text: The Tm anion is a tridentate, tripodal ligand topologically similar to the more common Tp ligands, but the two classes of ligands differ in several ways. Tm has three "soft" sulfur donor atoms, whereas Tp has three nitrogen donor atoms. The thioamide sulfur is highly basic, as found for other thioureas. The Tm anion simulates the environment provided by three facial thiolate ligands but without the 3- charge of a facial trithiolate.
  The large 8-membered SCNBNCSM chelate rings in M(Tm) complexes are more flexible than the 6-membered CNBNCM rings in M(Tp) complexes.  This flexibility enables the formation of boron-metal bonds, after loss of the B-H bond.  This degradation of the coordinated Tm anion gives a dehydrogenated boranamide B(mt) where mt = methimazolate.