Catherine A. Morewood

The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)32] and [Os8(CO)20(η6-C6H6]

Reduction of the heptaosmium cluster [Os7(CO)21] With [Et4N][NH4) gives the cluster dianion [Os7(CO)20]2−,1, in high yield. The reaction of the dianion with [AuPR3Cl] (R=Et or Ph) in the presence of TlPF6 forms [Os7((CO)20(AuPR3)2] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C6H6)(CH3CN)3]2+ gives [Os8(CO)20 (η6-C6H6)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph4P]+ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt3 groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C6H6) unit capped to a triangular face, to give a bicapped octahedral framework.

Cluster build-up using the [Os(η6-C6H6)(MeCN)3]2+ cation; synthesis and structural characterisation of some hexa- and hepta-nuclear arene-substituted clusters

Reactions of the cluster dianion [Os5(CO)15]2– with [Os(η6-C6H6)(MeCN)3]2+ and [Os(C6H5Me)(CF3SO3)2] provided [Os6(CO)15(η6-C6H6)]1 and [Os6(CO)15(η6-C6H5Me)]2, respectively, in good yield (≈45%). Reduction of the hexaosmium cluster [Os6(CO)18] with K–Ph2CO gave the cluster dianion [Os6(CO)17]2–3 in quantitative yield. When this dianion was treated with [Os(η6-C6H6)(MeCN)3]2+ the heptanuclear cluster [Os7(CO)17(η6-C6H6)]4 was obtained in fair yield, while the corresponding reaction with [Os(η6-C6H5Me)(CF3SO3)2] gave [Os7(CO)17(η6-C6H5Me)]5 in similar yield (ca. 25%). The four arene clusters have been characterised by spectroscopic techniques, and the molecular geometries of 1, 2 and 4 established by single-crystal X-ray diffraction techniques. In both 1 and 2 the metal framework geometry is best described as a bicapped tetrahedron. In 1 the η6-C6H6 ligand occupies a site on the central Os4 tetrahedron while in 2 in the η6-arene is co-ordinated to one of the capping Os atoms. The metal framework in 4 may be viewed as derived from a bicapped tetrahedron with the seventh metal capping one of the caps to give a chain of four fused tetrahedra. The η6-C6H6 ligand in 4 occupies a similar site to that found in 1.

Use of [Ru(η5-C5H5)(MeCN)3]+ as a capping reagent in cluster build-up: synthesis and structural characterisation of [Os5Ru2(CO)15(η5-C5H5)2]

Ionic coupling of the mononuclear cation [Ru(η5-C5H5)(MeCN)3]+ with the cluster dianion [Os5(CO)15]2– afforded the neutral heptanuclear cluster [Os5Ru2(CO)15(η5-C5H5)2] which has been shown by X-ray diffraction studies to contain a tricapped tetrahedral metal core.

Mixed alkyne-arene-substituted carbonyl clusters; the crystal and molecular structure of OS4(CO)9(η6-C6H6)(MeCCMe)

Reaction of the alkyne-substituted cluster anion [Os3(CO)9(R1CCR2)]2− with the cation [Os(η6-C6H6)(CH3CN)]2+ affords the neutral tetranuclear cluster Os4(CO)9(η6-C6H6)(R1CCR2) (R1=R2=Me (1a); R1=Me, R2=Ph (1b); R1=R2=Ph (1c)). The structure of 1a has been confirmed by a single-crystal X-ray analysis. The metals adopt a ‘butterfly’ geometry with the alkylenic CC vector parallel to the ‘hinge’ vector of the ‘butterfly’, and the η6-C6H6 ligand occupies a terminal site on one of the ‘wingtip’ Os atoms. Complexes 1a and 1b may also be prepared by the reaction of the activated arene cluster Os4H2(CO)9(η6-C6H6)(CH3CN) with MeCCMe and MeCCPh, respectively. Under similar reaction conditions, with PhCCPh, the arene and acetonitrile ligands are substituted by the alkyne to give the known complex Os4H2(CO)9(PhCCPh)2 (2c).

