Synthesis, structure, spectroscopic and electrochemical study of the paramagnetic compound [2-(η7-C7H7)-7,11-F2-2,1-closo-MoTeB10H8]

Abstract

The reaction of [NEt₄][7-nido-TeB₁₀H₁₁] 1 with [Mo(CO)₃(η⁷-C₇H₇)][BF₄] 2 in dichloromethane yields the novel paramagnetic, B-fluorinated, “mixed-sandwich” compound [2-(η⁷-C₇H₇)-7,11-F₂-2,1-closo-MoTeB₁₀H₈] 3 in 19% yield. An X-ray diffraction study of 3 establishes the closo twelve-vertex MoTeB₁₀-cage structure with two B–F units at adjacent positions. The structure of 3 was solved in space group Pna2₁ with unit cell dimensions of a = 16.7598(18), b = 12.5500(11), c = 7.2607(18) Å, and Z = 4. The final R factor was 0.0291 for 1471 observed reflections. Principal interatomic distances are Mo–Te 2.7083(8), B–F 1.396(9) and 1.410(9) Å. In the MoTeB₁₀ cage interatomic distances are in the ranges; Mo–B 2.363(8) to 2.481(9), Te–B 2.293(9) to 2.373(9) and B–B 1.720(13) to 1.943(12) Å. EPR spectra confirm the paramagnetic nature of 3 with the unpaired electron located in a mainly molybdenum-based molecular orbital. The cyclic voltammetric response of 3 exhibits a reversible one-electron reduction at E^0′ = −0.39 V in dichloromethane solvent.