Formation of ferraboranes from pentaborane(9) or BH3 · thf and an electron-rich cyclopentadienyl iron phosphine hydride

[(η⁵-C₅R₅)Fe(PMe₃)₂H] (R = H, Me) can be made in good yields in a simple one-pot reaction between FeCl₂, PMe₃, C₅R₅H (R = H, Me) and Na/Hg in thf. Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with pentaborane(9) gives the known metallaborane [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (1) in improved yield as well as the new metallaboranes [(η-C₅H₅)-nido-2-FeB₅H₈{μ-5,6-Fe(η⁵-C₅H₅)(PMe₃)(μ-6,7-H)}] (2), [(η-C₅H₅)(PMe₃)-arachno-2-FeB₃H₈] (3), [(η⁵-C₅H₅)₂-capped-nido-2,3-Fe₂B₄H₈] (4), [(η⁵-C₅H₅)-nido-2-FeB₄H₇(PMe₃)] (5) and [(η⁵-C₅H₅)-nido-2-FeB₅H₈(PMe₃)] (6). Reaction of [(η⁵-C₅Me₅)Fe(PMe₃)₂H] with pentaborane(9) gives predominantly [(η⁵-C₅Me₅)-nido-2-FeB₅H₁₀] (7) and [(η⁵-C₅Me₅)(PMe₃)-arachno-2-FeB₃H₈] (8). Reaction of [(η⁵-C₅H₅)Fe(PMe₃)₂H] with 2 equiv. of BH₃ · thf gives low yields of ferrocene and compound 3. Compound 7 thermally isomerises to the apical isomer [(η⁵-C₅H₅)-nido-2-FeB₅H₁₀] (9) in low yield. Compounds 1 and 7 deprotonate cleanly in the presence of KH at the unique B-H-B bridge to give [(η⁵-C₅H₅)-nido-2-FeB₅H₉⁻][K⁺] (10) and [(η⁵-C₅Me₅)-nido-2-FeB₅H₉⁻][K⁺] (11) respectively, whilst 6 deprotonates more slowly at one of two equivalent B-H-B bridges to give the fluxional anion [(η⁵-C₅H₅)-nido-2-FeB₅H₇(PMe₃)⁻] (12).     

Reactions of pentaborane(9) with electron-rich molybdenum and tungsten phosphine polyhydrides

Reaction of [W(PMe₂Ph)₃H₆] with pentaborane(9) gives nido-2-[W(PMe₂Ph)₃H₂B₄H₈] (1) as well as nido-2-[W(PMe₂Ph)₃HB₅H₁₀] (2). The crystal structure of (2) has been determined. Compound (2) has a novel metallaborane structure containing an edge-bridging {BH₃} group between the tungsten atom and one of the basal boron atoms in a “nido-WB₄” pyramid. Reaction of [W(PMe₃)₄(η²-CH₂PMe₂)H] with pentaborane(9) gives nido-2-[W(PMe₃)₃H₂B₄H₈] (3) whilst reaction of [Mo(L)₄H₄] with pentaborane(9) gives nido-2-[Mo(L)₃H₂B₄H₈] [L = PMe₃ (4), PMe₂Ph (5)]. Treatment of [Mo(PMe₃)₄H₄] with excess BH₃ · thf gives the known borohydride [Mo(PMe₃)₄H(η²-BH₄)].     

