Direct, one-pot synthesis of POCOP-type pincer complexes from metallic nickel

Abstract

A one-pot procedure has been developed for the direct and atom-economical preparation of the pincer-type complexes (R′-POCOP^R)NiCl (R′-POCOP^R = κ^P,κ^C,κ^P-(2,6-(R₂PO)₂-R^′_n-C₆H_3−n); R = i-Pr, Ph; R^′_n = H, 4-OMe, 4-COOMe, 3,5-(t-Bu)₂). This convenient synthetic protocol involves heating a 1 : 2 : 1–2 mixture of resorcinol (or its substituted derivatives), R₂PCl, and nickel powder in toluene (at 100 °C) or acetonitrile (at 75 °C) for 18 h. The target nickel compounds can be obtained from this procedure in up to 93% yield. Using metallic palladium in this protocol instead of nickel gives the corresponding palladium complexes in low yields only (ca. 10%).