Cyclohexadiene-linked clusters: synthesis and molecular structure of [{Os4(CO)8(MeCCMe)(η6-C6H6)}2(μ2-η2:η2-C6H8-1,3)]

Abstract The reaction of [Os 4 (CO) 9 (RCCR)(η 6 -C 6 H 6 )] (R=Me, Ph) with Me 3 NO in the presence of 1,3-cyclohexadiene or 1,4-cyclohexadiene yields the clusters [{Os 4 (CO) 8 (RCCR)(η 6 -C 6 H 6 )} 2 (μ 2 -η 2 :η 2 -C 6 H 8 -1,3)] and [{Os 4 (CO) 8 (RCCR)(η 6 -C 6 H 6 )} 2 (μ 2 -η 2 :η 2 -C 6 H 8 -1,4)], respectively. The molecular structure of [{Os 4 (CO) 8 (MeCCMe)(η 6 -C 6 H 6 )} 2 (μ 2 -η 2 :η 2 -C 6 H 8 -1,3)] has been determined by single crystal X-ray diffraction, and represents the first example of two osmium cluster fragments linked by 1,3-cyclohexadiene through a μ 2 -η 2 :η 2 -bridge.

Use of the monocationic fragment [Ru(η5-C5H5)(MeCN)3]+ as a capping reagent in the synthesis of mixed-metal clusters: synthesis and structural characterisation of [Os3RuH(CO)11(η5-C5H5)] and [Os3Ru2(CO)9(µ3-CO)2(η5-C5H5)2]

The reaction of the monoanion [Os3H(CO)11]– 1 with 1 equivalent of the cation [Ru(C5H5)(MeCN)3]+ 2, in CH2Cl2, formed the mixed-metal, tetranuclear cluster [Os3RuH(CO)11(η5-C5H5)] 3 in high yield. Subsequent deprotonation of 3 with 1,8-diazabicyclo[5.4.0]undec-7-ene, in CH2Cl2, afforded the anion [Os3Ru(CO)11(η5-C5H5)]– 4, and reaction of 4 with a second equivalent of [Ru(C5H5)(MeCN)3]+ provided the new bis-(cyclopentadienyl) cluster [Os3Ru2(CO)9(µ3-CO)2(η5-C5H5)2] 5 in ca. 80% yield. Alternatively, reduction of [Os3(CO)12] with K/Ph2CO afforded the known cluster dianion [Os3(CO)11]2– 6 which can be treated with 2 equivalents of [Ru(C5H5)(MeCN)3]+ to produce 5 in 75% yield. The clusters 3 and 5 have been fully characterised by both spectroscopic and crystallographic methods. The structure of 3 contains an Os3Ru tetrahedron in which the cyclopentadienyl ligand is co-ordinated to the Ru atom in an η5 terminal mode. The metal framework in 5 is a trigonal bipyramid, but may be viewed as an Os3Ru tetrahedral unit, as in 3, to which a second Ru atom capping an Os2Ru triangular face has been added. Both the cyclopentadienyl ligands remain in η5 terminal bonding sites co-ordinated to the two Ru atoms.

Cluster build-up using the[Ru(η5-C5H5)(MeCN)3]+ cation; synthesis and structural characterisation ofsome cyclopentadienyl-substituted hexa- and hepta-nuclear rutheniumcarbido clusters

The reaction of the dianion [Ru 5 C(CO) 14 ] 2- with 2 equivalents of [Ru(η 5 -C 5 H 5 )(MeCN) 3 ] + afforded two new clusters, the hexanuclear anion [Ru 6 C(CO) 14 (η 5 -C 5 H 5 )] - 1 and the neutral heptanuclear cluster [Ru 7 C(CO) 14 (η 5 -C 5 H 5 ) 2 ] 2 in high yields. In a similar reaction the hexanuclear dianion [Ru 6 C(CO) 16 ] 2- may be ‘capped’ by [Ru(η 5 -C 5 H 5 )(MeCN) 3 ] + to afford good yields of both the heptanuclear monoanion [Ru 7 C(CO) 16 (η 5 -C 5 H 5 )] - 3 and the neutral cluster 2. The clusters 1, 2 and 3 have been fully characterised by both spectroscopic and crystallographic methods. The crystal structures show that the metal framework of all three clusters is based on a central Ru 6 C octahedral core. In 1 one of the core atoms is co-ordinated to an η 5 -C 5 H 5 ligand, while in 2 an additional Ru(η 5 -C 5 H 5 ) group caps one triangular face of the octahedron to give a capped octahedral framework. In 3 the single η 5 -C 5 H 5 ligand is co-ordinated to the capping Ru atom in the capped octahedral framework.