Die Molekül- und Kristallstrukturen von (CO)4 W(μ-S-t-C4H9)2W(CO)4, η7-C7H7W(μ-SC6H4CH3)3W(CO)3 und η7-C7H7W(μ-S-n-C4H9)3W(CO)(μ-S-n-C4H9)2W(CO)4

Molecular and Crystal Structures of (CO)₄W(μ-S-t-C₄H₉)₂W(CO)₄, η⁷-C₇H₇W(μ-SC₆H₄CH₃)₃W(CO)₃ and η⁷-C₇H₇W(μ-S-n-C₄H₉)₃W(CO)(μ-S-n-C₄H₉)₂W(CO)₄ The molecular structures of the two binuclear complexes (CO)₄W(μ-S-t-C₄H₉)₂W(CO)₄ and η⁷-C₇H₇W(μ-SC₆H₄CH₃)₃W(CO)₃ and of the tungsten cluster η⁷-C₇H₇W(μ-S-n-C₄H₉)₃W(CO)-(μ-S-n-C₄H₉)₂W(CO)₄ respectively are described. In the nonlinear trinuclear cluster the central tungsten atom is connected to the two tungsten atoms by two and three μ-S-n-C₄H₉ bridges respectively and additionally by one W? W bond each. The coordination sphere of the W atoms is completed by a η⁷-C₇H₇ ring and four CO groups respectively; the central tungsten carries an additional CO group.     

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.     

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.     

Isomere η2-Acyl- und σ-Alkyl(carbonyl)-Komplexe von Molybdän und Wolfram. Eine Studie zum Bildungs-mechanismus,zur Isomerisierungsgeschwindigkeit und zur Steuerung der Gleichgewichtslage

η²-Acyl and σ-Alkyl(carbonyl) Coordination in Molybdenum and Tungsten Complexes: Synthesis and Studies of the Isomerization Equilibria and Kinetics The anionic molybdenum and tungsten complexes [L_RM(CO)₃]^? (L_R^? = [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, O-i-C₃H₇; M = Mo, W) have been alkylated with the iodides R′ I, R′ = CH₃, C₂H₅, i-C₃H₇, and CH₂C₆H₅. The reactivity pattern of the alkylation is in accord with a S_N2 mechanism. Depending on M, R′, reaction temperature, and time the η-alkyl (carbonyl) compounds [L_RM(CO)₃R′] and/or the isomeric η²-acyl compounds [L_RM(CO)₂(η²-COR′)] can be obtained. 8 new σ-alkyl(carbonyl) compounds and 15 new η²-acyl compounds have been isolated and characterized. The ¹H NMR and the IR spectra give conclusive evidence that the σ-alkyl(carbonyl) compounds [L_RM(CO)₃R′] are formed as the primary products of the alkylation and that they isomerize partly or completely to give the η²-acyl compounds [L_RM(CO)₂(η²-COR′)]. The position of the equilibrium σ-alkyl(carbonyl)/η²-acyl is controlled by the steric demands of the groups R′ and the ligands L_R^?. The molybdenum compounds isomerize much more readily than the tungsten compounds. The rate constants of the isomerization processes [L_RMo(CO)₃CH₃] → [L_RMo(CO)₂(η²-COCH₃)], R = OCH₃, OC₂H₅, and O-i-C₃H₇, measured at 305 K in acetone-d₆, are 6–8 x 10^?3 s^?1.     

Synthesis of the compounds [Re(CR)(CO)2(η5-C9H7)][BF4] (R = C6H4Me-4 or C6H3Me2-2,6) and the preparation of complexes with FeRe bonds

The salts [Re(CR)CO)₂(η⁵-C₉H₇)][BF₄] [R = C₆H₄Me-4 or C₆H₃Me-2,6; η⁵- C₉H₇ = indenyl] have been prepared and used to synthesize the dimetal compounds [FeRe(μ-CR)(μ-NO)(CO)₄(η⁵-C₉H₇)]. The iron-rhenium species containing a bridging p- tolylmethylidyne ligands react with [Fe₂(CO)₉] or with [Ru(CO)₄(η-C₂H₄)], respectively, to yield the trimetal compounds ([FeMRe(μ₃-CC₆H₄Me-4)(μ-CO)(μ-NO)(CO)₆(η ₅-C₉H₇)] (M = Fe or Ru).     