Molybdenum complexes containing substituted cyclopenta[l]phenanthrenyl ligand

The synthesis of new cyclopenta[l]phenanthrenyl complexes [(η⁵-C₁₇H₁₀Me)(η³-C₃H₅)Mo(CO)₂] and [(η⁵-C₁₇H₉(COOMe)N(CH₂)₄)(η³-C₃H₅)Mo(CO)₂] is described. Although these compounds are structural analogues their reactivity is different. Protonation of [(η⁵-C₁₇H₁₀Me)(η³-C₃H₅)Mo(CO)₂] gives a stable ionic compound [(η⁵-C₁₇H₁₀Me)Mo(CO)₂(NCMe)₂][BF₄] while its analogue containing both tertiary amino and carboxylic ester groups [(η⁵-C₁₇H₉(COOMe)N(CH₂)₄)(η³-C₃H₅)Mo(CO)₂] decomposes under the same conditions. [(η⁵-C₁₇H₁₀Me)Mo(CO)₂(NCMe)₂][BF₄] reacts with cyclopentadiene to give a stable η⁴-complex [(η⁴-C₅H₆)(η⁵-C₁₇H₁₀Me)Mo(CO)₂][BF₄] that was successfully oxidized to the Mo(IV) dicationic compound [(η⁵-C₅H₅)(η⁵-C₁₇H₁₀Me)Mo(CO)₂][Br][BF₄].     

Partial incorporation of a cyclopentadienyl ligand into a molybdaborane to form a molybdacarbaborane

Reaction of the molybdaborane arachno-2-[Mo(η-C₅H₅)(η⁵:η¹-C₅H₄)B₄H₇] (I) with NEt₃ in toluene at 120 °C for 7 days gives a 90% yield of the molybdacarbaborane nido-1-[Mo(η-C₅H₅)(η³:η²-C₃H₃)C₂B₃H₅] (II). Two of the carbon atoms in the substituted cyclopentadienyl ring in I are incorporated into the metallacarbaborane cluster II. The carbaborane {C₂B₃H₅} fragment in II is attached to an allylic {C₃H₃} group and can be thought of as a new non-planar {C₅B₃H₈} ligand providing seven electrons to the molybdenum atom. Reaction of I with KH in thf at 20 °C gives the anion via deprotonation of a B-H-B bridging proton.     

New η-allyl η-cyclopentadienylcobalt cations

[Co(R-η-C₃H₄)(η-C₅H₅)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt₃ to the iodo-complex (R  H) gives [Co(η-C₃H₅)(η-C₅H₅)(PEt₃)]⁺. The reactions of [Co(R-η-C₃H₄)(η-C₅H₅))I] (R  H or 2-Me) with AgBF₄ give solutions containing the coordinatively unsaturated species [Co(R-η-C₃H₄)(η-C₅H₅)⁺. The presence of traces of water leads to the formation of [Co(R-ηC₃H₄)-(η-C₅H₅)(H₂O)]⁺. The addition of monodentate ligands L  PEt₃ PPh₃, AsPh₃, SbPh₃, CNCH₃ and bidentate ligands LL  Ph₂PCH₂CH₂PPh₂(dppe) and o-C₆H₄(AsMe₂)₂(diars), gives, respectively mononuclear [Co(2-Me-ηC₃H₄)-(η-C₅H₅)L]⁺ and binuclear ligand-bridged [(2-Me-ηC₃H₄)(η-C₅H₅)CoLLCo(2-Me-ηC₃H₄)(η-C₅H₅))]²⁺ complexes. Crystals of [Co(2-Me-ηC₃H₄)(η-C₅H₅)-(H₂O)]⁺[BF₄]^- are monoclinic, space group P2₁/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H₂O molecule in a staggered conformation with respect to the 2-Me group.     

Structural characterization of the anionic halfsandwich complex [Li(TMEDA)2][Mo(η5-C5H5)(CO)3] and its reactivity towards stannanes and distannanes

The crystal structure of the molybdenum half sandwich alkali salt [Li(TMEDA)₂][Mo(η⁵-C₅H₅)(CO)₃] shows the occurrence of a separated ion pair in the solid state. Furthermore, the crystal structures of the long known organotin complexes [Mo(η⁵-C₅H₅)(SnMe₃)(CO)₃], [{Mo(η⁵-C₅H₅)(CO)₃}₂SnMe₂] and [Mo(η⁵-C₅H₅)(SnMeCl₂)(CO)₃] have been recorded. The chlorination of [Mo(η⁵-C₅H₅)(SnMe₃)(CO)₃] with SnCl₄ is presented as an improved synthetic access to [Mo(η⁵-C₅H₅)(SnMeCl₂)(CO)₃]. Finally, the reaction of Li[Mo(η⁵-C₅H₅)(CO)₃] with ^tBu₂(Cl)Sn–Sn(Cl)^tBu₂ leads to the novel molybdenum distannane complex [Mo(η⁵-C₅H₅){Sn^tBu₂-Sn(Cl)^tBu₂}(CO)₃], which is fully characterized by NMR, elemental and X-ray analysis.     

