Asymmetric Transfer Hydrogenation of Ketones Improved by PNN-Manganese Complexes.

Chiral manganese(I) complexes that contain carbocyclic-fused 8-amino-5,6,7,8-tetrahydroquinolinyl groups that are appended with distinct -R substituents have proven to be effective catalysts in the asymmetric transfer hydrogenation (ATH) of a wide range of ketones (48 examples). Notably, proved to be the most productive catalyst, allowing an outstanding turnover number of 8300 with catalyst loadings as low as 0.01 mol %.

Robust and efficient transfer hydrogenation of carbonyl compounds catalyzed by -Mn(I) complexes.

A series of manganese(I) carbonyl complexes bearing structurally related - and -chelating ligands have been synthesized and assessed as catalysts for transfer hydrogenation (TH). Notably, the -systems based on -R functionalized 5,6,7,8-tetrahydroquinoline-8-amines, proved the most effective in the manganese-promoted conversion of acetophenone to 1-phenylethanol. In particular, the -isopropyl derivative, Mn1, when conducted in combination with -BuONa, was the standout performer mediating not only the reduction of acetophenone but also a range of carbonyl substrates including (hetero)aromatic-, aliphatic- and cycloalkyl-containing ketones and aldehydes with especially high values of TON (up to 17 200; TOF of 3550 h).

,-Bis(2,4-Dibenzhydryl-6-cycloalkylphenyl)butane-2,3-diimine-Nickel Complexes as Tunable and Effective Catalysts for High-Molecular-Weight PE Elastomers.

Four examples of ,-bis(aryl)butane-2,3-diimine-nickel(II) bromide complexes, [ArN=C(Me)-C(Me)=NAr]NiBr (where Ar = 2-(CH)-4,6-(CHPh)CH (), Ar = 2-(CH)-4,6-(CHPh)CH (), 2-(CH)-4,6-(CHPh)CH () and 2-(CH)-4,6-(CHPh)CH ()), disparate in the ring size of the -cycloalkyl substituents, were prepared using a straightforward one-pot synthetic method. The molecular structures of and highlight the variation in the steric hindrance of the -cyclohexyl and -cyclododecyl rings exerted on the nickel center, respectively. By employing EtAlCl, EtAlCl or MAO as activators, - displayed moderate to high activity as catalysts for ethylene polymerization, with levels falling in the order (cyclohexyl) > (cyclopentyl) > (cyclododecyl) > (cyclooctyl).

Exploring fluoride effects in sterically enhanced cobalt ethylene polymerisation catalysts; a combined experimental and DFT study.

The fluoro-substituted 2,6-bis(arylimino)pyridine dichlorocobalt complexes, [2-{CMeN(2,6-(PhCH)-3,4-FCH)}-6-(CMeNAr)CHN]CoCl (Ar = 2,6-MeCH Co1, 2,6-EtCHCo2, 2,6-iPrCHCo3, 2,4,6-MeCHCo4, 2,6-Et-4-MeCHCo5), were synthesized in good yield from the corresponding unsymmetrical ,,'-ligands, L1-L5. Besides characterization of Co1-Co5 by FT-IR spectroscopy, F NMR spectroscopy and elemental analysis, the molecular structures of Co2 and Co5 were also determined highlighting the unsymmetrical nature of the terdentate ligand and the -square pyramidal geometry about the metal center. When either MAO or MMAO were employed as activators, Co1-Co5 were able to achieve a wide range of catalytic activities for ethylene polymerisation.

High molecular weight PE elastomers through 4,4-difluorobenzhydryl substitution in symmetrical α-diimino-nickel ethylene polymerization catalysts.

