Ladder compounds

The application of this reaction leads to the formation of a soluble drum compound, [n-BuSn C CCsHg] g CgHg, 1, Figure 2, containing cyclopentane units, and the formation of an unusual ladder compound, [(n-BuSn(0)02CPh)2 n-BuSn(Cl) (C CPh)2]2> 2> Figure 3 (4). 

Other than the chloro derivative, 2, the drum and ladder compounds are prepared in high yield, > 70%. All are soluble in organic solvents and show characteristic infrared spectra. The drum compounds and A exhibit a symmetrical doublet for the carboxylate stretching frequency, Vqqq, centered near 1550 cm 1 and a single Sn-0 stretch, v Q, near 600 cm-1. In contrast, the open-drum structures, 2 and 3, show an unsymmetrical vcoo doublet in the same region as that for the drums and the presence of two Sn-0 stretches near 600 cm. ... 

The "unfolded-drum" or "ladder" compound 2 has crystallographic symmetry. This corresponds to the idealized molecular symmetry and, therefore, there are three chemically inequivalent types of Sn atoms in the molecule, although all are hexacoordinated. The oxygen atoms in the open form can be subdivided into two types, as in the case of the drum molecule tricoordinate framework oxygen atoms and the dicoordinate oxygen atoms of the bridging carboxylate ligands. 

Dienones can behave as enones in additions to dienes479a). The interesting ladder compound in (4.67) has been isolated in moderate yields 479b). 

Before the explanation of ladder poly silanes is started, ladder compounds of other Group 14 elements are briefly mentioned. Hydrocarbons with a ladder-shaped carbon framework are known as ladderanes. The study on ladderanes goes back to 1927, when bicyclo[2.2.0]hexane ([2]ladderane) was synthesized by the reduction of dy-l,4-dibromocyclohexane with sodium.19 Ladderanes so far reported are tricyclo[4.2.0.02,5]octane ([3]ladderane),20 tetracyclo[4.4.0.02,507,1°]decane21 ([4]ladderane), and a number of their derivatives (Fig. 3). 

When anti-2 was oxidized with 3 equivalents of MCPBA, the trioxidation product 11 was obtained in 81% yield (Scheme 7). Similarly, the oxidation of anti,anti-3 and anti,anti,anti-4 with 4 and 5 equivalents of MCPBA gave the tetraoxidation product 12 and the pentaoxidation product 13, respectively, in moderate yields. Therefore, these ladder polysilanes were found to be oxidized in a unique manner one of two polysilane main chains was oxidized selectively, and novel ladder compounds consisting of polysiloxane and polysilane chains were formed. 

Ladderanes, 135-137, 158, 160 Ladder compounds, 133-166 Ladder polysilanes, 133-166 Lead, decamethylmetallocene, 1-2, 6,... 

FIGURE 6. 3D zinc phosphates with eight-membered rings obtained from the transformation of the ladder compound 2 (a) [C Halos-[Zn2(P04)2] (8) and (b) [C2N2H1o](Zn2(P04)2] (9). The features of the ladder structure can be dearly seen in the 3D strudure of 9. Such features are also present in 4 and 8. 

FIGURE 7. (a) 2D layer phosphate, [C4N2H10] (Zn PC J (10). obtained from the transformation of the ladder compound 2. (b) A 2D layer compound, [C3N2Hi2][Zn4(P04)2(HP04)2] (11), obtained from the transformation of the ladder conpound 5. Both 10and11 exhibit features of the ladder structure, from which they are formed. 

The first polyether antibiotic to be isolated was nigericin 1 in 1951. By 1983, more than 70 terrestrial polyether antibiotics had been reported and Cane et al. (1) had proposed a unified stereochemical model to account for their biosynthesis, including the polyene-polyepoxide model of polyether formation. It took almost 20 years for the first polyether gene cluster to be reported (2). In contrast, the first marine polyethers were reported in 1981, and a model to explain the biosynthesis of marine polyether ladder compounds was proposed in 2006 (3) no genetic information is available currently for the marine polyethers. 

Further progresses in comprehension would profit from more systematic comparisons of the charge transfer organic conductors and superconductors with their oxide counterparts. The example give by H. Schultz should here be followed after starting with D. Jerome a study of electron correlations in the organics that led finally to D. Jerome s and C. Bourbonnais work described here, H. Schultz centred his own activity on very similar problems in oxides, where he was one of the first to give a satisfactory description of ladder compounds. 

Another interesting application is to simulate realistic models for quantum magnets, using exchange constants calculated by ab-initio methods. Comparing these ab-initio QMC data to experimental measurements, as done for a series of vanadates [73] and for ladder compounds [71] allows to quantitatively check the ab-initio calculations. 

Although drum compounds are the must ubiquitous forms found in monoorganotin carboxylates, hexanuclear open-chain ladder compounds (Figure 2.4.10(a) and (b)) and trinuclear compounds (Figure 2.4.10(c)) are also found in some instances. The hexanuclear ladders can be converted to drums by a controlled hydrolysis. ... 

Besides the electrical conductivity, a number of other applications of [M(dmit)2] have been investigated. For example, molecular-based magnets, such as the spin ladder compound p-EPYNN][Ni(dmit)2] [p-FFYNN]" " = p-N-ethylpyridinium a-nitronyl nitroxide) was reported in 1996. In the crystal, the radical cationic molecules, p-EPYNN, form one-dimensional chains with ferromagnetic interactions, while the chains of [Ni(dmit)2] monovalent anions, in a ladder formation, exhibit antiferromagnetic interactions. The magnetisation is explained by the sum of them. 

Recently, Larkin et al. (2000) have encountered (in a study of the spin-ladder system Sr(Cui xZnj )203, which falls outside this review, but see sect. 8.3.4) muon spin relaxation functions with too shallow and too broad minima of polarization to be reproduced by Kubo-Toyabe functions. Again, longitudinal field data showed the spin system to be static. These authors used an approach (called Kubo golden rule, KGR), which was originally derived by Kubo (see Kubo 1981 and Yamazaki 1997) to describe their findings. For details we refer to the original papers. The KGR method allows the calculation of the muon spin relaxation function for arbitrary field distributions (if they can be described by arithmetic function). In the spin-ladder compound an exponential field distribution reproduced the data. The approach of Noakes and Kalvius (1997) can be reproduced using KGR. 

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