Palladium (II) complexes with mono-oxide 1,1′-bis(diphenylphosphino)metallocene ligands [Fe(η-C5Me4PPh2)(η-C5Me4P{O}Ph2)] and [Os(η-C5H4PPh2)(η-C5H4P{O}Ph2)]

The monoxides [Fe(η⁵-C₅Me₄PPh₂)(η⁵-C₅Me₄P{O}Ph₂)] (1) and [Os(η⁵-C₅H₄PPh₂)(η⁵-C₅H₄P{O}Ph₂)] (2) have been prepared by treatment of the corresponding diphosphines with CCl₄ and methanol.These ligands react with [Pd(PhCN)₂Cl₂] to give dichloride complexes of different structure.The dimeric complex [{Os(η⁵-C₅H₄PPh₂)(η⁵-C₅H₄P{O}Ph₂)}PdCl(μ-Cl)]₂ (4) contains the monodentate P-coordinated osmocene ligand with the free P{O}Ph₂ group, while the octamethylferrocene ligand gives the chelate k²-P,O complex [{Fe(η⁵-C₅Me₄PPh₂)(η⁵-C₅Me₄P{O}Ph₂)}PdCl₂] (3).The structures of 3 and 4 have been determined crystallographically.Treatment of 3 and 4 with silver salts in CH₂Cl₂ or acetonitrile leads to the corresponding dicationic complexes[{M(η⁵-C₅R₄PPh₂)(η⁵-C₅R₄P{O}Ph₂)}Pd(MeCN)_x]²⁺ (5, M = Fe, R = Me; 6, M = Os, R = H). Complex 5 decomposes upon isolation, in contrast 6 is rather stable, probably due to Os-Pd bonding. The dichlorides 3 and 4 catalyze catalytic amination of p-bromotoluene with N-(4-tolyl)morpholine with lower activity than (dppf)PdCl₂, however they perform comparable to (dppf)PdCl₂ activity in coupling of p-bromotoluene with p-methoxyphenyl boronic acid.     

New ferrocenylmethylphosphines - Preparation, characterisation and coordination chemistry of PH(CH2Fc)2, P(CH2Fc)3 [Fc = Fe(η-C5H5)(η-C5H4)] and their derivatives

The new ferrocenylmethylphosphines PH(CH₂Fc)₂ (1) [Fc = Fe(η⁵-C₅H₅)(η⁵-C₅H₄)] and P(CH₂Fc)₃ (2) and the phosphonium salt [P(CH₂Fc)₃(CH₂OH)]I (3) were synthesised from P(CH₂OH)₃ and [FcCH₂NMe₃]I. [P(CH₂Fc)(CH₂OH)₃]Cl (4) was obtained from P(CH₂Fc)(CH₂OH)₂, CH₂O and HCl. The new phosphines and phosphonium salts were fully characterised by NMR and IR spectroscopy and MS. [Mo(CO)₆] reacts with 1 to give [Mo(CO)₅{PH(CH₂Fc)₂}] (5) in high yield, but attempts to employ 2 as a ligand failed. The reaction of [P(CH₂Fc)₃(CH₂OH)]I (3) and [PH(CH₂Fc)₃]I (obtained in situ from 3 and Na₂S₂O₅) with [WI₂(CO)₃(NCMe)₂] gave the complex salts [P(CH₂Fc)₃(CH₂OH)][WI₃(CO)₄] (6) and [PH(CH₂Fc)₃][WI₃(CO)₄] (7), respectively. [P(CH₂Fc)₄]I (8) was synthesized from PH₂CH₂Fc and [FcCH₂NMe₃]I. Crystal structures were obtained for 1, 3-8.     

