Decanuclear Cluster Research Articles

Solvent-induced structural transformation from heptanuclear to decanuclear [Co-Ln] coordination clusters: trapping of unique counteranion and understanding of aggregation pathways.

Five new cobalt(ii/iii)-lanthanide(iii)-based coordination aggregates, [LnIII3CoII2CoIII2(L1)2(O2CCMe3)8(OH)4(OMe)2(H2O)4]·Ln(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2·2MeOH·2H2O (where Ln = Tb (1), Ho (3), and H2L1 = N-(2-hydroxyethyl)-salicylaldimine), TbIII3CoII3CoIII4(L1)4(O2CCMe3)9(OH)10(H2O) (4) and LnIII3CoII2CoIII5(L1)4(O2CCMe3)10(OH)10 (Ln = Dy (5), Ho (6)) have been synthesized and characterized, including structural analysis via single-crystal X-ray diffraction. The dysprosium analogue (2) of 1 and 3 was previously reported by us. The heptanuclear monocationic clusters in 1 and 3 were formed by placement of seven metal ions (4 Co and 3 Ln) in a vertex shared dicubane structure from the control of two Schiff base anions and crystallized in the presence of in situ generated and literature unknown counter anions Tb(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2- and Ho(η1-O2CCMe3)2(η2-O2CCMe3)2(MeOH)2-. Interesting solvent-induced cluster structure transformation was observed on dissolving the heptanuclear aggregates in MeCN for the formation of decanuclear clusters 4-6. These high nuclearity clusters consist of a vertex shared heptanuclear dicubane part and a curved trinuclear chain linking the two cubic halves. The dicubane unit differs from that of the heptanuclear precursors in the presence of CoII/III at the shared vertex as opposed to LnIII and the absence of OMe- bridges. HRMS (+ve) analysis shed light on the pathway of formation of these heptanuclear molecules, while at the same time revealing a different aggregation process for the decanuclear clusters.

Aggregation-induced phosphorescence sensitization in two heptanuclear and decanuclear gold-silver sandwich clusters.

The strategy of aggregation-induced emission enhancement (AIEE) has been proven to be efficient in wide areas and has recently been adopted in the field of metal nanoclusters. However, the relationship between atomically precise clusters and AIEE is still unclear. Herein, we have successfully obtained two few-atom heterometallic gold–silver hepta-/decanuclear clusters, denoted Au6Ag and Au9Ag, and determined their structures by X-ray diffraction and mass spectrometry. The nature of the AuI⋯AgI interactions thereof is demonstrated through energy decomposition analysis to be far-beyond typical closed-shell metal–metal interaction dominated by dispersion interaction. Furthermore, a positive correlation has been established between the particle size of the nanoaggregates and the photoluminescence quantum yield for Au6Ag, manifesting AIEE control upon varying the stoichiometric ratio of Au : Ag in atomically-precise clusters.

A Series of High‐nuclear 3d‐4f (FeIII8LnIII2) Complexes: Syntheses, Structures, and Magnetic Properties

Six novel decanuclear clusters with formula of {[Fe8Ln2(O)4(OH)4(EtO)2(dhbp)4(dhbpH)2(piv)6]·4EtOH} (Ln = Y (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), dhbpH2 = 6,6′‐dihydroxyl‐2,2′‐bipyridine, Hpiv = pivalic acid, EtOH = ethanol) have been synthesized and characterized. Single‐crystal and powder X‐ray diffraction analyses reveal that complexes 1–6 are isostructural and show a sandwich‐like FeIII8LnIII2 structure, in which the [Ln2] unit is sandwiched by two planar [Fe4] units. Magnetic properties of complexes 1–6 have been investigated and display dominant antiferromagnetic interactions, thereinto, complexes 4 and 6 display weak ferromagnetic behaviors associated with LnIII ions, while others are antiferromagnetic‐like features. Furthermore, complex 4 (FeIII8DyIII2) shows temperature/frequency‐dependent ac signals with an energy barrier of 4.1 K, indicating that complex 4 should be a single‐molecule magnet (SMM)

