C-H bond activation during and after the reactions of a metallacyclic amide with silanes: formation of a μ-alkylidene hydride complex, its H-D exchange, and β-H abstraction by a hydride ligand.

Metallacyclic complex [(Me2N)3Ta(η(2)-CH2SiMe2NSiMe3)] (3) undergoes C-H activation in its reaction with H3SiPh to afford a Ta/μ-alkylidene/hydride complex, [(Me2N)2{(Me3Si)2N}Ta(μ-H)2(μ-C-η(2)-CHSiMe2NSiMe3)Ta(NMe2)2] (4). Deuterium-labeling studies with [D3]SiPh show H-D exchange between the Ta-D-Ta unit and all methyl groups in [(Me2N)2{(Me3Si)2N}Ta(μ-D)2(μ-C-η(2)-CHSiMe2NSiMe3)Ta(NMe2)2] ([D2]-4) to give the partially deuterated complex [Dn]-4. In addition, 4 undergoes β-H abstraction between a hydride and an NMe2 ligand and forms a new complex [(Me2N){(Me3 Si)2N}Ta(μ-H)(μ-N-η(2)-C,N-CH2NMe)(μ-C-η(2)-C,N-CHSiMe2NSiMe3)Ta(NMe2)2] (5) with a cyclometalated, η(2)-imine ligand.

Reactions of d(0) tungsten alkylidyne complexes with O2 or H2O. Formation of an oxo siloxy complex through unusual silyl migrations.

(Me3SiCH2)3(Me3SiC≡)W←O=PMe3 (1), an adduct between (Me3SiCH2)3W≡CSiMe3 (2) and O=PMe3, reacts with O2 to give O=W(OSiMe3)(CH2SiMe3)3 (3) and CO2. Reaction of 2 with H2O yields 3 and the trimer [(μ-O)W(CH2SiMe3)2(=O)(THF)]3 (4). In the reaction of D2O with 2, 3-d(n) and methane isotopologues CH2D2, CHD3 and CD4 have been observed.

Synthesis of a C-linked hyaluronic acid disaccharide mimetic.

The synthesis of a C-disaccharide that is designed as a mimetic for the repeating unit disaccharide of hyaluronic acid is described. The target compound was obtained via the SmI2-promoted coupling reaction of the sulfone, 2-acetamido-4,6-O-benzylidene-3-O-tert-butyldimethylsilyl-1,2-dideoxy-1-pyridinylsulfonyl-beta-D-glucopyranose (6), and the aldehyde, p-methoxyphenyl 2,3-di-O-benzyl-4-deoxy-4-C-formyl-6-O-p-methoxybenzyl-beta-D-glucopyranoside (14).

A pair of epimeric 13-hydroxy-2,3,6,7-tetramethoxy-8b,11,12,12a,13,13a-hexahydro-9H-9a-azacyclopenta[b]triphenylene-10-ones.

The structures of two compounds which are intermediates in the synthesis of phenanthroindolizidine alkaloids have been determined. (8bS,13aS,14R,14aR)-8b,9,11,12,13,13a,14,14a-Octahydro-14-hydroxy-2,3,6,7-tetramethoxydibenzo[f,h]pyrrolo[1,2-b]isoquinolin-11-one acetone solvate, C24H27NO6.C3H6O, (II), crystallizes in a chiral space group with one solvent molecule (acetone) present in the asymmetric unit.

Synthesis, characterization, and theoretical studies of group 4 amido hydrotris(pyrazolyl)borate complexes.

Titanium and zirconium amido complexes containing a hydrotris(pyrazolyl)borate (Tp) or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand TpM(NMe(2))(3) (M = Ti, 1; M = Zr, 2) and Tp*M(NMe(2))(3) (M = Ti, 3; M = Zr, 4) were prepared by the reactions of M(NMe(2))(3)Cl (M = Ti, Zr) with sodium hydridotris(pyrazol-1-yl)borate and potassium hydridotris(3,5-dimethylpyrazol-1-yl)borate, respectively. The structures of 1, 2, and 4.CH(2)Cl(2) were determined by X-ray diffraction and show octahedral coordination geometry around the metal centers.

Direct observation of eta 2-imine formation through beta-H abstraction between amide ligands. Neutron and X-ray diffraction structure of a dihydride imine ditantalum complex.

Reactions of Ta(NMe2)5 with D2SiR'Ph (R' = Me, Ph) were found to give a dideuteride eta 2-imine complex (Me2N)3Ta(mu-D)2(mu-N-eta 2-N,C-CH2NMe)Ta(NMe2)3(1-d2) through C-H activation of an amide ligand via beta-H abstraction, and the structure of 1 was confirmed by single crystal neutron and X-ray diffraction.