Synthesis, characterization and reactivity of tetramethylphospholyl complexes of scandium

Reaction of 2 equiv. of (C₄Me₄P)Li(tmeda) (tmeda = tetraethylenediamine) with 1 equiv. of ScCl₃(THF)₃ gave the new compound (η⁵-C₄Me₄P)₂ScCl₂Li(tmeda) (1), which was characterized by X-ray crystallography. A phospholyl moiety in 1 is labile, as demonstrated by reactions of 1 with LiCH(SiMe₃)₂ and Cp^∗Li (Cp^∗ = C₅Me₅) to afford, respectively, (η⁵-Me₄C₄P)Sc[CH(SiMe₃)₂]Cl₂Li(tmeda) (4) and (η⁵-Me₄C₄P)Cp^∗ScCl₂Li(tmeda) (5). Attempts to generate alkyl derivatives of the general type (η⁵-C₄Me₄P)₂ScR (R = alkyl) were unsuccessful.     

Synthesis,characterization and reactivity of some rhenium phosphite complexes

The preparation and characterization of some Re(III), Re(IV) and Re(V) chloro phosphite complexes are reported. Both Re(III) and Re(IV) complexes react with sodium borohydride, yielding the corresponding polyhydrides, ReH₅[P(OEt)₃]₃ and ReH₇[P(OEt)₃]₂. The thermal and photochemical reactivity of these complexes is described.     

Synthesis, characterization and reactivity of tribenzylphosphine rhodium and iridium complexes

New rhodium and iridium complexes, with the formula [MCl(PBz₃)(cod)] [M = Rh (1), Ir (2)] and [M(PBz₃)₂(cod)]PF₆ [M = Rh (3), Ir (4)] (cod = 1,5-cyclooctadiene), stabilized by the tribenzylphosphine ligand (PBz₃) were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The addition of pyridine to a methanol solution of 1or 2, followed by metathetical reaction with NH₄PF₆, gave the corresponding derivatives [M(py)(PBz₃)(cod)]PF₆ [M = Rh (5), Ir (6)]. At room temperature in CHCl₃ solution, 4 converted spontaneously to the ortho-metallated complex [IrH(PBz₃)(cod){η²-P,C-(C₆H₄CH₂)PBz₂}]PF₆ (7) as a mixture of cis/trans isomers via intramolecular C-H activation of a benzylic phenyl ring. The reaction of 3 or 4 with hydrogen in coordinating solvents gave the dihydrido bis(solvento) derivative [M(H)₂(S)₂(PBz₃)₂]PF₆ (M = Rh, Ir; S = acetone, acetonitrile, THF), that transformed into the corresponding dicarbonyls [M(H)₂(CO)₂(PBz₃)₂]PF₆ by treatment with CO. Analogous cis-dihydrido complexes [M(H)₂(THF)₂(py)(PBz₃)₂]PF₆ (M = Rh, Ir) were observed by reaction of the py derivatives 5 and 6 with H₂.     

Synthesis,characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes

Thiolate-bridged hetero-bimetallic complexes [Cp*M（Me CN）N₂S₂Fe Cl][PF₆]（2, M = Ru; 3, M = Co, Cp*= η⁵-C₅Me₅, N₂S₂= N,N’-dimethyl-3,6-diazanonane-1,8-dithiolate） were prepared by self-assembly of dimer [N₂S₂Fe]₂ with mononuclear precursor [Cp*Ru（MeCN）₃][PF₆] or [Cp*Co（Me CN）₃][PF₆]₂ in the presence of CHCl₃ as a...     

