Octahedral Core Research Articles

Synthesis and skeletal isomerization of the phosphinidene acetylide cluster complexes [Ru4(CO)10(μ4-PPh)(CCPh){WL(CO)}] where L = C5Me5 or C5H5

Reactions of the phosphinidene cluster [Ru4(CO)13(µ3-PPh)] with tungsten acetylide complexes [WL(CO)3(CCPh)] (L = C5Me5 or C5H5) gave interconvertible isomers of formula [Ru4(CO)10(µ4-PPh)(CCPh){WL(CO)}]. The structures of the two C5Me5 derivatives were determined by X-ray diffraction, showing a novel WRu4P octahedral core arrangement, in which the acetylide ligand is co-ordinated to a WRu2 triangle with its C–C vector bridging the Ru–Ru edge. For one isomer the phosphinidene ligand is located at the position trans to the W atom, while in the second isomer it is at the cis position. Possible mechanisms for this rare example of skeletal isomerization are suggested.

Syntheses and structural characterizations of the octahedral boride clusters [Rh2Ru4H(CO)16−2x (nbd) x B] (x=1,2) and gold(I) phosphine derivatives (nbd=norbornadiene)

The reaction of less than one equivalent of [Rh2Cl2(nbd)2] with [Ru4H(CO)12BH]−, which contains a semi-interstitial boron atom, yields the heterometallic boride clustercis-[Rh2Ru4H(CO)12(nbd)2B] which has been characterized by spectroscopic and X-ray diffraction methods. The cluster has an octahedral core, consistent with an 86 electron count. Deprotonation yields the conjugate basecis-[Rh2Ru4(CO)12(nbd)2B]− which has been isolated and fully characterized as the [(Ph3P)2N]+ salt. There is little structural perturbation upon going fromcis-[Rh2Ru4H(CO)12(nbd)2B] tocis-[Rh2Ru4(CO)12(nbd)2B]− and neither cluster shows a tendency for the formation of thetrans skeletal isomer in contrast to the analogous carbonyl clustercis-[Rh2Ru4(CO)16B]−. If the reaction of [Rh2Cl2(nbd)2] with [Ru4H(CO)12BH]− is allowed to proceed for 30 min and [R 3PAuCl] (R=Ph, C6H11, 2-MeC6H4) is then added, the clusterscis-[Rh2Ru4(CO)12(nbd)2B(AuPR3)] andcis-[Rh2Ru4(CO)14(nbd)B(AuPR3)] are formed in yields that are dependent upon the initial reaction period. The single crystal structures ofcis-[Rh2Ru4(CO)12(nbd)2B(AuPPh3)] andcis-[Rh2Ru4(CO)14(nbd)B(AuPPh3)] are reported. In contrast to their all-carbonyl analoguescis-[Rh2Ru4(CO)16B(AuPR 3)] (R=Ph or C6H11), the nbd derivatives do not undergocis →trans skeletal isomerism.

Trans-[(Mo6Cl8)(C7H7)4{P(n-C4H9)3}2] andtrans-[(Mo6Cl8)(C8H5)4{P(n-C5H11)3}2].2C7H8

The title compounds, tetrabenzyl-2κC,3κC,4κC,5κC-octa-μ3-chloro-bis(tributylphosphine)-1κP,6κP-octahedro-hexamolybdenum(12Mo—Mo), (1) and tetrakis(phenylethynyl)-2κC,3κC,4κC,5κC-octa-μ3-chloro-bis(tripentylphosphine)-1κP,6κP-octahedro-hexamolybdenum(12Mo—Mo)-toluene (1/2), (2), containing octahedral Mo clusters with four σ-C ligands, were prepared by the reaction of trans-[(Mo6Cl8)Cl4(PR3)2] with tribenzylaluminium and tris(phenylethynyl)aluminium, respectively, and their structures determined. The octahedral Mo6 cores of both compounds are on inversion centres and are almost regular. Average interatomic distances in the clusters for (1) are Mo—Mo(edge) = 2.618, Mo⋯Mo(opposite) = 3.703, Mo—Cl = 2.477 and Mo—C = 2.26 Å, and for (2) are Mo—Mo(edge) = 2.626, Mo⋯Mo(opposite) = 3.714 and Mo—C = 2.13 Å.

