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The reaction between pyridine-2-ylmethanol (HL), anhydrous CoCl2and NaH afforded polynuclear Co(ii) complexes [Co7(L)12]Cl2(1), [Co6Na(L)12]Cl (2) and [Co4Cl2(L)6] (3), depending on the HL:CoCl2ratio set in the reaction. The core structures of the centrosymmetric complexes 1and 2are of the M@Co6type (M = Co or Na, respectively) with a coplanar arrangement of the metals whereas that of centrosymmetric 3is of an incomplete dicubane type. The experimental conditions allowing interconversions between these polynuclear complexes have been determined, which provides a more rational control of their synthesis. Thus, 1transforms to 3when reacted with CoCl2in a 1 : 1 ratio, whereas the same reaction performed with a large excess of CoCl2gave the tetranuclear pseudo-cubane complex [Co4(L)4Cl2(MeOH)4] upon recrystallization. Conversely, 1was isolated from the reaction of 3with HL and NaH. The crystal structure of these compounds is reported, along with the magnetic behaviour of 1and 3. The analysis of the magnetism using the effective spin-1/2 Hamiltonian approach revealed single-molecule metamagnetic behavior in 3. [ABSTRACT FROM AUTHOR]

A novel heterodifunctional phosphinite imidazolium salt was synthesized and reacted with Ag(I) to afford an unusual tetrasilver cubane-type cluster with two P-NHC ligands bridging between the Ag(I) centres of opposite Ag2I2faces. [ABSTRACT FROM AUTHOR]

The readily available Pt(0) methyl acrylate complex [Pt{CH2CHC(O)OMe}(PPh3)2] (2) allows access to the known, mixed-valence trinuclear cluster [Pt3(μ-PPh2)3Ph(PPh3)2] (3) in 64% yield. Oxidation of 3with 2 equivalents of I2afforded the new trinuclear complex [Pt3(μ-I)2(μ-PPh2)2I2(PPh3)2] (4) whose molecular structure is similar to that of the related compound of empirical formula [Pt3(μ-I)2(μ-PPh2)2Cl0.5I1.5(PPh3)2] (5) which has been generated by oxidation of 3with successively 1 equivalent of I2and 1 equivalent of C6H5ICl2. In these complexes, the four halogen atoms lie on the same side of the almost aligned platinum atoms and the nearly square-planar coordination planes of the metal atoms adopt a “japanese screen”, chair-like conformation. The reaction of the dinuclear, metal–metal bonded Pt(I)–Pt(I) complex [Pt2(μ-PPh2)2(PPh3)2] with one equivalent of I2afforded the Pt(II) complex [Pt2(μ-PPh2)2I2(PPh3)2] (6). The molecular structures of complexes 2·CH2Cl2, [Pt3(μ-I)2(μ-PPh2)2(I1.3Cl0.7)(PPh3)2][Pt3(μ-I)2(μ-PPh2)2(I1.7Cl0.3)(PPh3)2]·C6H5Cl·3CH2Cl2(5A·5B·C6H5Cl·3CH2Cl2) and 6have been established by single crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

The coordination properties of the β-keto phosphine ligands R2PCH2C(O)Ph (HL1, R = i-Pr; HL2, R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)2PNHC(O)Me (HL3) and of Ph2PNHC(O)Me (HL4) have been examined towards Ni(ii) complexes. Comparisons are made between systems in which the PCH2function of the ketophosphine has been replaced with an isoelectronic PNH group in amide-derived ligands, or the PCH functionality of phosphinoenolates with a PN group in phosphinoiminolate complexes. Furthermore, ligands HL2and HL4reacted with [(η5-C5H5)CoI2(CO)] to afford the phosphine mono-adducts [(η5-C5H5)CoI2{Ph2PCH2C(O)Ph}] (1) and [(η5-C5H5)CoI2{Ph2PNHC(O)Me}] (3), respectively, which upon reaction with excess NEt3yielded the phosphinoenolate complex [(η5-C5H5)CoI{Ph2PCHC(O)Ph}] (2) and the phosphinoiminolate complex [(η5-C5H5)CoI{Ph2PNC(O)Me}] (4), respectively. The complexes cis-[Ni{(i-Pr)2PNC(O)Me}2] (6) and cis-[Ni{Ph2PNC(O)Me}2] (7) were obtained similarly from NiCl2and HL3and HL4, respectively, in the presence of a base. The phosphinoenolate complex [Ni{(i-Pr)2PCHC(O)Ph}2] (5) exists in ethanol as a mixture of the cisand transisomers, in contrast to cis-[Ni{(Ph2PCHC(O)Ph}2], and the solid-state structure of the transisomer of 5was established by X-ray diffraction. The structures of the ligand HL3and of the complexes 1, 3in 3·3/2CH2Cl2, 4, 6and 7have also been determined by X-ray diffraction and are compared with those of related complexes. Complexes 4, 6and 7contain a five-membered heteroatomic metallocyclic moiety, which is constituted by five different chemical elements. The structural consequences of the steric bulk of the P substituents and of the electronic characteristics of the P,O chelates are discussed. [ABSTRACT FROM AUTHOR]

