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Dissertation:
„Lithium, magnesium, zinc and vanadium complexes supported by diaminebis(aryloxido)
ligands – synthesis, characterization and reactivity.”
mgr Ew Kober
Supervisor: dr hab. Zofia A. Janas, prof. UWr.
The main goal of the presented research was the synthesis, structural characterization and
reactivity
of
lithium,
magnesium,
zinc
and
vanadium
complexes
supported
by diaminebis(phenolate) ligands. Three types of tetradentate, dianionic [O,N,N,O] ligands:
tripodal, linear and imidazolidine-bridged have been used to realize the scientific project. Thirty
two
new
metal
complexes
including
seven
lithium,
three
magnesium,
two
zinc
and twenty vanadium were prepared. The solution structure of all complexes were examined
and the solid state structures were determined for twenty of them.
Tripodal diaminebis(phenolate) ligand generates tetra- and hexalithium complexes which
reveal the cube, cube with oxygen bridged on two opposite edges, hexagonal prisms and flexed
ladder-like structures, respectively. Magnesium and zinc complexes bearing tripodal ligands have
dimeric nature while the linear ligands generate trimeric magnesium and dimeric zinc complexes.
Two series of monomeric oxovanadium(V) complexes were obtained and fully
characterized. Complexes possess Cs-symmetry, octahedral geometry around the vanadium centre
and a variety of structural isomers. Tripodal ligands generate in solution trans-1
and trans-2 complexes but in the solid state only trans-1 isomer was isolated. Achiral linear
ligands adopt a cis–α configuration around octahedral vanadium center and form a racemic
mixture of enantiomers with Δ and Λ helicity. Imidazolidenebis(phenol) gives monoand dinuclear okso-vanadium complexes depending on the reaction stoichiometry.
A mixture of mono- and dimeric oxo-vanadium(IV) complexes supported on the linear
ligands were obtained via the reduction of oxo-vanadium(V) compounds by 1-methyl-1phenylhydrazine
(NH2NMePh).
In
protolytic
solvents,
complexes
are
unstable
and
disproportionate to vanadium(III) and oxo-vanadium(V) complexes.
Lithium complexes, in contrast to the magnesium and zinc compounds, were found
to efficiently initiate the ring opening polymerization (ROP) of L-lactide in the presence
of benzyl alcohol at the room temperature yielding isotactic polymers (PLLAs) with relatively
narrow polydispersity indexes. The oxidation of styrene and cyclohexene, catalyzed by oxovanadium(IV) and (V) complexes was carried out using tert-butylhydroperoxide as the external
oxidant. Styrene oxide and cyclohexene oxide were obtained with high conversion and selectivity.