The following family of ,-diaryl-2,3-dimethyl-1,4-diazabutadienes, ArN[double bond, length as m-dash]C(Me)C(Me)[double bond, length as m-dash]NAr (Ar = 2,6-Me-4-{CH(4-FCH)}CHL1, 2-Me-6-Et-4-{CH(4-FCH)}CHL2, 2,4-{CH(4-FCH)}-6-MeCHL3, 2,4-{CH(4-FCH)}-6-EtCHL4, 2,4-{CH(4-FCH)}-6-iPrCHL5), each incorporating -substituted 4,4-difluorobenzhydryl groups but differing in the -pairing, have been synthesized and used as precursors to their respective nickel(ii) bromide complexes, Ni1-Ni5. Compound characterization has been achieved through a combination of FT-IR, multinuclear NMR spectroscopy (H, C, F) and elemental analysis. In addition, L1, Ni1 and Ni5 have been structurally characterized with Ni1 and Ni5 revealing similarly distorted tetrahedral geometries about nickel but with distinct differences in the steric protection offered by the -substituents.

Bis(imino)-6,7-dihydro-5-quinoline-cobalt complexes as highly active catalysts for the formation of vinyl-terminated PE waxes; steps towards inhibiting deactivation pathways through targeted ligand design.

A set of five related bis(imino)-6,7-dihydro-5-quinoline-cobalt(ii) complexes, [2-(ArN = CPh)-8-(NAr)-CHN]CoCl (Ar = 2,6-MeCHCo1, 2,6-EtCHCo2, 2,6-i-PrCHCo3, 2,4,6-MeCHCo4, 2,6-Et-4-MeCHCo5), have been synthesized in reasonable yield by the template reaction of cobalt(ii) chloride hexahydrate, 2-benzoyl-6,7-dihydro-5-quinolin-8-one and the corresponding aniline. The molecular structures of Co1 and Co4 highlight both the differences in the two imino-carbon environments (phenyl-capped chain cyclic) and also the steric properties exerted by the bulky -aryl groups. On pre-treatment with either modified methylaluminoxane (MMAO) or methylaluminoxane (MAO), all complexes proved productive catalysts for the polymerization of ethylene.

Bis-cycloheptyl-fused bis(imino)pyridine-cobalt catalysts for PE wax formation: positive effects of fluoride substitution on catalytic performance and thermal stability.

The α,α'-bis(imino)-2,3:5,6-bis(pentamethylene)pyridyl-cobalt(ii) chlorides, [2,3:5,6-{C4H8C(N(2-R1-4-R3-6-R2C6H2))}2C5HN] CoCl2 (R1 = Me, R2 = R3 = CH(p-FPh)2Co1; R1 = Et, R2 = R3 = CH(p-FPh)2Co2; R1 = i-Pr, R2 = R3 = CH(p-FPh)2Co3; R1 = Cl, R2 = R3 = CH(p-FPh)2Co4; R1 = F, R2 = R3 = CH(p-FPh)2Co5; R1 = F, R2 = R3 = CHPh2Co5'', R1 = R2 = Me, R3 = CH(p-FPh)2Co6; R1 = R3 = Me, R2 = CH(p-FPh)2Co7), have been synthesized by a one-pot template reaction of α,α'-dioxo-2,3:5,6-bis(pentamethylene)pyridine, cobalt(ii) chloride and the respective aniline in n-butanol. By contrast, the mixed cobalt(ii) chloride/acetate complex, [2,3:5,6-{C4H8C(N(2-F-4,6-(CH(p-FPh)2)2C6H2))}2C5HN]CoCl(OAc) (Co5'), was isolated when the corresponding template reaction was carried out in acetic acid. Structural characterization of Co4, Co5 and Co5'' revealed distorted square pyramidal geometries while six-coordinate Co5', incorporating a chelating acetate ligand, exhibited a distorted octahedral geometry.

High molecular weight polyethylenes of narrow dispersity promoted using bis(arylimino)cyclohepta[b]pyridine-cobalt catalysts ortho-substituted with benzhydryl & cycloalkyl groups.

A one-pot template strategy has been utilized to synthesize sterically enhanced bis(imino)cyclohepta[b]pyridine-cobalt(ii) chlorides, [2-{(Ar)N[double bond, length as m-dash]CMe}-9-{N(Ar)}C10H10N]CoCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Co1, 2-(C6H11)-4,6-(CHPh2)2C6H2Co2, 2-(C8H15)-4,6-(CHPh2)2C6H2Co3, 2-(C12H23)-4,6-(CHPh2)2C6H2Co4, 2,6-(C5H9)2-4-(CHPh2)C6H2Co5). All five complexes have been characterized by a combination of FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Co1, Co3 and Co5 highlight the substantial steric hindrance imparted by the 2-cycloalkyl-6-benzhydryl or 2,6-dicyclopentyl ortho-substitution pattern; distorted square pyramidal geometries are exhibited in each case.

