Molybdenum alkyl- and aryl-thiolates

The reaction between [(η⁵-C₅H₅)MoH(CO)₃] and disulphides gives dimeric or trimeric complexes depending upon the conditions. The syntheses of the novel trinuclear molybdenum carbonyl complex [{Mo(η⁵-C₅H₅)(SR)(μ-CO)(CO)}₃] (R = Me), and dinuclear compounds [Mo₂(η⁵-C₅H₅)(μ-SR)₃(CO)₄] (R = Me) and [Mo₂(η⁵-C₅H₅)₂(SR)₂(CO)₂(μ-SR)(μ-Br)] (R = Me or Ph) are reported.     

Conversion of allene into μ-dimethylcarbene at a diruthenium centre

Treatment of [Ru₂(CO)(μ-CO) {μ-C(O)C₂Ph₂} (η-C ₅H₅)₂] with allene in toluene at 100°C displaces diphenylacetylene and produces [Ru(CO)(η-C₅H₅)-{η³-C₃H₄Ru(CO)₂(η-C₅H₅)}]; upon protonation a 1-methylvinyl cation [Ru₂(CO)₂(μ-CO){μ-C(Me)CH₂}(η-C₅H₅)₂]⁺ is formed which undergoes nucleophillic attack by hydride to yield the μ-dimethylcarbene complex [Ru₂(CO)₂-(μ-CO)(μ-CMe₂)(η-C₅H₅)₂].     

A convenient entry into diruthenium chemistry

In boiling toluene, diphenylacetylene is readily displaced from the dimetallocycle [Ru₂(CO)(μ-CO) {μ-C(O)C₂Ph₂} (η-C₅H₅)₂] by a variety of reagents (P(OMe)₃, SO₂, R₂CN₂, Ph₂PCH₂) to produce [Ru₂(CO){P(OMe)₃}(μ-CO)₂ - (η-C₅H₅)₂] or [Ru₂(CO)₂(μ-CO)(μ-L)(η-C₅H₅)₂] (L  SO₂, CR₂, CH₂) in high yield.     

Reactivity of the unsaturated dimolybdenum anion [Mo2(η-C5H5)2(μ-PCy2)(μ-CO)2] towards electrophiles based on p- and d-block elements

The 30-electron binuclear anion [Mo₂Cp₂(μ-PCy₂)(μ-CO)₂]⁻ reacts with the chlorophosphite ClP(OEt)₂ or the organotin chlorides Cl₂SnPh₂ or ClSnPh₃ to give compounds of the formula trans-[Mo₂Cp₂(μ-E)(μ-PCy₂)(CO)₂], (E = P(OEt)₂, SnPh₃, SnPh₂Cl). In contrast, this anion reacts with the organosilicon chlorides ClSiR₃ (R = Ph, Me) to give unstable silyloxycarbyne-bridged complexes [Mo₂Cp₂(μ-PCy₂)(μ-COSiR₃)(μ-CO)], which rapidly hydrolyze to give the known hydride [Mo₂Cp₂(μ-H)(μ-PCy₂)(CO)₂]. Two main types of products were also observed in the reactions of the title anion with different chlorocomplexes of the transition and post-transition metals. Thus, the reactions with [MCl₂Cp₂] (M = Ti, Zr) give moisture-sensitive isocarbonyl-bridged complexes of the type [Mo₂Cp₂(μ-COMClCp₂)(μ-PCy₂)(μ-CO)]. In contrast, softer metallic electrophiles such as [AuCl(PR₃)] (R = ⁱPr, ptol) react with the anion at the dimolybdenum site to form new trimetallic clusters of the formula [AuMo₂Cp₂(μ-PCy₂)(CO)₂(PR₃)], also retaining a Mo−Mo triple bond. Subsequent reactions of the latter products with the solvate complexes [Au(PR₃)(THF)][PF₆] give the tetranuclear clusters [Au₂Mo₂Cp₂(μ-PCy₂)(CO)₂(PR₃)₂][PF₆] (Mo−Mo = 2.5674(3) Å and Au−Au = 2.7832(2) Å when R = ⁱPr). Finally, the reaction of the title anion with HgI₂ gives the pentanuclear cluster [Hg{Mo₂Cp₂(μ-PCy₂)(CO)₂}₂] or the trinuclear cluster [Mo₂Cp₂(μ-HgI)(μ-PCy₂)(CO)₂] depending on the stoichiometry being actually used for the reaction. The trinuclear species is only stable in tetrahydrofuran (THF), and decomposes to give a mixture of the dimeric species [Mo₂Cp₂(μ-HgI)(μ-PCy₂)(CO)₂]₂ along with variable amounts of the known iodide-bridged complex [Mo₂Cp₂(μ-I)(μ-PCy₂)(CO)₂].     

