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Trans-bending

Thus the function Vt represents one-half of the splitting of the adiabatic potentials computed for pure trans bending, and Vc one-half of the splitting of the cis-bending curves. [Pg.525]

Trans bending of the substituents and bending at the centr al carbon for silaketene (HiSiCO) become dominant for its calculated structure. The Si—C—O angle is calculated to be 167.4 and the angle created between the. Si—C bond and the vector bisecting the two Si—H bonds becomes a very shai p 89.0. The calculated bond lengths for this yet unseen moiety are 1.891 A (Si—C) and 1.148 A (C—O). [Pg.37]

Pj and p2 represent the displacement vectors of the nuclei A and D (the corresponding polar coordinates are p1 cji, and p2, < )2, respectively) p, and pc are the displacement vectors and pT, r and pc, <[)f the corresponding polar coordinates of the terminal nuclei at the (collective) trans-bending and cis-bending vibrations, respectively. As a consequence of the use of these symmetry coordinates the nuclear kinetic energy operator for small-amplitude bending vibrations represents the kinetic energy of two uncoupled 2D harmonic oscillators ... [Pg.627]

Figure 1. Unzipped polyads (bottom) from the C2H2 A 0° DF spectrum as progressions in 04 (trans bend). Each row has constant vz (CC stretch) and each column has constant 04. Integrated intensity (deperturbed Franck-Condon factor) for each polyad in the 0° DF spectrum, arranged as progressions in 04 (top). Shading indicates the value of V2 for the progression. Figure 1. Unzipped polyads (bottom) from the C2H2 A 0° DF spectrum as progressions in 04 (trans bend). Each row has constant vz (CC stretch) and each column has constant 04. Integrated intensity (deperturbed Franck-Condon factor) for each polyad in the 0° DF spectrum, arranged as progressions in 04 (top). Shading indicates the value of V2 for the progression.
The fractionation patterns exhibited % successive members of a progression of polyads (along 02, CC stretch, or along v4, trans-bend) provide a surveyor s map of IVR. One can look at the 1VR trends and see whether the multiresonance model expressed in the H nres (1 polyads provides a qualitative or quantitative representation of the fractionation patterns. The dynamics of even a four-atom molecule is so complicated that, unless one knows what to look for, one can neither identify nor explain trends in the dynamics versus V2 or u4 or Evib- Moreover, by defining the pattern of the IVR and how this pattern should scale with V2, v4, or EVib, the H res / polyad model may make it possible to detect a disruption of the pattern. Such disruptions could be due to a change in the resonance structure of the exact H near some chemically interesting topographic feature of the V(Q), such as an isomerization saddle point. [Pg.473]

H. Jacobsen and T. Ziegler, J. Am. Chem. Soc., 116,3667 (1994). Nonclassical Double Bonds in Ethylene Analogues Influence of Pauli Repulsion on Trans Bending and tt-Bond Strength. A Density Functional Study. [Pg.79]

In contrast to the C=C double bond of sterically crowded alkenes, in which variations of the bond lengths are small, the Si=Si bond lengths of dis-ilenes vary between 214 and 229 pm. The twist angle r of the two SiR2 planes varies between 0° and 25°. A further peculiarity of the disilenes, not observed in alkenes, is the possibility of trans-bending of the substituents, which is described by the trans-bent angle 0 between the SiR2 planes and the Si=Si vector. The 0 values can reach up to 34°. These differences can be... [Pg.538]

See Reference 24a. The wide range of bond lengths and trans-bending angles is caused by the bulky substituents on the double bonds. [Pg.66]

The orientations of the various tensors in the parent disilene are shown in Figure 2. Since the calculations show that trans-bending or twisting has only a small effect on the values of the tensors64, the parent compound H2Si=SiH2 is shown for simplicity in the planar form. [Pg.399]

The trans-bending phenomenon observed in disilene, digermene, and germasilene has also been related to the singlet-triplet splittings of the fragments involved. Specifically, Trinquier and Malrieu (91,92,95) have proposed, and tested, a simple model which predicts that double bonds will be unstable with respect to this distortion whenever the sum of A values... [Pg.158]


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See also in sourсe #XX -- [ Pg.11 ]




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RjM=M R2 compounds, structure and trans-bending

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