Azolyl complexes bonding

Anion displacement of halides with azolyl anions is one common route to azolyl complexes. One example of such a synthesis is shown in Equation 4.21. In other cases, azolyl complexes have been prepared by proton transfer between the free azole and a metal alkox-ide or hydroxide. An example involving the synthesis of palladium-azolyl complexes is shown in Equation 4.22. In some rare cases, reactions of pyrrole and d early metal alkyls also lead to the formation of a metal-nitrogen bond via o-bond metathesis, as shown in Equation 4.23. Finally, several late-transition-metal-azolyl complexes possessing accompanying hydride Hgands have been prepared by N-H activation of pyrrole and other azoles. 

In their initial attempts to prepare classical chelate complexes containing TmMe, Hill and co-workers155 have encountered an unprecedented class of reaction for tris(azolyl)borate, namely the intramolecular activation of the bridgehead B—H bond which provides the first example of a metallaboratrane. The reaction of TmMe with [Ru(R)ClCOPPh3] (CH=CHCPh2OH) likely yield... 

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