Hiromi Tobita

A layered ionic crystal of polar Li@C 60 superatoms

If the physical properties of C(60) fullerene molecules can be controlled in C(60) products already in use in various applications, the potential for industrial development will be significant. Encapsulation of a metal atom in the C(60) fullerene molecule is a promising way to control its physical properties. However, the isolation of C(60)-based metallofullerenes has been difficult due to their insolubility. Here, we report the complete isolation and determination of the molecular and crystal structure of polar cationic Li@C(60) metallofullerene. The physical and chemical properties of Li@C(60) cation are compared with those of pristine C(60). It is found that the lithium cation is located at off-centre positions in the C(60)-I(h) cage interior and that the [Li(+)@C(60)] salt has a unique two-dimensional structure. The present method of purification and crystallization of C(60)-based metallofullerenes provides a new C(60) fullerene material that contains a metal atom.

Rock‐Salt‐Type Crystal of Thermally Contracted C60 with Encapsulated Lithium Cation

Rock solid: fullerene-encapsulated Li(+) (Li(+)@C(60)) is an alkaline cation owing to the spherical shape and positive charge. Li(+)@C(60) crystallizes as a rock-salt-type crystal in the presence of PF(6)(-). The orientations of C(60) and PF(6)(-) (orange) are perfectly ordered below 370 K, and Li(+) (purple) hops within the cage. At temperatures below 100 K two Li(+) units are localized at two polar positions within each C(60) .

Covalently chemical modification of lithium ion-encapsulated fullerene: synthesis and characterization of [Li+@PCBM]PF6(-).

Covalently organic derivatization of [Li(+)@C60]PF6(-) to obtain Li(+)-encapsulated PCBM, [Li(+)@PCBM]PF6(-), is described. Synthetic procedures, electrochemical properties, light absorption properties, details of isomerization from [5,6]- to [6,6]-isomer, and X-ray crystal structure of [Li(+)@PCBM]PF6(-) are discussed.

Preparation of endohedral fullerene containing lithium (Li@C60) and isolation as pure hexafluorophosphate salt ([Li+@C60][PF6−])

A synthetic protocol for endohedral fullerene containing lithium (Li@C60), as well as the synthesis, characterization, and properties of its chemically oxidized derivative [Li+@C60][PF6−] are reported in full. Simultaneous deposition of Li plasma and C60 produces a mixture containing Li@C60 and C60. Strong intermolecular attraction between Li@C60 and C60 has prevented their separation, but this obstacle was surmounted by selective chemical oxidation of Li@C60, which led to the isolation of a substantial amount of pure [Li+@C60][PF6−]. For this purpose, an HPLC technique using an electrolyte in the mobile phase was effective in purifying the ionic metallofullerene. [Li+@C60][PF6−] was stable in air and, compared with [Li+@C60][SbCl6−], was more stable to moisture and various chemicals. [Li+@C60][PF6−] holds promise for practical applications. The spectroscopic data (MS, 7Li and 13C NMR, UV-vis, and IR) and electrochemical data for [Li+@C60][PF6−] are disclosed. In addition, the high electron affinity of [Li+@C60][PF6−] is discussed.

Synthesis and reactivity of (phosphinoaklyl)silyl complexes

Abstract Silyl ancillary ligands are expected to generate the reactive unsaturated metal center due to their exceptionally strong trans -influence and -effect. Nevertheless, little has been known on the influence of silyl ligands on the reactivity of transition-metal complexes. This would be mainly due to the facile cleavage of the metal–silicon bond. (Phosphinoalkyl)silyl ligands have been developed to suppress the elimination of silyl groups from the metal center. This article reviews the synthesis and properties of the transition metal complexes having chelate-type (phosphinoalkyl)silyl ligands R 2 P(CH 2 ) n SiR 2 ( n =1, 2).

Photoreactions of silyliron(II) complexes Cp*Fe(CO)2SiMe3 (Cp*=η5-C5H5, η5-C5Me5) in the presence of trihydrosilanes

