Structures Of Complexes 4a Research Articles

C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion

Abstract C–S bond cleavage in pyridylmethylthioether systems promoted by oxorhenium(V) ion has been established performing the reaction of 1,2-bis(2-pyridylmethylthio)ethane(BPT1), 1,3-bis(2-pyridyl-methylthio)propane(BPT2) and 3,4-bis(2-pyridylmethylthio)-5-methyltoluene (BPT3) with Bu4N[ReOCl4] in dry alcoholoic medium. In case of BPT1 and BPT2, new 2-(2-pyridylmethylthio)ethane-1-thiol (L1H) and 3-(2-pyridylmethylthio)propane-1-thiol (L2H) ligand, respectively were formed in situ through cleavage of one C–S(thioether) bond, resulting in the neutral oxorhenium(V) complexes of formulation [ReO(L1)Cl2] (1a) and [ReO(L2)Cl2] (1b); where as in case of BPT3, binary oxorhenium(V) complex of 3,4-dimercapto-toluene ligand (L3H2), formulated as Bu4N[ReO(L3)2] (1c) through cleavage of two C–S(thioether) bonds. The presence of picolinic acid, as by-product in the filtrates of the C–S bond cleavage reactions in dry alcohol, was detected by treatment of copper(II) salts and GC–MS techniques. But in hydrated alcoholic medium no C–S bond cleavage induced by ReO(V) ion occurred in any of the BPT systems rather the conversion of ReO(V) into perrhenate salt was observed; this reaction mixture, in turn on reaction with copper(II) nitrate trihydrate salt, produce [Cu(BPT)Cl]ReO4 (2) type complexes. The solid-state structures of complexes 1a and 2a were established by X-ray crystallography.

Synthesis of Mixed Cp/TpMe2 Lanthanide Complexes from Lanthanocene Precursors and their Structures and Reactivities

Reaction of Cp(2)LnCl with 1 equiv of KTp(Me2) in toluene gives the mixed Tp(Me2)/Cp lanthanide complexes Cp(2)Ln(Tp(Me2)) (Ln = Yb (1a), Er (1b), Dy (1c)), while unexpected complexes CpLn(Tp(Me2))Cl(THF) (Ln = Yb (2a), Er (2b.THF), Dy (2c), Y (2d)) are obtained when the reactions are carried out in THF. Complex 2b can also be formed by the reaction of CpErCl(2)(THF)(3) with 1 equiv of KTp(Me2) in THF. Moreover, complex 1a can also be obtained from the reaction of Cp(3)Yb and KTp(Me2). The results not only represent an efficient and versatile method for the synthesis of mixed Cp/Tp(Me2) lanthanide complexes but also provide new insight into the reactivity of Cp(2)LnCl. Furthermore, the reactivities of complexes 1a-c toward proton-donating reagents are examined. It has been found that 1b reacts with benzotriazole (C(6)H(4)NHN(2)) in THF to yield a lanthanide metallomacrocyclic complex [(Tp(Me2))CpEr(mu-N(3)C(6)H(4))](3) (3), while the reaction of 1a with 1 equiv of 2-aminopyridine in THF gives an unexpected oxide complex [(Tp(Me2))Yb(2-HNC(5)H(4)N)](2)(mu-O) (4). Presumably, the oxide ligand of compound 4 results from adventitious water. In addition, treatment of 1c with 2 equiv of 3,5-dimethylpyrazole yields a completely Cp-abstracted product (Tp(Me2))Dy(Pz(Me2))(2)(THF) (5), which can also be directly obtained from a three-component reaction of Cp(2)DyCl, KTp(Me2), and 3,5-dimethylpyrazole in THF. These results further indicate that the new mixed Tp(Me2)/Cp lanthanide complexes are practical and versatile precursors for the synthesis of poly(pyrazolyl)borate lanthanide derivatives. All new compounds have been characterized by elemental analysis and spectroscopic methods. The structures of complexes 1a,b and 2-5 have also been determined through single-crystal X-ray diffraction analysis.

