NEW CHIRAL AMIDE LIGANDS DERIVED FROM (+ -)-TRANS-1,2-DIAMINOCYCLOHEXANE - APPLICATIONS IN TITANIUM(IV) CHEMISTRY/

Titanium(IV) hydrocarbyl compounds containing chiral bis(amide) ligand s derived from (+/-)-trans-1,2-(NHSiR(3))(2)-cyclohexanes (6a-c: SiR(3 ) = SiMe(3) (a), SiMe(2)Ph (b), SiMePh(2) (c) are described. The react ion of (+/-)-trans-1,2-diaminocyclohexane with SiR(3)Cl and NEt(3) aff ords diamines 6a-c in 60-80% yield. Double deprotonation of 6a-c with 2 equiv of n-BuLi yields the dilithio salts Li-2[(+/-)-trans-1,2-(NSiR (3))(2)-cyclohexane] (7a-c) in 70-97% yield. The reaction of 7a,b with TiCl4(THF)(2) in toluene yields mixtures of {(+/-)-trans-1,2-(NSiR(3) )(2)-cyclohexane}TiCl2 (8a,b) and bis(ligand) complexes {trans-1,2-(NS iR(3))(2)-cyclohexane}(2)Ti (9a,b; mixture of diastereomers). The reac tion of 7c with TiCl4 yields {(+/-)-trans-1,2-(NSiMePh(2))(2)-cyclohex ane}TiCl2 (8c; 15% isolated yield). The reaction of 6a,b and Ti(CH(2)P h)(4) yields -trans-1,2-(NSiR(3))(2)-cyclohexane}Ti(CH(2)Ph)(2) (10a,b ) cleanly, but these species are difficult to isolate due to their hig h solubility. Iodinolysis of 10a,b with I-2 yields {(+/-)-trans-1,2-(N SiR(3))(2)-cyclohexane}TiI2 (11a,b) in 60-80% isolated yield. 11a,b ca n be prepared in 60-80% isolated yield (vs Ti(CH(2)Ph)(4)) in a ''one- pot'' reaction by treatment of Ti(CH(2)Ph)(4) with 6a,b followed by io dinolysis. The dimethyl and diphenyl derivatives {(+/-)-trans-1,2-(NSi R(3))(2)-cyclohexane}TiMe(2) (12a,b) and {(+/-)-trans-1,2-(NSiR(3))(2) -cyclohexane}TiPh(2) (13a,b) are prepared by the reaction of 11a,b and RMgX reagents. X-ray crystallographic analyses establish that 10a and 11a have distorted tetrahedral structures with small N-Ti-N angles (c a. 92 degrees) and large X-Ti-X angles (ca. 116 degrees).