Synthesis of Dinuclear Mo−Fe Hydride Complexes and Catalytic Silylation of N2

Two transition-metal atoms bridged by hydrides may represent a useful structural motif for N₂ activation by molecular complexes and the enzyme active site. In this study, dinuclear Mo^IV-Fe^II complexes with bridging hydrides, Cp^RMo(PMe₃)(H)(μ-H)₃FeCp* ( 2 a ; Cp^R=Cp*=C₅Me₅, 2 b ; Cp^R=C₅Me₄H), were synthesized via deprotonation of Cp^RMo(PMe₃)H₅ ( 1 a ; Cp^R=Cp*, 1 b ; Cp^R=C₅Me₄H) by Cp*FeN(SiMe₃)₂, and they were characterized by spectroscopy and crystallography. These Mo−Fe complexes reveal the shortest Mo−Fe distances ever reported (2.4005(3) Å for 2 a and 2.3952(3) Å for 2 b ), and the Mo−Fe interactions were analyzed by computational studies. Removal of the terminal Mo−H hydride in 2 a – 2 b by [Ph₃C]⁺ in THF led to the formation of cationic THF adducts [Cp^RMo(PMe₃)(THF)(μ-H)₃FeCp*]⁺ ( 3 a ; Cp^R=Cp*, 3 b ; Cp^R=C₅Me₄H). Further reaction of 3 a with LiPPh₂ gave rise to a phosphido-bridged complex Cp*Mo(PMe₃)(μ-H)(μ-PPh₂)FeCp* ( 4 ). A series of Mo−Fe complexes were subjected to catalytic silylation of N₂ in the presence of Na and Me₃SiCl, furnishing up to 129±20 equiv of N(SiMe₃)₃ per molecule of 2 b . Mechanism of the catalytic cycle was analyzed by DFT calculations.     

Reaction of [M(CO)4] (M = Ir, Rh) with cyclopropenyl tetrafluoroborate - Ring opening and coupling of cyclopropenyl ligands to form dinuclear metal complexes

Reaction of the iridium tetracarbonylate [PPN][Ir(CO)₄] (1a) with triphenylcyclopropenyl tetrafluoroborate [C₃Ph₃][BF₄] afforded two dinuclear species Ir₂(CO)₄(μ,η¹:η²-C₃Ph₃)(μ,η²:η³-C₃Ph₃) (2) and Ir₂(CO)₄(μ,η⁴:η⁴-C₆Ph₆) (3a) resulting from the ring opening and in the latter case, coupling of the resulting acyclic, propenyl ligands. The analogous reaction with [PPN][Rh(CO)₄] (1b) afforded only the rhodium analogue for 3a.     

Reactivity of the 30-electron dimolybdenum anion [Mo2(η-C5H5)2(μ-PCy2)(μ-CO)2] towards β,γ-unsaturated organic halides: Alkenyl, allenyl and alkoxycarbyne derivatives

