Enrico Sappa

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.

Stereochemically nonrigid carbonyl complexes of group VIII B metal clusters

Abstract The variable temperature 13 C-nmr of M 3 (CO) 12 (M = Fe, Ru, Os) have been studied. Fe3(CO)12 and Ru 3 (CO) 12 give one sharp resonance down to −100° C. Os 3 (CO) 12 shows two resonances at room temperature which coalesce to a single resonance at +150 C. Possible mechanisms for carbonyl averaging are considered. The 13C-nmr of the acetylenic complexes HM3(CO)9C2C(CH3)3 (M = Ru, Os) were examined and shown to be stereochemically nonrigid. Both the osmium and ruthenium compounds show axial equatorial exchange on the metal atom which is sigmabonded to one of the acetylenic carbons. Only the ruthenium compound shows exchange between metal atoms in the temperature range examined. The importance of bridging intermediates in this exchange process is discussed.

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.

The Reactivity of HRu3(CO)9C2BUt. The Synthesis and crystal structure of (PPH3)AuRu3(CO)9C2BUt, a new ruthenium-gold cluster

Abstract The (PPh 3 )AuRu 3 (CO) 9 C 3 Bu t complex has been obtained by reacting (PPh 3 )AuCl with the anionic complex [Ru 3 (CO) 9 C 2 Bu t ] − , prepared from the hydride HRu 3 (CO) 9 C 2 Bu t with a new procedure. The crystal structure of this heterometallic complex, as acetone solvate, has been determined by X-ray methods: it crystallizes in the orthorhombic space group F dd2, with 16 molecules in a unit cell of dimensions a = 33.64(2), b = 48.38(2), c = 9.23(1) A. The structure has been solved from diffractometer data by direct and Patterson methods, and refined by full-matrix least-squares to R = 0.068 for 1628 observed reflections. The complex consists of a AuRu 3 cluster in a butterfly arrangement with the Au atom on a wingtip. The Au atom of the Au(PPh 3 ) group bridges one side of the ruthenium triangle and practically substitutes the hydride ligand of the HRu 3 (CO) 9 C 2 -Bu t complex, maintaining the basic features of the Ru 3 (CO) 9 C 2 Bu t framework virtually unchange.

Reactions of Ru3(CO)12 with chalcogen compounds

Abstract Attempts to synthesize the compounds Ru3(CO)9X2(X = S,Se,Te) bytreating Ru3(CO)12 in alkaline solution with chalcogen compounds gave the substituted hydrides of the series H2Ru3(CO)9X (X = S,Se,Te), which were isolated and characterised. The same products were obtained under other conditions also. The NMR and mass spectra are discussed, and possible structures for these paramagnetic complexes are suggested.

Acetylenic derivatives of metal carbonyls I. Substitution reactions of CO2(CO)6C2RR′ complexes

Abstract In this work the substitution reactions were studied, of one acetylenic derivative, by another, in the complexes Co 2 (CO) 6 C 2 RR′ in which R and R′CF 3 , COOCH 3 , C 6 H 5 , CH 2 Cl, CH 3 , CH 2 N(C 2 H 5 ) 2 and H. On the basis of such reactions, relative stabilities of the various acetylenic derivatives were determined and discussed in terms of the acceptor character of the different acetylenes. Also reported are the preparations and properties of some new compounds of this series.

The reactions of ruthenium carbonyl and alkyne-carbonyl complexes with nickelocene, [(η-C5H5)Ni(CO)]2 and (η-C5H5)2Ni2(RC2R′). Cyrstal structures of two isostructural heterometallic trinuclear clusters, (η-C5H5)2Ni2Ru(CO)3(C2Ph2) and (η-C5H5)2Ni2Fe(CO)3(C2Ph2)

