A Versatile Synthetic Route for Cyclopentadienyl−Amido Titanium(IV) Compounds. NMR Spectroscopy Study and X-ray Molecular Structure of [Ti{η⁵-C₅H₄SiMe₂NMe(CH₂)₂-η-NMe}Cl₂]

Abstract

The reaction of the chlorosilyl-substituted cyclopentadienyltitanium compound [Ti(η 5 -C 5 H 4 -SiMe 2 Cl)Cl 3 ] with N,N′-dimethylethylenediamine in the presence of 2 equiv of NEt 3 gave a mixture of two complexes, [Ti{η 5 -C 5 H 4 SiMe 2 NMe(CH 2 ) 2 -η-NMe}Cl 2 ] (1) and [Ti{η 5 -C 5 H 4 SiMe 2η-N(CH 2 ) 2 -η-NHMe}Cl 2 ] (2), in a molar ratio of 3:1. However, a similar reaction with N-methylethylenediamine afforded complex 2 regiospecifically. The dialkyl derivatives [Ti- 3), CH 2 Ph (4)) were prepared by reacting the dichloride complex 1 with 2 equiv of MgClMe or 1 equiv of Mg(CH 2 Ph) 2 •2THF, respectively. The analogous reaction with LiNMe 2 afforded the diamido derivative [Ti{η 5 -C 5 H 4 SiMe 2 NMe(CH 2 ) 2 -η-NMe}(NMe 2 ) 2 ] (5) in high yield. Complex 1 reacts with dry CO 2 via insertion of a molecule of CO 2 into each of the Ti-N and Si-N bonds to yield the dicarbamate compound [Ti{(η 5 -C 5 H 4 SiMe 2 OC(O)NMe(CH 2 ) 2 NMe(η 2 -CO 2 )}Cl 2 ] (6), in which the carbamate groups are bound in η 2 -and η 1 -fashion. Thermal decomposition of complex 6 afforded the known oxo derivatives [Ti{µ-(η 5 -C 5 H 4 SiMe 2 -η-O)}Cl 2 ] 2 and [(TiCl 2 ) 2 (µ-O)-[µ-{(η 5 -C 5 H 4 SiMe 2 ) 2 -(µ-O)}] with elimination of CO 2 and 1,3-dimethyl-2-imidazolidinone. The conformational interconversion of 1 and 6 and the reversible coordination of the terminal "NHMe" group to the metal center in 2 were studied in solution by DNMR spectroscopy. The crystal structure of 1 was determined by X-ray diffraction methods.

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl] (Ar=2,6-Me2C6H3)

“…When this functionality on the ring is the [SiMe 2 Cl] group, the reactivity of the Si-Cl bond facilitates access to a versatile range of products, including catalysts anchored on solid supports [2][3][4][5] and silylamido bridge formation between the cyclopentadienyl ligand and the metal centre (constrained-geometry complexes) [6][7][8][9][10][11].…”

Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

“…Complex 4 is the kinetic product of the reaction, since heating a C 6 D 6 solution of 4 or leaving the oily mixture of diastereoisomers of 4 at room temperature for several days gave the bisamidosilyl complex [Nb{g 5 [7], which proved to be an intermolecular process. In this case, the 1 H NMR spectrum of 5 again showed an AA 0 BB 0 pattern, after recovering the C s symmetry; meanwhile, the 29 Si NMR spectrum showed a resonance shifted highfield (d À29.0), due to the presence of two p donor amido ligands bound to the silicon atom [29,30].…”

“…A particularly useful functionality is that containing a chlorosilyl group because the reactivity of the Si-Cl bond facilitates the formation of the silyl-g-amido bridge between the cyclopentadienyl ligand and the metal centre [2][3][4][5][6][7][8]. These types of silyl-g-amido monocyclopentadienyl groups 3 and 4 metal complexes are active catalysts for olefin polymerization (constrainedgeometry catalysts) [9][10][11][12] and a rich chemistry has been developed [13][14][15][16][17] since their discovery, showing both similarities and differences when compared with related dicyclopentadienyl compounds.…”

“…We focused our research interest on studies related to cyclopentadienyl group 4-6 metal complexes supporting modified cyclopentadienyl rings [2][3][4][5][6][7][8][18][19][20][21][22][23][24], and reported the synthesis of silyl-g-amido cyclopentadienyl group 4 and 5 metal complexes using the related (chlorodimethylsilyl)cyclopentadienyl metal derivatives [2][3][4][5][6][7][8]24]. Hydrolysis of these compounds also led to the isolation of dinuclear derivatives with Si-O-Si bridges for Nb [8,21,25], Mo and W [24] and Si-O-M bridges for Nb [25] and group 4 metals [2,26,27].…”

“…Continuing our studies on the chemistry of metal compounds with modified monocyclopentadienyl ligands, we report here the synthesis of the (dichloromethylsilyl)cyclopentadienyl niobium derivative [Nb{g 5 -C 5 H 4 -(SiCl 2 Me)}Cl 4 ] and its reactions with lithium amides to give imidodichloro-and imidochloroamido-niobium complexes with aminosilylcyclopentadienyl ligands [Nb{g 5 …”