Unexpected reactivities of Cu2(diphosphine)2 complexes in alcohol: isolation, x-ray crystal structure, and photoluminescent properties of a remarkably stable [Cu3(diphosphine)3(mu3-H)]2+ hydride complex

Treatment of [Cu2(dcpm)2]Y2 (dcpm = bis(dicyclohexylphosphino)methane, Y = ClO4-, BF4-, PF6-, CF3SO3-) with refluxing MeOH in the presence of KOH afforded hydride complexes [Cu3(dcpm)3(mu3-H)]Y2 (1) in about 85% yield. Refluxing [Cu2(dcpm)2](PF6)2 with MeOH in the presence of NH3.H2O and air gave a carboxylate complex [Cu2(dcpm)2(O2CCH2OH)]PF6 (2) in 40% yield. All of the complexes 1 and 2 have been characterized by X-ray crystallography. The Cu3 cores in 1 are almost perfectly shielded by the dcpm ligands. Intense photoluminescence was observed for 1 both in the solid state and in solution.     

Picosecond pulse transmission in germanium of various thicknesses

The transmission of ultrashort pulses from a mode-locked Nd: glass laser in germanium of various thicknesses (3 to 8 m) has been measured as a function of incident irradiance. Transmission is seen to increase with irradiance level in all samples. The degree of enhancement is greater for the thcker samples. At high excitation levels, thinner samples show a peaking of transmission, which does not occur in a thick sample. Taking the sample as composed of thin elements, the parameters characterizing the photoexcited electron-hole plasma have been found by assuming homogeneous excitation within each element. Theoretical curves thus obtained give good quantitative account of the experimental results. Peaking of transmission is seen to due to a balance between absorption enhancement in the front portion of the sample and absorption reduction in the back.     

Our Odyssey with Functionalized Chiral Phosphines: From Optical Resolution to Asymmetric Synthesis to Catalysis

Our journey in organophosphorus research over the past 26 years is compiled in this Personal Account. Advances in palladacycle design have engendered a shift in our focus from template‐mediated transformations to catalysis for the direct preparation of chiral phosphines containing a wide variety of functional groups. Novel approaches to access previously inaccessible phosphines and their applications in cancer research are summarized herein.

     

Efficient computation of the Bergsma–Dassios sign covariance

In an extension of Kendall’s \(\tau \), Bergsma and Dassios (Bernoulli 20(2):1006–1028, 2014) introduced a covariance measure \(\tau ^*\) for two ordinal random variables that vanishes if and only if the two variables are independent. For a sample of size n, a direct computation of \(t^*\), the empirical version of \(\tau ^*\), requires \(O(n^4)\) operations. We derive an algorithm that computes the statistic using only \(O \left( n^2\log (n)\right) \) operations.     

Axial donating ligands: a new strategy for late transition metal olefin polymerization catalysis

An alpha-diimine ligand (1) containing an axial donating pyridine group is developed for late metal polymerization catalysis. Despite having no substitution on the bottom face of the ligand, the nickel and palladium complexes of 1 are highly active for ethylene polymerization, producing linear high molecular weight polymers. For example, 1-NiBr2 (3) forms PE with a Mn of up to 109 224 g/mol with 1.4 branches/1000 C's. Similarly, 1-PdMeCl (5) forms PE with a Mn of up to 880 379 g/mol with 5.1 branches/1000 C's. In sharp contrast, catalysts containing the control ligand (2) consisting of a noncoordinating phenyl group gave only low molecular weight branched oligomers. It is observed that AlMe2Cl plays a specific role in generating the active species for the pyridine-based complexes. Presumably, the pyridine group may interact with AlMe2Cl to form a bimetallic species which suppresses the beta-hydride elimination process, hence resulting in reduced chain transfer and more linear structure.     

Ruthenium complexes with tetraphenylimidodiphosphinate: syntheses, structures, and applications to catalytic organic oxidation

Treatment of Ru(PPh3)3Cl2 with K(tpip) (tpip(-)=[N(Ph2PO)2](-)) afforded Ru(tpip)(PPh3)2Cl (1), which reacted with 4- t-Bu-C6H4CN, SO2(g), and NH 3(g) to give Ru(tpip)(PPh3)2Cl(4- t-BuC6H4CN) (2), Ru(tpip)(PPh3)2Cl(SO2) (3), and fac-[Ru(NH3)3(PPh3)2Cl][tpip] (4), respectively. Reaction of [Ru(CO)2Cl2] x with K(tpip) in refluxing tetrahydrofuran (THF) led to isolation of the K/Ru bimetallic compound K 2Ru2(tpip)4(CO)4Cl2 (5). Photolysis of cis-Ru(tpip) 2(NO)Cl in MeCN and wet CH 2Cl 2 afforded cis-Ru(tpip) 2(MeCN)Cl ( 6) and cis-Ru(tpip)2(H2O)Cl (7), respectively. Refluxing 6 in neat THF yielded Ru(tpip) 2(THF)Cl (8). Treatment of Ru(CHR)Cl2(PCy3)2 (Cy=cyclohexyl) with [Ag(tpip)] 4 afforded cis-Ru(tpip)2(CHR)(PCy3) [R=Ph (9), OEt (10)]. Complex 9 is capable of catalyzing oxidation of alcohols and olefins with N-methylmorpholine N-oxide and iodosylbenzene, respectively. The crystal structures of 2-7 and 9 were determined.     

On "the complete basis set limit" and plane-wave methods in first-principles simulations of water

Water structure, measured by the height of the first peak in oxygen-oxygen radial distributions, is converged with respect to plane-wave basis energy cutoffs for ab initio molecular dynamics simulations, confirming the reliability of plane-wave methods.