Variable hapticity of the cyclooctatetraene ring in sandwich compounds of the first row transition metals

Density functional theory methods (B3LYP and BP86) indicate that the preferred structures for such early transition metal derivatives are (η⁸-C₈H₈)M(η⁴-C₈H₈) (M = Ti, V, Cr) with one octahapto η⁸-C₈H₈ ring and one tetrahapto η⁴-C₈H₈ ring. In such structures only 12 of the 16 carbon atoms of the two C₈H₈ rings are bonded to the metal, leading to 16-, 17-, and 18-electron complexes, respectively, in accord with the experimentally known structures for the Ti and V derivatives. The preferred structures for the Mn and Fe derivatives are (η⁶-C₈H₈)M(η⁴-C₈H₈) (M = Mn, Fe) with one hexahapto and one tetrahapto C₈H₈ ring and thus having 17- and 18-electron configurations, respectively, in accord with experimental data on the iron complex. The lowest energy structure for the cobalt complex is (η⁴-C₈H₈)Co(η^2,2-C₈H₈) with two different types of tetrahapto C₈H₈ rings and a 17-electron metal configuration. The nickel complex (C₈H₈)₂Ni appears to prefer a structure with a 16-electron configuration and two trihapto C₈H₈ rings, similar to the known (η³-C₃H₅)₂Ni rather than a bis(tetrahapto) structure with the favored 18-electron configuration. These theoretical studies indicate that in (C₈H₈)₂M derivatives of the first row transition metals, the number of carbon atoms in the pair of C₈H₈ rings involved in the bonding to the central metal atom gives the metal atoms 16-, 17-, or 18-electron configurations.     

Reaktionen der Cycloheptatrienylkomplexe [η7-C7H7W(CO)3]BF4 und η7-C7H7Mo(CO)2 Br mit Neutralliganden und die elektrochemische Reduktion des Wolframkomplexes

Reactions of the Cycloheptatrienyl Complexes [η⁷-C₇H₇W(CO)₃]BF₄ and η⁷-C₇H₇Mo(CO)₂Br with Neutral Ligands and the Electrochemical Reduction of the Wolfram Complex Compounds of the type [η⁷-C₇H₇M(CO)₂L][BF₄] (L = P(C₆H₅)₃, As(C₆H₅)₃, Sb(C₆H₅)₃ for M = W and L = N₂H₄ for M = Mo) were synthesized and characterisized. The iodide η⁷-C₇H₇W(CO)₂I reacts with the diphosphine ((C₆H₅)₂PCH₂)₂ to give the trihapto complex η³-C₇H₇ W(CO)₂I((C₆H₅)₂PCH₂)₂. In the case of η⁷-C₇H₇Mo(CO)₂ Br reaction with hydrazine leads to the substitution product [η⁷-C₇H₇ Mo(CO)₂N₂H₄]^⊕, which can be stabilized by large anions. The binuclear complex [C₇H₇W(CO)₃]₂ has been synthesized electrochemically.     

Synthesis and structure of mono- and dinuclear cyclopentadienyl–indenyl complexes of iron(II) and further reactions to mixed tri- and tetranuclear iron–cobalt complexes

