Synthesis of nickel complexes with bidentate N,O-type ligands and application in the catalytic oligomerization of ethylene

The dinuclear complexes [Ni(micro-Cl){(4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol}](2)Cl(2) and [Ni(micro-Cl){(pyridin-2-yl)methanol}](2)Cl(2) 16 have been synthesized in high yields by reaction of NiCl(2) 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 NiCl(2) with 3 mol. equiv. of 15 afforded in high yield the mononuclear, octahedral mer-[Ni{(pyridin-2-yl)methanol}(3)Cl(2)] 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.C(6)H(12) and in 16.3CH(2)Cl(2) and of the mononuclear, octahedral complex 18 in 18.CH(2)Cl(2) 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 AlEtCl(2) (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 AlEtCl(2) proved to be the most active system with a turnover frequency (TOF) up to 187 500 C(2)H(4) (mol Ni h)(-1). Complex 16 with 200 equiv. of MAO was also the most active, with TOF up to 104 300 C(2)H(4) (mol Ni h)(-1) under 30 bar of ethylene.     

A phosphino-oxazoline ligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: catalytic ethylene oligomerization

The Pd(II) complex [PdCl(2)(1)] [1 = ({oxazolin-2-yl}methyl)diphenylphosphine] was obtained by the 1:1 reaction of 1 with [PdCl(2)(NCPh)(2)]. Although this neutral complex is stable in the solid-state and in solution, it reacts with the dinuclear complex [CoCl(2)(μ-1)](2) to afford the heterometallic zwitterionic complex [{PdCl(1)}(+)(μ-1)(CoCl(3))(-)] (2). Under inert atmosphere, two equivalents of 1 reacted with [NiCl(2)(dme)] to give trans-[NiCl(2)(1)(2)] (3) in CH(2)Cl(2) but cis-[NiCl(2)(1)(2)] (4) in CHCl(3). When the latter reaction was performed in air, trans-[NiCl(2)(5)(2)] (6) [5 = ({oxazolin-2-yl}methyl)diphenylphosphine oxide] was obtained. All metal complexes, 2, 3, 4 and 6, have been structurally characterized by X-ray diffraction. Complexes 3, 4 and 6 have been evaluated as precatalysts for ethylene oligomerisation in the presence of AlEtCl(2) as cocatalyst. Complexes 3 and 6 yielded a turnover frequency (TOF) of 60,700 and 62,600 mol of C(2)H(4)/((mol of Ni)·h), respectively, in the presence of 10 equiv. of AlEtCl(2). In the presence of only 6 equiv. of cocatalyst, these Ni complexes yielded TOF values of 41,500 and 58,000 mol of C(2)H(4)/((mol of Ni)·h), respectively.     

Dinuclear nickel complexes with bidentate N,O ligands: synthesis, structure, and catalytic oligomerization of ethylene

The new dicationic dinuclear complexes [Ni(micro-Cl)(2)(N,OH)(2)]Cl(2) (11, N,OH = 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-propan-2-ol; 12, N,OH = 2-pyridin-2-yl-propan-2-ol) were prepared in good yields and evaluated as precatalyts in the oligomerization of ethylene, using MAO or AlEtCl(2) as cocatalyst. These paramagnetic complexes were characterized by single-crystal X-ray diffraction in the solid state and in solution with the help of the Evans method, which revealed agreement between the octahedral coordination spheres found in solution and in the solid state. The N donor atoms of each chelating ligand are in mutual cis position, and the OH donors are mutually trans situated. Selectivities for 1-butene within the C(4) fraction of 61% (11) and 58% (12) were observed in the presence of 200 equiv of MAO, but better turnover frequencies (28 300 (11) and 20 400 (12) mol of C(2)H(4)/(mol of Ni.h)) were obtained when 800 equiv of MAO was used. In the presence of 6 equiv of AlEtCl(2), the activities were considerably increased, up to 174 300 (11) and 97 100 (12) mol of C(2)H(4)/(mol of Ni.h), and the selectivity for C(4) olefins was 70% and 64%, respectively.     