Fusing Carbocycles of Inequivalent Ring Size to a Bis(imino)pyridine-Iron Ethylene Polymerization Catalyst: Distinctive Effects on Activity, PE Molecular Weight, and Dispersity.

The 4,6-bis(arylimino)-1,2,3,7,8,9,10-heptahydrocyclohepta[]quinoline-iron(II) chlorides (aryl = 2,6-MeCH ; 2,6-EtCH ; 2,6--PrCH ; 2,4,6-MeCH ; and 2,6-Et-4-MeCH ) have been prepared in good yield by a straightforward one-pot reaction of 2,3,7,8,9,10-hexahydro-1H-cyclohepta[]quinoline-4,6-dione, FeCl·4HO, and the appropriate aniline in acetic acid. All ferrous complexes have been characterized by elemental analysis and FT-IR spectroscopy. In addition, the structure of has been determined by single crystal X-ray diffraction, which showed the iron center to adopt a distorted square pyramidal geometry with the saturated sections of the fused six- and seven-membered carbocycles to be -configured.

Probing the effect of ortho-cycloalkyl ring size on activity and thermostability in cycloheptyl-fused N,N,N-iron ethylene polymerization catalysts.

The syntheses of six bis(imino)-5,6,7,8-tetrahydrocycloheptapyridine-iron(ii) chloride complexes, [2-{(Ar)NCMe}-9-{N(Ar)}CHN]FeCl (Ar = 2-(CH)-6-MeCHFe1, 2-(CH)-6-MeCHFe2, 2-(CH)-6-MeCHFe3, 2-(CH)-4,6-MeCHFe4, 2-(CH)-4,6-MeCHFe5, 2-(CH)-4,6-MeCHFe6), are reported in which the ring size of the ortho-cycloalkyl group has been varied as has the type of para-substituent. The molecular structures of Fe3 and Fe6 reveal square pyramidal geometries at iron while the ortho-cyclooctyl rings adopt boat-chair conformations. On treatment with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all six complexes showed optimal activities at 80 °C [up to 1.

Steric and electronic modulation of iron catalysts as a route to remarkably high molecular weight linear polyethylenes.

Five structurally related bis(arylimino)pyridine-iron(ii) chloride complexes, [2-[CMeN{2,6-{(4-FC6H4)2CH}2-4-NO2}]-6-(CMeNAr)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3Fe1, 2,6-Et2C6H3Fe2, 2,6-i-Pr2C6H3Fe3, 2,4,6-Me3C6H2Fe4, and 2,6-Et2-4-MeC6H2Fe5), incorporating one N-2,6-bis{di(4-fluorophenyl)methyl}-4-nitrophenyl group and one distinct N-aryl group, have been prepared in good yield through the interaction of the corresponding free ligands (L1-L5) with FeCl2·4H2O. All ferrous complexes were paramagnetic which was manifested by broad and highly shifted peaks in their 1H NMR spectra. The marked steric imbalance imposed by the two inequivalent N-aryl groups was a key feature highlighted in the molecular structures of representative complexes Fe1 and Fe2.

1,5-Naphthyl-linked bis(imino)pyridines as binucleating scaffolds for dicobalt ethylene oligo-/polymerization catalysts: exploring temperature and steric effects.

Six examples of dinuclear bis(imino)pyridine-cobalt(ii) complexes, [1,5-{2-(CMe[double bond, length as m-dash]N)-6-(CMe[double bond, length as m-dash]N(2,6-R-4-R-CH))CHN}(CH)]CoCl (R = Me, R = H Co1; R = Et, R = H Co2; R = Pr, R = H Co3; R = Me, R = Me Co4; R = Et, R = Me Co5; R = CHPh, R = Me Co6), have been prepared from the corresponding bis(tridentate) compartmental ligands (L1-L6) in reasonable yields. The molecular structures of Co3 and Co5 revealed two N,N,N-cobalt dichloride units to adopt anti-positions about the 1,5-naphthyl linking unit, with each cobalt center exhibiting a distorted trigonal bipyramidal geometry. On activation with either MAO or MMAO, Co1-Co6 were shown to promote both polymerization and oligomerization of ethylene with high overall activities (up to 1.

gem-Dimethyl-substituted bis(imino)dihydroquinolines as thermally stable supports for highly active cobalt catalysts that produce linear PE waxes.