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.     

The coordinative properties of the ligands Ph2ECH2EPh2 (E = P,As, Sb) in carbonylvanadium complexes,and the molecular structure of η5-C5H5V(CO)3As2Ph4

Photo-reaction between the ligands Ph₂ECH₂EPh₂ (E = P: dppm, E = As: dpam, E = Sb: dpsm), L, and the vanadium complexes η⁵-C₅H₅V(CO)₄ and [Et₄N][V(CO)₆] yields monosubstituted mononuclear (dpsm) and dinuclear, ligand-bridged complexes (dpam, dpsm). With dppm, the final products are disubstituted chelate complexes, but monosubstituted mono- and dinuclear species are formed as intermediates.The shielding of the ⁵¹V nucleus decreases in the series dpsm > dppm > dpam and {M(CO)_n} > {M(CO)_n?1} L > {M(CO)_n?1}₂μ-L > {M(CO)_n?2}dppm ({M(CO)_n}[V(CO)₆]^?, η⁵-C₅H₅V(CO)₄). The half-widths of the NMR signals are greater for dinuclear than for mononuclear complexes.The crystal and molecular structures of η⁵-C₅H₅V(CO)₃As₂Ph₄ have been determined. The compound crystallizes in the space group P2₁/c with a = 1347.8, b = 1020.0, c = 2085.2 pm and β = 82.3°. Due to steric crowding, the ⁵¹V shielding is low composed to that of {η⁵-C₅H₅V(CO)₃}₂μ-dpam.     

Reversal of the bonding mode of μ-C7H7 on an FeRh framework: Synthesis and structure of (μ-C7H7)(μ-CO)Fe(CO)2Rh(dppe)

Phosphine ligands rapidly displace one or two carbonyl groups from (μ-C₇H₇)F$\text{e(CO)}{}_3\text{R}$h(CO)₂ (I). The substitution occurs exclusively at the Rh center and proceeds with reversal of the bonding mode of the μ-C₇H₇ moiety from η⁴-Rh and η³-Fe in I to η³-Rh and η⁴-Fe in μ-C₇H₇)(μ-CO)Fe(CO)₂Rh(dppe).     

(η5-C5R5)2Fe2(CO)2(μ-CO)(μ-CH2) (R = H,CH3): A convenient one-pot synthesis using chloromethyl pivalate

The compounds (η⁵-C₅R₅)₂Fe₂(CO)₂(μ-CO)(μ-CH₂) (R = H, CH₃) have been prepared through the reaction of chloromethyl pivalate with the appropriate metal anions, η⁵-C₅H₅Fe(CO)₂K and η⁵-C₅Me₅Fe(CO)₂K.     

Perfluormethyl-Element-Liganden. XXXV. Reaktivität metallierter Phosphane und Arsane des Typs π-C5H5(CO)3MER2 (M  Cr,Mo, W; E  P,As; R  CF3, CN)

