Five-coordinate organoaluminum acetylides and crystal structure of the hydrosylate, [Salophen(tBu)Al]2O

Mononuclear salen-gallium complexes for iso-selective ring-opening polymerization (ROP) of rac-lactide

Mononuclear salen-supported Ga amido and alkoxide complexes, structurally characterized herein, mediate the controlled and iso-selective polymerization ofrac-lactide.

Reactions of α-diimine-aluminum complexes with sodium alkynides: versatile structures of aluminum σ-alkynide complexes

Reaction of AlCl(3) with the monoanionic α-diimine ligand [NaL] yielded the complex [L˙(-)Al(III)Cl(2)(-)] (1, L = [(2,6-iPr(2)C(6)H(3))NC(Me)](2)), and subsequent reduction of by sodium metal afforded the mononuclear [L(2-)Al(III)Cl(-)(THF)] (2) and binuclear [L(2-)(THF)Al(II)-Al(II)(THF)L(2-)] (3). Compounds 2 and 3 exhibit interesting reactivities to sodium alkynides at room temperature. Treatment of dialumane 3 with 1 equiv. of 4-methylphenylacetylene in the presence of sodium metal yielded the asymmetric Al-Al-bonded compound [Na(Et(2)O)][LAl-Al(C[triple bond, length as m-dash]C(C(6)H(4)-Me))L] (4) containing an alkynyl group attached to one of the Al atoms. The reaction of 2 with 4-methylphenylacetylene and Na (or sodium 4-methylphenylacetylide) resulted in the mononuclear product [L(THF)Al(C[triple bond, length as m-dash]C-(C(6)H(4)-Me))] (5) containing a single terminal acetylide ligand. Precursor 2 reacted with 2 equiv. of phenylacetylene (or 4-methylphenylacetylene, trimethylsilylacetylene) and Na to give the tweezer "ate" complexes, [Na(THF)(DME)][LAl(C[triple bond, length as m-dash]CR)(2)] (R = C(6)H(5), ; C(6)H(4)-Me, ; Si(Me)(3), 6c), [Na(THF)](2)[LAl(C[triple bond, length as m-dash]CPh)(2)](2)(μ-C(7)H(8)) (7), [Na(C(7)H(8))][(μ-Na)][LAl(C[triple bond, length as m-dash]CSi(Me)(3))(2)](2) (8), as well as the polymeric [LAl(C[triple bond, length as m-dash]CPh)(2)Na](n) (9). In the products, two alkynyl groups coordinate terminally to one Al center and a sodium ion is embedded between these two alkynyls. Interestingly, both cycloaddition and terminal acetylide coordination of three equiv. of alkyne occurred in the reaction of with 1-hexyne, resulting in the unique dialuminum complex [Na(Et(2)O)](2)[{L(C(C(4)H(9))[double bond, length as m-dash]CH)}Al(C[triple bond, length as m-dash]C(C(4)H(9)))(2)](2) (10). Complexes 1-10 have been characterized by NMR ((1)H, (13)C) and IR spectroscopy, elemental analysis, and X-ray diffraction, and their electronic structures were studied by DFT calculations.

Salen-complex-mediated formation of cyclic carbonates by cycloaddition of CO2 to epoxides

Metal complexes of salen ligands are an important class of compounds, and they have been widely studied in the past. Among their successful catalytic applications, the synthesis of cyclic carbonates by the coupling reaction of epoxides with CO(2) has received increased attention; this is mostly due to the importance of using a greenhouse gas as a feedstock for the synthesis of useful molecules. Herein the most relevant past and present research surrounding this topic is presented.

Cyclic carbonate synthesis catalysed by bimetallic aluminium-salen complexes

The development of bimetallic aluminium-salen complexes [{Al(salen)}(2)O] as catalysts for the synthesis of cyclic carbonates (including the commercially important ethylene and propylene carbonates) from a wide range of terminal epoxides in the presence of tetrabutylammonium bromide as a cocatalyst is reported. The bimetallic structure of one complex was confirmed by X-ray crystallography. The bimetallic complexes displayed exceptionally high catalytic activity and in the presence of tetrabutylammonium bromide could catalyse cyclic carbonate synthesis at atmospheric pressure and room temperature. Catalyst-reuse experiments demonstrated that one bimetallic complex was stable for over 60 reactions, though the tetrabutylammonium bromide decomposed in situ by a retro-Menschutkin reaction to form tributylamine and had to be regularly replaced. The mild reaction conditions allowed a full analysis of the reaction kinetics to be carried out and this showed that the reaction was first order in aluminium complex concentration, first order in epoxide concentration, first order in carbon dioxide concentration (except when used in excess) and unexpectedly second order in tetrabutylammonium bromide concentration. Further kinetic experiments demonstrated that the tributylamine formed in situ was involved in the catalysis and that addition of butyl bromide to reconvert the tributylamine into tetrabutylammonium bromide resulted in inhibition of the reaction. The reaction kinetics also indicated that no kinetic resolution of racemic epoxides was possible with this class of catalysts, even when the catalyst was derived from a chiral salen ligand. However, it was shown that if enantiomerically pure styrene oxide was used as substrate, then enantiomerically pure styrene carbonate was formed. On the basis of the kinetic and other experimental data, a catalytic cycle that explains why the bimetallic complexes display such high catalytic activity has been developed.

Syntheses, Structures, and Luminescent Properties of Isomorphous Hydroxo-Bridged Aluminum(III) and Indium(III) Compounds with 2-(2-Hydroxyphenyl)benzimidazole

Two new neutral isomorphous AlIII and InIII complexes [(M(pbm)2(μ-OH))2]·8C2H5OH·2H2O [Hpbm = 2-(2-hydroxylphenyl)benzimidazole, M = Al (1) and In (2)] featuring [M2(μ-OH)2] cores have been synthesized. The molecular orbital calculations show that the luminescent properties are π→π* transition-like in nature. The spectroscopic variations along with the effect of the metal core are also discussed.