Reductive dimerization of [Mo(C6F5)(CO)2(η-C7H7)]. Synthesis and characterization of the bitropyl complex [{Mo(C6F5)(CO)2}2(η6:η′6-C14H14)]2–

Abstract

The complex [Mo(C₆F₅)(CO)₂(η-C₇H₇)]1 can be reduced either chemically or electrochemically (E_pc=–2.07 V vs. ferrocenium-ferrocene) by one electron to produce the bitropyl (bicycloheptatrienyl) complex [{Mo(C₆F₅)(CO)₂}₂(η⁶:η′⁶-C₁₄H₁₄)]^2–2^2–. The sodium salt produced by Na(Hg) reduction of 1 in tetrahydrofuran is extremely air sensitive, but replacement of the Na⁺ cations with [N(PPh₃)₂]⁺ yields a much more stable salt. With either counter ion, the complex 2^2– exists in solution as a mixture of three isomers: endo-endo; endo-exo; and exo-exo. The complex has been fully characterized by IR, ¹H and ¹³ C NMR spectroscopy, elemental analysis and a crystal structure of the endo-endo isomer of the [N(PPh₃)₂]⁺ salt. Oxidation of the bitropyl complex rapidly cleaves the bridging C–C bond and returns complex 1.