The reaction of a mixture of sodium cyclopentadienide and the monolithium salt or dilithium salt of 2,2-bis(indenyl)propane with FeCl₂ leads to the mononuclear complex [(η⁵-C₅H₅)Fe(η⁵-ind-C(CH₃)₂-ind)] (ind = 1-indenyl) (1) and the dinuclear complex [{(η⁵-C₅H₅)Fe(η⁵-ind)}₂C(CH₃)₂] (2), respectively. [(η⁵-Me₅C₅)Fe(tmeda)Cl] reacts with dilithium 1,1′-biindenyl under formation of [{(η⁵-Me₅C₅)Fe}₂(μ-η⁵:η⁵-1,1′-biind)] (4). Due to the annelated arene rings of the η⁵-indenyl ligands, 2 and 4 may act as 4-electron donor ligands, as exemplified by the reaction with the triple-decker complex [{(η⁵-Me₅C₅)Co}₂(μ-η⁶:η⁶-toluene)], which afforded the tetranuclear dimer of triple-decker complexes [{(η⁵-C₅H₅)Fe(η⁵-Me₅C₅)Co(μ-η⁵:η⁴-1-ind)}₂C(CH₃)₂] (3) and the trinuclear complex [{(η⁵-Me₅C₅)Fe}₂(η⁵-Me₅C₅)Co(μ₃-η⁵:η⁴:η⁵-1,1′-biind)] · Et₂O (5 · Et₂O) by replacement of the central toluene deck, respectively. The [(η⁵-Me₅C₅)Co] fragments of 3 and 5 are bonded via the six-membered rings of the indenyl ligands in a η⁴-fashion. Caused by the coordination to the Co atoms the six-membered rings lose their planarity and adopt a butterfly structure. The coordination geometry of the Fe atoms is similar in all five complexes. Each Fe atom is coordinated by the C atoms of one of the five-membered rings of the indenyl ligands in a slightly distorted η⁵ manner (η³ + η²-coordination) and by a cyclopentadienyl ligand in a regular η⁵-fashion. The structures of 3 and 5 represent the first examples of slipped triple-decker complexes which comprise indenyl ligands in a μ-η⁵:η⁴ coordination mode.     

Synthesis of Cationic 2,4-Dimethylpenta-2,4-dienylruthenium Complexes. Crystal Structure of Carbonyl(η4-cyclohexa-1,3-diene)-(η5-2,4-dimethylpenta-2,4-dienyl)ruthenium Tetrafluoroborate

The complex [Ru(η⁵-C₇H₁₁)₂H]BF₄ (C₇H₁₁ = 2,4-dimethylpenta-2,4-dienyl) is highly reactive towards two- and six-electron ligands. e.g. giving with CO complex [RuCO(η⁴-C₇H₁₂)(η⁵-C₇H₁₁)]BF₄. The 2,4-dimethylpenta-1,3-diene ligand (C₇H₁₂) of the latter complex is readily displaced giving, e.g. with excess cyclohexa-1,3-diene (C₆H₈) complex [RuCO(η⁴-C₆H₈)(η⁵-C₇H₁₁)]BF₄. These reactions provide a convenient entry into monopentadienylruthenium chemistry.     

Metal-Assisted Opening of Intact P4 Tetrahedra

The reactivity of ruthenium and manganese complexes bearing intact white phosphorus in the coordination sphere was investigated towards the low-valent transition-metal species [Cp′′′Co] (Cp′′′=η⁵-C₅H₂-1,2,4-tBu₃) and [L⁰M] (L⁰=CH[CHN(2,6-Me₂C₆H₃)]₂; M=Fe, Co). Remarkably, and irrespective of the metal species, the reaction proceeds by the selective cleavage of two P–P edges and the formation of a square-planar cyclo-P₄ ligand. The reaction products [{CpRu(PPh₃)₂}{CoCp′′′}(μ,η^1:4-P₄)][CF₃SO₃] ( 5 ), [{Cp^BIGMn(CO)₂}₂{CoCp′′′}(μ,η^1:1:4-P₄)] ( 6 ) and [{Cp^BIGMn(CO)₂}₂{ML⁰}(μ,η^1:1:4-P₄)] (Cp^BIG=C₅(C₆H₄nBu)₅; L⁰=CH[CHN(2,6-Me₂C₆H₃)]₂; M=Fe ( 7 a ), Co ( 7 b )), respectively, were fully characterized by single-crystal X-ray diffraction and spectroscopic methods. The electronic structure of the cyclo-P₄ ligand in the complexes 5 – 7 is best described as a π-delocalized P₄²⁻ system, which is further stabilized by two and three metal moieties, respectively. DFT calculations envisaged a potential intermediate in the reaction to form 5 , in which a quasi-butterfly-shaped P₄ moiety bridges the two metals and behaves as an η³-coordinated ligand towards the cobalt center.     

