Evidence for the trans-influence of axial substituents as a significant factor determining the structure and stability of five-coordinate complexes: molecular structure of the first simple five-coordinate dialkylaluminum O,O′-chelate complex

Lewiński, Janusz; Goś, Piotr; Kopeć, Tomasz; Lipkowski, Janusz; Luboradzki, Roman

doi:10.1016/s1387-7003(99)00094-5

Cited by 17 publications

(6 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Al and Ga atoms are displaced by 0.250(3) and 0.314(5) Å, respectively, out of the almost flat ligand plane. We demonstrated recently that for unsaturated bidentate ligands the strength of the interaction between donor sites and the metal center is significantly controlled by the conformation of the chelate heterocyclic ring . Hence , it is reasonable to assume that the conformation of the heterocyclic ring in 1 and 2 , in the absence of steric hindrances, results from the intermolecular noncovalent forces.…”

Section: Resultsmentioning

confidence: 99%

Structure Investigations of Group 13 Derivatives of N-Phenylsalicylideneimine

et al. 2003

Self Cite

View full text Add to dashboard Cite

The reaction of MMe3 with 1 molar equiv of N-phenylsalicylideneimine (HsaldPh) yields the O,N-chelate complexes Me2M(saldPh) (where M = Al (1), Ga (2), In (3)) in high yields. The reaction of 1 with γ-picoline results in a ligand redistribution reaction and the formation of the five-coordinate complex MeAl(saldPh)2 (4), while the gallium and indium compounds are stable in the presence of γ-picoline. The resulting compounds have been characterized in a solution by NMR and IR spectroscopy and cryoscopic molecular weight measurements, and their molecular and crystal structure have been determined by X-ray crystallography. Compounds 1 and 2 exist as monomeric tetrahedral complexes, while the indium analogue 3 is dimeric with the In2(μ-O)2 bridges and five-coordinate metal centers. The five-coordinate methylaluminum compound 4 exhibits trigonal-bipyramidal geometry of the metal center. The obtained results show that a Schiff base acts as a strongly coordinating chelate ligand and, in this regard, it resembles the symmetrical acetylacetonato ligand and related β-diketonates. An extended crystal structure analysis reveals that the isostructural crystalline complexes 1 and 2 comprise monomeric four-coordinate molecules linked by C−Himino···O hydrogen bonds, forming helical chains. Parallel left- and right-handed helices joined by C−H···π interactions give rise to the 3D extended tetragonal framework, with voids filled by solvent molecules. In the crystalline complex 4 the C−Haryl···O hydrogen bonds organize molecules into H-bonded dimers.

show abstract

Section: Resultsmentioning

confidence: 99%

Structure Investigations of Group 13 Derivatives of N-Phenylsalicylideneimine

et al. 2003

Self Cite

View full text Add to dashboard Cite

show abstract

“…Resonances for six-coordinate aluminum generally appear at ∼10 ppm, while those for four-coordinate aluminum appear at ∼150 ppm . The more rare five-coordinate aluminum resonances generally appear at ∼100 ppm . Thus, the resonance observed for 1 is best interpreted as being six-coordinate, although it is hard to visualize how this occurs since any dimerization would lead to a maximum of five-coordination.…”

Section: Resultsmentioning

confidence: 99%

Group 13 Cation Formation with a Potentially Tridentate Ligand

et al. 2000

View full text Add to dashboard Cite

A potentially tridentate ligand, Phensal(tBu)H 3 , was prepared by the condensation of 1 equiv of phenylenediamine with 3,5-di-tert-butylsalicylaldehyde. When 1 equiv of this new ligand is added to AlMe 3 , [[Phensal(tBu)HAlMe]] 2 (1) results. In contrast, this reaction with GaMe 3 produces [Phensal(tBu)H 2 ]GaMe 2 (2). When 1 or 2 equiv of Phensal(tBu)H 3 is combined with Et 2 AlCl, the complex [Phensal(tBu)] 2 AlCl (3) forms. However the same reaction with Me 2 GaCl leads to [Phensal(tBu)H 2 ]Ga(Me)Cl (4). A cationic complex, {[Phensal(tBu)] 2 Al} + Cl -(5), is formed when 3 is dissolved in MeOH. The MeOH apparently mediates the formation of the cation but does not coordinate the cationic metal. When the solvent is removed, 5 reverts back to neutral 3. When 3 is combined with GaCl 3 in toluene, another cationic complex, {[Phensal(tBu)H 2 ] 2 Al} + GaCl 4 -(6), is formed. In a similar manner, {[Phensal(tBu)H 2 ] 2 Al} + Me 2 AlCl 2 -(7) is formed by adding Me 2 AlCl to 3. The compounds were characterized by mp, elemental analyses, IR, 1 H and 27 Al NMR, and in the case of 2, 5, and 6 single-crystal X-ray analysis.Supporting Information Available: Crystallographic data for compounds 2, 5, and 6, which includes full tables of bond lengths and angles, full atom-labeled ORTEP views, and unit cell views. This material is available free of charge via the Internet at http://pubs.acs.org. Observed and calculated structure factor tables are available upon request. This data may also be obtained at the Cambridge Crystallographic Database (CCDC 139436, 139437, 139438).

show abstract

“…The coordination sphere of the central gallium atoms can be described as distorted trigonal bipyramidal, with the angle defined by the axial substituents of 145.9°(1). The Ga(1)−O(1), 1.951(3) Å, and Ga(1)−O(1‘), 1.991(3) Å, bridge-bond distances differ in length, which is a typical feature of the dimeric five-coordinate group 13 organometallic alkoxides, [R 2 M(μ- O,O ‘ )] 2 . , The observed nonequivalency of the Ga−O bridging distances in 2 is smaller than that in the related derivative of ethylene glycol monomethyl ether, [Me 2 Ga(μ-OC 2 H 4 OCH 3 )] 2 (the corresponding Ga−O distances are 1.934(6) and 2.012(7) Å, and the Ga−O axial distance is 2.624(6) Å),6b which is consistent with the diversified trans influence of axial substituents, i.e., the terminal axial bond in 2 is weaker than that in the α-hydroxy ether derivatives and the trans influence effects the intramolecular geometry less. The Ga(1)−O(2) bond distance of 2.886(3) Å is significantly shorter than the sum of the van der Waals radii of oxygen and gallium (3.39 Å), , however, it is noticeably longer than the corresponding bond distances in the dialkylgallium derivatives of α-hydroxy ethers. 6a,b We also note that there is significant widening of O(1)−Ga(1)−C angles by 5−6° compared to O(1‘)−Ga(1)−C angles.…”

mentioning

confidence: 99%