Trispyrazolylborate ligands bonding

Copper and silver complexes bearing trispyrazolylborate ligands have shown catalytic activity towards several organic transformations involving the functionalization of unsaturated carbon-carbon bonds or several saturated E—H bonds, particularly of carbon-hydrogen bonds. The tunability of this class of ligands from both steric and electronic perspectives allows the control of those catalytic capabilities. On the basis of the work already described, the potential for their use on other, yet unreported transformations seems feasible. 

There is just one example of a nonsubstituted pyridyHdene complex obtained as a 1 1 mixture together with the N-adduct (Scheme 27). This outstanding transformation was mediated by an iridium complex featuring two Ir-CH2 bonds that resulted from the metaUation of two methyl groups of mesityl substituents of the trispyrazolylborate ligand (Tp = hydrotris(5-mesitylpyrazolyl)borate). The presence of an Ir-CH2 bond within a chelate is essential for the tautomerization process. 

Only a handful of pseudotetrahedral or octahedral oxosulfido-Mo(VI) and -Mo(V) complexes are known, and their chemistry is described in Section 11. Mononuclear sulfido-Mo(V) complexes are unstable due to their susceptibility to redox, polynucleation, and hydrolysis reactions. Trispyrazolylborate derivatives such as sfructuraUy characterized Tp Mo SX2 (X = Cl, OPh derivative X2 = bdt, catecholate) are most commonly encountered. The Tp complexes exhibit short Mo=S bonds (ca. 2.13 A), intense S(ls)- - n (Mo=S) XAS transitions characteristic of terminal thio ligands, and EPR iso see g-Factor) values substantially lower than their 0x0 analogues. ... 

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