Cooperation between cis and trans influences in cisPt(II)PPh3)2 complexes: structural, spectroscopic and computational studies

The relevance of cis and trans influences of some anionic ligands X and Y in cis-[PtX2(PPh3)2] and cis-[PtXY(PPh3)2] complexes have been studied by the X-ray crystal structures of several derivatives (X2 = (AcO)2 (3), (NO3)2 (5), Br2 (7), I2 (11); and XY = Cl(AcO) (2), Cl(NO3) (4), and Cl(NO2) (13)), density functional theory (DFT) calculations, and one bond Pt-P coupling constants, 1JPtP. The latter have allowed an evaluation of the relative magnitude of both influences. It is concluded that such influences act in a cooperative way and that the cis influence is not irrelevant when rationalizing the 1JPtP values, as well as the experimental Pt-P bond distances. On the contrary, in the optimized geometries, evaluated through B3LYP/def2-SVP calculations, the cis influence was not observed, except for compounds ClPh (21), Ph2 (22), and, to a lesser extent, Cl(NO2) (13) and (NO2)2 (14). A natural bond order analysis on the optimized structures, however, has shown how the cis influence can be related to the s-character of the Pt hybrid orbital involved in the Pt-P bonds and the net atomic charge on Pt. We have also found that in the X-ray structures of cis-[PtX2(PPh3)2] complexes the two Pt-X and the two Pt-P bond lengths are different each other and are related to the conformation of the phosphine groups, rather than to the crystal packing, since this feature is observed also in the optimized geometries

Numerical Modelling of the Assembly of Big Bags to Optimize Landfill Disposal

The so-called ‘big bags’ are used in landfills to dispose waste material in a sequential manner. In this study, big bags are constituted by geosynthetics and filled with organic waste similar to granular material. The result is an element having a blocky shape and being highly deformable. The process of deployment of big bags for waste disposal in landfills becomes crucial when considering the stability of these assemblies. This paper is intended to focus on the understanding of the mechanisms governing the stability of these assemblies of blocks by means of Distinct Element numerical modelling. To determine the appropriate properties to be assigned to the model, a calibration process was performed by simulating the behaviour of a single big bag undergoing loading and unloading stages. A real scale experimental setup was implemented at the site to test the behaviour of the block by superimposing a concrete cubic weight to a big-bag and measuring the deformations at different time intervals during loading and unloading. The numerical analyses showed to be appropriate to reproduce the behaviour of the big bag at the single block scale and were adopted to study the stability of the assembly in a variety of geometrical layouts. The work performed allowed the definition of the arrangement that guarantees the stability conditions of the assembly