Synthesis and Characterization of Mononuclear, Pseudotetrahedral Cobalt(III) Compounds

Abstract

The preparation and characterization of two mononuclear cobalt(III) tropocoronand complexes, [Co(TC-5,5)](BF[subscript 4]) and [Co(TC-6,6)](BPh[subscript 4]), are reported. The cobalt(III) centers exist in rare pseudotetrahedral conformations, with twist angles of 65° and 74° for the [Co(TC-5,5]+ and [Co(TC-6,6)]+ species, respectively. Structural and electrochemical characteristics are compared with those of newly synthesized [Ga(TC-5,5)](GaCl[subscript 4]) and [Ga(TC-6,6)](GaCl[subscript 4]) analogues. The spin state of the pseudotetrahedral [Co(TC-6,6)](BPh[subscript 4]) compound was determined to be S = 2, a change in spin state from the value of S = 1 that occurs in the square-planar and distorted square-planar complexes, [Co(TC-3,3)](X) (X = BPh[subscript 4], BAr′[subscript 4]) and [Co(TC-4,4)](BPh[subscript 4]), respectively.