UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Transition metal derivatives of asymmetric pyrazolylgallate ligands Chong, Kenneth Samuel


The reaction of sodium pyrazolide or sodium 3,5-dimethyl-pyrazolide with trimethyl gallium followed by reaction of the resultant adduct with 'ethanolamine' produces novel asymmetric tridentate ligands which are capable of either meridional or facial coordination in transition metal complexes. Na⁺('pz')⁻ + Me₃Ga THF> Na⁺[Me₃Ga ('pz’) ] ⁻ Na⁺[Me₃Ga ('pz’) ] ⁻+ R’ ₂NCH₂CH₂OH₂ > Na⁺L⁻ + MeH With R' = H, these ligands react with divalent transition metal ions to give octahedral bis-ligand complexes. However with R’ = Me, reaction with divalent transition metal ions produced either trigonal bipyramidal (R = Me) or binuclear five-coordinate (R = H) complexes. The asymmetric chelating gallate ligands reacted with Mn(CO)₅Br to give LMn(CO)₃ and with appropriate Gp VI carbonyl derivatives to give LM(CO)₃⁻ ( M = Cr, Mo, W). The carbonyl anions were found to be stereochemically non-rigid in solution and a mechanism for the fluxional process is proposed. Reaction of LM(CO)₃⁻(M = Mo, W) with various three-electron ligands gave derivatives of the form, LM(CO)₂T (T = NO, N₂Ph, C₃H₅ C₄H₇, C₇H₇, and CH₂SMe). A similar fluxional process (to that found in the carbonyl anions) was found in the complex, [Me₂Ga(pz)(OCH₂CH₂NH₂)] Mo(CO)₂(n³ -C₄H₇). In addition, the cycloheptatrienyl derivatives were found to be fluxional as a result of a rapidly rotating C₇H₇ ring. Depending on the nature of T, the LM(CO)₂T derivatives can exhibit both positional and conformational isomerism and this subject is discussed in detail. Reaction of Na⁺L⁻ (R = R'= Me) with Ni(NO)I and Cu(PPh₃)Br gave LNi(NO) and LCu(PPh₃) respectively. Both of these molecules were found to be fluxional in solution and a similar mechanism to that proposed for the Gp VI carbonyl ions is invoked to explain these fluxional processes. The compounds, LMn(NO)₂ and LFe(NO)₂ (19-electron) were prepared by reaction of Na+L- (R = R'= Me) with appropriate metal dinitrosyl precursors.and are the first of their type to be synthesized. Finally, reaction of Na+L- (R = R'= Me) with Mo(NO)₂Cl₂ gave LMo(NO)₂Cl. In additon to studies involving the ligand L, the pyrazolyl bridged dimers [Ni('pz’)(NO)]₂, [Fe('pz')(NO)₂]₂ and [Co('pz')(NO)₂]₂ were prepared and their reactivity towards nucleophiles studied. The π-allyl compounds [Me₂Ga (pz" )₂]M (C₃H₅) (M = Ni or Pd) and [Ni (pz") (C₃H₅) ]"₂were also prepared. All the prepared compounds were systematically characterized with uv-vis, ir and XH nmr spectroscopy as well as mass spectrometry. In addition, x-ray studies were carried out (by Dr. S. Rettig) on several of the prepared compounds and these data are correlated with other physical measurements.

Item Media

Item Citations and Data


For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.