Tomoaki Tanase

Systematic Conversion of Single Walled Carbon Nanotubes into n-type Thermoelectric Materials by Molecular Dopants

Thermoelectrics is a challenging issue for modern and future energy conversion and recovery technology. Carbon nanotubes are promising active thermoelectic materials owing to their narrow bandgap energy and high charge carrier mobility, and they can be integrated into flexible thermoelectrics that can recover any waste heat. We here report air-stable n-type single walled carbon nanotubes with a variety of weak electron donors in the range of HOMO level between ca. −4.4 eV and ca. −5.6 eV, in which partial uphill electron injection from the dopant to the conduction band of single walled carbon nanotubes is dominant. We display flexible films of the doped single walled carbon nanotubes possessing significantly large thermoelectric effect, which is applicable to flexible ambient thermoelectric modules.

Hexa‐ and Octagold Chains from Flexible Tetragold Molecular Units Supported by Linear Tetraphosphine Ligands

A flexible building block: Flexible tetragold(I) chain complexes supported by a new single methylene-bridged tetraphosphine ligand were synthesized and further transformed into discrete linear octagold(I) {Au(8)} and cyclic hexagold(I) {Au(6)} structures by reaction with KI and NaAuCl(4), respectively (see picture, Au purple, Cl dark green, PF(6) light green, I pink). The tetragold complexes are also luminescent at room temperature.

Unprecedented sugar-dependent in vivo antitumor activity of carbohydrate-pendant cis-diamminedichloroplatinum(II) complexes.

Eight carbohydrate-pendant platinum(II) complexes have been synthesized from carbohydrate-diamine conjugates. D-Glucose, D-mannose, D-galactose, D-xylose, and L-glucose are attached to the dichloroplatinum(II) moiety by 1,3- or 1,2-diaminopropane chelates through with an O-glycoside bond. All the carbohydrate moieties reduced the toxicity inherent with platinum(II) complexes.

Planar Tetranuclear and Dumbbell-Shaped Octanuclear Palladium Complexes with Bridging Silylene Ligands†

Late-transition-metal complexes with silylene (SiR2) ligands have attracted considerable attention since the proposal of platinum–silylene intermediates in the [PtCl2(PEt3)2]-catalyzed reactions that convert organodisilanes into oligosilanes and the cyclic adducts into alkynes. Mononuclear silylene complexes of platinum and other late transition metals were not isolated until some years later, probably because of the extremely high reactivity of most M=Si double bonds. Dinuclear complexes of late transition metals with bridging silylene ligands are more common. The dinuclear platinum complex [{Pt(PR3)}2(m-SiHPh2)2] (PR3 = PPh3, PCy3 etc.) has been reported. However, in spite of the stable coordination of bridging silylene ligands, complexes containing three or more metal atoms with bridging Si ligands have few precedents, and those known are stabilized by electron-withdrawing CO and CNR ligands. Braddock-Wilking and coworkers and our group have reported zero-valent triangular Pt3 complexes, stabilized by bridging silylene and phosphine ligands. Chen, Shimada, and Tanaka employed 1,2disilabenzene as a ligand and prepared trinuclear Pd complexes supported by the Si ligands. Herein, we report the synthesis and unexpected structure of a planar tetranuclear Pd complex with three bridging SiPh2 ligands as well as facile exchange of the bridging silylene ligands to yield a dumbbell-shaped octapalladium complex composed of two Pd4 units bridged by a diphosphine ligand. These complexes, composed of Pd centers and electrondonating Si and phosphine ligands, possess a unique planar {Pd4Si3} core. Heating a mixture of a dipalladium complex with bridging diphenylsilyl ligands, [{Pd(PCy3)}2(m-h -SiHPh2)2] (1), [12] and 1,2-bis(dimethylphosphino)ethane (dmpe) in toluene at 80 8C produced [Pd{Pd(dmpe)}3(m -SiPh2)3] (2 ; 54 %), which incorporates four Pd centers and three bridging SiPh2 ligands [Eq. (1)]. The accompanying formation of [Pd(SiPh2H)2(dmpe)] (3) was also detected. Reaction of [Pd(PCy3)2] with 3 yields 2 as one of the products.

