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B Carries Two Equivalent n-Pairs

We note from Fig. 2 that the hypothetical equilibrium conformation is pyramidal, with 0e = 46(8)°, even though the geometry of the complex is effectively planar in the zero-point state (i.e. the vibrational wavefunction has C2v symmetry) because the PE barrier at the planar (0 = 0) form is low. At the time of the publication of [112] this was a critical result because it demon- [Pg.27]

The situation for the complexes H2S- -HX and H2S- XY is different from that of their H2O analogues. It has been shown by rotational spectroscopy that the conformation at S is much more steeply pyramidal, with 90°, and [Pg.29]

It is clear from Fig. 8 and Table 1 that the angle does indeed decrease as expected if the n-pair models and rule 1 were appUcable. Moreover, the hydrogen bond non-linearity 9 decreases along the series B = oxirane, oxetane, 2,5-dihydrofuran. On the other hand, the values of 9 for oxirane- ClF and 2,5-dihydrofuran ClF (included in Fig. 8) reveal that the halogen bond shows little propensity to be non-hnear. [Pg.33]

Oxirane is an important Lewis base in the present context. The O atom carries two equivalent n-pairs of electrons, as it does in H2O, but oxirane has the advantage over water in that it is possible to determine both angles (j) and 9 for its complexes with HCl and ClF because the non-zero off-diagonal element Xflb(Cl) of the Cl nuclear quadrupole coupling tensor is available. The corresponding Lewis base in which an S atom carries two equivalent n-pairs is thiirane. Each of the pair of complexes (CH2)2S- HCl and (CH2)2S- ClF has Cs symmetry and here it is the off-diagonal element x jc(C1) that is non-zero [Pg.33]

The values of 0 are both close to 90°, which suggests an n-pair model of thiirane (see Fig. 9) similar to that described for H2S earlier. A reason for the [Pg.34]


See other pages where B Carries Two Equivalent n-Pairs is mentioned: [Pg.36]    [Pg.26]   


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