Mono-η-arenebis(trimethylphosphine(rhenium chemistry: alkyl,hydrido, halogeno and olefin derivatives

Co-condensation of rhenium atoms with a benzene-trimethylphosphine mixture gives the dimer [Re(ν-C₆H₆)(PMe₃)₂]₂ which is a precursor to the new compounds Re(η-C₆H₆)(PMe₃)₂R (R = H, Cl, I, Me, Et, CHCH₂ or Ph), [Re(η-C₆H₆)(PMe₃)₂X₂]BF₄ (X₂ = H₂ or HI), [Re(η-C₆H₆)(PMe₃)₂H₂][BF₄]₂, and [Re(η-C₆H₆)(PMe₃)₂L]BF₄ (L = η-C₂H₄ or CO). Co-condensation of manganese atoms with benzene-trimethylphosphine gives Mn(η-C₆H₆)(PMe₃)₂H.     

Metallaborane reaction chemistry. Part 12. Some interactions of acetylenes and isocyanides with selected metallaboranes

Compared to the chemistry associated with the basic syntheses and structures of the metallaboranes, their reaction chemistry is relatively uninvestigated. To illustrate the potential variety of such reaction chemistry, a linked overview of some previously reported and previously unreported reactions of the nido-6-metalladecaboranes [(PPh₃)₂HIrB₉H₁₃], [(PPh₃)(Ph₂PC₆H₄)HIrB₉H₁₂], [(η⁶-C₆Me₆)RuB₉H₁₃], [(η⁶-MeC₆H₄^isoPr)RuB₉H₁₃] and [(η⁵-C₅Me₅)RhB₉H₁₃] with acetylenes and isocyanides is presented, together with some related chemistry derived from the arachno-type 4-metallanonaboranes [(PMe₂Ph)₂PtB₈H₁₂] and [(PMe₃)₂(CO)HIrB₈H₁₂]. Reductions, oligomerisations, and reductive oligomerisations of the unsaturated species are observed, as well as complete or partial incorporation of carbon and nitrogen hetero atoms into the metallaborane clusters.¹     

Trityl tetraphenylborate as a reagent in organometallic chemistry

Trityl tetraphenylborate, prepared from trityl triflate and sodium tetraphenylborate, is shown to be a useful hydride and methyl anion abstraction reagent for organometallic compounds. It reacts with (η⁵-C₅Me₅)(PMe₃)₂RuMe to give the fulvene complex [η⁴-C₅Me₄CH₂)(PMe₃)₂RuMe]BPh₄, and with (η⁵-C₅H₅)₂ZrMe₂ in acetonitrile-d₃ to afford the cationic methyl derivative [(η⁵-C₅H₅)₂ZrMe(NCCD₃)]BPh₄.     

Syntheses and crystal structures of group 6 metal complexes containing allyl and cyanotrihydroborate groups

Compounds M(η³-C₃H₅)(CO)₂(NCCH₃)₂(NCBH₃) and [N(CH₃)₄]₂[M(η³-C₃H₅)(CO)₂(NCBH₃)₃] (M = Mo, W) were prepared and structurally characterized. In the solid state, the allyl group orients its open face to the two carbonyl groups producing an endo form in the above compounds. In solution, an exo form coexists with an endo form in compound Mo(η³-C₃H₅)(CO)₂(NCCH₃)₂(NCBH₃). The cyanotrihydroborate ligand bonds to the metal through a nitrogen atom. Both of the IR and the 11B NMR spectroscopic data suggest the negative charge of the cyanotrihydroborate ligand on the complex is almost localized on the BH₃ and this negative charge only has small effect on the metal-nitrogen interaction.     

