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The presence of a permethylated α-cyclodextrin (α-CD) cavity in a chelating P,N ligand promotes exclusive formation of 1 : 1 ligand/metal complexes. In MX

With their N-amine and N'-imine substituents, the imidazolium chlorides [(ImH){C(Me)[double bond, length as m-dash]NDipp}(C

The development of bifunctional non-noble metal electrocatalysts demonstrating high activity and stability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great significance for renewable and clean energy. In this work, we report hierarchically structured integrated Fe-MoS

The double aminolysis reaction of [Co{N(SiMe3)2}2] by the salt 1-(6-((dicyclohexylphosphaneyl)methyl)pyridin-2-yl)-3-(2,6-diisopropylphenyl)-1H-imidazol-3-ium bromide, which contains one phosphane, one pyridine and one imidazolium groups, of formula [o-Cy2PCH2(C5H3N)(o-C3H3N2DiPP)]Br and abbreviated as (CyPNpyrCim)Br, was previously shown to afford the Co(ii) complex [Co(CyP*NaCNHC)Br] (1) containing a dearomatised picolyl moiety in the tridentate, anionic donor ligand CyP*NaCNHC (Na = anionic amido, P* = vinylic P donor). We now report that formation of 1 is preceded by an intermediate tentatively assignable to the 5-coordinate Co(ii) complex [Co(CyPNpyrCNHC){N(SiMe3)2}Br] (2). The reaction of 1 with LiCH2SiMe3 afforded the dark purple, paramagnetic [Co(CyP*NaCNHC)CH2SiMe3] (3) with a low spin d7 CoII; the electronic configurations of 1 and 3 were corroborated by EPR spectroscopy. Addition of excess (≥4 equiv.) H2SiPh2 to a solution of 1 gave the diamagnetic [Co(CyP(SiHPh2)NCNHC)Br] (4) following Si-H activation and silylation of the ligand backbone at the α-CHP. Reduction of CoII to CoI by silanes is uncommon.

New non-symmetrical, redox-active imino NHC pyridine pincer ligands, 2-(R1-imidazol-2-ylidene)-6-(R2NCH)-pyridine (R1 = 2,6-diisopropylphenyl (DiPP), R2 = 2,4,6-trimethylphenyl (Mes), 4B; R1 = R2 = DiPP, 4C), have been accessed by a ZnII-promoted modular synthesis involving the quaternization of R1-imidazole by [Zn(κNimineκNpyridine)(2-(R2NCH)-6-bromo-pyridine)Cl2], followed by ZnII removal and deprotonation of imidazolium pro-ligands. Redox active forms of 4B were implicated in the two complexes obtained by its reaction with FeBr2/KC8; metrical data analysis pointed to the occurrence of radical anionic and dianionic redox states of 4B.

The linear, two-coordinate and isostructural heteroleptic [M(IPr){N(SiMe

A series of P-NHC-type hybrid ligands containing both PR2 and N-heterocyclic carbene (NHC) donors on meta-bis-substituted phenylene backbones, L(Cy), L(tBu) and L(Ph) (R = Cy, tBu, Ph, respectively), was accessed through a modular synthesis from a common precursor, and their coordination chemistry with coinage metals was explored and compared. Metallation of L(Ph)·n(HBr) (n = 1, 2) with Ag2O gave the pseudo-cubane [Ag4Br4(L(Ph))2], isostructural to [Ag4Br4(L(R))2] (R = Cy, tBu) (T. Simler, P. Braunstein and A. A. Danopoulos, Angew. Chem., Int. Ed., 2015, 54, 13691), whereas metallation of ·HBF4 (R = Ph, tBu) led to the dinuclear complexes [Ag2(L(R))2](BF4)2 which, in the solid state, feature heteroleptic Ag centres and a 'head-to-tail' (HT) arrangement of the bridging ligands. In solution, interconversion with the homoleptic 'head-to-head' (HH) isomers is facilitated by ligand fluxionality. 'Head-to-tail' [Cu2Br2(L(R))2] (R = Cy, tBu) dinuclear complexes were obtained from L(R)·HBr and [Cu5(Mes)5], Mes = 2,4,6-trimethylphenyl, which also feature bridging ligands and heteroleptic Cu centres. Although the various ligands L(R)l ed to structurally analogous complexes for R = Cy, tBu and Ph, the rates of dynamic processes occurring in solution are dependent on R, with faster rates for R = Ph. Transmetallation of both NHC and P donor groups from [Ag4Br4(L(tBu))2] to AuI by reaction with [AuCl(THT)] (THT = tetrahydrothiophene) led to L(tBu) transfer and to the dinuclear complex [Au2Cl2L(tBu)] with one L(tBu) ligand bridging the two Au centres. Except for the silver pseudo-cubanes, all other complexes do not exhibit metallophilic interactions.

