Intramolecular hydrogen bonding and cation π-interactions affecting cis–trans isomerization in tungsten hexacarbonyl derivatives of 2-pyridyldiphenylphosphane and triphenylphosphane

Intramolecular hydrogen bonding and cation π-interactions can be used to favour cis isomers of [W(CO)4(PRPh2)2](R=2-pyridyl or phenyl) type complexes. The changes in isomerization equilibrium can be switched by protonation or deprotonation of the 2-pyridyl groups.