The 30-electron dimolybdenum anion [Mo₂Cp₂(μ-PCy₂)(μ-CO)₂]⁻ reacts at room temperature with allyl chloride to give the unsaturated σ:π-bonded alkenyl derivative trans-[Mo₂Cp₂(μ-η¹:η²-CMeCH₂)(μ-PCy₂)(CO)₂], this requiring a 2,1-hydrogen shift in the allyl moiety probably induced by the unsaturated nature of the dimetal center. In a similar way, the dimolybdenum anion reacts with trans-1-chloro-2-butene (crotyl chloride) to give a mixture of the alkenyl complexes trans-[Mo₂Cp₂(μ-η¹:η²-CEtCH₂)(μ-PCy₂)(CO)₂] and trans-[Mo₂Cp₂(μ-η¹:η²-CMeCHMe)(μ-PCy₂)(CO)₂] in a 3:2 ratio, which could not be separated by column chromatography. All these alkenyl species exhibit a dynamic behavior in solution (fast on the NMR timescale even at low temperatures) involving alternative π-bonding of the alkenyl ligand to each metal center. In contrast, the title anion reacts with propargyl chloride (ClCH₂-CCH) without further rearrangement of the propargyl moiety, to afford the allenyl derivative trans-[Mo₂Cp₂{μ-η²:η³-CH₂CCH)}(μ-PCy₂)(CO)₂] as the major species. Acryloyl chloride (ClC(O)-CHCH₂) also reacts with the title anion to give a mixture of two products, the carbyne complex [Mo₂Cp₂{μ-COC(O)CHCH₂}(μ-PCy₂)(μ-CO)] and the vinyl trans-[Mo₂Cp₂(μ-η¹:η²-CHCH₂)(μ-PCy₂)(CO)₂], in a 1:1 ratio. This reaction is a unique case in which a single electrophile can attack both nucleophilic positions in the dimolybdenum anion, these being located at the O(carbonyl) and metal sites, respectively. The formation of the vinyl derivative requires the decarbonylation of a metal-bound acryloyl group, which proved to be an irreversible reaction, since the addition of CO to the above alkenyl complex gave instead the tricarbonyl vinyl derivative cis-[Mo₂Cp₂(μ-η¹:η²-CHCH₂)(μ-PCy₂)(CO)₃]. The structure of this electron-precise complex was confirmed through a single-crystal X-ray diffraction analysis (Mo−Mo = 3.0858(7) Å).     

Isonitrilsynthesen am komplex: V. Desulfurierung von isothiocyanaten in carbonylmetallat-additions-verbindungen

The isocyanide complexes [Fe(η-C₅H₅)(CO)₂CNR][PF₆] and Cr(CO)₅CNR (R = CH₃, C₆H₁₁, C₆H₅) are conveniently prepared at ?50°C from carbonyl metallates, isothiocyanates, and phosgene. At room temperature Na[Fe(η-C₅H₅)(CO)₂] reacts with isothiocyanates ($\text{1}\text{1}$) to give the isocyanide bridged complexes [Fe₂(η-C₅H₅)₂(μ-CO)(μ-CNR)(CO)₂].     

Preparation of bis(aryldiazene) and new aryldiazenido complexes of rhenium

Mixed-ligand hydride ReH₂(NO)L(PPh₃)₂ complexes [L=P(OEt)₃ or PPh(OEt)₂] were prepared by allowing the ReH₂(NO)(PPh₃)₃ species to react with an excess of phosphite. Treatment of ReH₂(NO)L(PPh₃)₂ hydrides with an equimolar amount of aryldiazonium cations ArN₂⁺ gives the mono-aryldiazene [ReH(ArNNH)(NO)L(PPh₃)₂]BPh₄ complexes (Ar=C₆H₅, 4-CH₃C₆H₄), while treatment with an excess of ArN₂⁺ yields bis(aryldiazene) [Re(ArNNH)₂(NO)L(PPh₃)₂](BPh₄)₂ derivatives. Binuclear [{ReH(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₂ and [{Re(4-CH₃C₆H₄NNH)(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₄ complexes (ArAr=4,4′-C₆H₄C₆H₄, 4,4′-C₆H₄CH₂C₆H₄) were also prepared. The reaction of the triphenylphosphine ReH₂(NO)(PPh₃)₃ complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene [ReH(ArNNH)(NO)(PPh₃)₃]BPh₄ and [{ReH(NO)(PPh₃)₃}₂(μ-HNNArArNNH)](BPh₄)₂ derivatives. The complexes were characterised spectroscopically (IR, NMR) using the ¹⁵N-labelled derivatives. The aryldiazenido [ReH(C₆H₅N₂){PPh(OEt)₂}₄]BPh₄ complex was prepared by allowing trihydride ReH₃[PPh(OEt)₂]₄ to react with phenyldiazonium tetrafluoroborate. A reaction path involving the aryldiazene [ReH₂(C₆H₅NNH){PPh(OEt)₂}₄]⁺ intermediate was also proposed.     