Attempts to evaluate experimentally the donor characteristics of the N,N'-bis(di-tert-butylphosphanyl)-imidazole-2-ylidene (PC(NHC)P) hybrid ligand are described. Thus, reactions of PC(NHC)P with [Rh(μ-Cl)(COD)]2 and [Rh(μ-Cl)(CO)2]2 led to the formation of the mononuclear and dinuclear complexes, [Rh(PC(NHC)P,κP,κC(NHC))2]Cl (PC(NHC)P-RhCl) and [Rh(CO)(PC(NHC),κP,κC(NHC),κN)]2 (PC(NHC)-RhCO), respectively, the latter resulting after in situ cleavage of one (t-Bu)2P-Nimid bond of PC(NHC)P. With ligands acting as a P,C-chelate, a straightforward evaluation of the Tolman electronic parameter (TEP) of the C(NHC) donor is problematical; the viability of dangling P- and bound C(NHC)-donors (i.e.κC(NHC)) has been observed in the trinuclear Fe(ii) chain complex [Fe3Cl2(μ-Cl)4(THF)2(PC(NHC)P,κC(NHC))2] (PC(NHC)P-Fe), obtained by the reaction of PC(NHC)P with [Fe4Cl8(THF)6] and, recently, established on Cr(II), Co(II) and Au(I) centres. Evaluation of the π-accepting properties of the PC(NHC)P (and the related Dipp-PC(NHC)) was based on the (77)Se NMR chemical shifts of the corresponding NHC-Se adducts, PC(NHC)P-Se (and Dipp-PC(NHC)-Se), which were prepared from the free PC(NHC)P (and Dipp-PC(NHC)) and Se. The π-acidity of PC(NHC)P is found to be higher than that of Dipp-PC(NHC) but lower than that of SIPr. The donor ability of the C(NHC) in PC(NHC)P was explored by its reaction with the Lewis acids tris(pentafluorophenyl)borane (B(C6F5)3) and tris(pentafluorophenyl)boroxine ([(C6F5)BO]3), which resulted in stable donor-acceptor adducts with no FLP reactivity. The steric properties of PC(NHC)P and Dipp-PC(NHC) are conformation dependent, with the percent buried volume (%Vbur) of PC(NHC)P in the structurally characterised conformer calculated at 67.6, the largest value currently reported for NHC ligands.

A reaction of the 44 electron cluster [Pt3(μ-PPh2)3Ph(PPh3)2] (1) with wet AgBF4 afforded the cationic cluster [Pt3(μ2-OH)(μ-PPh2)2(PPh3)3]BF4 (3(BF4)) which slowly transformed into [Pt3(μ2-Cl)(μ-PPh2)2(PPh3)3]BF4 (4(BF4)) upon recrystallization from CH2Cl2. These 44 electron clusters have been characterized by (31)P{(1)H} NMR, and the crystal structure of 4(PF6) has been determined by X-ray diffraction, as well as that of [Pt3(μ-PPh2)2I2(PPh3)3] (5), which was obtained by recrystallization of the known cluster [Pt3(μ2-I)(μ-PPh2)2(PPh3)3]I (2(I)) from toluene and represents a neutral formula isomer of the latter. In addition, we have prepared the adducts of cluster 1 containing the moieties [Cu(NCMe)2](+) and [Au(PPh3)](+) in 6 and 7, respectively, and on the basis of their spectroscopic data, it was concluded that these complexes have similar structures to that previously established for the adduct of 1 with Ag(TFA) (TFA = OC(O)CF3), [Pt3{μ3-Ag(TFA)}(μ-PPh2)3Ph(PPh3)2] (8). The cationic clusters in 3(BF4) and 4(BF4) react with Ag(TFA) to afford cationic adducts in [Pt3{μ3-Ag(TFA)}(μ2-X)(μ-PPh2)2(PPh3)3]BF4 (9(BF4), X = OH; 10(BF4), X = Cl). The structure of the mixed-metal cluster [Pt3(μ3-AgBF4)(μ2-I)(μ-PPh2)2(PPh3)3]BF4 (11(BF4)), obtained by reaction of the complex 2(I) with AgBF4, was determined by X-ray diffraction.