The dinuclear chromium complexes [Cr2(N,O)3Cl3] (6) (N,O = 4,4-dimethyl-2-oxazolylmethanolate), [Cr2(N,OMe2)2(EtOH)2Cl4] (7) and [Cr2(N,OMe2)2(H2O)2Cl4] (8) (N,OMe2= 4,4-dimethyl-2-oxazolyldimethylmethanolate) have been prepared and characterized, including by single-crystal X-ray diffraction. Complex 6is unsymmetrical, with two chloride ligands terminally bound to one Cr atom, whereas 7and 8(in 8·C4H8O) which contain two molecules of coordinated ethanol or water, respectively, are centrosymmetric. These chromium complexes are paramagnetic, and the magnetic properties of 6and 7in the solid state correspond to antiferromagnetic behaviour, which was confirmed by DFT calculations of their electronic structures. Complexes 6–8were evaluated in the catalytic oligomerization and/or polymerization of ethylene with different aluminium-based cocatalysts, and MMAO proved to be the most effective one. In the presence of MMAO, the influence of different reaction parameters, such as the Al/Cr molar ratio, reaction temperature and ethylene pressure, was investigated. Complex 7showed the highest activity for ethylene polymerization at both 1 atm and 10 atm of ethylene pressure, up to 620 000 g mol−1(Cr) h−1in the latter case. [ABSTRACT FROM AUTHOR]

The N,P,N-type ligands bis(2-picolyl)phenylphosphine (1), bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine (2), bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine (3) and bis(2-picolyloxy)phenylphosphine (4) were used to synthesize the corresponding pentacoordinated Ni(ii) complexes [Ni{bis(2-picolyl)phenylphosphine}Cl2] (6), [Ni{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}Cl2] (7), [Ni{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl2] (8) and [Ni{bis(2-picolyloxy)phenylphosphine}Cl2] (9), respectively. The hexacoordinated iron complexes [Fe{bis(2-picolyl)phenylphosphine}2][Cl3FeOFeCl3] (10), [Fe{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}2][Cl3FeOFeCl3] (11) and the tetracoordinated complex [Fe{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl2] (abbreviated [FeCl2(NPNMe2-N,N)]) were prepared by reaction of FeCl2·4H2O with ligands 1–3, respectively. The crystal structures of the octahedral complexes 10 and 11, determined by X-ray diffraction, showed that two tridentate ligands are facially coordinated to the metal centre with a cis-arrangement of the P atoms and the dianion (μ-oxo)bis[trichloroferrate(iii)] compensates the doubly positive charge of the complex. The cyclic voltammograms of 10 and 11 showed two reversible redox couples attributed to the reduction of the dianion (Fe2OCl6)2− (−0.24 V for 10 and −0.20 V for 11vs. SCE) and to the oxidation of the Fe(ii) ion of the complex (0.67 V for 10 and 0.52 V for 11vs. SCE). The cyclic voltammogram of [FeCl2(NPNMe2-N,N)] showed a reversible redox couple at −0.17 V vs. SCE assigned to the oxidation of the Fe(ii) atom and an irreversible process at 0.65 V. The complexes 6, 8–11 and [FeCl2(NPNMe2-N,N)] have been evaluated in the catalytic oligomerization of ethylene with AlEtCl2 or MAO as cocatalyst. The nickel complex 6 proved to be the most active precatalyst in the series, with a turnover frequency (TOF) of 61 800 molC2H4 molNi−1 h−1 with 10 equiv. of AlEtCl2 and 12 200 molC2H4 molNi−1 h−1 with 200 equiv. of MAO. Precatalysts 8 and 9 were the most selective in butenes, up to 90% with 6 equiv. of AlEtCl2 and 89% with 2 equiv. of AlEtCl2, respectively, and up to 92% butenes with 400 equiv. of MAO and 91% butenes with 200 equiv. MAO, respectively. The best selectivities for 1-butene were provided by 8 and AlEtCl2 (up to 31% with 6 equiv.) and 9 with MAO (up to 72% with 200 equiv.). The iron complexes were not significantly active with AlEtCl2 or MAO as cocatalyst. [ABSTRACT FROM AUTHOR]

