Tetrahedranyllithium: Synthesis, Characterization, and Reactivity

The first representative of stable tetrahedranyl anion, tris(trimethylsilyl)tetrahedranyllithium (3), has been synthesized by the reaction of tetrakis(trimethylsilyl)tetrahedrane (2) with methyllithium in tetrahydrofuran. The structural characterization of the tetrahedranyllithium has been achieved by X-ray crystallography, showing that the structure of 3·(TMEDA)1.5 represents a stretched tetrahedron. The endocyclic C(Li)−C(SiMe3) bond lengths range from 1.5408(15) to 1.5441(15) Å (av 1.5425(15) Å), and are longer than the endocyclic C(SiMe3)−C(SiMe3) bond lengths, which range from 1.4961(15) to 1.5009(15) Å (av 1.4986(15) Å). Methyl- and hydrogen-substituted tetrahedranes have also been prepared by the reaction of 3 with dimethyl sulfate and cyclopentadiene, respectively

Tetrahedranyllithium: Synthesis, Characterization, and Reactivity

The first representative of stable tetrahedranyl anion, tris(trimethylsilyl)tetrahedranyllithium (3), has been synthesized by the reaction of tetrakis(trimethylsilyl)tetrahedrane (2) with methyllithium in tetrahydrofuran. The structural characterization of the tetrahedranyllithium has been achieved by X-ray crystallography, showing that the structure of 3·(TMEDA)1.5 represents a stretched tetrahedron. The endocyclic C(Li)−C(SiMe3) bond lengths range from 1.5408(15) to 1.5441(15) Å (av 1.5425(15) Å), and are longer than the endocyclic C(SiMe3)−C(SiMe3) bond lengths, which range from 1.4961(15) to 1.5009(15) Å (av 1.4986(15) Å). Methyl- and hydrogen-substituted tetrahedranes have also been prepared by the reaction of 3 with dimethyl sulfate and cyclopentadiene, respectively

A Stable Silaborene: Synthesis and Characterization

A stable silicon−boron doubly bonded compound, silaborene (2), was synthesized by the reaction of 1,1-dilithiosilane (1) with dichloro(2,2,6,6-tetramethylpiperidino)borane in toluene. The X-ray crystallographic analysis of 2 revealed that the >SiB−N2 reacted with lithium trimethylsilylacetylide at 60 °C in DME to give the corresponding silaborenide (4-·[Li(dme)3]+), whose reddish-orange crystals were isolated as the solvent separated ion pair. The X-ray analysis of 4-·[Li(dme)3]+ showed that the Si−B bond length (1.933(3) Å) is longer than that of 2, but still shorter than typical Si−B single bonds. These structural features indicate that 4- has double bond character involving the >SiB- resonance structure

Group-14-Element-Based Hybrid Dendrimers. Synthesis and Characterization of Dendrimers with Alternating Si and Ge Atoms in the Chains

A hybrid dendrimer with alternating Si and Ge atoms in the chains has been synthesized by the divergent growth method using Me(PhMe2Ge)2SiLi as a branching reagent. The structure of the first generation of the hybrid permethylated dendrimer 1G has been established by X-ray crystallography

A Stable Silaborene: Synthesis and Characterization

A stable silicon−boron doubly bonded compound, silaborene (2), was synthesized by the reaction of 1,1-dilithiosilane (1) with dichloro(2,2,6,6-tetramethylpiperidino)borane in toluene. The X-ray crystallographic analysis of 2 revealed that the >SiB−N2 reacted with lithium trimethylsilylacetylide at 60 °C in DME to give the corresponding silaborenide (4-·[Li(dme)3]+), whose reddish-orange crystals were isolated as the solvent separated ion pair. The X-ray analysis of 4-·[Li(dme)3]+ showed that the Si−B bond length (1.933(3) Å) is longer than that of 2, but still shorter than typical Si−B single bonds. These structural features indicate that 4- has double bond character involving the >SiB- resonance structure

