(β-Oxoiminato)(phosphanyl)palladium Complexes as Highly Active Catalysts in Suzuki–Miyaura Coupling Reactions

Additive-free spin coating of tin oxide thin films: synthesis, characterization and evaluation of tin β-ketoiminates as a new precursor class for solution deposition processes

The fabrication of SnOx in thin film form via chemical solution deposition (CSD) processes is favored over vacuum based techniques as it is cost effective and simpler. The precursor employed plays a central role in defining the process conditions for CSD. Particularly for processing SnO2 layers that are appealing for sensor or electronic applications, there are limited precursors available for CSD. Thus the focus of this work was to develop metalorganic precursors for tin, based on the ketoiminate ligand class. By systematic molecular engineering of the ligand periphery, a series of new homoleptic Sn(ii) β-ketoiminate complexes was synthesized, namely bis[4-(2-methoxyethylimino)-3-pentanonato] tin, [Sn(MEKI)2] (1), bis[4-(2-ethoxyethylimino)-2-pentanonato] tin, [Sn(EEKI)2] (2), bis[4-(3-methoxypropylimino)-2-pentanonato] tin, [Sn(MPKI)2] (3), bis[4-(3-ethoxypropylimino)-2-pentanonato] tin, [Sn(EPKI)2] (4) and bis[4-(3-isopropoxypropylimino)-2-pentanonato] tin, [Sn(iPPKI)2] (5). All these N-side-chain ether functionalized compounds were analyzed by nuclear magnetic resonance (NMR) spectroscopy, electron impact mass spectrometry (EI-MS), elemental analysis (EA) and thermogravimetric analysis (TGA). The solid state molecular structure of [Sn(MPKI)2] (3) was eludicated by means of single crystal X-ray diffraction (SCXRD). Interestingly, this class of compounds features excellent solubility and stability in common organic solvents alongside good reactivity towards H2O and low decomposition temperatures, thus fulfilling the desired requirements for CSD of tin oxides. With compound 3 as a representative example, we have demonstrated the possibility to directly deposit SnOx layers via hydrolysis upon exposure to air followed by heat treatment under oxygen at moderate temperatures and most importantly without the need for any additive that is generally used in CSD. A range of complementary analytical methods were employed, namely X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to analyse the structure, morphology and composition of the SnOx layers.

Synthesis, characterization, and catalytic activity of sodium ketminiate complexes toward the ring-opening polymerization of l-lactide

Na complexes bearing ketiminate ligands revealed the greater catalytic activity and polymer controllability than that of Na complexes bearing Schiff base ligands.

Coordination of β-Ketoimine-Derived Ligands at Main Group and Transition Metals

The β-ketoimine HC[MeC(O)][MeC(NHt-Bu)] (1H) (Me = methyl) was used as a ligand in the synthesis of organo-aluminium and gallium compounds. With Al, the NH functionality was deprotonated to form the N,O-chelating β-ketoiminate ligand in Al{HC[MeC(O)][MeC(Nt-Bu)]}Me2 (3) (t-Bu = tertiary butyl), whereas the neutral form coordinated to trimethylgallium via the oxygen atom to form the adduct GaMe3·{HC[MeC(O)][MeC(NHt-Bu)]} (4). Reaction of 1H with Ar†NH2 (Ar† = 2-t-BuC6H4) afforded the new N-aryl β-ketoimine HC[MeC(O)][MeC(NHAr†)] (2H), which reacted with Pd(OAc)2 (OAc = acetate = CH3CO2–) to afford the heteroleptic dimer {Pd[HC(MeC(O))(MeC(NAr†))](μ-OAc)}2 ([5]2). The homoleptic bis(β-ketoiminate) Pd{HC[MeC(O)][MeC(NAr†)]}2 (6) was isolated as a minor product of this reaction. The crystal structures of compounds 3, 4, [5]2, and 6 are reported.

Scope and Mechanistic Study of the Coupling Reaction of α, β-Unsaturated Carbonyl Compounds with Alkenes: Uncovering Electronic Effects on Alkene Insertion vs Oxidative Coupling Pathways

The cationic ruthenium-hydride complex [(C(6)H(6))(PCy(3))(CO)RuH](+)BF(4) (-) (1) was found to be a highly effective catalyst for the intermolecular conjugate addition of simple alkenes to α,β-unsaturated carbonyl compounds to give (Z)-selective tetrasubstituted olefin products. The analogous coupling reaction of cinnamides with electron-deficient olefins led to the oxidative coupling of two olefinic C-H bonds in forming (E)-selective diene products. The intramolecular version of the coupling reaction efficiently produced indene and bicyclic fulvene derivatives. The empirical rate law for the coupling reaction of ethyl cinnamate with propene was determined as: rate = k[1](1)[propene](0)[cinnamate](-1). A negligible deuterium kinetic isotope effect (k(H)/k(D) = 1.1±0.1) was measured from both (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) and (E)-C(6)H(5)CD=C(CH(3))CONHCH(3) with styrene. In contrast, a significant normal isotope effect (k(H)/k(D) = 1.7±0.1) was observed from the reaction of (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) with styrene and styrene-d(10). A pronounced carbon isotope effect was measured from the coupling reaction of (E)-C(6)H(5)CH=CHCO(2)Et with propene ((13)C(recovered)/(13)C(virgin) at C(β) = 1.019(6)), while a negligible carbon isotope effect ((13)C(recovered)/(13)C(virgin) at C(β) = 0.999(4)) was obtained from the reaction of (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) with styrene. Hammett plots from the correlation of para-substituted p-X-C(6)H(4)CH=CHCO(2)Et (X = OCH(3), CH(3), H, F, Cl, CO(2)Me, CF(3)) with propene and from the treatment of (E)-C(6)H(5)CH=CHCO(2)Et with a series of para-substituted styrenes p-Y-C(6)H(4)CH=CH(2) (Y = OCH(3), CH(3), H, F, Cl, CF(3)) gave the positive slopes for both cases (ρ = +1.1±0.1 and +1.5±0.1, respectively). Eyring analysis of the coupling reaction led to the thermodynamic parameters, Δ H(‡) = 20±2 kcal mol(-1) and S(‡) = -42±5 e.u. Two separate mechanistic pathways for the coupling reaction have been proposed on the basis of these kinetic and spectroscopic studies.

Mild and ligand-free palladium-catalysed Suzuki–Miyaura cross-couplings in aqueous two-phase system

Pd(OAc)2 combined with an ethanol/K2HPO4 aqueous two-phase system was developed as an inexpensive and efficient catalytic system for Suzuki–Miyaura cross-coupling. The couplings between aryl iodides and arylboronic acids proceeded smoothly in moderate to excellent yields at 60°C in the aqueous two-phase system, and aryl bromides required a higher reaction temperature (reflux at about 80°C) to improve the yield.