Novel nucleophilic reactivity of disulfido ligands coordinated parallel to M-M (M = Rh, Ir) bonds

Reaction of trans-[(MCp)(2)(mu-CH(2))(2)Cl(2)] (M = Rh, Ir; Cp = eta(5)-C(5)Me(5)) with Li(2)S(2) afforded the disulfido complexes [(MCp)(2)(mu-CH(2))(2)(mu-S(2)-S:S')] which were easily oxidized by O(2) to give the oxygenated complexes [(MCp)(2)(mu-CH(2))(2)(mu-SSO(2)-S:S')]. Although [(RhCp)(2)(mu-CH(2))(2)(mu-S(2)-S:S')] gave a complicated mixture when reacted with CH(2)Cl(2) or CHCl(3), [(IrCp)(2)(mu-CH(2))(2)(mu-S(2)-S:S')] reacted with both CH(2)Cl(2) and CHCl(3) to give the dithioformato complex [(IrCp)(2)(mu-CH(2))(2)(mu-S(2)CH-S:S')]Cl and the cyclotetrasulfido complex [((IrCp)(2)(mu-CH(2))(2))(2)(mu-S(4)-S:S':S":S"')]Cl(2). The oxygenated complexes [(RhCp)(2)(mu-CH(2))(2)(mu-SSO(2)-S:S')] reacted with hydrocarbyl halides to afford bridging hydrocarbyl thiolato complexes accompanied by the generation of SO(2) gas. These complexes have been characterized by NMR spectroscopy, ESI-MS, and X-ray diffraction.     

Probing the effects of ligand structure on activity and selectivity of Cr(III) complexes for ethylene oligomerisation and polymerisation

A series of distorted octahedral Cr(III) complexes containing tridentate S-, S/O- or N-donor ligands comprised of three distinct architectures: facultative {S(CH(2)CH(2)SC(10)H(21))(2) (L(1)) and O(CH(2)CH(2)SC(10)H(21))(2) (L(2))}, tripodal {MeC(CH(2)S(n)C(4)H(9))(3) (L(3)), MeC(CH(2)SC(10)H(21))(3) (L(4))} and macrocyclic {(C(10)H(21))[9]aneN(3) (L(5)), (C(10)H(21))(3)[9]aneN(3) (L(6)), with [9]aneN(3)=1,4,7-triazacyclononane} are reported and characterised spectroscopically. Activation of [CrCl(3)(L)] with MMAO produces very active ethylene trimerisation, oligomerisation and polymerisation catalysts, with significant dependence of the product distribution upon the ligand type present. The properties of the parent [CrCl(3)(L)] complexes are probed by cyclic voltammetry, UV-visible, EPR, EXAFS and XANES measurements, and the effects upon activation with Me(3)Al investigated similarly. Treatment with excess Me(3)Al leads to substitution of Cl ligands by Me groups, generation of an EPR silent Cr species (consistent with a change in the oxidation state of the Cr to either Cr(II) or Cr(IV)) and substantial dissociation of the neutral S and S/O-donor ligands.     

Insertion, reduction, and carbon-carbon coupling induced by monomeric aluminum hydride compounds bearing substituted pyrrolyl ligands

A monomeric aluminum hydride complex bearing substituted pyrrolyl ligands, AlH[C(4)H(3)N(CH(2)NMe(2))-2](2) (1), was synthesized and structurally characterized. To further confirm the presence of Al--H bonds, the compound AlD[C(4)H(3)N(CH(2)NMe(2))-2](2) ([D]1) was synthesized by reacting LiAlD(4) with [C(4)H(4)N(CH(2)NMe(2))-2]. Compound 1 and [D]1 react with phenyl isothiocyanate yielding Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCHNPh] (2) and Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCDNPh] ([D]2) by insertion. The reactions of 1 with 9-fluorenone and benzophenone generated the unusual aluminum alkoxide complexes 3 and 4, respectively, through intramolecular proton abstraction and C-C coupling. A mechanistic study shows that 9-fluorenone coordinates to [D]1 and releases one equivalent of HD followed by C-C coupling and hydride transfer to yield the final product. Reduction of benzil with 1 affords aluminum enediolate complex 5 in moderate yield. Mechanistic studies also showed that the benzil was inserted into the aluminum hydride bond of [D]1 through hydroalumination followed by proton transfer to generate the final product [D]5. All new complexes have been characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography.     