Synthesis and characterization of lithium, aluminium and zinc complexes supported by pyrazolyl-based N,N′-chelate ligands

A series of lithium, aluminium and zinc complexes bearing [3,5-R2C3HN2CHC(R1)N(R2)]− ligands were synthesized and characterized. Treatment of 1-(Me3SiCH2)-3,5-R2C3HN2 (R = Me, But) with LiBun and then ButCN afforded [Li{N(SiMe3)C(But)CHN2C3HR2-3,5}]2 (R = Me, 2a; R = But, 2b). Reaction of both 2a and 2b with ZnCl2 gave zinc complexes [Zn(Cl){N(SiMe3)C(But)CHN2C3HR2-3,5}]2 (R = Me, 3a; R = But, 3b). Treatment of o-RC6H4NHC(Ph)CHN2C3HMe2-3,5 (R = OPri, 5a; R = Me, 5b) with LiBun yielded lithium complexes similar to 2a or 2b, [Li{N(o-RC6H4)C(Ph)CHN2C3HMe2-3,5}] (R = OPri, 6a; R = Me, 6b). Reaction of 6b with ZnCl2 generated zinc complexes [Zn(Cl){N(o-MeC6H4)C(Ph)CHN2C3HMe2-3,5}] (7), and with AlCl3 gave [Al(Cl2){N(o-MeC6H4)C(Ph)CHN2C3HMe2-3,5}] (8). Reaction of 5a with ZnEt2 produced [Zn{N(o-PriC6H4)C(Ph)CHN2C3HMe2-3,5}2] (9). Reaction of 5a and 5b with AlR′3 (R′ = Me, Et) afforded aluminium complexes [Al(R′2){N(o-RC6H4)C(Ph)CHN2C3HMe2-3,5}] (R = OPri, R′ = Me, 10a; R=Me, R′ = Me, 10b; R = OPri, R′ = Et, 10c; R = Me, R′ = Et, 10d). A trace of species [Al(Et2){N(o-MeC6H4)C(Ph)(Et)CH2N2C3HMe2-3,5}] (11) was also isolated from the reaction products of 5b and AlEt3. All of new compounds were characterized by 1H and 13C NMR spectroscopy and elemental analyses. Structures of complexes 2a, 8, 10a, 10d and 11 were additionally characterized by single-crystal X-ray diffraction techniques.

Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R 2C 3N 2)C 6H 4NH 2 (R = Me, Ph) with salicylaldehyde or 3,5-di- tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a– 2d. Treatment of 2a– 2d with an equiv. of AlR 2 3 (R 2 = Me, Et) gave corresponding aluminum aryloxides 3a– 3e, while reaction with an equiv. of ZnEt 2 afforded zinc aryloxides 4a– 4d. Treatment of 2c with 0.5 equiv. of ZnEt 2 formed diphenolato zinc complex 5. All new compounds were characterized by 1H and 13C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3– 5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes ( 4a– 4d) exhibited higher catalytic activity than the aluminum complexes ( 3a– 3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a– 4d. The aluminum complex ( 3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex ( 4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.

Copper 5-sulfoisophthalato quasi-planar squares in coordination polymers modulated by alkaline-earth metals: a way to molecular squares?

Two copper-sip coordination polymers (sip3− = 5-sulfoisophthalic anion), [Ca(H2O)3Cu2(H2O)6(sip)2]·2H2O 2a, and [Sr(H2O)4Cu2(H2O)6(sip)2]·H2O 2b, have been synthesized at room temperature. Single-crystal X-ray diffraction reveals that the structures of complexes 2a and 2b are 2-D coordination layer structures, containing [Cu4(sip)4] molecular squares linked by calcium (2a) or strontium (2b) bridges. The coordination layers display 3,6-connected topologies if the [Cu4(sip)4] molecular squares and alkaline-earth metals are considered as nodes, or (4,4) nets if alkaline-earth metals are considered to be part of the [Cu4(sip)4] squares. In comparison with the more commonly encountered Cu-sip zigzag chain subunits in copper-sip coordination polymers, the [Cu4(sip)4] square subunits in 2a and 2b represent similar coordination fashions and connecting modes while creating singular examples of new subunits in coordination complexes of the copper-sip system. Variable temperature magnetic susceptibility of 2a indicated that antiferromagnetic interactions dominate between the Cu(II) ions bridged by sip3− ligands.