Six types of 2,8-bis(imino)-7,7-dimethyl-5,6-dihydroquinoline, 2-(ArN[double bond, length as m-dash]CMe)-8-(ArN)-7,7-MeCHN (Ar = 2,6-MeCHL1, 2,6-EtCHL2, 2,6-PrCHL3, 2,4,6-MeCHL4, 2,6-Et-4-MeCHL5, 2,4,6-BuCHL6), distinguishable by their steric and electronic profile, are described that can readily undergo complexation with cobaltous chloride to form their corresponding LCoCl chelates, Co1-Co6. The molecular structures of Co2 and Co3 reveal square pyramidal geometries with ring puckering a feature of the gem-dimethyl section of their unsymmetrical N,N,N'-ligands. On activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the cobalt complexes exhibited exceptionally high activities for ethylene polymerization with levels reaching up to 1.

Bimetallic Aluminum 5,6-Dihydro-7,7-dimethyl quinolin-8-olates as Pro-Initiators for the ROP of ε-CL; Probing the Nuclearity of the Active Initiator.

Six examples of aluminum 5,6-dihydro-7,7-dimethylquinolin-8-olates, [{2-R¹-7,7-Me₂-8-R²C₉H₆N-8-O}AlR³₂]₂ (R¹ = R² = H, R³ = Me ; R¹ = R² = H, R³ = Et ; R¹ = R² = H, R³ = -Bu ; R¹ = Cl, R² = H, R³ = Me ; R¹ = H, R² = R³ = Me ; R¹ = Cl, R² = R³ = Me ), have been prepared by treating the corresponding pro-ligand (⁻) with either AlMe₃, AlEt₃ or Al(-Bu)₃. All complexes have been characterized by ¹H and C NMR spectroscopy and in the case of and by single crystal X-ray diffraction; dimeric species are a feature of their molecular structures. In the presence of PhCH₂OH (BnOH), ⁻ displayed good control and efficiency for the ROP of ε-CL with almost 100% conversion achievable in 10 min at 90 °C; the chloro-substituted and notably exhibited the lowest activity of the series.

Bis(imino)pyridines fused with 6- and 7-membered carbocylic rings as N,N,N-scaffolds for cobalt ethylene polymerization catalysts.

The unsymmetrical diketone, 1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-dione, based on a central pyridine unit fused by both 6- and 7-membered rings, has been synthesized via a sequence of reactions including ruthenium-catalyzed coupling cyclization. Templating this diketone with a mixture of cobalt(ii) chloride hexahydrate and the corresponding aniline in acetic acid at reflux afforded five examples of carbocyclic-fused bis(arylimino)pyridine-cobalt(ii) chlorides (aryl = 2,6-Me2Ph Co1, 2,6-Et2Ph Co2, 2,6-i-Pr2Ph Co3, 2,4,6-Me3Ph Co4, 4-Me-2,6-Et2Ph Co5) in good yield. All cobalt complexes have been fully characterized including by 1H NMR spectroscopy which reveals broad but assignable paramagnetically shifted peaks.

Plastomeric-like polyethylenes achievable using thermally robust N,N'-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups.

A new set of five unsymmetrical N,N'-diiminoacenaphthenes, 1-[2,6-{(4-FCH)CH}-4-NOCHN]-2-(ArN)CCH (Ar = 2,6-MeCHL1, 2,6-EtCHL2, 2,6-PrCHL3, 2,4,6-MeCHL4, 2,6-Et-4-MeCHL5), have been synthesized and used to prepare their corresponding nickel(ii) halide complexes, LNiBr (Ni1-Ni5) and LNiCl (Ni6-Ni10). The molecular structures of Ni3(OH) and Ni4 reveal distorted square pyramidal and tetrahedral geometries, respectively, while the H NMR spectra of all the nickel(ii) (S = 1) complexes show broad paramagnetically shifted peaks. Upon activation with either methylaluminoxane (MAO) or ethylaluminum sesquichloride (EtAlCl, EASC), Ni1-Ni10 displayed very high activities for ethylene polymerization with the optimal performance being observed using 2,6-dimethyl-containing Ni1 in combination with EASC (1.