Synthetic and structural studies on new diiron azadithiolate (ADT)-type model compounds for active site of [FeFe]hydrogenases

A series of new diiron azadithiolate (ADT) complexes (1-8), which could be regarded as the active site models of [FeFe]hydrogenases, have been synthesized starting from parent complex [(μ-SCH(2))(2)NCH(2)CH(2)OH]Fe(2)(CO)(6) (A). Treatment of A with ethyl malonyl chloride or malonyl dichloride in the presence of pyridine afforded the malonyl-containing complexes [(μ-SCH(2))(2)NCH(2)CH(2)O(2)CCH(2)CO(2)Et]Fe(2)(CO)(6) (1) and [Fe(2)(CO)(6)(μ-SCH(2))(2)NCH(2)CH(2)O(2)C](2)CH(2) (2). Further treatment of 1 and 2 with PPh(3) under different conditions produced the PPh(3)-substituted complexes [(μ-SCH(2))(2)NCH(2)CH(2)O(2)CCH(2)CO(2)Et]Fe(2)(CO)(5)(PPh(3)) (3), [(μ-SCH(2))(2)NCH(2)CH(2)O(2)CCH(2)CO(2)Et]Fe(2)(CO)(4)(PPh(3))(2) (4), and [Fe(2)(CO)(5)(PPh(3))(μ-SCH(2))(2)NCH(2)CH(2)O(2)C](2)CH(2) (5). More interestingly, complexes 1-3 could react with C(60) in the presence of CBr(4) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) via Bingel-Hirsch reaction to give the C(60)-containing complexes [(μ-SCH(2))(2)NCH(2)CH(2)O(2)CC(C(60))CO(2)Et]Fe(2)(CO)(6) (6), [Fe(2)(CO)(6)(μ-SCH(2))(2)NCH(2)CH(2)O(2)C](2)C(C(60)) (7), and [(μ-SCH(2))(2)NCH(2)CH(2)O(2)CC(C(60))CO(2)Et]Fe(2)(CO)(5)(PPh(3)) (8). The new ADT-type models 1-8 were characterized by elemental analysis and spectroscopy, whereas 2-4 were further studied by X-ray crystallography and 6-8 investigated in detail by DFT methods.     

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.     

Investigations on the electronic effects of the peripheral 4'-group on 5-(4'-substituted)phenylazo-8-hydroxyquinoline ligands: zinc and aluminium complexes

A new series of 5-(4'-substituted)phenylazo-8-hydroxyquinolines (H[L-R]; R = N(CH(3))(2), C(2)H(5), n-C(4)H(9), C(CH(3))(3), H, and F, ) has been prepared and the corresponding Zn[L-R](2) (1a-6a) and Al[L-R](3) (1b-6b) complexes successfully synthesized. These compounds have been studied in order to design new molecular materials with enhanced electron transport properties. The obtained species have been extensively characterized by absorption and emission spectra and by cyclic voltammetric measurements. Experimental and computational results show that the Zn[L-N(CH(3))(2)].2H(2)O (1a) and Al[L-N(CH(3))(2)](1b) complexes only feature luminescence (at 620 and 600 nm), respectively. The unique effects, which are induced by the N=N-C(6)H(4)-N(CH(3))(2) group, are further proved by a reversible electron transfer process detected by cyclic voltammetry. These outcomes, discussed on the basis of theoretical calculations performed on the (H[L-N(CH3)2])-, H[L-N(CH3)2] and (H[L-N(CH3)(2)])+ species, suggest that metal complexes formed by 5-(4'-N,N-dimethylamino)phenylazo-8-hydroxyquinoline should be considered as electron transport materials suitable for applications in photonic devices.     

Deoligomerization by cocomplexation: syntheses and structures of aluminum-calcium alkoxides and aryloxides

Reactions of oligomeric "Ca(dbbfo)2" and Ca9(CH3OCH2CH2O)18(CH3OCH2CH2OH)2 with Al(CH3)3 in toluene gave tetranuclear heterobimetallic [Ca(mu-dbbfo){(mu-dbbfo)(mu-CH3)Al(CH3)2}]2 (71%) and polymeric Ca{(mu-CH3OCH2CH2O)(mu-CH3)Al(CH3)2}2 (86%). The latter can be obtained as monomeric THF adduct Ca{(mu-CH3OCH2CH2O)Al(CH3)3}2(THF)2 (78%) when a mixture of solvents is used. The results, including an initial L-lactide polymerization test, are discussed in the context of calcium alkoxo cluster degradation in solution.     