A series of [Na2MnII2MnIII6] clusters derived from trigonal bipyramidal [NaMnIIMnIII3] subunits bridged by mono-, di- and tri-fold azide groups: synthesis, crystal structures and magnetic properties

A series of [Na2MnII2MnIII6] clusters derived from trigonal bipyramidal [NaMnIIMnIII3] subunits bridged by mono-, di- and tri- fold azide groups Na[Na2MnII2MnIII6(μ3-O)2(HL1)6(μ1,3-N3)(HCOO)8(H2O)2](ClO4)2 (1), [Na2MnII2MnIII6(μ3-O)2(L2)6(μ1,1-N3)4(μ1,3-N3)2(N3)2(CH3OH)2] (2) and [Na2MnII2MnIII6(μ3-O)2(L3)6(μ1,1-N3)7(N3)2(H2O)2] (3) have been obtained via the self-assembly of different potentially multidentate Schiff base ligands and auxiliary ligands (azide ions and formate ions) with divalent manganese salt in an air-exposed water-methanol solution. The structures of 1, 2 and 3 were characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction analysis. Crystal structures reveal that all the three similar interesting decanuclear clusters [Na2MnII2MnIII6] are derived from double trigonal bipyramid subunits bridged by mono-, di- and tri- fold azide groups, respectively. The magnetic susceptibility studies of 1, 2 and 3 in the temperature range 2–300 K shows that predominantly antiferromagnetic interactions between the manganese centers.

Binding of ligands containing carbonyl and phenol groups to iron(iii): new Fe6, Fe10 and Fe12 coordination clusters.

The initial use of ligands 2'-hydroxyacetophenone (HL1), 2-hydroxybenzophenone (HL2) and 2,2'-dihydroxybenzophenone (H2L3) in iron(iii) chemistry is described. The syntheses and crystal structures are reported for five iron(iii) clusters: [Fe10O4(OMe)14(L1)6(MeOH)2](NO3)2·3MeOH (1·3MeOH), [Fe12O4(OH)(OMe)17(L1)8](ClO4)2·2H2O (2·2H2O), [Fe10O4(OMe)14Cl4(L2)4(MeOH)2] (3), [Fe10O4(OMe)14(L2)6(py)2](ClO4)2·MeOH (4·MeOH), where py = pyridine, and [Fe6O2(OEt)6(O2CMe)2(L3)2(HL3)2] (5). The molecular structures of the decanuclear clusters 1, 3 and 4 are organized around a {Fe10(μ4-O)4(μ3-OMe)2(μ-OMe)12}8+ core consisting of ten {Fe3O4} face-sharing defective cubane units. The core of 2 consists of a {Fe12(μ4-O)4(μ3-OMe)4(μ-OH)(μ-OMe)13}10+ unit composed of twelve {Fe3O4} face-sharing defective cubanes. The ligands (L1)- and (L2)- in 1-4 adopt the O,O'-bidentate chelating coordination mode and their roles are to terminate the further aggregation of the FeIII/O2-/RO- cores. Complex 5 contains the {Fe6(μ4-O)2(μ-OEt)6(μ-Ocarbonyl)2}4+ core, where the μ-Ocarbonyl atoms are the bridging carbonyl oxygens of the two η1:η2:η1:μ (L3)2- ligands; the (HL3)- groups behave as Ophenolate, Ocarbonyl-bidentate chelating ligands with the neutral hydroxyl group being unbound to the FeIII atoms. The core is composed of four {Fe3O4} face-sharing defective cubanes. The FeIII atoms in 1-5 are all six-coordinate with distorted octahedral geometries. The IR spectra of the complexes are discussed in terms of the known coordination modes of the ligands and the ionic character of nitrates and perchlorates. Variable-temperature magnetic susceptibility and variable-field magnetization measurements establish that 2, 3 and 5 have S = 3, 0 and 5 ground states, respectively. The susceptibility data for 5 were fitted using a 3-J model indicating the simultaneous presence of both antiferromagnetic and ferromagnetic FeIIIFeIII exchange interactions. Known magnetostructural correlations in oxido-bridged iron(iii) systems have been applied to rationalise the magnetic behaviour of the three clusters. The results of the present study demonstrate the utility of HL1, HL2 and H2L3 in the stabilisation of robust iron(iii)/oxido/alkoxido clusters.