Ruthenium-Stabilized Low-Coordinate Phosphorus Atoms. p-Cymene Ligand as Reactivity Switch

A detailed comparative study of the structural and spectroscopic features and of the reactivity of ruthenium phosphinidene complexes (η6-Ar)(PCy3)Ru(PMes*) (2a, Ar = p-cymene; 2b, Ar = benzene) has been undertaken. The structures of complexes 2a and 2b have been determined by single-crystal X-ray diffraction and display similar features. Both compounds possess identical chemical behavior toward Brönsted acids such as HBF4: protonation of the phosphinidene ligand yields the new cationic complexes [(η6-Ar)(PCy3)Ru(PHMes*)]BF4 (3aBF4, Ar = p-cymene; 3bBF4, Ar = benzene), which exhibit an unprecedented phosphenium-bearing hydrogen substituent. 3aBF4 has been characterized using X-ray diffraction techniques. The lone pair of the phosphorus atom of the phosphinidene ligand remains also accessible to the Lewis acid BH3: the reactions of 2a and 2b with borane give the adducts (η6-Ar)(PCy3)Ru[P(BH3)Mes*] (4a, Ar = p-cymene; 4b, Ar = benzene). In the presence of the larger borane BPh3, no reaction occurs until water is introduced in the reaction vessel. This results in the generation of [(η6-Ar)(PCy3)Ru(PHMes*)]BPh3OH (3aBPh3OH, Ar = p-cymene; 3bBPh3OH, Ar = benzene) presumably through protonation of 2a and 2b by the previously unknown adduct H2O·BPh3. Phosphinidene complexes react also with electrophilic alkylating reagents such as organic iodides provided the alkyl substituent is small. Treatment of 2a and 2b with 1 equiv of methyliodide leads to the alkylation at the phosphinidene center and yields the phosphenium complexes [(η6-Ar)(PCy3)Ru(PMeMes*)]I (5a, Ar = p-cymene; 5b, Ar = benzene). Examination of the reactivity toward electron-rich reagents such as the alkynes RCCH (R = Me3Si, Ph) yields unexpected results: 2a instantaneously reacts to generate phosphaindane complexes 6 and 7, whereas no reaction occurs when using 2b. A detailed kinetic study provides evidence for a dissociative mechanism involving the release of the phosphine ligand in 2a and explains its specificity. The p-cymene ligand in 2a acts as a reactivity switch due to the higher steric hindrance of this arene.

Selective Reaction Based on the Linked Diamido Ligands of Dinuclear Lanthanide Complexes

The dinuclear ytterbium pyridyl diamido complexes [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,6)] (1a) and [Cp(2)Yb(THF)](2)[mu-eta(1):eta(2)-(NH)(2)(C(5)H(3)N-2,3)] (1b) are easily prepared by protonolysis of Cp(3)Yb with 0.5 equiv of the corresponding diaminopyridine in accepted yields, respectively. Treatment of 1a with 2 equiv of dicyclohexylcarbodiimide (CyN=C=NCy) in THF at low temperature leads to the isolation of the formal double N-H addition product (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyN(CyNH)CN)(2)(C(5)H(3)N-2,6)] (2) in 42% yield. Compound 2 is unstable to heat and slowly isomerized to the mixed neutral/dianionic diguanidinate complex (Cp(2)Yb)(2)[mu-eta(2):eta(2)-(CyNH)(2)CN(C(5)H(3)N-2,6)NC(NCy)(2)](THF) (3) at room temperature. Similarly, treatment of 1b with 2 equiv of CyN=C=NCy gives the addition/ isomerization product (Cp(2)Yb)(2)[mu-eta(2):eta(2):eta(1)-(CyNH)(2)CN(C(5)H(3)N-2,3)NC(NCy)(2)] (4). Moreover, the reaction of various ytterbium aryl diamido complexes (prepared in situ from [Cp(2)YbMe](2) and aryldiamine, respectively) with CyN=C=NCy affords the corresponding addition products (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,4)] (5), (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(6)H(4)-1,3)](6), and (Cp(2)Yb)(2)[mu-eta(2):eta(2)-{CyN(CyNH)CN}(2)(C(13)H(8)-2,7)] (7), respectively. In contrast to pyridyl-bridged bis(guanidinate monoanion) complexes, aryl-bridged bis(guanidinate monoanion) complexes 5-7 are stable even with prolonged heating at 110 degrees C. All the results not only demonstrate that the presence of the pyridyl bridge can impart the diamido complexes with a unique reactivity and initiate the unexpected reaction sequence but also indicate evidently that the number and distribution of negative charges of the diguanidinate ligand is tunable from double monoanionic units to mixed neutral/dianionic isomers. All the complexes are characterized by elemental analysis and IR spectroscopies. The structures of complexes 1a, 3, 5, 6, and 7 are also determined through X-ray single-crystal diffraction analysis.

