Indirekte Kernspinkopplung in den Tetramethylverbindungen der IV. Gruppe

Abstract

The indirect nuclear spin-spin coupling between protons, C13 and the spin ½ isotopes of the group IV elements (Si29, Sn119 and Pb207) were investigated in the tetramethylcompounds X(CH3)4. Substances enriched in C13 were used. The absorption of the most sensitive nucleus H1 was observed directly while the resonances of the other nuclei were located by a double resonance technique. The normalized coupling constants between directly bonded nuclei were found to be positive in all cases while their magnitudes are in good agreement with a semi-empirical estimate using the contact mechanism. All normalized two-bond X—C—H coupling constants are negative while the three-bond C—X—C—H coupling constants are positive as well as the four-bond H—C—Si—C—H coupling constant. Using these results it is shown that the sign of the normalized X—H coupling constants in the analogous hydrides XH4 are positive confirming a theoretical prediction made in previous work.