Symmetrical H bond

Coordination of O and H+ gives cations such as [(acetamide)2H]+. A neutron diifraction study of its chloride salt implies two short, symmetrical H-bonds between O atoms,55 but this has been questioned on spectroscopic grounds.56... 

The effectiveness of the cleft-binding strategy is well demonstrated for oxalate, which in addition to moderately strong H-bonds retaining one end of the carboxylate in the cleft, also exhibits a short, possibly symmetric, H-bond linking the protruding carboxylate functions of the other end. 

Dinuclear complexes [M(SCN) (Ph2PO)2H ]2(M = Pd or Pt) have been prepared by metathetical reaction from the chloro-bridged dimers (see below).42 The X-ray structure (15) (see Table 1, p. 400) shows square-planar co-ordination around the Pd (N, S, 2 ) with an unusual symmetrically H-bonded anion [(Ph2PO)2H]. In view of the possibility of S- or N-bonding, molten thiocyanate is of some interest... 

Bosons corresponding to the g and u symmetrized H-bond bridge coordinates with = l and [au,at] = ]... 

Symmetric g and Antisymmetric u kth States of the Symmetrized High Frequency Mode Harmonic Hamiltonians. Symmetric g and antisymmetric u nth states of the symmetrized H-bond bridge harmonic Hamiltonians. 

The (ith eigenket of the effective Hamiltonian of the u symmetrized H-bond bridge. 

The hydrogen form of the rhenioacac (11-XXIX) has a very short symmetrical H-bond, 2.4 A, with an O—H—O angle of 172° nevertheless, it is best considered as having a localized n system as shown with an asymmetric H-bond rather than a delocalized one. 

Since the boranes satisfy criteria 3 and 5, they meet the general requirements of H bonding. Despite this positive verification that the boranes involve structural units which resemble bent but symmetrical H bonds, it may be that the similarity is only superficial. Perhaps the bonding is very different in character and, if so, other properties can be expected to differ from the usual H bond behavior. 

H bond. Some authors have felt that H bond lengths near 2.45 A would have a centrally located H atom (e.g., Rundle et aL, 1764, 1488). Speakman has proposed that potassium hydrogen bisphenylacetate has a symmetrical H bond with R = 2.55 A (1927), but Davies and... 

Theory of IR spectrum quantum-mechanical treatment of symmetrical H bond. 

H. M. E. Cardwell, J. D. Dunitz, and L. E. Orgel. J. Chem. Soc. 1953, 3740-2. IR spectra of maleic acid (and deutero-), potassium hydrogen maleate (and deutero-), possible symmetrical H bond. 

J. Chem. Phys. 15, 526 (1947). Residual entropy of KHF2, a symmetrical H bond. 

A description of the double well O-H-O bond in so-called chromous acid (in reality a Cr(III) compound, CrO(OH)) has been derived in agreement with some early INS work [7], see Fig 9.3. In symmetric H-bonds the vibrations are best described as, the symmetric stretch, VsCO-H-0), and the antisymmetric stretch, VasCO-H-O) wherev (O-H-O)... 

In strong symmetric H-bonds Vs(O-H-O) can rise to about 500 cm and v as(O-H-O) can fall to around 800 cm. Thus, the main spectral features, at least of moderate and strong H-bonds, fall in the range from 200 to 1500 cm , which is optimal for neutron spectroscopy. 

Table 6.1 Shortest possible heavy atom distances of symmetric H-bonds predicted by the valence bond order model.

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