Synthesis and structures of novel chiral lithium amidinates and mono- and di-lithium (1R,2R)-(-)-1,2(NHSiMe3)2C6H10

Four lithium salts derived from (1R,2R)-1,2-diaminocyclohexane are described. After the resolution of 1,2-diaminocyclohexane (DACH), (1R,2R)-(-)-1,2-(NHSiMe3)(2)C6H10 (1) was prepared from the (R,R) enatiomer by reaction with LiBun and Me3SiCl. Treatment of 1 with one equiv. of LiBun gave the single lithium salt (1R,2R)-(-)-1-Li(NSiMe3)-2-(NHSiMe3)C6H10 (2). Double deprotonation of 1 with two equiv. of LiBun yielded the dilithium salt Li-2[(1R,2R)-(-)-1,2-(NSiMe3)(2)C6H10] (3). The addition reaction of 2 or 3 with PhCN gave (1R,2R)-(-)-1-Li[NC(Ph)N(SiMe3)]-2-(NHSiMe3)C6H10 (4) and Li-2[(1R,2R)-(-)-1,2-{NC(Ph)N(SiMe3)}(2)C6H10] (5) respectively. Crystallographic studies and comparison of these lithium salts with beta-diketiminates exhibit some noteworthy features.