Syntheses, structures, and reactivity of new pentamethylcyclopentadienyl-rhodium(III) and -iridium(III) 4-acyl-5-pyrazolonate complexes

New [CpM(Q)Cl] complexes (M = Rh or Ir, Cp = pentamethylcyclopentadienyl, HQ = 1-phenyl-3-methyl-4R(C=O)-pyrazol-5-one in general, in detail HQ(Me), R = CH(3); HQ(Et), R = CH(2)CH(3); HQ(Piv), R = CH(2)-C(CH(3))(3); HQ(Bn), R = CH(2)-(C(6)H(5)); HQ(S), R = CH-(C(6)H(5))(2)) have been synthesized from the reaction of [CpMCl(2)](2) with the sodium salt, NaQ, of the appropriate HQ proligand. Crystal structure determinations for a representative selection of these [CpM(Q)Cl] compounds show a pseudo-octahedral metal environment with the Q ligand bonded in the O,O'-chelating form. In each case, two enantiomers (S(M)) and (R(M)) arise, differing only in the metal chirality. The reaction of [CpRh(Q(Bn))Cl] with MgCH(3)Br produces only halide exchange with the formation of [CpRh(Q(Bn))Br]. The [CpRh(Q)Cl] complexes react with PPh(3) in dichloromethane yielding the adducts CpRh(Q)Cl/PPh(3) (1:1) which exist in solution in two different isomeric forms. The interaction of [CpRh(Q(Me))Cl] with AgNO(3) in MeCN allows generation of [CpRh(Q(Me))(MeCN)]NO(3).3H(2)O, whereas the reaction of [CpRh(Q(Me))Cl] with AgClO(4) in the same solvent yields both [CpRh(Q(Me))(H(2)O)]ClO(4) and [CpRh(Cl)(H(2)O)(2)]ClO(4); the H(2)O molecules derive from the not-rigorously anhydrous solvents or silver salts.     

The synthesis, characterisation and reactivity of 2-phosphanylethylcyclopentadienyl complexes of cobalt, rhodium and iridium

2-Phosphanylethylcyclopentadienyl lithium compounds, Li[C(5)R'(4)(CH(2))(2)PR(2)] (R = Et, R' = H or Me, R = Ph, R' = Me), have been prepared from the reaction of spirohydrocarbons C(5)R'(4)(C(2)H(4)) with LiPR(2). C(5)Et(4)HSiMe(2)CH(2)PMe(2), was prepared from reaction of Li[C(5)Et(4)] with Me(2)SiCl(2) followed by Me(2)PCH(2)Li. The lithium salts were reacted with [RhCl(CO)(2)](2), [IrCl(CO)(3)] or [Co(2)(CO)(8)] to give [M(C(5)R'(4)(CH(2))(2)PR(2))(CO)] (M = Rh, R = Et, R' = H or Me, R = Ph, R' = Me; M = Ir or Co, R = Et, R' = Me), which have been fully characterised, in many cases crystallographically as monomers with coordination of the phosphorus atom and the cyclopentadienyl ring. The values of nu(CO) for these complexes are usually lower than those for the analogous complexes without the bridge between the cyclopentadienyl ring and the phosphine, the exception being [Rh(Cp'(CH(2))(2)PEt(2))(CO)] (Cp' = C(5)Me(4)), the most electron rich of the complexes. [Rh(C(5)Et(4)SiMe(2)CH(2)PMe(2))(CO)] may be a dimer. [Co(2)(CO)(8)] reacts with C(5)H(5)(CH(2))(2)PEt(2) or C(5)Et(4)HSiMe(2)CH(2)PMe(2) (L) to give binuclear complexes of the form [Co(2)(CO)(6)L(2)] with almost linear PCoCoP skeletons. [Rh(Cp'(CH(2))(2)PEt(2))(CO)] and [Rh(Cp'(CH(2))(2)PPh(2))(CO)] are active for methanol carbonylation at 150 degrees C and 27 bar CO, with the rate using [Rh(Cp'(CH(2))(2)PPh(2))(CO)] (0.81 mol dm(-3) h(-1)) being higher than that for [RhI(2)(CO)(2)](-) (0.64 mol dm(-3) h(-1)). The most electron rich complex, [Rh(Cp'(CH(2))(2)PEt(2))(CO)] (0.38 mol dm(-3) h(-1)) gave a comparable rate to [Cp*Rh(PEt(3))(CO)] (0.30 mol dm(-3) h(-1)), which was unstable towards oxidation of the phosphine. [Rh(Cp'(CH(2))(2)PEt(2))I(2)], which is inactive for methanol carbonylation, was isolated after the methanol carbonylation reaction using [Rh(Cp'(CH(2))(2)PEt(2))(CO)]. Neither of [M(Cp'(CH(2))(2)PEt(2))(CO)] (M = Co or Ir) was active for methanol carbonylation under these conditions, nor under many other conditions investigated, except that [Ir(Cp'(CH(2))(2)PEt(2))(CO)] showed some activity at higher temperature (190 degrees C), probably as a result of degradation to [IrI(2)(CO)(2)](-). [M(Cp'(CH(2))(2)PEt(2))(CO)] react with MeI to give [M(Cp'(CH(2))(2)PEt(2))(C(O)Me)I] (M = Co or Rh) or [Ir(Cp'(CH(2))(2)PEt(2))Me(CO)]I. The rates of oxidative addition of MeI to [Rh(C(5)H(4)(CH(2))(2)PEt(2))(CO)] and [Rh(Cp'(CH(2))(2)PPh(2))(CO)] are 62 and 1770 times faster than to [Cp*Rh(CO)(2)]. Methyl migration is slower, however. High pressure NMR studies show that [Co(Cp'(CH(2))(2)PEt(2))(CO)] and [Cp*Rh(PEt(3))(CO)] are unstable towards phosphine oxidation and/or quaternisation under methanol carbonylation conditions, but that [Rh(Cp'(CH(2))(2)PEt(2))(CO)] does not exhibit phosphine degradation, eventually producing inactive [Rh(Cp'(CH(2))(2)PEt(2))I(2)] at least under conditions of poor gas mixing. The observation of [Rh(Cp'(CH(2))(2)PEt(2))(C(O)Me)I] under methanol carbonylation conditions suggests that the rhodium centre has become so electron rich that reductive elimination of ethanoyl iodide has become rate determining for methanol carbonylation. In addition to the high electron density at rhodium.     