Perfluoromethyl-Element-Ligands. XXXV. Reactivity of Metallated Phosphanes and Arsanes of the Type π-C₅H₅(CO)₃MER₂ (M ? Cr, Mo, W; E ? P, As; R ? CF₃, CN) The influence of the complex fragments π-C₅H₅(CO)₃M (M ? Cr, Mo, W) on the basicity of the metallated phosphanes or arsanes π-C₅H₅(CO)₃MER₂ (E ? P, As; R ? CF₃, CN) has been investigated by reactions with sulfur, methyliodide, fluorotrichloromethane, and W(CO)₅THF, respectively. π-C₅H₅(CO)₃ME(CF₃)₂ (E ? P: 1a–c ; E ? As: 2a–c ) react with sulfur only for E ? P to give the complexes π-C₅H₅(CO)₃P(S)(CF₃)₂ ( 5a–c ) in good yield. The attempted thermal transformation of the phosphane sulfides to η² coordinated (CF₃)₂P?S complexes proves unsuccessful. The reactions of 1a–c, 2a–c and π-C₅H₅(CO)₃MP(CN)₂ ( 3a–c ) with CH₃I or CCl₃F do not lead to onium salts, but to cleavage of the M–E bonds forming π-C₅H₅(CO)₃MX (X ? I, Cl) and CH₃ER₂ and R₂ECCl₂F, respectively. The reactivity depends on ER₂ and M: P(CF₃)₂ > P(CN)₂ > As(CF₃)₂; Cr > Mo > W. Due to the low donor ability of the complexes 1a–c, 2a–c and 3a–c binuclear compounds π-C₅H₅(CO)₃MER₂W(CO)₅ (E ? As, R ? CF₃: 11a–c ; E ? P, R ? CN: 12a–c ; ER₂?P(CN)Ph: 13a, b ) are obtained only with the highly reactive W(CO)₅THF. In case of the (CF₃)₂P bridged derivatives spontaneous CO-elimination leads to the threemembered ring systems ( 10a–c ).     

Heterometallische Clusterkomplexe der Typen Re2(μ-PR2)(CO)8(HgY) und ReMo(μ-PR2)(η5-C5H5)(CO)6(HgY) (R = Ph,Cy; Y = Cl,W(η5-C5H5)(CO)3)

Heterometallic Cluster Complexes of the Types Re₂(μ-PR₂)(CO)₈(HgY) and ReMo(μ-PR₂)(η⁵-C₅H₅)(CO)₆(HgY) (R = Ph, Cy; Y = Cl, W(η⁵-C₅H₅)(CO)₃) Dinuclear complexes Re₂(μ-H)(μ-PR₂)(CO)₈ and ReMo(μ-H)(μ-PR₂)(η⁵-C₅H₅)(CO)₆ (R = phenyl, cyclohexyl) were deprotonated and reacted as anions with HgCl₂ to compounds of the both types Re₂(μ-PR₂)(CO)₈HgCl) and ReMo(μ-PR₂)(η⁵-C₅H₅)(CO)₆(HgCl). The heterometallic three-membered cluster complexes correspond to an isolobal exchange of a proton against a cationic HgCl⁺ group. For one of the products ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgCl) has been shown its conversion with NaW(η⁵-C₅H₅)(CO)₃ to ReMo(μ-PCy₂)(η⁵-C₅H₅)(HgW(η⁵-C₅H₅)(CO)₃) under substitution of the chloro ligand, par example. The newly prepared compounds were characterized by means of IR, UV/VIS and ³¹P NMR data. A complete determination of the molecular structure by single crystal analyses was done in the case of Re₂(μ-PCy₂)(CO)₈(HgCl) and of ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgCl) which both are dimer because of the presence of an asymmetric dichloro bridge, and of ReMo(μ-PCy₂)(η⁵-C₅H₅)(CO)₆(HgW(η⁵-C₅H₅)(CO)₃). The structural study illustrates through comparison the influence of various metal types on an interaction between centric and edge-bridged frontier orbitals in three-membered metal rings.     

Reactions of the cycloheptatrienyl complexes [MX(CO)2(η-C7H7)] (M=Mo, X=Br; M=W, X=I) with CNBu: X-ray crystal structure of [WI(CO)2(CNBu)2(η-C7H7)]

