A Rigid Linker for Site-Selective Coordination of Transition Metal Cations: Combining an Acetylacetone with a Caged Phosphine

Abstract

The combination of a soft phosphorus and a hard oxygen donor in the new ligand HacacTRIP leads to excellent site selectivity for the coordination of two different metal cations of matching Pearson character. The deprotonation step required for coordinating the acetylacetone oxygen donor further increases the selectivity. In contrast to most phosphines, the use of the caged phosphatriptycene motif enables a rigid and directional orientation of the phosphorus binding site which is required to form stable coordination network structures. In addition to the synthesis of HacacTRIP, we present its selective coordination. The deprotonated acetylacetone was selectively bound to CuII and FeIII. The solid state structure of the former displays a rare axial coordination of chloroform molecules. The phosphorus donor was selectively coordinated to the monovalent coinage metal cations CuI, AgI, and AuI. The CuI and AgI complexes represent the first examples in which a phosphatriptycene is bound to these metal cations. Heterometallic coordination compounds were characterized with combinations of these two groups. They comprise an oligonuclear CuI/CuII mixed-valence compound in which iodide binds to both CuI and CuII cations and a complex in which acacTRIP– bridges CuII and AuI. In addition to these discrete aggregates, the ligand has been used to link FeIII and AgI into a 2D coordination polymer with unprecedented trigonal planar coordination of three bulky phosphatriptycenes to a cation and resulting honeycomb topology. Its almost regular hexagons underline the desired rigidity of the ditopic acacTRIP– ligand.

New Copper Complexes with N,O-Donor Ligands Based on Pyrazole Moieties Supported by 3-Substituted Acetylacetone Scaffolds

“…Ditopic ligands based on 3-monosubstituted acetylacetone with two distinctly different coordination sites allow for assembling cations to coordination polymers, and thus add an additional degree of freedom to these complex solids [57][58][59][60][61]. Substituted acetylacetonates have often been used in this context and 3-ciano [62], 3-diazo [63], 3-pyridyl [64], 3-halogen [65], 3-caged phosphine [66], 3-(4-methylthiophenyl) [67] and 3-pyrazolyl [68] substituents, capable of supporting secondary interactions through exocyclic atoms with metal cations, have been described [57,64,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84], and the subject has recently been reviewed [85].…”

Diverse structural reactivity patterns of a POCOP ligand with coinage metals

“…The Cu1⋯Cu2 bond distance falls in the borderline of the sum of van der Waals radii, whereas the latter one is more elongated. 17,18 Treatment of 1 with two equivalents of the copper( i )–triflate(toluene) complex in dichloromethane afforded 5 with the elimination of a toluene molecule (Scheme 1). A new resonance indicated the successful complexation at δ 98.3 ppm in the 31 P NMR spectrum.…”

Synthesis and Coordination Behavior of 9,10-Diarsatriptycene

“…5 Triptycenes with heteroatoms at the bridgehead positions, called heterotriptycenes, 6 have attracted considerable attention, and various elements, such as phosphorus 7 and boron, 8 have been incorporated. Heterotriptycenes are used as ligands, 9 Lewis acids, and bases. 8,10 Diheterotriptycenes (DHT), in which two bridgehead carbon atoms are replaced by heteroatoms (Figure 1b), are an important class of heterotriptycenes.…”