TRISILYLMETHANE AS A STRUCTURAL BACKBONE IN MULTIFUNCTIONAL LITHIUM AMIDES - SYNTHESES AND STRUCTURES OF HC((CH3)2SIN(LI)-T-BU)3 AND ITS SOLVATE HC((CH3)2SIN(LI)-T-BU)3.2THF

The trisilylmethane derivatives HC{(CH3)2SiH}3 (1) and C6H5C{(CH3)2SiH)3 (2) have been synthesized. Bromination and subsequent aminolysis with t-BuNH2 yielded HC{(CH3)2SiNH-t-Bu}3 (5) and C6H5C{(CH3)2SiNH-t-Bu}-{[(CH3)2Si]2N-t-Bu} (8), respectively. 5 was lithiated with 3 molar equiv of n-BuLi both in pentane and in THF yielding the trilithium triamide HC{(CH3)2SiN(Li)-t-Bu}3 (9) and its bis-THF solvate HC{(CH3)2SiN(Li)-t-Bu}3.2THF (11) which have been structurally characterized by single crystal X-ray structure analyses. 9: monoclinic, P2(1)/c, a = 17.379(6) angstrom, b = 8.483(3) angstrom, c = 18.801(3) angstrom, beta = 91.39-degrees, V = 1053.2 angstrom3, Z = 4, R = 0.053; 11: monoclinic, P2(1)/n, a = 11.783(4) angstrom, b = 19.026(6) angstrom, c = 16.761(5) angstrom, beta = 104.34(8)degrees, V = 1063.5 angstrom3, Z = 4, R = 0.058. 9 has an adamantane-type cage structure incorporating a puckered (LiN)3 ring while 11 contains two THF-solvated Li atoms bridging, respectively, two amido-N atoms while the third, nonsolvated Li has close bonding contacts to all three N-centers, thus generating a unique structural arrangement for a (LiN)3 unit. H-1- and Li-7-NMR spectroscopic studies of the generation of 9 indicate a certain degree of cooperativity in the metalation process with the preferential formation of the trimetalated species even after addition of subequivalent amounts of n-BuLi. Variable temperature H-1- and Li-7-NMR studies of 11 in solution indicate rapid chemical exchange within the system, which displays an effective 3-fold symmetry. This process could not be frozen out at 180 K.