A. J. Arce

Oxidative addition of 2-formyl-furan and related pyrrole and thiophene compounds at triosmium clusters

Abstract The bridging acyl complexes [Os 3 H(μ-COC 4 H 3 X)(CO) 10 ] (X = NH, O, or S) have been prepared by oxidative addition of the 2-formyl derivatives of pyrrole, furan, or thiophene (C 4 H 3 XCHO) at [Os 3 (CO) 10 (MeCN) 2 ] with cleavage of the aldehydic CH bonds. On heating double decarbonylation of the acyl complexes occurs, to afford high yields of the compounds [Os 3 H 2 (CO) 9 (μ 3 -C 4 H 2 X)], reported previously for X = NH or O. For X = NH, two isomers with this formulation were characterised by 1 H NMR and IR data; the one containing the μ 3 -2,3-C 4 H 3 N ligand isomerises to one containing μ 3 -1,2-C 4 H 3 N. The direct reaction of pyrrole with [Os 3 (CO) 12 ] has been re-examined at lower temperatures than before, and observed to give new products, including [Os 3 H(CO) 10 (C 4 H 4 N)], which contains a bridging non-aromatic tautomeric form of pyrrole. The ability of Os 3 clusters to stabilize non-aromatic tautomers of aromatic ligands is discussed.

Triosmium clusters derived from α,β-unsaturated aldehydes

Abstract The compounds [Os 3 H 2 (CO) 10 ] and [Os 3 (CO) 10 (MeCN) 2 ] both react with the aldehydes RCHCHCHO (R = Me or Ph) with competitive oxidative additions of the vinylic CH groups, to give compounds of the type [Os 3 H(CO) 10 (RCCHCHO)], or of the aldehydic groups to give acyl clusters of the type [Os 3 H(CO) 10 (RCHCHCO)]. The alkyne PhCCCHO reacts with [Os 3 H 2 (CO) 10 ] to give [Os 3 H(CO) 10 (PhCCHCHO)], but also two other isomers as a cis - trans mixture of [Os 3 H(CO) 10 (PhCHCCHO)], which are converted in acetone into the PhCCHCHO compound and free cinnamaldelyde. In each of these Os 3 compounds there are OsO bonds.

Stabilisation of alkyl compounds of the type Os3H(alkyl)(CO)10 formed by alkene insertion into Os3H2(CO)10

Abstract The hydrido cluster Os 3 H 2 (CO) 10 reacts with neat methyl vinyl ether to give two isomers of the insertion product Os 3 H(μ-MeCHOMe)(CO) 10 which are stabilised by ether coordination in the 1-methoxyethyl bridge but slowly revert to the dihydride on standing in solution. The clusters Os 3 H(CHCH 2 )(CO) 10 , Os 3 (CHCH)(CO) 10 , Os 3 H 2 (CCH 2 )(CO) 9 and Os 3 H 3 (CCH 3 )(CO) 9 are formed as minor products from CO ether cleavage at room temperature or on thermolysis. One product from heating the 1-methoxyethyl compound in refluxing n-heptane, the 1-methoxyethylidene compound Os 3 H 2 (μ 3 -MeCOMe)(CO) 9 , retains the CO bond.

Alkyne Coupling Induced by a Trinuclear Ruthenium Cluster: Synthesis and Structure of Di-μ-carbonyl-hexacarbonyl-μ3-(1,2,3,4-tetraphenyl-1,3-butadiene-1,4-diyl)-triruthenium(2 Ru—Ru), [Ru3(CO)8(C4Ph4)]

The reaction of PhC≡CPh with [Ru 3 (CO) 10 (MeCN) 2 ] affords two [Ru 3 (CO) 8 (C 2 Ph 2 )2] complexes, one red-violet containing only terminal carbonyl groups and the other the orange-yellow title compound, di-μ-carbonyl-1:2κ 2 C;1:3κ 2 C-hexacarbonyl-1κ 2 C,2κ 2 C,3κ 2 C-μ 3 -[1,2,3,4-tetraphenyl-2(η 4 ):3(η 4 )-1,3-butadiene-1,4-diyl-1κ 2 C]-triruthenium(2 Ru-Ru). The structure of the latter isomer consists of an open Ru 3 cluster [Ru-Ru 2.6696 (8) and 2.6717 (6), Ru...Ru 3.7461(7) A] coordinated to the C 4 Ph 4 ligand, formed by the dimerization of PhC≡CPh, and to eight CO groups, six terminal and two bridging. The central Ru atom is σ-bonded to the butadiene moiety to form an RuC 4 metallacyclopentadiene ring [Ru-C 2.219(4) and 2.216(4); mean C-C 1.461 A]. Each of the other two metal atoms is η 4 -bonded to the C atoms of the RuC 4 ring [mean Ru-C 2.322 A] to form a pentagonal bipyramidal Ru 3 C 4 core.

