General cooperative effects of single atom ligands on a metal: a¹⁹⁵Pt NMR chemical shift as a function of coordinated halido ligands’ ionic radii overall sum

Abstract

An inverse linear relationship between the experimentally observed (195)Pt NMR signals and the overall sum of coordinated halido ligands' ionic radii was discovered in Pt(ii) and Pt(iv) complexes. The reduction of (195)Pt NMR frequencies parallels the increase of coordinated halido ligands' ionic radii sum. This suggests that each halido ligand may act as a conducting ring whose induced electric current shields the (195)Pt NMR signals proportionally to the ionic radius of the coordinated halido ligand.

Square‐Planar PtII versus Octahedral PtIV Halido Complexes: 195Pt NMR Explained by a Simple Empirical Approach

“…A good linear relationship between the observed 195 Pt NMR chemical shift frequencies and the overall sum of the ionic radii [Σ( r h )] of the coordinated halido ligands was also discovered in octahedral Pt IV complexes of the type [PtX n Y 6– n ] 2– (1 ≤ n ≤ 6; X, Y = F, Cl, Br, I; Figure , A) . Interestingly, NMR frequencies show similar linear relationships (very similar slope) to the Σ( r h ) (and to the ionic radius of each coordinated halido ligand) in both pentacoordinate Pt II[54] and octahedral Pt IV complexes, (Figure , A). Hitherto, this new concept, which we defined as “cooperative effects of single atom ligands on the 195 Pt NMR chemical shift”, did not involve square‐planar Pt II complexes with coordinated halido ligands.…”

“…To better understand the relationship between the observed NMR chemical shifts and the molecular structures of platinum complexes, we studied the Pt II pentacoordinate complexes of the type [PtXY(η 2 ‐olefin)(N^N)] and [PtXY(η 2 ‐alkyne)(N^N)] (X,Y = Cl, Br, I; N^N = dinitrogen ligand). In particular, collection of the 1 H, 13 C, 15 N, and 195 Pt NMR spectroscopic data of the considered pentacoordinate complexes allowed the linear correlation of the chemical shift frequencies with both the spatial disposition of the observed nuclei and the ionic radii of the apical halido ligands (Figure , A) , . A good linear relationship between the observed 195 Pt NMR chemical shift frequencies and the overall sum of the ionic radii [Σ( r h )] of the coordinated halido ligands was also discovered in octahedral Pt IV complexes of the type [PtX n Y 6– n ] 2– (1 ≤ n ≤ 6; X, Y = F, Cl, Br, I; Figure , A) .…”

“…In particular, collection of the 1 H, 13 C, 15 N, and 195 Pt NMR spectroscopic data of the considered pentacoordinate complexes allowed the linear correlation of the chemical shift frequencies with both the spatial disposition of the observed nuclei and the ionic radii of the apical halido ligands (Figure , A) , . A good linear relationship between the observed 195 Pt NMR chemical shift frequencies and the overall sum of the ionic radii [Σ( r h )] of the coordinated halido ligands was also discovered in octahedral Pt IV complexes of the type [PtX n Y 6– n ] 2– (1 ≤ n ≤ 6; X, Y = F, Cl, Br, I; Figure , A) . Interestingly, NMR frequencies show similar linear relationships (very similar slope) to the Σ( r h ) (and to the ionic radius of each coordinated halido ligand) in both pentacoordinate Pt II[54] and octahedral Pt IV complexes, (Figure , A).…”

“…The 195 Pt NMR chemical shifts ( δ ) of the pentacoordinate [PtXY(η 2 ‐CH 2 =CH 2 )(Me 2 phen)] (Table S1),, octahedral [PtX n Y 6– n ] 2– (Table S2),, , and square‐planar [PtX n Y 4– n ] 2– (Table ) complexes are presented together as a function of Σ( r h ) in Figure (A). Interestingly, all three considered groups of platinum complexes (two of Pt II and one of Pt IV ) exhibit a strong linear correlation between the 195 Pt NMR chemical shifts and Σ( r h ).…”

“…(A) 195 Pt NMR chemical shifts of pentacoordinate [PtXY(η 2 ‐CH 2 =CH 2 )(Me 2 phen)] (Me 2 phen = 2,9‐dimethyl‐1,10‐phenanthroline; X,Y = Cl, Br, I),, square‐planar [PtX n Y 4– n ] 2– (1 ≤ n ≤ 4; X,Y = Cl, Br, I),, and octahedral [PtX n Y 6– n ] 2– (1 ≤ n ≤ 6; X,Y = F, Cl, Br, I) complexes, as a function of the overall sum of the ionic radii of coordinated halido ligands [Σ( r h )]. The interpolating lines are shown in black and the corresponding correlation coefficients ( R 2 ) and slopes ( s ) are given.…”