Da. Robson et al., Neutral and cationic organometallic aluminium and indium complexes of mono-pendant arm triazacyclononane ligands, J CHEM S DA, (2), 2001, pp. 157-169
Citations number
62
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
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)].