The beta-dialdiminato ligand [{N(C6H3Pri(2)-2,6)C(H)}2CPh]-: the conjugate acid and Li, Al, Ga and In derivatives

The synthesis of the following crystalline complexes is described: [Li(L)(thf)2] (), [Li(L)(tmeda)] (), [MCl2(L)] [M=Al (), Ga ()], [In(Cl)(L)(micro-Cl)2Li(OEt2)2] (), [In(Cl)(L){N(H)C6H3Pri(2)-2,6}] (), [In(L){N(H)C6H3Pri(2)-2,6}2] (), [{In(Cl)(L)(micro-OH)}2] (), [L(Cl)In-In(Cl)(L)] () (the thf-solvate, the solvate-free and the hexane-solvate), [{In(Cl)L}2(micro-S)] () and [InCl2(L)(tmeda)] () ([L]-=[{N(C6H3Pri(2)-2,6)C(H)}2CPh]-). From H(L) (), via Li(L) in Et2O, and thf, tmeda, AlCl3, GaCl3 or InCl3 there was obtained , , , or , respectively in excellent yield. Compound was the precursor for each of , and [{InCl3(tmeda)2{micro-(OSnMe2)2}}] () by treatment with one () or two () equivalents of K[N(H)(C6H3Pri(2)-2,6)], successively Li[N(SiMe3)(C6H3Pri(2)-2,6)] and moist air (), Na in thf (), tmeda (), or successively tmeda and Me3SnSnMe3 (). Crystals of (with an equivalent of In) and were obtained from InCl or thermolysis of [In(Cl)(L){N(SiMe3)(C6H3Pri(2)-2,6)}] () {prepared in situ from and Li[N(SiMe3)(C6H3Pri(2)-2,6)] in Et2O}, respectively. Compound was obtained from a thf solution of and sulfur. X-Ray data for crystalline , , , , , and are presented. The M(L) moiety in each (not the L-free ) has the monoanionic L ligated to the metal in the N,N'-chelating mode. The MN1C1C2C3N2 six-membered M(L) ring is pi-delocalised and has the half-chair (, and ) or boat (, and ) conformation.     

Chelating N-pyrrolylphosphino-N'-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis

Two families of variously-substituted N-pyrrolylphosphino-N'-arylaldimine ligands, 2-(aryl-N=CH)C4H3N-PR2 {R=Ph; R=Pri2N}, have been prepared from the corresponding pyrrolylaldimines . The donor characteristics/basicity of P-N-chelating and have been assessed using a combination of 31P{1H} NMR and IR spectroscopies through study of the magnitudes of 1JSeP for the phosphorus(V) selenides and , and measurement of nu(CO) for the complexes [RhCl(CO)(-kappa2-P,N)], respectively. The synthesis of the palladium(II) complexes [PdCl2(-kappa2-P,N)] was readily achieved from reaction of or with [PdCl2(MeCN)2] in CH2Cl2. X-Ray crystallographic studies of and confirm the chelating nature of the P-N ligands, which adopt a distorted 'envelope' conformation, and highlight the potentially significant steric demands of these metal scaffolds. Reaction of equimolar quantities of with [NiBr2(DME)] in MeCN afforded [NiBr2(-kappa2-P,N)], while the same reaction undertaken in CH2Cl2 with gave rise to the homoleptic bis(pyrrolatoimine) derivative [Ni{2-(mes-N=CH)C4H3N}2] in 45% yield, following P-N bond cleavage. Complex was characterised in the solid-state by X-ray crystallography. No identifiable metal-containing complexes could be obtained on reaction of with a variety of sources of Ni(II). The palladium dichloride complexes and proved inactive in combination with MAO or EtAlCl2 for ethylene polymerisation, and with methanesulfonic acid for CO/ethylene co-polymerisation. Contrastingly, the nickel complexes in combination with 4.5 eq. EtAlCl2 catalysed the formation of butenes and hexenes with moderate activity from ethylene at 1 bar.     

Mono- and dinuclear cobalt complexes with chelating or bridging bidentate P,N phosphino- and phosphinito-oxazoline ligands: synthesis, structures and catalytic ethylene oligomerisation

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.     

