[Fec3(μ3-CR)(CO)10]− Cluster anions as building blocks for the synthesis of mixed-metal clusters: II. Synthesis of HFe3Rh(μ4-η2-CCHR)(CO)11 clusters (R = H or C6H5) and study of their catalytic activity (R = C6H5) under hydroformylation and hydrogenation conditions

The mixed-metal vinylidene clusters HFe₃Rh(CO)₁₁(CCHR) (R = H, C₆H₅) have been synthesized via the reaction of [HFe₃(CO)₃CCHR][P(C₆H₅)₄] with [RhCl(CO)₂]₂ in the presence of a thallium salt. The reaction initially gives the [Fe₃Rh(CO)₁₁]CCHR][P(C₆H₅)₄] cluster which leads to the final products by protonation. Spectroscopic data indicate a μ₄-η² mode of bonding for the vinylidene ligand. A structure with a Fe₃Rh core in a butterfly configuration and in which the rhodium atom occupy a wing-tip site is proposed. The catalytic activity of HFe₃Rh(CO)₁₁(CCH(C₆H₅)) (80% yield) has been checked in hydroformylation and hydrogenation. In hydroformylation the cluster shows the same activity as Rh₄(CO)₁₂, whereas in hydrogenation the mixed-metal system shows specific activity; isomerization of 1-heptene to cis and trans 2-heptene takes place with no more than 14% heptane formation. The cluster is broken down during the catalysis, and some H₃Fe₃CO)₉(μ₃-CCH₂(C₆H₅)) is formed. The latter cluster is not an active catalyst, and under the same conditions use of Rh₄(CO)₁₂ results mainly in hydrogenation of 1-heptene. These observations suggest that the active species is a mixed iron-rhodium system.     

Iron atom discrimination by carbon during the fragmentation of a ligand around a FeFe bond. Crystal structure [μ-η3-RCH2OC(S)SMeFe2(CO)5P(OMe)3]

The substituted compound [μ-η³RCH₂OC(S)SMeFe₂(CO)₅P(OMe)₃] (3) (the structure of which was determined by X-ray diffraction), undergoes a ligand fragmentation leading to the known substituted compound [μ-η²(RCH₂OCS)Fe₂- (CO)₅P(OMe)₃μ-SMe] (4). Evidently during the rearrangement the carbon atom of the bridging ligand migrates from one iron atom to the adjacent iron that bears the phosphite ligand.     

Übergangsmetall-substituierte Acylphosphane und Phosphaalkene. 17 [1] Synthese und Struktur der μ-Isophosphaalkin-Komplexe [(η5-C5H5)2(CO)2Fe2(μ-CO)(μ-CPC6H2R3-2,4,6)] (R = Me,iPr, tBu)

Transition Metal Substituted Acylphosphanes and Phosphaalkenes. 17. Synthesis and Structure of the μ-Isophosphaalkyne Complexes [(η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(μ-C?PC₆H₂R₃)] (R = Me, iPr, tBu) . Condensation of (η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(μ-CSMe)}⁺SO₃CF₃^? ( 6 ) with 2,4,6-R₃C₆H₂PH(SiMe₃) ( 7 ) ( a : R = Me, b : R = iPr, c : R = tBu) affords the complexes (η⁵-C₅H₅)₂(CO)₂Fe₂(μ-CO)(η-C?PC₆H₂R₃-2,4,6) ( 9 a–c ) with edge-bridging isophosphaalkyne ligands as confirmed by the x-ray structure analysis of 9 a .     

Intramolecular rearrangement of the bridging σ,π-acetylide ligand in the Os3H(CO)9(L)(μ-η2-CCPh) (L = CO,PMe2Ph) clusters and crystal structure of Os3H(CO)9(PMe2Ph)(μ-η2-CCPh)

Clusters Os₃H(Cl)(CO)₉(L) (L= CO, PMe₂Ph) react with lithium phenyl-acetylide to yield Os₃H(CO)₉(L)(μ-η²-CCPh),which has a bridging acetylide ligand. The Os₃H(CO)₁₀(μ-η²-CCPh) complex (II) is fluxional owing to rapid π → σ, σ → π interchange of acetylide ligand between the bridged osmium atoms, whereas the phosphine-substituted derivative, Os₃H(CO)₉(PM₂Ph)(μ-η²-CCPh) (III), is stereochemically rigid and exists at room temperature in two isomeric forms. These isomers have been isolated as solids and have been characterized by ¹H and ³¹P{¹H} NMR spectroscopy. According to the spectroscopic data, in the major (IIIa) and minor (IIIb) isomers the phosphine ligand is coordinated to the metal atom which is σ- or π-bonded to the bridging acetylide group, respectively. The isomerization of IIIb into IIIa occurs only at 80°C. The structure of IIIa has been confirmed by an X-ray diffraction study.     

