AMINO-FUNCTIONALIZED TRISILYLMETHANES - PRECURSORS FOR A NEW CLASS OF TRIPODAL 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 structurally both in solution and in the solid state. The temperature dependence of the chemical shift of the apical proton in 1-5 and 8 along with H-1-NOESY experiments at variable temperature have established solution structures in which the peripheral groups point in, respectively, opposite directions relative to the ligand framework. The structural arrangement of the amines in the solid state was established by single-crystal 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, beta = 94.23(2)degrees, Z = 4, V = 3044.6(6) angstrom3, R = 0.043. 8: trigonal, 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 structure as postulated in solution, the amino-functionalized trisilylmethane unit in 8 may be viewed as part of an adamantane-related structure. The corresponding trilithium amides were obtained readily by reaction with n-butyllithium and, on the basis of their H-1- and C-13-NMR spectra, are thought to have an adamantoid cage structure. They react with 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 monofunctional building blocks in more complicated structural arrays.