Nickel complexes with new bidentate P,N phosphinitooxazoline and -pyridine ligands: application for the catalytic oligomerization of ethylene

The phosphinitooxazoline 4,4-dimethyl-2-[1-oxy(diphenylphosphine)-1-methylethyl]-4,5-dihydrooxazole (9), the corresponding phosphinitopyridine ligands 2-ethyl-[1'-methyl-1'-oxy(diphenylphosphino)]pyridine (11) and 2-ethyl-6-methyl-[1'-methyl-1'-oxy(diphenylphosphino)]pyridine (12), which have a one-carbon spacer between the phosphinite oxygen and the heterocycle, and the homologous ligand 2-propyl-[2'-methyl-2'-oxy(diphenylphosphino)]pyridine (13), with a two-carbon spacer, were prepared in good yields. The corresponding mononuclear [NiCl(2)(P,N)] complexes 14 (P,N = 9), 15 (P,N = 11), and 16 (P,N = 12) and the dinuclear [NiCl(micro-Cl)(P,N)](2) 17 (P,N = 13) Ni(II) complex were evaluated in the catalytic oligomerization of ethylene. These four complexes were characterized by single-crystal X-ray diffraction in the solid state and in solution with the help of the Evans method, which indicated differences between the coordination spheres in the solution and the solid state. In the presence of methylalumoxane (MAO) or AlEt(3), only the decomposition of the Ni complexes was observed. However, complexes 14-17 provided activities up to 50000 mol C(2)H(4)/(mol Ni).h (16 and 17) in the presence of only 6 equiv of AlEtCl(2). The observed selectivities for ethylene dimers were higher than 91% (for 14 or 15 in the presence of only 1.3 equiv of AlEtCl(2)). The activities for 14-17 were superior to that of [NiCl(2)(PCy(3))(2)], a typical dimerization catalyst taken as a reference. The selectivities of the complexes 14-17 for ethylene dimers and alpha-olefins were the same order of magnitude. From the study of the phosphinite 9/AlEtCl(2) system, we concluded that in our case ligand transfer from the nickel atom to the aluminum cocatalyst is unlikely to represent an activation mechanism.     

Nickel and iron complexes with oxazoline- or pyridine-phosphonite ligands; synthesis, structure and application for the catalytic oligomerisation of ethylene

The bis(oxazolinyl)phenylphosphonite ligand (bis(4,4-dimethyl-2-(1-hydroxy-1-methylethyl)-4,5-dihydrooxazole)phenylphosphonite, NOPONMe2)) and the new pyridine-phosphonite ligand (2-ethyl(1'-methyl-1-hydroxy)pyridine-6H-dibenz[c,e][1,2]oxaphosphorin) have been used for the preparation of the mononuclear complexes [NiCl2(NOPONMe2)] 18 and [NiCl2(6)2] 19, respectively, which catalyze the oligomerisation of ethylene with activities up to 57300 mol C2H4 mol Ni(-1) h(-1) (19 in the presence of only 6 equivalents of AlEtCl2). The selectivities for C4 dimers were as high as 90% (18 in the presence of only 2 equivalents of AlEtCl2) with selectivities for 1-butene of 21-22% of the C4 fraction. In the presence of 400 or 800 equivalents of MAO as cocatalyst, complex 19 yielded turnover frequencies of 7400 mol C2H4 mol Ni(-1) h(-1) and 13200 mol C2H4 mol Ni(-1) h(-1), respectively. The selectivities for 1-butene and ethylene dimers were similar to those obtained with AlEtCl2. The fact that 19 with a cyclic phosphonite moiety leads to higher activities and selectivities than 18 which contains an acyclic phosphonite group underlines the importance of the ligand on the catalytic properties of its metal complex. An unprecedented dinuclear iron complex [FeCl2(4,4-dimethyl-2-[(1-hydroxy-1-methyl)ethyl]-4,5-dihydrooxazolate)]2 20 was also obtained which contains two pentacoordinated metal centers coordinated by a bridging-chelating oxazoline-alcoholate. Complexes 18-20 are paramagnetic in solution, as determined by the Evans method.     

