Synthesis, Interionic Structure, and Reactivity toward CO and p‐Methylstyrene of Palladacyclic Compounds Bearing α‐Diimine Ligands

Abstract

Dedicated to Professor Giambattista Consiglio on the occasion of his 65th birthday Palladacyclic compounds [Pd(C 6 [X] complexes were found to copolymerize CO and p-methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4-(o,o'-dimethylaryl)-1,4-diazabuta-1,3-dienes were used, respectively. The reactions with CO and p-methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the PdÀC bonds were isolated and completely characterized in solution.Introduction. -There is increasing evidence that the solution structure and reactivity of organometallic compounds can be altered by noncovalent interactions. For instance, when ionic compounds are considered, ion pairing may substantially affect the chemical pathway of organic reactions mediated by transition-metal organometallics in terms of chemo-, regio-, and stereoselectivity [1].It has been demonstrated that NMR spectroscopy is the technique of choice for investigating noncovalent adducts in solution, especially by NOE (nuclear Overhauser effect) and PGSE (pulsed-field gradient spin echo) experiments (for recent reviews, see [2]).For several years, our group has been involved in the application of NOE [3a -c] and PGSE [3d] NMR methodologies to determine the interionic structure in solution (namely, the relative cation-anion orientation and aggregation level) of transitionmetal complex ionic adducts. Several combinations of anions (ranging from inorganic, such as [BF 4 ] À and [PF 6 ]

Cyclometalated IrIII Complexes with Substituted 1,10‐Phenanthrolines: A New Class of Efficient Cationic Organometallic Second‐Order NLO Chromophores

“…The distinction between resonances of the two sides of the asymmetric phenanthroline ligand and of the two rings of the cyclometalated ligands was achieved by the observation of intra-and interligand key NOEs. For example, the evidence of an intra-ligand NOE between protons 7 (easily assigned being the only singlet) and 10 of the phenanthroline ligand leads to a complete assignment of the with the known low-frequency shielding of the proton close to the s-bonded carbon atom of a cyclometalated system, [20] allowed us to assign the latter signals to protons 13 and 22, respectively, of the cyclometalated ligand.…”

“…D t data were treated as described in the literature. [19][20][21][22][23][24] The measurement uncertainty was estimated by determining the standard deviation of m by performing experiments with different D values. Standard propagation of error analysis yielded a standard deviation of approximately 3-4 % in the hydrodynamic radius and 10 % in the hydrodynamic volumes and a.…”

Cationic Palladium(II) Complexes for CO/Vinyl Arene Copolymerization in the Presence of Carbon Dioxide

“…NMR diffusion methods (pulse gradient spin–echo, PGSE) in combination with heteronuclear Overhauser spectroscopy ( 1 H– 1 H NOESY and 1 H– 19 F HOESY experiments) were run in order to analyze the existence and degree of ion pairing in CD 2 Cl 2 . − …”

Dichlorido[1-(2,6-dimethylphenylimino)-1,2-diphenylpropan-2-ol-κ2N,O]palladium(II) methanol monosolvate

“…For transition metal complexes of (N,O)-bidentate ligands, see: Skrolkhod et al (2002); Macchioni et al (2002); Binotti et al (2004); Zuccaccia et al (2006). Complexes with group IV metals with (N,O)-bidentate ligands, which form sixmembered rings, have been widely used in the production of polyethylene with high molecular weight and relative narrow molecular weight distribution, see: Jia & Jin (2009); Mu et al (2009).…”

“…Therefore, different steric and electronic properties are achieved easily. Various transition metal complexes (Skrolkhod et al 2002;Macchioni et al 2002;Binotti et al 2004;Zuccaccia et al 2006) have been developed. Especially, complexes with metals of the group IV containing (N, O) ligands have been widely used to produce polyethylene with high molecular weight and relative narrow molecular weight distribution (Mu et al 2009;Jia et al 2009).…”