Aluminum complexes incorporating symmetrical and asymmetrical tridentate pincer type pyrrolyl ligands: synthesis, characterization and reactivity study.

A series of aluminum complexes incorporating substituted symmetrical and asymmetrical tridentate pyrrolyl ligands are synthesized conveniently and the treatment of the derivatives with small organic molecules are analyzed. The reaction of lithiated [C4H2NH(2-CH2NH(t)Bu)(5-CH2NR1R2)], where for 1, R1 = R2 = Me; 2, R1 = H, R2 = (t)Bu, with AlCl3 in diethyl ether affords Al[C4H2N(2-CH2NH(t)Bu)(5-CH2NMe2)]Cl2 (3) and Al[C4H2N(2,5-CH2NH(t)Bu)2]Cl2 (4), respectively, in high yields. Furthermore, subjecting 3 and 4 to reaction with one equiv.

Deprotonation and reductive addition reactions of hypervalent aluminium dihydride compounds containing substituted pyrrolyl ligands with phenols, ketones, and aldehydes.

The reactivities of [C4H2N(CH2NMe2)2]AlH2 (1) with primary and secondary amines, phenols, ketones, and phenyl isothiocyanate were examined. Reactions of 1 with one or two equivalents of 2,6-dichloroaniline in methylene chloride generated [C4H2N(CH2NMe2)2]AlH(NHC6H3-2,6-Cl2) (2) and [C4H2N(CH2NMe2)2]Al(NHC6H3-2,6-Cl2)2 (3), respectively, following hydrogen elimination. Similarly, the reactions of 1 with one or two equivalents of carbazole afforded [C4H2N(CH2NMe2)2]AlH(NC12H8) (4) or [C4H2N(CH2NMe2)2]Al(NC12H8)2 (5) by deprotonating the acidic N-H of carbazole.

Robust and electron-rich cis-palladium(II) complexes with phosphine and carbene ligands as catalytic precursors in Suzuki coupling reactions.

A new imidazolinium ligand precursor [L(2)H]Cl (2) was prepared in 86 % yield. Compared with its imidazolium counterpart, [L(1)H]Cl (1), 2 is very sensitive to moisture and can undergo ring-opening reactions very readily. Palladium complexes with the ring-opened products from imidazolinium salts were isolated and characterized by X-ray crystallography.

Cis-trans isomerizations of beta-carotene and lycopene: a theoretical study.

The all-trans to mono-cis isomerizations of polyenes and two C40H56 carotenes, beta-carotene and lycopene, at the ground singlet (S0) and triplet (T1) states are studied by means of quantum chemistry computations. At the S0 state of polyenes containing n acetylene units (Pn), we find that the energy barrier of the central C=C rotation decreases with n. In contrast, however, at the T 1 state, the rotational barrier increases with n.

Theoretical study of the enthalpies of formation for C40H56 carotenes.

Theoretical study of the enthalpies of formation (DeltaHf) for polyenes up to nine ethylene units and for several C40H56 carotenes including beta-carotene, alpha-carotene, lycopene, and prolycopene is presented. For polyenes and small branched alkenes, we used G2, G3, and G3MP2B3 theories, and the DeltaHf values were evaluated with the atomization, isodesmic bond separation, and homodesmic schemes. The applicability of six DFT functionals were evaluated by comparing their predictions with those obtained using G3 theory within the atomization scheme.