Synthesis, characterization and ethylene reactivity of 2-diphenylphosphanylbenzamido nickel complexes

Addition of primary amines to N-[2-(diphenylphosphanyl)benzoyloxy]succinimide affords 2-diphenylphosphanylbenzamides, Ph2PC6H4C(O)NHR (R = C(CH3)3, 3; R = H, 4; R = CH2CH2CH3, 5; R = CH(CH3)2, 6). Addition of NiCl(eta3-CH2C6H5)(PMe3) to the deprotonated potassium salts of the amides and subsequent treatment of two equivalents of B(C6F5)3 to the resulting products furnishes eta3-benzyl zwitterionic nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta3-CH2C6H5) (R = C6H5, 9; R = C(CH3)3, 10; R = H, 11; R = CH2CH2CH3, 12; R = CH(CH3)2, 13). Solid structures of 9, 11, 13 and the intermediate eta1-benzyl nickel(II) complexes, [Ph2PC6H4C(O)NR-kappa2N,P]Ni(eta1-CH2C6H5)(PMe3) (R = C6H5, 7; R = C(CH3)3, 8) were determined by X-ray crystallography. When ethylene is added to the eta3-benzyl zwitterionic nickel(II) complexes, butene is obtained by the complexes 9-12 but complex 13 provides very high molecular-weight branched polyethylene (Mw, approximately 1300000) with excellent activity (up to 5200 kg mol-1 h-1 at 100 psi gauge).     

Synthesis and dehydrocoupling reactivity of iron and ruthenium phosphine-borane complexes

The Fe and Ru phosphine-borane complexes CpM(CO)2PPh2 x BH3 (1, M = Fe, 4, M = Ru) were synthesized utilizing the reaction of the phosphine-borane anion Li[PPh2 x BH3] with the iodo complexes CpM(CO)2I. The Fe complex 1 reacted with PMe3 to yield CpFe(CO)(PMe3)(PPh2 x BH3) (2) and CpFe(PMe3)2(PPh2 x BH3) (3) whereas the Ru species 4 gave only CpRu(CO)(PMe3)(PPh2 x BH3) (5). The complexes 1-5 were characterized by 1H, 11B, 13C and 31P NMR spectroscopy, MS, IR and X-ray crystallography for 1 to 4, and EA for 1, 2 and 4. The reactivity of 1 and 4 towards PPh2H x BH3 was explored. Although no stoichiometric reactions were detected under mild conditions, both 1 and 4 were found to function as dehydrocoupling catalysts to afford Ph2PH x BH2 x PPh2 x BH3 in the melt at elevated temperature (120 degrees C). The carbonyl Fe2(CO)9 also functioned as a dehydrocoupling catalyst under similar conditions. Complex 1 and Fe2(CO)9 represent the first reported active Fe complexes for the catalytic dehydrocoupling of phosphine-borane adducts.     

Salen-iron complexes: Synthesis,characterization and their reactivity with lactide

Schiff-base metal complexes as efficient catalysts are widely used in ring-opening polymerization of cycle esters.The salen Fe complexes were formed with their excellent biocompatibility and less toxicity.A series of salen Fe complexes were designed in this work in order to study the activity and control of polymerization of lactide.The salen Fe complexes' activities changed with the ligands configuration and substituent groups.     

Synthesis and reactivity of cyclopentadienyl iron complexes containing ferrocenyl selenolates

New homo-trimetallic complexes of general formula?1,1??-fc[SeFeCp(CO)₂]₂ (fc?=?Fe(??⁵-C₅H₄)₂) are accessible in high yield by the reaction of 1,1??-fc(SeLi)₂, which is generated from 1,1??-fc(SeSiMe₃)₂ and n-BuLi, with two equivalents of CpFe(CO)₂I. Photolytic CO-substitution reactions of the organoiron diselenolate with bis-phosphines at ?50?°C using 1:2 (metal/ligand) molar ratio afforded 1,1??-fc(SeFeCp(P^P)₂. All these complexes were characterized by physicochemical and spectroscopic methods.     

Chiral cis-iron(ii) complexes with metal- and ligand-centered chirality for highly regio- and enantioselective alkylation of N-heteroaromatics

Iron-catalyzed highly regio- and enantioselective organic transformations with generality and broad substrate scope have profound applications in modern synthetic chemistry; an example is herein described based on cis-Fe^II complexes having metal- and ligand-centered chirality. The cis-β Fe^II(N₄) complex [Fe^II(L)(OTf)₂] (L = N,N′-bis(2,3-dihydro-1H-cyclopenta-[b]quinoline-5-yl)-N,N′-dimethylcyclohexane-1,2-diamine) is an effective chiral catalyst for highly regio- and enantioselective alkylation of N-heteroaromatics with α,β-unsaturated 2-acyl imidazoles, including asymmetric N1, C2, C3 alkylations of a broad range of indoles (34 examples) and alkylation of pyrroles and anilines (14 examples), all with high product yields (up to 98%), high enantioselectivity (up to >99% ee) and high regioselectivity. DFT calculations revealed that the “chiral-at-metal” cis-β configuration of the iron complex and a secondary π–π interaction are responsible for the high enantioselectivity.