Darstellung und Charakterisierung von kationischen η2-1-Buten- und Acetonitrilkomplexen

Preparation and Characterization of Cationic η²-1-Butene and Acetonitrile Complexes The reaction of the species η⁵-C₅H₅M(CO)_n-σ-C₄H₇ (M = Fe, Mo, W; n = 2, 3) with (C₆H₅)₃CBF₄ yielded – instead of the expected cationic butadiene complexes of the type [η⁵-CpM(CO)_n?1-η⁴-C₄H₆][BF₄], which would have been formed in case of hydride cleavage – compounds of the type [η⁵-CpM(CO)_n η²-C₄H₈][BF₄], which were formed by protonation of the σ-C₄H₇ ligands. The reaction proceeded quantitatively. The BF₄^? anion can be substituted by other anions, such as ClO₄^?, B(C₆H₅)₄^?, PF₄^?, and [Cr(SCN)₄(NH₃)₂]^? in the complexes obtained. The mechanism of the reaction leading to the η²-bonded 1-butene complexes was determined by isotope experiments. In trying to recrystallize the butene complexes from acetonitrile the cationic complexes [η⁵-C₅H₅ Fe(CO)₂CH₃CN]BF₄ and [η⁵-C₅H₅ M(CO)₃CH₃CN]BF₄ were observed; the X-ray structure analysis of the former is reported.     

Synthesis and properties of a thermally stable methyltitanium(IV) compound: Cyclopentadienylmethyldichlorotitanium(IV)

η⁵C₅H₅Ti(CH₃)Cl₂ and η⁵-C₅H₅Ti(C₂H₅TiCl₂ have been synthesized. The reactivity of the methyl compound is much greater than that of the closely related sandwich compound, (η⁵-C₅H₅)₂Ti(CH₃)Cl, but the thermal stability is comparable.     

Tris(Butadiene) Compounds versus Butadiene Oligomerization in Second-Row Transition Metal Chemistry: Effects of Increased Ligand Fields

The geometries, energetics, and preferred spin states of the second-row transition metal tris(butadiene) complexes (C₄H₆)₃M (M = Zr–Pd) and their isomers, including the experimentally known very stable molybdenum derivative (C₄H₆)₃Mo, have been examined by density functional theory. Such low-energy structures are found to have low-spin singlet and doublet spin states in contrast to the corresponding derivatives of the first-row transition metals. The three butadiene ligands in the lowest-energy (C₄H₆)₃M structures of the late second-row transition metals couple to form a C₁₂H₁₈ ligand that binds to the central metal atom as a hexahapto ligand for M = Pd but as an octahapto ligand for M = Rh and Ru. However, the lowest-energy (C₄H₆)₃M structures of the early transition metals have three separate tetrahapto butadiene ligands for M = Zr, Nb, and Mo or two tetrahapto butadiene ligands and one dihapto butadiene ligand for M = Tc. The low energy of the experimentally known singlet (C₄H₆)₃Mo structure contrasts with the very high energy of its experimentally unknown singlet chromium (C₄H₆)₃Cr analog relative to quintet (C₁₂H₁₈)Cr isomers with an open-chain C₁₂H₁₈ ligand.     

Synthesis of allyl-transition metal complexes by phase transfer catalyzed reactions of metal carbonyl halides: III. Considerations of the mechanisms

Mechanisms are proposed for the hydroxide ion-initiated reactions of metal carbonyl halides which lead to allyl-transition metal complexes under phase transfer conditions. Evidence is presented for intermediate anionic metallocarboxylic acids in reactions leading to η³-allyl products of molybdenum, iron, ruthenium and manganese, whereas η¹ complexes are shown to result from halide displacement reactions in which simple metal carbonyl anions are generated. In some cases phosphorus-containing ligands inhibit the hydroxide-promoted reactions of metal carbonyl halides with allyl bromide; a rationale involving decreased acidity of the carbonyl ligands is presented. Syntheses of η³-C₃H₅Mn(CO)₃P(OCH₃)₃ and η³-C₃H₅Mn(CO)₂[P(OCH₃)₃]₂ by phase transfer catalysis are also described.     

