TaCp*Cl 2 {N(2,6-Me 2 C 6 H 3 )}] reacts with 2 equiv of LiMe at -78 °C to give the imido dimethyl complex TaCp*Me 2 {N(2,6-Me 2 C 6 H 3 )} (1) in almost quantitative yield, whereas the monomethyl imido derivatives [TaCp*MeX{N(2,6-Me 2 C 6 H 3 )}] (X ) Cl (2), OC 6 H 3 Me 2 (3)) can be prepared by addition of HX (X ) Cl, OC 6 H 3 Me 2 ) to toluene solutions of [TaCp*Me-(NR){NR(CMedCMe 2 )}] (R ) 2,6-Me 2 C 6 H 3 ) with elimination of the corresponding imine RNdCMeCHMe 2 . Complex 1 reacts with CO to give the dinuclear ene diolate complex [TaCp*{N(2,6-Me 2 C 6 H 3 )Me}] 2 {µ-η 2 -OC(Me)dC(Me)O} (5) via intermolecular coupling between two acyl carbon atoms of the intermediate η 2 -acyl complex TaCp*Me{N(2,6-Me 2 C 6 H 3 )}{η 2 -C(Me)dO} ( 4). However, when the same reaction was carried out with the chloro imido methyl derivative 2, the unexpected oxo 7) was obtained via the barely stable intermediate η 2 -acyl complex [TaCp*Cl-{N(2,6-Me 2 C 6 H 3 )}{η 2 -C(Me)dO}] (6). The analogous reaction of [TaCp*Cl 2 Me 2 ] with CO leads to the formation of the dichloro oxotantalacyclopropane complex [TaCp*Cl 2 (η 2 -CMe 2 O)] ( 8), but the acyl intermediate species was not observed. Similarly, the azatantalacyclopropane complexes [TaCp*XMe(η 2 CMe 2 -NR)] react with 1 equiv of CO to form the stable enolate derivatives [TaCp*X(NR){OC(Me)dCMe 2 }] (X ) Cl (9), Me (10); R ) 2,6-Me 2 C 6 H 3 ). The stable 18-electron imido η 2 -iminoacyl derivatives [TaCp*X(NR){η 2 -C(Me)dNR}] (X ) Me (11), Cl (12), OC(Me)dCMe 2 (13); R ) 2,6-Me 2 C 6 H 3 ) are formed when the isocyanide RNC (1 equiv) is added to toluene solutions of the imido complexes 1, 2, and 10, respectively. All compounds were characterized by IR and NMR ( 1 H and 13 C), and the molecular structures of 7 and 11 were studied by X-ray diffraction methods.
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.
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.
Crystal size 0.35 x 0.20 x 0.19 mm Theta range for data collection 3.33 to 27.51 deg. Limiting indices -18<=h<=18, -12<=k<=12, -14<=l<=14 Reflections collected / unique 34587 / 3713 [R(int) = 0.0509] Completeness to theta = 27.51 99.6 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.785 and 0.597 Refinement method Full-matrix least-squares on F^2
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