Chalcogen Stabilized bis‐Hydridoborate Complexes of Cobalt: Analogues of Tetracyclo[4.3.0.0 2,4 .0 3,5 ]nonane

Treatment of Li[BH 3 ER] (E=Se or Te, R=Ph; E=S, R=CH 2 Ph) with [Cp*CoCl] 2 led to the formation of hydridoborate complexes, [{CoCp*Ph}{Cp*Co}{ μ ‐EPh}{ μ ‐ κ 2 ‐E,H‐EBH 3 }], 1a and 1 b ( 1 a : E=Se; 1 b : E=Te) and a bis‐hydridoborate species [Cp*Co{ μ ‐ κ 2 ‐Se,H‐SeBH 3 }] 2 , 2 . All the complexes, 1 a , 1 b and 2 are stabilized by β‐agostic type interaction in which 1 b represents a novel bimetallic borate complex with a rare B−Te bond. QTAIM analysis furnished direct proof for the existence of a shared and dative B‐chalcogen and Co‐chalcogen interactions, respectively. In parallel to the formation of the hydridoborate complexes, the reactions also yielded tetracyclic species, [Cp*Co{ κ 3 ‐E,H,H‐E(BH 2 ) 2 ‐C 5 Me 5 H 3 }], 3 a and 3 b ( 3 a : E=Se and 3 b : E=S), wherein the bridgehead boron atoms are surrounded by one chalcogen, one cobalt and two carbon atoms of a cyclopentane ring. Molecules 3 a and 3 b are best described as the structural mimic of tetracyclo[4.3.0.0 2,4 .0 3,5 ]nonane having identical structure and similar valence electron counts.