Ligand angle profile

Analyses of cone-angle radial profiles have been used to correlate multinu-clear NMR data with spatial regions of steric overlap (43). Cone-angle radial profiles have the potential to be used to predict relative stabilities of cis and trans isomers and to predict coordination numbers of bulky ligands. However, cone-angle profiles are very sensitive to the conformation of a ligand. 

For complex chemical systems, the analysis of ligand-property control leads to similar profiles. For the above mentioned ligand-concentration control of the system 1,3-dimethylallyl-methyl-nickel/P-ligands/CO, the corresponding profile is shown in Fig. 1 of Scheme 3.5-5. The increase of the cone angle and of the acceptor strength (high X values) favours C-C bond formation over C=0 insertion (15 over 16) ... 

Figure 12 Oliver and Smith s presentation of a ligand profile showing the variation of van der Waals contacts with the rotation () about the M-P bond resulting in cone angle 0) variations. (Reprinted with permission from Ref. 86. 1978 American Chemical Society)...

Figure 4 Generation of a ligand profile for a PR3 ligand. As the ligand rotates about the M-P bond, (j), the half cone angle varies (shown on left). The plot of half cone angle versus (j) is the ligand profile (shown on right).

Figure 5 Generation of a cone-angle radial profile, (a) A sphere of radius d (a variable) is allowed to grow from the metal toward the ligand, (b) The plot of cone angle (or solid angle see Sec. 3.4) versus radial distance, d, is called the cone-angle radial profile. (From Ref. 48.)...

Perhaps more powerful than the solid-angle radial profile is the quantification of the amount of overlap between two adjacent ligands. 

Figure 11 Use of solid-angle radial profiles, (a) Cis methyl groups give rise to the profiles indicated in (b). (b) The point marked X indicates the radial distance at which maximum steric interaction occurs. (From Ref. 48.) (c) Radial profiles for the cyclopentadienyl and P(OMe>3 ligands in [( -CbH4-p-C6H4Me)Fe(CO) P(OMe)3 l]. Nuclear magnetic resonance spectroscopy reveals steric interaction between the ligands as indicated. (From Ref. 31.)...

There is no physical overlap between the C and O atoms, yet in the projection of the ligand from the metal, the carbon atom eclipses oxygen. In the radial profile (Fig. 10), this overlap is eliminated. By using the solid-angle methodology, a quantitative measure of the amount of overlap can be attained (49). 

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