We describe the synthesis, structures, and magnetochemistry of new M4Cl4 cubane-type cobalt(II) and nickel(II) complexes with the formula [M(μ3-Cl)Cl(HL·S)]4 (1: M = Co; 2: M = Ni), where HL·S represents a pyridyl-alcohol-type ligand with a thioether functional group, introduced to allow subsequent binding to Au surfaces. Dc and ac magnetic susceptibility data of 1 and 2 were modeled with a full spin Hamiltonian implemented in the computational framework CONDON 2.0. Although both coordination clusters 1 and 2 are isostructural, with each of their transition metal ions in a pseudo-octahedral coordination environment of four Cl atoms and N,O-donor atoms of one chelating HL·S ligand, the substantially different ligand field effects of Co(II) and Ni(II) results in stark differences in their magnetism. In contrast to compound 1 which exhibits a dominant antiferromagnetic intramolecular coupling (J = -0.14 cm(-1)), 2 is characterised by a ferromagnetic coupling (J = +10.6 cm(-1)) and is considered to be a single-molecule magnet (SMM), a feature of special interest for future surface deposition studies. An analysis based on density functional theory (DFT) was performed to explore possible magnetostructural correlations in these compounds. Using a two-J model Hamiltonian, it revealed that compound 1 has four positive and two (small) negative J(Co···Co) isotropic interactions leading to a S(HS) = 6 ground state. Taking into account the magnetic anisotropy, one would recover a M(S) = 0 ground state since D0 from computations. In 2, all the J constants are positive and, in this framework, the zero-field splitting energy characterising the axial anisotropy was estimated to be negative (D = -0.44 cm(-1)). The computational results are consistent with compound 2 being an SMM.

The reaction of one equivalent of 2-methyl-1-(pyridin-2-yl)propan-2-ol (HL) with two equivalents of [Ni(OAc)2·4H2O] in methanol afforded the nonanuclear coordination cluster [Ni9(HL-κ(2)N,O)4(OAc-κ(2)O)2(μ2-OAc-κ(1)O)2(μ2-OAc-κ(2)O,O')4(μ3-OAc-κ(2)O;κ(2)O,O')2(μ3-OMe)8] (1). All nickel ions are hexacoordinated and show a slightly distorted octahedral coordination geometry. This unusual centrosymmetric coordination cluster can be described as constituted by two cubane moieties connected by a linker comprising a nickel atom, situated on the inversion centre, four bridging acetates and two triply-bridging acetates. Each cubane contains four Ni(II) centres and four triply-bridging methoxide anions, two of the Ni(II) centres are N,O-chelated by the ligand HL, another Ni(II) is chelated by an acetate ligand and the fourth Ni(II) centre is connected to the exo-cubane Ni(II) through three acetate ligands which each have a different bonding mode: μ2-κ(2)O,O', μ2-κ(1)O, and μ3-κ(1)O;κ(2)O,O'. The magnetic and catalytic properties for ethylene oligomerization of the unusual complex have been investigated.

