Iridium(I) and Iridium(III) Complexes Supported by a Diphenolate Imidazolyl-Carbene Ligand

Deprotonation of 1,3-di(2-hydroxy-5-tert-butylphenyl)imidazolium chloride (1a) followed by reaction with chloro-1,5-cyclooctadiene Ir(I) dimer affords the anionic Ir(I) complex [K][{OCO}Ir(cod)] (2: OCO = 1,3-di(2-hydroxy-5-tert-butylphenyl)imidazolyl; cod = 1,5-cyclooctadiene), the first Ir complex stabilized by a diphenolate imidazolyl-carbene ligand. In the solid state 2 exhibits square-planar geometry, with only one of the phenoxides bound to the metal center. Oxidation of 2 with 2 equiv of [FeCp_2][PF_6] generates the Ir(III) complex [{OCO}Ir(cod)(MeCN)][PF_6] (3). Reaction of 3 with H_2 results in the liberation of cyclooctane and a species capable of catalyzing the hydrogenation of cyclohexene to cyclohexane. Displacement of cyclooctadiene from 3 can be achieved by heating in acetonitrile to form [{OCO}Ir(MeCN)3][PF_6] (4) or by reaction with either PMe_3 or PCy_3 to generate [{OCO}Ir(PMe_3)_3][PF_6] (5) or [{OCO}Ir(PCy_3)_2(MeCN)][PF_6] (6), respectively. 6 reacts with CO in acetonitrile to give an equilibrium mixture of 6 and [{OCO}Ir(PCy_3)_2(CO)][PF_6] (7) and with chloride to generate [{OCO}Ir(PCy_3)_(2)Cl] (8). The solid-state structure of 8 shows that the diphenolate imidazolyl-carbene ligand is distorted from planarity; DFT calculations suggest this is due to an antibonding interaction between the phenolates and the metal center in the highest occupied molecular orbital (HOMO) of the complex. 8 undergoes two successive reversible one-electron oxidations in CH_(2)Cl_2 at −0.22 and at 0.58 V (vs ferrocene/ferrocenium); EPR spectra, mass spectroscopy, and DFT calculations suggest that the product of the first oxidation is [{OCO}Ir(PCy_3)_(2)Cl]+ (8+), with the unpaired electron occupying a molecular orbital that is delocalized over both the metal center and the diphenolate imidazolyl-carbene ligand

cis-(Nitrato-κ2 O,O′)(2,5,5,7,9,12,12,14-octa­methyl-1,4,8,11-tetra­aza­cyclo­tetra­decane-κ4 N,N′,N′′,N′′′)cadmium nitrate hemihydrate

The CdII atom in the title complex, [Cd(NO3)(C18H40N4)]NO3·0.5H2O, is coordinated within a cis-N4O2 donor set provided by the tetra­dentate macrocyclic ligand and two O atoms of a nitrate anion; the coordination geometry is distorted octa­hedral. The lattice water mol­ecule is located on a twofold rotation axis. N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions link the complex cations into a supra­molecular layer in the bc plane. Layers are connected by O—H⋯O hydrogen bonds between the lattice water mol­ecule and the non-coordinating nitrate anion, as well as by weak C—H⋯O contacts

5,7,7,12,14,14-Hexamethyl-4,11-diaza-1,8-diazo­niacyclo­tetra­decane bis­(perchlorate) monohydrate

In the title hydrated salt, C16H38N4 2+·2ClO4 −·H2O, the dication is protonated at the diagonally opposite N atoms proximate to the –C(CH3)2– groups. Within the cavity, there are two ammonium–amine N—H⋯N hydrogen bonds. Supra­molecular layers are formed in the crystal packing whereby the water mol­ecule links two perchlorate anions, and the resultant aggregates are connected to the dications via N—H⋯O hydrogen bonds. Layers, with an undulating topology, stack along the a axis being connected by C—H⋯O inter­actions

