Abstract: | The complexes [Co(CNCMe3)3{P(C6H4NMe2-p)3}2](ClO4)2 and [Co(CNCMe3)3{P(C6H4NMe2 -p)3}2]ClO4 are reported. The Co(II) complex, formed by reaction of excess triarylphos-phine with the alkylisocyanide Co(II) complex, is stable and the favoured product. The Co(I) complex, formed by hydrazine reduction of the Co(II) complex, has limited stability in solution, readily oxidizing to the Co(II) species. Upon prolonged irradiation of the Co(II) complex in acetone, [Co{OP(C6H4NMe2-p)3}4](ClO4)2 is produced. |