Synthesis and characterization of heterobimetallic oxo-bridged aluminum-rare earth metal complexes

Reaction of the aluminum hydroxide LAl(OH)[C(Ph)CH(Ph)] (1, L = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(6)H(3)) with Y(CH(2)SiMe(3))(3)(THF)(2) yielded the oxo-bridged heterobimetallic yttrium dialkyl complex LAl[C(Ph)CH(Ph)](μ-O)Y(CH(2)SiMe(3))(2)(THF)(2) (2). Alkane elimination reaction of 2 with 2-(imino)pyrrole [NN]H ([NN]H = 2-(ArN═CH)-5-tBuC(4)H(2)NH) afforded the yttrium monoalkyl complex LAl[C(Ph)CH(Ph)] (μ-O)Y(CH(2)SiMe(3))[NN](THF)(2) (5). Alternatively, 5 can be prepared in high yield by reaction of 1 with [NN]Y(CH(2)SiMe(3))(2)(THF)(2) (3). The analogous samarium alkyl complex LAl[C(Ph)CH(Ph)](μ-O)Sm(CH(2)SiMe(3))[NN](THF)(2) (6) was prepared similarly. Reactions of 5 and 6 with 1 equiv of iPrOH yielded the corresponding alkoxyl complexes 7 and 8, respectively. The molecular structures of 3, 6, and 8 have been determined by X-ray single-crystal analysis. Complexes 2, 3, 5, 7, and 8 have been investigated as lactide polymerization initiators. The heterobimetallic alkoxyl 8 is highly active to yield high molecular weight (M(n) = 6.91 × 10(4)) polylactides with over 91% conversion at the lactide-to-initiator molar ratio of 2000.     

Unusual pathways for metal-assisted C[bond]C and C[bond]P coupling reactions using allenylidenerhodium complexes as precursors

