Ligands, axial/equatorial

Van Leeuwen came to the conclusion that the equatorial/equatorial configuration in particular imposes a high linearity on the formed aldehydes [26-29]. Thus, the best selectivities to the linear aldehyde species should be obtained when the bite angle has a value of about 120°. The configuration of the ligand in equatorial/axial positions (bite angle 90°) leads to lower linearity of the formed aldehydes. 

In the case of BDPP with a bite angle of 90°, the high-pressure NMR and high-pressure IR studies showed the structures of the hydrido dicarbonyl diphosphine resting state as an axial-equatorial BPT. Similar behavior was observed for the furanoside diphosphines. Dinuclear rhodium species in equilibrium with the mononuclear pentacoordinate rhodium hydride carbonyl diphosphines have been found for these ligands. The position of this equilibrium depends on the hydrogen concentration and the ligands. The rate... 

In this section, we have discussed in detail only one class of carbonyls, namely monosubstituted octahedra. More highly substituted octahedra have been less thoroughly investigated, either because the CO parameter analysis is less certain, or because the separation of ligand cis- and imns-influences is less clearcut. In substituted tetrahedra, the distinction between cis and trans CO groups does not exist, while in 5-coordinate complexes, the situation is further complicated, quite apart from the effects of substituents, by the axial-equatorial distinction. 

The coordination polyhedron of the metal in its N,N-dialkylacetamidinato derivatives is generally a distorted pentagonal bipyramid with two chlorines in the apical positions.[TaCl2Me CyNC(Me)NCy 2] adopts a different geometry, with one bidentate ligand in equatorial sites, while the other spans axial and equatiorial positions, thus maximizing the intramolecular distances between the cyclohexyl group.341... 

Mechanisms for such reactions have been viewed by the effective coordination number of the transition state. Bond rupture processes proceed via five-coordinate transition states for which idealized square-pyramidal (SP) and trigonal-bipyramidal (TBP) geometries with the dangling ligand axial or equatorial have been considered. Twist mechanisms are considered to proceed via six-coordinate transition states with idealized trigonal prismatic (TP) geometry. Twists of the chelate rings about the real or pseudo C3 axis in the case of the cis or trans isomer, respectively, and about the... 

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