Synthese,Struktur und Reaktivität von η3‐1,2‐Diphosphaallylkomplexen sowie von [{(η5‐C5H5)(CO)2W–Co(CO)3}{μ‐AsCH(SiMe3)2}(μ‐CO)]

Syntheses, Structure and Reactivity of η³‐1,2‐Diphosphaallyl Complexes and [{(η⁵‐C₅H₅)(CO)₂W–Co(CO)₃}{μ‐AsCH(SiMe₃)₂}(μ‐CO)] Reaction of ClP=C(SiMe₂iPr)₂ ( 3 ) with Na[Mo(CO)₃(η⁵‐C₅H₅)] afforded the phosphavinylidene complex [(η⁵‐C₅H₅)(CO)₂Mo=P=C(SiMe₂iPr)₂] ( 4 ) which in situ was converted into the η¹‐1,2‐diphosphaallyl complex [η⁵‐(C₅H₅)(CO)₂Mo{η³‐tBuPPC(SiMe₂iPr)₂] ( 6 ) by treatment with the phosphaalkene tBuP=C(NMe₂)₂. The chloroarsanyl complexes [(η⁵‐C₅H₅)(CO)₃M–As(Cl)CH(SiMe₃)₂] [where M = Mo ( 9 ); M = W ( 10 )] resulted from the reaction of Na[M(CO)₃(η⁵‐C₅H₅)] (M = Mo, W) with Cl₂AsCH(SiMe₃)₂. The tungsten derivative 10 and Na[Co(CO)₄] underwent reaction to give the dinuclear μ‐arsinidene complex [(η⁵‐C₅H₅)(CO)₂W–Co(CO)₃{μ‐AsCH(SiMe₃)₂}(μ‐CO)] ( 11 ). Treatment of [(η⁵‐C₅H₅)(CO)₂Mo{η³‐tBuPPC(SiMe₃)₂}] ( 1 ) with an equimolar amount of ethereal HBF₄ gave rise to a 85/15 mixture of the saline complexes [(η⁵‐C₅H₅)(CO)₂Mo{η²‐tBu(H)P–P(F)CH(SiMe₃)₂}]BF₄ ( 18 ) and [Cp(CO)₂Mo{F₂PCH(SiMe₃)₂}(tBuPH₂)]BF₄ ( 19 ) by HF‐addition to the PC bond of the η³‐diphosphaallyl ligand and subsequent protonation ( 18 ) and/or scission of the PP bond by the acid ( 19 ). Consistently 19 was the sole product when 1 was allowed to react with an excess of ethereal HBF₄. The products 6 , 9 , 10 , 11 , 18 and 19 were characterized by means of spectroscopy (IR, ¹H‐, ¹³C{¹H}‐, ³¹P{¹H}‐NMR, MS). Moreover, the molecular structures of 6 , 11 and 18 were determined by X‐ray diffraction analysis.     

Direct synthesis of linear low‐density polyethylene of ethylene/1‐hexene from ethylene with a tandem catalytic system in a single reactor

Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η⁵‐C₅H₄CMe₂C₆H₅)TiCl₃ ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η⁵‐C₅Me₄)SiMe₂(^tBuN)]TiCl₂ ( 2 )/MMAO or rac‐Me₂Si(2‐MeBenz[e]Ind)₂ZrCl₂ ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004     

Synthesis of Mixed-ring Zirconocene Complexes Containing Alkenyl Group and Ethylene Polymerization Catalyzed with Them

Four new mixed‐ring zirconium completes, [CH₂ = CH(CH₂)_n ‐C₅H₄](RC₅H₄)ZrCl₂ [n = l, R = CH₃OCH₂CH₂(3); n = 2, R = CH₃OCH₂CH₂ (4); n = 2, R=Me₃Si (5); n = 2, R = allyl (6)], have been prepared by the reaction of CH₂ = CH(CH₂)_n C₅H₄ZrCl₃, DME[n = l (1); n = 2 (2)] with RC₅H₄Li. When activated with methylaluminoxane (MAO), the catalytic activities of the above complexes in ethylene polymerization were tested. Complexes 5 and 6 show high activities similar to Cp₂ZrCl₂. Introduction of methoxyethyl group into Cp‐ligand dramatically decreases the catalytic activities of complexes 3 and 4, which can be overcome by increasing the amount of MAO. For complex 5, the dependence of activity and molecular weight (Mη) on the Al/Zr ratio, the polymerization time (t_P), polymerization temperature (T_P) and the polymerization solvent volume (V) was investigated.     

