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

Wang, Yu‐Zhong; Bhandari, Sonali; Parkin, Sean; Atwood, David A.

doi:10.1016/j.jorganchem.2003.12.011

Cited by 15 publications

(12 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Complexes 1a and 1c have previously been prepared by a different route18,19 and used to catalyse asymmetric Michael additions 19. The X‐ray structure of complexes 1c 20 and 1d 21 have previously been reported, and the mass spectra of compounds 1a – h confirmed their dimetallic structures (see Supporting Information).…”

Section: Resultsmentioning

confidence: 88%

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts

2007

View full text Add to dashboard Cite

show abstract

Section: Resultsmentioning

confidence: 88%

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts

2007

View full text Add to dashboard Cite

show abstract

“…A search of the Cambridge Structure Database (version 5.30 with updates to May 2009), [32] revealed that bimetallic complexes of the form [{MA C H T U N G T R E N N U N G (salen)} 2 O] have been structurally characterised for iron, [33] aluminium, [34] manganese, [35] chromium [36] and nickel. [37] Since the bimetallic aluminium-A C H T U N G T R E N N U N G (salen) complex 9 a had been reported to be an effective Lewis acid for Michael additions, [31c, 38] cyanohydrin synthesis [39] and Passerini-type reactions, [40] it appeared reasonable that it may have activity in cyclic carbonate synthesis as well.…”

Section: Resultsmentioning

confidence: 99%

“…[34] The Al-O-Al linkage is almost linear in both molecules (172.52 (15) and 170.47(15)8); this angle varies considerably in the related structures, in the range 152.0-174.48. [34] Complex 9 a was then tested as a catalyst for the synthesis of styrene carbonate from styrene oxide under the standard conditions shown in Scheme 2 and the results are presented in Table 2. Complex 9 a alone was also found to be catalytically inactive even at elevated pressure and temperature (entry 1, Table 2) and DMAP was not an effective cocatalyst (entry 2, Table 2).…”

Section: Entry Catalystmentioning

confidence: 99%

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

Clegg¹,

Harrington²,

North³

et al. 2010

Chemistry A European J

367

174

View full text Add to dashboard Cite

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.

show abstract

“…In such chelates, the τ (Tau) parameter allows a quantitative measure of the distortion from perfectly square pyramidal (SP) or trigonal bipyramidal (TBP) geometry for five-coordinate metal complexes. 22,32,33,34,35,36,37,38 The broad range of τ values typically encountered in Salensupported Group 13 metal complexes reflects how the metal coordination geometry may be affected/tuned by the salen backbone and substituents. 22,39,40 Based on literature data, Salen-Group 13 complexes incorporating a flexible and thus less constraining linker, i.e.…”

Section: (Figures S1-s3 In Esi)mentioning

confidence: 99%

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

et al. 2017

View full text Add to dashboard Cite

A series of mononuclear salen-supported gallium amido/alkoxide derivatives were prepared and structurally characterized and subsequently used as initiators in rac-lactide ring-opening polymerisation (ROP). The reaction of variously substituted salen ligands (1a-1f) with 0.5 equiv. of Ga(NMe) allowed the isolation of the corresponding (salen)Ga-NMe chelates (2b-2d, 2f) via an amine elimination route, as poorly soluble compounds in common solvents. The (salen)Ga-OBn derivatives (3a-3e) may be readily accessed by an amine-elimination/alcoholysis sequence and the molecular structures of 3a, 3d and 3e were confirmed through X-ray crystallography diffraction analysis. The present (salen)Ga-X species may effectively mediate the iso-selective ROP of rac-LA in a controlled manner (P up to 0.77 using a 1/1 2f/BnOH mixture as ROP initiator), with a ROP activity greatly dependent upon steric hindrance and geometrical constraints imposed by the variously substituted salen ligands. Based on the present study, salen ligands with limited steric hindrance and a certain degree of flexibility appear best suited for iso-selective ROP by (salen)Ga chelates. The salen-gallium complex 3a is also effective for the controlled ROP of ε-caprolactone (CL) and the production of PCL-b-PLA copolymers.

show abstract

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

Cited by 15 publications

References 34 publications

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts

Synthesis of Cyclic Carbonates from Atmospheric Pressure Carbon Dioxide Using Exceptionally Active Aluminium(salen) Complexes as Catalysts

Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium–Salen Complexes

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

Contact Info

Product

Resources

About