Tetrylene-Functionalized Si-Siliconoids.

The core expansion of metallic or metalloid clusters by the addition of further homo- or heteronuclear vertices is pivotal to the nucleation and growth of particles. The exohedral grafting of a low-valent functionality followed by endohedral incorporation have been identified as key steps. Following previous work on the Si series, we now report the synthesis and full characterization of the amidinatotetrylene-functionalized seven-vertex siliconoids SiR[E(NBu)CPh] (E = Si, Ge, Sn).

Stable Silapyramidanes.

Starting from tetrakis(trimethylsilyl)cyclobutadiene and an amidinate-supported silylene of the Roesky-type, a sequence of addition and reduction cleanly gives the elusive silapyramidane via an isolable cyclobutene intermediate with an exocyclic Si═C bond. The silapyramidane features an unusually shielded Si NMR resonance at -448.3 ppm for the apex silicon atom.

Low-Valent M Al Cluster Salts with Tetrahedral [SiAl ] and Trigonal-Bipyramidal [M Al ] Cores (M=Si/Ge).

Schnöckel's [(AlCp*) ] and Jutzi's [SiCp*][B(C F ) ] (Cp*=C Me ) are landmarks in modern main-group chemistry with diverse applications in synthesis and catalysis. Despite the isoelectronic relationship between the AlCp* and the [SiCp*] fragments, their mutual reactivity is hitherto unknown. Here, we report on their reaction giving the complex salts [Cp*Si(AlCp*) ][WCA] ([WCA] =[Al(OR ) ] and [F{Al(OR ) } ] ; R =C(CF ) ).

A Striking Mode of Activation of Carbon Disulfide with a Cooperative Bis(silylene).

The reactivity of the 1,4-substituted bis(silylenyl)terphenylene 1, 1,4-[ortho-(LSi)C H ] C H , (L=RC(NtBu) , R=Ph, Mes) towards CS is reported. It results in a dearomatization of the phenylene ring, affording the 1,3-substituted cyclohexadiene derivative 2. According to DFT calculations, a transient silene containing a Si=C bond capable of π(C=C) addition at the aromatic phenylene ring is a key intermediate.

Exohedral functionalization core expansion of siliconoids with Group 9 metals: catalytic activity in alkene isomerization.

Taking advantage of pendant tetrylene side-arms, stable unsaturated Si silicon clusters (siliconoids) with the benzpolarene motif (the energetic counterpart of benzene in silicon chemistry) are successfully employed as ligands towards Group 9 metals. The pronounced σ-donating properties of the tetrylene moieties allow for sequential oxidative addition and reductive elimination events without complete dissociation of the ligand at any stage. In this manner, either covalently linked or core-expanded metallasiliconoids are obtained.

Indirect and Direct Grafting of Transition Metals to Siliconoids.

Unsaturated charge-neutral silicon clusters (siliconoids) are important as gas-phase intermediates between molecules and the elemental bulk. With stable zirconocene- and hafnocene-substituted derivatives, we here report the first examples containing directly bonded transition-metal fragments that are readily accessible from the ligato-lithiated Si siliconoid (1Li) and Cp MCl (M=Zr, Hf). Charge-neutral siliconoid ligands with pending tetrylene functionality were prepared by the reaction of amidinato chloro tetrylenes [PhC(NtBu) ]ECl (E=Si, Ge, Sn) with 1Li, thus confirming the principal compatibility of such low-valent functionalities with the unsaturated Si cluster scaffold.