Heterocyclic nitrogen donor complexes of aluminium, gallium and indium with weakly coordinating triflate anions

Abstract The reactions of M(OTf)3 (M = Al, Ga, In; OTf = CF3SO3–) with 2,2′:6′,2′’- terpyridyl (terpy) in CH2Cl2 gave mer-[M(OTf)3(terpy)], whilst with 2,2′-bipyridyl (bipy) and 1,10-phenanthroline (phen) the products isolated were cis-[M”(OTf)2(bipy)2]OTf (M” = Al, Ga), cis-[In(OTf)(H2O)(bipy)2][OTf]2, cis-[Al(OTf)2(phen)2][OTf] and [In(H2O)2(phen)2][OTf]3. The X-ray structures of mer-[In(OTf)3(terpy)], cis-[Ga(OTf)2(bipy)2][OTf] and cis-[In(OTf)(H2O)(bipy)2][OTf]2, along with those of the minor by-products, cis-[Ga(H2O)2(phen)2][OTf]3 and the hydroxide-bridged dimer [{In(terpy)(OTf)}2(µ-OH)2][OTf]2 were also obtained, all of which show six-coordination at the metal ion. While the anhydrous complexes show κ1-coordination of the triflate to the metal ion, those species with coordinated water (or hydroxide) ligands show significant H-bonding interactions between the water H atoms and the O-atoms from triflate anions. The complexes were characterised by IR, 1H, 13C{1H}, 19F{1H} and 27Al NMR spectroscopy, together with microanalysis. The 19F{1H} NMR spectra suggest that in MeCN solution the coordinated triflates are displaced by the solvent, but the original complexes appear to reform on removal of the MeCN in vacuo.