Staggered-parallel

Cp SnCp, Cp SnCp 13C and 119Sn NMR, CP-MAS-NMR, Moss-bauer, IR, Raman, MS and powder XRD. A Sn(II) compound. Parallel staggered conformation proposed for decaphenylstannocene while the cyclopentadienyl groups are not parallel in pentaphenylstannocene0. 151, 152... 

These systems exhibit considerable affinity for halide anions. X-ray analysis ascertained the formation of an anionic 2 1 chloride adduct of (1) where the chloride is simultaneously bound by four mercury atoms. In the crystal structures of (2) Cl and (2) l2, the anions are located within the macrocycle and complexed cooperatively by the four mercury(II) centers. Several anionic complexes of (3), including bromide, iodide, and thiocyanide salts, have been isolated. The compounds adopt multidecker stmctures with the hexacoordinated anions effectively sandwiched between two successive molecules of (3). The Lewis acidity of perfluoro-ortAo-phenylenemercury (3) has also been substantiated by its ability to form stable adducts with neutral substrates (HMPA, DMSO, ethyl acetate, and acetonitrile) and arenes. The (3) -CeHe adduct exists as extended stacks of nearly parallel, staggered molecules of (3), which sandwich benzene molecules. Similar structures have been reported for the corresponding adducts with biphenyl, naphthalene, pyrene, and triphenylene. 

Figure 19.29 The structure of [Cr( ) -C6H6)(CO)3] showing the three CO groups in staggered configuration with respect to the benzene ring the Cr-O distance is 295 pm and the plane of the 3 O atoms is parallel to the plane of the ring.

However, uranocene can be made more air-stable by use of sufficiently bulky substituents, and 1,3,5,7-tetraphenylcyclo-octatetraene yields the completely air-stable [U( -CgH4Ph4)2], in which the parallel ligands are virtually eclipsed but the phenyl substituents staggered and rotated on average 42° out of the Cg ring plane (Fig. 31.10). 

Cyclohexane is strain-free because it adopts a puckered chair conformation, in which all bond angles are near 109° and all neighboring C—H bonds are staggered. Chair cyclohexane has two kinds of positions axial and equatorial. Axial positions are oriented up and down, parallel to the ring axis, whereas equatorial positions lie in a belt around the equator of the ring. Each carbon atom has one axial and one equatorial position. 

Periplanar (Section 11.8) A conformation in which bonds to neighboring atoms have a parallel arrangement. In an eclipsed conformation, the neighboring bonds are syn periplanar in a staggered conformation, the bonds are anti periplanar. 

FIGURE 5.49 A representation of the nematic phase of a liquid crystal. The long molecules lie parallel to one another but are staggered along their long axes. 

In orthorhombic a-sulfur, the modification stable at normal conditions, S8 rings are stacked to form columns. Consecutive rings are not stacked one exactly above another (as in a roll of coins), but in a staggered manner so that the column looks like a crank shaft (Fig. 11.3). This arrangement allows for a dense packing of the molecules, with columns in two mutually perpendicular directions. The columns of one direction are placed in the recesses of the perpendicular crank shafts . In S6 and in S12 the rings are stacked exactly one above another, and the rolls are bundled parallel to each other. In the structures a... 

The structure of [Ir(cod)(dppf)]PF6 shows approximately square-planar geometry at Ir, and the cp rings of the dppf ligand are close to parallel and staggered.592 The systems [Ir(cod)(LL)]C104, where LL = dppf, l-diphenylphosphino-2-(7V,7V-dimethylamino)methyl ferrocene and 1,6-diferrocene-2,5-diazahexane, catalytically trimerize PC=CH to 1,3,5-triphenylbenzene.593 The electrochemistry of [Ir(dppf)2]BPh4 shows two one-electron reductions at —1.560 V and -1.755 V vs. ferrocenium/ ferrocene.753... 

Interconversion of the two enantiomers is possible only if the molecule is removed from the surface and rotated by 180° around an axis parallel to the substrate surface. In the case of PVBA adsorbed on Ag l 11, hydrogen bonding leads to a preference for homochiral double chains based on head-to-tail N—H—O bonds and a C2 axis relating the two strands of the chains. The chirality of the chain can be recognized in the STM images by the stagger of one strand relative to the other that arises from C—H—O bonds, as shown in Figure 1.3 [6],... 

In the Group XIV compounds the two rings are not parallel, due to the influence of the metal lone pair, giving rise to a bent-sandwich molecular structure142 (C2V symmetry), different from that in other stable cyclopentadienyl derivatives, such as Fe(Cp)2, where the two rings are parallel (D5h symmetry in the eclipsed conformation and D5d symmetry in the staggered one). 

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