The reactions of nickelocene, [(η-C5H5)Ni(CO)]2 and (η-C5H5)2Ni2(RC2R”) (R = H, R′ = But; R = R′ = Et, Ph) with Ru3(CO)12, H4Ru4(CO)12, HRu3(CO)9C2But and HRu3(CO)9(C6H9) are reported and compared with those of the iron carbonyls and alkyne-carbonyls. Some new products have been identified and characterized by spectroscpic analyses. The isostructural trimetallic (η-C5H5)2Ni2Fe(CO)3(C2Ph2) (V) and (η-C5H5)2Ni2Ru(CO)3(C2Ph2) (Va) have been studied by X-ray methods. Crystals of V and Va are monoclinic, space group Cc. Unit cell parameters for V are: a = 9.334(8), b = 26.717(13), c = 9.143(8)A, β = 95.15(7)°, and for Va: a = 9.201(9), b = 27.076(15), c = 9.303(8) A, β = 94.94(7)°. Both structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.049 for V and 0.044 for Va. The complexes consist of a triangular cluster formed by two Ni and one Fe atoms and two Ni and one Ru atoms, respectively. A cyclopentadienyl ligand is η-bonded to each Ni atom and three terminal carbonyls are attached to the unique metal atom. The diphenylacetylene, σ-bonded to the Ni atoms and π-bonded to Fe or Ru atom, lies almost parallel to the NiNi side of the cluster. The clusters are considerably smaller in size than other complexes of comparable structure. The elongation of the acetylenic CC bond is different in the two complexes V and Va, although the alkyne—metal interactions are comparable.

Complexes of transition metal carbonyls with alkynes. Closo- and nido-pentagonal bipyramidal clusters

Abstract A short review of the synthetic methods, structures and isolobal relationships of the closo M 3 (CO) 8 (RC 2 R′) 2 and of the nido M 2 (CO) 6 (RC 2 R′) 2 pentagonal bipyramidal complexes (M=Fe, Ru, Os) and of some related compounds is given. The role of these complexes in organic synthesis and in catalysis is discussed.

Metal-Carbonyl Clusters with Alkynes Bound in "Parallel" or "Perpendicular" Fashion

Alkyne-substituted tri- and polynuclear clusters have been known for a long time. Among these, the derivatives with acetylene substituents coordinated parallel to one edge of a trimetallic cluster represent the majority. Clusters with alkynes perpendicular to one edge of a trimetallic cluster are not very common. The reactivity of these clusters is discussed in this paper; particular attention is devoted to the chemical transformations which could occur during catalytic reactions. Some examples of the behavior of these clusters in homogeneous and solid–gas hydrogenation catalysis are given.

Heterometallic clusters in homogeneous catalysis. Hydrogenation of diphenylacetylene and isomerization of cis-stilbene in the presence of [Fe2Ru(CO)12], [FeRu2(CO)12], [H2FeRu3(CO)13], [H2Ru4(CO)13], and related compounds. Identification of organometallic complexes and a discussion of their role

Abstract The clusters [M 3 (CO) 12 ], (M  Ru or Fe), [Fe 2 Ru(CO) 12 ], [FeRu 2 (C0) 12 ], [H 4 Ru 4 (CO) 12 ] and [H 2 M′M 3 (CO) 13 ] (M  Ru, M′  Fe or Ru) have been tested as homogeneous catalysts for the hydrogenation of C 2 Ph 2 and isomerization of cis -stilbene. The effect of the cluster stoichiometry, of dihydrogen and of the substrate/cluster ratio have been evaluated. There is evidence of competition between dihydrogen, which favours the formation of catalytically active hydrides or “metal fragments”, and C 2 Ph 2 , which favours metal-fragment condensation to give alkyne-substituted clusters; with the exception of [H 2 Ru 3 (CO) 9 C 2 Ph 2 ], these derivatives are stable by-products and react slowly with dihydrogen, giving only small amounts of hydrogenation products. The alkyne-substituted derivatives found in the hydrogenation solutions are the reported products of the reactions of iron, ruthenium or iron-ruthenium carbonyl clusters with C 2 Ph 2 under dinitrogen; however, there are differences in the yields. Moreover, in the reactions of [H 2 Ru 4 (CO) 13 ] or [H 2 FeRu 3 (CO) 13 ], a new derivative was obtained; this was characterized spectroscopically as a third isomer of [Ru 3 (CO) 8 (C 2 Ph 2 ) 2 ].