Iron-arylimide clusters [Fe(m)()(NAr)(n)Cl(4)](2)(-) (m,n = 2, 2; 3, 4; 4, 4) from a ferric amide precursor: synthesis,characterization, and comparison to Fe-S chemistry

Tetrahedral FeCl[N(SiMe(3))(2)](2)(THF) (2), prepared from FeCl(3) and 2 equiv of Na[N(SiMe(3))(2)] in THF, is a useful ferric starting material for the synthesis of weak-field iron-imide (Fe-NR) clusters. Protonolysis of 2 with aniline yields azobenzene and [Fe(2)(mu-Cl)(3)(THF)(6)](2)[Fe(3)(mu-NPh)(4)Cl(4)] (3), a salt composed of two diferrous monocations and a trinuclear dianion with a formal 2 Fe(III)/1 Fe(IV) oxidation state. Treatment of 2 with LiCl, which gives the adduct [FeCl(2)(N(SiMe(3))(2))(2)](-) (isolated as the [Li(TMEDA)(2)](+) salt), suppresses arylamine oxidation/iron reduction chemistry during protonolysis. Thus, under appropriate conditions, the reaction of 1:1 2/LiCl with arylamine provides a practical route to the following Fe-NR clusters: [Li(2)(THF)(7)][Fe(3)(mu-NPh)(4)Cl(4)] (5a), which contains the same Fe-NR cluster found in 3; [Li(THF)(4)](2)[Fe(3)(mu-N-p-Tol)(4)Cl(4)] (5b); [Li(DME)(3)](2)[Fe(2)(mu-NPh)(2)Cl(4)] (6a); [Li(2)(THF)(7)][Fe(2)(mu-NMes)(2)Cl(4)] (6c). [Li(DME)(3)](2)[Fe(4)(mu(3)-NPh)(4)Cl(4)] (7), a trace product in the synthesis of 5a and 6a, forms readily as the sole Fe-NR complex upon reduction of these lower nuclearity clusters. Products were characterized by X-ray crystallographic analysis, by electronic absorption, (1)H NMR, and M?ssbauer spectroscopies, and by cyclic voltammetry. The structures of the Fe-NR complexes derive from tetrahedral iron centers, edge-fused by imide bridges into linear arrays (5a,b; 6a,c) or the condensed heterocubane geometry (7), and are homologous to fundamental iron-sulfur (Fe-S) cluster motifs. The analogy to Fe-S chemistry also encompasses parallels between Fe-mediated redox transformations of nitrogen and sulfur ligands and reductive core conversions of linear dinuclear and trinuclear clusters to heterocubane species and is reinforced by other recent examples of iron- and cobalt-imide cluster chemistry. The correspondence of nitrogen and sulfur chemistry at iron is intriguing in the context of speculative Fe-mediated mechanisms for biological nitrogen fixation.     

Dinuclear nickel and palladium complexes with bridging 2,5-diamino-1,4-benzoquinonediimines: synthesis, structures, and catalytic oligomerization of ethylene

Dinuclear, divalent acetylacetonato (acac) complexes of the type [M(acac){mu-C6H2(--NR)4}M(acac)] (M = Ni, Pd) have been prepared by the reaction of the corresponding bis(acac) metal precursor with 2,5-diamino-1,4-benzoquinonediimines C6H2(NHR)2(=NR)2 (4a, R = CH2-t-Bu; 4b, R = CH2Ph; 4c, R = Ph), which are metalated and become bridging ligands, also like in the complex [(C8H11)Pt{mu-C6H2(--NCH2-t-Bu)4}Pt(C8H11)] (6) obtained by the reaction of 4a with [PtCl2(COD)]. The complexes were fully characterized, including by X-ray diffraction for [Ni(acac){mu-C6H2(--NCH2Ph)4}Ni(acac)] (9b) and [Pd(acac){mu-C6H2(--NCH2-t-Bu)4}Pd(acac)] (10a). The coordination geometry around the metal ions is square-planar, and a complete electronic delocalization of the quinonoid pi system occurs between the metal centers over the two N--C--C--C--N halves of the ligand. The nature of the N substituent explains the differences between the supramolecular stacking arrangements found for [Ni(acac){mu-C6H2(--NR)4}Ni(acac)] (9a; R = CH2-t-Bu; 9b, R = CH2Ph). The Ni complexes were evaluated as catalyst precursors for ethylene oligomerization in the presence of AlEtCl(2) or MAO as the cocatalyst, in particular in order to study possible cooperative effects resulting from electronic communication between the metal centers and to examine the influence of the N substituent on the activity and selectivity. These catalysts afforded mostly ethylene dimers and trimers.     

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 -.     

