Ruthenium‐to‐Platinum Interactions in η 6 ,η 1 NCN‐Pincer Arene Heterobimetallic Complexes: An Experimental and Theoretical Study

A series of η 6 ,η 1 ‐heterobimetallic complexes have been prepared in which a [Ru(η 6 ‐arene)(C 5 R 5 )] + fragment (R = H or Me) and an η 1 ‐NCN‐pincer platinum fragment are combined within the same molecule. In complexes [ 2 ] + and [ 3 ] + , the ruthenium and platinum centers are η 6 and η 1 coordinated, respectively, to the same arene ring, whereas in [ 4 A ] + and [ 5 A ] + they are coordinated to two different arene rings that are linked with a covalent bond ([ 4 A ] + ) or an ethyl bridge ([ 5 A ] + ). Upon changing the organic manifold between both metal centers, very strong ([ 2 ] + ) to very weak ([ 5 A ] + ) ruthenium‐to‐platinum interactions are obtained. Experimentally, X‐ray crystal structures show an increaing steric hindrance when the Ru–Pt distance diminishes, and electrochemical and 195 Pt NMR spectroscopic studies show a decreasing electron density on platinum from [ 5 A ] + to [ 2 ] + . Theoretical DFT calculations were undertaken, which show an increasing charge on platinum from [ 5 A ] + to [ 2 ] + . Our theoretical analysis shows that the particularly strong ruthenium‐to‐platinum electronic interactions in [ 2 ] + and [ 3 ] + do not come from binding of ruthenium to platinum, but from the pincer C ipso sharing its electron density between both metal centers, which decreases the σ donation to platinum, and from increased backdonation of the platinum d electrons into the π system of the arene ring.