Resumo

CONTRERAS, R. H. et al. Electron delocalizaton interactions and NMR spin-spin coupling constants in saturated cage compounds. An. Asoc. Quím. Argent. [online]. 2006, vol.94, n.1-3, pp.95-104. ISSN 0365-0375.

Since the cage substrate of 1-X;3-Y-bicyclo[1.1.1]pentanes is notably strained, it is expected that in compounds of this type important trans-cage spin-spin coupling constants, SSCCs, could be observed. Such SSCCs should be dominated to a great extent by the Fermi Contact, FC, contribution since this term, for long-range couplings, is transmitted by electron-transfer interactions, which in strained compounds are particularly enhanced. In this paper, both theoretically and experimentally, ⁴J(¹³C_a,¹H₃) SSCCs in 1-X-bicyclo[1.1.1]pentanes, where the a-atom of group X is ¹³C, are studied. Results are compared with similar trans-cage SSCCs in analogous compounds. Insights into electron delocalization interactions defining the experimental trends are obtained through the study of s-hyperconjugative interactions of cage bonds. These interactions are studied using the Natural Bond Orbital, NBO, method. Results suggest that multipath additivity should hold in compounds where trans-cage SSCCs are determined by charge transfer interactions.