Timothy S. Keizer

Monomeric Group 13 compounds with bidentate (N,O) ligands

Abstract The bidentate ligand, Sal(tBu)H, is prepared by the condensation of one equivalent of a bulky amine with 3,-5-di-tert-butylsalicylaldehyde. When one equivalent of Sal(tBu)H is added to MR3 or AlMe2Cl, compounds are btained which have the general form: [Sal(tBu)MR2] (with M/R combinations, Al/Me (1), Al/Et (3), Ga/Et (4) and In/Et (5)) and Sal(tBu)AlMeCl (2). The compounds are characterized by melting point, elemental analyses, IR, 1H-NMR, and in the case of 2 and 3 by single-crystal X-ray analysis.

Salen-supported dinuclear and trinuclear boron compounds

Abstract Six boron compounds have been synthesized through the combination of phenylboronic acid and various Salen ( N , N ′-ethylenebis(2-hydroxy)benzylidenimine) ligands. They contain seven- and eight-membered heterocycles with a bridging oxygen and have the formula: L[(PhB) 2 (μ-O)] (L=Acmen ( 1 ), Salen( t Bu) ( 2 ), Sal(2-OH)pen ( 3 ), Salpen( t Bu) ( 4 ), Acpen ( 5 )) and L[B 2 (μ-O)(O 2 BPh)] (L=Acen ( 6 ), Salmen ( 7 )). Compounds 6 and 7 are interesting trinuclear boron derivatives with two four-coordinate and one three-coordinate boron atoms. The compounds have been characterized by MP, MS, IR, EA and 1 H- and 11 B-NMR, by 11 B-MAS for 6 and 7 and by X-ray crystallography for 2 , 4 – 7 .

Chelated aluminum alkoxides

The present contribution will demonstrate that monomeric alkoxide compounds can be formed by the use of the Salen(tBu) ligand. These alkoxides, LAlOR (with L=Salen (tBu), R=Me (1), Salomphen(tBu), R=Me (3) and L=Salen(tBu), R=Et (4)) feature five-coordinate monomeric aluminum (Salen(tBu)=N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine) and Salomphen(tBu)=N,N′-(4,5-di-methyl)phenylenenebis(3,5-di-tert-butylsalicylideneimine). Crystallization of 1 from MeOH affords the six-coordinate complex, Salen(tBu)AlOMe(MeOH) (2). The manner in which these compounds may be obtained, as well as the structures of 2 and 4 will be described

Six-coordinate aluminium cations: characterization, catalysis, and theory

The new thf supported cations, [Salen(tBu)Al(thf)2]+ (2), [Salpen(tBu)Al(thf)2]+ (3), [Salben(tBu)Al(thf)2]+ (4) [Salophen(tBu)Al(thf)2]+ (5) and [Salomphen(tBu)Al(thf)2]+ (6), with BPh4− as the counter anion, have been prepared from salt elimination reactions with the respective Salen(tBu)AlCl reagent, including one that is new, Salben(tBu)AlCl (1). The cations were observed to polymerize propylene oxide. Based upon the results of experimental and theoretical work the mechanism appears to be one in which a carbocation is the propagating species although the PDI values are remarkably low, ≈1.2 in some cases. All of the potential catalysts were characterized spectroscopically and, in the case of 3, by X-ray crystallography.

Dealkylation with boron bromide chelates

Potential two-point Lewis acid compounds can be formed by combining the salen( t Bu)H2 (N ,N ?-alkylenenebis(3,5-di-tertbutyl(2hydroxy)benzylidenimine) class of ligands and its derivatives with boron tribromide. In the present study compounds having the formula, L(BBr2)2 (L� /salen( t Bu) (1), salhen( t Bu) (2), L([ p tolyl]BBr) (L � /salen( t Bu) (3), salpen( t Bu) (4), salben( t Bu) (5), salhen( t Bu) (6), and t Bu-sal( t Bu)BBr2 (7) were prepared. These compounds are active towards the dealkylation of alkyl phosphates and are catalytic when stoichiometric amounts of BBr3 and trimethylphosphate are introduced to the chelate ligand. All of the compounds were characterized by Mp, elemental analysis, 1 H- and 11 B-NMR, IR, MS and in the case of 2 by X-ray crystallography.

Salen Supported Molecular Borosilicates

Various Salen ligands (Salen(tBu)H2=N, N′-ethylenebis(3,5-di-tertbutyl(2-hydroxy)benzylidenimine) were used to prepare borosilyl and μ-O bridged borosilyl compounds having the formula, L{B(OSiMe3)2}2 (L=Salen(tBu) (1), Salpen(tBu) (2), Salben(tBu) (3), Salhen(tBu) (4) and L(BOSiMe3)2(μ-O) (L=Salen(tBu) (5) and Salben(tBu) (6)). In the case of 5 and 6 the formation of the B–O–B linkage takes precedence over the formation of a B–O–Si linkage. All of the compounds were characterized by Mp, elemental analysis, 1H and 11B NMR, IR, MS and in the case of 1, 2, and6 by X-ray crystallography.