Reactions of diferrocenyl dichalcogenides with [W(CO)5(THF)]: X-ray crystal structures of Fc2Te2 and [W2(μ-SeFc)2(CO)8] (Fc = [Fe(η-C5H5)(η-C5H4)])

Treatment of [W(CO)₅THF] with diferrocenyl diselenide, Fc₂Se₂, yielded the novel metal-metal bonded tungsten(I) complex, [W₂(μ-SeFc)₂(CO)₈] (1: Fc = ferrocenyl, [Fe(η⁵-C₅H₅)(η⁵-C₅H₄)]), which was characterised by NMR and IR spectroscopy, mass spectrometry, and X-ray crystallography. The corresponding tellurium derivative could not be prepared by an analogous route. The X-ray crystal structure of Fc₂Te₂ has also been determined.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(en)(X) (M = Mo, W; X = Br, N3, CN) and [(en)(η-C3H5)(CO)2M(μ-CN)M(CO)2(η-C3H5)(en)]Br (M = Mo, W)

Mononuclear compounds M(CO)₂(η³-C₃H₅)(en)(X) (X = Br, M = Mo(1), W(2); X = N₃, M = Mo(3), W(4); X = CN, M = Mo(5), W(6)) and cyanide-bridged bimetallic compounds [(en)(η³-C₃H₅)(CO)₂M(μ-CN)M(CO)₂(η³-C₃H₅)(en)]Br (M = Mo (7), W(8)) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1-6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1-4 adopt an asymmetric endo-conformation, while those of 5 and 6 were both found to possess a symmetric endo-conformation. The single crystal X-ray structures of 1-6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo-conformation in the solid state.     

Hydrogenation of cyclohexene catalyzed by ruthenium nitrosyl complexes: Crystal structures of catalyst precursors [CpRu(μ2-NO)2RuCp] and [CpRu(NO)(η-C6H10)] (Cp = η-C5(CH3)5)

Hydrogenation of cyclohexene with 0.1 mol% of the (nitrosyl)ruthenium catalyst [Cp^∗Ru(NO)(C₆H₅)₂] (1; Cp^∗ = η⁵-C₅(CH₃)₅) under 1.0 MPa of H₂ in water at 90 °C for 13 h afforded cyclohexane in 94% yield. The nitrosyl-bridged dinuclear complex [Cp^∗Ru(μ₂-NO)₂RuCp^∗] (2) and the mononuclear cyclohexene complex [Cp^∗Ru(NO)(η²-C₆H₁₀)] (3), which also serve as catalyst precursors, have been obtained from the reaction mixture. X-ray crystallographic analyses of 2 and 3 have revealed that the bridging nitrosyl ligands in 2 form an almost planar Ru₂N₂ four-membered ring with the Ru–Ru distance of 2.5366(5) Å, whereas the nitrosyl ligand in 3 is linear. On the other hand, a ruthenium complex without a nitrosyl ligand [Cp^∗Ru(CH₃CN)₃][OSO₂CF₃] proved to be less effective for this hydrogenation.     

A synthetic, structural and reactivity study of [(η-C4R4)Co(η-C5H4X)] complexes, R = Me or Et; X = CHO, CHCHFc, CHCH(η-C5H4)Co(η-C4Ph4), CHC(CN)2: Unexpected formation of [(η-cyclopentadienyl)(η-3,4,5,6-tetraethyl-α-pyrone)cobalt]