Thermodynamic-Driven Self-Assembly: Heterochiral Self-Sorting and Structural Reconfiguration in Gold(I)-Sulfido Cluster System.

By employing chiral precursors, a new class of chiral gold(I)-sulfido clusters with unique structures has been constructed. Interestingly, pure enantiomers of the precursors are found to self-assemble into chiral hexa- and decanuclear clusters sequentially, while a racemic mixture of them has resulted in heterochiral self-sorting of an achiral meso decanuclear cluster. Chirality has determined not only the symmetry and structures but also the photophysical behaviors of these clusters. The racemic mixture of decanuclear clusters undergoes rearrangement and heterochiral self-sorting to give a meso decanuclear cluster. The thermodynamic-driven heterochiral self-sorting of gold(I) clusters provides a means to develop controlled self-assembly that may be of relevance to the understanding of chirality in nature.

In situ tetrazole templated chair-like decanuclear azido-cobalt(II) SMM containing both tetra- and octa-hedral Co(II) ions.

An azido-bridged chair-like decanuclear cluster: [Co(II)10(bzp)8(Metz)2(N3)18]·4MeOH·3H2O (1, bzp = 2-benzoylpyridine and HMetz = 5-methyl-1H-tetrazole) was prepared with in situ tetrazolate anions as templates in a sealed system. 1 containing both octahedral and tetrahedral Co(II) ions exhibited slow relaxation of magnetization with an effective barrier of 26 K under an applied dc field of 1 kOe.

Unique Deca‐ and Tetranuclear Halocuprate(I) Clusters of a Clamplike Ligand: Isolation, Structure, and Luminescence Properties (Eur. J. Inorg. Chem. 5/2014)

The cover picture shows the structure of a decanuclear cluster [Cu10Cl10(L)4], where L is 3,7-di(3-pyridyl)-1,5-dioxa-3,7-diazacyclooctane, generated by diffusing the CH2Cl2 solution of L into the MeCN solution of CuCl. The two stairlike [Cu5Cl5] fragments share two μ6-Cl and two μ-Cl atoms to form a unique [Cu10Cl10] cluster framework. Details are discussed in the article by Z.-G. Ren, J.-P. Lang et al. on p. 824 ff. For more on the story behind the cover research, see the Cover Profile.

Unique Deca‐ and Tetranuclear Halocuprate(I) Clusters of a Clamplike Ligand: Isolation, Structure, and Luminescence Properties

AbstractThe reaction of 3‐aminopyridine with formaldehyde afforded a clamplike ligand, 3,7‐di(3‐pyridyl)‐1,5‐dioxa‐3,7‐diazacyclooctane (L). The diffusion of a CH2Cl2 solution of L into an MeCN solution of CuX produced one decanuclear cluster [Cu10Cl10(L)4] (1) and two tetranuclear clusters [Cu4X4(L)2(MeCN)2] [X = Br (2), I (3)]. Compound 1 possesses a unique [Cu10Cl10] cluster core consisting of two stairlike [Cu5Cl5] fragments that share two μ6‐Cl and two μ‐Cl atoms. Compounds 2 and 3 have a stairlike [Cu4X4] cluster core that is anchored by two L ligands. The trans configuration of the two pyridyl groups of the free L ligand was converted into the cis configuration of the two pyridyl groups of each bridging L ligand in 1–3. The photoluminescence properties of 1–3 in the solid state were also investigated.

Trinuclear, octanuclear and decanuclear dysprosium(III) complexes: Synthesis, structural and magnetic studies

