Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

As an extension of the previous work on the post-modification strategy of pyridine-based PN3P group 10 metal complexes, the triazine-based PN3P pincer ligands incorporating nickel complexes, Me-Et-PN3PNiCl, and Me-Et-PN3PNiI, were synthesized and characterized. The solid state structures suggest that the N-donor atom of triazine-based PN3P ligands have more electron donating than the pyridine-based PNP pincer ligands. A new non-symmetric PONNP pincer ligand system was developed to: (1) give more parameters for electronic and steric properties (2) to block the influence of acidic proton. However, the unstable metal-hydride complexes indicate the degradable O–P bond or N–P bond of the PONNP ligand. Treating the three ligands, including tert-butyl, phenyl, and cyclopentyl substituents with NiCl2(DME) individually all resulted in the production of [(PtBuONNPtBu)NiCl]+Cl-. It suggests that both O‒P and N‒P can cleave and rearrange during the complexation. The solvent effect and time tracing experiments demonstrated that the O‒P and N‒P bond rearrangement occurs after forming the nickel complex. The finding of [(ONNPtBu)NiCl]22+(Cl-)2 indicates the weakness of the O‒P bond, suggesting the degradation of an oxygen-phosphorus bond may be the initial step of substituents rearrangement. To ensure the ligand-centered reactivity of (PtBuONNPtBu)*NiCl, a nickel-silver bimetallic complex, [(PtBuONNPtBu)*NiCl]2[AgOTf]2, was produced. In contrast to pyridine-based PN3P*NiH, there are two active sites of [(PtBuONNPtBu)*NiCl]2[AgOTf]2, the N atoms on the imine arm and pyrimidine ring. The solid-structure of the acid-base adduct compound, {[(PtBuONNPtBu)*NiCl][B(C6F5)3], demonstrates that the nitrogen atom on the pyrimidine ring is a better active site than the imine arm because of the steric effect. The molecular structures of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 and {[(PtBuONNPtBu)*NiCl][B(C6F5)3] exhibit that the pyrimidine ring of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 tends to be an aromatic zwitterionic form. The ligand backbone of {[(PtBuONNPtBu)*NiCl][B(C6F5)3] favors the dearomatized form.

A series of 24 new photoluminescent symmetric and unsymmetric -NHC pincer Pt complexes was synthesized and characterized, including collection of their 195Pt NMR chemical shifts. In total 18 new X-ray crystal structures, and photophysical studies of these photoluminescent -NHC pincer Pt complexes are reported. -NHC pincer Pt complexes were synthesized and characterized using new -NHC pincer based proligands [(RChetChetCRH3)X2, X = Cl, Br, or BPh4, where het represents imidazolyl, benzimidazolyl, and 1,2,4-triazolyl moieties; R = n-butyl, 3,3-dimethylbutyl, n-hexyl] as starting materials. A new method to synthesize Pt-Cl complexes to prevent halogen mixing was developed using tetraphenylborate salts as proligands. -NHC pincer complexes Pt(II) were oxidized to Pt(IV) complexes by reaction with Br2, I2, or iodobenzene dichloride. Photophysical studies showed emission of blue to red-orange color range for the Pt(II) complexes when irradiated with long wavelength UV light (360 nm). No visible emission for Pt(IV) complexes was observed upon irradiation at 360 nm. The tunable photoluminescence of the synthesized -NHC pincer Pt(II) complexes can be used as the materials for OLEDs. Parameters and scales that provide understanding of steric and electronic effects are essential to predicting properties, and, therefore, to systematically designing new ligands. Meridional tridentate pincer ligands are neither conveniently nor accurately described by existing options. A scale has been developed based on 195Pt NMR chemical shift that is reflective of the total donor ability of a multi-dentate ligand in a square planar complex and that does not suffer from cis/trans stereochemical issues. This scale, Platinum Electronic Parameter (PtEP) and defined as PtEP = -(195Pt NMR shift) in CDCl3 revealed significant deviations of -NHC pincer ligands, PCP and POCOP donor abilities from predicted extrapolations using existing TEP parameters. This initial data set demonstrates the applicability and broad potential of the PtEP scale.