Steric Effects in Aluminum Compounds Containing Monoanionic Potentially Bidentate Ligands: Effect of the Steric Bulk at the α-Carbon

Article type: Research Article

Authors: McMahon, C. Niamh | Bott, Simon G. | Barron, Andrew R.

Affiliations: Department of Chemistry, Rice University, Houston, Texas 77005 | Department of Chemistry, University of Houston, Houston, Texas 77204

Note: [] Corresponding author. (http://pcheml.rice.edu/∼arb/Barron.html)

Abstract: Reaction of [(iBu)2AlH]2 with l-ephedrine yields [(iBu)2A1{μ-OC(H)(Ph)CH(Me)N(H)Me}]2 (1). Reaction of Al(tBu)3 with (2S,3R)-(+)-4-(dimethylamino)-l,2-diphenyl-3-methyl-2-butanol (Chirald®) yields (tBu)2Al[OC(CH2Ph)(Ph)CH(Me)CH2NMe2] (2). The molecular structures of compounds 1 and 2 have been determined by X-ray crystallography. Compound 2 is monomeric with a six membered chelate heterocyclic ring. In contrast, compound 1 exists as a bridged dimer. The formation of monomeric chelate species for compound 2, rather than the alkoxide bridged dimer as is found for 1 is found to be due to the steric bulk of the aluminum alkyl and substitution at the ligand’s α-carbon. Crystal data: (1) orthorhombic, P212121, a=10.987(2), b=18.795(4), c =19.270(4) Å, V=3979(1) Å3, Z=4, R=0.1056, Rw=0.2454. (2) tetragonal, 14, a=22.236(3), c=10.784(1) Å, V=5332.0(5) Å3, Z=8, R=0.0485, Rw=0.0537.

DOI: 10.1080/13583149912331338971

Journal: Main Group Chemistry, vol. 3, no. 1, pp. 43-51, 1999