Redox Chemistry in the Reaction of Oxovanadium(V) with Thiolate‐Containing Ligands: the Isolation and Characterization of Non‐Oxo Vanadium(IV) Complexes Containing Disulfide and Thioether Groups

AbstractThe reactions of VVO(O‐iPr)3 with [PS3′]H3 and [PS3]H3 {[PS3′]H3 = P(C6H3‐5‐Me‐2‐SH)3, [PS3]H3 = P(C6H4‐2‐SH)3} led to the formation of [VIV(L)] [L = P2S4′ (1a), P2S4 (1b)], where L was formed by the oxidative coupling of two PS3′ or PS3 ligands by a disulfide bond. When the reaction of VVO(O‐iPr)3 with [PS3′]H3 was conducted in the presence of methoxide followed by the addition of a cation, [VIV(PS3′)(PS2SMe′)]X [X = N(C2H5)4 (2a), N(C2H5)3(CH2Ph) (2b)] was isolated, where PS2SMe′ is a bis(benzenethiolato)phenylmethylthioetherphosphane ligand generated from the methylation of one thiolate group in PS3′. The structures of complexes 1a,b and 2a,b, determined by X‐ray crystallography, contain six‐ and seven‐coordinate non‐oxo vanadium(IV) centers, respectively, with an octahedral geometry for 1a,b and a pentagonal‐bipyramidal geometry for 2a,b. The electronic, magnetic, and electrochemical properties of these complexes were determined by UV/Vis and EPR spectroscopy, SQUID measurements, and cyclic voltammetry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis, characterization and solid state structures of thiosemicarbazone palladacycles: Influence of hydrogen bonding in the molecular arrangement

Treatment of the thiosemicarbazones 4-FC 6H 4C(Me) NN(H)C( S)NHR, (R = Me, a; Ph, b) and 2-ClC 6H 4C(Me) NN(H)C( S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC 6H 3C(Me) NN C(S)NHR}] 4 ( 1a, 1b) and [Pd{2-ClC 6H 3C(Me) NN C(S)NHPh}] 4 ( 1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC 6H 3C(Me) NN C(S)NHR}) 2(μ-Ph 2P(CH 2) n PPh 2)], ( n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC 6H 3C(Me) NN C(S)NHPh}) 2(μ-Ph 2PCH CHPPh 2)], ( 3a, 3b) and [(Pd{2-ClC 6H 3C(Me) NN C(S)NHR}) 2(μ-Ph 2P(CH 2) n PPh 2)], ( n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC 6H 3C(Me) NN C(S)NHPh}) 2(μ-PPh 2CH CHPPh 2)], ( 3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.

Heterometallic (ZrIII)2—Al hydrides [(Cp2Zr)2(µ-H)](µ-H)2AlX2 (X = Cl or Br): preparative synthesis and reactivity. Molecular structure of [(Cp2Zr)2(µ-Cl)](µ-H)2AlCl2

A procedure was developed for the synthesis of trinuclear cyclic (ZrIII)2—Al hydrides [(Cp2Zr)2(µ-H)](µ-H)2AlX2 (X = Cl (1a) or Br (1b)). These complexes were prepared in 60–65% yields by the reaction of Cp2ZrX2 with LiAlH4 in the presence of CoBr2 and tolane. The structures of complexes 1a and 1b and iodide 1c (X = I) were studied by NMR spectroscopy in solvents of different basicities (toluene, THF, and pyridine). Complex 1a is unsolvated and monomeric in all solvents; complex 1b, in toluene and THF; complex 1c, in toluene only. At room temperature, complex 1a does not catalyze hydrogenation of hex-1-ene and does not react with tolane, but reacts with the latter at high temperature to give bis(η5-cyclopentadienyl)-2,3,4,5-tetraphenylzirconacyclopentadiene. The reaction of equivalent amounts of complex 1a and HCl produces the [(Cp2Zr)2(µ-Cl)](µ-H)2AlCl2 complex. The structure of the latter was established by X-ray diffraction.