Cycloheptyl-fused N,N,N'-chromium catalysts with selectivity for vinyl-terminated polyethylene waxes: thermal optimization and polymer functionalization.

Five chromium(iii) chloride complexes, [2-{(Ar)N[double bond, length as m-dash]CMe}-9-{N(Ar)}C10H10N]CrCl3 (Ar = 2,6-Me2C6H3Cr1, 2,6-Et2C6H3Cr2, 2,6-i-Pr2C6H3Cr3, 2,4,6-Me3C6H2Cr4, 2,6-Et2-4-MeC6H2Cr5), each chelated by a sterically and electronically different cycloheptyl-fused N,N,N'-bis(imino)pyridine, have been synthesized by the reactions of CrCl3(THF)3 with the corresponding ligand (L1/L1'-L5/L5'). The molecular structure of Cr2 highlights both the steric properties exerted by the inequivalent N-2,6-ethylphenyl groups and the puckering of the fused cycloheptyl ring; a distorted octahedral geometry is conferred about the metal center. On activation with methylaluminoxane (MAO) or modified MAO (MMAO), Cr1-Cr5 displayed their optimal activity for ethylene polymerization at temperatures between 70 and 80 °C with the least sterically demanding Cr1 proving the most productive (1.

Ligand and solvent control of selectivity in the C-H activation of a pyridylimine-substituted 1-naphthalene; a combined synthetic and computational study.

The pyridylimine-substituted 1-naphthalenes, 2-(1-C10H7)-6-{CR[double bond, length as m-dash]N(2,6-i-Pr2C6H3)}C5H3N (R = Me HLMe, H HLH), react with Na2[PdCl4] in acetic acid at elevated temperature to afford either ortho-C-Hnaphthyl activated (LMe)PdCl (2ortho) or the unactivated adduct (HLH)PdCl2 (1b). Alternatively, 1b and its ketimine analogue (HLMe)PdCl2 (1a), can be prepared by treating (MeCN)2PdCl2 with either HLMe or HLH in chloroform at room temperature. Regio-selective ortho-C-H activation to form 2ortho can also be initiated by the thermolysis of 1a in acetic acid, while no reaction occurs under similar conditions with 1b.

An air and moisture tolerant iminotrihydroquinoline-ruthenium(ii) catalyst for the transfer hydrogenation of ketones.

Reaction of 8-amino-5,6,7,8-tetrahydroquinoline with RuCl2(PPh3)3 at room temperature affords the ruthenium(ii) chelate (8-NH2-C9H10N)RuCl2(PPh3)2 (E), in which the two triphenylphosphine ligands are disposed mutually cis. By contrast, when the reaction is performed at reflux ligand oxidation/dehydrogenation occurs along with cis-trans reorganization of the triphenylphosphines to form the 8-imino-5,6,7-trihydroquinoline-ruthenium(ii) complex, (8-NH-C9H9N)RuCl2(PPh3)2 (F). Complex F can also be obtained in higher yield by heating a solution of E alone to reflux.

Methylene-bridged bimetallic bis(imino)pyridine-cobaltous chlorides as precatalysts for vinyl-terminated polyethylene waxes.

Four examples of phenol-substituted methylene-bridged bis(imino)pyridines, CH(C6H4-4-OH){2'-(4-C6H2-2,6-R22N[double bond, length as m-dash]CMe)-6'-(2'',6''-R12C6H3N[double bond, length as m-dash]CMe)C5H3N}2 [R1 = R2 = Me L1, R1 = R2 = Et L2, R1 = Et, R2 = Me L3, R1 = iPr, R2 = Me L4], have been synthesized and fully characterized. Treatment of L1-L4 with two equivalents of cobaltous chloride affords the bimetallic complexes, [(L)Co2Cl4] (L = L1Co1, L2Co2, L3Co3, L4Co4), in good yield. The molecular structure of Co1 shows the two metal centers to be separated by a distance of 13.

ortho-Cycloalkyl substituted N,N'-diaryliminoacenaphthene-Ni(ii) catalysts for polyethylene elastomers; exploring ring size and temperature effects.

