Organoborate species are key transient intermediates in cross-coupling reactions that act as nucleophiles in the synthesis of both organic and organometallic compounds. The organoborates also serve as counter anions on quaternary nitrogen-containing compounds of which azolium salts are examples. However, the basic chemistry the borate ions on the azolium salts could perform during metalation has been overlooked when it comes to the synthesis of NHC carbene complexes. Therefore, 1,3-bis(3’-butylimidazol-1’-yl) benzene bis-tetraphenylborate salt was employed to study the effects of tetraphenylborate ions on Zr(NMe2)4 based metalation to synthesize CCC-NHC Zirconium (IV) pincer complexes. The reaction was done using a stoichiometric amount of the Zr(NMe2)4 and in excess. A trigonal bipyramidal CCC-NHC Zr(IV) pincer complex was obtained in good yield using 1 equivalent of the Zr(NMe2)4. The BPh4- counter ions on the salt underwent transmetalation when a stoichiometric amount of the Zr(NMe2)4 was used to obtain the NHC borane adduct. Attempt to synthesize coordinatively saturated octahedral mono amido diphenyl Zr(IV) pincer complex capitalizing on the fact that BPh4- ions behave as phenylating species was unsuccessful. A neutral tris-amido CCC-NHC Zr(IV) pincer complex was not obtained when an excess amount of the Zr(NMe2)4 was used but rather gave the trigonal bipyramidal Zr(IV) pincer complex in a quantitative yield.

Probing the influence of the counter ion in the synthesis of CCC-NHC Zr(IV) pincer complexes: Tetraphenylborate

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