A Stable Silaborene: Synthesis and Characterization

A stable silicon−boron doubly bonded compound, silaborene (2), was synthesized by the reaction of 1,1-dilithiosilane (1) with dichloro(2,2,6,6-tetramethylpiperidino)borane in toluene. The X-ray crystallographic analysis of 2 revealed that the >SiB−N2 reacted with lithium trimethylsilylacetylide at 60 °C in DME to give the corresponding silaborenide (4-·[Li(dme)3]+), whose reddish-orange crystals were isolated as the solvent separated ion pair. The X-ray analysis of 4-·[Li(dme)3]+ showed that the Si−B bond length (1.933(3) Å) is longer than that of 2, but still shorter than typical Si−B single bonds. These structural features indicate that 4- has double bond character involving the >SiB- resonance structure

Unusual Reactivity of a Disilyne with 4-Dimethylaminopyridine: Formation of an Intramolecularly N-Coordinated Silylene and Its Isomerization to a Zwitterionic Silyl Anion

Reaction of isolable 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne (1) with an equiv amount of 4-dimethylaminopyridine unexpectedly produced the intramolecularly N-coordinated silylene 2 as the primary product. However, 2 was not thermally stable at room temperature in solution and slowly isomerized to silyl anion 3 with a zwitterionic structure via 1,2-hydrogen migration followed by Si–N bond formation

Unusual Reactivity of a Disilyne with 4-Dimethylaminopyridine: Formation of an Intramolecularly N-Coordinated Silylene and Its Isomerization to a Zwitterionic Silyl Anion

Reaction of isolable 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne (1) with an equiv amount of 4-dimethylaminopyridine unexpectedly produced the intramolecularly N-coordinated silylene 2 as the primary product. However, 2 was not thermally stable at room temperature in solution and slowly isomerized to silyl anion 3 with a zwitterionic structure via 1,2-hydrogen migration followed by Si–N bond formation

An <i>N</i>-Heterocyclic Carbene−Disilyne Complex and Its Reactivity toward ZnCl₂

The reaction of disilyne 1 with 1,3,4,5-tetramethylimidazol-2-ylidene (an N-heterocyclic carbene, NHC) produced the disilyne−NHC complex 2, RLSiSiR: (R = SiiPr[CH(SiMe3)2]2, L = NHC), with a trans geometry of the SiSi moiety and lone-pair electrons residing on one of the double-bonded Si atoms. Upon complexation of 2 with ZnCl2, the disilyne−NHC−ZnCl2 complex 3 was produced, in which the SiSi bond adopted the cis geometry

Aromaticity of the Cyclobutadiene Dianion: Structural Characteristics and Magnetic Properties

The dilithium salts of cyclobutadiene dianions (CBD2-), 1,2-diphenyl-3,4-bis(trimethylsilyl)cyclobutadiene dianion dilithium (3), and 1,3-diphenyl-2,4-bis(trimethylsilyl)cyclobutadiene dianion dilithium (4) have been synthesized by the reaction of the corresponding cyclobutadiene cobalt complexes with lithium metal in tetrahydrofuran (THF). The dilithium salts were isolated as air- and moisture-sensitive crystals, and their molecular structures, containing two molecules of 1,2-dimethoxyethane (DME), were determined by X-ray crystallography. Each of the CBD2- has a monomeric structure and forms contact ion pairs (CIPs) in the crystal. The two Li+ ions are located above and below the plane of the four-membered ring and are bonded to the four quaternary carbon atoms. The cyclobutadienediide ring of the cis-diphenyl CBD2- (3) shows a conspicuous trapezoid structure, whereas that of the trans-diphenyl CBD2- (4) shows a slightly rhomboid structure. The 7Li NMR spectra of the CBD2- indicate that the two lithium atoms are considerably shielded by a diatropic ring current, resulting from the six-π-electron system