Zur kenntnis der cyclopentadienyl-nitrosyl-carbonyl-isonitril-komplexe der VI. Und der cyclopentadienyl-dicarbonyl-isonitril-komplexe der VII. Nebengruppe

The nitrosylcarbonylisonitrile complexes η⁵-C₅H₅M(NO)(CO)CNR (R = Me for Cr, Mo, W; R = Et, SiMe₃, GeMe₃, SnMe₃ for Mo) are formed by treatment of the nitrosylcarbonylcyanometalates Na[η⁵-C₅H₅M(NO)(CO)CN] with [R₃O]BF₄ (R = Me, Et), Me₃SiCl, Me₃GeCl or Me₃SnCl. The isoelectronic dicarbonylisonitrile compounds η⁵-C₅H₅Mn(CO)₂CNR (R = SiMe₃, GeMe₃, SnMe₃, PPh₂, AsMe₂) and η⁵-C₅H₅Re(CO)₂CNAsMe₂ are obtained by analogous reactions of Na[η⁵-C₅H₅M(CO)₂CN] (M = Mn, Re) with Me₃ECl (E = Si, Ge, Sn), Ph₂PCl and Me₂AsBr.With phosgene the anionic complexes Na[η⁵-C₅H₅M(CO)₂CN] (M = Mn, Re) can be transformed into the new carbonyldiisocyanide-bridged dinuclear complexes η⁵-C₅H₅M(CO)₂CN-C(O)-NC(OC)₂M-η⁵-C₅H₅. Finally, the reactions of η⁵-C₅H₅M(NO)(CO)CNMe (M = Cr, Mo, W) with NOPF₆, leading to the cationic dinitrosylisonitrile complexes [η⁵-C₅H₅M(NO)₂CNMe]⁺, are described.     

Fluorenyl based syndiotactic specific metallocene catalysts structural features,origin of syndiospecificity

The stereochemistry of propylene insertion/propagation reactions with a variety of C_s symmetric fluorenyl- containing single site catalysts is discussed. Our recent results indicate that independent of the chemical composition of the ancillary ligand fragments, or nature of the transition metal, active sites with local C_s symmetry and enantiotopic coordination positions behave syndioselectively in the general context of chain migratory insertion mechanism. Perfect bilateral symmetry neither exists nor is required in these processes. In this context the mechanism of syndiospecific polymerization is revisited by taking into account the structural characteristics and catalytic behavior of the original metallocene based (η⁵-C₅H₄-CMe₂-η⁵-C₁₃H₈) MCl₂/ MAO; M = Zr ( 1 ), Hf ( 2 ) catalyst systems and new syndiotactic specific systems including (η⁵-C₅H₄-CPh2-η5-3,6-di-tBut-C₁₃H₆)ZrCl₂ ( 3 ), η¹,η⁵-(μMe₂Si)(3,6-di-tBut-Flu)(t-ButN)MCl₂/ MAO; M =Ti ( 4 ), Zr ( 5 ) and η¹,η⁵-(μMe₂Si)(2,7-di-tBut-Flu)(t-ButN)MCl₂/ MAO; M = Ti ( 6 ), Zr ( 7 ).     

Studies in negative ion mass spectrometry. VIII—Electron capture by some monomeric and dimeric η5—cylcopentadienyl transition metal carbonyls

The negative ion mass spectra of a series of monomeric and dimeric η⁵-cyclopentadienyl transition metal carbonyls have been examined. The base peak in the case of the monomeric compounds (η⁵-C₅H₅)V(CO)₄, (η⁵-C₅H₅)Mn(CO)₃ and (η⁵-CH₃C₅H₄)Mn(CO)₃ arises from a reductive decarbonylation of the parent molecule—the resulting radical anion [M–CO]^? is formally isoelectronic with the molecular cations [M]^? observed in the positive ion mass spectra of these compounds and subsequently undergoes successive decarbonylations to the ‘aromatic’ cyclopentadienyl anions. For the compound (η⁵-C₅H₅)Co(CO)₂, however, a molecular anion was observed as the base peak which has been formulated as [(η³-C₅H₅)Co(CO)₂]^? in the light of considerations based on the rare gas rule. As expected, the dimeric molecules [(η⁵-C₅H₅)M(CO)₃]₂ (where M = Cr or Mo) and [(η⁵-C₅H₅)Fe(CO)₂]₂ (and its methyl analogue) undergo reductive cleavage of their metal-metal bonds to give the anions [(η⁵-C₅H₅)M(CO)₃]^? and [(η⁵-C₅H₅)Fe(CO)₂]^? as the base peaks in their negative ion mass spectra. The dimeric nickel compound [(η⁵-C₅H₅)Ni(CO)]₂, however, reductively decarbonylates to the [M-CO]^? radical anion as its predominant fragmentation in the gas phase. Very low abundances of [(η⁵-C₅H₅)Fe(CO)₂] and [(η⁵-CH₃C₅H₄)Fe(CO)₂] were also observed.     