Synthesis and Characterization of Pyrrolthiosemicarbazone Complexes of Palladium(II). Crystal Structures of [{Pd[C4H4NC(H)=NNC(S)NHMe](Cl)}2{μ-Ph2P(CH2)3PPh2}] and [Pd{C4H4NC(H)=NNC(S)NHMe}{Ph2P(CH2)2PPh2-P,P}](Cl)

Reaction of the thiosemicarbazone ligands C4H4NC(H)=NN(H)C(S)NHR (R = Me, a; Et, b) with Li2[PdCl4] gave the dinuclear complexes [Pd{C4H4NC(H)=NNC(S)NHR}(μ-Cl)]2 (R = Me, 1a; Et, 1b) with a central Pd2Cl2 core and with deprotonation of the thiosemicarbazones at the hydrazinic nitrogen atom. Treatment of 1a and 1b with triphenylphosphine gave the mononuclear compounds [Pd{C4H4C(H)=NNC(S)NHR}(Cl)(PPh3)] (R = Me, 2a; Et, 2b), whereas reaction of 1a and 1b with tertiary diphosphines gave mono- and dinuclear compounds, as appropriate, with the corresponding diphosphine acting as a monodentate (6b), chelating (3a) and bridging ligand (4a, 5a, 4b, 5b). Treatment of 1a and 1b with (Ph2PCH2CH2PPh2)W(CO)5 gave the new heterobimetallic complexes 7a and 7b. The crystal structures of complexes 3a and 4a are described.

Synthesis and characterization of aluminum complexes of 2-pyrazol-1-yl-ethenolate ligands

The synthesis and the characterization of some new aluminum complexes with bidentate 2-pyrazol-1-yl-ethenolate ligands are described. 2-(3,5-Disubstituted pyrazol-1-yl)-1-phenylethanones, 1-PhC(O)CH 2-3,5-R 2C 3HN 2 ( 1a, R = Me; 1b, R = Bu t ), were prepared by solventless reaction of 3,5-dimethyl pyrazole or 3,5-di- tert-butyl pyrazole with PhC(O)CH 2Br. Reaction of 1a or 1b with AlR 3 1 (R 1 = Me, Et) yielded N, O-chelate alkylaluminum complexes [ R 2 1 AlOC ( Ph ) CH { ( 3 , 5 - R 2 C 3 HN 2 ) - 1 } ] ( 2a, R = R 1 = Me; 2b, R = Bu t , R 1 = Me; 2c, R = Me, R 1 = Et). Compound 1a was readily lithiated with LiBu n in thf or toluene to give lithiated species 3. Treatment of 3 with 0.5 equiv of MeAlCl 2 or AlCl 3 yielded five-coordinated aluminum complexes [XAl(OC(Ph)CH{(3,5-Me 2C 3HN 2)-1}) 2] ( 4, X = Me; 5, X = Cl). Reaction of 5 with an equiv of LiHBEt 3 generated [Al(OC(Ph)CH{(3,5-Me 2C 3HN 2)-1}) 3] ( 6). Complex 6 was also obtained by reaction of 3 with 1/3 equiv of AlCl 3. Treatment of 5 with 2 equiv of AlMe 3 yielded complex 2a, whereas with an equiv of AlMe 3 afforded a mixture of 2a and [Me(Cl)AlOC(Ph)CH{(3,5-Me 2C 3HN 2)-1}] ( 7). Compounds 1a, 1b, 2a– 2c and 4– 6 were characterized by elemental analyses, NMR and IR (for 1a and 1b) spectroscopy. The structures of complexes 2a and 5 were determined by single crystal X-ray diffraction techniques. Both 2a and 5 are monomeric in the solid state. The coordination geometries of the aluminum atoms are a distorted tetrahedron for 2a or a distorted trigonal bipyramid for 5.

