Ligand oxidation of small-ring aza- and thia-macrocycles involving C-H activation: crystal structures of [MeN(CH2NMe)(2)CH](2)[MX6]center dot MeCN (M = Te, X = Cl, Br; M = Sn, X = Br and [C6H11S3](2)[TeBr6]center dot MeCN)

摘要

Reactions of M(IV) halides with the six-membered triazacyclohexane (MeNCH2)(3), provide the ionic salts [MeN(CH2NMe)(2)CH](2)[MX6]. MeCN where M = Te, X = Cl (I); M = Te, X = Br (II) and M = Sn, X = Br (III), as confirmed by spectroscopic and single crystal X-ray diffraction studies. The individual [MeN(CH2NMe)(2)CH](+) cations contain a planar (Me)N-CH-N(Me) segment reminiscent of amidinium formation (mean): N-C, 1.31(1) ; N-C-N, 121.3(1)degrees. A plausible reaction pathway involving an incipient release of a hydride ion from a CH, unit of the bound ligand and a subsequent attack (nucleophilic) at the beta -carbon of a coordinated acetonitrile (solvent) molecule is discussed. Supporting evidence for activation of the acetonitrile via a nucleophilic attack comes from the reaction system GeBr4/(C3H7NHCOCH2CONHC3H7)-C-i-C-i/CH3CN, which provides the cationic organohydrobromide salt [CH3C(CH((CONHC3H7)-C-i)(2))(2)NH3],Br (IV). The structure of IV reveals two malonamide fragments attached to the acetonitrile residue. The reaction of TeBr4 and [9]aneS(3) provides orange crystals of a product identified spectroscopically and by X-ray diffraction studies as the bicyclic sulphonium salt [C6H11S3],[TeBr6]. MeCN (V). A plausible reaction pathway, namely molecular oxidation with C-H activation resulting in hydride ion expulsion, is suggested. The structure of the bicyclic cation reveals a five-membered ring and a six-membered ring fused along a common S-C linkage, 1.825(6) Angstrom. The peripheral S-C bond distances lie in the range 1.800(5)- 1.822(5) Angstrom. The reaction of TeCl4 and Me-3[9]aneN(3) in toluene gives orange crystals of the doubly-protonated ligand salt [(Me-3[9]aneN(3))H-2][TeCl6].C6H5CH3 (VI). An extensive pattern of intra- and inter-molecular hydrogen bonding is observed. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 90]