The Sting of the Scorpion: A Metallaboratrane.

An unprecedented intramolecular B-H activation of a hydrotris(2-sulfanyl-1-methylimidazolyl)borate ligand coordinated to ruthenium has provided the first example of metallaboratranes. The remarkable ease with which the ruthenaboratrane 1 forms relative to the case with a hydrotris(pyrazolyl)borate ligand is a consequence of the lability of the chelation and the increased ring size of the chelates.