The reaction of ortho-halogenated aromatic aldazine ligands with Fe2(CO)9: symmetrical cleavage of the azine and carbon-halogen activation

Azine ligands derived from hydrazine and benzaldehyde derivatives bearing halogen substituents in ortho-position with respect to the carbonyl function upon treatment with Fe₂(CO)₉ show two typical reaction principles. One is the symmetrical cleavage of the N-N bond of the azine to yield either di- or trinuclear iron carbonyl compounds [Fe₂(CO)₆(μ₂-NCHR)₂] and [Fe₃(CO)₉(μ₂-NCHR)(μ₂-η²-NCHR)] each showing two arylidenimido moieties. In addition, a trinuclear iron carbonyl cluster compound exhibiting a tetrahedral Fe₃N cluster core is isolated. The cluster shows only one half of the former azine ligand. It is a ionic compound of the general formula [Fe₃(CO)₉(μ₃-η²-NCHR)]Na × H₂O. This trinuclear cluster compound is quantitatively converted into [Fe₃(CO)₉(μ₂-H)(μ₃-η²-NCHR)] upon treatment with phosphorous acid. Most interestingly, we were also able to isolate two types of compounds in which an activation of one of the carbon halogen bonds in ortho-position with respect to the imine functions of the azine has occured in terms of an ortho-metallation reaction. In the N-N bond of the azine is still preserved, whereas in [Fe₃(CO)₉(μ₃-η³-NCHR)] again only one half of the former azine ligand is coordinated in an arylidenimido fashion. In both types of compounds one additional iron carbon bond is present due to the activation of an aromatic carbon halogen bond. The reaction of iron carbonyls with 2,6-difluorobenzonitrile produces [Fe₃(CO)₉(μ₃-η²-NCR)] as the sole product. All new iron carbonyl compounds are characterized by means of X-ray crystallography.     

The Diphenylacetylene Reaction with Tricarbonylbis(η2-cis-cyclooctene)iron in the Presence or Absence of Carbon Monoxide

Known to be a facile irontricarbonyl transfer reagent, (η²-cis-C₈H₁₄)₂Fe(CO)₃ 1 transfers its Fe(CO)₃ unit to a variety of ligands at low temperature. Stirring a THF mixture of 1 and PhC=CPh under N₂(g) at ?60 °C for 1 h then at room temperature overnight provides mainly a flyover-bridge product [-CPh=CPhC(0)-CPh=CPh-]Fe₂(CO)₆ 2 with the organic bridge on diiron core in a complicated μ-(1,2,5-η³:1,4,5-η³) fashion. The keto fragment in 2 comes presumably from the decomposition of 1 that liberates CO. However, stirring a THF mixture of 1 and PhC=CPh under CO(g) at ?60 °C for 3 h then at room temperature overnight results in [-C(0)CPh=CPhC(0)-]Fe(CO)₄ 3, a compound not isolated in the earlier thermal or photochemical reactions of PhC=CPh with ironcarbonyl. The X-ray structure determinations for both 2 and 3 have been performed.     

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).     

Reactivity of [HFe3(CO)11]−1 toward alkynes: II. Reactions with monosubstituted alkynes: from alkylidyne to acetylide ligands on a triiron unit

The reactions of monosubstituted alkynes (RCCH (R = C₆H₅, C₃H₇, C(O)CH₃ or C(O)OCH₃) with [P(C₆H₅)₄][HFe₃(CO)₁₁] have been studied. Depending on the reaction conditions the complexes [P(C₆H₅)₄][Fe₃(CO)₁₀(μ₃-CCH₂R)] (A) and [P(C₆H₅)₄][HFe₃(CO)₉(μ₃-CCHR)] (B) can be isolated. The two types of complexes are interrelated by the addition of (B → A) or loss (A → B) of carbon monoxide. In two cases (R = C₆H₅, C₃H₇) the transformation B → [P(C₆H₅)₄][Fe₃(CO)₉(μ₃-CCR)] has been observed in refluxing 2-methoxyethanol, and for these two alkynes all the transformations

have been observed on a triiron unit.     

