Isolation and reactivity of palladium hydrido complexes: intermediates in the hydrodefluorination of pentafluoropyridine??

Dalton Transactions Pub Date: 2010-06-15 DOI: 10.1039/C0DT00086H

Abstract

The hydrido complexes trans-[Pd(H)(4-C5NF4)(PiPr3)2] (3) and trans-[Pd(H)(4-C5NF4)(PCy3)2] (5) can be prepared by reaction of trans-[Pd(F)(4-C5NF4)(PiPr3)2] (2) or trans-[Pd(F)(4-C5NF4)(PCy3)2] (4) with HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane). The iodo and triflato complexes trans-[Pd(I)(4-C5NF4)(PiPr3)2] (7) and trans-[Pd(OTf)(4-C5NF4)(PiPr3)2] (9) are generated on treatment of complex 3 with MeI or ethyltrifluoromethanesulfonate (EtOTf), respectively. Treatment of 3 with Ph3CPF6 in MeCN results in the formation of trans-[Pd(4-C5NF4)(NCMe)(PiPr3)2]PF6 (6a). Heating 3 to 60 °C gives the products of reductive elimination 2,3,5,6-tetrafluoropyridine as well as [Pd(PiPr3)2] (1). In the presence of pentafluoropyridine [Pd(PiPr3)2] (1) affords the oxidative addition product 2. In a catalytic experiment, pentafluoropyridine can be converted into 2,3,5,6-tetrafluoropyridine in the presence of HBpin with 44% yield when 10% of 3 is employed as catalyst.

Graphical abstract: Isolation and reactivity of palladium hydrido complexes: intermediates in the hydrodefluorination of pentafluoropyridine
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