To discern the isotropic 1 H NMR chemical shift of C2H4 in Cu(I)-MFU-4l(η 2 -C2H4) we turned to C{ 1 H} heteronuclear correlation (HETCOR) spectroscopy. This double resonance NMR experiment transfers magnetization from protons ( 1 H) to adjacent C nuclear spins. As dipoledipole coupling decreases with the third power of the internuclear distance ∝ r(C-H) -3 , the final 2D spectrum at short contact times (100 µs) features those 1 H in direct proximity of C, for example the protons in 13 C2H4. To measure the contribution of the metal center to forward electron donation, we computed the C chemical shielding anisotropy tensors of acetylene. We found σ33 reflects the metal orbital contribution to forward bonding electron donation.