Formation of Alkyne Bridged Multicobalt Carbonyl Complexes with Tris(2‐Thienyl)Phosphine or Bis(Trimethylsilylethynyl)Phenylphosphine Ligand

Treatment of Co₄(CO)₁₂ with an excess of trimethylsilylacetylene (TMSA) in the presence of tri(2‐thienyl)phosphine in THF at 25 °C for 2 hours yielded six compounds. Two pseudo‐octahedral, alkyne‐bridged tetracobalt clusters, [Co₄(μ₄‐η²‐HC≡CSiMe₃)(CO)₁₀(μ‐CO)₂] ( 4 ) and [Co₄(μ₄‐η²‐HC≡CSiMe³)‐(CO)₉(μ‐CO)₂{P(C₄H₄S)₃}] ( 6 ), along with an alkyne‐bridged dicobalt complex, [Co₂(CO)₅(μ‐HC≡CSiMe₃)‐{P(C₄H₄S)₃}] ( 5 ), were obtained as new compounds. The addition of the thienylphosphine ligand, in fact, facilitates the reaction rate. Reaction of an alkyne‐bridged dicobalt complex, [(η²‐H‐C≡C‐SiMe₃)Co₂(CO)₆] ( 3 ), with a bi‐functional ligand, PPh(‐C≡C‐SiMe₃)₂, yielded an unexpected six‐membered, cyclic compound, {(Ph)(Me₃Si‐C≡C)P‐[(η²‐C≡C‐SiMe₃)Co₂(CO)₅]}₂ ( 7 ). All of these new compounds were characterized by spectroscopic means; the solid‐state structures of ( 5 ), ( 6 ) and ( 7 ) have been established by X‐ray crystallography.     

Synthesis and Insertion Chemistry of Mixed Tether Uranium Metallocene Complexes

The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η⁵‐C₅Me₄SiMe₂CH₂‐κC)₂U] ( 1 ) with substrates that react with only one of the U? C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U? C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN₃) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η⁵‐C₅Me₄SiMe₂CH₂‐κC)U(η⁵‐C₅Me₄SiMe₂‐CH₂NNN‐Ad‐κ²N^1,3)]. Similarly, a single equivalent of CS₂ reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η⁵‐C₅Me₄SiMe₂CH₂‐κC)U(η⁵‐C₅Me₄SiMe₂‐ CH₂C(S)₂‐κ²S,S′)], a reaction that constitutes the first example of CS₂ insertion into a U⁴⁺? C bond. Complex 1 reacts with one equivalent of pyridine N‐oxide by C? H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N‐oxide complex [(η⁵‐C₅Me₄SiMe₂CH₂‐κC)(η⁵‐C₅Me₄SiMe₃)U(C₆H₄NO‐κ²C,O)]. The remaining (η⁵‐C₅Me₄SiMe₂CH₂‐κC)^2? ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η⁵‐C₅Me₄SiMe₃)U(C₅H₄NO‐κ²C,O)(η⁵‐C₅Me₄SiMe₂C(?CH₂)O‐κO)] and [(η⁵‐C₅Me₄SiMe₂CH₂NNN‐Ad‐κ²N^1,3)U(η⁵‐C₅Me₄SiMe₂C(?CH₂)O‐κO)].     

Synthesis and characterization of methyl-phenyl-substituted cyclopentadienyl zirconium complexes

The trisubstituted methyl-phenyl-silyl-cyclopentadienes [Me-Ph-C₅H₃(SiMe₂X)] (X = Me, Cl, NHt-Bu) and [(Me-Ph-C₅H₃)₂SiMe₂] and the lithium salts Li₂[Me-Ph-C₅H₂(SiMe₂Nt-Bu)] and Li₂[(Me-Ph-C₅H₂)₂SiMe₂] have been isolated by conventional methods and characterized by NMR spectroscopy. Desilylation of [Me-Ph-C₅H₃(SiMe₃)] with ZrCl₄(SMe₂)₂ gave the monocyclopentadienyl complex [Zr(η⁵-1-Ph-3-Me-C₅H₃)Cl₃]. The ansa-metallocene [Zr{(η⁵-2-Me-4-Ph-C₅H₂)SiMe₂(η⁵-2-Ph-4-Me-C₅H₂)}Cl₂] was obtained from the mixture of isomers formed by transmetallation of Li₂[(Me-Ph-C₅H₂)₂SiMe₂] to ZrCl₄ and characterized as the meso-diastereomer by X-ray diffraction methods. Similar transmetallation of Li₂[Me-Ph-C₅H₂(SiMe₂Nt-Bu)] gave the silyl-η-amido complex [Zr{η⁵-2-Me-4-Ph-C₅H₂(SiMe₂-η-Nt-Bu)}Cl₂] that was further alkylated to give [Zr{η⁵-2-Me-4-Ph-C₅H₂(SiMe₂-η-Nt-Bu)}R₂] (R = Me, CH₂Ph) and used as a catalyst precursor, activated with MAO, for ethene and propene polymerization. All of the new compounds were characterized by elemental analysis and NMR spectroscopy.     