Transition metal derivatives of arenediazonium ions: XIV. Reactions of arenediazomolybdenum(II) complexes with neutral and anionic Lewis bases

The reactions of arenediazomolybdenum(II) complexes such as [(η-C₅H₅)Mo(N₂C₆H₄CH₃-p)I₂]₂, (η-C₅H₅)Mo(CO species with neutral and anionic monodentate or chelating ligands have been investigated. The new arenediazo complexes isolated from these reactions include neutral species such as (η-C₅H₅)Mo(PPh₃)(N₂C₆H₄CH₃-p)I₂ and (η-C₅H₅)Mo(N₂C₆H₄CH₃-p) cations of the type [η-C₅H₅)Mo(bipy)(N₂C₆H₄CH₃-p)I]⁺ and the anion [(η-C₅H₅)Mo(N₂C₆H₄CH₃-p)I₃]^?. The structures of the new complexes are discussed.     

The stereoselective reaction of sodium cyanide with the cationic ruthenium vinylidene complex [(η5-C5H5)(PMe3)2RuCC(Me)Ph]+

The reaction of sodium cyanide with [(η⁵-C₅H₅)(PMe₃)₂RuCC(Me)Ph]PF₆ (1) proceeds with high stereoselectivity (> 95 : 5) to give (Z)-(η⁵-C₅H₅)(PMe₃)₂RuC(CN)C(Me)Ph, which under acid conditions isomerises (< 5 : 95) to the E isomer.     

Charge relocation in cationic diene complexes: formation of an iminium-substituted allyl complex and its deprotonation to an enamine

The reaction of [Mo(NCME)₂(CO)₂(η⁵-C₉H₇)][BF₄] (1) with 1-dimethylaminocyclohexa-1,3-diene affords the cationic η³-allyl complex [Mo(η³-C₆H₇NMe₂)(CO)₂- (η⁵-C₉H₇)][BF₄] (3), in which the positive charge is located at an exocyclic iminium centre. Addition of Li[N(SiMe₃)₂] to 3 results in deprotonation and the formation of an enamine species [Mo(η³-C₆H₆NMe₂)(CO)₂(η⁵-C₉H₇)] (8), which undergoes stereofacial attack upon treatment with electrophiles.     

Complexes du titane et du zirconium contenant les ligands cyclopentadienyldiphenylphosphine et cyclopentadienylethyldiphenylphosphine: acces a des structures heterobimetalliques

Reactions of Ph₂P(CH₂)_n(C₅H₄)Li, (n = 0, 2), with MCl₄ or CpTiCl₃ (M = Ti, Zr; Cp = η⁵-C₅H₅) form Cl₂M[(η⁵-C₅H₄)(CH₂)_nPPh₂]₂ or Cl₂CpTi[(η⁵-C₅H₄)-(CH₂)₂PPh₂] in good yields. Chemical reduction with Al, or electrochemical reduction of these complexes, under CO, are described. The titanium(IV) and zirconium(IV) derivatives react with metal carbonyls (Mo(CO)₆, Cr(CO)₆, Fe(CO)₅, Mo(CO)₄(C₈H₁₂)) under formation of new heterobimetallic complexes. Reduction with Al of Cl₂CpTi[(η⁵-C₅H₄)(CH₂)₂PPh₂]Mo(CO)₅ under CO results in a new heterobimetallic species containing low valent titanium. Both complexes Cl₂M[(η⁵-C₅H₄)(CH₂)₂PPh₂]₂ (M = Ti, Zr) react with [Rh(μ-Cl)(CO)(C₂H₄)]₂ to yield {RhCl(CO)(Cl₂M[(η⁵-C₅H₄)(CH₂)₂PPh₂]₂)}x, which is assumed to be a dimer, in which the titanium or the zirconium compounds act as bridging diphosphine ligands between the rhodium atoms.     