Three new polynuclear dysprosium complexes have been synthesized and characterized via X-ray crystallographic and magnetic measurements. The crystallographic data revealed tri-, octa- and deca-nuclear clusters of formulae [DyIII3(OH)(teaH2)3(paa)3](Cl)2·MeCN·4H2O (1), [DyIII8(OH)6(teaH)6(teaH2)2(teaH3)2](O3SCF3)4·0.5MeOH·2H2O (2) and [DyIII10O2(OH)6(o-van)6(ISO)13(H2O)2](NO3) (3) using the bridging ligands triethanolamine (teaH3), N-(2-pyridyl)-acetoacetamide (paaH), o-vanillin (o-van) and isonicotinic acid (ISO). Compound 1 displays a triangular metallic core, while compound 2 reveals three fused butterfly motifs. Compound 3 displays two trigonal-prismatic units, which are bridged via a single isonicotinate ligand. Variable temperature dc magnetic susceptibility measurements reveal an overall decrease in the χMT (χM=molar magnetic susceptibility) product upon lowering the temperature for 1, 2 and 3, with ac magnetic measurements for 2 and 3 displaying peak ‘tails’ in the out-of-phase susceptibilities (χM″) below 8K, indicating single molecule magnet behavior.

A Heterometallic (NiII–CuII) Decanuclear Cluster Containing Two Distorted Cubane-like Pentanuclear Cores: Synthesis, Structure, and Magnetic Properties

A new heterometallic Ni(II)-Cu(II) decanuclear cluster, {[Ni(4)Cu(6)(μ-OH(2))(2)(dpkO(2))(8)(OAc)(4)(H(2)O)(4)]·2CH(3)OH·17H(2)O} (1), has been synthesized by self-assembly of the constituent metal ions and the precursor di-2-pyridylketone (dpk) of multinucleating ligand dpkO(2)(2-) and is structurally characterized. The cluster 1 is formed by the union of two symmetry-related distorted cubane-like pentanuclear cores. A magnetic study of 1 reveals strong antiferromagnetic interactions operating through the Ni-O-Ni pathway, which is independent of the assumption D = 0 or D ≠ 0. The pentanuclear cores are ferromagnetically coupled, as supported by density functional theory calculations.

A novel decanuclear Co(ii) cluster with adamantane-like metallic skeleton supported by 8-hydroxyquinoline and in situ formed CO32− anions

A novel decanuclear Co(II) cluster, [Co(10)(Q)(12)(μ(6)-CO(3))(4)]·2.5DMF (1) (Q = 8-hydroxyquinoline), has been synthesized under solvothermal conditions and characterized by powder XRD, TGA and IR spectroscopy. Single-crystal X-ray diffraction analysis shows that 1 represents a new type of decanuclear cobalt cluster with an approximate supertruncated tetrahedral shape coordinated with coexisted Q ligands and in situ formed μ(6)-bridging CO(3)(2-) anions. Meanwhile, 1 is the largest aggregate in metal-Q coordination chemistry. Another distinguishing feature of 1 is the adamantane-like metallic skeleton with point symbol {6(3)}(2){6}(3), which is observed in the polynuclear metal complexes for the first time. Furthermore, it is considered that the in situ formed CO(3)(2-) anions have a crucial effect on the formation of the resultant unexpected polynuclear structures. The magnetic studies show that antiferromagnetic (AF) interactions exist within 1.

Synthesis and characterization of homo- and heterovalent tetra- hexa- hepta- and decanuclear manganese clusters using pyridyl functionalized β-diketone, carboxylate and triethanolamine ligands