Activation of Molecular Hydrogen by Bis(η5,η1‐pentafulvene)‐titanium Complexes – Efficient Formation of Titanium(III)hydrides

The synthesis and crystal structures of two dinuclear titanocene hydride complexes are reported. Both complexes, namely bis(η⁵‐(di‐para‐tolylmethyl)cyclopentadienyl)titanium hydride dimer, [(η⁵‐C₂₀H₁₉)₂Ti(μ‐H)]₂ ( 2a ), and bis(η⁵‐2‐adamantylcyclopentadienyl)‐titanium hydride dimer, [(η⁵‐C₁₅H₁₉)₂Ti(μ‐H)]₂ ( 2b ), are formed via activation of molecular hydrogen by the corresponding bis(η⁵,η¹‐pentafulvene)titanium complexes 1a and 1b at ambient temperatures and pressures in high yields. The hydride complexes 2a and 2b exhibit planar [Ti₂H₂] cores and, as a result of the heterolytic cleavage of molecular hydrogen, substituted Cp Ligands were formed during the reaction.     

Dinuclear Dysprosium and Ytterbium Complexes Incorporating N,N‐Bis(pyrrolyl‐α‐methyl)‐N‐methylamine Ligand: Syntheses and Structures

Reaction of DyCl₃ with two equivalents of NaN(SiMe₃)₂ in THF yielded {Dy(μ‐Cl)[N(SiMe₃)₂]₂(THF)}₂ ( 1 ). X‐ray crystal structure analysis revealed that 1 is a centrosymmetric dimer with asymmetrically bridging chloride ligands. The metal coordination arrangement can be best described as distorted trigonal bipyramid. The bond lengths of Ln–Cl and Ln–N showed a decreasing trend with the contraction of the size of Ln³⁺. Treatment of N,N‐bis(pyrrolyl‐α‐methyl)‐N‐methylamine (H₂dpma) with 1 and known compound {Yb(μ‐Cl)[N(SiMe₃)₂]₂(THF)}₂, respectively, led to the formations of [Dy(μ‐Cl)(dpma)(THF)₂]₂ ( 2 ) and {Yb(μ‐Cl)[N(SiMe₃)₂]₂(THF)}₂ ( 3 ). Compounds 2 and 3 were fully characterized by single‐crystal X‐ray crystallography, elemental analysis, and ¹H NMR spectroscopy. Structure determination indicated that 2 and 3 exhibit as centrosymmetric dimers with asymmetrically bridging chloride ligands. One pot reactions involving LnCl₃ (Ln = Dy and Yb), LiN(SiMe₃)₂, and H₂dpma were explored and desired products 2 and 3 were not yielded, which indicated that 1 and {Yb(μ‐Cl)[N(SiMe₃)₂]₂(THF)}₂ are the demanding precursors to synthesize Dysprosium and Ytterbium complexes supported by dpma^2– ligand. Compounds 2 and 3 are the first reported lanthanide complexes chelated by dpma^2– ligand.     

