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The synthesis and characterization of tridentate polypyrazolylgallate and borate ligands and their transition metal derivatives

University of British Columbia

The anionic tridentate chelating ligands [MeGa(pz)₃]⁻, [MeGa(dmpz)₃]⁻, and [MeGa(mpz)₃]⁻ have been synthesized and their coordinative properties studied. The [MeGa(pz)₃]⁻ ligand acts as a six-electron chelating ligand to divalent transition metal ions giving complexes of the type [MeGa(pz)₃]₂M (M=Mn,Co,Ni,Cu,Zn), believed to possess an octahedral MN₆ core. The ligand also forms numerous carbonyl complexes with Mn, Mo and W. The tridentate chelating nature of this new ligand has been demonstrated through a crystal structure determination of the complex [MeGa(pz)₃]Mo(CO)₂(n³-C₃H₅). The [MeGa(dmpz)₃]⁻ ligand also forms carbonyl complexes of Mn, Mo and W. The ready conversion of this ligand to the less sterically demanding tris-chelating "hydroxy" ligand [MeGa(dmpz)₂(OH)]⁻ occurs in the attempted synthesis of "n³-allyl" complexes [MeGa(dmpz)₃]M(CO)₂ " n³-allyl" (where M=Mo or W, "n³-allyl"=n³-C₅H₅, n³-C₄H₇). The tridentate chelating nature of this "hydroxy" ligand is conclusively demonstrated in the crystal structure determination of the complex [MeGa(dmpz)₂(OH) ]Mo(C0)₂(n³-C₄H₇) . The [MeGa(mpz)₃]⁻ ligand forms transition metal complexes of the type [MeGa(mpz)₃]₂M (M=Co,Ni) and also carbonyl complexes of Mo and W. Less definitive results were obtained with this ligand, as characterization of the resulting complexes was complicated by the inability to separate the isomers possible for each complex The synthesis of the [H₂B(OCH₂CH₂NR₂)(pz)]⁻ (R=H, Me) ligands and their reaction with divalent transition metal ions is also described. In this case, the only products isolated were the previously characterized [H₂B(pz)₂]₂M and [HB(pz)₃]₂M (M=Co,Ni, Cu,Zn) complexes. Finally, details of the synthesis and characterization of the [R₂Ga(CH₃C0₂)] and [R₂Ga(C₄H₈NC0₂)] (R=Me,Et) compounds are given. The crystal structure of the [Me₂Ga(C₄H₈NC0₂)] derivative consisted of monomeric units linked to two others by weak Ga-0 bonds to form a chain-like polymeric structure. The gallium atom in this compound is five-coordinate and has distorted trigonal bipyramidal geometry.

Text

2010-02-25

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http://hdl.handle.net/2429/20938

Chemistry

University of British Columbia

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