The rhodium allenylidenes trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = Ph (1), p-Tol (2)] react with NaC(5)H(5) to give the half-sandwich type complexes [(eta(5)-C(5)H(5))Rh[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))] (3, 4). The reaction of 1 with the Grignard reagent CH(2)[double bond]CHMgBr affords the eta(3)-pentatrienyl compound [Rh(eta(3)-CH(2)CHC[double bond]C[double bond]CPh(2))(PiPr(3))(2)] (6), which in the presence of CO rearranges to the eta(1)-pentatrienyl derivative trans-[Rh[eta(1)-C(CH[double bond]CH(2))[double bond]C[double bond]CPh(2)](CO)(PiPr(3))(2)] (7). Treatment of 7 with acetic acid generates the vinylallene CH(2)[double bond]CH[bond]CH[double bond]=C=CPh(2) (8). Compounds 1 and 2 react with HCl to give the five-coordinate allenylrhodium(III) complexes [RhCl(2)[CH[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (10, 11). An unusual [C(3) + C(2) + P] coupling process takes place upon treatment of 1 with terminal alkynes HC[triple bond]CR', leading to the formation of the eta(3)-allylic compounds [RhCl[eta(3)-anti-CH(PiPr(3))C(R')C[double bond]C[double bond]CPh(2)](PiPr(3))] [R' = Ph (12), p-Tol (13), SiMe(3) (14)]. From 12 and RMgBr the corresponding phenyl and vinyl rhodium(I) derivatives 15 and 16 have been obtained. The previously unknown unsaturated ylide iPr(3)PCHC(Ph)[double bond]C[double bond]C[double bond]CPh(2) (17) was generated from 12 and CO. A [C(3) + P] coupling process occurs on treatment of the rhodium allenylidenes 1, 2, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(p-Anis)(2)](PiPr(3))(2)] (20) with either Cl(2) or PhICl(2), affording the ylide-rhodium(III) complexes [RhCl(3)[C(PiPr(3))C[double bond]C(R)R'](PiPr(3))] (21-23). The butatrienerhodium(I) compounds trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (28-31) were prepared from 1, 20, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = CF(3) (26), tBu (27)] and diazomethane; with the exception of 30 (R = CF(3), R' = Ph), they thermally rearrange to the isomers trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (32, 33, and syn/anti-34). The new 1,1-disubstituted butatriene H(2)C[double bond]C[double bond]C[double bond]C(tBu)Ph (35) was generated either from 31 or 34 and CO. The iodo derivatives trans-[RhI(eta(2)-H(2)C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] [R = Ph (38), p-Anis (39)] were obtained by an unusual route from 1 or 20 and CH(3)I in the presence of KI. While the hydrogenation of 1 and 26 leads to the allenerhodium(I) complexes trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (40, 41), the thermolysis of 1 and 20 produces the rhodium(I) hexapentaenes trans-[RhCl(eta(2)-R(2)C[double bond]C[double bond]C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] (44, 45) via C-C coupling. The molecular structures of 3, 7, 12, 21, and 28 have been determined by X-ray crystallography.     

Cyclometallated Pd(II) azido complexes containing 6-phenyl-2,2'-bipyridyl or 2-phenylpyridyl derivatives: synthesis and reactivity toward organic isocyanides and isothiocyanates

Cyclometallated palladium(II) azido complexes containing C,N,N- or C,N-donor ligands, [Pd(N(3))L](HL = 6-phenyl-2,2'-bipyridine or 2-phenylpyridyl derivatives), showed different reactivities toward organic isocyanides and isothiocyanates. In particular, aryl isocyanides (CN-Ar) underwent insertion into the orthometallated Pd-C bond on the phenyl moiety of the supporting ligand (L) in [Pd(N(3))L] or [Pd(N(3))(PR(3))L] to selectively give carbodiimido [[Pd(N=C=N-Ar)L]], imidoyl [[Pd(N(3))(-C=N-Ar)(PR(3))L]], or imidoyl carbodiimido complexes [[Pd(N=C=N-Ar)(-C=N-Ar)L] or [Pd(N=C=N-Ar)(-C=N-Ar)(PR(3))L]], depending on reaction conditions. Interestingly, reactions of [Pd(N(3))(PR(3))L] with organic isothiocyanates gave unusual dinuclear complexes [(micro-SCN(4)-R)PdL](2), exhibiting the concurrent S- and N-coordinating thio-tetrazole bridge.     

Temperature-dependent coordination of phosphine to five-coordinate alkenylruthenium complexes

The red, five-coordinate complexes Ru(CO)Cl(PPh(3))2(CH=CHPh) and [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHC(6)H(4)CH=CH) undergo reversible coordination of PPh(3) at low temperature to produce the pale yellow, six-coordinate complexes Ru(CO)Cl(PPh(3))3(CH=CHPh) and [Ru(CO)Cl(PPh(3))3]2(mu-CH=CHC(6)H(4)CH=CH). X-ray crystal structures of the latter complex and of the hydride complex RuH(CO)Cl(PPh(3))3 were obtained. 1H and 31P NMR spectra between 20 and -70 degrees C exhibit large changes in both equilibrium constants and dynamic effects. Thermodynamic parameters, DeltaH = -17.5 +/- 2.0 kcal/mol and DeltaS = -57.5 +/- 7.6 eu, were obtained for PPh(3) coordination to the monoruthenium complex, and activation parameters, DeltaH = 20.6 +/- 0.7 kcal/mol and DeltaS = 41.6 +/- 2.0 eu, were obtained for the reverse decoordination. Coordination of PPh(3) was not observed upon cooling of the shorter bridged complex, [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHCH=CH).     