A cis-β Fe^II complex having metal- and ligand-centered chirality catalyzes highly regio- and enantioselective alkylation of indoles (at the N1, C2, or C3 position), pyrroles and anilines with α,β-unsaturated 2-acyl imidazoles (48 examples, up to 99% ee).     

Synthesis, characterization and spectral properties of substituted tetraphenylporphyrin iron chloride complexes

A series of substituted tetraphenylporphyrin iron chloride complexes [RTPPFe(III)Cl, R=o/p-NO?, o/p-Cl, H, o/p-CH?, o/p-OCH?] were synthesized by a novel universal mixed-solvent method and the spectral properties of free base porphyrins and iron porphyrin compounds were compared with each other. The experimental results showed that the one-pot mixed solvent method was superior to the two-step method in the yields, reaction time and workup of reaction mixtures for the synthesis of iron porphyrin compounds. The highest yields (28.7%-40.4%) of RTPPFe(III)Cl were obtained in the mixed solvents propionic acid, glacial acetic acid and m-nitrotoluene under reflux for 2 h. A detailed analysis of ultraviolet-visible (UV-vis), infrared (IR) and far-infrared (FIR) spectra suggested the transformation from free base porphyrins to iron porphyrins. The red shift of the Soret band in ultraviolet-visible spectra due to the presence of p-nitrophenyl substituents and the blue shift of Fe-Cl bond of TPPFeCl in far-infrared spectra were further explained by the electron transfer and molecular planarity in the porphyrin ring.     

Synthesis and characterization of zinc complexes and reactivity with primary phosphines

Zinc complexes of chelating monoanionic N-donors and neutral diphosphine ligands were synthesized by reaction of diethylzinc with 1,3-diketimine, diazabutadiene, and diphosphine ligand precursors. These complexes were reacted with primary phosphines in an attempt to solicit phosphine dehydrocoupling reactivity. In most cases, insoluble zinc-containing precipitates were formed and ligands were liberated. For the most sterically encumbered complex, (^DippL)ZnEt (3, ^DippL = [(2,6-ⁱPrC₆H₃)NC(CH₃)]₂CH^?), a product assigned as the zinc-phosphide (^DippL)ZnPHPh (6) was observed but could not be isolated as a pure compound. A new, less bulky β-diketiminate complex (^TolL)ZnEt (2, ^TolL = [(p-CH₃C₆H₄)NC(CH₃)]₂CH^?) was reacted with primary phosphines to give a precipitate and the bis(β-diketiminate)zinc complex (^TolL)₂Zn (5), an apparent product of comproportionation. (^MesAI)ZnEt (1, ^MesAI = MesNC(Me)(Et)C(Me) = NMes) and 2 were structurally characterized.     

Synthesis and characterization of zinc complexes and reactivity with primary phosphines

Zinc complexes of chelating monoanionic N-donors and neutral diphosphine ligands were synthesized by reaction of diethylzinc with 1,3-diketimine, diazabutadiene, and diphosphine ligand precursors. These complexes were reacted with primary phosphines in an attempt to solicit phosphine dehydrocoupling reactivity. In most cases, insoluble zinc-containing precipitates were formed and ligands were liberated. For the most sterically encumbered complex, (^DippL)ZnEt (3, ^DippL = [(2,6-ⁱPrC₆H₃)NC(CH₃)]₂CH⁻), a product assigned as the zinc-phosphide (^DippL)ZnPHPh (6) was observed but could not be isolated as a pure compound. A new, less bulky β-diketiminate complex (^TolL)ZnEt (2, ^TolL = [(p-CH₃C₆H₄)NC(CH₃)]₂CH⁻) was reacted with primary phosphines to give a precipitate and the bis(β-diketiminate)zinc complex (^TolL)₂Zn (5), an apparent product of comproportionation. (^MesAI)ZnEt (1, ^MesAI = MesNC(Me)(Et)C(Me) = NMes) and 2 were structurally characterized.     