Transition metal complexes bearing 2,6-bis(imino)pyridyl:Synthesis, structure, ethylene polymerization/oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyri-dine}MCI2 [M=Fe(Ⅱ) (2), Co(Ⅱ) (3), Ni(Ⅱ) (4), Cu(Ⅱ) (5), Zn(Ⅱ) (6)] have been synthesized. At 25℃, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(Ⅱ), Co(Ⅱ) catalysts can reach 4.02×106 g/mol-Fehatm for ethylene polymerization and 3.98×105 g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.     

Ligand influence on the formation of P/Se semiconductor materials from metal-organic complexes

The complexes [Ni{(SeP(i)Pr(2))(2)N}(2)] (), [Ni(Se(2)P(i)Pr(2))(2)] (), and [Co(Se(2)P(i)Pr(2))(2)] () were synthesised and the X-ray single crystal structures of () and () were determined. Thin films of nickel selenide, cobalt selenide and cobalt phosphide have been deposited by the chemical vapour deposition method using imidodiselenophosphinato-nickel(ii) (), -cobalt(ii) [Co{(SeP(i)Pr(2))(2)N}(2)] (), diselenophosphinato-nickel(ii) (), -cobalt(ii) () and diselenocarbamato-nickel(ii) [Ni(Se(2)CNEt(2))(2)] (), and -cobalt(iii) [Co(Se(2)CNEt(2))(3)] () precursors.     

Sterically variable dizinc complexes bearing bis(iminopyridyl)phenolate ligands: synthesis, structures and reactivity studies

A series of chiral dizinc complexes of the type [(2,6-{ArN=C(Me)C5H3N}2C6H3O)Zn2(micro-Cl)Cl2] [Ar=2,6-i-Pr2C6H3 (), 2,6-Me2C6H3 (), 2,4,6-Me3-C6H2 (), 2,4-Me2C6H3 ()] can be conveniently prepared in good yield by the template reaction of 2,6-{O=C(Me)C5H3N}2C6H3OH with an excess of the corresponding aniline and two equivalents of zinc dichloride in n-BuOH at elevated temperature. Alternatively, the pro-ligands, 2,6-{(ArN=C(Me)C5H3N}2C6H3OH [Ar=2,6-i-Pr2C6H3 (L1-H), 2,6-Me2C6H3 (L2-H), 2,4,6-Me3C6H2 (L3-H), 2,4-Me2C6H3 (L4-H)], can be isolated and then treated with two equivalents of zinc dichloride to afford . Interaction of with two equivalents of NaOAc in the presence of TlBF4 gives the diacetate-bridged salt [(L1)Zn2(micro-OAc)2](BF4) () while with Nadbm (dbm=dibenzoylmethanato) the bis(dbm)-chelated salt [(L1)Zn2(dbm)2](BF4) () is obtained. Hydrolysis occurs on reaction of with TlOEt to furnish [(L1)Zn2(micro-OH)Cl2] () as the only isolable product. Conversely, reaction of with Tlhp (hp=2-pyridonate) affords the neutral bis(pyridonate)-bridged trimetallic complex [(L1)Zn3(micro-hp)2Cl3] () as the major product along with as the minor one. Complex and mixtures of / act as modest activators for the ring-opening polymerisation of epsilon-caprolactone. Single crystal X-ray diffraction studies have been performed on , , , , and reveal Zn...Zn separations in the range: 3.069(4)-4.649(6) A.     

Syntheses, structures and reactions of a series of beta-diketiminatoyttrium compounds

