New iso-propoxides, tert-butoxides and neo-pentoxides of niobium(v): Synthesis, structure, characterization and stabilization by trifluoroheteroarylalkenolates and pyridine ligands

作者：Appel Linus; Fiz Raquel; Tyrra Wieland; Mathur Sanjay^*

来源：Dalton Transactions, 2012, 41(7): 1981-1990.

DOI：10.1039/c1dt11668a

The synthesis and characterization of nine new heteroleptic alkoxides of niobium is described. Metathesis reactions of Nb2Cl10 with (BuCH2OH)-Bu-t and pyridine (py) or 4-dimethylaminopyridine (DMAP) affords monomeric octahedral complexes Nb((OCH2Bu)-Bu-t)(5)py (1) and Nb((OCH2Bu)-Bu-t)(5)DMAP (2), respectively, in high yields (%26gt;60%). The same reaction with (BuOH)-Bu-t resulted in a chloro functionalized alkoxide Nb((OBu)-Bu-t)(4)pyCl (3) and could not be pushed to complete removal of remaining Cl- ligand. The introduction of a chelating bidental ligand 3,3,3-trifluoro-1-(pyridine-2-yl) propen-2-ol (2-PyCHCOHCF3) (4 %26apos;%26apos;) in the dimeric framework of Nb-2((OPr)-Pr-i)(10) (4 %26apos;) produced a heteroleptic, monomeric niobium complex Nb((OPr)-Pr-i)(4)(2-PyCHCOCF3 ) (4) with significantly enhanced stability and volatility. As a comparison to (4), five different heteroaryl systems (5-9) with the same side chain have been synthesized and examined in order to understand the influence upon physio-chemical properties. All the new compounds (1-9) have been characterized by microanalysis, variable temperature multinuclear NMR spectroscopy, mass spectrometry, thermal analysis and single crystal X-ray diffraction studies ((3), (4) and (9)). The molecular structure of (3) revealed mononuclear species with Nb atoms present in the distorted octahedral environment of four (BuO)-Bu-t, one chloride and one pyridine ligand. Compounds (4) and (9) consisting of four (PrO)-Pr-i and a trifluoroheteroarylenolate exhibited a stronger distortion in the molecular geometry due to the rigidity of chelating beta-alkenolate moiety.

• 出版日期2012