A simple theory of the optimal number of immigrants

This paper develops a simple model to explain two stylised facts about immigration. First, some countries have a low ratio of migrants in their population, while other wealthy countries have a high number of migrants. In fact such migrants are of the same order of magnitude as their domestic workforce. Secondly, migrants are often segregated in jobs. The domestic residents do not wish to be employed in these jobs due to their unattractive working conditions and payments. The model assumes that domestic residents are all identical in terms of their skills and wealth and furthermore that native and foreign workers have the same skills. However, foreign migrants cannot be excluded from the use of public services, the quality of which decreases due to congestion created or enhanced by migrants. On the basis of our model we show that the stylised facts are consistent with an optimal immigration policy, defined by domestic residents who have neither altruistic feelings nor ethnic prejudice toward foreign migrants.Ce papier développe un modèle simple pour expliquer deux faits stylisés sur l'immigration. D'abord, certains pays ont une proportion d'immigrés dans la population relativement basse, alors que d'autres pays riches accueillent davantage d'immigrés. En fait dans certains pays la population active d'immigrés est du même ordre de grandeur que celle de nationaux. Ensuite, les immigrés sont souvent ségrégés dans certains emplois. Les nationaux ne souhaitent pas prendre ces emplois par suite de leurs rémunérations et conditions de travail peu attractives. Le modèle suppose que les nationaux sont tous identiques dans leurs compétences et dans leur richesse. De plus les travailleurs nationaux et étrangers ont les mêmes compétences. Cependant, les immigrés ne peuvent pas être exclus de l'usage de services publics dont la qualité diminue à cause de leur encombrement qui résulte ou qui est amplifié par la venue d'immigrés. Le modèle permet d'établir que les faits stylisés observés sont cohérents avec les résultats d'une politique optimale d'immigration, définie par des nationaux qui n'éprouvent ni sentiments altruistes ni préjudices ethniques à l'égard des immigrés venant de l'étranger

Tourism, jobs, capital accumulation and the economy: A dynamic analysis

This paper examines the effects of tourism on labor employment, capital accumulation and resident welfare for a small open economy with unemployment. A tourism boom improves the terms of trade, increases labor employment, but lowers capital accumulation. The reduction in the capital stock depends on the degree of factor intensity. When the traded sector is weakly capital intensive, the fall in capital would not be so severe and the expansion of tourism improves welfare. However, when the traded sector is strongly capital intensive, the fall in capital can be a dominant factor to lower welfare. This immiserizing result of tourism on resident welfare is confirmed by the German data.tourism ; employment ; capital accumulation ; welfare

Corruption and Zipf's law

Zipf's law states that the population size of a city is inversely proportional to its population rank of the city. This paper examines the applicability of the Zipf's law to the world rank of corruption. The relationship between corruption and its rank is found to be approximately log-linear but less than perfect for Zipf's law. Due to a slight concavity of the relation, either a piecewise regression or a non-linear model provides an extremely convenient tool for predicting the degree of corruption across countries. Although limited number of observations, an alternative characterization of the corruption ranks appears to obey the Zipf's law more closely

[(4E,11E)-5,7,12,14-Tetra­benzyl-7,14-dimethyl-1,4,8,11-tetra­aza­cyclo­tetra­deca-4,11-diene]copper(II) bis(per­chlorate)

The complete cation in the title compound, [Cu(C40H48N4)](ClO4)2, is generated by the operation of a crystallographic centre of inversion. The CuII ion exists in a tetra­gonally distorted trans-N4O2 coordination geometry defined by the four N atoms of the macrocyclic ligand and two weakly bound perchlorate-O atoms from two anions. The N—H atoms form intra­molecular N—H⋯O(perchlorate) hydrogen bonds. Disorder was resolved in the –CH2–NH– portion of the macrocycle with the major component having a site-occupancy factor of 0.570 (6)

Robotic Lepidoptery: Structural Characterization of (mostly) Unexpected Palladium Complexes Obtained from High-Throughput Catalyst Screening

In the course of a high-throughput search for optimal combinations of bidentate ligands with Pd(II) carboxylates to generate oxidation catalysts, we obtained and crystallographically characterized a number of crystalline products. While some combinations afforded the anticipated (L-L)Pd(OC(O)R)_2 structures (L-L = bipyridine, tmeda; R = CH_3, CF_3), many gave unusual oligometallic complexes resulting from reactions such as C−H activation (L-L = sparteine), P−C bond cleavage (L-L = 1,2-bis(diphenylphosphino)ethane, and C−C bond formation between solvent (acetone) and ligand (L-L = 1,4-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene). These findings illustrate potential pitfalls of screening procedures based on assuming uniform, in situ catalyst self-assembly

(Acetato-κO)(2,5,5,7,9,12,12,14-octa­methyl-1,4,8,11-tetra­aza­cyclo­tetra­decane-κ4 N,N′,N′′,N′′′)zinc perchlorate

The ZnII atom in the cation of the title salt, [Zn(C2H3O2)(C18H40N4)]ClO4, is five-coordinated by the four N atoms of the macrocycle and the O atom of the monodentate acetate ligand. The N4O donor set is based on a trigonal bipyramid with two N atoms occupying axial positions [N—Zn—N = 170.89 (16)°]. The perchlorate anions are associated with the cations via N—H⋯O hydrogen bonds; intra­molecular N—H⋯O(acetate) inter­actions are also observed. The neutral aggregates are connected into an helical chain along the b axis via N—H⋯O(acetate) hydrogen bonds. The perchlorate anion was found to be disordered about a pseudo-threefold axis: the major component of the disorder had a site occupancy factor of 0.692 (11)