Bent geometry

The interplay between favourable reactivity at a collinear geometry and electrostatic forces favouring a T-shaped geometry leads to a bent geometry at the transition state. 

The fluorescence spectrum of dibenz[7>,/]oxepin shows that this molecule adopts a planar structure in the excited state whereas the ground state has bent geometry as expected.19 The emission spectrum is similar to that of anthracene. 

To avoid the bent geometry required for utilisation of VPH gratings, they are sometimes combined with a prism analogously to a grism ( vrisms Fig. 8). For these,... 

For dissociation at 226 and 230 nm, the determined j3 values for the fast and slow oxygen atoms are 1.3/1.5 and 0.7/0.8, respectively. The former value corresponds to a bond angle of 120°, close to the ozone ground state equilibrium bond angle of 117°. The reduced anisotropy parameter of 0.8 implies a more strongly bent geometry with a bond angle of 100°. 

Ar4 Ar>c-o A,7 l7 This stannaketeneimine has very bent geometry 240 at die central carbon atom43. 

Based upon a VSEPR approach, we would predict tetrahedral geometry for each X atom (i.e. Si, P+, S2+) and a bent geometry for each bridging oxygen atom Therefore, a maximum of five atoms in each pyroanion can lie in a plane ... 

Donor-acceptor interactions also lead to strangely bent geometries in heavier F— M—F alkaline earth fluorides. Such bending can occur when strong ionic attractions force a filled fluoride pz orbital into proximity with an orthogonal metal pj orbital, for in this case symmetry-forbidden (pz)p —(p l)m interactions can turn on only when the strict a/n symmetry of a linear F—M—F arrangement is broken. 

What is the nature of the multiple metal-metal bonds Let us consider the specific example of HW WH, whose NBO Lewis structure exhibits five metal-metal bonds. Figure 4.24 displays the strongly trans-bent geometry of HW=WH and contour diagrams of the five metal-metal bond NBOs, each drawn in a chosen contour plane (specified in the lower-left-hand corner of the panel) to emphasize its distinguishing characteristics. 

Unlike ferrocene, group-4 metallocenes are 14-electron species and hence, very reactive [19]. These are generated in situ, for immediate reaction [9b,20] and have bent geometry (Scheme 14.4). The electron deficiency forces them to accept... 

Reduction of the distannynes with sodium or potassium gives the radical anions. [Ar Sn=SnAr ] has the trans-bent geometry given in Table 11, and shows an ESR spectrum with g= 2.0691, (ll7Sn) 0.83 mT and (117Sn) = 0.85 mT, indicating a very low unpaired spin density on tin. The main line is about 0.6mT wide, and no proton coupling is resolved. 

We shall first illustrate how the OEMO approach can be used to elucidate the effect of geminal interactions on the stability and shape of molecules. We shall utilize the molecule H20 as the model system and compare the relative stabilization of the linear and bent geometries. The analysis involves the construction of the sigma MO s of H20 from the AO s of O and the group orbitals spanning the two hydrogens. 

Despite the statistical disorder, it has been found that dioxygen binds the iron centre according to a bent geometry, as above seen for most haemoproteins. 

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