The tetraethyl- and tetramethyl-cyclobutadiene complexes [(η⁴-C₄R₄)Co(η⁵-C₅H₄CHO)] R = Et, 5, R = Me, 7, and [(η⁴-C₄R₄)Co(η⁵-C₅H₄CO₂Me)] R = Et, 6, R = Me, 8, are conveniently prepared by photolysis of the corresponding isocobaltocenium cations [(η⁴-C₄R₄)Co(η⁶-C₆H₅Me)]⁺ in acetonitrile, and subsequent treatment with Na[C₅H₄CHO] or Na[C₅H₄CO₂Me]. The aldehydes 5 and 7 undergo Wittig and Knoevenagel reactions with [FcCH₂PPh₃]I and CH₂(CN)₂, to form [(η⁴-C₄R₄)Co(η⁵-C₅H₄CH=CHFc)] and [(η⁴-C₄R₄)Co(η⁵-C₅H₄CH=C(CN)₂], 11 and 15, respectively. The Horner-Wittig reaction of [(η⁴-C₄R₄)Co(η⁵-C₅H₄CH₂P(O)(OEt)₂] with [(η⁴-C₄Ph₄)Co(η⁵-C₅H₄CHO)] yields [(η⁴-C₄R₄)Co(η⁵:η⁵-C₅H₄CHCH-C₅H₄)Co(η⁴-C₄Ph₄)], 12 and 13. [(η⁴-C₄Me₄)Co(η⁵-C₅H₄CHO)] also reacts with t-BuLi and FcLi to furnish the corresponding secondary alcohols, 16 and 17, respectively. Surprisingly, the attempted direct synthesis of 5 by reaction of Na[C₅H₅] and ethyl formate with [(η⁴-C₄Et₄)Co(CO)₂I], 1, instead yielded [(η⁵-C₅H₅)Co(η⁴-3,4,5,6-tetraethyl-α-pyrone)], 18, and a mechanistic proposal is advanced. The X-ray crystal structures of 1, 7, 8, 11(Z), 15 and 18, and also the isocobaltocenium salts [(η⁴-C₄Et₄)Co(η⁶-C₆H₅Me)][PF₆], 2, and [(η⁴-C₄Et₄)Co(η⁶-1,3,5-C₆H₃Me₃)][PF₆], 4, are reported.     

Stereoselective syntheses of substituted succinic acid derivatives of the iron chiral auxiliary [(η-C5H5)Fe(CO)(PPh3)]

A range of alkyl- or aryl-substituted iron succinoyl complexes, incorporating the iron chiral auxiliary [(η⁵-C₅H₅)Fe(CO)(PPh₃)], were prepared in high regio- and diastereoselectivities by employing four successful strategies: (i) the alkylation of chiral enolate equivalents with tert-butyl bromoacetate; (ii) the mutual kinetic resolution of tert-butyl α-bromoacetate with a chiral acetate enolate equivalent; (iii) the alkylation of chiral succinoyl enolate equivalents; (iv) the conjugate addition of organolithium reagents or lithium amide reagents to chiral fumaroyl derivatives. Oxidative cleavage of the iron chiral auxiliary was shown to occur without compromising the stereochemical integrity of the succinoyl fragments.     

Hydrolytic disproportionation of coordinated white phosphorus in [CpRu(dppe)(η-P4)]PF6 [dppe = 1,2-bis(diphenylphosphino)ethane]

The reaction of [CpRu(dppe)Cl] (1), dppe = 1,2-bis(diphenylphosphino)ethane, with one equivalent of P₄ in the presence of TlPF₆ affords the stable complex [CpRu(dppe)(η¹-P₄)]PF₆ (2) which contains the tetrahedral P₄ molecule η¹-bound to the metal. The tetraphosphorus ligand readily reacts with water upon mixing acetone or THF solutions of the complex with excess water. The complexes [CpRu(dppe)(PH₃)]PF₆ (5) and [CpRu(dppe){P(OH)₃}]PF₆ (6), identified among the hydrolysis products, contain the PH₃ molecule and, respectively, the unstable P(OH)₃ tautomer of the phosphorous acid bound to the CpRu(dppe) fragment. In CH₂Cl₂ the coordinated P(OH)₃ molecule in 6 easily yields the compound [CpRu(dppe){PF(OH)₂}]PF₂O₂ (8), via hydrolysis of the hexafluorophosphate anion and F/OH substitution in the coordinated P(OH)₃ molecule. All the compounds have been characterized by elemental analyses and NMR measurements. The crystal structures of 2 and 8 have been determined by X-ray diffraction methods.     