Der Dihydridoiridium(III)‐Komplex [IrH2Cl(PiPr3)2] als Molekülbaustein für unsymmetrische Rhodium–Iridiumund Iridium–Iridium‐Zweikernverbindungen

The Dihydridoiridium(III) Complex [IrH₂Cl(P i Pr₃)₂] as a Molecular Building Block for Unsymmetrical Binuclear Rhodium–Iridium and Iridium–Iridium Compounds The title compound [IrH₂Cl(PiPr₃)₂] ( 3 ) reacts with the chloro‐bridged dimers [RhCl(PiPr₃)₂]₂ ( 1 ) and [IrCl(C₈H₁₄)(PiPr₃)]₂ ( 5 ) by cleavage of the Cl‐bridges to give the unsymmetrical binuclear complexes 4 and 6 with Rh(μ‐Cl)₂Ir and Ir(μ‐Cl)₂Ir as the central building block. The reactions of 3 with the bis(cyclooctene) and (1,5‐cyclooctadiene) compounds [MCl(C₈H₁₄)₂]₂ ( 7 , 8 ) and [MCl(η⁴‐C₈H₁₂)]₂ ( 9 , 10 ) (M = Rh, Ir) occur analogously and afford the rhodium(I)‐iridium(III) and iridium(I)‐iridium(III) complexes 11 – 14 in 70–80% yield. Treatment of [(η⁴‐C₈H₁₂)M(μ‐Cl)₂IrH₂(PiPr₃)₂] ( 13 , 14 ) with phenylacetylene leads to the formation of the substitution products [(η⁴‐C₈H₁₂)M(μ‐Cl)₂IrH(C≡CPh)(PiPr₃)₂] ( 15 , 16 ) without changing the central molecular core. Similarly, the compound [(η⁴‐C₈H₁₂)Rh(μ‐Br)₂IrH(C≡CPh)(PiPr₃)₂] ( 18 ) has been prepared; it was characterized by X‐ray crystallography.     

Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η2:η1:η1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐cis‐Polymerization

Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η²:η¹:η¹ hapticities are synthesized and characterized. Treatment of [RE(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of 3‐(tBuN?CH)C₈H₅NH ( L₁ ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH(CH₂SiMe₃)}Ind)RE(thf)(CH₂SiMe₃)]₂ (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L₁ is deprotonated by the metal alkyl species and the imino C?N group is transferred to the amido group by alkyl CH₂SiMe₃ insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ‐η²:η¹:η¹ bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L₁ is reduced to 3‐(tBuNHCH₂)C₈H₅NH ( L₂ ), the reaction of [Yb(CH₂SiMe₃)₃(thf)₂] with 1 equivalent of L₂ in THF, interestingly, generated the trans‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (major) and cis‐[(μ‐η²:η¹:η¹‐3‐{tBuNCH₂}Ind)Yb(thf)(CH₂SiMe₃)]₂ (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐cis‐polymerization.     

The Potential of Molybdenum Complexes Bearing Unsubstituted Heterodiatomic Group 15 Elements as Linkers in Supramolecular Chemistry

The reactions of tetrahedral molybdenum complexes bearing unsubstituted heterodiatomic Group 15 elements, [Cp₂Mo₂(CO)₄(μ,η²:η²‐PE)] (Cp=C₅H₅; E=As ( 1 ), Sb ( 2 )), with Cu^I halides afforded seven unprecedented neutral supramolecular assemblies. Depending on the Mo₂PE units and the Cu^I halide, the oligomers [?{Cp₂Mo₂(CO)₄}{μ₄,η²:η²:η²:η¹‐PE}?₄?{CuX}{Cu(μ‐X)}?₂] (E=As (X=Cl ( 3 ), Br ( 4 )); E=Sb (X=Cl ( 6 ), Br ( 7 ))) or the 1D coordination polymers [{Cp₂Mo₂(CO)₄}{μ₄,η²:η²:η¹:η¹‐PAs}{Cu(μ‐I)}]_n ( 5 ) and [{Cp₂Mo₂(CO)₄}{μ₄,η²:η²:η²:η¹‐PSb}₂{Cu(μ‐X)}₃]_n (X=I ( 8 ), Br ( 9 )) are accessible. These solid‐state aggregates are the first and only examples featuring the organometallic heterodiatomic Mo₂PE complexes 1 and 2 as linking moieties. DFT calculations demonstrate that complexes 1 and 2 present a unique class of mixed‐donor ligands coordinating to Cu^I centers via the P lone pair and the P?E σ‐bond, revealing an unprecedented coordination mode.     

