Unexpected Differences in the Coordination Behaviour of 1,2,4-Triphosphaferrocenes towards Cu Chloride

Abstract

The coordination behaviour of 1,2,4-triphosphaferrocenes [FeCpR(5-P3C2tBu2)] [CpR = Cp (1), Cp (2)] towards CuI chloride is significantly influenced by the substitution pattern of the cyclopentadienyl ring attached to iron. The dimeric copper complexes []2 (3) and [(-CuCl)]2 (4), in which two 1,2,4-triphosphaferrocenes are linked by two CuCl centres to form dimeric complexes were obtained in reactions using a 1:1 stoichiometry. Whereas in 3 a tetra-coordinated Cu atom is revealed, 4 possesses a threefold-coordinated Cu atom due to the steric influence of the bulkier Cp ligand. However, if the reaction is carried out with an excess of CuCl in a 1:2 stoichiometry for the Cp derivative 1 the same product 3 is obtained, whereas in the case of a tri-tert-butyl-substituted Cp ligand complex 2 the triphospholyl ring is fragmented under mild conditions to a tetraphosphabutadiene moiety within an iron triple-decker sandwich complex [] (5) embedded in a CuCl polymer matrix.