The syntheses and characterizations are reported for six new homo- and heterovalent manganese clusters, utilizing pyridyl functionalized beta-diketones ligands. The reaction of the trinuclear complex [Mn3O(O2CPh)6(H2O)(Py)2] with 1,3-di(pyridine-2-yl)propane-1,3-dione (dppdH) in CH2Cl2 resulted in a mixed-valence Mn3(II)Mn6(III)Mn(IV) decanuclear cluster of formula [Mn10O7(dppd)3(O2CPh)11] x 4 CH2Cl2 (1). The structure of the core of 1 is based upon a centred tricapped trigonal prism. Reacting Mn(BF4)2 x xH2O with dppdH and triethylamine (NEt3) in CH2Cl2-MeOH gave a rare, homoleptic hexanuclear cluster of formula [Mn(II)6(dppd)8][BF4]4 (2) which has a triangular based core. Reaction of Mn(Y)2 x xH2O, Y = NO3(-) or BF4(-), with dppdH or 1-phenyl-3-(2-pyridyl)propane-1,3-dione (pppdH) in the presence of triethanolamine (teaH3) and NEt3 gave a heptanuclear 'disc' like manganese core of general formula [Mn(II)7(X)6(tea)(OH)3][Y]2 x solv (3) X = pppd- or dppd- and Y = NO3(-) or BF4(-). The addition of N-(2-pyridinyl)acetoacetamide (paaH) to Mn(Y)2 x 4 H2O Y = NO3(-) or ClO4(-) in MeOH gave a second divalent heptanuclear cluster with a 'disc'-like core of general formula [Mn7(paa)6(OMe)6][X]2 x solv (4) (X = NO3(-) or ClO4(-)), whilst the addition of paaH to a mixture of Mn(NO3)2 x 4 H2O, teaH3 and NEt3 in CH2Cl2-MeOH resulted in the formation of a mixed-valence Mn2(II)Mn2(III) tetranuclear 'butterfly' complex of formula [Mn4(paa)4(teaH)2][NO3]2 x 2 MeOH x 2 CH2Cl2 (5). Compound 5 displays the rare Mn(II/III) oxidation state distribution of the body positions being Mn(II) while the wing tips are Mn(III). The in situ formation of the tetranuclear [Mn4(teaH)2(teaH2)2(O2C(CH3)3)2][O2C(CH3)3]2 'butterfly' complex followed by the addition of Mn(O2CMe)2 x 4 H2O resulted in a mixed-valence Mn4(II)Mn(III)Mn(IV) hexanuclear species of formula [Mn6O2(teaH2)4(O2CMe)4][NO3]2[O2CMe] x CH2Cl2 x MeOH x 2 H2O (6). The core of 6 displays a face sharing dicubane topology. Compounds 1 and 6 both display novel trapped-valence metal cores containing three different oxidation states on the manganese ion. Compounds 1, 2 and 3 are the first manganese based dppd clusters, while 4 and 5 are the first with the pyridylamino-substituted beta-diketone ligand (paaH). The magnetic data for 1, 2, 3, 4, and 6 are dominated by antiferromagnetic interactions within the clusters, leading to small ground spin values of S = 1 for 1, S = 3 for 2, S = 5/2 for 3, S = 5/2 for 4 and S = 1/2 for 6. Compound 5, however, displays overall ferromagnetic interactions with the data indicating an S = 6 ground state. 5 also exhibits probable single molecule magnet behaviour as indicated by frequency dependent out-of-phase chiM'' peaks in the AC susceptibility measurements.

Variation of Heterometallic Structural Motifs Based on [W(CN)8]3− Anions and MnII Ions as a Function of Synthetic Conditions

Reactions of [W(CN)(8)](3-/4-) anions with complexes of Mn(2+) ion with tridentate organic ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) lead to a series of heterobimetallic complexes. The crystal structures of these compounds are derived from the same basic structural fragment, namely a W(2)Mn(2) square constructed of alternating cyanide-bridged W and Mn ions. In [Mn(II)(tptz)(OAc)(H(2)O)(2)](2){[Mn(II)(tptz)(MeOH)(1.58)(H(2)O)(0.42)](2)[W(V)(CN)(8)](2)}.5 MeOH.9.85 H(2)O (3), isolated molecular squares are co-crystallized with mononuclear cationic Mn(II) complexes. The structure of {[Mn(II)(tptz)(MeOH)](2)[W(IV)(CN)(8)].2 MeOH}(infinity) (4) is based on an infinite chain of vertex-sharing squares, while {[Mn(II) (2)(tptz)(2)(MeOH)(3)(OAc)][W(V)(CN)(8)].3.5 MeOH0.25 H(2)O}(infinity) (5) and {[Mn(II) (2)(tptz)(2)(MeOH)(3)W(V)(CN)(8)][Mn(II)(tptz)(MeOH)W(V)(CN)(8)].2 H(2).OMeOH}(8) (7) are derived from such an infinite chain by removing one of the W-C[triple bond]N-Mn linkages in each of the squares. The decanuclear cluster [Mn(II) (6)(tptz)(6)(MeOH)(4)(DMF)(2)W(V) (4)(CN)(32)].8.2 H(2)O.2.3 MeOH (6) is a truncated version of structure 4 and consists of three vertex-sharing W(2)Mn(2) squares. The structure of [Mn(II)(tptz)(MeOH)(NO(3))](2)[Mn(II)(tptz)(MeOH) (DMF)](2)[W(V)(CN)(8)](2).6 MeOH (8) consists of a hexanuclear cluster, in which the central W(2)Mn(2) square is extended by two Mn side-arms attached via CN(-) ligands to the W corners of the square. The magnetic behavior of these heterobimetallic complexes (except for 4) is dominated by antiferromagnetic coupling between Mn(II) and W(V) ions mediated by cyanide bridges. Compounds 3, 6, and 8 exhibit high spin ground states of S=4, 13, and 9, respectively, while 5 and 7 exhibit behavior typical of a ferrimagnetic chain with alternating spin centers. Complex 4 contains diamagnetic W(IV) centers but holds promise as a potential photomagnetic solid.

