Molybdenum Tricarbonyl Complexes Supported by Linear PNP Ligands: Influence of P- and N-Substituents on Relative Stability, Stereoisomerism and on the Activation of Small Molecules

Series of linear tridentate (PNPR)-P-Ph-ligands (R= Me, Et, Pln, Ph, Cyp, iPr, Cy, tBu) and molybdenum tricarbonyl complexes [Mo(CO)(3)(PNPR)-P-Ph] (R= Ph, Et, Cyp, iPr, Cy,) were synthesized and characterized using NMR-, IR-, and Raman spectroscopy as well as X-ray crystallography. The influence of the different phosphine donor groups of the PNPhPR ligands on the bonding and activation of CO ligands is investigated. Importantly, all complexes are found to adopt a fac geometry, both in solution and in the solid state. This is in contrast to analogous complexes supported by PNHP ligands. DFT calculations reveal that the phenyl ring at the central amine function is the cause of the preferred geometry, hindering isomerization to a mer geometry.