The dinuclear complexes [Ni(µ-Cl){(4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol}]2Cl214 and [Ni(µ-Cl){(pyridin-2-yl)methanol}]2Cl216 have been synthesized in high yields by reaction of NiCl2 with 2 mol. equiv. of the ligands 4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol 13 or (pyridin-2-yl)methanol 15, respectively. The reaction of NiCl2 with 3 mol. equiv. of 15 afforded in high yield the mononuclear, octahedral mer-[Ni{(pyridin-2-yl)methanol}3Cl2] complex 18. The reaction of 16 with NaH led to the deprotonation of one of the pyridine alcohol ligands to form [Ni{(pyridin-2-yl)methanol}{(pyridin-2-yl)methanolate}Cl] 21 in which the metal is coordinated by one pyridine alcohol and one pyridine alcoholate ligand. The crystal structures of the dinuclear, chloride-bridged octahedral complexes in 14·C6H12 and in 16·3CH2Cl2 and of the mononuclear, octahedral complex 18 in 18·CH2Cl2 have been determined by X-ray diffraction. In the latter case, intermolecular OH⋯Cl bonding interactions generate a centrosymmetric pseudo-dimer. Complexes 14, 16 and 21 have been tested in ethylene oligomerization with AlEtCl2 (Al/Ni ratios of 2, 4 or 6) or MAO (50, 100 or 200 equiv.) as co-catalysts under 10 bar of ethylene and yielded mostly dimers and trimers. Complex 16 in the presence of 6 equiv. of AlEtCl2 proved to be the most active system with a turnover frequency (TOF) up to 187 500 C2H4 (mol Ni h)−1. Complex 16 with 200 equiv. of MAO was also the most active, with TOF up to 104 300 C2H4 (mol Ni h)−1 under 30 bar of ethylene. [ABSTRACT FROM AUTHOR]

The β-keto phosphorus ylides (n-Bu)3PCHC(O)Ph 6, (t-Bu)2PhPCHC(O)Ph 7, (t-Bu)Ph2PCHC(O)Ph 8, (n-Bu)2PhPCHC(O)Ph 9, (n-Bu)Ph2PCHC(O)Ph 10, Me2PhPCHC(O)Ph 11 and Ph3PCHC(O)(o-OMe-C6H4) 12 have been synthesized in 80–96% yields. The Ni(ii) complexes [NiPh{Ph2PCHC(O)(o-OMeC6H4)}(PPh3)] 13, [NiPh{Ph(t-Bu)PCHC(O)Ph}(PPh3)] 15, [NiPh{(n-Bu)2PCHC(O)Ph}(PPh3)] 16 and [NiPh{Ph(n-Bu)PCHC(O)Ph}(PPh3)] 17 have been prepared by reaction of equimolar amounts of [Ni(COD)2] and PPh3 with the β-keto phosphorus ylides 12 or 8–10, respectively, and characterized by 1H and 31P{1H} NMR spectroscopy. NMR studies and the crystal structure determination of 13 indicated an interaction between the hydrogen atom of the C–H group α to phosphorus and the ether function. The complexes [NiPh{Ph2PCHC(O)Ph}(Py)] 18, [NiPh{Ph(t-Bu)PCHC(O)Ph}(Py)] 19, [NiPh{(n-Bu)2PCHC(O)Ph}(Py)] 20, [NiPh{Ph(n-Bu)PCHC(O)Ph}(Py)] 21 and [NiPh{Me2PCHC(O)Ph}(Py)] 22 have been isolated from the reactions of [Ni(COD)2] and an excess of pyridine with the β-keto phosphorus ylides Ph3PCHC(O)Ph 3 or 8–11, respectively, and characterized by 1H and 31P{1H} NMR spectroscopy. Ligands 3, 8, 10 and 12 have been used to prepare in situ oligomerization catalysts by reaction with one equiv. of [Ni(COD)2] and PPh3 under an ethylene pressure of 30 or 60 bar. The catalyst prepared in situ from 12, [Ni(COD)2] and PPh3 was the most active of the series with a TON of 12 700 mol C2H4 (mol Ni)−1 under 30 bar ethylene. When the β-keto phosphorus ylide 8 was reacted in situ with three equiv. of [Ni(COD)2] and one equiv. of PPh3 under 30 bar of ethylene, ethylene polymerization was observed with a TON of 5500 mol C2H4 (mol Ni)−1. [ABSTRACT FROM AUTHOR]