This paper describes the synthesis and selected reactions of a series of crystalline mono(beta-diiminato)yttrium chlorides , , , , , , and . The X-ray structure of each has been determined, as well as of [YCl()(2)] (), [Y()(2)OBu(t)] () and [Y{CH(SiMe(3))(2)}(thf)(mu-Cl)(2)Li(OEt(2))(2)(mu-Cl)](2) (). The N,N'-kappa(2)-beta-diiminato ligands were [{N(R)C(Me)}(2)CH](-) [R = C(6)H(4)Pr(i)-2 (); R = C(6)H(4)Bu(t)-2 (); R = C(6)H(3)Pr(i)(2)-2,6 ()], [{N(SiMe(3))C(Ph)}(2)CH)](-) () and [{N(C(6)H(3)Pr(i)(2)-2,6)C(H)}(2)CPh](-) (). Equivalent portions of Li[L(x)] and YCl(3) in Et(2)O under mild conditions yielded [Y(mu-Cl)(L(x))(mu-Cl)(2)Li(OEt(2))(2)](2) [L(x) = () or ()] and [Y(mu-Cl)()(mu-Cl)Li(OEt(2))(2)(mu-Cl)](2) () or its thf (instead of Et(2)O) equivalent . Each of the Li(OEt(2))(2)Cl(2) moieties is bonded in a terminal () or bridging () mode with respect to the two Y atoms; the difference is attributed to the greater steric demand of than or . Under slightly more forcing conditions, YCl(3) and Li() (via) gave the lithium-free complex [YCl(2)()(thf)(2)] (). Two isoleptic compounds and (having in place of in , and , respectively) were obtained from YCl(3) and an equivalent portion of K[] and Na[], respectively; under the same conditions using Na[], the unexpected product was [YCl()(2)] () (i.e. incorporating only one half of the YCl(3)). A further unusual outcome was in the formation of from and 2 Li[CH(SiMe(3))(2)]. Compound [Y(){N(H)C(6)H(3)Pr(i)(2)-2,6}(thf)(mu(3)-Cl)(2)K](2).4Et(2)O (), obtained from and K[N(H)C(6)H(3)Pr(i)(2)-2,6], is noteworthy among group 3 or lanthanide metal (M) compounds for containing MClKCl (M = Y) moieties.     

Transition metal induced derivatisations resulting in novel coordination behaviour of bis(oxamato) ligands

Two mononuclear bis(oxamato) complexes with the formula [nBu4N]2[M(2,3-acbo)] (M=Ni (), Cu (), with acbo=anthra-9,10-chinone-2,3-bis(oxamato) have been synthesized starting from symmetric diethyl N,N'-anthra-9,10-chinone-2,3-bis(oxamate) (, 2,3-acboH2Et2). The crystal structures of and have been determined, verifying that the transition metal ions are eta4(kappa2N,kappa2O) coordinated by the [2,3-acbo]4- ligands. Using the asymmetric diethyl N,N'-anthra-9,10-chinone-1,2-bis(oxamate) (, 1,2-acboH2Et2) leads, under otherwise identical reaction conditions, to the novel bis(oxamato) complex [(n)Bu4N]2[Ni(1,2-acbo)] () whereby in the case of Cu(II) the derivate [nBu4N]2[Cu(aibo)2] () (aibo=anthra[1,2-d]-(imidazole-2-carboxylato)-6,11-dione) has been obtained. The crystal structures of and have been determined, displaying that the Ni(II) ion of is eta4(kappa2N,kappa2O) coordinated by the [1,2-acbo]4- ligand. The Cu(II) ion of is coordinated by two [aibo]2- ligands, giving rise to an approximately square-planar trans-bis(aibo-N,O) arrangement. Using the symmetric diethyl N,N'-4,5-dinitro-o-phenylene-bis(oxamate) (, niboH2Et2), possessing strongly electron withdrawing NO2-groups, leads under otherwise identical reaction conditions to the bis(oxamato) complex [nBu4N]2[Ni(nibo)] (), whereby in the case of Cu(II) the derivate [nBu4N]2[Cu(niqo)2] () (niqo=7,8-dinitro-2,3-quinoxalinedionato) has been obtained. The crystal structures of and have been determined, ensuring that the Ni(II) ion of is eta(4)(kappa2N,kappa2O) coordinated by the [nibo]4- ligand. The Cu(II) ion of is coordinated by four oxygen atoms of two [niqo]2- ligands, giving rise to an approximately square-planar coordination geometry.     

Acetonitrile-facilitated reductive dimerization of TCNE to octacyanobutanediide, [C4(CN)8]2-, by Iron(II) chloride

The redox properties of MCl2 (M=Mn, Fe, Co) acetonitrile solvates were electrochemically and spectroscopically characterized. The three voltammogram waves at 0.86, 0.48, and 0.21 V versus SCE for FeCl(2) dissolved in MeCN are assigned as one-electron reduction potentials for [Fe(II)Cl(x)(NCMe)4-x]2-x (1相似文献   

SHOP-type nickel complexes with alkyl substituents on phosphorus, synthesis and catalytic ethylene oligomerization

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.     