Reactions of small boranes with ruthenium phosphine hydrides: Oligomerisation of monoborane-tetrahydrofuran to a nido-hexaruthenaborane

Reaction of [Ru(PPh₃)₄H₂] with BH₃ · thf at room temperature gives borane oligomerisation with the formation of the 6-vertex metallaborane nido-2-[Ru(PPh₃)₂(H)B₅H₁₀] (1). This cluster is also formed by reaction of [Ru(PPh₃)₄H₂] with nido-B₅H₉. Compound (1) is readily deprotonated by KH in thf at the unique basal B-H-B bridge to give (2). In contrast to [Ru(PPh₃)₄H₂] reaction of [cis-Ru(PMe₃)₄H₂] with BH₃ · thf gives initially the known borohydride [Ru(PMe₃)₃(H)(η²-BH₄)] which reacts with excess BH₃ · thf to give the 5-vertex metallaborane nido-2-[Ru(PMe₃)₃B₄H₈] (3). Reaction of [cis-Ru(PMe₃)₄H₂] with nido-B₅H₉ also gives (3) and nido-2-[Ru(PMe₃)₃B₉H₁₃] (4). [cis-Ru(PMe₃)₄H₂] is conveniently prepared in high yield in a one-pot synthesis by the sodium amalgam reduction of RuCl₃ · 3H₂O in thf with excess PMe₃ under dinitrogen.     

Preparation of new (η5-C5H4CH3)Mn(NO)(PPh3) and (η7-C7H7)Mo(CO)-(PPh3) complexes

The complex (η⁵-C₅H₄CH₃)Mn(NO)(PPh₃)I has been prepared by the reaction of NaI with [(η⁵-C₅H₄CH₃)Mn(NO)(CO)(PPh₃)]⁺ and also by the reaction of [(η⁵-C₅H₄CH₃)Mn(NO)(CO)₂]⁺ with NaI followed by PPh₃. This iodide compound reacts with NaCN to yield (η⁵-C₅H₄CH₃)Mn(NO)(PPh₃)CN which is ethylated by [(C₂H₅)₃O]BF₄ to yield [(η⁵-C₅H₄CH₃)Mn(NO)(PPh₃)(CNC₂H₅)]⁺. Both [(η⁵-C₅H₄CH₃)Mn(NO)(CO)₂]⁺ and [(η⁵-C₅H₄CH₃)Mn(NO)(PPh₃)(CO)]⁺ react with NaCN to yield [(η⁵-C₅H₄CH₃)Mn(NO)(CN)₂]^?. This anion reacts with Ph₃SnCl to yield cis-(η⁵-C₅H₄CH₃)Mn(NO)(CN)₂SnPh₃ and with [(C₂-H₅)₃O]BF₄ to yield [(η⁵-C₅H₄CH₃)Mn(NO)(CNC₂H₅)₂]⁺. The reaction of (η⁵-C₅-H₄CH₃)Mn(NO)(PPh₃)I with AgBF₄ in acetonitrile yields [(η⁵-C₅H₄CH₃)Mn-(NO)(PPh₃)(NCCH₃)]⁺. The complex (η⁵-C₅H₄CH₃)Mn(NO)(CO)I, produced in the reaction of [(η⁵-C₅H₄CH₃)Mn(NO)(CO)₂]⁺ with NaI, is not stable and decomposes to the dimeric complex (η⁵-C₅H₄CH₃)₂Mn₂(NO)₃I for which a reasonable structure is proposed. Similar dimers can be prepared from the other halide salts. The reaction of (η⁷-C₇H₇)Mo(CO)(PPh₃)I with NaCN yields (η⁷-C₇-H₇)Mo(CO)(PPh₃)CN which is ethylated by [(C₂H₅)₃O]BF₄ to yield [(η⁷-C₇H₇)-Mo(CO)(PPh₃)(CNC₂H₅)]⁺. The interaction of this molybdenum halide complex with AgBF₄ in acetonitrile and pyridine yields [(η⁷-C₇H₇)Mo(CO)(PPh₃)-(NCCH₃)]⁺ and [(η⁷-C₇H₇)Mo(CO)(PPh₃)(NC₅H₅)]⁺, respectively. Both (η⁵-C₅-H₄CH₃)Mn(NO)(PPh₃)I and (η⁷-C₇H₇)Mo(CO)(PPh₃)I are oxidized by NOPF₆ to the respective 17-electron cations in acetonitrile at ?78°C but revert to the neutral halide complex at room temperature. This result is supported by electrochemical data.     

