| The natural design of enzymes and proteins inspires synthetic strategies for designing more efficient transition metal catalysts for achieving similar organic transformations.;Novel tris(triazolyl)borate ligands with intermediate steric bulk, tris(3-isopropyl,5-methyl,1,2,4-triazolyl)hydroborate (TtziPr,Me), tris(3,5-diisopropyl,1,2,4-triazolyl)hydroborate (TtziPr2), and tris(3,5-diisopropyl,1,2,4-triazolyl)methane (TtzmiPr2), were synthesized and characterized. These ligands were used to support transition metal complexes: (TtziPr, Me)NiCl, (TtziPr, Me)CuCl, (TtziPr, Me)ZnCl, (Ttz iPr, Me)ZnOAc, (TtziPr, Me)NiCl, (TtziPr2CuCl) 2, (TtziPr2CuOH)2, (TtziPr2)CuOAc, (TtziPr2)CuCO, (TtziPr2)CuNO2, (Ttz iPr2)CuNO3, (TtziPr2)ZnCl, (TtziPr2 )ZnCH2CH3, and (TtzmiPr2)Cu(NO 3)2. These complexes either serve as models of the active-site of metallo-enzymes or as precursors used to achieve the desired mimic.;The modulation of a metallo-enzyme's electronic properties by a network of hydrogen-bonds or protonation/deprotonation events is an important feature regarding its reactivity towards an organic substrate. The Ttz is a unique ligand such that it can model this feature and thus we studied the effects protonation of the Ttz-ligand has on the electronic density of (Ttz R1,R2)Cu(I)CO centers, where the stretching mode of the CO ligand determined by IR was used to assess the change in the electronic properties of the Cu(I)-center upon protonation. Four protonated-states were characterized by deconvolution of the CO spectral features and by DFT calculations.;This concept was applied to studying the reactivity of (TtzR1,R2 )Cu(I/II) complexes towards various organic substrates. (Ttz R1,R2)CuNO2 complexes were synthesized as models for the copper nitrite reductase enzyme. The stoichiometric reduction of nitrite to form NO(g) was studied. [(TtztBu,Me)Cu INO2]-facilitated the stoichiometric reduction of nitrite to generate NO(g) in yields of up to 93% determined by UV-Vis. (TtztBu,Me)CuIINO2 and (Ttz tBu,Me)CuIINO2 in the presence of HBF 4 generated NO(g) in yields of 75% and 90% determined by UV-vis. Additionally, (TtzR1,R2)CuNCCH3 complexes were synthesized as catalysts for C-H activation of cyclohexanes, hexanes, dimethylbutane, and tetrahydrofuran, and % product conversion and TON values increased under acidic conditions determined by 1H-NMR and GC-MS. Furthermore, the steric environment around the Cu-center was determined to influence the catalyst's reactivity towards C-H bonds.;Attempts at synthesizing (TtziPr2)ZnOH and Ttz Ph,MeMoO2Cl as models for carbonic anhydrase and molybdenum-containing enzymes were also made. |