Darstellung carboxylatsubstituierter Rhenium-Gold-Metallatetrahedrane Re2(AuPPh3)2(μ-PCy2)(CO)7(η1-OC(R)O) (R = H,Me, CF3, Ph, 3,4-(OMe)2C6H3)

Synthesis of Carboxylate Substituted Rhenium Gold Metallatetrahedranes Re₂(AuPPh₃)₂(μ-PCy₂)(CO)₇(η¹-OC(R)O) (R = H, Me, CF₃, Ph, 3,4-(OMe)₂C₆H₃) The reaction of the in situ prepared salt Li[Re₂(μ-H)(μ-PCy₂)(CO)₇(ax-C(Ph)O)] ( 2 ) with 1,5 equivalents of monocarboxylic acid RCOOH (R = H ( 4 a ), Me ( 4 b ), CF₃ ( 4 c ), Ph ( 4 d ), 3,4-(OMe)₂C₆H₃ ( 4 e ) in tetrahydrofruan (THF) solution at 60 °C gives within 4 h under release of benzaldehyde (PhCHO) the η¹-carboxylate substituted dirhenium salt Li[Re₂(μ-H)(μ-PCy₂)(CO)₇(η¹-OC(R)O)] (R = H ( 4 a ), Me ( 4 b ), CF₃ ( 4 c ), Ph ( 4 d ), 3,4-(OMe)₂C₆H₃ ( 4 e )) in almost quantitative yield. The lower the pK_a value of the respective carboxylic acid the faster the reaction proceeds. It was only in the case of CF₃COOH possible to prove the formation of the hydroxycarbene complex Re₂(μ-H)(μ-PCy₂)(CO)₇(=C(Ph)OH) ( 5 ) prior to elimination of PhCHO. The new compounds 4 a–4 e were only characterized by ³¹P NMR and ν(CO) IR spectroscopy as they are only stable in solution. They are converted with two equivalents of BF₄AuPPh₃ at 0 °C in a so-called cluster expansion reaction into the heterometallic metallatetrahedrane complexes Re₂(AuPPh₃)₂(μ-PCy₂)(CO)₇(η¹-OC(R)O) (R = H ( 7 a ), Me ( 7 b ), CF₃ ( 7 c ), Ph ( 7 d ), 3,4-(OMe)₂C₆H₃ ( 7 e )) (yield 47–71% ). The expected precursor complexes of 7 a–7 e Li[Re₂(AuPPh₃)(μ-PCy₂)(CO)₇(η¹-OC(R)O] ( 8 ) were not detected by NMR and IR spectroscopy in the course of the reaction. Their existence was retrosynthetically proved by the reaction of 7 b with an excess of the chelating base TBD (1,5,7-Triazabicyclo[4.4.0]dec-5-en) forming [(TBD)_xAuPPh₃][Re₂(AuPPh₃)(μ-PCy₂)(CO)₇(η¹-OC(Me)O] ( 8 b ) in solution. The η¹-bound carboxylate ligand in 7 a–7 e can photochemically be converted into a μ-bound ligand in Re₂(AuPPh₃)₂(μ-PCy₂)(μ-OC(R)O)(CO)₆ (R = H ( 9 a ), Me ( 9 b ), CF₃ ( 9 c ), Ph ( 9 d ), 3.4-(MeO)₂C₆H₃ ( 9 e )) under release of one equivalent CO. All isolated cluster complexes were characterized and identified by the following analytical methods: elementary analysis, NMR (¹H, ³¹P) spectroscopy, ν(CO) IR spectroscopy and in the case of 7 d and 9 b by X-ray structure 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.     

Derivative des borols: VI. Dehydrierende komplexierung von borolenen mit carbonylmetallen: (borol)metall-komplexe von mangan,eisen und cobalt

The reaction of 2-borolenes and 3-borolenes C₄H₆BR (R = Ph, Me, C₆H₁₁, OMe) with Mn, Fe, and Co carbonyls leads to dehydrogenating complexation with formation of simple, i.e. C-unsubstituted (η⁵-borole)metal complexes. Thus, Mn₂(CO)₁₀ gives the triple-decked complexes (μ-η⁵-C₄H₄BR)[Mn(CO)₃]₂ (R = Ph, OMe). By irradiation of Fe(CO)₅ the half-sandwich complexes Fe(CO)₃ (η⁵-C₄H₄BR) (R = Ph, Me, C₆H₁₁, OMe) are formed, whereas Co₂(CO)₈ yields the dinuclear complexes (μ-CO)₂[Co(CO)(η⁵-C₄H₄BR)]₂ (Co-Co) (R = Ph, Me). A low-temperature X-ray structure determination of Fe(CO)₃(η⁵-C₄H₄BPh) is described in detail.     

