Abstract NMR spectral data for a series of substituted benzyldimethylsilanes (I) and phenyltetramethyldisilanes (II) are reported. 29 Si H and 13 C H coupling constants are shown to be correlated by Hammett σ constants. The data are discussed in terms of mechanisms of transmission of substituent effects across C—Si and Si—Si bonds. A good Hammett correlation is also found of J (13 C H) for the benzylic protons of a series of ...