Synthesis and investigation of the stability of Ti(III) β-diketiminato complexes. Structure of the tetrameric non-metallocene titanium fluoride complex (L2)4Ti4F6O2·2toluene supported by the β-diketiminato ligand (original) (raw)

The titanium b-diketiminato complexes (L1)TiCl 2 (1), (L1)TiCl(N2,6-i Pr 2 C 6 H 3 ) (2), and (L2) 2 TiCl (3) [L1 0/ (2,6-i Pr 2 C 6 H 3 )NC(Me)CHC(Me)N(2,6-i Pr 2 C 6 H 3 ), L20/ i PrNC(Me)CHC(Me)N i Pr] have been prepared by the reaction of the lithium salt of the ligand, L, with titanium trichloride. Complex 2 was isolated from supernatant solutions of 1 containing excess of the (L1)Li salt. The monochloride complex [(L2)TiCl(N i Pr)] 2 (4) was prepared by reduction of (L2) 2 TiCl 2 with the excess of Na/K alloy. Fluorination of the monochloride complex 3 with Me 3 SnF affords polymeric [(L2)TiF 2 ] n (5). Oxidation of 5 gives the tetrameric complex, (L2) 4 Ti 4 F 6 O 2 ×/2toluene (6). Compounds 1 Á/6 were characterized by single crystal X-ray structural analyses, elemental analyses, NMR and mass spectra. The bulky ligand (L1) stabilizes the Ti(III) complex 1 with an unusual distorted squareplanar pyramidal geometry around the titanium atom, by sigma bonding to the metal. The less bulky ligand (L2) in complexes 3, 4 and 6 has mixed s and p coordination to the titanium center. Investigation of the C Ã/C, N Ã/C distances in the NCCCN unit of the coordinated b-diketiminato ligands (L1) and (L2) demonstrated the localization of the double bonds in the ligand in complexes 1 Á/3 and 6. The stability of the complexes in solution was studied by means of NMR spectroscopy. Complexes 2 and 4 are stable in solution, the polymeric and the tetrameric nature of complexes 5 and 6 is not evident in C 6 D 6 solution. The (L2) 2 TiCl stoichiometry of the complex is unstable. #

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