The Lewis acidities of as eries of [n]magnesocenophanes (1a-d)h ave been investigatedc omputationally and found to be af unctiono ft he tilt of the cyclopentadienyl moieties. Their catalytic abilities in amine borane dehydrogenation/dehydrocoupling reactions have been probed, and C[1]magnesocenophane (1a)h as been shown to effectively catalyze the dehydrogenation/dehydrocoupling of dimethyl-amine borane (2a)a nd diisopropylamine borane (2b)u nder ambient conditions. Furthermore, the mechanism of the reaction with 2a has been investigated experimentally and computationally,a nd the results imply al igand-assisted mechanism involving stepwise protona nd hydride transfer, with dimethylaminoborane as the key intermediate. [a] E = bridginga tom(s) of ansa bridge;[ b] n = number of bridging atom(s) in ansa bridge.Scheme6.Reactionofm agnesium complex 5 with 2,2-dicyclopentadienylpropanetog ive magnesocenophane 1a.Scheme8.Simplified proposed catalytic cycle (coordinating solventm olecules omitted) for the dehydrogenation of Me 2 NH·BH 3 (2a)and Me 2 NHÀBH 2 ÀNMe 2 À BH 3 (3b)t oc yclic diborazane 3a,catalyzedbym agnesocenophane 1a.Scheme7.Dehydrocoupling of Me 2 NHÀBH 2 ÀNMe 2 ÀBH 3 (3b)catalyzed by 1a. Figure 10. Calculated reaction pathwaysfor the dehydrogenation of dimethylamine borane (2a)v ia dimethylaminoborane (4a), catalyzed by 1a·dme (calculated at the B3LYP-D3/def2-TZVP leveloft heory [11] ;hydrogena toms of CH 2 and CH 3 groupso mittedf or clarity).

Several stannocene carbene complexes, 3a-3g, were synthesized and examined in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction. In this new class of metallocene carbene complexes, coordination of the carbene to the tin atom was found to be comparably weak and mostly due to attractive dispersion forces, as indicated by density functional theory calculations. Furthermore, coordination of the N-heterocyclic carbenes results in a weakening of the Sn-Cp bonds, making these complexes very reactive and short-lived at room temperature.

The application of C[1]magnesocenophanes in dehydrocoupling catalysis is reported. Two new cycloalkylidenebridged C[1]magnesocenophanes were synthesized and structurally characterized. These C[1]magnesocenophanes were used as catalysts in amine−borane dehydrocoupling and, more extensively, in amine−silane cross-dehydrocoupling. The substrate scope, involving different aliphatic, aromatic, and benzylic amines, was probed and the mechanism of this cross-dehydrocoupling catalysis was investigated.

Metallocenes with interlinked cyclopentadienidel igands are commonly referred to as ansa-metallocenes or metallocenophanes.T hese can have drastically different properties than their unbridged parentc ompounds. While this concept is best known for transition metalss uch as iron, it can also be adopted form any main-group elements. This review aims to summarize recent advances in the field of metallocenophanes based on main-group elements of group 2, group 13, group 14 and group 15, focusingo ns ynthesis, structure and properties of these compounds.

In contrast to Brønsted and other Lewis acids ClTi(OiPr)3 is especially suited to catalyze the formation of amino‐substituted coumarins from aminophenols and functionalized β‐oxo esters in a Pechmann condensation. This straightforward protocol allows the synthesis of fluorescence labels and false fluorescent neurotransmitters.