Towards new organometallic wires: tetraruthenium complexes bridged by phenylenevinylene and vinylpyridine ligands

The tetranuclear complexes [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)Ru Cl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)- CH=CH-1,4)] (3 a) and [{(PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (3b), which contain vinylpyridine ligands that connect peripheral Ru(PiPr(3))(2)(CO)Cl units to a central divinylphenylene-bridged diruthenium core, have been prepared and investigated. These complexes, in various oxidation states up to the tetracation level, have been characterized by standard electrochemical and spectroelectrochemical techniques, including IR, UV/Vis/NIR and ESR spectroscopy. A comparison with the results for the vinylpyridine-bridged dinuclear complex [PiPr(3))(2)(CO)ClRu(mu-CH=CHpy)RuCl(CO)(PPh(3))(2)(CH=CHPh)] (6) and the divinylphenylene-bridged complexes [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,4)] (8a) and [{(EtOOCpy)(CO)Cl(PPh(3))(2)Ru}(2)(mu-CH=CH-C(6)H(4)-CH=CH-1,3)] (8b), which represent the outer sections (6) or the inner core (8a,b) of complexes 3a,b, and with the mononuclear complex [(EtOOCpy)(CO)(PPh(3))(2)RuCl(CH=CHPh)] (7) indicate that every accessible oxidation process is primarily centred on one of the vinyl ligands, with smaller contributions from the metal centres. The experimental results and quantum chemical calculations indicate charge- and spin-delocalization across the central divinylphenylenediruthenium part of 3a,b or the styrylruthenium unit of 6, but not beyond. The energy gap between the higher lying styryl- or divinylphenylenediruthenium-based and the lower occupied vinylpyridineruthenium-based orbitals increases in the order 6<3 b<3 a and thus follows the conjugation within the non-heteroatom-substituted aromatic vinyl ligand.     

Homolysis of the Ln-N (Ln = Yb, Eu) bond. Synthesis, structural characterization and catalytic activity of ytterbium(II) and europium(II) complexes with methoxyethyl functionalized indenyl ligands

The interaction of methoxyethyl functionalized indene compounds (C(9)H(6)-1-R-3-CH(2)CH(2)OMe, R =t-BuNHSiMe(2)(1), Me(3)Si (2), H (3)) with [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5)) produced a series of new ytterbium(II) and europium(II) complexes via tandem silylamine elimination/homolysis of the Ln-N (Ln=Yb, Eu) bond. Treatment of the lanthanide(III) amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5) with 2 equiv. of, 1,2 and 3, respectively, produced, after workup, the ytterbium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Yb(II) (6), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Yb(II) (7), (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Yb(II)(8) and the corresponding europium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Eu(II)(9), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Eu(II)(10) and (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Eu(II)(11) in moderate to good yield. In contrast, interaction of the corresponding indene compounds 1, 2 or 3 with the lanthanide amides [(Me(3)Si)(2)N](3)Ln (Ln = Yb, Eu) was not observed, while addition of 0.5 equiv. of anhydrous LiCl to the corresponding reaction mixture produced, after workup, the corresponding ytterbium(II) or europium(II) complexes. All the new compounds were fully characterized by spectroscopic and elemental analyses. The structures of complexes, and were determined by single-crystal X-ray analyses. The catalytic activity of all the ytterbium(II) and europium(II) complexes on MMA polymerization was examined. It was found that all the ytterbium(II) and europium(II) complexes can function as single-component MMA polymerization catalysts. The temperature, solvent and ligand effects on the catalytic activity were studied.     

Synthesis, structures, and reactivity of weakly coordinating anions with delocalized borate structure: the assessment of anion effects in metallocene polymerization catalysts.