Electrophilic additions to unsaturated systems : By P.B.D. De la Mare and R. Bolton,Elsevier Scientific Publ. Co., Amsterdam and New York, 2nd Edition, 1982, xiii + 377 pages,U.S. $91.50, Dutch Fl. 215.00

The metalmetal double-bonded μ-alkyne complex [Ru₂(μ-CO)(μ-C₂Ph₂) (η-C₅H₅)₂] (1) reacts with diazomethane at 0°C to yield Ru₂(CO)(η-CH₂) {μ-C(Ph)C(Ph)CH₂} (η-C₅H₅)₂] (2) incorporating two methylene units, one bridging the metal atoms and one linked with the alkyne. Upon heating, a second carboncarbon bond formation occurs to link the methylene groups and give [Ru₂(CO)(μ-CO) {μ-C(Ph)C(Ph)C(H)Me} (η-C₅H₅)₂ (3); the structures of 1 and 2 were established by X-Ray diffraction.     

Irregular cyclization reactions in titanocenes bearing pendant double bonds

Reduction of methyl-substituted titanocene dichlorides bearing pendant double bonds [TiCl₂{η⁵-C₅Me₄(CH₂CMeCH₂)}₂] (1) and [TiCl₂{η⁵-C₅Me₄(SiMe₂(CH₂)₂CHCH₂)}₂] (2) with magnesium yielded diamagnetic Ti(IV) compound [Ti{η¹:η¹:η⁵-C₅Me₃(CH₂)(CH₂CH(Me)CH₂)}{η⁵-C₅Me₄(CH₂C(Me)CH₂)}] (4) and paramagnetic Ti(III) compound [Ti{η⁵-C₅Me₄(SiMe₂CH₂CHCHMe)}(μ-η³,η¹:η⁵,η¹(Ti:Mg){C₅Me₃(CH₂)(SiMe₂CHCHCMe)})Mg(OC₄H₈)₂] (6), respectively. The reluctance of titanocene intermediates to undergo intramolecular cyclization to cyclopentadienyl-ring-tethered titanacycles (as typically observed) can be explained by a shortness of the 2-methylallyl group and steric hindrance of its double bond in the former case and, in the latter case, by an attack of magnesium on the titanocene intermediate, faster than cyclization reactions. The crystal structures of 4 and 6 were determined by single-crystal X-ray diffraction.     

Preparation and crystal structure of [μ-Ni(C5H5)P(C6H5)3] [μ-C5H5] [ZnC5H5]2, a nickel-bridged cyclopentadienylzinc dimer

[μ-Ni(C₅H₅)P(C₆H₅)₃] [μ-C₅H₅]₂ [ZnC₅H₅]₂ has been obtained from the reaction of Cp₂Zn with Ni(COD)₂ in the presence of Ph₃P and its structure determined by X-ray crystallography. It consists of two cyclopentadienylzinc moieties bridged by the Ni atom of a CpNiPPh₃ group and by a Cp group. A possible mechanism for the formation of the compound is discussed.     

Reactions of metal carbonyl derivatives : XIV. Bridged phosphido derivatives of iron and ruthenium

The tertiary phosphines P(C₆H₅)₂R [RM π-C₅H₅)(CO)₂ M(π-C₅H₅(CO)₂ (M = Fe or Ru)] readily effect the displacement of the chloro group in [M′(φ-C₅H₅)(CO)₂Cl] (M′ = Fe or Ru) to give bridged cationic species of the type [MM′(φ-C₅H₅)₂(CO)₄P(C₆H₅)]⁺. Treatment of [Fe₂(CO)₉] with P(C₆H₅)₂R [RRu(φ-C₅H₅)(CO)₂] leads to the formation of the neutral mixed-metal derivatives [FeRu(φ-C₅H₅)(CO)₆P(C₆H₅)₂] and [FeRu(φ-C₅H₅)(CO)₅P(C₆H₅)₂].     

