CYCLOPENTADIENYLCOBALT COMPLEXES OF SOME AZEPINES

The complexes [(C(5)R(5))Co(2-5-eta-C(6)H(6)NR')] (R' = C(O)OEt; R = H (6a) or Me (9a)) are prepared from N-ethoxycarbonyl azepine and [(C(5 )R(5))Co(C2H4)(2)] (R = H (5) or Me (8)). On treatment with methoxide ion, 6a is partially converted into the N-methoxycarbonyl derivative 6 b. Complex 9a can be reduced with LiAlH4 to give the N-methyl derivati ve 9b. Complexes 6a, 9a and 9b were shown to be fluxional in solution. The complexes undergo a degenerate valence tautomerization, which is much more facile in 9b than in 6a and 9a. Restricted rotation around t he N-C(O) bond was found in 6a, leading to the presence of two diaster eomers at low temperatures. No dinuclear azepine-bridged complexes wer e obtained from 6a, 9a and 9b after treatment with 5 or 8.