AMINO-FUNCTIONALIZED TRISILYLMETHANES - PRECURSORS FOR A NEW CLASS OFTRIPODAL AMIDO LIGANDS IN TRANSITION-METAL COMPLEXES

A series of amino-functionalized trisilylmethanes HC(SiMe2NHR)3 [R = 4 -CH3C6H4 (1), 3-CH3C6H4 (2), 2-CH3C6H4 (3), C6H5 (4), 4-FC6H4 (5), HC{ SiMe2NH[(S)-CH(CH3)Ph]}3 (8)] has been synthesized and studied structu rally both in solution and in the solid state. The temperature depende nce of the chemical shift of the apical proton in 1-5 and 8 along with H-1-NOESY experiments at variable temperature have established soluti on structures in which the peripheral groups point in, respectively, o pposite directions relative to the ligand framework. The structural ar rangement of the amines in the solid state was established by single-c rystal X-ray structure analyses of 1 and 8. 1: monoclinic, P2(1)/n, a = 9.160(2) angstrom, b = 9.456(3) angstrom, c = 35.25(1) angstrom, bet a = 94.23(2)degrees, Z = 4, V = 3044.6(6) angstrom3, R = 0.043. 8: tri gonal, P3, a = 16.510(2) angstrom, c = 10. 592(2) angstrom, Z = 3, V = 2500.4(5) angstrom3, R = 0.047. Whereas 1 has an almost inverted stru cture as postulated in solution, the amino-functionalized trisilylmeth ane unit in 8 may be viewed as part of an adamantane-related structure . The corresponding trilithium amides were obtained readily by reactio n with n-butyllithium and, on the basis of their H-1- and C-13-NMR spe ctra, are thought to have an adamantoid cage structure. They react wit h TiX4(THF)2 to yield the tripodal amidotitanium complexes HC(SiMe2-NR )3TiX {R = 4-CH3C6H4, X = Cl [Br] (14a [b]), R = 3-CH3C6H4, X = Cl [Br ] (15a [b]), R = 4-FC6H4, X Br (16)] which are of interest as monofunc tional building blocks in more complicated structural arrays.