A Versatile Diphosphine Ligand: cis and trans Chelation or Bridging, with Self Association through Hydrogen Bonding

Abstract

The diphosphine ligand, N,N'-bis(2-diphenylphosphinoethyl)isophthalamide, dpipa, contains two amide groups and can form cis or trans chelate complexes or cis,cis or trans,trans bridged complexes. The amide groups are likely to be involved in intramolecular or intermolecular hydrogen bonding. This combination of properties of the ligand dpipa leads to very unusual structural properties of its complexes, which often exist as mixtures of monomers and dimers in solution. In the complex [Au2(μ-dpipa)2]Cl2, the ligands adopt the trans,trans bridging mode, with linear gold(I) centers, and the amide groups hydrogen bond to the chloride anions. In [Pt2Cl4(μ-dpipa)2], the ligands adopt the cis,cis bridging mode, with square planar platinum(II) centers, and the amide groups form intermolecular hydrogen bonds to the chloride ligands to form a supramolecular one-dimensional polymer. Both the monomeric and dimeric complexes [PtMe2(dpipa)] and [Pt2Me4(μ-dpipa)2] have cis-PtMe2 units with cis chelating or cis,cis bridging dpipa ligands respectively; each forms a supramolecular dimer through hydrogen bonding between amide groups and each contains an unusual NH···Pt interaction. An attempted oxidative addition reaction with methyl iodide gave the complex [PtIMe(dpipa)], which contains trans chelating dpipa, while a reaction with bromine gave a disordered complex with approximate composition [Pt2Me3Br5(μ-dpipa)2], which contains trans,trans bridging dpipa ligands.

Half-Sandwich Ruthenium Complexes of Amide-Phosphine Based Ligands: H-Bonding Cavity Assisted Binding and Reduction of Nitro-substrates

“…Hydrogen bonding (H-bonding) plays numerous important roles in the biology. , In particular, many metalloenzymes harness hydrogen bonds (H-bonds) in bringing, holding, and orienting a substrate closer to the active site, a critical step before the actual function or transformation. , Appreciable attention has been given to install H-bonding functional groups in synthetic systems. − Successful examples include the stabilization of unusual species and intermediates ,, and effective control of the reaction outcome. , H-bonding and other weak interactive forces have also been utilized for preorganizing substrates during the catalysis . Such interactions have elegantly assisted both in regio- and enantioselective catalysis by holding a substrate closer to a catalytic site. − A few supramolecular metal–ligand assemblies have also been found to aid in catalysis by stabilizing cavity-encapsulated substrates and reagents .…”

Probing the Influence of Phosphine Substituents on the Donor and Catalytic Properties of Phosphinoferrocene Carboxamides: A Combined Experimental and Theoretical Study

“…Phosphinocarboxylic amides , are versatile ligands for coordination chemistry and catalysis. Their attractiveness results mainly from their hybrid-donor character and modular structures, which allow for fine tuning to the intended purpose.…”

Two Hg(II)-Based Macrocycles Offering Hydrogen Bonding Cavities: Influence of Cavity Structure on Heterogeneous Catalysis

“…61−65 Such paucity is related to the difficulty in first synthetically installing H-bonds followed by giving them the required orientations to interact with an analyte of choice while also avoiding their undesirable interactions with lattice solvent molecules and/or anions. 61,62 Although there have been a few examples where H-bonds have been incorporated within coordination-driven self-assemblies, in most cases Hbonds have been primarily used for structural purposes rather than focusing on their influence on applications. 61−63 Our research group has recently reported two Pd(II) macrocycles synthesized using pyridine-2,6-dicarboxamide based ligands offering appended phosphine groups.…”

“…Such a fact is not only related to the presence of well-defined cavities such molecular assemblies offer but also due to the possibility to fine-tune these cavities. − Several such molecular assemblies have been effectively used in host–guest chemistry, − sensing, − drug delivery, − stabilizing reactive intermediates ,− and organic transformations. − Extensive efforts have been made to synthesize assorted molecular assemblies that show remarkable properties. , Efforts vary from the construction of molecular assemblies offering hydrophobic interior space, − and examples include various covalent bonding based assemblies with the objective to tune the cavity structure to suit an application. Efforts have also been made to construct metal–ligand coordination driven molecular assemblies that rely on the geometrical parameters of both metal(s) and ligand(s). − In such molecular assemblies, the interior space has been designed to offer hydrophobic ,− as well as hydrophilic functional groups. In contrast, examples are scarce when hydrogen bonds (H-bonds) are installed within a cavity. − Such paucity is related to the difficulty in first synthetically installing H-bonds followed by giving them the required orientations t...…”