Table , Table , and Table summarize all values for ethylene, propylene, and 1-butylene, respectively. The main contribution to σ11 comes from the σ(C=C) bond and σ11 decreases with the rise of the π*(C=C) energy level, thereby reflecting backdonation. For Cu(I) and Pt(II), 81% and 82% of the changes can be attributed to these effects, demonstrating how back bonding strength is reflected in σ11. The tensor component σ33 is unchanged from the gas phase molecules upon binding to the metal centers in Cu(I)-MFU-4l, consistent with experimental observations (vide infra). This absence of change is expected since a combination of the σ33 B1g symmetry and a large energy gap between the two perpendicular orbitals E(σ(C=C)) -E(σ(C-H)) leads to small shielding of ethylene, propylene, and butylene along the z-direction that is not expected to change upon binding. In other words, σ11, σ22, and δiso are related by -σ11-σ22 = 3δiso+ σ33 ≈ 3δiso+10 ppm. To further assess the π-backbonding contribution to the NMR chemical shift tensors, we calculated the energy lowering in kJ/mol on charge transfer (CT) due to backbonding as distinct from overall charge transfer for different diamagnetic metal centers. We found an increase in the normalized NMR parameters σ22, σ11, and δiso with an increase in charge transfer related to backbonding (CTback). Figure shows the changes in these parameters after subtracting the values of the adsorbed alkylene, respectively. This analysis suggests that the experimental values of σ22, σ11, and δiso reflect the extent of charge transfer attributed to π-backbonding.