Isometallocenes. Part 1. Polymethylated isocobaltocenium salts; a general route to [Co(C₄Me₄)(arene)]

(Tetramethylcyclobutadiene)cobalt Complexes − Syntheses of Tris(ligand) Derivatives and Structures of [(C4Me4)Co(CO)3]BF4 and [(C4Me4)Co(NCMe)3]PF6

“…In the work of Pauson et al [16] the salt [Cb*Co(CO) 3 ]PF 6 (5) was isolated from the reaction of Me 4 C 4 AlCl 3 [17] and Co 2 (CO) 8 . In a second step, this salt was treated with Me 3 NO/Bu 4 NI in dichloromethane or with K 2 CO 3 /Bu 4 NI in dichloromethane to afford the iodide 2.…”

“…In a further transformation the iodide 2 was heated with AlCl 3 in benzene, and the resulting cation 3 ϩ was isolated as hexafluorophosphate 6 [ϵ (3)PF 6 ]. [16] In part of our work we used the tetrafluoroborate 7 [ϵ (1)BF 4 ] which was synthesized by a straightforward adaptation of the published synthesis of the hexafluorophosphate 5. The iodide 2 was prepared by a simplified procedure that combines the two steps of the original work into a single protocol.…”

“…The yield of 6 varies somewhat erratically between 50 and 80% (ref. [16] 25%), presumably because traces of water seem to be favorable while larger amounts of water are detrimental.…”

“…The first substitution step has already been described by Pauson et al [16] to give the red salt [Cb*Co(CO) 2 (NCMe)]BF 4 (17). Irradiation of an acetonitrile solution of 7 effects a slow second substitution and affords mixtures of 17 and the disubstitution product [Cb*Co(CO)(NCMe) 2 ]BF 4 (18).…”

“…There are several general reviews on (cyclobutadiene)metal complexes, [14] and also specialized reviews that center on the chemistry of (cyclobutadiene)cobalt complexes. [15] In pioneering work Pauson et al [16] have shown that the zwitterionic cyclobutenyl species Me 4 C 4 AlCl 3 [17] readily re-(Tetramethylcyclobutadiene)cobalt Complexes…”