New cationic Ag(I) complexes were prepared by reaction of AgBF4 with two thioether-functionalized bis(diphenylphosphino)amine ligands, Ph2PN(p-ArSMe)PPh2 (L1) and Ph2PN(n-PrSMe)PPh2 (L2), and compared with those obtained from the unfunctionalized ligands Ph2PN(Ph)PPh2 (L3) and Ph2PN(n-Bu)PPh2 (L4), respectively. The complex [Ag3(μ3-Cl)2(μ2-L1-P,P)3](BF4) (1·BF4) contains a triangular array of Ag centres supported by three bridging L1 ligands and two triply-bridging chlorides. In contrast, ligand L2 led to the coordination polymer [{Ag2(μ3-L2,-P,P,S)2(MeCN)2}{Ag2(μ2-L2-P,P)2(MeCN)2}(BF4)4]n (2) in which the tethered thioether group connects intermolecularly a Ag2 unit to the diphosphine bridging the other Ag2 unit. With L3 and L4, two similar complexes were obtained, [Ag2(μ2-L3)(BF4)2] (3) and [Ag2(μ2-L4)(BF4)2] (4), respectively, with bridging diphosphine ligands and a BF4 anion completing the coordination sphere of the metal. Complexes 1·BF4·CH2Cl2, 2·THF, 3·3CH2Cl2 and 4 have been fully characterized, including by single crystal X-ray diffraction.

International audience; The reactions of NiCl2 center dot 2H(2)O or [NiCl2(DME)] (DME = dimethoxyethane) with 2-methyl-1-(pyridin-2-yl)-propan-2-ol (HL) and 2-(pyridin-2-yl) ethanol (HLEt), in a 1 : 1 ratio, afforded the tetranuclear, cubane-type clusters [Ni(mu(3)-Cl)Cl(HL)](4) (3) and [Ni(mu(3)-Cl) Cl(HLEt)](4) (4), respectively. These are tetramers of the hypothetical mononuclear formula-isomers [NiCl2(HL)] and [NiCl2(HLEt)], respectively, and represent rare examples of structurally characterized cubane-like transition metal dihalogenide complexes. The 2 : 1 reactions between HL or HLEt and [NiCl2(DME)] yielded, instead, the mononuclear [NiCl2(HL)(2)] (1) and the dinuclear complex [Ni(mu-Cl)(HLEt)(2)](2)Cl-2 (2), respectively. The reaction of 3 with NaOH afforded selectively the cubane-type cluster [Ni(mu(3)-OH)Cl(HL)](4) (5) which differs only in the nature of the capping anions (Cl vs. OH, respectively). The magnetic properties of the unusual tetranuclear cubanes 3 and 5 have been investigated and revealed in both cases single-molecule magnet (SMM) behaviour.

Density functional theory calculations have been employed to model the double C-Cl bond activation of CH(2)Cl(2) at [CoCl(PR(3))(3)] to give [CoCl(3)(CH(2)PR(3))(PR(3))(2)]. Calculations incorporating dichloromethane solution (PCM approach) on a [CoCl(PMe(3))(3)] model system showed the two C-Cl cleavage steps to involve different mechanisms. The first C-Cl cleavage step occurs on the triplet surface and proceeds via Cl abstraction with a barrier of 19.1 kcal mol(-1). Radical recombination would then give singlet mer,trans-[CoCl(2)(CH(2)Cl)(PMe(3))(3)] with an overall free energy change of +1.8 kcal mol(-1). Alternative C-Cl activation processes based on nucleophilic attack by the Co centre at dichloromethane with loss of Cl(-) have significantly higher barriers. The second C-Cl cleavage occurs via nucleophilic attack of PMe(3) at the CH(2)Cl ligand with formation of a new P-C bond and displacement of Cl(-). This may either occur in an intermolecular fashion (after prior PMe(3) dissociation) or intramolecularly. Both processes have similar barriers of ca. 12 kcal mol(-1). The comproportionation of [CoCl(3)(CH(2)PMe(3))(PMe(3))(2)] with [CoCl(PMe(3))(3)] to give [CoCl(2)(CH(2)PMe(3))(PMe(3))], [CoCl(2)(PMe(3))(2)] and 2 PMe(3) is computed to be strongly exergonic, consistent with the observation of this process in analogous experimental systems.

