H-Bonding Assisted Self-Assembly of Anionic and Neutral Ligand on Metal: A Comprehensive Strategy To Mimic Ditopic Ligands in Olefin Polymerization

Abstract

Self-assembly of two neutral ligands on a metal to mimic bidentate ligand coordination has been frequently encountered in the recent past, but self-assembly of an anionic ligand on a metal template alongside a neutral ligand remains an elusive target. Such a self-assembly is hampered by additional complexity, wherein a highly negatively charged anion can form intermolecular hydrogen bonding with the supramolecular motif, leaving no scope for self-assembly with neutral ligand. Presented here is the self-association of anionic ligand 3-ureidobenzoic acid (2a) and neutral ligand 1-(3-(diphenylphosphanyl)phenyl)urea (1a) on a metal template to yield metal complex [{COOCHNH(CO)NH}{PhPCHNH(CO)NH}PdMeDMSO] (4a). The identity of 4a was established by NMR and mass spectroscopy. Along the same lines, 3-(3-phenylureido)benzoic acid (2b) and 1-(3-(diphenylphosphanyl)phenyl)-3-phenylurea (1b) self-assemble on a metal template to produce palladium complex [{COOCHNH(CO)NHPh}{PhPCHNH(CO)NHPh}PdMePy] (5c). The existence of 5c was confirmed by Job plot, 1-2D NMR spectroscopy, deuterium labeling, IR spectroscopy, UV-vis spectroscopy, model complex synthesis, and DFT calculations. These solution and gas phase investigations authenticated the presence of intramolecular hydrogen bonding between hydrogen's of 1b and carbonyl oxygen of 2b. The generality of the supramolecular approach has been validated by preparing six complexes from four monodentate ligands, and their synthetic utility was demonstrated in ethylene polymerization. Complex 4a was found to be the most active, leading to the production of highly branched polyethylene with a molecular weight of 55700 g/mol and melting temperature of 112 °C.

Structural Diversity in Supramolecular Organization of Anionic Phosphate Monoesters: Role of Cations

“…After the imidazolium-based cations, which contain only H-bond donor unit(s), we considered 1,4-diazabicyclo[2.2.2]­octane (DABCO), which should result in the 1,4-diazabicyclo[2.2.2]­octan-1-ium cation VII with both H-bond acceptor and H-bond donor sites and thus capable of functioning in a ditopic manner. − Compound 14 was obtained by treating the ligand 1 with 1 equiv of DABCO and crystallized from a hot DMF/CH 3 OH mixture (Scheme ). So far, we were unable to obtain high-quality single-crystal X-ray diffraction data, and therefore, we are not discussing any metric parameters of this compound (Figure ).…”

Status of Organometallics and Catalysis Research in India: N–Heterocyclic Carbene (NHC) Ligands for Organometallic Catalysis

“…Balaraman group (IISER-Tirupati) efforts lie in the domain of catalytic hydrogenation and dehydrogenation reactions (Midya et al, 2015;Sahoo et al, 2017;Sahoo et al, 2018;Jaiswal et al, 2017;Nandakumar et al, 2015). Chikkali group (CSIR-NCL) uses metal catalysts bearing phosphorus ligands featuring supramolecular binding property for hydrophosphination, hydrogenation, hydroformylation, polymerization reactions (Koshti et al, 2014;Koshti et al, 2015;Pandey and Chikkali, 2015;Pandey et al, 2018;Mote et al, 2017). Biplab group (IISERK) is developing new synthetic methodology using manganese catalyst to construct new C-C bonds by alcohols activation (Barman et al, 2018a;Maji and Barman, 2017;Barman et al, 2018b;Jana et al, 2018).…”

Pd‐Iminocarboxylate Complexes and Their Behavior in Ethylene Polymerization

“…Whereas, the corresponding Pd-complexes produced ethylene oligomers (Figure 1C, 2). It has been recently demonstrated that an aminocarboxylate ligated nickel complex can catalyze ethylene dimerizationr eaction in presence of suitablea ctivator.I nt he view of prior art in this field [12,13] and our previous work, [14][15][16] we envisioned that an iminocarboxy ligated metal complex might catalyze the ethylene polymerization reaction. [10] While, specially designed ligand backbone comprising N-heterocyclic carbene were found to be active in ethylene polymerization (Figure 1C, 4).…”

“…[11] Based on the above discoveries, we pondered about the choice of the bidentate ligand that can yield single component neutralm etal complex, which may catalyzee thylene polymerization reaction. It has been recently demonstrated that an aminocarboxylate ligated nickel complex can catalyze ethylene dimerizationr eaction in presence of suitablea ctivator.I nt he view of prior art in this field [12,13] and our previous work, [14][15][16] we envisioned that an iminocarboxy ligated metal complex might catalyze the ethylene polymerization reaction.…”

“…It has been recently demonstrated that an aminocarboxylate ligated nickel complex can catalyze ethylene dimerization reaction in presence of suitable activator. In the view of prior art in this field and our previous work, we envisioned that an iminocarboxy ligated metal complex might catalyze the ethylene polymerization reaction.…”