Zusammenfassung
In half-sandwich compounds of the type [Cp*(MLLPPh3)-L-1-P-2] the PPh3 propeller is stabilized by attractive CH/pi interactions in which C-o-H bonds specifically interact with the C-i and C-o atoms of neighbouring phenyl rings, as in the T-shaped benzene dimer (i/o = ipso/ortho). This stabilization was not taken into account in a recent conformational analysis based on van der Waals energy ...
Zusammenfassung
In half-sandwich compounds of the type [Cp*(MLLPPh3)-L-1-P-2] the PPh3 propeller is stabilized by attractive CH/pi interactions in which C-o-H bonds specifically interact with the C-i and C-o atoms of neighbouring phenyl rings, as in the T-shaped benzene dimer (i/o = ipso/ortho). This stabilization was not taken into account in a recent conformational analysis based on van der Waals energy calculations and minimization of steric compression (Dalton Trans., 2015, 44, 5451-5466). It is shown that in all 116 structures discussed in this analysis the CoH-C-i/o distances fall below the sum of the van der Waals radii, establishing attractive CH/pi interactions, although the short contacts could easily be avoided by phenyl rotation to relieve steric strain. In 53 of the described structures there are acyl substituents which form conformation-determining C-o-H center dot center dot center dot O(acyl) hydrogen bonds that are not taken into account in the recent analysis. The steric-only model is not an adequate description of M-PPh3 complexes.
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