A new family of N,N'-bis-(2,6-diisopropylphenyl)-(2,6-diisopropylphenyl-imidazolium)-acetamidines have been developed as NHC proligands and ligands that are functionalised with neutral amidine and anionic amidinato moieties. On coordination they adopt diverse binding modes, depending on the nature of the metal and the reaction conditions. In the Ag, K and Cr complexes reported in this paper, monodentate κ(1)(NHC), bimetallic bridging-(κ(1)-NHC-κ(1)-amidinato) and bidentate (κ(1)-NHC-κ(1)-amidinato) binding modes were observed, respectively. Two of the novel Cr complexes, in the presence of activators, were tested as catalysts for the polymerisation of ethylene showing low activity.

New titanium complexes of general formula [(ArO)(n)Ti(Oi-Pr)((4-n))] were synthesized and used as pre-catalysts for the selective dimerization of ethylene to 1-butene. The complexes were prepared in cyclohexane using [Ti(Oi-Pr)(4)] and one or two equivalents of the corresponding phenols (ArOH) at room temperature. In this work, both monodentate and chelating phenols were evaluated. For alkyl-substituted phenols, it was demonstrated that large steric hindrance at both ortho and ortho' positions selectively yielded the mono-substituted complexes [(ArO)Ti(Oi-Pr)(3)]. Substitution at only one of the ortho positions allowed both the mono- and the di-substituted Ti complexes to be isolated. When a heteroatom was introduced on the phenol backbone, di-substitution systematically occurred except with phenols presenting a hemilabile -CH(2)NR(2) group at the ortho position. Upon activation with 3 equiv. of AlEt(3) at 20 bar and 60 °C, all the complexes selectively dimerized ethylene to 1-butene (86% of butenes among which 99% of 1-butene). An increase of the steric bulk at the ortho position of the ligand or the introduction of a functional group led to decreased activity compared to [Ti(Oi-Pr)(4)].

The reaction of TCNE and TCNQ zwitterionic benzoquinonemonoimine derivatives under basic conditions resulted in HCN elimination to give a tricyanoethenyl derivative – which forms a π-complex with Pd(0) – or a stable malodinitrile salt, respectively. In the latter case, chemoselective C-alkylation was observed whereas oxidation led to dimerization by C–C coupling.

The synthesis of bis(thioether)-functionalized imidazolium salts, the characterisation of the first S,C(NHC),S free carbene ligand and the corresponding Ag(i) and Pd(ii) functional carbene complexes are reported. The latter have been prepared from the isolated Ag(i) carbene complexes using the transmetallation procedure or by reaction of the imidazolium salts with [PdCl(2)(COD)], followed by deprotonation of the intermediate in which both thioether functions are coordinated to Pd(ii).

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 Ag(2)I(2) faces.

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(mu-PPh2)3Ph(PPh3)2] (3) in 64% yield. Oxidation of 3 with 2 equivalents of I2 afforded the new trinuclear complex [Pt3(mu-I)2(mu-PPh2)2I2(PPh3)2] (4) whose molecular structure is similar to that of the related compound of empirical formula [Pt3(mu-I)2(mu-PPh2)2Cl0.5I1.5(PPh3)2] ( 5) which has been generated by oxidation of 3 with successively 1 equivalent of I2 and 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(mu-PPh2)2(PPh3)2] with one equivalent of I2 afforded the Pt(II) complex [Pt2(mu-PPh2)2I2(PPh3)2] (6). The molecular structures of complexes 2 x CH2Cl2, [Pt3(mu-I)2(mu-PPh2)2(I1.3Cl0.7)(PPh3)2][Pt3(mu-I)2(mu-PPh2)2(I1.7Cl0.3)(PPh3)2] x C6H5Cl x 3CH2Cl2 (5A x 5B x C6H5Cl x 3CH2Cl2) and 6 have been established by single crystal X-ray diffraction studies.

