Hydrotris borate, reaction with

Trispyrazolylborates are models for tris-histidine active sites in zinc enzymes, e.g., the matrix metalloproteinases involved in breakdown of extracellular matrices. Inhibition of these metalloproteinases may prove valuable in the treatment of, inter alios, cancer and arthritis, so efforts are being made to find appropriate ligands to block the zinc active site. The search has recently moved on from hydroxamates to hydroxypyridinones - l-hydroxy-2-pyridinone is a cyclic analogue of hydroxamic acid. As reported in Section II.B.2 earlier, hydroxypyridinones form stable five-coordinate complexes on reaction with hydrotris(3,5-phenylmethylpyrazolyl)borate zinc hydroxide. Modeling studies suggest that hydroxypyridinonate ligands should be able to access the active site in the enzyme with ease (110). 

Rhenium(V) 4-tolylimido complexes with the hydrotris(pyrazolyl)borate ligand, HB(pz)3, are formed on heating the 0x0 derivatives [ReOX2 HB(pz)3 ] (X = Cl, I) with 4-toluidine, whereas reactions with amines at ambient temperatures only give 0x0 complexes of the composition [ReO(NHR)Cl HB(pz)3 ]. The [Re(NC6H4-4-Me)X2 HB(pz)3] complexes react with ZnEt2 with formation of imido-ethyl complexes of the composition [Re(NC6H4-4-Me)Cl(Et) HB(pz)3 ]. " ... 

Hydrotris(l,2,4-triazolyl)borate organic salts (imidazolium, tria-zolium, and tetrazolium) were synthesized in high yield by metathesis reaction with [Ag HB(tz)3 ]. These borate salts melt at relatively low temperature to give thermally stable ionic liquids.246... 

---