Transition Metal Borate Complexes Containing κ0-κ6 Denticity of Scorpionate Borate Ligands

The recent developments in the field of transition metal (TM) borate complexes have been a landmark in modern coordination chemistry. The structural diversities of these complexes play an important role in several catalytic processes. Generally, polypyrazolyl borate ligands, [BHn(pz)(4-n)](-) (n=1, 2; pz=pyrazolyl), popularly known as scorpionates have been used extensively for the preparation of TM borate complexes. The presence of multiple donor atoms in the flexible borate proligands led to several coordination modes. Based on the electronic and steric properties of these ligands and the metals, the denticity of borate ligands in TM complexes varied from kappa(0) to kappa(6). The presence of different bonding modes of these borate ligands made them very interesting in main group organometallic chemistry. In addition, cooperative activation of boranes by TM complexes containing metal-nitrogen or metal-sulfur bonds has become an alternative to the utilization of borate proligands for the synthesis of TM borate complexes. This review summarizes the advancements of the chemistry of TM borate complexes focusing exclusively on the synthetic methods and various bonding scenarios.

Automated summary

The recent developments in the field of transition metal borate complexes have had a significant impact on modern coordination chemistry. These complexes exhibit structural diversities that are crucial in numerous catalytic processes. Polypyrazolyl borate ligands, commonly known as scorpionates, have been extensively used in the preparation of transition metal borate complexes. The presence of multiple donor atoms in the flexible borate proligands leads to various coordination modes. The denticity of borate ligands in these complexes ranges from kappa(0) to kappa(6), depending on the electronic and steric properties of the ligands and the metals. The different bonding modes of these borate ligands make them highly interesting in main group organometallic chemistry. Additionally, the cooperative activation of boranes by transition metal complexes containing metal-nitrogen or metal-sulfur bonds has emerged as an alternative synthetic route for transition metal borate complexes. This review summarizes the progress in the chemistry of transition metal borate complexes, focusing on synthetic methods and bonding scenarios.