Titanium Carbene Complexes Stabilized by Alkali Metal Amides.

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 Me TACD [(Me 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 CH group of the trimethylsilymethyl ligand. The nucleophilic character of the carbene carbon atom was shown by the reaction with benzophenone and terminal acetylenes.

Mononuclear Alkali Metal Organoperoxides Stabilized by an NNNN-Macrocycle and Short Hydrogen Bonds from ROOH Molecules.

A series of light alkali metal organoperoxides [MOOR] (M=Li, Na, K; R=tBu, CMe Ph) were isolated in mononuclear form, aided by the tetradentate and neutral NNNN-type macrocycle Me TACD (L; Me [12]aneN =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-H⋅⋅⋅O contacts, in the case of the Na derivative as short as 2.41 Å.

Ligand Influence on Carbonyl Hydroboration Catalysis by Alkali Metal Hydridotriphenylborates [(L)M][HBPh ] (M=Li, Na, K).

Alkali metal hydridotriphenylborates [(L )M][HBPh ] (L =Me TREN; M=Li, Na, K) chemoselectively catalyze the hydroboration of carbonyls and CO , with lithium being the most active system. A new series of complexes [(L )M][HBPh ] [M=Li (1), Na (2), K (3)] featuring the cyclen-derived macrocyclic polyamine Me TACD (L ) 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 [HBPh ] anion from lithium to potassium.

Facile ring-opening of THF at a lithium center induced by a pendant Si-H bond and BPh.

The macrocyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane [LH = (MeTACD)H] formed adducts with tetramethyl-silazides [M{N(SiHMe)}] (M = Li, Na, K) of light alkali metals. Upon heating, intramolecular dehydrocoupling occurred to give [M{(L)SiMeN(SiHMe)}]. BPh induced facile ring-opening of THF when reacted with [Li{(L)SiMeN(SiHMe)}].

Ring-opening of cyclic ethers by aluminum hydridotriphenylborate.

Molecular aluminum hydride [(L)AlH] (L = MeTACD) reacted with 2 equiv. of BPh in THF or THP to give the cationic alkoxides [(L)Al(OR)][HBPh] (R = nBu, nPent) by facile ring-opening of the cyclic ethers. The C-O bond cleavage which involves the isolable intermediate [(L)AlH][HBPh] is a result of hydride transfer to C from [HBPh].

Artificial Diels-Alderase based on the transmembrane protein FhuA.

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.

Alkali Metal Hydridotriphenylborates [(L)M][HBPh3] (M = Li, Na, K): Chemoselective Catalysts for Carbonyl and CO2 Hydroboration.

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.