Solvent-Dependent Hemilability of (2-Diphenylphosphino)Phenol in a Ru(II) para-Cymene System

Abstract

The addition of Ph2P(2-C6H4OH) to [(η6-p-cymene)RuCl(μ-Cl)]2 led to the formation of three distinct products, depending on the experimental conditions. The previously reported [(η6-p-cymene)RuCl{κ2P,O-PPh2(2-C6H4O)}], 1, was obtained in 90% yield using MeOH as the solvent, in the presence of a base (Et3N). Conversely, [(η6-p-cymene)RuCl{κ2P,O-PPh2(2-C6H4OH)}]Cl, [2]Cl, was afforded (88% yield) in MeOH without using the base. However, [(η6-p-cymene)RuCl2{κP-PPh2(2-C6H4OH)}], 3, was the major species in chlorinated solvents. Compounds 1, [2]Cl, and 3 were characterized by analytical and spectroscopic (IR, NMR) methods. The X-ray structures of [2]+ and 3 were determined, with the latter forming hydrogen bond dimeric units in the solid state. The dissolution of [2]Cl into a series of deuterated solvents, except methanol, led to rapid equilibration between [2]Cl and 3, revealing the hemilabile behavior of the phosphino-phenol ligand. According to Pulsed-Field Gradient Spin Echo (PGSE)-NMR and DFT studies, the ...