Reaction of Cp2ZrCl2 with Inorganic Amides

The reactions of [η⁵‐Cp₂ZrCl₂] (Cp = η⁵‐C₅H₅) with [K(THF)_n][N(PPh₂)₂] (n = 1.25—1.5) and K[CH(PPh₂NSiMe₃)₂] are reported. The first reaction led to the monoamido complex [η⁵‐Cp₂Zr(Cl)N(PPh₂)₂] in which the {(Ph₂P)₂N}^— ligand — via a phosphorous and the nitrogen atom — is coordinated to the zirconium atom in a chelating (η²) fashion. Reaction of the potassium methanide compound, K{CH(PPh₂NSiMe₃)₂} with zirconocene dichloride yield the carbene‐like mono cyclopentadienyl complex [η⁵‐CpZr(Cl){C(PPh₂NSiMe₃)₂}]. The complex is formed by a salt metathesis and concomitant a cyclopentadiene extrusion.     

Beiträge zur Chemie des Phosphors. 227. HP4º als Komplexligand: Bildung und Eigenschaften von [(η5-C5H5)2ZrCl(P4H)], [(η5-C5Me5)2ZrCl(P4H)] und [(η5-C5H5)3Zr(P4H)]

Contributions to the Chemistry of Phosphorus. 227. HP₄º as a Complex Ligand: Formation and Properties of [(η⁵-C₅H₅)₂ZrCl(P₄H)], [(η⁵-C₅Me₅)₂ZrCl(P₄H)], and [(η⁵-C₅H₅)₃Zr(P₄H)] The novel complexes [(η⁵-C₅H₅)₂ZrCl(P₄H)] ( 1 ), [(η⁵-C₅Me₅)₂ZrCl(P₄H)] ( 2 ), and [(η⁵-C₅H₅)₃Zr(P₄H)] ( 3 ) have been obtained by reaction of a solution of (Na/K)HP₄ with the zirconocen derivatives [(η⁵-C₅H₅)₂ZrCl₂], [(η⁵-C₅Me₅)₂ZrCl₂], and [(η⁵-C₅H₅)₃(η¹-C₅ H₅)Zr] under suitable conditions. The structure of the compounds 1 – 3 , which are only stable in solution, has been elucidated by means of ³¹P-NMR spectroscopy. It is highly probable that the exo,endo isomer exists in each case. In addition, further isomers of lower relative abundancies have been observed, in which the ligands presumably exhibit a different spatial orientation relatively to each other.     

Highly active zirconium(IV) catalyst containing sterically hindered hydridotris(pyrazolyl)borate ligand for the polymerization of ethylene

The synthesis and characterization of the novel zirconium (IV) tris(pyrazolyl)borate compound {Tp^Ms*}ZrCl₃ ( 1 ) (Tp^Ms* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)), as well as its performance in polymerizing ethylene are described. The reaction of ZrCl₄ with 1 equivalent of TlTp^Ms* in toluene at room temperature affords 1 as a white solid in 62% yield. Compound 1 in the presence of MAO showed remarkable productivity using a low Al : Zr molar ratio (6.79×10⁴ kg of PE/(mol Zr·h·[C₂H₄]); toluene, 60°C, Al/Zr = 100). Under identical polymerization conditions, compound 1 and Cp₂ZrCl₂ showed comparable productivities. Compound 1 displayed similar productivities at temperatures in the range of 0–75°C and noticeable productivity at 105°C. The viscosity‐average molecular weight of the polyethylenes depends on the Al : Zr molar ratio and polymerization temperature and varied between 1.09 and 8.98×10⁵ g·mol^–1.     

Synthesis of Branched Polyethylene by Tandem Catalysis

Linear low‐density polyethylene (LLDPE) can be prepared by addition of ethylene to a mixture of two catalysts. In this “tandem catalysis” scheme one catalyst dimerizes or oligomerizes ethylene to α‐olefins while the second site incorporates these α‐olefins into a growing polyethylene chain. A variety of classical catalyst combinations are available for this purpose. Better control over the polymerization process, and therefore product properties, is attained by the use of homogenous “single site” catalysts. The best‐behaved tandem processes take advantage of well‐defined catalysts that require stoichiometric quantities of activators. One such system employs [(C₆H₅)₂PC₆H₄C(OB(C₆F₅)₃)O‐κ²P,O]Ni(η³‐CH₂CMeCH₂) and {[(η⁵‐C₅Me₄)SiMe₂(η¹‐NCMe₃)]TiMe}{MeB(C₆F₅)₃}. The nickel sites are responsible for converting ethylene to 1‐butene or mixtures of 1‐butene with 1‐hexene. These olefins are copolymerized with ethylene at the titanium sites. It is possible to obtain a linear correlation between the branching content in the polymer product and the Ni/Ti ratio. The effect of ligand substitution at nickel has also been investigated. When the benzyl derivative [(C₆H₅)₂PC₆H₄C(O‐B(C₆F₅)₃)O‐κ²P,O]Ni(η³‐CH₂C₆H₅) is used instead of the methallyl counterpart [(C₆H₅)₂PC₆H₄C(OB(C₆F₅)₃)O‐κ²P,O]Ni(η³‐CH₂CMeCH₂), one obtains, at a constant Ni/Ti ratio, considerably more branching in the final polymer structure. These results are rationalized in terms of a more efficient initiation when the more labile benzyl ligand is used.     