Synthesis of New Cationic Cp*Ir N-Heterocyclic Carbene Complexes and Their High Catalytic Activities in the Oppenauer-Type Oxidation of Primary and Secondary Alcohols

Several new cationic Cp*Ir N-heterocyclic complexes have been synthesized and their catalytic activities in the Oppenauer-type oxidation have been investigated in order to improve the catalytic activity of [Cp*IrCl(μ-Cl)]2. The reactions of [Cp*IrCl(μ-Cl)]2 (1) with N-heterocyclic carbene ligands afforded Cp*Ir(L)Cl2 (3a−d; L = N-heterocyclic carbene ligands). The cationic complexes [Cp*Ir(L)(MeCN)2]2+ (5a−d) were obtained by the treatment of 3a−d with 2 equiv of AgOTf followed by addition of CH3CN. Structures of complexes 3a−d and 5a−d were determined by X-ray crystallographic studies. Complex 5a (L = 1,3,4,5-tetramethylimidazol-2-ylidene) catalyzed the Oppenauer-type oxidation of primary and secondary alcohols very selectively under mild conditions. In the oxidation of 1-phenylethanol and cyclopentanol using 5a as a catalyst, turnover numbers reached 3200 and 6640, respectively. These results demonstrate that, to the best of our knowledge, the cationic carbene complex 5a is the most effective catalyst in homogeneous oxidation of alcohols in terms of its high catalytic activity and wide applicability to the oxidation of primary and secondary alcohols. In this catalytic system, the stronger electron-donating ability of the N-heterocyclic carbene ligand than the phosphine ligand is more favorable for acceleration of the hydride transfer to acetone as a hydrogen acceptor. Additionally, dihydrido carbene complex Cp*Ir(L)(H)2 (6) and dinuclear iridium carbene complex [Cp*Ir(L)(μ-H)]22+ (7) were prepared to investigate the catalytically active species and fate of the catalyst. Thus, it is highly probable that an iridium-monohydride complex is the catalytically active species and that 7, which could be generated by dimerization of the iridium-monohydride complex in the catalytic system, is inactive.

Neutral N−O Chelated Palladium(II) Complexes: Syntheses, Characterization, and Reactivity

A series of neutral salicylaldiminato Pd(II) complexes, Pd(Me)(Ph-CHN-R‘)[3-tBu-2-(O)C6H3-CHN-2,6-di-iPr-C6H3] (R = CH3, n-Pr, tert-Bu, Ph, benzyl) (3a−3e) and Pd(Me)[2-(CHN-t-Bu)-Py][3-tBu-2-(O)C6H3-CHN-2,6-di-iPr-C6H3] (4), have been synthesized and characterized. The structures of complexes 3a, 3c−3e, and 4 have been confirmed by X-ray analysis. NMR studies utilizing 3c indicate that the insertion of CO into the Pd−Me bond occurs through a five-coordinate intermediate. The acyl compounds in turn undergo imine insertion. The neutral complexes 3a−3e show moderate catalytic activity for the polymerization of methyl acrylate at ambient temperature. However, a radical rather than vinyl insertion mechanism appears to be operative.

Reactions of 16-Electron Iridium(III) Dithiolene Complexes with Diazoalkanes: Formation and Properties of Novel Mononuclear and Binuclear Alkylidene Adducts of Iridium Dithiolene Complexes

Some 16-electron pentacoordinated iridium dithiolene complexes were synthesized by the reactions of [Cp*Ir(Cl)(μ-Cl)]2 (Cp* = C5Me5) with 1,3-dithiol-2-one derivatives. The iridium dithiolene complex [Cp*Ir{S2C2(COOMe)2}] (1) reacted with ethyl diazoacetate or (trimethylsilyl)diazomethane to give the 1:1 alkylidene adducts of iridium dithiolene complexes (R = COOEt (3a), SiMe3 (3b)), respectively. The structures of complexes 3a,b were determined by X-ray crystal structure analyses: the COOEt unit of complex 3a is located at the exo position with respect to the iridadithiolene ring, and the SiMe3 group of complex 3b is located at the corresponding endo position with respect to the same ring. In solution, the endo (3b-1) and exo (3b-2) isomers of complex 3b were observed. In an electrochemical investigation, the oxidized species of the exo isomer (3b-2+) was isomerized to the stable endo isomer (3b-1+). The reaction of complex 1 with diazomethane gave the novel 2:2 methylene adduct of a binuclear iridium dithiolene complex (4). This complex 4 has a five-membered iridadithiolene ring and a six-membered iridacycle. The dimeric complex 4 was also formed from the desilylation of the monomeric complex 3b with TBAF. The complex (5a) that includes a six-membered iridacycle was obtained by the reaction of the alkylidene-bridged complex 3a with trimethyl phosphite. The reactions of complex 3b with HCl gave [Cp*Ir(Cl){S(SCH2SiMe3)C2(COOMe)2}] (6b) due to Ir−C bond cleavage.

