Rare-earth metal-mediated PhC[triple bond, length as m-dash]N insertion into N,N-bis(trimethylsilyl)naphthalene-1,8-diamido dianion - a synthetic approach to complexes coordinated by ansa-bridged amido-amidinato ligand.

Lithium silylamides 1,8-CH[N(SiMe)Li(L)] (L = EtO (); L = TMEDA (1TMEDA)), when treated with PhC[triple bond, length as m-dash]N, formed the adducts 1,8-CH[N(SiMe)Li(N[triple bond, length as m-dash]CPh)(OEt)][N(SiMe)Li(OEt)] () and 1,8-CH[N(SiMe)Li(N[triple bond, length as m-dash]CPh)][N(SiMe)Li(TMEDA)] (2TMEDA) containing one benzonitrile molecule coordinated to Li ion while the second molecule retains a coordinated L ligand. The salt metathesis reactions of LnCl (Ln = Y, Sm) with equimolar amounts of and 2TMEDA (THF, 4 h, 40 °C) resulted in benzonitrile insertion and formation of new dianionic amido-amidinate ligands. The reactions of with LnCl afforded ionic chloro complexes [{1,8-CH[NSiMe][NC(Ph)NSiMe]}{1,8-CH[N(H)SiMe][NC(Ph)NSiMe]}LnCl][Li(L)] (Ln = Y, L = THF, n = 4 (3Y), Ln = Sm, L = DME, n = 3 (3Sm)), while the reaction of 2TMEDA and YCl leds to the formation of the neutral salt-free yttrium chloro complex {1,8-CH[NSiMe][NC(Ph)NSiMe]}YCl(TMEDA) (4). The treatment of 3Y and 4 with tBuOK enabled the synthesis of tert-butoxides [{1,8-CH[NSiMe][NC(Ph)NSiMe]}{1,8-CH[N(H)SiMe][NC(Ph)NSiMe]}YOtBu][Li(THF)] (7) and {1,8-CH[NSiMe][NC(Ph)NSiMe]}YOtBu(TMEDA) (8). Complexes 7 and 8 were evaluated as initiators for the ring opening polymerization of rac-lactide. Neutral tert-butoxide complex 8 demonstrated significantly higher activity compared to that of ionic 7.