Hexacarbonyl-1κ4C,2κ2C-[μ-1κC6:2(η5)-6-methylfulvene] diruthenium (Ru-Ru), [Ru2(C5H4CHCH3)(CO)6]

The reaction of spiro[2.4]hepta-4,6-diene with [Ru 3 (CO) 12 ] leads to the title compound, a diruthenium-fulvene complex which contains a μ-1κC :2(η 5 )- (or, simplistically, μ-η 1 :η 5- ) C 5 H 4 CHCH 3 bridging ligand. The Ru-Ru distance is 2.7954 (8)A, while Ru-ligand distances are : Ru-C(η 1 ) 2.232(8)A, average Ru-C(Cp) (Cp = cyclopentadienyl) 2.237A, average Ru-C(CO) 1.945/1.879A with/without trans influence. Excepting the methyl group, the molecule has approximate m point symmetry.

Nonacarbonyl[μ3-(1,2-diphenylethyl)-phenylphosphinito]triosmium(2 Os-Os)

The reaction of 1,2,3-triphenylphosphirene with [H2Os3(CO)10] leads to the title compound, [Os3(CO)9{(C6H5)3C2PO}], which displays an open Os3(CO)9 cluster [Os—Os 2.703 (1) and 2.867 (2) A, and Os—Os—Os 124.24 (4)°]. This moiety is μ3,η3-bonded to a phosphirene ligand with a cleaved P—C bond, PhC—C(Ph)—P. An O atom was incorporated into the molecule resulting in an unusual five-membered metallacycle, Os—C—C—P—O, with distances Os—C 2.10 (1), C—C 1.46 (2), C—P 1.76 (1), P—O 1.628 (9) and O—Os 2.136 (9) A. This ring makes a dihedral angle of 57.3 (2)° with the plane of the metal atoms.

trans-1,1'-Bis(indenylidene)

The title compound, (C 9 H 6 ) 2 , was obtained by the coupling of the carbene C 9 H 6 : derived from 1-diazo-indene, C 9 H 6 N 2 , in the presence of [Ru 3 (CO) 12 ]. The molecule is centrosymmetric and completely planar. The six-membered rings have aromatic character and are connected by an extended π-electron system.

Isomeric clusters [Ru4(µ4-PPh)(µ4-C4H3N)(CO)11] containing diagonal C,C and parallel C,N bonded pyrrolyne ligands

The three isomeric tertiary phosphines, diphenyl- n-pyrrolylphosphine ( n = 1, 2 or 3) lead to two isomeric tetranuclear clusters [Ru 4(µ 4-PPh)(µ 4-C 4H 3N)(CO) 11] which contain the diagonal C,C bonded and parallel C,N bonded pyrrolyne ligands.

Perpendicular versus parallel alkynes, monohapto versus dihapto vinyls, aromatic versus non-aromatic heterocycles: access to different types of bonding of these ligands in clusters

Abstract Triply-bridging alkyne ligands in trimetallic clusters adopt one of three distinct coordination types. The most common system is the 48-electron cluster with the plane of the alkyne tilted to the metal plane and with the C—C axis parallel to a metal—metal edge. In the other two types the alkyne plane is perpendicular (vertical) to the horizontal metal plane with the C—C axis perpendicular to a metal-metal edge. These two are 46- and 48-electron clusters respectively and are only distinguishable by the number of M — C bonds, the 46-electron system having more. The perpendicular 48-electron form is favoured by the presence of π-donor substituents on the ligand and structures between this and the parallel 48-electron form are observed. Doubly-bridging vinyl ligands are either tilted and dihapto or vertical and monohapto . The structure adopted depends upon the π-donor capacity of the substituents and intermediate structures are found. Five-membered heterocyclic derivatives based on furan, thiophene and pyrrole give geometric forms very closely related to those of the vinyls but in these cases the vertical form is disfavoured by aromaticity and only the N-methylpyrrolyl compound is found to be vertical.