Cross-Dehydrocoupling of Amines and Silanes Catalyzed by Magnesocenophanes

Abstract

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.

Constrained Geometry ansa‐Half‐Sandwich Complexes of Magnesium – Versatile s‐Block Catalysts

“…Literature known ansa-half-sandwich ligands [50][51][52][53] were reacted with dibutylmagnesium to obtain the corresponding ansa-halfsandwich magnesium complexes 1 a-d (Scheme 1). Similar to magnesocenophanes, [24,25,[54][55][56] 1 a-d possess Lewis acidic magnesium atoms and crystalized as solvent adducts from donor solvent (Figure 1, S14-S18). In case of 1 a-c, mono dme adducts are observed in the solid state, with the dme molecule coordinated to the magnesium atom via both oxygen atoms and the magnesium atom exhibiting an η 5 coordination mode to the Cp group.…”

“…Recently, we demonstrated that [1]magnesocenophanes are potent catalysts in the dehydrocoupling of amine-boranes. [24,25] While many magnesium based catalysts require elevated temperatures to operate, [26][27][28][29] [1]magnesocenophanes were able to catalyze the dehydrocoupling reactions of different dialkylamine-boranes at room temperature. [24,25] We therefore started our investigations into the catalytic abilities of ansa-halfsandwich magnesium complexes 1 a-d by testing their performance in the dehydrocoupling of amine-boranes.…”

N-Silylamines in catalysis: synthesis and reactivity

“…In 2021, the Scha ¨fer group reported the first example of C [1]magnesocenophanes for the dehydrogenative coupling of amines with silanes. 37 There was limited reactivity with this catalytic system and better conversions and selectivity were obtained when amine was coupled with diphenylsilane as compared to phenylsilane.…”

Silicon–nitrogen bond formation via dealkynative coupling of amines with bis(trimethylsilyl)acetylene mediated by KHMDS

“…The dehydrocoupling between amines and hydrosilanes seems to be the most attractive route, due to the formation of H 2 as the by-product (Figure 1, c). [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Unfortunately, this approach is completely impractical for the preparation of a highly important trimethylsilyl-protecting group, due to the pyrophoricity of gaseous Me 3 SiH. Moreover, the control of the chemoselectivity for Si-H/N-H dehydrocoupling has proved to be challenging due to the possible formation of several products including polymeric silazanes and a mixture of mono-and di-silylated amines.…”

“…1c). [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Unfortunately, this approach is completely impractical for the preparation of a highly important trimethylsilyl-protecting group, due to the pyrophoricity of gaseous Me 3 SiH. Moreover, the control of the chemoselectivity for Si-H/N-H dehydrocoupling has proved to be challenging due to the possible formation of several products including polymeric silazanes and a mixture of mono-and disilylated amines.…”