Chalcogen–acetylide interaction and unusual reactivity of coordinated acetylide with water: synthesis and characterisation of [(η5-C5R5)Fe3(CO)6(μ3-E)(μ3-ECCH2RI)] (R=H,Me; RI=Ph,Fc; E=S,Se) and [(η5-C5R5)MoFe2(CO)6(μ3-S)(μ-SCCH2Ph)] (R=H,Me)

Photolysis of a benzene solution containing [Fe₃(CO)₉(μ₃-E)₂] (E=S, Se), [(η⁵-C₅R₅)Fe(CO)₂(CCR^I)] (R=H, Me; R^I=Ph, Fc), H₂O and Et₃N results in formation of new metal clusters [(η⁵-C₅R₅)Fe₃(CO)₆(μ₃-E)(μ₃-ECCH₂R^I)] (R=H, R^I=Ph, E=S 1 or Se 2; R=Me, R^I=Ph, E=S 3 or Se 4; R=H, R^I=Fc, E=S 5; R=Me, R^I=Fc, E=S 6 or Se 7). Reaction of [Fe₃(CO)₉(μ₃-S)₂]with [(η⁵-C₅R₅)Mo(CO)₃(CCPh)] (R=H, Me), under same conditions, produces mixed-metal clusters [(η⁵-C₅R₅)MoFe₂(CO)₆(μ₃-S)(μ-SCCH₂Ph)] (R=H 8; R=Me 9). Compounds 1–9 have been characterised by IR and ¹H and ¹³C-NMR spectroscopy. Structures of 1, 5 and 9 have been established crystallographically. A common feature in all these products is the formation of new C-chalcogen bond to give rise to a (ECCH₂R^I) ligand.     

Trinuclear Phosphaferroles from Alkylidyne‐Phosphaalkyne Coupling Reactions

Reaction of bisalkylidyne cluster compounds [Fe₃(CO)₉(μ₃‐CR)₂] ( 1a—d ) ( a , R = H; b , R = F; c , R = Cl; d , R = Br) with the phosphaalkyne t‐C₄H₉‐C≡P ( 2 ) yield a single isomer of the phosphaferrole cluster [Fe₃(CO)₈][CR‐C(t‐Bu)‐P‐CR] ( 3a—d ). However, the three isomeric compounds [Fe₃(CO)₈][C(OEt)‐C(t‐Bu)‐P‐C(Me)] ( 5a ), [Fe₃(CO)₈][C(Me)‐C(t‐Bu)‐P‐C(OEt)] ( 5b ), and [Fe₃(CO)₈][C(OEt)‐C(Me)‐C(t‐Bu)‐P] ( 5c ) are obtained in the reaction of [Fe₃(CO)₉(μ₃‐CMe)(μ₃‐C‐OEt)] ( 4 ) with 2 . As the phosphaferroles 3 possess a lone pair of electrons at the phosphorus atom they can act as ligands. [Fe₃(CO)₈][CF‐C(t‐Bu)‐P‐CF]ML_n ( 7a—c ) ( a , ML_n = Cr(CO)₅; b , ML_n = CpMn(CO)₂; c , ML_n = Cp^*Mn(CO)₂) were formed from 3b and L_nM(η²‐C₈H₁₄) ( 6a—c ). The dinuclear cluster [Fe₂(CO)₆][CF‐CF‐C(t‐Bu)‐PH(OMe)] ( 8 ) was obtained from 3b and NiCl₂·6H₂O in methanol. The structures of 3a—d , 5a—c , 7b , and 8 have been elucidated by X‐ray crystal structure determinations.     