Cobalt(ii) complexes of the type [CoCl2(P,N)], where P,N represents a heterobidentate phosphino- or phosphinito-oxazoline-type ligand, have been synthesised and characterised by infrared spectroscopy and elemental analysis. Their molecular structures were established by single-crystal X-ray diffraction in the solid state. Whereas the phosphino-oxazoline complex [CoCl2{Ph2PCH2oxMe2}] (Ph2PCH2oxMe2 = 2-[(diphenylphosphanyl)-methyl]-4,4-dimethyl-4,5-dihydro-oxazole) (8) and the phosphinito-oxazoline complexes [CoCl2{Ph2POCH2oxMe2}] (Ph2POCH2oxMe2 = 1-[4,4-dimethyl-2{1-oxy(diphenylphosphino)-1-methyl}]-4,5-dihydro-oxazole) (9) and [CoCl2{Ph2POCMe2oxMe2}] (Ph2POCMe2oxMe2 = 1-[4,4-dimethyl-2- [1-oxy(diphenylphosphino)-1-methylethyl]]-4,5-dihydrooxazole) (10) are mononuclear, the phosphino-oxazoline complexes [CoCl2{μ-i-Pr2PCH2ox}]2 (i-Pr2PCH2ox = 2-[(diisopropyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) (6) and [CoCl2{µ-Ph2PCH2ox}]2 (Ph2PCH2ox = 2-[(diphenyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) (7) are dinuclear compounds and contain two bridging phosphino-oxazoline ligands which form a 10-membered ring. In the course of this work, the zwitterionic complex [CoCl3{Ph2PCH2C(O)OCH2CMe2NH3] (11) was obtained and characterised by X-ray diffraction in which the oxazoline ring has been opened. Air-oxidation of the phosphine function of the mononuclear P,N chelate complex 8 yielded the blue N,O-bridged, centrosymmetric dinuclear complex [┌CoCl2{μ-OPPh2CH2C=NCMe2CH2O}]2 (12) which contains a 12-membered ring. All these complexes are paramagnetic and their magnetic moments in solution were measured by the Evans method. Complexes 6–10 were evaluated in the catalytic oligomerisation of ethylene with AlEtCl2 or methylaluminoxane (MAO) as cocatalysts and provided moderate activities. In the presence of AlEtCl2 (6–14 equiv.), the selectivities for ethylene dimers were higher than 92% and complex 8 showed the highest turnover frequency with 14 equiv. of AlEtCl2. When MAO was used as cocatalyst, the catalytic activities were similar to those with AlEtCl2 but significant amounts of C6–C12 oligomers were produced. [ABSTRACT FROM AUTHOR]