[CpR(OC)Mo(μ‐η2:2‐P2)2FeCpR′] als Edukt für heterobimetallische Zweikerncluster mit P2‐ und CnRnP4‐n‐Liganden (n = 1, 2)

[Cp^R(OC)Mo(μ‐η^2:2‐P₂)₂FeCp^R′] as Educt for Heterobimetallic Dinuclear Clusters with P₂ and C_nR_nP_4‐n Ligands (n = 1, 2) The cothermolysis of [Cp^R(OC)Mo(μ‐η^2:2‐P₂)₂FeCp^R′] ( 1 ) and tBuC≡P ( 2 ) as well as PhC≡CPh ( 3 ) affords the heterobimetallic triple‐decker like dinuclear clusters [(Cp'''Mo)(Cp*′Fe)(P₃CtBu)(P₂)] ( 4 ), Cp''' = C₅H₂tBu₃‐1,2,4, Cp*′ = C₅Me₄Et, and [(Cp*Mo)(Cp*Fe)(P₂C₂Ph₂)(P₂)] ( 5 ) with a bridging tri‐ and diphosphabutadiendiyl ligand. 4 and 5 have been characterized additionally by X‐ray crystallography.     

Solvent induced ionisation of η-allydicarbonylmolybdenum(II) complexes

[MoCl(η-C₃H₅)(CO)₂(MeCN)₂] dissolved in aprotic solvents is extensively ionised to [Mo(η-C₃H₅)(CO)₂(MeCN)₃]⁺[Mo₂Cl₃(η-C₃H₅)₂(CO)₄]^- with the liberation of free acetonitrile. The corresponding bromo- complex shows similar but less pronounced ionisation in (CD₃)₂CO, whereas the iodo-complex retains its molecular structure.     

Isocyanide insertion reactivity of dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [{Nb(η-C5H4SiMe3)(CH2Ph)2}2(μ-1,4-NC6H4N)]

The reactivity of dinuclear niobium and tantalum imido complexes with the isocyanide compound 2,6-Me₂C₆H₃NC has been studied. The trialkyl complexes [{NbR₃(CH₃CN)}₂(μ-1,3-NC₆H₄N)], [{NbR₃(CH₃CN)}₂(μ-1,4-NC₆H₄N)] and [{TaR₃(CH₃CN)}₂(μ-1,4-NC₆H₄N)] (R=CH₂SiMe₃) gave [{Nb(η²-RCNAr)₂R}₂(μ-1,3-NC₆H₄N)] (1), [{Nb(η²-RCNAr)₂R}₂(μ-1,4-NC₆H₄N)] (2) and [{Ta(η²-RCNAr)₂R}₂(μ-1,4-NC₆H₄N)] (3) (R=CH₂SiMe₃; Ar=2,6-Me₂C₆H₃), from the isocyanide insertion in two of the metal alkyl carbon bonds. The reaction of the isocyanide reagent with the di-alkyl mono-cyclopentadienyl derivatives [{Nb(η⁵-C₅H₄SiMe₃)R₂}₂(μ-1,3-NC₆H₄N)] (R=Me, CH₂Ph, CH₂SiMe₃), [{Nb(η⁵-C₅H₄SiMe₃)R₂}₂(μ-1,4-NC₆H₄N)] (R=Me, CH₂Ph (4), CH₂SiMe₃) and [{Ta(η⁵-C₅Me₅)(CH₂SiMe₃)₂}₂(μ-1,4-NC₆H₄N)] yielded [{Nb(η⁵-C₅H₄SiMe₃)(η²-RCNAr)R}₂(μ-1,3-NC₆H₄N)] (R=Me (5), CH₂Ph (6), CH₂SiMe₃ (7)), [{Nb(η⁵-C₅H₄SiMe₃)(η²-RCNAr)R}₂(μ-1,4-NC₆H₄N)] (R=Me (8), CH₂Ph (9), CH₂SiMe₃ (10)) and [{Ta(η⁵-C₅Me₅)(η²-Me₃SiCH₂CNAr)CH₂SiMe₃}₂(μ-1,4-NC₆H₄N)] (11) (Ar=2,6-Me₂C₆H₃), respectively, from a single insertion process. The reaction with the mono-alkyl complex [{Nb(η⁵-C₅H₄SiMe₃)(Me)Cl}₂(μ-1,4-NC₆H₄N)] gave [{Nb(η⁵-C₅H₄SiMe₃)(η²-MeCNAr)Cl}₂(μ-1,4-NC₆H₄N)] (12), produced from the isocyanide insertion in the metal-alkyl carbon bond. The alkyl-amido complex [{Nb(η⁵-C₅H₄SiMe₃)(Me)NMe₂}₂(μ-1,4-NC₆H₄N)] gave, from the preferential isocyanide insertion in the metal-amide nitrogen bond, [{Nb(η⁵-C₅H₄SiMe₃)(η²-Me₂NCNAr)Me}₂(μ-1,4-NC₆H₄N)] (13). The molecular structure of one of the alkyl precursors, [{Nb(η⁵-C₅H₄SiMe₃)(CH₂Ph)₂}₂(μ-1,4-NC₆H₄N)] (4), has been determined.     

