M. Valle

The chemistry of dodecacarbonyltriruthenium I. Acetylene derivatives of dodecacarbonyltriruthenium

Abstract Substitutions of carbonyl groups in Ru 3 (CO) 12 by diphenylacetylene and tetraphenylcyclopentadienone are described. Nine compounds, six of which are trinuclear ruthenium carbonyl acetylenes, were isolated from the reaction with diphenylacetylene in inert solvents. In methyl alcohol two Ru 3 (CO) 8 (C 2 Ph 2 ) 2 isomers were obtained, a violet one having only terminal carbonyls and an orange-yellow one with bridging carbonyl groups. The thermal decomposition of the products and replacements of carbonyl groups with basic ligands (mainly triphenylphosphine) were studied. A compound Ru 3 (CO) 5 (C 2 Ph2) 2 (PPh 3 ) 3 , containing bridging carbonyl groups, is also described. The greater tendency of the ruthenium carbonyl than of iron carbonyl to retain the trinuclear cluster in these reactions is discussed, with emphasis on the fact that the ruthenium carbonyl can give rise to bridged carbonyl compounds even when such groups are not present in the original structure.

Simple, high-yields syntheses of nickel-osmium clusters. spectroscopic characterization of the new (η-C5H5)NiOs3(CO)9(μ2-H)3. The reactivity of (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3Ni3Os3(CO)9 towards H2, CO, alkynes and alkenes

Abstract The complexes (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3 Ni3Os3(CO)9 can be obtained in high yield by treating Os3(CO)12 or H2Os3(CO)10 with [(η-C5H5)-Ni(CO)]2 in refluxing hydrocarbons. The course of the reactions and the yields of the products can be modified by carrying out the reaction under nitrogen, hydrogen or carbon monoxide atmospheres. A preliminary report of an X-ray study of the hexametallic, 87 e− cluster was presented. The new tetrametallic derivative was characterized by spectroscopic techniques; a tetrahedral, tri-hydridic structure is proposed for this complex. The reactions of the heterometallic nickel-osmium complexes towards ligands, in particular alkenes and alkynes, are discussed. A preliminary investigation of homogeneous hydrogenation of these substrates is reported.

Butadienic derivatives and metal carbonyls II. Some rearrangements of butadienic ligands in reactions with dodecacarbonyltriruthenium

Abstract Isomerization and rearrangement of ligands L, such as 1,4-trans,trans-diphenyl-1,3-butadiene, hexadiene isomers, isoprene and 1,3-butadiene, occur in the reactions with Ru3(CO)12 to give trimetallic complexes of molecular formula HRu3(O)9(L-H), in addition to bi- and monometallic complexes of known structure. On the contrary the diene skeleton is always maintained when L is 2,3-dimethyl-1,3-butadiene. Structures of HRu3(CO)9(L-H) complexes are suggested and some novel features in their proton n.m.r. spectra are described.

Isomerisation of pentenes with H4Ru4(CO)12

Abstract Catalytic isomerisation of 1-pentene to 2- cis and 2- trans -pentene with H 4 Ru 4 (CO) 12 in toluene at 70.4 °C is described. Carbon monoxide, hydrogen, weak acids and polar substances, such as ethyl acetate, decrease the isomerisation rate. Reactions of H 4 Ru 4 (CO) 12 with trans -C 2 H 2 D 2 and [1,2-D 2 ] 1-pentene and of D 4 Ru 4 (CO) 12 with 1-pentene suggest the operation of a metal-hydride addition-elimination mechanism involving σ-alkyl intermediates. The active species is supposed to be mainly originated by loss of CO to give H 4 Ru 4 (CO) 11 . Catalytic hydrogenation of the pentene isomers occurs at the approaching of the equilibrium and is largerly enhanced by addition of hydrogen to the reaction system.

13C NMR study of methynyltricobalt enneacarbonyls

Abstract The 13 C NMR apical carbon resonances for a series of Co 3 (CO) 9 CY complexes have been observed to be in the lowfiedl region (310–230 ppm). Variable temperature spectra have shown “thermal decoupling” of carbon from cobalt and scrambling of the carbonyls.

Effect of phosphorus-donor ligands on the isomerisation of pentenes catalysed by substituted derivatives of H4Ru4(CO)12

Abstract The catalytic activity of H 4 Ru 4 (CO) 11 L (where is PPh 3 , P(OEt) 3 , P(OPh) 3 ), H 4 Ru 4 (CO) 10 [P(OEt) 3 ] 2 and H 4 Ru 4 (CO) 8 [P(OEt) 3 ] 4 in the isomerisation of pentenes in toluene at 70.4 °C is described. The initial conversion rate is proportional to the catalyst concentration, decreases with increasing CO pressure, while the addition of the free ligand causes a decrease of the conversion rate, in the initial steps, ascribed to its preferential coordination on the active sites. For H 4 Ru 4 (CO) 11 L, the isomerisation rate decreases with L in the sequence P(OEt) 3 > (P(OPh) 3 > PPh 3 > CO. The conversion rate, moreover, decreases with n in the series H 4 Ru 4 (CO) 12−n [P(OEt) 3 ] n (n = 1, 2, 4). The results are interpreted by suggesting that the RuCO bonds are mainly involved in the active site formation and that the phosphorus-donor ligands cause a weak increase of the activity of the carbonyl groups. However, the free sites formed by RuCO bond cleavage of Ru(CO) 2 L units are considered to give a little contribution to the isomerisation for the steric hindrance of L.

