Pressure‐Enhanced C–H Bond Activation in Chloromethane Platinum(II) Complexes

Abstract

The nature of the interaction between chloromethanes CH 4– n Cl n and Pt(II) complexes has been studied by high‐pressure X‐ray diffraction and infrared spectroscopy in combination with DFT calculations. In case of electron rich complexes such as d 8 ‐Pt(btz‐ N , N ′)(phenyl) L with L = phenyl, Cl, Br and btz = 2,2′‐Bi‐5,6‐dihydro‐4 H ‐1,3‐thiazine stable chloroform adducts with bridging hydrogen atoms in the η 1 (C–H)Pt moieties were isolated which display highly activated C–H bonds. This activation is a consequence of a pronounced Pt(d z ² )→σ*(C–H) back donation and is signaled by large red‐shifts of the isolated ν is (C–H) stretching modes. The extent of the C–H bond activation and covalent Pt–H bond formation in the η 1 (C–H)Pt moieties is thereby controlled by ( i ) the σ/π donor capabilities of the ligands L , ( ii ) the orientation of the coordinating C–H bond with regard to the Pt(d z ² ) orbital and ( iii ) the applied pressure.