A new entry into ferraborane chemistry: synthesis and characterization of heteroferraborane complexes

Abstract

Reaction of [CpFe(CO)₂I], 1 (Cp = η⁵-C₅H₅) and di(organyl)dichalcogenides, E₂R₂ (E = S, Se; R = Ph, CH₂Ph, 2,6-(tBu)₂-C₆H₂OH) with [LiBH₄·thf] at −70 °C in toluene, followed by stirring at room temperature for 18 h yielded heteroferraboranes, [CpFe(CO)B₂H₄ (μ-L)], 2–4 (2: L = SePh; 3: SeCH₂Ph and 4: S(2,6-(tBu)₂-C₆H₂OH). Compounds 2–4 are highly unstable and concurrent lose of boron atoms yielded organochalcogenolato-bridged complexes, [CpFe(CO)(μ-L)]₂, 5–7, respectively (5: L = SePh; 6: SeCH₂Ph and 7: S(2,6-(tBu)₂-C₆H₂OH). In contrast, the reaction of 1 with di(2-furyl)ditelluride, (C₄H₃O)₂Te₂, yielded organotellurato-bridged complex, [CpFe(CO)(μ-TeC₄H₃O)]₂, 8 and all of our attempts to isolate the boron precursor [CpFe(CO)B₂H₄ (μ-TeC₄H₃O)] in pure form failed. The accuracy of these predictions in each case is established by IR, ¹H, ¹¹B, ¹³C, ⁷⁷Se, ¹²⁵Te NMR and mass spectrometry and complex 8 is further structurally confirmed by X-ray crystallography.