Abstract The photochemistry of silyliron(II) complexes Cp★Fe(CO)2SiMe3 (Cp★  η5-C5H5, η5-C5Me5) in the presence of trihydrosilanes is described. Three types of products were observed, depending on the bulkiness of the Cp★ ligands and the substituents on the trihydrosilanes: (η5-C5H5)Fe(CO)2SiMe3 reacts with tert-alkylsilanes RSiH3 (R  tBu, C(Me2)2H) upon irradiation to give silylene-bridged diiron complexes (η5-C5H5)2Fe2(CO)3(μ-SiHR) in good yields. In contrast, (η5-C5Me5)Fe(CO)2SiMe3 reacts with the tert-alkylsilanes photochemically to give silyl monoiron complexes (η5-C5Me5)Fe(CO)2SiH2R exclusively. Using p-TolSiH3 instead of tert-alkylsilane, the main photolysis product was the hydridobis(silyl)iron complex Cp★Fe(CO)SiMe3(H)SiH2-p-Tol. The X-ray crystal structure analysis of (η5-C5H5)2Fe2(CO)3(μ-SiHtBu) revealed that this complex adopts a geometry in which the two Cp rings and a SiH bond are located on the same side with respect to the SiFe2C four-membered ring. 29Si NMR spectra of the silylene-bridged diiron complexes showed signals at remarkably low field (δ 235.5–289.1 ppm). A mechanism for the formation of these silylene-bridged diiron complexes is proposed.

Insertion of a Cationic Metallogermylene into E–H Bonds (E = H, B, Si)

A cationic germylene containing tungsten and N-heterocyclic carbene units reacted with H2 in fluorobenzene at 60 °C, resulting in its insertion into the H-H bond. It also activated the Si-H bond of ethyldimethylsilane and the B-H bond of pinacolborane at ambient temperature to give the insertion products. The latter insertion reactions against hydrosilane and hydroborane were found to be reversible.

Tetrakis(trimethylsilyl)ethylene and related compounds, crowded olefins☆

Abstract Tetrakis(trimethylsilyl)ethylene (1), tris(trimethylsilyl) (dimethylsilyl)ethylene and 1,2-bis(trimethylsilyl)-1,2-bis(dimethylsilyl)ethylene have been prepared and spectral properties are described. ESR spectra of anion and cation radicals of 1 are also recorded, indicating a nonplanar twisted structure for 1. These crowded olefins show interesting reversible thermochromism.

Reactions of a hydrido(hydrosilylene)ruthenium complex with carbonyl compounds

Reactions of a neutral silyleneruthenium complex with ketones and aldehydes, and isolation of their agostic intermediates are reported, where an alpha-H abstraction or hydrosilylation of the carbonyl compounds occurs depending on the substituents of the substrates.

Formation of a Germylyne Complex: Dehydrogenation of a Hydrido(hydrogermylene)tungsten Complex with Mesityl Isocyanate

The heavier analogues of transition-metal carbyne complexes are attractive synthetic targets for research in fundamental organometallic and main-group chemistry. Over the last 15 years, the syntheses of a series of complexes with M E bonds (E = Si, Ge, Sn, Pb) have been achieved, but examples are few. These complexes were synthesized by employing a base-stabilized halosilylene and stable divalent Group 14 element halides for E = Ge, Sn, or Pb as precursors. For example, Power and Simons reported the first example of this type of complex, [Cp(CO)2Mo Ge(C6H3-2,6-Mes2)] (Mes = mesityl = 2,4,6-trimethylphenyl), which was obtained by salt elimination from a germanium(II) chloride GeCl(C6H3-2,6Mes2) and an anionic complex Na[MoCp(CO)3]. [2a] Recently, we have synthesized a neutral hydrido (hydrogermylene) complex [Cp*(CO)2(H)W=Ge(H){C(SiMe3)3}] (1) and found that 1 reacted with mesitylisocyanate MesNCO upon heating to produce a germylyne complex [Cp*(CO)2W Ge{C(SiMe3)3}] (2) with release of MesNHCHO. In this reaction, 1 is formally dehydrogenated with MesNCO to give 2. This type of synthesis of a germylyne complex from a germylene complex has not been previously reported. We also succeeded in the isolation of an intermediate [Cp*(CO)2W(GeH(OCH=NMes){C(SiMe3)3})] (3). Herein, we report the details of this novel transformation and our mechanistic investigations, including kinetic studies with 3 and DFT calculations. We previously reported that 1 underwent hydrogermylation of PhNCO at the C=O bond at room temperature in 24 h to give a five-membered ring complex [Cp*(CO)2W(GeH(OCH=NPh){C(SiMe3)3})] (4) in 61% yield (85% NMR yield). A similar reaction of 1 with sterically hindered MesNCO (3 equiv) proceeded very slowly at room temperature to give the analogous complex 3 in 76 % yield after 10 days, together with germylyne complex 2 (24%) as determined from the H NMR spectrum (Scheme 1). Complex 3 was isolated in 61 % yield from a similar reaction using one