Lewis-base properties of the HFe3(CO)9S− and Fe3(CO)9S2− cluster anions

Summary The HFe₃(CO)₉S^– and Fe₃(CO)₉S^2– anions [prepared from H₂Fe₃(CO)₉S by deprotonation] react with M(CO)₅(THF) (M=Cr or W) to form the anionic capped clusters, HFe₃(CO)₉SM(CO) ₅ ^– and Fe₃(CO)₉SM(CO) ₅ ^2– , which can be isolated as their Et₄N salts. The M-S bonds of these complexes are cleaved by ligands such as PPh₃ or MeCN. The dianionic clusters are more stable than their monoanionic analogues. Alkylation of Fe₃(CO)₉S^2– with alkyl halides followed by protonation yields HFe₃(CO)₉SR complexes, among them the first member of the series with R=Me.     

IR frequencies and intensities of the vibrational modes of Cx Hy fragments bonded to metal complexes. Relationship with structure,bonding and reactivity

The following organometallic complexes were studied as models of the coordination between metal atoms and different C_x H_y ligands: Co₂Fe(CO)₉(CCH₂), Co₂Ru(CO)₉(CCH₂), Os₃(H)₂(CO)₉(CCH₂) and Co₂Fe(CO)₉(CC(H)CH₃) (η₃-η₂-vinylidene or μ₃-η₂-methylvinylidene group); Fe₂(C₅H₅)₂(CO)₃(CCH₂) (μ₂-η¹-vinylidene group); Os₃(μ-H)(CO)₉(CHCH₂) (μ₂-η²-vinyl group); CH₃Mn(CO)₅ (η¹-methyl group); Os₃(μ-H)₂(Co)₁₀(CH₂) and Fe₂(CO)₈(CH₂) (μ₂-η¹-methylene group); Co₃(CO)₉(CH) (μ₃-methyne group); CO₃(CO)₉(CCH₃) (μ₃-η¹-ethylidyne group); Os₃(H)(CO)₉(C₂H) (μ₃-η²-acetylide group). The infrared frequencies and intensities associated with the main vibrational modes of the ligands (CC and CH stretchings, CH deformations) were evaluated and compared with those of appropriate model molecules. Both the frequency and intensity data can be usefully correlated with structural parameters (e.g. CC and CH bond distances and HCH bond angles) and provide information on the charge distribution on the ligands. It is therefore possible to discuss the type of metal—ligand interaction and the balance between the σ and π contributions to the bond.     

Transformationen von clustern mit dem (μ3-RP)Fe3(CO)9-Gerüst. Synthese und reaktionen von [(μ3-RP)Fe3(CO)9]2−

The clusters (μ₃-RP)Fe₃(CO)₁₀ (1) or (μ₃-RP)Fe₃(CO)₉(μ₂-H)₂ (2) can reversibly be transformed into the cluster anions [(μ₃-RP)Fe₃(CO)₉ (μ₂-H)]⁻ (3) and [(μ₃-RP)Fe₃(CO)₉]²⁻ (4). The pyrophoric clusters 4 react with the divalent electrophile CH₂I₂ to give the complexes (μ₃-η²-RP=CH₂)Fe₃(CO)₁₀ (5), which contain a cluster-stabilized phosphaalkene, RP=CH₂, as a ligand. With monovalent electrophiles R′X, such as Me₂SO₄, compound 4 (R = anisyl), yields, upon protolytic work-up, the complexes (μ₃-η³-R′P-anisyl)Fe₃(CO)₉(μ₂-H) (6) in which the phosphorus-bound aryl residue of the μ₂-bridging phosphide ligand (R′P-anisyl) forms an η²-coordination to the third iron atom of the cluster. The η²-coordination of the aryl substituent may be reversibly released by two-electron ligands L under formation of (μ₂-R′P-anisyl)(μ₂-H)Fe₃(CO)₉L (7). In addition, the transformation sequence of 5 into 6 is accomplished by an H⁻, H⁺ addition sequence. The experiments are documented by analytic and spectroscopic data as well as by X-ray analyses.     