Ketiminate supported aluminum(III) complexes: Synthesis, characterization and reactivity

The reaction of LLi, (L = [RNC(Me)CHC(Me) = O] (R = C₂H₄NEt₂)), with AlCl₃ at −78 °C forms the mono-ketiminate product, LAlCl₂, 1, while the same reaction at 0 °C affords the bis-ketiminate complex, [{(LH)₂AlCl}(Cl₂)], 2, Reduction of 1 with Li^o, K^o or Mg^o yielded an unusual dimeric aluminum(III) species, [L′AlCl]₂, 3, where C-C coupling of the ligand backbone is observed.     

Synthesis, reactivity, and structure of strictly homologous 18 and 19 valence electron iron nitrosyl complexes

The 18 and 19 valence electron (VE) nitrosyl complexes [Fe(NO)('pyS4')]BF4 ([1]BF4) and [Fe(NO)('pyS4')] (2) have been synthesized from [Fe('pyS4')]x ('pyS4'(2-) = 2,6-bis(2-mercaptophenylthiomethyl)pyridine(2-)) and either NOBF4 or NO gas. Complex [1]BF4 was also obtained from [Fe(CO)('pyS4')] and NOBF4. The cation [1]+ is reversibly reduced to give 2. Oxidation of 2 by [Cp2Fe]PF6 afforded [Fe(NO)('pyS4')]PF6 ([1]PF6). The molecular structures of [1]PF6 and 2 were determined by X-ray crystallography. They demonstrate that addition of one electron to [1]+ causes a significant elongation of the Fe-donor atom bonds and a bending of the FeNO angle. Density functional calculations show that the unpaired electron in 2 occupies an orbital, which is antibonding with respect to all Fe-ligand interactions. As expected from qualitative Molecular Orbital (MO) theory, it has a large contribution from a pi* type NO orbital. The nu(NO) frequency decreases from 1893 cm(-1) in [1]BF4 to 1648 cm(-1) in 2 (in KBr). The antibonding character of the unpaired electron explains the ready reaction of 2 with excess NO to give [Fe(NO)2('pyS4')] (3), the facile NO/CO exchange of 2 to afford [Fe(CO)('pyS4')], and the easy oxidation of 2 to [1]+.     

Synthesis,characterization and C–H amination reactivity of nickel iminyl complexes

Metalation of the deprotonated dipyrrin (^AdFL)Li with NiCl₂(py)₂ afforded the divalent Ni product (^AdFL)NiCl(py)₂ (1) (^AdFL: 1,9-di(1-adamantyl)-5-perfluorophenyldipyrrin; py: pyridine). To generate a reactive synthon on which to explore oxidative group transfer, we used potassium graphite to reduce 1, affording the monovalent Ni synthon (^AdFL)Ni(py) (2) and concomitant production of a stoichiometric equivalent of KCl and pyridine. Slow addition of mesityl- or 1-adamantylazide in benzene to 2 afforded the oxidized Ni complexes (^AdFL)Ni(NMes) (3) and (^AdFL)Ni(NAd) (4), respectively. Both 3 and 4 were characterized by multinuclear NMR, EPR, magnetometry, single-crystal X-ray crystallography, theoretical calculations, and X-ray absorption spectroscopies to provide a detailed electronic structure picture of the nitrenoid adducts. X-ray absorption near edge spectroscopy (XANES) on the Ni reveals higher energy Ni 1s → 3d transitions (3: 8333.2 eV; 4: 8333.4 eV) than Ni^I or unambiguous Ni^II analogues. N K-edge X-ray absorption spectroscopy performed on 3 and 4 reveals a common low-energy absorption present only for 3 and 4 (395.4 eV) that was assigned via TDDFT as an N 1s promotion into a predominantly N-localized, singly occupied orbital, akin to metal-supported iminyl complexes reported for iron. On the continuum of imido (i.e., NR²⁻) to iminyl (i.e., ²NR⁻) formulations, the complexes are best described as Ni^II-bound iminyl species given the N K-edge and TDDFT results. Given the open-shell configuration (S = 1/2) of the iminyl adducts, we then examined their propensity to undergo nitrenoid-group transfer to organic substrates. The adamantyl complex 4 readily consumes 1,4-cyclohexadiene (CHD) via H-atom abstraction to afford the amide (^AdFL)Ni(NHAd) (5), whereas no reaction was observed upon treatment of the mesityl variant 3 with excess amount of CHD over 3 hours. Toluene can be functionalized by 4 at room temperature, exclusively affording the N-1-adamantyl-benzylidene (6). Slow addition of the organoazide substrate (4-azidobutyl)benzene (7) with 2 exclusively forms 4-phenylbutanenitrile (8) as opposed to an intramolecular cyclized pyrrolidine, resulting from facile β-H elimination outcompeting H-atom abstraction from the benzylic position, followed by rapid H₂-elimination from the intermediate Ni hydride ketimide intermediate.

