We have used high-resolution X-ray photoelectron spectroscopy (XPS) to investigate the molecular dependence on sulfur chemical states of organosulfur monolayers of alkanethiol, dialkyl disulfide, monosulfide, thiophene, and aromatic thiols on a Au(111) surface. When monosulfides or thiophenes adsorbed on the Au surface, the S(2p) peaks appeared between 161 and 164 eV, and peak fitting revealed that these organosulfurs exhibited almost the same peaks as those of alkanethiol and dialklyl disulfide monolayers. The monolayer made from monosulfide with shorter alkyl chains exhibited almost the same S(2p) XPS spectrum as the typical alkanethiol or dialkyl disulfide monolayers. Another S(2p3/2) peak appeared for aromatic derivatized thiol SAMs at around 161 eV, in addition to strong doublet S(2p) peak observed at 162.0 and 163.3 eV in the S(2p) spectra. The 161 eV peak was observed even in the S(2p) XPS spectra of alkanethiol or dialkyl disulfide monolayers, at the initial stage of monolayer growth or after low-temperature (∼ 100 °C) annealing of low molecular density alkanethiol SAMs. We consider that this 161 eV peak can be formed without molecular decomposition as well as due to the atomic sulfur produced by C-S cleavage.

We have studied electrical conduction of conjugated molecules with phenyl rings embedded into alkanethiol self-assembled monolayers (SAMs), to investigate the molecular structural effect on the electrical conduction. Scanning tunneling microscope (STM) images of this surface revealed that the conjugated molecules with phenyl rings adsorbed mainly on defects and domain boundaries of the pre-assembled alkanethiol (nonanethiol C9) SAM and formed conjugated domains. In the case of conjugated molecules with one or three methylene groups between the sulfur and phenyl rings, the measured height of the conjugated molecular domains depended on their lateral sizes, while a strong dependence was not observed in the case of conjugated molecules without a methylene group. By analyzing size dependence on the height of the conjugated molecular domain, we could evaluate the electronic conductivity of the molecular domains. As a result of the analysis, to increase the vertical conduction of the molecular domains, one methylene group was found to be necessary between the sulfur and aromatic phenyl rings. Local barrier heights on the conjugated molecular domains in all the cases were larger than on the C9 SAM surface, suggesting that the increase in the vertical conductivitity is not likely to be due to the lowering of the local barrier height, but can be attributed to the conjugated molecular adsorption. X-ray photoelectron spectra (XPS) and ultraviolet light photoelectron spectra (UPS) revealed that the carrier density among conjugated molecular SAMs does not depend on the number of methylene groups between the sulfur and phenyl rings, suggesting that the higher vertical conduction of conjugated molecules with one methylene group can probably be attributed to higher transfer probability of carriers during the STM measurements.

Electric conductivity of organic molecules was estimated with molecular resolution using self-assembled techniques and scanning tunneling microscopy (STM). Conjugated molecules of [1,1‘:4‘,1‘ ‘-terphenyl]-4-methanethiol (TP) were embedded in self-assembled monolayers of insulative n-alkanethiols, and when observed by STM, TP molecules appeared as protruding domains. The apparent height of the TP domains increases as the lateral size of the domains grows from 1 to 10 nm, reflecting the increase in the vertical conductance of the domains due to the lateral, intermolecular interaction. We assumed that the molecules are connected to each other with resistors for estimating the effect of intermolecular interaction on the conductance and calculated the height of conducting disks with various radii, which should roughly reproduce the size-dependent height of the TP domains observed by STM. The estimated resistance of the single TP molecule was less than 40 GΩ, and the effective lateral conductivity corresponding to the large TP domains was larger than 0.01 S/cm.

Oxidative addition of Ph2P(O)H to M(PEt3)3 (M = Pd, Pt) readily took place at room temperature in benzene to afford cis-MH[P(O)Ph2][PPh2(OH)](PEt3) complexes. The structure of the platinum complex was determined by X-ray crystallography. The palladium complex was found to undergo an insertion reaction with oct-1-yne to give 1- and 2-(diphenylphosphinyl)oct-1-enes. Pd(PPh3)4 catalyzed regio- and stereoselective synthesis of alkenyldiphenylphosphine oxides (hydrophosphinylation) from alkynes and Ph2P(O)H.

Highly regio- and stereoselective borylstannylative carbocyclization of diynes 2a − f with the borylstannane 1 are efficiently catalyzed at room temperature by a series of palladium complexes such as Cl2Pd(PPh3)2, Cl2Pd[P(o-tolyl)3]2, Pd(PPh3)4, and Pd(dba)2, giving 1-(borylmethylidene)-2-(stannylmethylidene)cycloalkane derivatives 3a − f in high yields. A 1,6-enyne (2g) also reacts similarly to afford a high yield of the corresponding cyclized product 3g.