Synthesis and characterization of multinuclear titanium and vanadium complexes: Magnetostructural investigations.

摘要

The purpose of this dissertation is the synthesis and characterization of multinuclear V{dollar}sp{lcub}rm III{rcub}{dollar} and Ti{dollar}sp{lcub}rm III{rcub}{dollar} complexes with a variety of coordination environments. The studies focus on synthesis, X-ray structural characterization, solid-state magnetic susceptibility, and paramagnetic NMR experiments.; Ambient temperature syntheses have been developed for the preparation of (NEt{dollar}sb4rbracksb3{dollar} (V{dollar}sb2{dollar}Cl{dollar}sb9{dollar}) and (NEt{dollar}sb4rbracksb3{dollar} (Ti{dollar}sb2{dollar}Cl{dollar}sb9{dollar}) in high yield and purity by reaction of MCl{dollar}sb3{dollar}(thf){dollar}sb3{dollar} with Cl{dollar}sp-{dollar}. The complexes were structurally characterized and examined by magnetic susceptibility techniques. Both complexes possess a face-sharing bioctahedral structure and exhibit antiferromagnetic interactions between the metal centers; the exchange parameters are J = {dollar}-{dollar}171 cm{dollar}sp{lcub}-1{rcub}{dollar} and J = {dollar}-{dollar}15 cm{dollar}sp{lcub}-1{rcub}{dollar} for Ti and V, respectively. A novel trapped valent Ti{dollar}sp{lcub}rm III{rcub}{dollar}Ti{dollar}sp{lcub}rm IV{rcub}{dollar} complex was synthesized by reaction of TiCl{dollar}sb3{dollar}(thf){dollar}sb3{dollar} with HO{dollar}sb2{dollar}CPh. The complex (Ti{dollar}sb2{dollar}O(O{dollar}sb2{dollar}CPh){dollar}sb2{dollar}Cl{dollar}sb3{dollar}(thf){dollar}sb3{dollar}) has an asymmetric oxide bridge exhibiting single bond/triple bond ligation to the Ti ions.; General methods for the syntheses of vanadium(III)/oxo/carboxylate complexes have been developed; the trinuclear (V{dollar}sb3{dollar}O(O{dollar}sb2{dollar}CR){dollar}sb6{dollar}(L){dollar}sb3{dollar}) (ClO{dollar}sb4{dollar}) and new tetranuclear (V{dollar}sb4{dollar}O{dollar}sb2{dollar}(O{dollar}sb2{dollar}CR){dollar}sb7{dollar}(L-L){dollar}sb2{dollar}) {dollar}sp{lcub}pm{rcub}{dollar} (R = alkyl, aryl; L = nitrogen donor) complexes were characterized in solution ({dollar}sp1{dollar}H NMR, electrochemistry, UV-vis) and in the solid state (X-ray diffraction and magnetic susceptibility). They contain a triangular (V{dollar}sb3(musb3{dollar}-O)) and butterfly-like (V{dollar}sb4(musb 3{dollar}-O){dollar}sb2{dollar}) core, respectively. In these complexes, a {dollar}pi{dollar}-contact spin-delocalization mechanism has been determined to be responsible for the observed isotropic shifts of the ligand protons in the NMR spectra. Antiferromagnetic exchange interactions in (V{dollar}sb3{dollar}O(O{dollar}sb2{dollar}CMe){dollar}sb6{dollar}(py){dollar}sb3{dollar}) (ClO{dollar}sb4{dollar}) (J = {dollar}-{dollar}18.0, {dollar}Jspprime{dollar} = {dollar}-{dollar}10.4 cm{dollar}sp{lcub}-1{rcub}{dollar}) lead to an S = 0 ground state, while ferromagnetic interactions dominate in (V{dollar}sb4{dollar}O{dollar}sb2{dollar}(O{dollar}sb2{dollar}CEt){dollar}sb7{dollar}(bpy){dollar}sb2{dollar}) (ClO{dollar}sb4{dollar}) ({dollar}Jsb{lcub}wb{rcub}{dollar} = 27.5, {dollar}Jsb{lcub}bb{rcub}{dollar} = {dollar}-{dollar}31.2 cm{dollar}sp{lcub}-1{rcub}{dollar}) to give an S = 3 ground state.; The magnetic properties of previously-prepared (NEt{dollar}sb4rbracksb3{dollar} (V{dollar}sb3{dollar}(edt){dollar}sb3{dollar}Cl{dollar}sb6{dollar}) and (V{dollar}sb4{dollar}O{dollar}sb4{dollar}Zn{dollar}sb4{dollar}(O{dollar}sb2{dollar}CPh){dollar}sb{lcub}12{rcub}{dollar}(thf){dollar}sb4{dollar}) have also been examined. Fitting of the magnetic data for (NEt{dollar}sb4rbracksb3{dollar} (V{dollar}sb3{dollar}(edt){dollar}sb3{dollar}Cl{dollar}sb6{dollar}) gave J = 42.5 and {dollar}Jspprime{dollar} = {dollar}-{dollar}1.8 cm{dollar}sp{lcub}-1{rcub}{dollar}, where J and {dollar}Jspprime{dollar} represent the magnetic interactions between adjacent and terminal V{dollar}sp{lcub}rm III{rcub}{dollar} atoms, respectively. The tetranuclear mixed-metal complex has an