Nickel-supported nitrenoids exhibit iminyl character, as determined by multi-edge XAS and TDDFT analysis, demonstrate efficacy for C–H activation and nitrene transfer chemistry.     

Synthesis, characterization and dioxygen reactivity of copper(I) complexes with glycoligands

A new family of copper(I) complexes with "glycoligands" containing a central saccharide scaffold, with 2-picolyl ether groups or 2-picolylamine or N-imidazolylamine groups, has been prepared and characterized. For this purpose, the following tetradentate ligands have been synthesized: methyl 2,3-di-O-(2-picolyl)-alpha-D-lyxofuranoside (L1), 1,5-anhydro-2-deoxy-3,4-di-O-(2-picolyl)-d-galactitol (L2), 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(2-picolyl)-alpha-D-xylofuranose (L3), and 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(methylimidazol-2-yl)-alpha-D-xylofuranose (L4). The ligands and the complexes were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies, ESI mass spectrometry, and cyclic voltammetry. Collaterally with the experimental work, HF-DFT(B3LYP/6-31G*) computations were performed to obtain additional structural information. The Cu(I) complexes are found to be pentacoordinated. The redox properties and the O2-reactivity of the Cu(I)Ln complexes have been studied. Reactions of Cu(I) complexes with dioxygen in ethanol yield stable Cu(II) complexes as confirmed by UV-visible spectrophotometry and EPR spectroscopy.     

Synthesis and structural characterization of new phosphinooxazoline complexes of iron

The first phosphinooxazoline chelate complexes of iron were synthesized, and their structural and electronic properties were studied.The known phosphinooxazolines 2-(2-(diphenylphosphino)phenyl)-4,5-dihydrooxazole (7a), 2-(2-(diphenylphosphino)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (7b), (S)-4-benzyl-2-(2-(diphenylphosphino)phenyl)-4,5-dihydrooxazole (7e) and (R)-2-(2-(diphenylphosphino)phenyl)-4-phenyl-4,5-dihydrooxazole (7f) were synthesized by a modified three step literature procedure with improved 67-60% overall yields. The new electronically tuned phosphinooxazolines 2-(5-bromo-2-(diphenylphosphino)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (7c), 3-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-4-(diphenylphosphino)-N,N-dimethylaniline (7d) and 2-(2-(diphenylphosphino)-3-(trifluoromethyl)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (7g) were synthesized in three to six steps with 59-29% overall yields. Reaction of 7a-f with CpFe(CO)₂I (110 °C, 2 h, toluene) gave the iodide salts of the new iron phosphinooxazoline complexes [CpFe(CO)(7a-f)]⁺ in 87-21% yield. The new complexes were characterized by X-ray and the molecular structures confirm the octahedral coordination geometry and the half-sandwich structure about the iron center. The impact of different oxazoline ligands on the steric and electronic properties of their iron complexes was determined by analysis of selected bond lengths, ν_CO stretching frequency and the oxidation potentials of the ligands and the iron complexes.     

