Sandwich system

After the discovery of the oscillatory magnetic interlayer coupling between ferromagnetic films separated by a paramagnetic spacer these sandwiched systems have been a subject of intense research. There have been many attempts to explain the magnetic interlayer coupling and a great number of theoretical and experimental studies have been performed . ... 

The coverage of the survey has though been deliberately restricted to those sandwich systems in which the pseudo-axial structure is definitely established or is strongly indicated by the available evidence, and species in which extensive distortion from this geometry is likely have thus been excluded. Consequently this has had the effect of largely limiting the coverage to the metallocenes and bisarene compounds of the 3d series since in the 4c and... 

There are several polymer supported transition metal hydrofomylation catalysts (42 ). Most are attached by phosphine ligation and suffer fron catalyst leaching. There are no n5-cyclo-pentadienyl half sandwich systems despite the potentially, clearly advantageous presence of the relatively strong Cp-metal bond (43,MO. Resin 5 was used in the following brief study in which the potential of polystyrene-supported CpCo(C0)2 to function as a hydrofomylation catalyst was tested. 

Species functionalized at boron, such as 50-53, have also been prepared from the corresponding MC2B4 closo clusters via the removal of the apex BH unit (decapitation) with I M Kl)A.54 57 The same approach has been employed to link CoC2B3 units to benzene or other arenes 5 As shown in the following subsection, di- and trinuclear complexes such as 53 and 54 are easily converted to multi-triple-decker sandwich systems. 

The synthesis of new materials having novel electronic or optical properties is of great current interest. One approach to the synthesis of such materials is to systematically link small sandwich units together to form an extended multi-decker sandwich system. Immediately following the discovery of the triple-decker structure of the Cp3Ni2+ complex in early 1970s,181 Grimes and co-workers synthesized the first neutral triple-decker metallacarborane sandwich compound. Most of the subsequent research in this field, some of which has been described... 

Figure 1.17. Two kinds of mean phase boundaries of a two dye, D and D2, sandwich system. The phase boundaries are sorted according to their distance from the front and back.

NbCl2(RCp)2] (R = H, Me) complexes react with H202, affording [Nb(02)Cl(RCp)2]. In the complex with R = H the two oxygen atoms (O—O 1.47(1) A) and the chlorine atom are in the plane which bisects the Nb(Cp)2 bent sandwich system the coordination around niobium is thus pseudotetrahedral. In the presence of H202, [Nb(02)Cl(Cp)2] catalytically converts cyclohexene to its epoxide. 

Sandwich and triple-decker complexes are routinely observed for Por and Pc ligands and have attracted most attention (Fig. 21 Buchler, WeiB). The sandwich systems are thermally stable and sublimable and show only limited moisture sensitivity. The lanthanide cations are located between two saucershaped macrocycles usually forming a square antiprismatic coordination polyhedron. The separation of the two macrocyclic rings is very close, starting at... 

The sandwich system is a method of soil care which was developed at the Research Institute for Organic Farming, Frick, Switzerland. It has four main aims ... 

The principle of the sandwich system is that a strip about 50 cm wide on either side of the row of trees, outside the area of the trunks, is hoed, while at the same time low ground cover is grown on a 35-50 cm wide strip in the middle of the row, without mulching. The total volume of soil without competition from vegetation, per tree, thus remains just as large as if the whole area were hoed, or it can he varied as required. 

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