General cooperative effects of single atom ligands on the NMR signals of [AXn] (A = C, Si, Ge, Sn, Pb, Pt; Xn = combination of n halido and hydrido ligands; n = 4-6) coordination compounds

The study of the NMR chemical shift variations produced by mono atomic ligands bonded to NMR active central A atoms, in [ALn] compounds (A = C, Si, Ge, Sn, Pb, Pt; Ln = combination of n halido and/or hydrido ligands; n = 4-6) is of wide interest. In particular, we found that the observed central atoms 13C, 29Si, 73Ge, 119Sn, 195Pt, 207Pb) NMR chemical shifts, are affected by both halido and hydrido ligands ionic radii and electronegativities overall sums, Σ(rL) and Σ(L), respectively. At this regard, we generally observed simple linear correlations between the central atoms  NMR chemical shifts and the Σ(rL), when Σ(rL) results below an onset value (red line in Figure 1A). For instance, this occurs in several [AL4] coordination compounds, where the central A can show different oxidation states and geometries (octahedral, squareplanar and tetrahedral). [1-3] Interestingly, in [CL4] and [SiL4] derivatives, we could determine a dependence of the DΣ(rL) difference (indicated for example by the green double arrow in Figure 1A) on Σ(rL), as also reported in Figure 1B. Indeed, above the indicated onset value the example DΣ(rL)C variations result directly proportional to the increase of Σ(rL) (blue line in Figure 1B). Similar trends were also observed in the analogue Si derivatives.