The dinuclear chromium complexes [Cr(2)(N,O)(3)Cl(3)] (6) (N,O = 4,4-dimethyl-2-oxazolylmethanolate), [Cr(2)(N,O(Me2))(2)(EtOH)(2)Cl(4)] (7) and [Cr(2)(N,O(Me2))(2)(H(2)O)(2)Cl(4)] (8) (N,O(Me2) = 4,4-dimethyl-2-oxazolyldimethylmethanolate) have been prepared and characterized, including by single-crystal X-ray diffraction. Complex 6 is unsymmetrical, with two chloride ligands terminally bound to one Cr atom, whereas 7 and 8 (in 8 x C(4)H(8)O) which contain two molecules of coordinated ethanol or water, respectively, are centrosymmetric. These chromium complexes are paramagnetic, and the magnetic properties of 6 and 7 in the solid state correspond to antiferromagnetic behaviour, which was confirmed by DFT calculations of their electronic structures. Complexes 6-8 were 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 7 showed 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(-1) in the latter case.

The N,P,N-type ligands bis(2-picolyl)phenylphosphine (), bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine (), bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine () and bis(2-picolyloxy)phenylphosphine () were used to synthesize the corresponding pentacoordinated Ni(ii) complexes [Ni{bis(2-picolyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] () and [Ni{bis(2-picolyloxy)phenylphosphine}Cl(2)] (), respectively. The hexacoordinated iron complexes [Fe{bis(2-picolyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] (), [Fe{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] () and the tetracoordinated complex [Fe{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] (abbreviated [FeCl(2)(NPN(Me2)-N,N)]) were prepared by reaction of FeCl(2).4H(2)O with ligands , respectively. The crystal structures of the octahedral complexes and , 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 (mu-oxo)bis[trichloroferrate(iii)] compensates the doubly positive charge of the complex. The cyclic voltammograms of and showed two reversible redox couples attributed to the reduction of the dianion (Fe(2)OCl(6))(2-) (-0.24 V for and -0.20 V for vs. SCE) and to the oxidation of the Fe(ii) ion of the complex (0.67 V for and 0.52 V for vs. SCE). The cyclic voltammogram of [FeCl(2)(NPN(Me2)-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 , and [FeCl(2)(NPN(Me2)-N,N)] have been evaluated in the catalytic oligomerization of ethylene with AlEtCl(2) or MAO as cocatalyst. The nickel complex proved to be the most active precatalyst in the series, with a turnover frequency (TOF) of 61 800 mol(C(2)H(4)) mol(Ni)(-1) h(-1) with 10 equiv. of AlEtCl(2) and 12 200 mol(C(2)H(4)) mol(Ni)(-1) h(-1) with 200 equiv. of MAO. Precatalysts and were the most selective in butenes, up to 90% with 6 equiv. of AlEtCl(2) and 89% with 2 equiv. of AlEtCl(2), 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 and AlEtCl(2) (up to 31% with 6 equiv.) and with MAO (up to 72% with 200 equiv.). The iron complexes were not significantly active with AlEtCl(2) or MAO as cocatalyst.

The beta-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 [NiPh{Ph2PCH...C(...O)(o-OMeC6H4)}(PPh3)] 13, [NiPh{Ph(t-Bu)PCHC(O)Ph}(PPh3)] 15, [NiPh{(n-Bu)2PCH...C(...O)Ph}(PPh3)] 16 and [NiPh{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 beta-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 alpha to phosphorus and the ether function. The complexes [NiPh{Ph2PCHC(O)Ph}(Py)] 18, [NiPh{Ph(t-Bu)PCHC(O)Ph}(Py)] 19, [NiPh{(n-Bu)2PCH...C(...O)Ph}(Py)] 20, [NiPh{Ph(n-Bu)PCH...C(...O)Ph}(Py)] 21 and [NiPh{Me2PCH...C(...O)Ph}(Py)] 22 have been isolated from the reactions of [Ni(COD)2] and an excess of pyridine with the -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 12700 mol C2H4 (mol Ni)-1 under 30 bar ethylene. When the beta-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.

