Reaction of GaCl3 with 1 mol equiv of [14]aneS(4) in anhydrous CH2Cl2 gives the exocyclic chain polymer [GaCl3([14]-aneS(4))] (1) whose structure confirms trigonal bipyramidal coordination at Ga with a planar GaCl3 unit. In contrast, using [16]aneS(4) and GaCl3 or [16]aneSe(4) and MCl3 (M = Ga or In) in either a 1:1 or a 1:2 molar ratio produces the anion-cation S complexes [GaCl2([16]aneS(4))][GaCl4] (2) and [MCl2([16]-aneSe(4))][MCl4] (M = Ga, 3 and M = In, 4) containing transoctahedral cations with endocyclic macrocycle coordination. The ligand-bridged dimer [(GaCl3)(2){o-C6H4(SMe)(2)}] (5) is formed from a 2:1 mol ratio of the constituents and contains distorted tetrahedral Ga(III). This complex is unusually reactive toward CH2Cl2, which is activated toward nucleophilic attack by polarization with GaCl3, producing the bis-sulfonium species [o-C6H4(SMeCH2Cl)(2)][GaCl4](2) (6), confirmed from a crystal structure. In contrast, the xylyl-based dithioether gives the stable [(GaCl3)(2){o-C6H4(CH2SEt)(2)}] (8). However, replacing GaCl3 with InCl3 with o-C6H4(CH2SEt)(2) preferentially forms the 4:3 In:L complex [(InCl3)(4){o-C6H4(CH2SEt)(2)}(3)] (9) containing discrete tetranuclear moieties in which the central In atom is octahedrally coordinated to six bridging Cl's, while the three In atoms on the edges have two bridging Cl's, two terminal Cl's, and two mutually trans S-donor atoms from different dithioether ligands. GaCl3 also reacts with the cyclic bidentate [8]aneSe(2) to form a colorless, extremely air-sensitive adduct formulated as [(GaCl3)(2)([8]aneSe(2))] (10), while InCl3 gives [InCl3([8]aneSe(2))] (14). Very surprisingly, 10 reacts rapidly with O-2 gas to give initially the red [{[8]aneSe(2)}(2)][GaCl4](2) (11) and subsequently the yellow [{[8]aneSe(2)}Cl][GaCl4] (12). The crystal structure of the former confirms a dimeric [{[8]aneSe(2)}(2)](2+) dication, derived from coupling of two mono-oxidized {[8]aneE(2)}(+center dot) cation radicals to form an Se Se bond linking the rings and weaker transannular 1,5-Se center dot center dot center dot Se interactions across both rings. The latter (yellow) product corresponds to discrete doubly oxidized {[8]aneSe(2)}(2+) cations (with a primary Se-Se bond across the 1,5-positions of the ring) with a Cl-bonded to one Se. Tetrahedral [GaCl4](-) anions provide charge balance in each case. These oxidation reactions are clearly promoted by the Ga(III) since [8]aneSe(2) itself does not oxidize in air. The new complexes have been characterized in the solid state by IR and Raman spectroscopy, microanalysis, and X-ray crystallography where possible. Where solubility permits, the solution characteristics have been probed by H-1, Se-77{H-1}, and Ga-71 NMR spectroscopic studies.