Stilbene analogues incorporating the Co(η-C4Ph4)(η-C5H4-) end group

A number of organometallic stilbenes of the general type [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHR] are reported where R is C₆H₄X-4 (X = H, OMe, Br, NO₂), 1-naphthyl, 9-anthryl, 1-pyrenyl, (η⁵-C₅H₄)Co(η⁴-C₄Ph₄), and (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y) {Y = CHO, CHC(CN)₂ and CHCHC₅H₄-η⁵)Co(η⁴-C₄Ph₄)}. They were prepared by Wittig or Horner-Wadsworth-Emmons reactions which yield both E and Z or only E products respectively. The isomers were separated and all compounds characterised by standard spectroscopic techniques as well as by X-ray diffraction methods in many cases. The electrochemistry of the stilbene analogues in dichloromethane solution is also reported. In most, the (η⁵-C₅H₄)Co(η⁴-C₄Ph₄) functional group undergoes a reversible one-electron oxidation. For those molecules that also include (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y), this is preceded by the reversible oxidation of the ferrocenyl group. Spectroscopic and structural data suggests that for most compounds there is little electronic interaction between Co(η⁴-C₄Ph₄)(η⁵-C₅H₄) and the R end groups which are effectively independent of one another. The only exceptions to this are Z and E-[Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHC₆H₄NO₂-4], and [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHC₅H₄-η⁵)Fe{η⁵-C₅H₄CHC(CN)₂}] where the electronic spectra are respectively consistent with a significant Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)/NO₂ donor/acceptor interaction and a less significant Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)/C(CN)₂ one. However, OTTLE studies show that in the electronic spectra of [Co(η⁴-C₄Ph₄)(η⁵-C₅H₄CHCHR]⁺ there are low energy absorption bands (950-1800 nm) which are attributed to R → Co(η⁴-C₄Ph₄)(η⁵-C₅H₄)⁺ or, when R is a ferrocenyl-base group, Co(η⁴-C₄Ph₄)(η⁵-C₅H₄) → (η⁵-C₅H₄)Fe(η⁵-C₅H₄Y)⁺ charge transfer transitions. The ferrocenyl compounds undergo cis/trans isomerisation on the OTTLE experiment timescale.     

Discovering the chemical reactivity of the molecular oxonitride [{Ti(η-C5Me5)(μ-O)}3(μ3-N)]

The ability of the oxonitride [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-N)] (1) to act as an organometallic ligand has been studied from both theoretical and experimental points of view. DFT calculations have allowed understanding the electronic structure of 1, and rationalizing its chemical behavior by comparison with the electronic structures of isoelectronic species [{Ti(η⁵-C₅Me₅)(μ-O)}₃(μ₃-CH)] and [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)]. Reactions of 1 with different inorganic molecules such as [Mo(CO)₃(1,3,5-Me₃C₆H₃)] or AlEt₃ have confirmed the possibility of 1 to act as a tridentate or monodentate ligand to give the [{(CO)₃Mo}(μ₃-O)₃{Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (2) and [{Et₃Al}(μ₃-O){(μ-O)₂Ti₃(η⁵-C₅Me₅)₃(μ₃-N)}] (3) complexes, respectively. Surprisingly, reactions of 1 with [M(CO)₆] (M = Cr, Mo, W) complexes led to activate the μ₃-N unit in 1 to afford the new compounds [Ti₃(η⁵-C₅Me₅)₃(μ-O)₄{(NC)M(CO)₅}]₂ [M = Cr (4), Mo (5), W (6)]. Molecular structures of complexes 2-6 have been established by single crystal X-ray analysis.     

Synthesis, characterization and catalytic behaviour of ansa-zirconocene complexes containing tetraphenylcyclopentadienyl rings: X-ray crystal structures of [Zr{Me2Si(η-C5Ph4)(η-C5H3R)}Cl2] (R = H, Bu)