Studies on interactions of isocyanide with transition metal complexes: XXXVI. Spontaneous successive insertion of isocyanide into palladium-carbon σ-bond

Abstract Reaction of trans -Pd(PPh 3 ) 2 I(CH 3 ) ( 1a ) with 2,6-xylyl isocyanide in a 1:1 molar ratio led to a spontaneous insertion of isocyanides into a PdC bond to give the tris-imino insertion product 2a . The structure was determined by an X-ray analysis. The crystals are triclinic with space group P 1 ( a = 14.638(9), b = 15.662(7), c = 7.895(3) A, α = 85.06(6), β = 82.84(4), γ = 102.4(4)°, and Z = 2; R = 0.066 for 2076 independent reflections with F 0 > 5σ( F 0 ). The tris-imino group acts as a bidentate ligand through C- and N-coordinations. The 2-methyl-1-naphthyl complex, trans -Pd(PPh 3 )Br(2-CH 3 C 10 H 9 ) reacted with 2,6-xylyl isocyanide to give a bis-imino complex containing μ 2 -Br bridging ligands. Using p -nitirophenyl isocyanide, the reaction produced a mono-imino compound. Reaction of 2a with CuCl 2 gave a mixed metal complex, in which the copper(II) atom is coordinated to two neighbouring imino-nitrogens.

Facile Insertion of Carbon Dioxide into Cu2(μ-H) Dinuclear Units Supported by Tetraphosphine Ligands

Reactions of meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm) with Cu(I) species in the presence of NaBH4 afforded di- and tetranuclear copper hydride complexes, [Cu2(μ-H)(μ-dpmppm)2]X (1) and [Cu4(μ-H)2(μ4-H)(μ-dpmppm)2]X (2) (X=BF4, PF6). Complex 1 undergoes facile insertion of CO2 (1 atm) at room temperature, leading to a formate-bridged dicopper complex [Cu2(μ-HCOO)(dpmppm)2]X (3). The experimental and DFT theoretical studies clearly demonstrate that CO2 insertion into the Cu2(μ-H) unit occurred with the flexible dicopper platform. Complex 2 also undergoes CO2 insertion to give a formate-bridged complex, [Cu4(μ-HCOO)3(dpmppm)2]X, during which the square Cu4 framework opened up to a linear tetranuclear chain.

Tetrapalladium complex with bridging germylene ligands. Structural change of the planar Pd4Ge3 core.

A complex with a planar hexagonal Pd(4)Ge(3) core, [Pd{Pd(dmpe)}(3)(μ(3)-GePh(2))(3)], was synthesized and characterized by X-ray and NMR measurements as well as by DFT calculations. 4-tert-Butylbenzenethiol converted the Pd(4) complex into a hexapalladium complex, [{Pd(3)(μ-GePh(2))(2)(μ-H)(μ(3)-GePh(2)(SC(6)H(4)(t)Bu-4))}(2)(μ-dmpe)], composed of two Pd(3)Ge(3) units bridged by a dmpe ligand. The addition of CuI or AgI to the Pd(4) complex yielded [Pd(μ-MI){Pd(dmpe)}(3)(μ(3)-GePh(2))(3) ] (M = Cu, Ag), in which Cu or Ag bridges a Pd-Pd bond of the Pd(4)Ge(3) core. The CuI adducts in solution undergo a pivot motion of the CuI on the surface of the Pd(4)Ge(3) plane on the NMR time scale.

