Platinum(II) Diphosphinamine Complexes for the Efficient Hydration of Alkynes in Micellar Media

Highly active monomeric bis-cationic platinum(II) catalysts bearing small bite angle diphosphinamine [N,N-bis(diarylphosphino)amine] PNP ligands efficiently catalyze Markovnikov hydration of terminal and internal alkynes to the corresponding ketones in water. Catalyst solubilization in water is achieved via ion pairing with anionic micelles formed by surfactant addition. The micelles ensure dissolution of apolar alkynes and promote the intimate contact between reagents and catalyst, while in organic-water media in the absence of surfactants the reaction is sluggish. Hydration products can be isolated by means of extraction with an apolar solvent and the catalyst, that remains confined in the aqueous phase, can be recycled up to four times without loss of catalytic activity.