The ansa-bis(cyclopentadiene) compounds, Me₂Si(C₅HPh₄)(C₅H₄R) (R = H (2); Bu^t (3)), have been prepared by the reaction of C₅HPh₄(SiMe₂Cl) (1) with Na(C₅H₅) or Li(C₅H₄Bu^t), respectively, and transformed to the di-lithium derivatives, Li₂{Me₂Si(C₅Ph₄)(C₅H₃R)} (R = H (4); Bu^t (5)), by the action of n-butyllithium. The ansa-zirconocene complexes, [Zr{Me₂Si(η⁵-C₅Ph₄)(η⁵-C₅H₃R)}Cl₂] (R = H (6); Bu^t (7)), were synthesized from the reaction of ZrCl₄ with 4 or 5, respectively. Compounds 6 and 7 have been tested in the polymerization of ethylene and compared with their methyl-substituted analogues, [Zr{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃R)}Cl₂] (R = H (8); Bu^t (9)). Whilst 8 and 9 are catalytically active, the tetraphenyl-substituted complexes 6 and 7 proved to be inactive in the polymerization of ethylene. This phenomenon has been explained by DFT calculations based on the reaction intermediates in the polymerization processes involving 6 and 7, which showed that the extraction of a methyl group from the zirconocene complex to form the cationic active specie is endothermic and therefore unfavourable.     

Facile synthesis and X-ray structures of (η-C5Me5)Ti(OAr)3 (OAr = OC6F5, OCH2C6F5, and OCH2C6F2H3)

New half-sandwich titanocene complexes (η⁵-C₅Me₅)Ti(OC₆F₅)₃ (1), (η⁵-C₅Me₅)Ti(OCH₂C₆F₅)₃ (2), and (η⁵-C₅Me₅)Ti(OCH₂C₆F₂H₃)₃ (3) were synthesized via the displacement of methoxide ligands in (η⁵-C₅Me₅)Ti(OMe)₃ by the corresponding aryloxy or benzyloxy ligands. These compounds have been fully characterized by various spectroscopic methods including X-ray crystallography. Compound 1 has a distorted three-legged piano stool structure. However, complexes 2 and 3 have the chariot-like structure, where chariot means a two-wheeled horse-drawn vehicle. The π electron donation of oxygen atom to Ti center in complexes 1-3 is considerable.     

Hexadecahydrotetrabenzo[a,c,d,f]fluorene - Ligand, available by Friedel-Crafts fluorene cycloalkylation. Synthesis, crystal and molecular structure of (η-C29H34)(η-C5H5)ZrCl2

Friedel-Crafts cycloalkylation of fluorene with 1,4-dichlorobutane has been studied in different conditions. This reaction allows to obtain the product of exhausting fluorene alkylation, hexadecahydrotetrabenzo[a,c,d,f]fluorene - perspective η⁵ ligand. The simplest zirconocene has been synthesized and its structure has been confirmed by X-ray diffraction analysis. The molecule of this compound possesses skewed conformation of metallocene fragment with the phenylene moiety of fluorenyl ligand oriented towards the front side of metallocene wedge.     

Synthesis and structure of the monometallic cationic complex [Cp(CO)2Fe{η-(CH2CHCH2CH3)}]PF6 (Cp = η-C5H5)

The bimetallic carbocation complex [{Cp(CO)₂Fe}₂(μ-C₄H₇)]PF₆ reacted with trifluoroacetic acid to give the mononuclear cationic complex [Cp(CO)₂Fe{η²-(CH₂CHCH₂CH₃)}]PF₆, which formed yellow orthorhombic crystals in the space group P2₁2₁2₁ with a = 7.652(4), b = 13.422(7), c = 14.037(7); α = β = γ = 90.00 and Z = 4. The carbocation is coordinated to the metal in a η²-fashion forming a chiral metallacyclopropane type structure. The β-CH carbon (C9) is disordered over two positions (C9A and C9B), each having about 50% occupancy. This is attributed to there being both the R and S enantioface isomers in equal amounts in the crystal sample. NMR data indicate that the metallacyclopropane structure observed in the solid state is preserved in solution.     

