Cluster versus coordination: the chemistry of cyclopentadienyl titanium and vanadium complexes with B- and C-functionalized carborane-thiols, [C2B10H12−n(SH)n] (n = 2 or 3)

Abstract

A series of B- and C-functionalized di- and trithiol chelating o-carborane ligands have been employed to explore the coordination chemistry with cyclopentadienyl titanium and vanadium complexes. Treatment of [Cp*TiCl₃] with [LiBH₄·THF], followed by thermolysis with a C-functionalized carborane-dithiol ligand [1,2-(SH)₂-1,2-C₂B₁₀H₁₀], yielded octacapped octahedral [(Cp*Ti)₄{Ti(1,2-(S)₂-1,2-C₂B₁₀H₁₀)}₂(μ₃-S)₆(μ₃-O)₂] (1) and hexacapped trigonal bipyramidal [(Cp*Ti)₄{Ti(1,2-(S)₂-1,2-C₂B₁₀H₁₀)}(μ₃-S)₆] (2) clusters. One of the driving forces of these reactions is the cleavage of C–S bonds of carborane-dithiols that resulted in sulfide ligands and subsequently generated clusters 1 and 2. In contrast, a similar reaction with a B-functionalized carborane-dithiol [9,12-(SH)₂-1,2-C₂B₁₀H₁₀] led to B–B bond formation that yielded a κ²-hydridoborato complex, [(Cp*Ti){κ²-BH₃(9,12-(S)₂-1,2-C₂B₁₀H₁₀)}] (3). To the best of our knowledge, complex 3 is the first example of a carborane-dithiol functionalized hydridoborato complex. Interestingly, when the reactions of [Cp*TiCl₃] or [Cp₂TiCl₂] were carried out with a B-functionalized carborane-trithiol, [8,9,12-(SH)₃-1,2-C₂B₁₀H₉], they led to coordination complexes, [(Cp/Cp*Ti){8,9,12-(S)₃-1,2-C₂B₁₀H₉}] (Cp* (4a) and Cp (4b)). Similarly, when [(Cp*VCl₂)₃] was employed as a metal precursor, deboronation was observed at the icosahedral cage that resulted in a zwitterionic complex, [(Cp*V){1,5,6-(S)₃-nido-7,8-C₂B₉H₉}] (5). All the clusters have been characterized by NMR, IR, mass spectrometry, and X-ray diffraction analysis. Furthermore, the theoretical analyses provided valuable insights into the electronic structures of these unusual clusters.