Reaction of [MX(CO)₂(η⁷-C₇H₇)] (M=Mo, X=Br; M=W, X=I) with two equivalents of CNBu^t in toluene affords the trihapto-bonded cycloheptatrienyl complexes [MX(CO)₂(CNBu^t)₂(η³-C₇H₇)] (1, M=Mo, X=Br; 2, M=W, X=I). The X-ray crystal structure of 2 reveals a pseudo-octahedral molecular geometry with an asymmetric ligand arrangement at tungsten in which one CNBu^t is located trans to the η³-C₇H₇ ring. Treatment of 2 with tetracyanoethene results in 1,4-cycloaddition at the η³-C₇H₇ ring to give [WI(CO)₂(CNBu^t)₂{η³-C₉H₇(CN)₄}], 3. The principal reaction type of the molybdenum complex 1 is loss of carbonyl and bromide ligands to afford substituted products [MoBr(CNBu^t)₂(η⁷-C₇H₇)] 4 or [Mo(CO)(CNBu^t)₂(η⁷-C₇H₇)]Br. Reaction of [MoBr(CO)₂(η⁷-C₇H₇)] with one equivalent of CNBu^t in toluene at 60°C affords [MoBr(CO)(CNBu^t)(η⁷-C₇H₇)], 5, which is a precursor to [Mo(CO)(CNBu^t)(NCMe)(η⁷-C₇H₇)][BF₄], 6, by reaction with Ag[BF₄] in acetonitrile. In contrast with the parent dicarbonyl systems [MoX(CO)₂(η⁷-C₇H₇)], complexes of the Mo(CO)(CNBu^t)(η⁷-C₇H₇) auxiliary, 5 and 6, do not afford observable η³-C₇H₇ products by ligand addition at the molybdenum centre.     

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.     

Alkylsulfito,bisulfito and sulfito complexes of η5-cyclopentadienyldicarbonyliron(II)

Alkylsulfito complexes η⁵-C₅H₅Fe(CO)₂S(O)₂OR (R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇) have been prepared by reaction of [η⁵-C₅H₅Fe(CO)₂H₂O]BF₄ with Na[S(O)₂OR] (R = CH₃, C₂H₅) and the respective alcohol as solvent. These products may be interconverted by the use of the appropriate alcohol at reflux; such exchange occurs also at 25°C in the presence of HBF₄. Reaction of η⁵-C₅H₅Fe(CO)₂S(O)₂OCH₃ with (+)₅₈₉-2-C₈H₁₇OH and HBF₄ followed by treatment of the optically active product (+)₅₈₉-η⁵-C₅H₅Fe(CO)₂S(O)₂OC₈H₁₇ with CH₃OH and HBF₄ regenerates (+)₅₈₉-2-C₈H₁₇OH with unchanged specific rotation. Hydrolysis of η⁵-C₅H₅Fe(CO)₂S(O)₂OR affords η⁵-C₅H₅Fe(CO)₂S(O)₂OH, which is a strong acid.     

SYNTHESIS OF ORGANOTRANSITION METAL COMPLEXES CONTAINING p-METHOXYCARBONYLBENZOYLCYCLO-PENTADIENYL AND p-METHOXYCARBONYLPHENYL (HYDROXYMETHYL)CYCLOPENTADIENYL LIGANDS FROM SODIUM p-METHOXYCARBONYLBENZOYLCYCLO-PENTADIENIDE. X-RAY STRUCTURE OF η5-p-MeO2CC6H4COC5H4Mo(CO)3I

Abstract

A new functionally substituted cyclopentadienyl salt p-MeO₂CC₆H₄COC₅H₄Na (1) was prepared from cyclopentadienylsodium and dimethyl terephthalate in THF, and which might be utilized to synthesize a series of novel transition metal complexes containing difunctional group-substituted cyclopentadienyl ligands; 1 reacted with M(CO)₆(M = Mo, W) followed by treatment with PBr₃ or I₂ to give mononuclear organomolybdenum (or tungsten) halides η⁵-p-MeO₂CC₆H₄COC₅H₄M(CO)3X(2, M = Mo, X = Br; 3, M = W, X = Br; 4, M = Mo, X = I; 5, M = W, X = I), whereas reaction of 1 with W(CO)₆ and successive treatment with selenium powder and MeI or PhCH₂Cl afforded mononuclear organotungsten selenolate complexes η⁵-p-MeO₂CC₆H₄COC₅H₄W (CO)₃SeMe (6) and η⁵-p-MeO₂CC₆H₄COC₅H₄W(CO)₃SeCH₂Ph (7). In addition, 1 reacted with M(CO)₆(M = Mo, W) followed by treatment with FeCo₂(CO)₉(μ₃-S) to produce the corresponding polynuclear complexes η⁵-p-MeO₂CC₆H₄COC₅H₄MFeCo(CO)₈(μ₃?S) (8, M = Mo; 9, M = W), which could be converted with NaBH₄ into hydroxyl derivatives η⁵-p-MeO₂CC₆H₄CH(OH)C₅H₄MFeCo(CO)₈(μ₃?S) (10, M = Mo; 11, M = W). All the new transition metal complexes 2–11 have been fully characterized by elemental analysis, IR and ¹H NMR spectroscopy, as well as for 4 by an X-ray diffraction analysis.     