Mechanistic studies on reaction of [ReH4(η-H2)(Cyttp)] with ketones to give the hydrido-oxo complex [ReH2(O)(Cyttp)] (Cyttp = PhP(CH2CH2CH2PCy2)2)

Mechanistic studies were conducted on reaction of [ReH₄(η²-H₂)(Cyttp)]OTf (1(OTf); Cyttp = PhP(CH₂CH₂CH₂PCy₂)₂, OTf = O₃SCF₃) with ketones, both neat and in solution. Treatment of 1(OTf) with excess acetone at 60-65 °C affords [ReH₂(O)(Cyttp)]OTf (2(OTf)) in high yield, nearly 1 equiv. of H₂, 2 equiv. of 2-propanol, 1 equiv. of each of 4-hydroxy-4-methyl-2-pentanone (B) and 4-methylpent-3-en-2-one (C), and smaller amounts of other organic products derived by condensation or related reactions of acetone. The presence of C, apparently arising by dehydration of B, points to the formation of 1 equiv. of H₂O in the reaction system. Use of acetone-d₆ in conjunction with 1(OTf) gives 2(OTf) containing no deuterium, as well as 1 equiv. of each of (CD₃)₂CHOH/OD and (CD₃)₂CDOD/OH. Reactions of 1(OTf) with cyclohexanone, including cyclohexanone-2,2,6,6-d₄, under comparable conditions, give analogous results. The ketones cyclopentanone, 2-butanone, and 3-pentanone also convert 1(OTf) to 2(OTf) upon heating, as does isobutyraldehyde, but only in the presence of the stabilizer BHT. In contrast, the more robust ketones 2,4-dimethyl-3-pentanone, 2,6-dimethylcyclohexanone, and 2-adamantanone, which do not undergo condensation, failed to effect this transformation. Other organooxygen compounds, i.e., methanol, cyclohexanol, 1,2-butene oxide, cyclohexene oxide, DMSO, and Me₃NO, also are ineffective. A mechanism is proposed which begins with loss of H₂ by 2 to give a 16-electron “[ReH₄(Cyttp)]⁺” which, depending on the experimental conditions, binds a solvent or ligand molecule. A [ReH₄(R₂CO)(Cyttp)]⁺ intermediate generated in this manner reacts spontaneously by elimination of R₂CHOH (containing methine hydrogen even when deuteriated ketone is used), which results from transfer of two hydride ligands to coordinated ketone. Continued reaction leads to the formation of 2 and another molecule of R₂CHOH (containing methine deuterium when deuteriated ketone is employed), with the added hydrogens coming from H₂O, which derives from solvent/reactant ketone.     

Effect of high external pressures on the vibrational spectra of Zeise’s complexes, K[Pt(η-C2H4)Cl3] and [Pt(η-C2H4)Cl2]2

The pressure dependences (dν/dP) of the main IR and Raman bands of Zeise’s complexes, K[Pt(η²-C₂H₄)Cl₃] and [Pt(η²-C₂H₄)Cl₂]₂, have been determined for the first time for selected pressures up to ∼33 kbar with the aid of diamond-anvil cells. Neither complex undergoes a pressure-induced structural change throughout the pressure range investigated. The dν/dP values range from −0.13 to 0.79 cm⁻¹ kbar⁻¹. The negative values have proved particularly informative in identifying the location of the CC stretching modes of the Pt-ethylene groups, a topic of considerable disagreement in the literature.     

(Cyclopentadienyl){(N,N-dimethylaminoethyl)cyclopentadienyl} complexes of zirconium: Crystal structure of [(η-C5H5)(η-C5H4CH2CH2NHMe2)ZrCl2]2[ZrCl6]

[(η⁵-C₅H₅)ZrCl₃] reacts with [C₅H₄CH₂CH₂NMe₂]Li yielding the coordination polymer [(C₅H₅)(C₅H₄CH₂CH₂NMe₂)ZrCl₂]_n (1) as a brown solid which is very sensitive to moisture. The reaction of 1 with 1.35 equivalent of HCl (methanolic solution) yields pale yellow green crystals of [(η⁵-C₅H₅)(η⁵-C₅H₄CH₂CH₂NHMe₂)ZrCl₂]₂[ZrCl₆] (2). Compound 2 was fully characterized on the basis of NMR data and X-ray crystal structure analysis. The formation of this product indicates the elimination of C₅H₄CH₂CH₂NMe₂ as well as C₅H₅ ligands from the Zr(IV) metal centre.