Cyclopentadienyl-Amido Ligands with a Pendant “−NHR” Amino Functionality in Titanium Chemistry. Molecular Structure of [Ti{η⁵-C₅H₄SiMe₂-η-N(CH₂)₂-η-NHCHMe₂}Cl₂]

Abstract

The reaction of the chlorodimethylsilyl-substituted cyclopentadienyl titanium compound [Ti(η 5 -C 5 H 4 SiMe 2 Cl)Cl 3 ] (1) with 1 equiv of NH 2 (CH 2 ) 2 NHR (R ) H, CHMe 2 ), in the presence of 2 equiv of NEt 3 , afforded the mononuclear complexes [Ti{η 5 -C 5 H 4 SiMe 2 -η-N(CH 2 ) 2 -η-NHR}-Cl 2 ] (R ) H, 2; CHMe 2 , 3) in high yield. While 2 is stable in solution, 3 slowly evolves into the strain-free complex [Ti{η 5 -C 5 H 4 SiMe 2 NH(CH 2 ) 2 -η-NCHMe 2 }Cl 2 ] (4). 1 reacts with 0.5 equiv of ethylenediamine to yield a mixture of 2 and the dinuclear titanium complex [Ti-{η 5 -C 5 H 4 SiMe 2 -η-N(CH 2 )-}Cl 2 ] 2 (5), which contains two tethered cyclopentadienyl-silyl-amido fragments. Compound 5 is also obtained from the reaction of 2 with 1. Treatment of 1 with 0.5 equiv of propylenediamine rendered the dinuclear compound [Ti{η 5 -C 5 H 4 SiMe 2 -η-N(CH 2 ) 1.5 -}Cl 2 ] 2 (6), whereas a mixture of 6 and the mononuclear species [Ti{η 5 -C 5 H 4 SiMe 2η-N(CH 2 ) 3 NH 2 }Cl 2 ] (7) was spectroscopically observed when 1 was reacted with 1 equiv of NH 2 (CH 2 ) 3 NH 2 in C 6 D 6 . A similar reaction of 1 with N-methylpropylenediamine regioselectively affords the unstrained mononuclear compound [Ti{η 5 -C 5 H 4 SiMe 2 NH(CH 2 ) 3 -η-NMe}-Cl 2 ] (8). Dinuclear derivatives [Ti{η 5 -C 5 H 4 SiMe 2 -η-N(CH 2 ) x -}Cl 2 ] 2 (x ) 2 (9); 2.5 (10)) were prepared by reacting complex 1 with butylenediamine and pentylenediamine, respectively. These compounds were characterized by elemental analysis and NMR spectroscopy. The crystal structure of 3 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

“…In an additional attempt to isolate a new silyl-g-amido constrained geometry complex, we added an equimolecular amount of LiNHtBu to a C 6 (8) as the unique reaction product. Compound 8 could not be isolated, and was only detected by its spectroscopic data, which were clearly different from those observed for 7.…”

“…The solution was filtered and the solvent was removed to yield an oily mixture of diastereoisomers 4a and 4b in a 1:0.5 molar ratio (0.43 g, 80% yield). NMR data for 4a/4b (C 6 A solution of 5 equiv. of LiNHtBu (0.43 g, 5.55 mmol) in diethylether (25 mL) was added dropwise to a solution of 2 (0.50 g, 1.11 mmol) in diethylether (25 mL) at room temperature.…”

“…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].…”