COORDINATION STUDIES OF THE LIGAND SERIES -CO-CENTER-DOT(CH2)(N)CENTER-DOT-CO-CENTER-DOT-NHR WHERE R = ALKYL, ARYL O = O, S AND N = 0,1,2 -PART 6 - CRYSTAL-STRUCTURES AND BONDING CONSIDERATIONS OF THE LIGANDSOT-CO-CENTER-DOT-CH2-CENTER-DOT-CO-CENTER-DOT-NHME (L-1), T-CH2-CENTER-DOT-CH2-CENTER-DOT-CO-CENTER-DOT-NHME (L-4), OT-CS-CENTER-DOT-CH2-CENTER-DOT-CS-CENTER-DOT-NHME

Crystal structures of the ligands MeNH . CO . CH2. CO . NHMe, MeNH . C O . CH2. CH2. CO . NHMe and MeNH . CS . CH2. CS . NHMe have been deter mined by X-ray diffraction studies. The framework C-C, C-N, and C=O/C= S bond distances and the associated interbond angles are all closely s imilar and the packing of these molecules is dominated by intermolecul ar hydrogen bonding of the type N-H ... O=C and, to a lesser extent, N -H ... S=C. For means of comparison the bond parameters of all the str ucturally characterised related ligands belonging to the N,N'-disubsti tuted series RNH . CO (CH2)(n). CO . NHR where R = alkyl; O = O, S and n = O, 1, 2 are listed and a general overview of the characteristics of such ligands including conformational variations is provided. Struc tural characterisation (X-ray diffraction) of SnBr4 (MeNH . CO . CH2. CO . NHMe). MeNH . CO . CH2. CO . NHMe, SnBr4((PrNH)-Pr-i . CO . CH2. CO . (NHPr)-Pr-i). 2THF and SnBr4(iPrNH . CS . CH2CS . (NHPr)-Pr-i). M eCN reveals bidentate chelate ligand attachment for these six coordina te mononuclear cis-octahedral Sn(IV) complexes. In all three structure s, the NH groups are involved in intermolecular hydrogen bonding being linked either to C=O/C=S groups of adjacent molecules, or solvent mol ecule(s) entrapped in the lattice and/or halogen atom(s) of a neighbou ring SnBr4 moiety. The general range of Sn-Br distances is 2.504(3)-2. 565(12) Angstrom excluding those halogen atoms directly involved in N- H ... Br-Sn interactions. These several types of intermolecular hydrog en bonding are viewed as a direct cause of ring puckering in the chela ted rings approximating to a chair conformation. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.