Synthesis, characterization, and reactivity of rhodium(I) acetylacetonato complexes containing pyridinecarboxaldimine ligands

Addition of o-C 6H 4NCHNAr to Rh(coe) 2(acac) (coe = cis-cyclooctene, acac = acetylacetonato) gave several new iminopyridine rhodium(I) complexes of the type Rh(acac)(kappa (2)- o-C 6H 4 NCH NAr) ( 1a Ar = 4-C 6H 4-OMe; 1b Ar = 2,6-C 6H 3-Me 2; 1c Ar = 2,6-C 6H 3-Et 2; 1d Ar = 2,6-C 6H 3- i-Pr 2). All new rhodium complexes have been characterized by a number of physical methods, including multinuclear NMR spectroscopy and X-ray diffraction studies for 1b and 1c. Addition of CHCl 3 to 1a afforded the corresponding rhodium(III) complex trans-Rh(kappa (2)- o-C 6H 4 NCH NAr)(CHCl 2)(Cl)(acac) ( 2). Addition of B 2cat 3 (cat = 1,2-O 2C 6H 4) to 1 gave zwitterionic Rh(eta (6)-catBcat)(kappa (2)- o-C 6H 4 NCH NAr) ( 3). The molecular structure of 3b has been confirmed by a single crystal X-ray diffraction study and shows that the N 2Rh fragment is bound to the catBcat anion via one of the catecholato groups in a eta (6)-fashion. These complexes have also been examined for their ability to catalyze the hydroboration of a series of vinylarenes. Reactions using catecholborane and pinacolborane seem to proceed largely through a dehydrogenative borylation mechanism to give a number of boronated products.     

Synthesis, characterization and reactivity of heteroleptic rare earth metal bis(phenolate) complexes

The synthesis, characterization and reactivity of heteroleptic rare earth metal complexes supported by the carbon-bridged bis(phenolate) ligand 2,2'-methylene-bis(6-tert-butyl-4-methyl-phenoxo) (MBMP(2-)) are described. Reaction of (C(5)H(5))(3)Ln(THF) with MBMPH(2) in a 1 : 1.5 molar ratio in THF at 50 degrees C produced the heteroleptic rare earth metal bis(phenolate) complexes (C(5)H(5))Ln(MBMP)(THF)(n) (Ln = La, n = 3 (); Ln = Yb (), Y (), n = 2) in nearly quantitative yields. The residual C(5)H(5)(-) groups in complexes to can be substituted by the bridged bis(phenolate) ligands at elevated temperature to give the neutral rare earth metal bis(phenolate) complexes, and the ionic radii have a profound effect on the structures of the final products. Complex reacted with MBMPH(2) in a 1 : 0.5 molar ratio in toluene at 80 degrees C to produce a dinuclear complex (MBMP)La(THF)(mu-MBMP)(2)La(THF)(2) () in good isolated yield; whereas complexes and reacted with MBMPH(2) under the same conditions to give (MBMP)Ln(MBMPH)(THF)(2) (Ln = Yb (), Y ()) as the final products, in which one hydroxyl group of the phenol is coordinated to the rare earth metal in a neutral fashion. The reactivity of complexes and with some metal alkyls was explored. Reaction of complex with 1 equiv. of AlEt(3) in toluene at room temperature afforded unexpected ligand redistributed products, and a discrete ion pair ytterbium complex [(MBMP)Yb(THF)(2)(DME)][(MBMP)(2)Yb(THF)(2)] () was isolated in moderate yield. Furthermore, reaction of complex with 1 equiv. of ZnEt(2) in toluene gave a ligand redistributed complex [(mu-MBMP)Zn(THF)](2) () in reasonable isolated yield. Similar reaction of complex with ZnEt(2) also afforded complex ; whereas the reaction of complex with 1 equiv. of n-BuLi in THF afforded the heterodimetallic complex [(THF)Yb(MBMP)(2)Li(THF)(2)] (). All of these complexes were well characterized by elemental analyses, IR spectra, and single-crystal structure determination, in the cases of complexes , and -.