Methanolysis as a Route to Gallium(III) Clusters: Synthesis and Structural Characterization of a Decanuclear Molecular Wheel

Treatment of a methanolic solution of gallium(III) nitrate with lithium hydroxide in the presence of benzilic acid resulted in the decanuclear cluster [Ga(OMe)2{O2CC(OH)Ph2}]10 (1). The metal and the organic components have assembled to form a cyclic molecule that adopts the structure of a wheel. The 10 Ga(III) ions are approximately coplanar and are coordinated in a distorted octahedral manner by six oxygen atoms. The integrity of the molecular wheel is retained in solution, as evidenced by the 1NMR spectrum of 1 in DMSO-d6, while no signal in the 71Ga NMR could be detected.

A simple method for the preparation of octanuclear tin (IV) oxosulfide cluster and the conversion of it to decanuclear cluster

An octanuclear tin (IV) complex [( n-C 4H 9) 4N] 4 [Sn 8(μ 4-O) 2(μ 2-OH) 2S 12Cl 6] 1 was synthesized simply by the reaction of Na 2S·7H 2O and SnCl 4·5H 2O in DMF. The yield is high and this may provide a new strategy for the preparation of other octanuclear tin (IV) oxosulfide cluster. When 1 was heated under hydrothermal conditions, a decanuclear cluster [( n-C 4H 9) 4N] 4 [Sn 10(μ 4-O) 4(μ 3-S) 4(μ 2-S) 12Cl 4]·(4,4 ′-bipy) 2 may be obtained. The two clusters were all characterized by X-ray structure analysis.

Reactivity of the mixed-metal cluster [Os 6(CO) 17(Au 2dppm)] towards gold electrophiles (dppm=Ph 2PCH 2PPh 2)

Reduction of the mixed-metal octanuclear cluster [Os 6(CO) 17(Au 2dppm)] ( 1) with Na–Hg amalgam and subsequent reaction with one equivalent of [Au 2dppm][NO 3] affords two isomers of the neutral decanuclear cluster [Os 6(CO) 17(Au 2dppm) 2] ( 2a, 2b). In a similar reaction between the reduced form of 1 with two equivalents of [AuPPh 3][NO 3] gives two isomers of the related cluster [Os 6(CO) 17(Au 2dppm 2)(AuPPh 3) 2] ( 3a, 3b). All the new clusters have been characterised by IR and NMR spectroscopy and FAB mass spectrometry. The molecular and crystal structure of 2a has been established by a single-crystal X-ray structure. In 2a the six Os atoms define an octahedron, in contrast to the bicapped tetrahedral osmium core previously observed for 1. Two of the Au atoms in 2a cap adjacent triangular faces of the Os 6 octahedron while the third spans an open OsAu 2 triangle, and the fourth caps a closed OsAu 2 triangle. Overall the decametal core may be viewed as an octahedron fused with a capped square based pyramid.

