc. 1996, 118, 1703). The results establish a linear correlation between the magnitude of the structural distortion and the electronic parameter of the phosphine donor.