Ab initio calculations of the NMR spectra of [1.1.1]propellane and bicyclo[1.1.1]pentane

New high-level ab initio values of all the NMR shielding and spin-spin coup ling constants in [1.1.1]propellane and bicyclo[1.1.1]pentane are obtained and compared with previous theoretical results and available experimental d ata. Electron correlation effects are taken into account and large basis se ts suitable for NMR studies are applied. The results for the shielding cons tants depend primarily on the basis set, while the spin-spin coupling const ants, in particular for the carbon-carbon coupling, are very sensitive to e lectron correlation effects. The computed NMR parameters agree well with th e known experimental values, with the exception of the bridgehead-bridgehea d carbon coupling constant in [1.1.1]propellane. Our best estimates of this constant differ from the experimental value for a substituted [1.1.1]prope llane, and possible explanations of this discrepancy are discussed.