Facile Transformations of Lanthanocene Alkyls to Lanthanocene Thiolate, Sulfide, and Disulfide Derivatives by Reaction with Elemental Sulfur

Treatment of [Cp2Ln(μ-Me)]2 with 2 equiv of elemental sulfur in toluene at room temperature leads to the formation of the methylthiolate complexes [Cp2Ln(μ-SMe)]2 [ Ln = Yb (1a), Y (1b), Er (1c), Dy (1d)] in good yields. While reaction of Cp2Y(nBu) with elemental sulfur in 1:1 stoichiometric ratio under the same conditions yields [(Cp2Y)2(μ3-S)(THF)]2 (2a) as the metal-containing product with the extrusion of nBuSnBu and nBuSSnBu, the corresponding insertion intermediate [Cp2Y(μ-SnBu)]2 (1e) could be isolated only by decreasing the relative amount of S8 under more mild reaction conditions. Furthermore, [Cp2Yb(μ-SEt)]2 reacts with 2 equiv of sulfur to give a mixture of [(Cp2Yb)2(μ3-S)(THF)]2 (2b) and [Cp2Yb(THF)]2(μ-η2:η2-S2) (3). 2b and 3 can also be prepared from the reaction of [Cp2Yb(μ-Me)]2 with excess elemental sulfur in THF. All these results demonstrate that lanthanocene thiolate complexes are unstable in solution with S8, and the nature of the alkyl ligands and reaction conditions has a great influence on the final product structures from the reaction of lanthanocene alkyls with elemental sulfur and provides an easy access to trivalent lanthanocene thiolate, sulfide, and disulfide complexes as well as thioethers and organic disulfides. Complexes 1−3 were characterized by elemental analysis and IR and mass spectroscopies. The structures of complexes 1a, 1e, 2a, 2b, and 3 are also determined through X-ray single-crystal diffraction analysis.

A Succession of Isomers of Ruthenium Dihydride Complexes. Which One Is the Ketone Hydrogenation Catalyst?

Reaction of RuHCl(PPh(3))(2)(diamine) (1a, diamine = (R,R)-1,2-diaminocyclohexane, (R,R)-dach; 1b, diamine = ethylenediamine, en) with KO(t)Bu in benzene quickly generates solutions of the amido-amine complexes RuH(PPh(3))(2)(NHC(6)H(10)NH(2)), (2a'), and RuH(PPh(3))(2)(NHCH(2)CH(2)NH(2)), (2b'), respectively. These solutions react with dihydrogen to first produce the trans-dihydrides (OC-6-22)-Ru(H)(2)(PPh(3))(2)(diamine) (t,c-3a, t,c-3b). Cold solutions (-20 degrees C) containing trans-dihydride t,c-3a react with acetophenone under Ar to give (S)-1-phenylethanol (63% ee). Complexes t,c-3 have lifetimes of less than 10 min at 20 degrees and then isomerize to the cis-dihydride, cis-bisphosphine isomers (OC-6-32)-Ru(H)(2)(PPh(3))(2)(diamine) (Delta/Lambda-c,c-3a, c,c-3b). A solution containing mainly Delta/Lambda-c,c-3a reacts with acetophenone under Ar to give (S)-1-phenylethanol in 20% ee, whereas it is an active precatalyst for its hydrogenation under 5 atm H(2) to give 1-phenylethanol with an ee of 50-60%. Complexes c,c-3 isomerize to the cis-dihydride, trans-bisphosphine complexes (OC-6-13)-Ru(H)(2)(PPh(3))(2)(diamine) (c,t-3a, c,t-3b) with half-lives of 40 min and 1 h, respectively. A mixture of Delta/Lambda-c,c-3a and c,t-3a can also be obtained by reaction of 1a with KBH(Bu(sec))(3). A solution of complex c,t-3a in benzene under Ar reacts very slowly with acetophenone. These results indicate that the trans-dihydrides t,c-3a or t,c-3b along with the corresponding amido-amine complexes 2a' or 2b' are the active hydrogenation catalysts in benzene, while the cis-dihydrides c,c-3a or c,c-3b serve as precatalysts. The complexes RuCl(2)(PPh(3))(2)((R,R)-dach) or 1a, when activated by KO(t)Bu, are also sources of the active catalysts. A study of the kinetics of the hydrogenation of acetophenone in benzene catalyzed by 3a indicates a rate law: rate = k[c,c-3a](initial)[H(2)] with k = 7.5 M(-1) s(-1). The turnover-limiting step appears to be the reaction of 2a' with dihydrogen as it is for RuH(NHCMe(2)CMe(2)NH(2))(PPh(3))(2) (2c'). The catalysts are more active in 2-propanol, even without added base, and the kinetic behavior is complicated. The basic cis-dihydride c,t-3a reacts with [NEt(3)H]BPh(4) to produce the dihydrogen complex (OC-14)-[Ru(eta(2)-H(2))(H)(PPh(3))(2)((R,R)-dach)]BPh(4) (4) and with diphenylphosphinic acid to give the complex RuH(O(2)PPh(2))(PPh(3))(2)((R,R)-dach) (5). The structure of 5 models aspects of the transition state structure for the ketone hydrogenation step. Complex 2b' decomposes rapidly under Ar to give dihydrides 3b along with a dinuclear complex (PPh(3))(2)HRu(mu-eta(2);eta(4)-NHCHCHNH)RuH(PPh(3))(2) (6) containing a rare, bridging 1,4-diazabutadiene group. The formation of an imine by beta-hydride elimination from the amido-amine ligand of 2a' under Ar might explain some loss of enantioselectivity of the catalyst. The structures of complexes 1a, 5, and 6 have been determined by single-crystal X-ray diffraction.

