The activation of B-H and B-Cl bonds in boranes by base-stabilized low-valent silicon compounds is described. The reaction of the amidinato amidosilylene-borane adduct [L{Ar(MeSi)N}SiBH] [1; L = PhC(N tBu), and Ar = 2,6- iPrCH] with MeOTf in toluene at room temperature formed [L{Ar(MeSi)N}SiBHOTf] (2). [LSiN(SiMe)Ar] in compound 2 then underwent a B-H bond activation with BHOTf in refluxing toluene to afford the B-H bond activation product [LB(H)Si(H)(OTf){N(SiMe)Ar}] (3). On the other hand, when compound 2 was reacted with 4-dimethylaminopyridine in refluxing toluene, another B-H bond activation product [(μ-κ1:κ1-L)B(H)(DMAP)Si(H){N(Ar)SiMe}]OTf (4) was afforded. Mechanistic studies show that "(μ-κ1:κ1-L)B(H)(OTf)Si(H){N(Ar)SiMe}" (2A) is the key intermediate in the reactions mentioned above. The formation of 2A is further evidenced by the activation of the B-Cl bond in PhBCl by the amidinato silicon(I) dimer [LSi:] to form the B-Cl bond activation product [(μ-κ1:κ1-L)B(Cl)(Ph)Si(Cl)] (6). Compounds 2-4 and 6 were characterized by nuclear magnetic resonance spectroscopy and X-ray crystallography.

The coordination chemistry of the amidinate-stabilized silicon(I) dimer toward group 9 metal complexes is described. The reaction of [LSi:]2 (1, L = PhC(NtBu)2) with [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) in toluene at ambient temperature afforded the base-stabilized silicon(I) dimer-iridium complex [LSi{Ir(cod)-μ-Cl-Ir(cod)}SiL][(cod)IrCl2] (2). In contrast, the reaction of 1 with [Rh(cod)Cl]2 in toluene at ambient temperature afforded a mixture of the amidinate-stabilized silicon(I) dimer-rhodium complex [LSi{Rh(cod)-μ-Cl-Rh(cod)}SiL] (3) and the dimeric amidinate-stabilized rhodosilylene [(LSi)μ-{Rh(μ-Cl)2Rh(cod)}]2 (4). Moreover, the latter reacted with PPh3 to afford a mixture of the Wilkinson's catalyst [(PPh3)3RhCl] and the dimeric rhodosilylene complex [(LSi)μ-{RhCl(PPh3)}]2 (5), which underwent a rearrangement to form the rhodosilylene-phosphidorhodium dimer (LSi)[μ-{RhCl(PPh3)}μ-{RhCl(LSiPh)}](PPh2) (6). Compounds 2-6 were characterized by NMR spectroscopy and X-ray crystallography. In addition, DFT calculations of compound 4 were performed to understand its electronic structure.

The reaction of the amidinato silicon(I) dimer [LSi:] 2 (1, L = PhC(NtBu) 2 ) with FeBr 2 in THF at ambient temperature afforded the silicon(I)-iron(II) dimer [LSi(FeBr 2 •thf)] 2 (2) after 40 hours. Compound 2 can catalyse hydroboration of aliphatic and aromatic ketone compounds with HBpin in the absence of any strong reducing agent. Mechanistic studies show that complex 2 reacts with ketone compounds to form a zwitterionic intermediate in the first step of catalysis. Subsequent reaction with HBpin affords the corresponding boron esters and then regenerates complex 2.

The background of the Frontispiece graphic shows the hive at Nanyang Technological University, which was designed by Thomas Heatherwick. It aims to promote interaction among professors and students. This philosophy is also demonstrated in the Communication by M.‐D. Su, C.‐W. So et al. on page 14329 ff. The interaction between the low‐valent silicon and cobalt centers in the dimeric amidinato cobaltosilylene resulted in promoting the regio‐ and stereoselective addition of the ortho‐C−H bond in arylpyridines with the C≡C triple bonds in alkynes.

The synthesis of a dimeric base-stabilized cobaltosilylene complex and its catalytic reactions are described. Treatment of the amidinato silicon(I) dimer [LSi:] (1; L=PhC(NtBu) ) with CoBr in toluene for 10 days afforded the dimeric amidinato cobaltosilylene [(LSi)μ-{CoBr(LSiBr)}] (2), which is speculated to proceed via "LSiCoBr" and "LSiBr" intermediates in the reaction. Compound 2 is paramagnetic, with an effective magnetic moment of 2.8 μB. Its electronic structure was elucidated by single-crystal X-ray crystallography and DFT studies. It was capable of catalyzing C-H bond functionalization, in which a combination of 2, phosphine and MeMgI can regio- and stereoselectively promoted the addition of the C≡C triple bonds in alkynes to the ortho-C-H position in arylpyridines. In addition, compound 2 catalyzed Kumada-type coupling reactions between aryl chlorides and the Grignard reagent 2-mesitylmagnesium bromide.