Stibines (SbR3) and bismuthines (BiR3) are the heavier Group 15 analogues of the very widely studied phosphine ligands. Although they are generally regarded as weaker donor ligands, stibines and bismuthines confer a number of interesting features that are not seen in the lighter analogues. Developing the chemistry of these relatively little studied compounds is one of our research themes.
Our recent work on developing new organo-stibine and organo-bismuthine ligand chemistry has revealed that these compounds, unlike their very widely studied lighter phosphine counterparts, can function simultaneously as both donors (towards metal cations) and acceptors (from adjacent Lewis bases) (Coordination Chemistry Reviews 2015, 297-298, 168; doi:10.1016/j.ccr.2015.02.003; Organometallics, 2012, 31, 1025; doi:10.1021/om2010996; Organometallics, 2011, 30, 895; doi:10.1021/om1010148).
This ‘hypercoordination’ leads to distinctly different chemical behaviours and reactivities; current work in the group is exploring the properties, reaction chemistry and the electronic structures and bonding present in these very unusual systems.
More recent work produced the very unexpected dark purple complex [Pd4(µ3-SbMe3)4(SbMe3)4], obtained from [Pd2Cl4(SbMe2Cl)4] and 8 equivalents of MeLi in thf (), containing a Pd4 tetrahedron with each palladium carrying a terminal SbMe3 and with one SbMe3 ligand capping each triangular face – a bonding mode unprecedented for SbMe3.
![Crystal structure of [Pd4(µ3-SbMe3)4(SbMe3)4], showing the triply-bridging SbMe3¬ ligands](https://cdn.southampton.ac.uk/assets/imported/transforms/content-block/CB_RImg/B1AF4E1DFE3C4B0CA1C6EE05BF0E894A/chenm.jpg_SIA_JPG_fit_to_width_INLINE.jpg)