The formation of adducts of tris(pentafluorophenyl)borane with strongly coordinating anions such as CN(-) and [M(CN)(4)](2)(-) (M = Ni, Pd) is a synthetically facile route to the bulky, very weakly coordinating anions [CN[B(C(6)F(5))(3)](2)](-) and [M[CNB(C(6)F(5))(3)](4)](2-) which are isolated as stable NHMe(2)Ph(+) and CPh(3)(+) salts. The crystal structures of [CPh(3)][CN[B(C(6)F(5))(3)](2)] (1), [CPh(3)][ClB(C(6)F(5))(3)] (2), [NHMe(2)Ph](2)[Ni[CNB(C(6)F(5))(3)](4)].2Me(2)CO (4b.2Me(2)CO), [CPh(3)](2)[Ni[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (4c.2CH(2)Cl(2)), and [CPh(3)](2)[Pd[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (5c.2CH(2)Cl(2)) are reported. The CN stretching frequencies in 4 and 5 are shifted by approximately 110 cm(-1) to higher wavenumbers compared to the parent tetracyano complexes in aqueous solution, although the M-C and C-N distances show no significant change on B(C(6)F(5))(3) coordination. Zirconocene dimethyl complexes L(2)ZrMe(2) [L(2) = Cp(2), SBI = rac-Me(2)Si(Ind)(2)] react with 1, 4c or 5c in benzene solution at 20 degrees C to give the salts of binuclear methyl-bridged cations, [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] and [(L(2)ZrMe)(2)(mu-Me)](2)[M[CNB(C(6)F(5))(3)](4)]. The reactivity of these species in solution was studied in comparison with the known [[(SBI)ZrMe](2)(mu-Me)][B(C(6)F(5))(4)]. While the latter reacts with excess [CPh(3)][B(C(6)F(5))(4)] in benzene to give the mononuclear ion pair [(SBI)ZrMe(+).B(C(6)F(5))(4)(-)] in a pseudo-first-order reaction, k = 3 x 10(-4) s(-1), [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] reacts to give a mixture of L(2)ZrMe(mu-Me)B(C(6)F(5))(3) and L(2)ZrMe(mu-NC)B(C(6)F(5))(3). Recrystallization of [Cp' '(2)Zr(mu-Me)(2)AlMe(2)][CN[B(C(6)F(5))(3)](2)] affords Cp' '(2)ZrMe(mu-NC)B(C(6)F(5))(3) 6, the X-ray structure of which is reported. The stability of [(L(2)ZrMe)(2)(mu-Me)](+)X(-) decreases in the order X = [B(C(6)F(5))(4)] > [M[CNB(C(6)F(5))(3)](4)] > [CN[B(C(6)F(5))(3)](2)] and increases strongly with the steric bulk of L(2) = Cp(2) < SBI. Activation of (SBI)ZrMe(2) by 1 in the presence of AlBu(i)(3) gives extremely active ethene polymerization catalysts. Polymerization studies at 1-7 bar monomer pressure suggest that these, and by implication most other highly active ethene polymerization catalysts, are strongly mass-transport limited. By contrast, monitoring propene polymerization activities with the systems (SBI)ZrMe(2)/1/AlBu(i)(3) and CGCTiMe(2)/1/AlBu(i)(3) at 20 degrees C as a function of catalyst concentration demonstrates that in these cases mass-transport limitation is absent up to [metal] approximately 2 x 10(-5) mol L(-1). Propene polymerization activities decrease in the order [CN[B(C(6)F(5))(3)](2)](-) > [B(C(6)F(5))(4)](-) > [M[CNB(C(6)F(5))(3)](4)](2-) > [MeB(C(6)F(5))(3)](-), with differences in activation barriers relative to [CN[B(C(6)F(5))(3)](2)](-) of DeltaDeltaG = 1.1 (B(C(6)F(5))(4)(-)), 4.1 (Ni[CNB(C(6)F(5))(3)](4)(2-)) and 10.7-12.8 kJ mol(-)(1) (MeB(C(6)F(5))(3)(-)). The data suggest that even in the case of very bulky anions with delocalized negative charge the displacement of the anion by the monomer must be involved in the rate-limiting step.     

Yttrium complexes incorporating the chelating diamides [ArN(CH2)xNAr]2- (Ar = C6H3-2,6-iPr2, x= 2, 3) and their unusual reaction with phenylsilane

Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)).     

