A 'sting' On Grubbs' Catalyst: An Insight Into Hydride Migration Between Boron And A Transition Metal

摘要

An unusual ruthenium(Ⅱ) complex frozen at an intermediate point of hydride transfer between boron and ruthenium centres is reported.rnThe advent of a new generation of scorpionate ligand, Tm, containing N-methyl-2-mercaptoimidazol-1-yl, mt rings (Fig. 1), first reported by Reglinski et al., added a further dimension to the chemistry of Trofimenko's ubiquitous ligands. This new scorpionate introduced flexibility and so the potential for activation at the boron bridgehead. Organometallic complexes containing this ligand, studied by Hill et al., showed the 'sting of the scorpion' in which the ligand undergoes a boron-to-metal hydride shift and elimination of an organic fragment (R-H, R = vinyl or aryl). This reaction led to the first metallaboratrane complex [Ru{κ~4-B,S,S,S-B(mt)_3}(CO)(PPh_3)] (1), and conclusive proof of the elusive Z-type (σ-acceptor) borane coordination to transition metals (Fig. 1).rnHill et al. and others have since developed a wide range of metallaboratranes based on Tm and derivative ligands. Despite this, there is still little evidence concerning the pathway(s) involved in the hydride migration step or why migration is not observed in some instances.