Preparation and Characterization of an Unusual Di-Cobalt Complex; X-Ray Crystal Structure of Co(CO)2(μ-CO)(μ:η2,η4-C4Ph4)Co(CO)2(PPh3)

Reaction of [MoCo(CO)₅(PPh₃)₂(η⁵-C₅H₅)] (1) with diphenylacetylene in tetrahydrofuran at 50 °C yielded two heterobimetallic compounds, [MoCo(CO)₄.(PPh₃){μ-PhC ? CPh}(η⁵-C₅H₅)] (4) and [MoCo(CO)₅{μ-PhC ? CPh} (η⁵-C₅H₅)] (5). However, an unexpected product, Co(CO)₂(μ-CO)(μ:η₂,η⁴-C₄Ph₄)Co(CO)₂(PPh₃) (6), was observed while attempting to grow the crystals for structural determination of 4. The X-ray crystal structure of 6 was determined: triclinic, $ {\rm P}\bar 1 $, a = 11.654(2) Å, b = 12.864(2) Å, c = 13.854(2) Å, α = 89.67(2)°, β = 86.00(2)°, γ= 83.33(2)°, V = 2057.9(6) ų Z=2. In 6, two cobalt fragments are at apical and basal positions of the pseudo-pentagonal pyramidal structure, respectively. The electron count for the apical cobalt fragments is 20, which is rather unusual. It is believed that 6 was formed after the fragmentation and recombination of the fragmented species of 4.     

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.     

Binuclear tungstenocene chemistry: hydrido and halo derivatives

The new compounds {(η-C₅H₅WX)[μ-(σ, η-C₅H₄)]}₂, where X = Cl, Br or I are described. The known hydride X = H, protonates and rearranges giving the new cation {(η-C₅H₅)WH}₂, (μ-H)[μ-C₅(η-C₅H₄-η-C₅H₄)]⁺.     

Reductions of metal carbonyls by quaternary ammonium borohydrides

Quaternary ammonium borohydrides, used directly or generated in phase transfer reactions, are highly effective reagents for preparing metal carbonyl anions from metal carbonyls [Mo(CO)₆, Mn₂(CO)₁₀, Re₂(CO)₁₀, CO₂(CO)₈, Fe₃(CO)₁₂, Ru₃(CO)₁₂ and (η⁵-C₅H₅)₂Mo₂(CO)₆] and from some metal carbonyl halides [BrMn(CO)₅ and η⁵-C₅H₅Mo(CO)₃Cl]. Where strongly basic anions would be formed from a halide [BrMn(CO)₄PPh₃ and η⁵-C₅H₅Ru(CO)₂Br], the reactions provide efficient syntheses of the corresponding hydrides instead. The anion η⁵-C₅H₅Fe(CO)₂^? is not accessible by these techniques; reaction of η⁵-C₅H₅Fe(CO)₂Br yields the iron dimer (via the highly nucleophilic anion) and the dimer is unreactive toward Q⁺BH₄^?. Reductions of Re₂(CO)₁₀ conducted in CH₂Cl₂ provide Re₂(CO)₉Cl^? in high yield.