Synthese und Charakterisierung neuer Acetylenkomplexe des Mangans und Rheniums

The reaction of the photochemically-generated tetrahydrofuran complexes Cp′(CO)₂M(thf) (Cp′  η⁵-C₅H₅, η⁵-C₅H₄Me, η⁵-C₅Me₅; M  Mn, Re) with various alkynes R¹C₂R² (R¹, R²  H, Me, Ph) yields are acetylene complexes Cp′(CO)₂MR¹C₂R². These compounds were identified from their IR, ¹H NMR, ¹³C NMR and mas spectra.     

Octahapto cyclooctatetraene rings and metal-metal multiple bonds in binuclear niobium carbonyl chemistry

Theoretical studies on (C₈H₈)₂Nb₂(CO)_n (n = 6, 5, 4, 3, 2, 1) predict structures mainly with octahapto and tetrahapto C₈H₈ rings. In all cases, the lowest energy singlet spin state structures lie below the corresponding lowest energy triplet spin state structures. Thus the lowest energy (C₈H₈)₂Nb₂(CO)₄ structure has two η⁸-C₈H₈ rings and an unbridged Nb-Nb single bond of length ∼3.15 Å. The lowest energy (C₈H₈)₂Nb₂(CO)₂ structure has two η⁸-C₈H₈ rings but a doubly bridged NbNb triple bond of length ∼2.64 Å. The lowest energy structure of (C₈H₈)₂Nb₂(CO)₃ also has a formal NbNb triple bond of similar length (2.66 Å) but with only one of the rings fully coordinated as an octahapto η⁸-C₈H₈ ligand. The other C₈H₈ ring in this tricarbonyl has “slipped” to form a hexahapto η⁶-C₈H₈ ligand. The lowest energy structure of the monocarbonyl (C₈H₈)₂Nb₂(CO) again has two octahapto η⁸-C₈H₈ rings and an extremely short NbNb distance of 2.45 Å, suggesting a formal quadruple bond. The lowest energy structures for the carbonyl-richer species (C₈H₈)₂Nb₂(CO)_n (n = 6, 5) have one η⁸-C₈H₈ and one η⁴-C₈H₈ ring (n = 5) and two η⁴-C₈H₈ rings (n = 6). The qualitatively assigned Nb-Nb bond orders are consistent with the Wiberg bond indices obtained from the Weinhold natural bond orbital analysis. Comparison of the (C₈H₈)₂Nb₂(CO)_n (n = 6, 5, 4, 3, 2, 1) derivatives with the isovalent (C₇H₇)₂Mo₂(CO)_n is made.     

Säureinduzierte carbin-acylumwandlung

The reaction of dicarbonyl- and carbonyl(trimethylphosphine)(cyclopentadienyl)-carbyne complexes of molybdenum and tungsten η⁵-C₅H₅(CO)_2−n(PMe₃)_nMCR (n = 0, 1; M = Mo, W; R = CH₃, C₆H₅, C₆H₄CH₃, C₃H₅) with protic nucleophiles HX (X = Cl, CF₃COO, CCl₃COO) leads, through a combined protonation/carbon-carbon coupling reaction, to η²-acyl complexes η⁵-C₅H₅(CO)_1−nX₂(PMe₃)_n-M(η²-COCH₂R). The reaction conditions, the results of the spectroscopic measurements and the X-ray structure of η⁵-C₅H₅(CO)(Cl₂)W(η²-COCH₂CH₃) are reported.     