The reaction of the iron metalate [Fe{Si(OMe)3}(CO)3(dppm-P)]− (1b) with [Ru(CO)3Cl(μ-Cl)]2 afforded the heterodinuclear complex [(OC)3{(MeO)3Si}Fe(μ-dppm)Ru(CO)3Cl)] (Fe–Ru) (3) in which a long Fe–Ru separation of 2.956(1)  has been crystallographically evidenced. It was shown by density functional theory (DFT) calculations to correspond to the minimum-energy structure. Upon treatment of the corresponding hydrido complex [HFe{Si(OMe)3}(CO)3(dppm-P)] (1a) with [Ru(CO)3Cl(μ-Cl)]2, the chloride-bridged tetranuclear hydrido complex [(OC)3{(MeO)3Si}Fe(H)(μ-dppm)Ru(CO)2Cl(μ-Cl)]2 (4) was formed in which the Fe and Ru centers are only linked via bridging dppm ligands. [ABSTRACT FROM AUTHOR]

The phosphinito-oxazoline ligand 4,4-dimethyl-2-[methoxy(diphenylphosphine)]-4,5-dihydrooxazole (2a) and the phosphonite-oxazoline ligand 4,4-dimethyl-2-[methoxy(6H-dibenz[c,e][1,2]oxaphosphorin)]-4,5-dihydrooxazole (8a) were prepared by deprotonation of (4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol (1a) and reaction with the corresponding P–Cl function, similar to the ligands 2b (4,4-dimethyl-2-[1-oxy(diphenylphosphine)-1-methylethyl]-4,5-dihydrooxazole) and 8b (4,4-dimethyl-2-[1-oxy(6H-dibenz[c,e][1,2]oxaphosphorin)-1-methylethyl]-4,5-dihydrooxazole) reported previously. These ligands react with [PdClX(COD)] to give complexes of the type [PdClX(P,N)] (3a P,N = 2a, X = Cl; 4a P,N = 2a, X = Me; 4b P,N = 2b, X = Me; 9a P,N = 8a, X = Cl; 9b P,N = 8b, X = Cl; 10a P,N = 8a, X = Me; 10b P,N = 8b, X = Me). Complexes 4a,b and 10a,b reacted with AgCF3SO3 to yield [PdMe(P,N)OSO2CF3] 5a,b and 11a,b, respectively. From the stepwise insertion reaction of CO and ethylene into the Pd–C bond of 5a and 11a,b, the alkyl ketone chelate complexes [┌Pd{CH2CH2C(O)Me}(P,N)]CF3SO37a and 14a,b respectively, have been isolated and spectroscopically characterized. Complexes 3a·CH2Cl2, 5a, 9b, 10a,b, [PdMe(H2O)(P,N)]CF3SO312b, (P,N = 8b) and 14a,b have also been characterized by X-ray crystallography and the structures of 14a,b represent still rare examples of structurally characterized CO/ethylene coupling products. [ABSTRACT FROM AUTHOR]

Both C–Cl bonds of CH2Cl2are readily activated by CoCl2and metallic Zn allowing quantitative methylation of phosphines; unprecedented zwitterionic Co(ii) and Zn(ii) intermediates have been characterized which display α-metallated phosphoniums. [ABSTRACT FROM AUTHOR]

Reactions of acetylpyridine derivatives with 8-aminoquinolines provide a general and simple access to an unexpected class of versatile N,N,N ligands, which offer interesting perspectives in coordination chemistry. [ABSTRACT FROM AUTHOR]

An unusual dinuclear Ir(i) complex bridged by two N-heterocyclic biscarbene ligands, forming a 20-membered, figure-of-eight dimetallacycle, and new CNHCCCNHC pincer complexes of Ir(iii) have been obtained directly from the bis(imidazolium) precursors and [Ir(μ-Cl)(cod)]2. [ABSTRACT FROM AUTHOR]

A straightforwardly synthesised complex, [Pd(μ-Cl)Cl(NHC)]2 (NHC = bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr), has been employed to mediate Suzuki–Miyaura reactions involving aryl chlorides at very low catalyst loadings and at room temperature. [ABSTRACT FROM AUTHOR]

Unexpected N,N-coordination of the potentially tridentate N,P,N-ligand bis(2-oxazolin-2,5,5-trimethyl)phenylphosphine occurs in Co(ii) and Fe(ii) complexes, in contrast to the P,N- or N,P,N-coordination modes observed in Pd(ii) complexes; this leads to the formation of unprecedented eight-membered ring chelates. [ABSTRACT FROM AUTHOR]