Some reactions of Ni-Mo and Ni-W propargylic cations with nucleophiles

Preliminary reactions of the metal stabilized carbocationic species [(η-C₅H₅)Ni(μ-η²(Ni),η³(Mo)-HC₂CMe₂)Mo(CO)₂(η-C₅H₄Me)]⁺ BF₄⁻ (Ni-Mo) with nucleophiles are reported. The Ni-Mo cationic propargylic complex undergoes nucleophilic attack by sodium methoxide to regenerate the neutral μ-alkyne complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(OMe)}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo), from which the stabilized carbocation was originally derived by protonation. The new complexes [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(C₅H₅)}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo), which exist as an inseparable mixture of 1(c)-1,3- and 2(c)-1,3-cyclopentadienyl isomers, were also obtained. When the Ni-Mo cations were treated with potassium t-butoxide, the alkyne isomers with pendant 1(c)-1,3- and 2(c)-1,3-cyclopentadienyl groups are also formed. The μ-hydroxyalkyne complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(OH)}-Mo(CO)(η-C₅H₄Me)] (Ni-Mo) was also isolated concurrently, and presumably arises from nucleophilic attack of fortuitously present hydroxide ions in the BuO⁻ reagent on the Ni-Mo cation. When NaBH₄ was added to the Ni-Mo propargylic, nucleophilic attack by hydride resulted and the μ-ⁱPrC₂H heterobimetallic complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂Prⁱ}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo) was recovered in good yield. Small quantities of other side-products were isolated and characterized spectroscopically. Some tantalizing differences in reactivity were observed when the corresponding Ni-W stabilized carbocation was reacted with methoxide ions. When the not fully characterized solid formed by protonating [(η-C₅H₅)Ni(μ-η²,η²-{HC₂CMe₂)(OMe)}W(CO)₂(η-C₅H₄Me)] (Ni-W) was treated with methoxide ions, regioisomers (1(c)-1,3- and 2(c)-1,3-cyclopentadienyl species) of composition [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(C₅H₅)}W(CO)₂(η-C₅H₄Me)] (Ni-W) were formed. Direct reaction of the pure cation [(η-C₅H₅Niμ-η²,η³-HC₂CMe₂)W(CO)₂(η-C₅H₄Me)]⁺ (Ni-W) with methoxide also generated the same 1(c)-1,3- and 2(c)-1,3-cyclopentadiene-substituted alkyne complexes. Unlike the case with the Ni-Mo complexes, the initial μ-HC₂CMe₂(OMe) species was not regenerated.     

Synthesis of [Ru4(μ3-η2-CO)(CO)9{μ-(RO)2PN(Et)P(OR)2}2] (R = Me or Pri): Butterfly clusters of ruthenium containing a triply bridging carbonyl ligand with an unusual mode of coordination. Crystal structure of [Ru4(μ3-η2-CO)(CO)9{μ-(MeO)2PN(Et)P(OMe)2}2]

Reaction of [Ru₃(CO)₁₂] with a two molar proportion of (RO)₂PN(Et)P(OR)₂ (R = Me or Prⁱ) in benzene under reflux affords a number of products including [Ru₃(CO)₁₀{μ-(RO)₂PN(Et)P(OR)₂}], [Ru₃(CO)₉{μ-(RO)₂PN(Et)P(OR)₂}{η¹-(RO)₂PN(Et)P(OR)₂}] and, as the major species, the tetranuclear derivative [Ru₄(μ₃-η²-CO)(CO)₉{μ-(RO)₂PN(Et)P(OR)₂}₂]. An X-ray diffraction study of [Ru₄(μ₃-η²-CO)(CO)₉{μ-(MeO)₂PN(Et)P(OMe)₂}₂] has revealed that the skeletal framework adopts a butterfly structure and that one of the carbonyl groups functions as a triply bridging four-electron donor ligand capping the two wing-tip and one of the hinge ruthenium atoms.     

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.     

Photochemical reactions of 1-ferrocenyl-4-phenyl-1,3-butadiyne with Fe(CO)5 and CO

Photolysis of a hexane solution containing ironpentacarbonyl, 1-ferrocenyl-4-phenyl-1,3-butadiyne at low temperature yields six new products: [Fe(CO)₂{η²:η²-PhCCCC(Fc)C(CCPh)C(Fc)Fe(CO)₃}-μ-CO] (1), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-PhCCCC(Fc)-C(O)-C(Fc)CCCPh}] (2), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCC(CC Ph)-C(O)-C(Fc)CCCPh}] (3), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCCCC(Fc)-C(O)-C(Fc)CCCPh}] (4), [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (5) and [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (6) formed by coupling of acetylenic moieties with CO insertion on metal carbonyl support. In presence of CO, formation of another new product 2,5-bis(ferrocenyl)-3,6-bis(tetracarbonylphenylmaleoyliron)quinone (7) was observed which on further reaction with ferrocenylacetyene gave the quinone, 2,5-bis(ferrocenyl)-3,6-bis(ethynylphenyl)quinone (8). Structures of 1-5 and 8 were established crystallographically.