The chemistry of cyclopentadienyl-ruthenacyclopentatrienes: novel carbon monoxide and isocyanide insertion reactions in [η5-C5H5)Ru(η4-C5Ph2H2NBut)Br]

Reaction of the novel ruthenacyclopentatriene [(η⁵-C₅H₅)Ru(C₄Ph₂H₂)Br] (1) with isocyanides gives the imino-2,5-diphenylcyclopentadiene complexes [(η⁵-C₅H₅Ru(η⁴-C₅Ph₂H₂NR)Br] (2, R = Me, Et, Cy, t-Bu, 2,6-Me₂C₆H₃); a novel fluxional process involving phenyl substituent rotation and imino nitrogen inversion has been identified for 2 (R = t-Bu, 2,6-Me₂C₆H₃), the interpretation of which is supported by the X-ray crystal structure determination of 2 (R = t-Bu).     

1,1′-Disubstituierte Titanocen-dithiolen-Chelate des Typs (η5-Me3EC5H4)2Ti(S2C2R2) (E = C,Si, Ge)

1,1′-Disubstituted Titanocene Dithiolene Chelates of Type (η⁵-Me₃EC₅H₄)₂Ti(S₂C₂R₂) (E = C, Si, Ge) Reaction of the titanocene dichlorides (η⁵-Me₃EC₅H₄)₂TiCl₂ (E = C, 1a ; E = Si, 1b ; E = Ge, 1c ) with the 1,2-dithiolates (NaS)₂C₂H₂, (NaS)₂C₂(CN)₂ or (LiS)₂C₆H₃Me-4 gave the new titanocene dithiolene chelates (η⁵-Me₃EC₅H₄)₂Ti(S₂C₂H₂) ( 2a–c ), (η⁵-Me₃EC₅H₄)₂Ti[S₂C₂(CN)₂] ( 3a–c ) and (η⁵-Me₃EC₅H₄)₂Ti(S₂C₆H₃Me-4) ( 4a–c ). These have been characterized by ¹H NMR, IR, and mass spectroscopy, and have been compared with the unsubstituted η⁵-C₅H₅ analogues 2d, 3d and 4d . Activation energies for the chelate ring inversion in solution of 2a–c, 3a–d and 4a–c have been estimated by temperature-dependent ¹H NMR spectroscopy.     

Derivate des borols: VIII. (η5-borol)cobalt-komplexe

A large variety of (η⁵-borole)cobalt complexes have been prepared starting with η-(CO)₂[Co(CO)(η⁵-C₄H₄BR)]₂(CoCo) (IIIa: R = Me, IIIb: R = Ph), including inter alia, the sandwich complexes CpCo(η⁵-C₄H₄BR) (VIIa, b), the triple-decked complexes η-(η⁵-C₄H₄BR)[Co(η⁵-C₄H₄BR)]₂ (VIIIa, b) and μ-(η⁵-C₄H₄BR)(FeCp)[Co(η⁵-C₄H₄BR)] (X, R = Ph), the dinuclear complex μ-(CO)₂[Fe(CO)Cp][Co(CO)(η⁵-C₄H₄BPh)](FeCo) (IX), and salts M[Co(η⁵-C₄H₄BR)₂](XVa, b: M = Na; XVIa, b: M = NMe₄; XVII: M = Cs, R = Ph). The anions [Co(η⁵-C₄H₄BR)₂]⁻ readily undergo stacking reactions to form multiple-decked complexes such as the triple-decker compounds μ-(η⁵-C₄H₄BR)[Mn(CO)₃][Co(η⁵-C₄H₄BR)] (XIIa, b), μ-(η⁵-C₄H₄BR)[Co(η⁵-C₄H₄BR)][Rh(η-1,5-COD)] (XVIII), [NMe₃Ph][μ-η⁵-C₄H₄BPh){Cr(CO)₃}{Co(η⁵-C₄H₄BPh)}] (XX), and the quadruple-decker complex Ru[μ-(η⁵-C₄H₄BR)Co(η⁵-C₄H₄BR)]₂ (XXI). The monofacially bound η⁵-borole ligands in VIIb and VIIIb shows regiospecific H/D exchange, at the α position of the boron, on treatment with CF₃CO₂D at room temperature. VIIb undergoes a Friedel-Crafts substitution to give the 2-acetyl derivative XXIV with MeCoCl/SnCl₄ in CH₂Cl₂ at room temperature.The structure of VIIIa, as determined by X-ray diffraction studies is that of a typical triple-decker compound with nearly coplanar rings. The three borole rings form a helix with torsional angles of 59.8 and 72.2°. All intra-ring bond distances of the central ligand are longer than those of the outer ligands. The metal-ligand interaction is somewhat stronger for the outer ligands than for the central ligand.     

