Electrophilic activation and the formation of an unusual Tl+/Cr3+ tetranuclear ion-complex adduct

Abstract

Reaction of TlPF(6) with the Cr(III) complex fac-[CrCl(3)(NPN)] (NPN = bis(2-picolyl)phenyl phosphine) did not lead to precipitation of TlCl but rather to addition of the Tl(+) cation to the CrCl(3) moiety, which resulted in a pseudo-dimeric adduct which has an unusual tetranuclear centrosymmetric structure in the solid state.

Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

“…7 Chromium-based metal complexes, both heterogeneous and homogeneous, are among the most important polyolefin catalysts and have received increasing attention because of their wide use in both ethylene polymerization and oligomerization. [41][42][43][44][45][46][47][48][49][50][51][52] However, Cr complexes bearing phenoxy-imine ligands are rare and underdeveloped. Previously, Gibson explored this ligand family for Cr-based polymerization catalysts, but only low to modest activity (usually less than 10 5 g(PE) mol −1 (Cr) h −1 ) was obtained.…”

The Diversity of the Metal-Ligand Interplay in Coordination Chemistry†

“…42 This Cr(III) complex represents a rare example of Cr-NPN system active for ethylene oligomerization in the presence of methylaluminoxane (MAO) as cocatalyst. 43 Since the generation of catalytically active species often requires the formation of cationic complexes, we reacted this complex with 1 equiv. of TlPF 6 but chloride abstraction did not occur.…”

“…Unexpectedly, this reaction afforded a novel Cr(III)/Tl(I) complex ion in which the Tl + cation has been added to the precursor complex and interacts with the three chloride ligands (Scheme 2). 43 This result indicates that chloride abstraction followed by precipitation of TlCl should not always be taken for granted and that the N py PN py ligand has a remarkable ability to stabilize a Cr(III) complex in the presence of an electrophilic reagent. Such interactions are of possible relevance to catalyst activation steps.…”

“…Such interactions are of possible relevance to catalyst activation steps. 43,44 The reactions of fac-[Cr(N py PN py )Cl 3 ] with various cocatalysts were then examined and the results are summarized in Scheme 3. 42 The reaction with MAO led to partial methylation and the mononuclear complex fac-[Cr(N py PN py )Cl 2.23 Me 0.77 ] (1) in which a coordination site trans to a nitrogen donor is one metal centre to another, 48,50 the evidence of metal-silylene moieties acting as electron donor toward an adjacent metal centre, 48,51 and metal-mediated ligand redistribution reactions between silicon and phosphorus ligands in the coordination sphere of iron.…”

Tridentate NPN Ligands with a Central Secondary Phosphine Oxide Donor and their Corresponding Metal Complexes

“…Multidentate ligands with NPN donors and pyridine moieties have been reported in the literature (Figure 1). [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Ligands with four donor atoms can bind to the metal center in a tetradentate arrangement as in complex 9; however in some cases they form tridentate complexes with a dangling arm as in 7, 12 and 19.…”