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Die α‐H‐Eliminierung in Tetrakis(trimethylsilylmethyl)titan‐Vorstufen unter Bildung von (Alkyliden)bis(alkyl)titan‐Komplexen wird durch Metallamide leichter Alkalimetalle mit makrozyklischen Liganden Me3TACD [(Me3TACD)H=1,4,7‐Trimethyl‐1,4,7,10‐tetraazacyclododecan] vom NNNN‐Typ hervorgerufen. Im Kristall wechselwirkt das Alkalimetall mit dem Carben‐Kohlenstoffatom oder der CH2‐Gruppe des Trimethylsilymethylliganden. Der nukleophile Charakter des Carben‐Kohlenstoffatoms wurde durch die Reaktionen mit Benzophenon und mit terminalen Acetylenen gezeigt. Eine leichte α‐H‐Eliminierung in Tetrakis(trimethylsilylmethyl)titan durch Alkalimetallamide mit makrozyklischen Me3TACD‐Liganden führt zu (Alkyliden)bis(alkyl)titan‐Komplexaddukten. Im Kristall wechselwirkt das Alkalimetall mit dem Carben‐C‐Atom oder der CH2‐Gruppe des Trimethylsilymethylliganden. Der nukleophile Charakter des Carben‐C‐Atoms wurde durch Reaktionen mit Benzophenon und terminalen Acetylenen demonstriert. [ABSTRACT FROM AUTHOR]

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 Me3TACD [(Me3TACD)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. Facile α‐H elimination from tetrakis(trimethylsilylmethyl)titanium is induced by alkali metal amides to give adducts of (alkylidene)bis(alkyl)titanium complexes. 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 reactions with benzophenone and terminal acetylenes. [ABSTRACT FROM AUTHOR]

A series of light alkali metal organoperoxides [MOOR] (M=Li, Na, K; R= tBu, CMe2Ph) were isolated in mononuclear form, aided by the tetradentate and neutral NNNN-type macrocycle Me4TACD (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−H⋅⋅⋅O contacts, in the case of the Na derivative as short as 2.41 Å. [ABSTRACT FROM AUTHOR]

Alkali metal hydridotriphenylborates [(L1)M][HBPh3] (L1=Me6TREN; 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 Me4TACD (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. [ABSTRACT FROM AUTHOR]

Triphenylborane (BPh3) abstracted the β-SiH in [(L)M{N(SiHMe2)2}] (L = Me6TREN; M = Li, Na, K) in THF to give the hydridotriphenylborates [(L)M][HBPh3]. Reactions in benzene favored silazide instead of hydride abstraction to give [(L)M][Ph3B-N(SiHMe2)2]. The hydridotriphenylborates [(L)M][HBPh3] catalyzed the chemoselective hydroboration of benzophenone by pinacolborane (HBpin), with the lithium derivative being the most active. The solution structure of [(L)Li][HBPh3] was qualitatively investigated in the context of its superior catalytic activity. Fluxional coordination of L in [(L)Li(THF)]+ in tandem with a THF solvent molecule was revealed by NMR spectroscopy. para-Substituents in [HB(C6H4-p-X)3]- influenced the rate which is apparently determined by the addition of the B-H function to the isolable alkoxy borate intermediate [(L)Li][Ph2CHOBPh3]. [ABSTRACT FROM AUTHOR]

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)}]. [ABSTRACT FROM AUTHOR]

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)}]. [ABSTRACT FROM AUTHOR]

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]−. [ABSTRACT FROM AUTHOR]

Newly prepared copper complexes covalently linked to an engineered variant of ferric hydroxamate uptake protein component A are biohybrid catalysts for the Diels-Alder reaction of a chalcone with cyclopentadiene to give the corresponding endo product. [ABSTRACT FROM AUTHOR]