Reactivity of an NHC-stabilized pyramidal hydrosilylene with electrophilic boron sources. Issue 17 (11th April 2019)

• Record Type: Journal Article
• Authors: Dübek, Gizem; Franz, Daniel; Eisenhut, Carsten; Altmann, Philipp J.; Inoue, Shigeyoshi
• Is Part Of: Dalton transactions. Volume 48:Issue 17(2019)
• Page Start: 5756
• Page End: 5765
• Publication Date: 2019-04-11
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9dt00608g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : An NHC-stabilized three-coordinate hydrosilylene dehydrogenates ammonia borane and forms more stable complexes with BH3, BPh3, BBr3 and BPhBr2 but less stable ones with BF3, and BCl3 for which ligand scrambling occurs. Abstract : Silylenes have become an indispensable tool for molecular bond activation. Their use for the construction of silicon–boron bonds is uncommon in comparison to the numerous studies on silylene-derived silicon-element bond formations. Herein we investigate the reactivity of the pyramidal NHC-coordinated hydrosilylene t Bu3 SiSi(H)L Me4 (1 ; NHC = N-heterocyclic carbene, L Me4 = 1, 3, 4, 5-tetramethylimidazolin-2-ylidene) with various boron-centered electrophiles. The reaction of1 with THF·BH3 or H3 N→BH3 afforded the silylene complex1 →BH3 or the product of insertion of the silicon(ii ) atom into an N–H bond with concomitant dehydrogenation along the HN–BH moiety (2 ). The respective conversion of1 with BPh3 yields1 →BPh3 which readily reacts with excess L Me4 to form the more stable complex L Me4 →BPh3 with release of1 . Treatment of1 with the haloboranes Et2 O→BF3, BCl3, BBr3 and Me2 S→BBr3 resulted in the formation of the Lewis acid base adducts1 →BX3 (X = F, Cl, Br) and an equilibrium with their auto-ionization products [1 2 BX2 ] + [BX4 ] − slowly develops. The ratio of1 →BX3 significantly increases with rising atomic number of the halide, thus1 →BF3 majorly transforms within hours while1 →BBr3 is near-quantitatively retained over time. Accordingly, the complex1 →BPhBr2 was isolated after conversion of1 with PhBBr2 .