Oxazoles XXII. The Cobalt(II) Coordination Chemistry of 2-(ortho-Anilinyl)-4,4-dimethyl-2-oxazoline: Syntheses, Properties, and Solid-State Structural Characterization

Ethanol solutions of the cobalt(II) halides react with an excess of 2-(ortho-anilinyl)-4,4-dimethyl-2-oxazoline (1: i.e. 2-(2'-anilinyl)-4,4-dimethyl-4,5-dihydro-1,3-oxazole) to give isolable kappa(2)-N, N'-bonded species of 1 in good to excellent yields. The complexes CoX2(1-kappa(2)- N,N')center dot(H2O)(n) have been isolated for X = Cl (2: n= 1/2), X = Br and I (3 and 4, respectively; n = 0); the solid-state structures (X-ray) are in accordance with those suggested by UV-visible spectroscopy and conductivity measurements (i.e. non-ionic complexes with a pseudo-tetrahedral coordination motif around Co). In contrast, reaction of excess 1 with Co(NCS)(2) forms the octahedral (UV-visible, X-ray) bis-isothiocyanato complex Co(NCS-kappa(1)-N')(2)(1-kappa(2)- N,N')(2) (5) with cis-oriented NCS groups and trans-disposed oxazolines. Calculations at the PM3(tm) level of theory suggest that this isomer is close in energy to the four other possible (gas-phase) isomers. Treatment of ethanol solutions of hydrated cobaltous nitrate with excess 1 yields a material analyzed as [Co(NO3)(1)(H2O)(2)](NO3) (6a) and a small amount (less than 1%) of a second complex (6b); the latter has been characterized (X-ray) as the hydrated octahedral complex [Co(NO3-kappa(1)-O)(1-kappa(2)-N,N')(2)(OH2)](NO3). In this case, the nitrato and aqua groupings are located cis to one another and trans to the coordinated -NH2 groups. Complex 6a is surmised to have a [Co(NO3-kappa(2)-O,O')2(1-kappa(2)-N,N')(OH2)(2)] NO3 structure. Cobalt compounds 2-5 and 1 have also been screened for their antifungal properties against Aspergillus niger, Aspergillus flavus, Candida albicans, and Saccharomyces cerevisiae but were found to be inactive in this regard.