Postsynthetic Metal Exchange in a Metal-Organic Framework Assembled from Co(III) Diphosphine Pincer Complexes

Abstract

A Zr metal-organic framework (MOF) 1-CoCl 3 has been synthesized by solvothermal reaction of ZrCl 4 with a carboxylic acid-functionalized Co III -P N N N P pincer complex H 4 (L-CoCl 3 ) ([L-CoCl 3 ] 4- = [(2,6-(NHPAr 2 ) 2 C 6 H 3 )CoCl 3 ] 4- , Ar = p-C 6 H 4 CO 2- ). The structure of 1-CoCl 3 has been determined by X-ray powder diffraction and exhibits a csq topology that differs from previously reported ftw-net Zr MOFs assembled from related Pd II - and Pt II -P N N N P pincer complexes. The Co-P N N N P pincer species readily demetallate upon reduction of Co III to Co II , allowing for transmetalation with late second and third row transition metals in both the homogeneous complex and 1-CoCl 3 . Reaction of 1-CoCl 3 with [Rh(nbd)Cl] 2 (nbd = 2,5-nobornadiene) results in complete Rh/Co metal exchange at the supported diphosphine pincer complexes to generate 1-RhCl, which has been inaccessible by direct solvothermal synthesis. Treating 1-CoCl 3 with PtCl 2 (SMe 2 ) 2 in the presence of the mild reductant NEt 3 resulted in nearly complete Co substitution by Pt. In addition, a mixed metal pincer MOF, 1-PtRh, was generated by sequential substitution of Co with Pt followed by Rh.