Study of half-sandwich platinum group metal complexes bearing dpt-NH2 ligand

A quite general approach for the preparation of η⁵-and η⁶-cyclichydrocarbon platinum group metal complexes is reported. The dinuclear arene ruthenium complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, C₁₀H₁₄ and C₆Me₆) and η⁵-pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁶-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh, Ir) react with 2 equiv. of 4-amino-3,5-di-pyridyltriazole (dpt-NH₂) in presence of NH₄PF₆ to afford the corresponding mononuclear complexes of the type [(η⁶-arene)Ru(dpt-NH₂)Cl]PF₆ {arene = C₁₀H₁₄ (1), C₆H₆ (2) and C₆Me₆ (3)} and [(η⁶-C₅Me₅)M(dpt-NH₂)Cl]PF₆ {M = Rh (4), Ir (5)}. However, the mononuclear η⁵-cyclopentadienyl analogues such as [(η⁵-C₅H₅)Ru(PPh₃)₂Cl], [(η⁵-C₅H₅)Os(PPh₃)₂Br], [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] and [(η⁵-C₉H₇)Ru(PPh₃)₂Cl] complexes react in presence of 1 equiv. of dpt-NH₂ and 1 equiv. of NH₄PF₆ in methanol yielded mononuclear complexes [(η⁵-C₅H₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (6), [(η⁵-C₅H₅)Os(PPh₃)(dpt-NH₂)]PF₆ (7), [(η⁵-C₅Me₅)Ru(PPh₃)(dpt-NH₂)]PF₆ (8) and [(η⁵-C₉H₇)Ru(PPh₃)(dpt-NH₂)]PF₆ (9), respectively. These compounds have been totally characterized by IR, NMR and mass spectrometry. The molecular structures of 4 and 6 have been established by single crystal X-ray diffraction and some of the representative complexes have also been studied by UV–Vis spectroscopy.     

π-cyclopentadienyls of nickel(II) : XV. Insertion reaction of RNCS into the nickel—carbon bond

η⁵-C₅H₅NiPBu₃CH(CN)₂ (I) readily undergoes ethyl- or phenyl-isothiocyanate insertion, producing the stable products η⁵-C₅H₅NiPBu₃SC(NRH) = C(CN)₂ (IIIa; R = C₂H₅, IIIb; R = C₆H₅. η⁵-C₅H₅NiPPh₃CH(CN)₂ (II) reacts with RNCS (R = C₂H₅ and C₆H₅) to undergo two types of insertion reaction; with C₂H₅NCS, η⁵C₅H₅NiPPh₃SC[N(C₂H₅)H] = C(CN)₂ (IVa) is obtained, with C₆H₅NCS, on the other hand, η⁵-C₅H₅NiPPh₃SC(NC₆H₅)CH(CN)₂ (IVb) is produced. p ]IIIa and IIIb react with PBu₃ to give ionic complexes [η⁵-C₅H₅Ni(PBu₃)₂]⁺ [SC(NC₂H₅H)C(CN)₂]^? (Va) and [η⁵-C₅H₅Ni(PBu₃)₂]⁺ [SC(NC₆H₅)CH(CN)₂]^?(Vb), respectively.