Synthese,Struktur und Reaktivität von η1und η3‐Allyl‐Rhenium‐Carbonylen

Synthesis, Structure, and Reactivity of η¹‐ and η³‐Allyl Rhenium Carbonyls In (η³‐C₃H₅)Re(CO)₄ one CO ligand can be substituted by PPh₃, pyridine, isocyanide and benzonitrile. With 1,2‐bis(diphenylphosphino)ethylene, 1,1′‐bis(diphenylphosphino)ferrocene and 1,2‐bis(4‐pyridyl)ethane dinuclear ligand bridged complexes are obtained. The η³‐η¹ conversion of the allyl ligand occurs on reaction of (η³‐C₃H₅)Re(CO)₄ with the bidendate ligands 1,2‐bis(diphenylphosphino)ethane and 1,3‐bis(diphenylphosphino)propane and with 2,2′‐bipyridine (L–L) which gives the complexes (η¹‐C₃H₅)Re(CO)₃(L–L). By reaction of (η³‐C₃H₅)Re(CO)₄ with bis(diphenylphosphino)methane the allyl group is protonated and under elemination of propene the complex (OC)₃Re(Ph₂PCHPPh₂)(η¹‐Ph₂PCH₂PPh₂) ( 19 ) with a diphosphinomethanide ligand is formed. On heating solutions of (η³‐C₃H₅)Re(CO)₄ and (η³‐C₃H₅)Re(CO)₃(CN‐2,5‐Me₂C₆H₃) ( 5 ) in methanol the methoxy bridged compounds Re₄(CO)₁₂(OH)(OMe)₃ and Re₂(CO)₄(CN‐2,5‐Me₂C₆H₃)₄(μ‐OMe)₂ ( 20 ) were isolated. The crystal structures of (η³‐C₃H₅)Re(CO)₃(CNCH₂SiMe₃) ( 4 ), [(η³‐C₃H₅)(OC)₃Re]₂‐ (μ‐bis‐(diphenylphosphino)ferrocene) ( 8 ), (η¹‐C₃H₅)Re(CO)₃‐ (bpy) ( 14 ), of 19 , 20 and of (OC)₃Re‐[Ph₂P(CH₂)₃PPh₂]Cl ( 16 ) were determined by X‐ray diffraction.     

Synthesis and properties of Zr-Co heterodinuclear complexes with a bridging bis(cyclopentadienyl) ligand

[(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(C₅H₅)] reacted with Co₂(CO)₈ to produce a heterodinuclear Zr(IV)-Co(I) complex [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)Co(CO)₂] (3). Complex 3 underwent oxidative addition of I₂ to give [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(CO)] (4) having Zr(IV) and Co(III) centers. The carbonyl ligand of 4 was easily replaced with P(OMe)₃ and PPh₃ to afford [(η⁵-C₅H₅)ZrCl₂(η⁵-C₅H₄)CMe₂(η⁵-C₅H₄)CoI₂(L)] (5: L = P(OMe)₃, 6: L = PPh₃). Structures of 5 and 6 were determined by X-ray crystallography. These Zr-Co heterodinuclear complexes catalyzed polymerization of ethylene and propylene.     