Systematic formation of mixed-metal high-nuclearity clusters: the synthesis and characterisation of [Os 6(CO) 17(Au 2dppm)] and [Os 6(CO) 17(Au 2dppm){Ru(η 5-C 5H 5)} 2] (dppm=Ph 2PCH 2PPh 2)

Reaction of the hexaosmium cluster [Os 6(CO) 18] with 1.1 equivalents of Me 3NO, in CH 2Cl 2, in the presence of one equivalent of [Au 2dppm]Cl 2 (dppm=Ph 2PCH 2PPh 2), at room temperature, affords the new mixed-metal cluster [Os 6(CO) 17(Au 2dppm)] ( 1), in high yield. Subsequent reduction of 1 with Na–Hg amalgam, and subsequent treatment with [Ru(η 5-C 5H 5)(MeCN) 3][PF 6] ( 2) afforded two decanuclear clusters [Os 6(CO) 17(Au 2dppm){Ru(η 5-C 5H 5)} 2] ( 3) and [Os 6(CO) 16(Au 2dppm){Ru(η 5-C 5H 5)} 2] ( 4) in moderate yield. Cluster 3 loses CO under reflux in toluene to produce 4. The new clusters have been fully characterised by IR, 1H- and 31P-NMR spectroscopies, and mass spectrometry. The molecular and crystal structures of 1 and 3 have been established by single-crystal X-ray analyses. In 1, the bicapped tetrahedral osmium core of [Os 6(CO) 18] is retained and the two Au atoms of the Au 2dppm group cap one Os 3 face in a μ 3-η 2 bonding mode. In 3 the metal core consists of a capped square-based pyramidal arrangement of Os atoms that is capped over the square face by the Au 2dppm group. One Ru atom caps another face of the Os 5 square-based pyramid, and the second Ru atom caps the Ru atom, two Os atoms and an Au atom to form a trigonal bipyramidal arrangement.

Synthesis and characterization of high-nuclearity iridium–ruthenium and –gold mixed-metal carbonyl clusters, [Ir7Ru3(CO)23]−, [Ir7Ru3(CO)23(AuPPh3)] and [Ir6Ru3(CO)21(AuPPh3)]−, possessing tetrahedrally capped octahedral iridium cores obtained by capping reactions with [Ru3(CO)12] and [AuCl(PPh3)

The new carbonyl cluster [PPh4][Ir7Ru3(CO)23] 1 has been obtained by the high yield reaction of [PPh4]2[Ir6(CO)15] with [Ru3(CO)12] in the presence of p-toluenesulfonic acid. The monoanionic decanuclear cluster 1 has an octahedral arrangement of the iridium atoms with three ruthenium atoms and an iridium atom tetrahedrally capping four triangular faces. Two terminal CO ligands are bound to each iridium atom and three to each ruthenium atom. In this synthesis p-toluenesulfonic acid served as a degradation reagent for [Ir6(CO)15]2− to generate the capping {Ir(CO)2}+ moiety. Reaction of 1 with [AuCl(PPh3)] in the presence of AgOSO2CF3 at ambient temperature yielded the undecanuclear neutral cluster [Ir7Ru3(CO)23(AuPPh3)] 2. The {AuPPh3}+ group co-ordinates to the apical iridium atom of the parent metal carbonyl monoanion 1 maintaining the cluster framework as well as the stereogeometry of the CO ligands. Thermal treatment of 1 with [AuCl(PPh3)] in refluxing 1,2-dichloroethane caused substitution of the capping {Ir(CO)2}+ group in 1 with an isolobal {AuPPh3}+ group, resulting in the formation of decanuclear monoanionic cluster [PPh4][Ir6Ru3(CO)21(AuPPh3)] 3.

In Situ FTIR Spectroscopy Studies on Electrochemical Redox Processes of High Nuclearity Osmium Carbonyl Clusters

The electrochemical redox processes of two high nuclearity osmium carbonyl clusters [(Ph3P)2N]2[Os10C(CO)24]·PPN2 (1) and Os6(CO)18 (6) have been studied by electrochemical in situ FTIR. The five oxidation states of 1, i.e., [Os10C(CO)24]0/1-/2-/3-/4-, have been characterized. There are no significant structural changes for these species. Hence, the ability of this decanuclear cluster to act as an electron reservoir has been demonstrated. The structural rearrangement associated with the two-electron reduction of bicapped tetrahedral 6 to octahedral dianion [Os6(CO)18]2- and [Os6(CO)18]4- tetraanion has also been investigated.