Reactions of phosphinites with oxide surfaces: a new method for anchoring organic and organometallic complexes

Abstract

When a pincer-ligated iridium complex with a phosphinite substituent in the para-position of the aromatic backbone is immobilized on γ-alumina, it becomes a highly effective supported catalyst for the transfer-dehydrogenation of alkanes. The nature of the interaction between the organometallic complex and the support was investigated using solid-state (31)P MAS NMR spectroscopy, solution-state (1)H and (31)P{(1)H} NMR spectroscopy, IR and GC/MS analysis of extracted reaction products. The phosphinite substituent is cleaved from the pincer ligand by its reaction with hydroxyl groups on the γ-alumina surface, resulting in covalent anchoring of the complex via the aryl ring. A similar reaction occurs on silica, allowing for ready grafting onto this support as well. A strategy for anchoring homogeneous catalysts on hydroxyl-terminated oxide supports though the selective cleavage of [POR]-containing ligand substituents is suggested.

A methods study of immobilization of PONOP pincer transition metal complexes on silica polyamine composites (SPC)

“…Previous studies also showed significant up-field chemical shifts for the pincer ligands and their complexes upon immobilization on to solid supports. [28] However, CPMAS 13 C resonances of the immobilized PONOP ligand and their complexes showed good agreement with the resonances found in solution (δ 163.1, pyridine ; δ 35.5, tert-butyl carbons). [47][48][49] Solid-state CPMAS 13 assigned to the CH and CH 2 -groups of poly(allylamine) and the propyl anchors bound to the starting BP-1.…”

“…and binding of para-functionalized POCOP iridium pincers to a coordinately-unsaturated surface Al site in Al 2 O 3 . [28] The dihydride pincer complex [IrH 2 (POCOP)] was also anchored on a mesoporous silica (SBA-15) by reaction of hydride with surface silanol groups and utilized as a heterogeneous catalyst for alkene hydrogenation reactions. [29] Pd(II)-SCS pincer complexes were covalently immobilized on porous silica, poly(norborene) and cross-linked Merrifield resin supports by C.W.…”

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

“…Thea ctive sites of these key petrochemical processes are proposed to be isolated metal sites.S ections 3.2 and 3.3 will describe heterogeneous dehydrogenation catalysts (both oxidative and non-oxidative) based on supported isolated metal sites generated by SOMC; [42,43,45,46] their activity will be compared to the related systems prepared by using classical methods.T he alternative approach based on supported homogeneous catalysts [84][85][86] has recently been reviewed and will not be discussed. [87] …”

Eine Brücke zwischen industriellen und wohldefinierten Trägerkatalysatoren

“…In den Abschnitten 3.2 und 3.3 werden Heterogenkatalysatoren für die nichtoxidative und oxidative Dehydrierung mit isolierten, durch SOMC erzeugten Metallzentren beschrieben, deren Aktivität verwandten, durch klassische Verfahren hergestellten Systemen gegenübergestellt wird. Der alternative Ansatz mit trägerfixierten Homogenkatalysatoren wurde erst kürzlich in Übersicht beschrieben und wird hier nicht weiter diskutiert …”