Organometallic polymorphism. Synthesis and structural characterization of two forms of [Ru(η6-C6H6)(η6-C6H4(CH3)COOCH3)][BF4]2 and the phase transition in [Ru(η5-C5H5)(η6-C6H5OH)][PF6]

The synthesis and structural characterization of the complex [Ru(η⁶-C₆H₆)(η⁶-C₆H₄(CH₃)COOCH₃)] [BF₄]₂ (2) and of its precursor [Ru(η⁶-C₆H₄(CH₃)COOCH₃)Cl₂]₂ (1) are reported. Compound (2) has been characterized in two polymorphic modifications (2a and 2b) and the molecular organization in the solid state has been investigated. The complex [Ru(η⁵-C₅H₅)(η⁶-C₆H₅OH)][PF₆] (3) has also been investigated; it has been shown to possess a disorder similar to that observed in the high temperature phase of related systems such as [Ru(η⁵-C₅H₅)(η⁶-C₆H₆)][PF₆].     

Derivatives of M(η5-C5H5)2 (M = Mo,W) with alkenylpyridines and related ligands

Reactions of ligands 2-vinylpyridine 1, 4-vinylpyridine 2, 2-allylpyridine 3, 1-allylpyrazole 4, acrylonitrile 5 and allylcyanide 6 with the metallocene derivatives [Mo(η⁵-C₅H₅)₂H₃][PF₆] 7, [Mo(η⁵-C₅H₅)₂HI] 8, [W(η⁵-C₅H₅)₂H₃] [PF₆] 9, [Mo(η⁵-C₅H₅)₂H₂] 10, [M(η⁵-C₅H₅)₂Br₂], M = Mo 11, M = W 12 are described. Reaction of 7 with 1, 8 with 1, 3 with 8 and 4 with 8 gave mixtures of metallocyle isomers resulting from coordination of the nitrogen atom to molybdenum followed by internal hydrometallation; reaction of 11 with 1 gave an olefinic π complex; reaction of either 9 or 11 with 1 gave intractable oils; reactions of 8 with 2, 11 with 5, 12 with 5, 11 with 6 and 12 with 6 yielded monosubstituted products in which the ligand is N-coordinated.     

Anionic tolylmethylidyne(carbaborane)tungsten complexes: protonationa and reaction with trimethylphosphine

Protonation of the closely related salts [N(PPh₃)₂][W(CC₆H₄Me-4)(CO)₂(η-1,2-C₂B₉H₉R₂] (Ia, R = H; Ib, R = Me) affords structurally different products: [N(PPh₃)₂][W₂(μ-H){μ-C₂(C₆H₄Me-4)₂}(CO)₄(η-1,2-C₂B₉H₁₁)₂] (III) and [W(CC₆H₄Me-4)(CO)₂(η-1,2-C₂B₉H₁₀Me₂)] (V), respectively. Treatment of Ib, with PMe₃, gives the ketenyl complex [N(PPh₃)₂][W(CO)(PMe₃){η²-C(C₆H₄Me-4)C(O)}(η-1,2-C₂B₉H₉Me₂)] (VI). Protonation and methylation of the latter yields the alkyne-tungsten compounds [W(CO)(PMe₃){η-C₂(OR′)(C₆H₄Me-4)}(η-1,2-C₂B₉H₉Me₂)] (IXa, R′ = H; IXb, R′ = Me).     

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.