RESUMEN
Facile α-H elimination from tetrakis(trimethylsilylmethyl)titanium precursors to give adducts of (alkylidene)bis(alkyl)titanium complexes is induced by light alkali metal amides of the NNNN-type macrocyclic anionic ligand Me3 TACD [(Me3 TACD)H=1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane]. In the crystal, the alkali metal interacts with the carbene carbon atom or with the CH2 group of the trimethylsilymethyl ligand. The nucleophilic character of the carbene carbon atom was shown by the reaction with benzophenone and terminal acetylenes.
RESUMEN
Alkali metal hydridotriphenylborates [(L1 )M][HBPh3 ] (L1 =Me6 TREN; M=Li, Na, K) chemoselectively catalyze the hydroboration of carbonyls and CO2 , with lithium being the most active system. A new series of complexes [(L2 )M][HBPh3 ] [M=Li (1), Na (2), K (3)] featuring the cyclen-derived macrocyclic polyamine Me4 TACD (L2 ) were synthesized in a "one-pot" fashion and fully characterized including X-ray crystallography. In the crystal, 1-3 exhibit wide variation in metal coordination of the [HBPh3 ]- anion from lithium to potassium. The structures differ from those in [(L1 )M][HBPh3 ]. Effects of coordination of L1 , L2 , and other N- and O-donor multidentate ligands on [Li(HBPh3 )] were used to rationalize the catalytic activity in carbonyl hydroboration.
RESUMEN
A series of light alkali metal organoperoxides [MOOR] (M=Li, Na, K; R=tBu, CMe2 Ph) were isolated in mononuclear form, aided by the tetradentate and neutral NNNN-type macrocycle Me4 TACD (L; Me4 [12]aneN4 =1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) and strong hydrogen bonds from additional ROOH molecules. The Na and K compounds are characterized by short O-Hâ â â O contacts, in the case of the Na derivative as short as 2.41â Å.
RESUMEN
Light alkali metal hydridotriphenylborates M[HBPh3] (M = Li, Na, K), characterized as tris{2-(dimethylamino)ethyl}amine (L) complexes [(L)M][HBPh3], act as efficient catalysts for the chemoselective hydroboration of a wide range of aldehydes and ketones using pinacolborane HBpin. The lithium derivative showed a remarkably high TOF of ≥17 s(-1). These compounds also catalyze the hydroborative reduction of CO2 to give formoxyborane HCO2Bpin without any over-reduction.
RESUMEN
Copper(I) and copper(II) complexes were covalently linked to an engineered variant of the transmembrane protein Ferric hydroxamate uptake protein component A (FhuA ΔCVF(tev)). Copper(I) was incorporated using an N-heterocyclic carbene (NHC) ligand equipped with a maleimide group on the side arm at the imidazole nitrogen. Copper(II) was attached by coordination to a terpyridyl ligand. The spacer length was varied in the back of the ligand framework. These biohybrid catalysts were shown to be active in the Diels-Alder reaction of a chalcone derivative with cyclopentadiene to preferentially give the endo product.
RESUMEN
The macrocyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane [LH = (Me3TACD)H] formed adducts with tetramethyl-silazides [M{N(SiHMe2)2}] (M = Li, Na, K) of light alkali metals. Upon heating, intramolecular dehydrocoupling occurred to give [M{(L)SiMe2N(SiHMe2)}]. BPh3 induced facile ring-opening of THF when reacted with [Li{(L)SiMe2N(SiHMe2)}].
RESUMEN
Molecular aluminum hydride [(L)AlH2] (L = Me3TACD) reacted with 2 equiv. of BPh3 in THF or THP to give the cationic alkoxides [(L)Al(OR)][HBPh3] (R = nBu, nPent) by facile ring-opening of the cyclic ethers. The Cα-O bond cleavage which involves the isolable intermediate [(L)AlH][HBPh3] is a result of hydride transfer to Cα from [HBPh3]-.