Platinum-195 nuclear magnetic resonance study of platinum(0) complexes containing a series of acetylenes

Abstract

A platinum-195 n.m.r. investigation has been performed on the acetyleneplatinum(0) complexes [Pt(RCCR′)(PPh₃)₂](R,R′= Ph,Ph; Ph,Me; Ph,OCOMe; Ph,H; Et,Et; Me,OCOMe; Me,Me; H,H; OCOEt,OCOEt; OCOMe,OCOMe; CF₃,CF₃; Ph,CN; OCOCH₂CF₃,OCOCH₂CF₃; Me,CN; H,CN; or CN,CN), and the results interpreted semiquantitatively based on charge-iterative extended Hückel molecular-orbital calculations. The platinum–phosphorus nuclear-spin coupling constant (3 303–3 887 Hz) is considerably sensitive to the electron-withdrawing ability of the acetylene substituents. A good correlation between this coupling constant and the calculated value of the mutual polarizability as well as the σ-bond population indicates that the substituent effect is transmitted through the σ framework of the complex. The dependence of the platinum chemical shift on the nature of the acetylene ligand is dominated by the electronic excitation energy which is in turn related to the π* level of the acetylene.