Ligand-modification effects on the reactivity, solubility, and stability of organometallic tantalum complexes in water

Tantalum complexes [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NMe(2))=CH)py}] (4) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NH(2))=CH)py}] (5), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ(3)-N,O,O-(OCH(2))(OCH)py}] (Cp* = η(5)-C(5)Me(5)) with HC≡CCH(2)NMe(2) and HC≡CCH(2)NH(2), respectively. The reactions of [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(Ph)=CH)py}] (2) and [TaCp*Me{κ(4)-C,N,O,O-(OCH(2))(OCHC(SiMe(3))=CH)py}] (3) with triflic acid (1:2 molar ratio) rendered the corresponding bis-triflate derivatives [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(Ph)=CH(2))py}] (6) and [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(OCHC(SiMe(3))=CH(2))py}] (7), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water-soluble cationic complex [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH)py}]OTf (8). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H(2)O){κ(3)-N,O,O-(OCH(2))(OCHC(CH(2)NHMe(2))=CH(2))py}](OTf)(2) (9). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ(4)-C,N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH)py}](OTf)(2) (10), which afforded the corresponding protonolysis derivative [TaCp*(OTf)(2){κ(3)-N,O,O-(OCH(2))(HOCHC(CH(2)NHMe(2))=CH(2))py}](OTf) (11) in solution. Complex 8 reacted with CNtBu and potassium 2-isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13, respectively. The molecular structures of complexes 5, 7, and 10 were established by single-crystal X-ray diffraction studies.     

Electronic response of a (P,N)-based ligand on metal coordination

The reaction of [(THF)Li(Ph(2)PC(H)Py)] with ZnCl(2) in the presence of ZnO yields the zinc complex [Zn(3)(Ph(2)PC(H)Py)(4)O] (1). Deprotonation of the phosphane Ph(2)P(CH(2)Py) with [Fe(N(SiMe(3))(2))2] gives the iron complexes [(Ph(2)P(CH(2)Py))Fe(Ph(2)PC(H)Py)2] (2) and [Fe(Ph(2)PC(H)Py)(N(SiMe(3))(2))]2 (3), depending on the ratio of phosphane. The solid state structures of the metal complexes illustrate the coordination flexibility of the [Ph(2)C(H)Py](-)-anion. Depending on the electronic requirements of the coordinated metal the anion acts as a (P,N)-chelating amide or C-coordinating carbanion with the P- and N-heteroatoms as donor bases.     

Synthesis, structure, and reactivity of fluorous phosphorus/carbon/phosphorus pincer ligands and metal complexes

Reactions of the diphosphine 1,3-C6H4(CH2PH2)2 and fluorous alkenes H2C=CHR(fn)(R(fn)=(CF2)(n-1)CF3; n = 6, 8) at 75 degrees C in the presence of AIBN give the title ligands 1,3-C6H4(CH2P(CH2CH2R(fn))2)2(3-R(fn)) and byproducts 1,3-C6H4(CH3)(CH2P(CH2CH2R(fn))2)(4-R(fn)) in 1 : 3 to 1 : 5 ratios. Workups give -R(fn) in 4--17% yields. Similar results are obtained photochemically. Reaction of 1,3-C6H4(CH2Br)2 and HP(CH2CH2R(f8))2 (5) at 80 degrees C (neat, 1 : 2 mol ratio) gives instead of simple substitution the metacyclophane [1,3-C6H4(CH2P(CH2CH2R(f8))2 CH2-1,3-C(6)H(4)CH(2)P[lower bond 1 end](CH2CH2R(f8))2C[upper bond 1 end]H2](2+)2Br-, which upon treatment with LiAlH(4) yields 3-R(f8)(20%), 4-R(f8), and other products. Efforts to better access 3-R(f8), either by altering stoichiometry or using various combinations of the phosphine borane (H3B)PH(CH2CH2R(f8))2 and base, are unsuccessful. Reactions of 3-R(fn) with Pd(O2CCF3)2 and [IrCl(COE)2]2(COE=cyclooctene) give the palladium and iridium pincer complexes (2,6,1-C6H3(CH2 P(CH2CH2R(fn))(2)(2)Pd(O2CCF3)(10-R(fn); 80-90%) and (2,6,1-C6H3(CH2P(CH2CH2R(f8))2)2)Ir(Cl)(H)(11-R(f8); 29%), which exhibit CF3C6F(11)/toluene partition coefficients of >96 : <4. The crystal structure of 10-R(f8) shows CH2CH2R(f8) groups with all-anti conformations that extend in parallel above and below the palladium square plane to create fluorous lattice domains. NMR monitoring shows a precursor to 11-R(f8) that is believed to be a COE adduct.