Neutral and cationic organometallic aluminium and indium complexes of mono-pendant arm triazacyclononane ligands

Organometallic monomeric and dimeric, neutral and cationic, kappa (2)- and kappa (4)-coordinated mono-pendant arm triazacyclononane complexes of alumi nium and indium have been prepared, along with three new mono-pendant arm t riazacyclononane ligand precursors HL4, HL5 and HL6 (HL4 = 1-(2-hydroxy-2-m ethylethyl)-4,7-diisopropyl-1,4,7-triazacyclononane; HL5 = 1-(2-hydroxy-2-m ethylethyl)-4,7-dimethyl-1,4,7-triazacyclononane; HL6 = 1-(2-hydroxy-2,2-di phenylethyl)-4,7-diisopropyl-1,4,7-triazacyclononane). Reaction of HL4 or H L5 with AlMe3 or AlMe3. py gives the mu -alkoxide bridged dimeric complexes [Al-2(kappa (2)-L-4)(2)Me-4] and [Al-2(kappa (2)-L-5)(2)Me-4]. Reaction of HL4 with two equivalents of AlMe3 gives the monomeric compound [Al(kappa ( 2)-L-4. AlMe3)Me-2] which can also be prepared by treating [Al-2(kappa (2)- L-4)(2)Me-4] with two equivalents of AlMe3. Reaction of HL2 with AlMe3. py gives [Al(kappa (2)-L-2)Me-2], whereas AlMe3 reacts with one or two equival ents of HL1 to give exclusively [Al(kappa (2)-L-1)(2)Me] which contains two kappa (2)-L-1 ligands (HL1 = 1-(2-hydroxy-3,5-dimethylbenzyl)-4,7-diisopro pyl-1,4,7-triazacyclononane; L-2 = 1-(3,5-di-tert-butyl-2-hydroxybenzyl)-4, 7-diisopropyl-1,4,7-triazacyclononane). Reaction of AlMe3 with HL6 gives lo w yields of the monomeric derivative [Al(kappa (2)-L-6)Me-2]. The kappa (2) -coordination mode of the triazacyclononane ligands in all these compounds is unique in the chemisty of these ligands. The crystal structures of four of them are discussed. Methyl group abstraction from [Al(kappa (2)-L-4. AlM e3)Me-2] or [Al(kappa (2)-L-2)Me-2] using B(C6F5)(3) gives the kappa (4)-co ordinated cationic derivatives [Al(kappa (4)-L-2)Me][MeB(C6F5)(3)] and [Al( kappa (4)-L-4. AlMe3)Me][MeB(C6F5)(3)], and the latter undergoes reaction w ith pyridine or MeCN to form [Al(kappa (4)-L-4)Me][MeB(C6F5)(3)]. The catio nic centres in the last three compounds are unreactive to unsaturated subst rates and aprotic Lewis bases. Reaction of In(CH2Ph)(3) with HL1 or HL2 aff ords the four-coordinate complexes [In(kappa (2)-L-1)(CH2Ph)(2)] and [In(ka ppa (2)-L-2)(CH2Ph)(2)] in which the L-1,L-2 ligand is kappa (2) bound to I n. With the sterically less demanding HL3 [1-(3,5-di-tert-butyl-2-hydroxybe nzyl)-4,7-dimethyl-1,4,7-triazacyclononane], however, the six-coordinate co mplex [In(kappa (4)-L-3)(CH2Ph)(2)] is formed. The compound [In(kappa (2)-L -2)(CH2Ph)(2)] reacts with B(C6F5)(3) to form [In(kappa (4)-L-2)(CH2Ph)][(P hCH2)B(C6F5)(3)].