Preparation of 1,1′-bis[(diphenylphosphino)methyl]ferrocene and its transition-metal complexes

1,1′-Bis[(diphenylphosphino)methyl]ferrocene (dpmf). prepared from 1,1′-bis(chloromethyl)ferrocene and LiPPh2, reacted with [PdCl2(MeCN)2] to give [Pd2Cl2(dpmf )2]1, and treatment of 1 with [Pd3(2,6-Me2C6H3NC)6] in a 1 : 0.66 ratio in the presence of NH4PF6 and 2,6-Me2C6H3NC produced a macrocyclic complex [Pd4(2,6-Me2C6H3NC)8(dpmf )2]4+.

Self‐Alignment of Low‐Valent Octanuclear Palladium Atoms

A linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm) was used to synthesize linear octapalladium-extended metal atom chains as discrete molecules of [Pd8(μ-dpmppm)4](BF4)4 (1) and [Pd8(μ-dpmppm)4L2](BF4)4 (L=2,6-xylyl isocyanide (XylNC; 2), acetonitrile (3), and N,N-dimethylformamide (dmf; 4)), which are stable in the solution states and show interesting temperature-dependent photochemical properties in the near IR region. Variable temperature NMR studies demonstrated that at higher temperature T≈140 °C the Pd8 chains were dissociated into Pd4 fragments, which were thermodynamically self-aligned to restore the Pd8 chains at lower temperature T<60 °C. The coldspray ionization mass spectra suggested a possibility for further aggregation of the linear tetrapalladium units.

Wheel-Shaped Icosanuclear Homo- and Heterometallic Complexes of NiII, CoII, and CuII Ions Supported by Unsymmetrical Aminoalcohol Ligands

Reactions of M(OAc)2·4H2O (M = Ni, Co) with 3-[benzyl(2-hydroxyethyl)amino]-1-propanol (H2L) in the presence of pyridine or triethylamine afforded novel homometallic icosanuclear wheel-shaped complexes [M20L4(HL)4(OAc)28] (M = Ni (1), Co (2)), which consist of a central M(II)12 single-stranded, nearly planar loop with four peripheral [M2(HL)(OAc)2] fragments attached in an S4 symmetrical fashion. The complexes can alternatively be recognized as saddle-shaped wheel structures, in which four tetranuclear units of [M4L(HL)(OAc)7](2-) are connected by four M(2+) ions (M5). The tetranuclear unit itself can be derived from an ideal C2 symmetrical [M4(HL)2(μ-η(2)-OAc)4(μ-η(1),η(1)-OAc)2(η(1),η(1)-OAc)](-) structure through deprotonation of the HL(-) ligand, and is composed of two plane-shared M3O4 incomplete cubanes in which the M2 and M3 atoms are involved in the central fused plane and the M1 and M4 atoms are disposed at the apex sites. Mixed-metal icosanuclear complexes [NixM20-xL4(HL)4(OAc)28] (3, M = Co, x = 9.5) and [Ni12M8L4(HL)4(OAc)28] (4, M = Cu) were also synthesized by using equimolar amounts of Ni(II) and M(II) ions, and were shown to have similar structures to 1 and 2. X-ray crystallographic and fluorescent analyses revealed that complex 3 contains nonstoichiometric amounts of Ni(2+) and Co(2+) ions in the ratio of 9.5:10.5 and that these are disordered at every metal site. In striking contrast, complex 4 has a stoichiometric formula of Ni12Cu8, which was confirmed by the Jahn-Teller elongation of Cu(2+) ions, and consequently, the M2 and M5 positions are occupied exclusively by the Cu(2+) ions. The temperature-dependent direct current (dc) magnetic susceptibility data showed the presence of ferromagnetic exchange interactions in the Ni homometallic (1) and NiCu bimetallic (4) complexes, while the Co homometallic (2) and NiCo bimetallic (3) complexes exhibited antiferromagnetic interactions due to spin-orbit coupling effects of the octahedral Co(II) ions. The present results demonstrate that the unsymmetrical aminoalcohol ligand H2L is quite effective in organizing the homo- and heterometallic icosanuclear wheel-shaped metal arrangements.