An unusual organoyttrium alkyl complex containing a [C5HMe3(η(3)-CH2)-C5H4N-κ]- ligand and an elusive cyclopentadienide-based scandium tuck-over zwitterion obtained by C-H bond activation

The acid–base reaction between Y(CH₂SiMe₃)₃(thf)₂ and the pyridyl‐functionalized cyclopentadienyl (Cp) ligand C₅Me₄H? C₅H₄N (1 equiv) at 0 °C afforded a mixture of two products: (η⁵:κ‐C₅Me₄? C₅H₄N)Y(CH₂SiMe₃)₂(thf) ( 1 a ) and (η⁵:κ‐C₅Me₄? C₅H₄N)₂YCH₂SiMe₃ ( 1 b ), in a 5:2 ratio. Addition of the same ligand (2 equiv) to Y(CH₂SiMe₃)₃(thf)₂, however, generated 1 b together with the novel complex 1 c , the first well defined yttrium mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)[C₅HMe₃(η³‐CH₂)‐C₅H₄N‐κ]Y(CH₂SiMe₃) containing a rare κ/η³‐allylic coordination mode in which the C? H bond activation occurs unexpectedly with the allylic methyl group rather than conventionally on Cp ring. If the central metal was changed to lutetium, the equimolar reaction between Lu(CH₂SiMe₃)₃(thf)₂ and C₅Me₄H? C₅H₄N exclusively afforded the bis(alkyl) product (η⁵:κ‐C₅Me₄? C₅H₄N)Lu(CH₂SiMe₃)₂(thf) ( 2 a ). Similarly, the reaction between the ligand (2 equiv) and Lu(CH₂SiMe₃)₃(thf)₂ gave the mono(alkyl) complex (η⁵:κ‐C₅Me₄? C₅H₄N)₂LuCH₂SiMe₃ ( 2 b ), in which no ligand redistribution was observed. Strikingly, treatment of Sc(CH₂SiMe₃)₃(thf)₂ with C₅Me₄H? C₅H₄N in either 1:1 or 1:2 ratio at 0 °C generated the first cyclopentadienide‐based scandium zwitterionic “tuck‐over” complex 3 , (η⁵:κ‐C₅Me₄? C₅H₄N)Sc(thf)[μ‐η⁵:η¹:κ‐C₅Me₃(CH₂)‐C₅H₄N]Sc(CH₂SiMe₃)₃. In the zwitterion, the dianionic ligand [C₅Me₃(CH₂)‐C₅H₄N]^2? binds both to Sc1³⁺ and to Sc2³⁺, in η⁵ and η¹/κ modes. In addition, the reaction chemistry, the molecular structures, and the mechanism are also discussed in detail.     

Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl ligands: synthesis, characterization and olefin polymerization studies

The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{η⁵-(1-Ph-3-Me-C₅H₃)}₂Cl₂] and [Zr(η⁵-C₅H₅){η⁵-(1-Ph-3-Me-C₅H₃)}Cl₂] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C₅H₃) to ZrCl₄(THF)₂ and [Zr(η⁵-C₅H₅)Cl₃ · DME] (DME = dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li₂[(Me-Ph-C₅H₂SiMe₂)₂O] to MCl₄ gave the ansa-metallocenes [M{η⁵-(Me-Ph-C₅H₂SiMe₂)₂O}Cl₂] (M = Zr, Hf) for which the meso- and rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{η⁵-(2-Me-4-Ph-C₅H₂SiMe₂)₂O}Cl₂] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts for ethene and propene polymerization was evaluated.     

μ3‐η2:η2:η2‐Coordination of Primary Silane on a Triruthenium Plane

A μ₃‐η²:η²:η²‐silane complex, [(Cp*Ru)₃(μ₃‐η²:η²:η²‐H₃SitBu)(μ‐H)₃] ( 2 a ; Cp*=η⁵‐C₅Me₅), was synthesized from the reaction of [{Cp*Ru(μ‐H)}₃(μ₃‐H)₂] ( 1 ) with tBuSiH₃. Complex 2 a is the first example of a silane ligand adopting a μ₃‐η²:η²:η² coordination mode. This unprecedented coordination mode was established by NMR and IR spectroscopy as well as X‐ray diffraction analysis and supported by a density functional study. Variable‐temperature NMR analysis implied that 2 a equilibrates with a tautomeric μ₃‐silyl complex ( 3 a ). Although 3 a was not isolated, the corresponding μ₃‐silyl complex, [(Cp*Ru)₃(μ₃‐η²:η²‐H₂SiPh)(H)(μ‐H)₃] ( 3 b ), was obtained from the reaction of 1 with PhSiH₃. Treatment of 2 a with PhSiH₃ resulted in a silane exchange reaction, leading to the formation of 3 b accompanied by the elimination of tBuSiH₃. This result indicates that the μ₃‐silane complex can be regarded as an “arrested” intermediate for the oxidative addition/reductive elimination of a primary silane to a trinuclear site.