Cobalt(ii) complexes of the type [CoCl(2)(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 [CoCl(2){Ph(2)PCH(2)ox(Me2)}] (Ph(2)PCH(2)ox(Me2) = 2-[(diphenylphosphanyl)-methyl]-4,4-dimethyl-4,5-dihydro-oxazole) () and the phosphinito-oxazoline complexes [CoCl(2){Ph(2)POCH(2)ox(Me2)}] (Ph(2)POCH(2)ox(Me2) = 1-[4,4-dimethyl-2{1-oxy(diphenylphosphino)-1-methyl}]-4,5-dihydro-oxazole) () and [CoCl(2){Ph(2)POCMe(2)ox(Me2)}] (Ph(2)POCMe(2)ox(Me2) = 1-[4,4-dimethyl-2- [1-oxy(diphenylphosphino)-1-methylethyl]]-4,5-dihydrooxazole) () are mononuclear, the phosphino-oxazoline complexes [CoCl(2){micro-i-Pr(2)PCH(2)ox}](2) (i-Pr(2)PCH(2)ox = 2-[(diisopropyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) () and [CoCl(2){micro-Ph(2)PCH(2)ox}](2) (Ph(2)PCH(2)ox = 2-[(diphenyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) () 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 [CoCl(3){Ph(2)PCH(2)C(O)OCH(2)CMe(2)NH(3)] () 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 yielded the blue N,O-bridged, centrosymmetric dinuclear complex [[upper bond 1 start]CoCl(2){micro-OPPh(2)CH(2)[lower bond 1 start]C[double bond, length as m-dash]N[upper bond 1 end]CMe(2)CH(2)O[lower bond 1 end]}](2) () which contains a 12-membered ring. All these complexes are paramagnetic and their magnetic moments in solution were measured by the Evans method. Complexes were evaluated in the catalytic oligomerisation of ethylene with AlEtCl(2) or methylaluminoxane (MAO) as cocatalysts and provided moderate activities. In the presence of AlEtCl(2) (6-14 equiv.), the selectivities for ethylene dimers were higher than 92% and complex showed the highest turnover frequency with 14 equiv. of AlEtCl(2). When MAO was used as cocatalyst, the catalytic activities were similar to those with AlEtCl(2) but significant amounts of C(6)-C(12) oligomers were produced.

A comparative study of the reactivity of isolobal rhenium and molybdenum carbonylmetallates containing a borole, in [Re(eta5-C4H4BPh)(CO)3]- (2), a boratanaphthalene, in [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (4a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (4b), a boratabenzene, in [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (6) or a dimethylaminocyclopentadienyl ligand, in [Mo(eta5-C5H4NMe2)(CO)3]- (7), toward palladium(II), gold(I), mercury(II) and platinum(II) complexes has allowed an evaluation of the role of these pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal bonded, heterometallic complexes. The new metallate 6 was reacted with [AuCl(PPh3)], and with 1 or 2 equiv. HgCl2, which afforded the new heterodinuclear complexes [Au{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}(PPh3)] (Mo-Au) (10) and [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}Cl] (Hg-Mo) (11) and the heterometallic chain complex [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}2] (Mo-Hg-Mo) (12), respectively. Reactions of the new metallate 7 with HgCl2, trans-[PtCl2(CNt-Bu)2] and trans-[PtCl2(NCPh)2] yielded the heterodinuclear complex [Hg{Mo(eta5-C5H4NMe2)(CO)3}Cl] (Mo-Hg) (15), the heterotrinuclear chain complexes trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(CNt-Bu)2] (Mo-Pt-Mo) (16) and trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(NCPh)2] (Mo-Pt-Mo) (17), the mononuclear complex [Mo(eta5-C5H4NMe2)(CO)3Cl] (18), the lozenge-type cluster [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (19) and the heterodinuclear complex [[upper bond 1 start]Pt{Mo(eta5-C5H4N[upper bond 1 end]Me2)(CO)3}(NCPh)Cl](Mo-Pt) (20), respectively. The complexes 11, 16, 17.2THF, 18 and 20 have been structurally characterized by X-ray diffraction and 20 differs from all other compounds in that the dimethylaminocyclopentadienyl ligand forms a bridge between the metals.