Sequential conversion of ethyne into μ-vinylidene, μ-methylcarbyne and μ-methylcarbene at a di-ruthenium centre: X-ray structures of [Ru2(CO)2(μ-CO) (μ-CCH2) (η-C5H5)2] and [Ru2(CO)2(μ-CO) (μ-CCH3) (η-C5H5)2] [BF4]

The ethyne-derived demetallocycle [Ru₂(CO) (μ-CO){μ-C(O)C₂H₂}(η-C₅H₅)₂ isomerises in boiling toluene to yield the μ-vinylidene complex [Ru₂(CO)₂(μ-CO)(μ-CCH₂) (η-C₅H₅)₂], which on protonation with dry HBF₄ provides the μ-carbyne complex [Ru₂(CO)₂(μ-CO)(μ-CCH₃)(η-C₅H₅)₂][BF₄]; the structure of each product has been determined by X-ray diffraction. The μ-carbyne cation is attacked by hydride to produce the μ-methylcarbene complex [Ru₂(CO)₂(μ-CO)(μ-CHCH₃)(η-C₅H₅)₂].     

Trinuclear π-cyclopentadienyl bridging sulphido derivatives of iron

The reaction of [Fe(π-C₅H₅)(CO)₂]₂ with the dialkyl disulphides R₂S₂ (R = CH₃, C₂H₅, t-C₄H₉ or CH₂C₆H₅) affords, as well as dinuclear derivatives of the type [Fe(π-C₅H₅)(CO)SR]₂, trinuclear species of formula [Fe₃(π-C₅H₅)₃(CO)₂(S)SR].     

Ansa-metallocenes with B---N and B---P linkages: the importance of N---HF---C hydrogen bonding in pentafluorophenyl boron compounds

The reaction of Cp′(Cp^B)ZrCl₂ [Cp^B=η⁵-C₅H₄B(C₆F₅)₂] with LiNHCMe₃ gave Cp′(Cp^B)(μ-NHCMe₃)ZrCl, with a constrained-geometry type Cp---B---N chelate ligand. The ¹⁹F-NMR spectrum of the zirconium complexes, as well as that of the titanium analogue, reveals C---FH---N hydrogen bonding to one of the ortho-F atoms of a C₆F₅ ring, strong enough to persist in solution at room temperature. The reaction of Cp′(Cp^B)TiCl₂ with LiPPh₂ affords the Cp---B---P chelate complex Cp′(Cp^B)(μ-PPh₂)TiCl, the first example of a crystallographically characterised Ti(IV) phosphido compound. A ¹⁹F-NMR study of a number of adducts of B(C₆F₅)₃ with prim- and sec-amines demonstrates the importance of intramolecular hydrogen bonding to C₆F₅ in this class of compounds, while there are no such interactions in B(C₆F₅)₃(PHR₂) (R=Cy, Ph). The crystal structures of Cp′(Cp^B)(μ-PPh₂)TiCl, B(C₆F₅)₃(NHMe₂) and B(C₆F₅)₃(PHCy₂) are reported.