Single-crystal X-ray geometries and electron density distributions of cyclopropane, bicyclopropyl and vinylcyclopropane. II. Multipole refinements and dynamic electron density distributions

Multipole refinements have been carried out with the program VALRA Y to obtain the most accurate models for the geometry and electron density description. During the ultimate multipole refinement on IF I, (i) independent reflections weighted with the reflection multiplicity were taken, (ii) extinction corrections were included for bicyclopropyl (BCP) and vinylcyclopropane (VCP), (iii) all available types of multipoles were used for C and H, viz up to hexadecapole level, and (iv) the form of the single exponential radial distribution functions for octopoles on C was varied. Final residuals are for cyclopropane (CP) C3H6: R(F)=0.0211, Rw(F)=0.0198; for BCP, C6H10: R(F)=0.0210, Rw(F) = 0.0194; and for VCP, CsHs: R(F)= 0.0159, Rw(F) = 0.0140. Pronounced features in the dynamic filtered deformation density distributions are the bent bond character in the plane of the ring and the non-cylindrical distribution around the double bond in VCP.