Hydrogenation of pentynes catalyzed by substituted derivatives of H4Ru4(CO)12 with phosphorus-donor ligands

The catalytic hydrogenation under mild conditions of 1-pentyne and 2-pentyne in the presence of phosphine and phosphite substituted derivatives of H4Ru4(CO)12 has been investigated. The initial rates of hydrogenation of both 1- and 2-pentyne with the monosubstituted derivatives were found to follow the trend: P(OPh)3 ≅ P(OEt)3 < PPh3 ≅ P(n-Bu)3. The initial rates of hydrogenation of 2-pentyne decrease with increasing substitution of the catalyst, while the opposite trend is observed for 1-pentyne. The specificity of all the catalysts investigated, towards the formation of cis-2-pentene and 1-pentene from 2-pentyne and 1-pentyne respectively, is similar and is improved as compared with that observed in the presence of H4Ru4(CO)12. The experimental results are interpreted on the basis of the stability of the alkyne carbonylmetal intermediates and of the influence which increasing substitution on H4Ru4(CO)12 plays on the formation of active sites. The complexity of this multistep process, however, does not allow a comprehensive rationalisation of the experimental data.

Hydrogenation of pentynes with Rh4(CO)12 and Rh2(CO)4Cl2 in solution and anchored on Al2O3

Abstract The catalytic activities of Rh 4 (CO) 12 and Rh 2 (CO) 4 Cl 2 for the homogeneous hydrogenation of pentynes in toluene have been studied and compared with those of these complexes anchored on γ-Al 2 O 3 . Rh 4 (CO) 12 and Rh 2 (CO) 4 Cl 2 interact strongly with γ-Al 2 O 3 , and the resulting species give identical IR spectra in the CO stretching region characterised by absorptions at 2080 cm −1 and 1997 cm −1 , suggesting that the same carbonylrhodium active centres are formed upon binding of both metal carbonyls. However, Rh 4 (CO) 12 /Al 2 O 3 and Rh 2 (CO) 4 Cl 2 /Al 2 O 3 show completely different behaviour as catalysts in the hydrogenation of pentynes; Rh 2 (CO) 4 Cl 2 /Al 2 O 3 is more active than Rh 2 (CO) 4 Cl 2 in solution, while the activity of Rh 4 (CO) 12 is not substantially altered upon going from the homogeneous to the heterogenised system. Complete hydrogenation to give pentane is favored when Rh 2 (CO) 4 Cl 2 and Rh 4 (CO) 12 are bound to Al 2 O 3 , and occurs much more slowly when the complexes are used as homogeneous catalysts.

Activation of a carbon—nitrogen triple bond in the presence of Ru3(CO)12 and H4Ru4(CO)12

Abstract The reaction of PhCN with Ru 3 (CO) 12 in the presence of acetic acid gives H 4 Ru 4 (CO) 12 , (I), (μ-H)Ru 3 (CO) 10 (μ-NCHPh) (II) and (μ-H)Ru 3 (CO) 10 (μ-NH-CH 2 Ph) (III) as the main products. Reaction under 110 atm of H 2 gives more III and also gives benzylamine. Replacement of acetic acid by H 2 at atmospheric pressure gives only II. When H 4 Ru 4 CO) 12 reacts with PhCN alone or in the presence of NaOH, II is formed as the only product. The structures of II and III have been fully elucidated by X-ray methods. The nitrogen atom of the NCHPh ligand in II and that of the NHCH 2 Ph ligand in III, interact with the isosceles-triangular metal cluster, symmetrically bridging the shortest Ru(1)-Ru(2) edge. A hydride ligand in both II and III bridges the same Ru(1)-Ru(2) edge of the cluster. Under mild conditions acetic acid is an essential requirement for the activation of Ru 3 (CO) 12 for reaction with PhCN to give III, which cannot be obtained under these conditions from II.

Hydrogenation of pentynes and of pentadienes catalysed by Ru3(CO)12, Fe3(CO)12 and mixed metal RuFe dodecacarbonyls supported on γ-Al2O3

Abstract Hydrogenation under mild conditions of 1- and 2-pentyne and of 1,3-cis- and 1,3-trans-pentadiene catalysed by Ru3(CO)12, FeRu2(CO)12, Fe2Ru(CO)12 and Fe3(CO)12 in toluene solutions or anchored on γ-Al2O3 has been studied. For all the systems examined, catalytic activity was highest for Ru3(CO)12-containing catalysts and lowest for Fe3(CO)12-containing ones. For mixed metal catalysts, activity decreased with increasing number of Fe atoms in the dodecacarbonyls. Anchorage of the clusters to γ-Al2O3 produced catalysts which were less active towards hydrogenation of 1- and 2-pentyne and more active towards hydrogenation of 1,3-cis- and 1,3-trans-pentadiene, but had no effect on product distribution.