The recently synthesized 3-tert-butyl-5-methyl-1,2,4-triazole reacted with KBH4 to give the new potassium tris(3-tert-butyl-5-methyl-1,2,4-triazolyl)borate K(Ttz(tBu,Me)) ligand. Ttz(tBu,Me) formed a four-coordinate (Ttz(tBu,Me))CoCl complex and five-coordinate (Ttz(tBu,Me))CoNO3 and (Ttz(tBu,Me))ZnOAc complexes. When these complexes were compared to their Tp(tBu,Me) analogues, it was found that Ttz(tBu,Me) resulted in negligible steric differences. K(Ttz(tBu,Me)) is more water-soluble than K(Tp(tBu,Me)), so bulky tris(triazolyl)borate ligands should lead to functional models for enzyme active sites in an aqueous environment and the creation of water-soluble analogues of Tp catalysts.

Ligands of intermediate steric bulk were designed to mimic metalloenzymes with histidine and carboxlyate binding sites. The reaction between tris(3-isopropylpyrazolyl)methane and butyllithium followed by SO3NMe3 in THF yielded the new ligand lithium tris(3-isopropylpyrazolyl)methane sulfonate (LiTpmsiPr). Various metal salts reacted with LiTpmsiPr to give the octahedral complexes M(TpmsiPr)2 (M = Zn, Cu, Ni, Co, Fe) in which each ligand has N,N,O binding to the metal. In the reaction between LiTpmsiPr and ZnCl2, in addition to the major product Zn(TpmsiPr)2, [LiTpmsiPrZnCl2].2THF was also formed as a minor product with a tetrahedral zinc atom coordinated to either N,N,Cl,Cl in the solid phase or N,N,N,Cl in acetonitrile solution. Although TpmsiPr is coordinatively flexible and can act as a bipodal or tripodal ligand, it appears to favor the formation of octahedral L2M complexes.