Reactions of [Re(NO)2(PR3)2][BArF4] complexes with phenylacetylene

The reaction of [Re(NO)2(PR3)2][BArF 4] (R = cyclo-C6H13 (1a), Pri (1b); [BArF 4]– = [B(3,5-(CF3)2C6H3)4]) with phenylacetylene in the presence of a non-nucleophilic base, like 2,6-bis(tert-butyl)pyridine (BTBP) or ButOK, affords the phenylethynyl complexes [Re(C≡CPh)(NO)2(PR3)2] (R = cyclo-C6H13 (2a); Pri (2b)) in moderate yields. In the absence of a base, complexes 1a and 1b are transformed into the compounds [Re(C≡CPh)(CH=C(Ph)ONH)(NO)(PR3)2][BArF 4] (3a and 3b, respectively). The structure of complex 3a was confirmed by X-ray diffraction analysis. The latter reaction is proposed to be initiated by deprotonation of the terminal alkyne H atom by the bent nitrosyl ligand followed by the subsequent 1,3-dipolar addition of the ReN(H)O moiety to phenylacetylene.

Incorporation of alkyne and vinylidene ligands into tetrazolate groups at a sulfur-rich dimolybdenum site using sodium azide

Treatment of either the μ-alkyne complex [Mo 2Cp 2(μ-SMe) 3(μ-PhCCH)](BF 4) ( 1) or the μ-vinylidene derivatives [Mo 2Cp 2(μ-SMe) 3(μ-η 1:η 2-(CCHR)](BF 4) ( 2) (R=Ph, Tol, nPr, C(CH 3)CH 2) with NaN 3 in ethanol at room temperature readily afforded μ-tetrazolate carbene complexes [Mo 2Cp 2(μ-SMe) 3){μ-η 1(C):η 1(N)-N 4CCR)}] (R=Ph ( 4a), Tol ( 4b), nPr ( 4c), C(CH 3)CH 2 ( 4d)). A mechanism which accounts for the formation of 4 by intramolecular 1,3-dipolar cycloaddition of metal-coordinated azide ligands to metal-coordinated nitriles is discussed. The structure of complex 4a has been determined by single X-ray diffraction analysis.

New neutral nickel(II) complexes bearing pyrrole-imine chelate ligands: synthesis, structure and norbornene polymerization behavior

New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands ( 4a– d), [2-(ArNCH)C 4H 3N]Ni(PPh 3)Ph [Ar2,6-diisopropylphenyl ( a), 2-methyl-6-isopropylphenyl ( b), 2,6-diethylphenyl ( c), 2- tert-butylphenyl ( d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh 3) 2(Ph)Cl, and the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2×10 7 g (mol Ni h) −1 and the viscosity-average molecular weight of polymer of up to 9.2×10 5 g mol −1 were observed. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as Al–Ni ratio, norbornene–catalyst ratio, monomer concentration, polymerization reaction temperature and time.