Synthesis and structure of two new (guanidinate)boron dichlorides and their attempted conversion to boron(I) derivatives

To test the feasibility of the guanidinate architecture for the support of boron(i) carbene analogues the energy gap between the singlet and triplet states of the model compound, [Me(2)NC{N(Ph)}(2)B:] (), has been probed by both DFT and second order M?ller-Plesset (MP2) methods. The singlet state is calculated to be more stable than the triplet state by between 6.0 and 10.1 kcal mol(-1). The new (guanidinate)boron dichlorides [Ph(2)NC{N(Mes)(2)]BCl(2) () and [Ph(2)NC{N(Dipp)(2)]BCl(2) () have been prepared and characterized by single-crystal X-ray diffraction. Attempts to reduce and to the corresponding boron(i) species were not successful.     

Coordination site-dependent cation binding and multi-responsible redox properties of Janus-head metalloligand, [Mo(V)(1,2-mercaptophenolato)3

The redox-active fac-[Mo(V)(mp)(3)](-) (mp: o-mercaptophenolato) bearing asymmetric O- and S-cation binding sites can bind with several kinds of metal ions such as Na(+), Mn(II), Fe(II), Co(II), Ni(II), and Cu(I). The fac-[Mo(V)(mp)(3)](-) metalloligand coordinates to Na(+) to form the contact ion pair {Na(+)(THF)(3)[fac-Mo(V)(mp)(3)]} (1), while a separated ion pair, n-Bu(4)N[fac-Mo(V)(mp)(3)] (2), is obtained by exchanging Na(+) with n-Bu(4)N(+). In the presence of asymmetric binding-sites, the metalloligand reacts with Mn(II)Cl(2)·4H(2)O, Fe(II)Cl(2)·4H(2)O, Co(II)Cl(2)·6H(2)O, and Ni(II)Cl(2)·6H(2)O to afford UV-vis-NIR spectra, indicating binding of these guest metal cations. Especially, for the cases of the Mn(II) and Co(II) products, trinuclear complexes, {M(H(2)O)(MeOH)[fac-Mo(V)(mp)(3)](2)}·1.5CH(2)Cl(2) (3·1.5CH(2)Cl(2) (M = Mn(II)), 4·1.5CH(2)Cl(2) (M = Co(II))), are successfully isolated and structurally characterized where the M are selectively bound to the hard O-binding sites of the fac-[Mo(V)(mp)(3)](-). On the other hand, a coordination polymer, {Cu(I)(CH(3)CN)[mer-Mo(V)(mp)(3)]}(n) (5), is obtained by the reaction of fac-[Mo(V)(mp)(3)](-) with [Cu(I)(CH(3)CN)(4)]ClO(4). In sharp contrast to the cases of 1, 3·1.5CH(2)Cl(2), and 4·1.5CH(2)Cl(2), the Cu(I) in 5 are selectively bound to the soft S-binding sites, where each Cu(I) is shared by two [Mo(V)(mp)(3)](-) with bidentate or monodentate coordination modes. The second notable feature of 5 is found in the geometric change of the [Mo(V)(mp)(3)](-), where the original fac-form of 1 is isomerized to the mer-[Mo(V)(mp)(3)](-) in 5, which was structurally and spectroscopically characterized for the first time. Such isomerization demonstrates the structural flexibility of the [Mo(V)(mp)(3)](-). Spectroscopic studies strongly indicate that the association/dissociation between the guest metal ions and metalloligand can be modulated by solvent polarity. Furthermore, it was also found that such association/dissociation features are significantly influenced by coexisting anions such as ClO(4)(-) or B(C(6)F(5))(4)(-). This suggests that coordination bonds between the guest metal ions and metalloligand are not too static, but are sufficiently moderate to be responsive to external environments. Moreover, electrochemical data of 1 and 3·1.5CH(2)Cl(2) demonstrated that guest metal ion binding led to enhance electron-accepting properties of the metalloligand. Our results illustrate the use of a redox-active chalcogenolato complex with a simple mononuclear structure as a multifunctional metalloligand that is responsive to chemical and electrochemical stimuli.