Hypoelectronic titanaboranes: icosahedral and tetracapped tetrahedral clusters comprising bridging hydrides.

Unusual hypoelectronic -clusters, such as icosahedral [(CpTi)(BH)(μ-H)(μ-Cl)] (1) and tetracapped tetrahedral [{(CpTi)B}(μ-BH)(μ-Te)] (2), have been synthesized and structurally characterized. Clusters 1 and 2 represent the first examples of -titanaboranes having bridging hydrides, where the Ti⋯Ti interactions play a pivotal role in defining their shapes and electron counts. Furthermore, two face-fused clusters, [(Cp*Ti)(μ-Se)(μ-SePh)(μ-η:η-BHR)] (3a: R = H; 3b: R = Ph), have been isolated that deviate from Mingos fusion formalism.