A family of six unsymmetrical N,N'-diiminoacenaphthene-nickel(ii) bromide complexes, [1-{2,6-(PhCH)-4-MeCHN}-2-(ArN)CCH]NiBr (Ar = 2-(CH)-6-MeCHNi1, 2-(CH)-6-MeCHNi2, 2-(CH)-6-MeCHNi3, 2-(CH)-4,6-MeCHNi4, 2-(CH)-4,6-MeCHNi5, 2-(CH)-4,6-MeCHNi6), each bearing one ring-size variable 4-R-2-methyl-6-cycloalkyl-substituted N-aryl group and one N'-4-methyl-2,6-dibenzhydrylphenyl group, have been prepared and fully characterized. The molecular structures of Ni1, Ni2, Ni3 and Ni5 reveal distorted tetrahedral geometries with different degrees of steric protection imparted by the two inequivalent N-aryl groups. On activation with either EASC or MMAO, all the precatalysts are highly active (up to 17.

From polyethylene waxes to HDPE using an α,α'-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl-chromium(iii) chloride pre-catalyst in ethylene polymerisation.

Five examples of α,α'-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl-chromium(iii) chlorides (aryl = 2,6-MePh Cr1, 2,6-EtPh Cr2, 2,6-i-PrPh Cr3, 2,4,6-MePh Cr4, 2,6-Et-4-MePh Cr5) have been synthesized by the one-pot template reaction of α,α'-dioxo-2,3:5,6-bis(pentamethylene)pyridine, CrCl·6HO and the corresponding aniline. The molecular structures of Cr1 and Cr4 reveal distorted octahedral geometries with the N,N,N-ligand adopting a mer-configuration. On activation with an aluminium alkyl co-catalyst, Cr1-Cr5 exhibited high catalytic activities in ethylene polymerization and showed outstanding thermal stability operating effectively at 80 °C with activities up to 1.

Crystal structure of (aceto-nitrile-κ)iodido-(2-(naphthalen-1-yl)-6-{1-[(2,4,6-tri-methyl-phen-yl)imino]ethyl}-pyridine-κ,')copper(I).

In the mononuclear title complex, [CuI(CHN)(CHN)], the Cu ion has a distorted tetra-hedral coordination environment, defined by two N atoms of the chelating 2-(naphthalen-1-yl)-6-[(2,4,6-tri-methyl-phen-yl)imino]-pyridine ligand, one N atom of an aceto-nitrile ligand and one iodide ligand. Within the complex, there are weak intra-molecular C-H⋯N hydrogen bonds, while weak inter-molecular C-H⋯I inter-actions between complex mol-ecules, help to facilitate a three-dimensional network.

Raising the N-aryl fluoride content in unsymmetrical diaryliminoacenaphthylenes as a route to highly active nickel(ii) catalysts in ethylene polymerization.

Five examples of selectively fluorinated unsymmetrical diiminoacenaphthylenes, 1-[2,6-{(4-FCH)CH}-4-FCHN]-2-(ArN) CCH (Ar = 2,6-MeCHL1, 2,6-EtCHL2, 2,6-iPrCHL3, 2,4,6-MeCHL4, 2,6-Et-4-MeCHL5), have been synthesized and used to prepare their corresponding nickel(ii) halide complexes, LNiBr (Ni1-Ni5) and LNiCl (Ni6-Ni10). Both H and F NMR spectroscopy techniques have been employed to characterize paramagnetic Ni1-Ni10; an inequivalent fluorine environment is a feature of the tetrahedral complexes in solution. Upon activation with relatively low ratios (ca.

Correction: Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru-porphyrin mediated amination reaction.

Correction for 'Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru-porphyrin mediated amination reaction' by Paolo Zardi et al., Analyst, 2016, 141, 3050-3058.