Marcia Martinelli

Synthesis and characterisation of [Ru3(CO)9(µ3-η2:η2:η2-C6H6)]

The cluster benzene complex [Ru3(CO)9(µ3-η2:η2:η2-C6H6)] which contains a benzene ligand in a face-capping co-ordination mode has been prepared, and its molecular structure investigated by a single crystal X-ray analysis which provides unambiguous evidence for C–C length alternation.

Synthesis of [M3H(CO)9(µ3-σ:η2:η2-C6H7)](M = Ru or Os). Molecular and crystal structure of the ruthenium cluster

The dienyl cluster compounds [M3H(CO)9(µ3-σ:η2:η2-C6H7)](M = Ru or Os) have been synthesised from [Os3H2(CO)10] or [M3(CO)10(MeCN)2](M = Ru or Os) with cyclohexa-1,3-diene. The molecular and crystal structure of [Ru3H(CO)9(C6H7)] has been established by single-crystal X-ray diffraction analysis: monoclinic, space group P21, a= 8.487(6), b= 12.031(3), c= 9.073(2)A, β= 92.43(4)° and Z= 2. The cyclohexadienyl ligand is involved in one σ and two π interactions with the metal triangle, while the H(hydride) ligand bridges the long Ru–Ru bond [3.052(1)A]. The other two Ru–Ru bond lengths are the same [2.837(1)A] and comparable to those observed in [Ru3(CO)9(µ3-η2:η2:η2-C6H6)]. The H(hyride) position afforded by the diffraction experiment has been compared with the result of potential-energy minimization procedures. The molecular organization within the lattice has been explored by means of atom–atom packing potential-energy calculations showing the presence of a network of C–H ⋯ O intermolecular hydrogen-bonding interactions.

The coordination of benzene in clusters : the face-capping mode

Abstract The use of discrete metal cluster complexes as models of chemisorption systems in surface chemistry is an attractive hypothesis and has been emphasised by numerous workers in recent years. In this paper we shall examine possible boundary conditions to such a cluster-surface analogy, drawing extensively on the interfacial chemistry of benzene. The motivation for this work is provided by the molecular chemistry of a new class of arene clusters in which the arene molecule is bonded to an M3 triangulo-face within the cluster. The parent compounds in these studies, [M3(CO)9(μ3:η2:η2:η2-C6H6)] (M = Ru or Os), contain benzene in this important new face-capping bonding mode that accurately models benzene adsorption at a threefold site on the surface of a close-packed metal lattice. X-ray diffraction studies combined with NMR (1H and13C) and infrared spectroscopic studies lead to the conclusion that the benzene is coordinated to the metal triangle and is best viewed as a bond-localised cyclohexa-1,3,5-triene.

High-nuclearity clusters

The use of discrete metal cluster compounds as models of chemisorption systems in surface chemistry is described. Possible boundary conditions to such a cluster–surface analogy are examined; drawing extensively on the interfacial chemistry of benzene. In particular, the complex [Os3(CO)9(µ3-C6H6)], which contains benzene in an important new face-capping bonding mode that accurately models benzene adsorption at a three-fold site on the surface of a close-packed metal lattice will be described and its chemistry discussed.

Synthesis and characterization of the bis-arene sandwich cluster [Ru6C(CO)11(η6-C6H3Me3-1,3,5)2]

The bis-arene cluster complex [Ru6C(CO)11(η6-C6H3Me3-1,3,5)2]1 has been synthesised and characterized by single-crystal X-ray diffraction; it possesses a unique structure in which the octahedral cluster core is sandwiched between the two arenes.

On the relationship between crystallographic and spectroscopic evidence of dynamic processes in the solid state. The case of the osmium cluster ‘helicopters’

The reorientational motion of the C6H6 and CH2CH2 ligands in [Os3(CO)8(η2-CH2CH2)(µ3-η2: η2: η2-C6H6)], evidenced in the solid by 13C cross-polarization magic angle spinning n.m.r. spectroscopy, has been examined by means of the atom–atom potential energy method. The results show that the motion of the ethene fragment is correlated to that of the benzene fragment and controlled primarily by intramolecular energy terms, while the crystal packing does not create relevant intermolecular barriers. The possibility of similar reorientational processes in solid [Os3(CO)7(µ3-σ : η2 : σ-C2Me2)(η6-C6H6)] has also been explored and the results compared with the X-ray crystallographic indication of extensive in-plane librational motion of the C6H6 ligand. In neither case does reorientation of the Os(CO)3 groups appear to be a possibility.

Trinuclear benzene clusters of ruthenium and osmium

The activated cluster [Os3(CO)7(µ3-η2:η2:η2-C6H6)(C2H4)(MeCN)] reacts with alkynes RC2R′(R = R′= H, Ph or Me; R = H, R′= Ph; R = Me, R′= Et) to produce the new clusters [Os3(CO)7(η6-C6H6)(µ3-η2-RC2R′)] in which the benzene molecule has migrated to a single osmium atom. In contrast, reaction of the ruthenium cluster [Ru3(CO)9(µ3-η2:η2:η2-C6H6)] with similar alkynes RC2R′(R = R′= H, Ph or Me; R = Ph, R′= H) yields the new clusters [Ru3(CO)7(η6-C6H6)(µ3-η2-RC2R′CO)] in which carbonyl insertion has occurred. The molecular structures of [Os3(CO)7(η6-C6H6)(µ3-η2-C2Me2)] and of [Ru3(CO)7(η6-C6H6)(µ3-η2-PhC2PhCO)] have been established by single-crystal X-ray analysis. The C6H6 ligand is η6-bonded to a single metal atom, while the C2Me2 and the PhC2PhCO ligands lie above the metal triangles and are bonded to the three metal atoms via two σ interactions and one π interaction.

Benzene migration in an osmium cluster: the formation of Os3(CO)7(?6-C6H6)(3 : ?1 : ?2 : ?1-C2Me2) from Os3(CO)9(3 : ?2 : ?2 : ?2-C6H6). The crystal structure of Os3(CO)7(?6-C6H6)(3 : ?1 : ?2 : ?1-C2Me2)

The activated cluster [Os3(CO)7(C2H4)(µ3 : η2 : η2 : η2-C6H6)(MeCN)] reacts with alkynes RC2R′(R = R′= H, Ph or Me; R = H, R′= Ph; R = ME, R′= Et), to produce the new clusters [OS3(CO)7(η6-C6H6)(µ3 : η1 : η2 : η1-RC2R′)] in which the benzene is bonded to a single metal atom as shown by a single crystal X-ray structure determination of the C2Me2 derivative.