Organoaluminium complexes with sterically demanding oximato ligands: does a bulky and rigid ligand backbone change the aggregation motif?

Abstract

The four organoaluminium ketoximates [(2,4-dimethylpentane-3-one oximato)AlMe(2)](2) (1), (meso)-[(norcamphor oximato)AlMe(2)](2) (2), {[(R,R)-camphor oximato]AlMe(2)}(3) (3) and {[(R,S)-fenchone oximato]AlMe(2)}(2) (4) have been prepared by the reactions of the corresponding oximes with trimethylaluminium. All compounds have been fully characterized by means of IR, mass and multi-nuclear NMR spectroscopy ((1)H, (13)C, (27)Al) and by elemental analyses. The crystal structures of three of these compounds (2, 3 and 4) were determined, revealing the aggregation motif of organometallic group 13 oximates to vary from the hitherto predominant six-membered dimeric M(2)N(2)O(2) array to others (six-membered M(3)O(3) core ring in the case of the camphor derivative; five-membered M(2)NO(2) core ring in the case of the fenchone derivative) so far only found e.g. in hydroxylamino complexes of group 13 metals. Furthermore, complexes 3 and 4 exhibit an unusual behaviour in solution, as indicated by upfield-shifted additional signals in their (27)Al NMR spectra, pointing at aluminium atoms in penta- or hexacoordination, respectively.

Synthesis and Structural Studies of Chiral Indium(III) Complexes Supported by Tridentate Diaminophenol Ligands

“…The emergence of indium as an important Lewis acid catalyst and the relative paucity of indium complexes supported by chiral ligands ,− emphasize the importance of developing well-characterized chiral indium complexes. − In this work, we present our investigations into the coordination chemistry and structural characteristics of a family of indium(III) complexes supported by a chiral tridentate diaminophenol ligand, H(NN H O), and provide explanations for the significant halide effect observed in these systems.…”

Boron, aluminium, gallium, indium and thallium

“…186 Using oximes of varying steric demand and/or skeleton rigidity, andwith two adjacent donor atoms, it was shown that the core structure changes from Al 2 N 2 O 2 , using 2,4-dimethylpentane-3-one oxime or (rac)-bicyclo[2,2,1]heptane-2-one oxime, to Al 3 O 3 , using (1R,4R)-1,7,7-trimethylbicyclo[2,2,1]heptane, to Al 2 NO 2 , with (1R,4S)-1,3,3-trimethylbicyclo[2,2,1]heptane-2-one oxime, the first two are of hexagonal shape and the latter is pentagonal. 187 The ligand 2,6-di(4-t-butylphenyl)phenyl is sterically demanding and suitable for the synthesis of new Group 13 complexes. The aluminium and gallium derivatives are similar in formulation, [2,6-(4-t-BuC 6 H 4 ) 2 C 6 H 3 ] 2 MX 2 Á OEt 2 (M = Al, X = Br; M = Ga, X = Cl), but structurally the aluminium-containing complex, although four coordinated, is closer to a distorted trigonal planar geometry, as bond angles show.…”

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies

“…Nevertheless, a limited number of metal complexes with oximate ligands have been reported in the literature using different transition and block f metals [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. Only two papers describing potassium complexes using oximate ligands have been published.…”