TPS structure

Rationalization for why ligand bending takes place in some tris(dithiolene) complexes has been addressed recently by Campbell and Harris (372) and previously by others (7, 357). In TP structures, the bend is thought to result from a second-order Jahn-Teller distortion where the highest occupied molecular orbital (HOMO) is lowered in energy as a result of improved overlap between the ligand nv and the metal dz2 orbitals as depicted in Fig. 23 (372). 

Thus, for theoretical calculations of the sarcophaginate and sepulchrate structures, one should take into account inter- and intramolecular nonbonded interactions and electronic effects. The calculations based on geometric and/or repulsion models are obviously justified only for complexes with insufficient or no preference for TAP or TP structure (ALFSE = 0). In this case, the ligand determines the complex geometry. In all other cases, the contribution of the metal ion electronic configuration cannot be neglected [178],... 

The coordination polyhedron geometry of tin-, antimony- and germanium-capped iron(II) dioximates was analyzed in the previous section. As mentioned above, the boron-capped clathrochelates have a distorted TP structure and positive QS values, whereas tin-, antimony- and germanium-capped clathrochelates have distorted TAP geometry, preferably for complexes with electronic configuration d , and a negative QS sign. 

A more recent example of this chemistry is shown in equation 8.68.95 Here the sterically-demanding Cp and Tp (structure 34)96 ligands dictate the course of the... 

Figure 12.27 (a) trigonal bypyramid tbp) and (b) trigonal pyramid (tp) structures of TeOj. 

This reaction (cf. 95CHE1251), earlier described as being dependent on unusual TP structures or extreme conditions, was now found to be predominant in the series of 3-alkyl-5-methyl-6-nitro-7-oxo TPs unsubstituted in the 2-position (e.g., 136, Scheme 37) (01RCB682). The triazole ring is exclusively cleaved in the presence of strong bases or C-nucleophiles to obtain pyrimidones such as 145. Under the influence of ethanolic alkali, after short reaction times, a mixture of intermediate cyanamide 144 and product 145 was obtained. 

The substitution reactions of [NbCl2(BnSC=CSBn)(Tp )], structurally characterized, have been recently investigated.42... 

Thus, (33) has a close resemblance to the conventional expression in (3). Equation (33) takes the distribution of atomic positions into account as well as the finite duration of the X-ray probe pulse. Clearly, if the temporal duration of the X-ray pulse is short compared to the molecular dynamics, the diffraction signal corresponds to diffraction from the instantaneous distribution of atomic positions, p(R, tp). at time tp. Structure determination of short-lived intermediates can be accomplished with long probe pulses, i.e., long on the timescale of atomic motion but short compared to the lifetime of the population. This limit corresponds to current experiments where fast kinetics is studied by X-ray pulses from synchrotrons. 

Wright SFI, Wunz TM, Wunz TP. Structure and interaction of inhibitors with the tetraethylammoniunVFI+ exchanger of rabbit... 

X-ray diffraction studies [22] indicated that [M(NO)(L)4] complexes of 8 and 9 group of the periodic table adopt either trigonal bipyramidal (TBP) or tetragonal pyramidal (TP) structures. Sometimes, however, the distinctions between these two stmctures are not unambiguous due to the distortions which are caused by the steric hindrance produced by the auxiliary ligands or by the presence of strong o-donor in the base of the TP structure or in the axial and equatorial positions of the TBP... 

Other structures. This is consistent with the dipole moment results reported above in Table 5. For both FP and TP, structure IV has a significantly smaller molecular dipole moment, which in turn results in a smaller aqueous hydration free energy. There may also be local hydration effects at work, such as explicit hydrogen bonding, which is not considered in this work. 

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