Metallaborane chemistry. Part 12. Electron hyper-deficient carbametallaboranes containing iron–iron, iron–cobalt, and iron–platinum connectivities: molecular and crystal structure of [CoFe(Me4C4B8H8)(PEt3)2]

Abstract

The dihydridocarbaferraborane [FeH₂(2,3-Me₂-2,3-C₂B₄H₄)₂] reacts with [Co(PEt₃)₄], [Pt₂(µ-cod)(PEt₃)₄](cod = cyclo-octa-1,5-diene), and [Fe(cod)(η-C₅H₅)] to afford, respectively, the dimetallic species [CoFe( Me₄C₄B₈H₈)(PEt₃)₂], [FePt(Me₄C₄B₈H₈)(PEt₃)₂], and [Fe₂(Me₄C₄B₈H₈)(η-C₅H₅)], each of which features a metal–metal connectivity. An X-ray diffraction study of the iron–cobalt molecule shows that it belongs to the structural family involving two pentagonal bipyramids fused about a common iron apical vertex and sharing a double-capping BH function. Crystals are orthorhombic, space group P2₁2₁2₁ with a= 16.533(5), b= 11.012(2), c= 16.279(3)Å, and four molecules per unit cell. Using 3 496 amplitudes recorded on a four-circle diffractometer at 291 ± 1 K the structure has been refined to R 0.043. The Co–Fe distance is 2.5300(8)Å; 0.05 Å longer than that in [CoFe(Me₄C₄B₈H₈)(η-C₅H₅)].