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

Reactions of M(IV) halides with the six-membered triazacyclohexane (MeNCH2)3 provide the ionic salts [MeN(CH2NMe)2CH]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)2CH]+ cations contain a planar (Me)NCHN(Me) segment reminiscent of amidinium formation (mean): NC, 1.31(1) Å; NCN, 123.3(1)°. A plausible reaction pathway involving an incipient release of a hydride ion from a CH2 unit of the bound ligand and a subsequent attack (nucleophilic) at the β-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/iC3H7NHCOCH2CONHiC3H7/CH3CN, which provides the cationic organohydrobromide salt [CH3C(CH(CONHiC3H7)2)2NH3]Br (IV). The structure of IV reveals two malonamide fragments attached to the acetonitrile residue. The reaction of TeBr4 and [9]aneS3 provides orange crystals of a product identified spectroscopically and by X-ray diffraction studies as the bicyclic sulphonium salt [C6H11S3]2[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) Å. The peripheral SC bond distances lie in the range 1.800(5)–1.822(5) Å. The reaction of TeCl4 and Me3[9]aneN3 in toluene gives orange crystals of the doubly-protonated ligand salt [(Me3[9]aneN3)H2][TeCl6]·C6H5CH3 (VI). An extensive pattern of intra- and inter-molecular hydrogen bonding is observed.