Measurement of long-range 29Si,13C spin-spin coupling at natural abundance

Schemes for sensitive measurements of spin-spin coupling constants between rare nuclei with low magnetogyric ratios are considered and two combinations of INEPT with gradient versions of (X,Y)HMQC and (X,Y)COSY are suggested as particularly suitable for 29Si,13C couplings. It is demonstrated that the (H,Si)INEPT-(Si,C,Si)gHMQC combination (with 29Si detection) produces excellent results even though it is theoretically inferior to the (H,Si)INEPT-(Si,C)gCOSY combination (with 13C detection).