Synthesis, structure and bonding of adamantoid complex [{CpFe(CO)}(BH2)3(CH2S2)2] and tetrathiolene complex [(Cp*Ti)2(µ-S2)(µ-C2S4)].

A novel ferrathiaborane having an adamantane-type caged structure has been synthesized and structurally characterized. The room temperature reaction of an intermediate generated from the reaction of [CpFe(CO)2I] (1) and [LiBH4·THF], with excess CS2 resulted in the formation of [CpFe(CO)(BH2)3(CH2S2)2] (3). Complex 3 has an adamantoid structure featuring a {FeB3C2S4} framework. Alternatively, 3 could also be synthesized from the reaction of 1 with heteroadamantane, [(BH2)4(CH2S2)2] (2). To the best of our knowledge, complex 3 is the first example of an adamantoid metallaheteroborane. In an attempt to synthesize a similar metallaheteroborane with an early transition metal fragment, a similar reaction protocol was employed using Cp*TiCl3 (4) instead of 1. This led to the formation of a bimetallic complex, [(Cp*Ti)2(µ-S2-κ2S:κ2S')(µ-C2S4-κ1S:κ1S':κ1S″:κ1S‴)] (5). Complex 5 comprises a tetrathiolene [C2S4]4- ligand and a disulfide [S2]2- ligand that bridges two Cp*Ti fragments in a side-on fashion. Complexes 3 and 5 were characterized by multinuclear NMR and IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction analysis. DFT calculations revealed that the replacement of a {BH2} unit in 2 by a {CpFe(CO)} fragment in 3 decreases the overall stability of the adamantoid framework.