Preparation and thermolysis of complexes derived from some trinuclear ruthenium clusters and 1,4-diphenylbuta-1,3-diyne

Reactions between Ru3(μ-dppm)(CO)10 and PhCȦCCȦCPh in thf, in the presence of Me3NO, afford the complexes Ru3(μ3-PhC2CȦCPh)(μ-dppm)(μ-CO)(CO)7 (1) and Ru3(μ-dppm)μ-C4Ph2(CȦCPh)2(CO)6 (2). Complex 1 was also obtained from Ru3(μ3-PhC2CȦCPh)(μ-CO)(CO)9 (3) and dppm in thf on heating. Two of the complexes formed by thermolysis of 1 in xylene at 130°C were identified crystallographically as Ru3μ3-CPhCHCC(C6H4-2)(μ-dppm)(CO)8 (4) and Ru3μ3-C4H2Ph2(μCO)(CO)5(dppm) (5). In 4, fragmentation of the cluster and metallation of one of the diyne phenyl groups took place; the dppm ligand bridges two non-bonded Ru atoms. In 5, partial hydrogenation of the diyne has occurred to give a 2η1:η4:η4-butadiendiyl ligand, the dppm ligand adopting a chelating mode on one of the two Ru atoms which is η4 attached to the hydrocarbon. In comparison, thermolysis of 3 gave Ru4(μ4-PhC2CȦCPh)(CO)n(n = 12 (6) and 14 (7)). The former has a distorted C2Ru4 octahedral core, while in the latter the Ru3 cluster has fragmented to give a ruthenacyclopentadiene derivative in which the central C-C bond bridges an Ru2(CO)8 group.

Electron-Transfer-Coupled Ligand Dynamics in CuI/II(TTCN)2Complexes in Aqueous Solution

One-electron oxidation of copper(I) bis(1,4,7-trithiacyclononane), [CuI(TTCN-κ3)(TTCN-κ1)]+, 1, a coordination complex with a tetrahedral CuS4 core, to [CuII(TTCN-κ3)2]2+, 2, with an octahedral CuS6 core, has been studied by pulse radiolysis and electrochemistry in aqueous solution at various pH values. In addition to the geometry change about the metal ion in this oxidation, the nonchelating 1,4,7-trithiacyclononane (TTCN) ligand in 1 changes conformation on becoming chelated in 2. However, pulse radiolysis reveals that this process does not occur intramolecularly but affords a bimolecular reaction in which the oxidized copper incorporates an external TTCN. Evidence for this mechanism is drawn from corresponding experiments with a variety of related CuI complexes in which the monodentate TTCN has been replaced by other sulfur-containing ligands and which have been structurally characterized by X-ray crystallography. From all these studies it is concluded that oxidation of 1 and all these other complexes of CuI is accompanied by immediate loss of the monodentate ligand generating [CuII(TTCN-κ3)(H2O)3]2+, 3. Transient 3 is characterized by an optical absorption with λmax = 370 nm and ε ∼ 2000 M-1 cm-1 which depends on pH because this transient participates in three acid/base equilibria. Deprotonation of the three water ligands associated with Cu(II) results in increasingly blue-shifted absorptions. Undeprotonated transient 3 prevails at pH ≤6, and converts directly into the stable CuII complex 2 via reaction with an unoxidized molecule of 1 or free TTCN. The corresponding bimolecular rate constants are 5.2 (±0.5) × 105 and 8.4 (±1.0) × 105 M-1 s-1, respectively. For the deprotonated forms of 3 this process is increasingly slowed down and at higher pH (≥9) the formation of 2 is completely prevented. The formation of transient 3 is also consistent with the pH dependence of the electrochemistry of 1. Under electrochemical conditions the conversion into 2 follows first-order kinetics due to a relatively high TTCN concentration available near the electrode surface after oxidation of 1. All the results require rapid ligand exchange in 1 and a particularly labile monodentate TTCN ligand. This has been corroborated by 1H NMR spectroscopic studies on 1.

Reactivity of [SeFe3(CO)9]2- with Electrophiles: Formation of [SeFe2Ru3(CO)14]2-, [SeFe3(CO)9(μ-HgI)]-, Fe2(CO)6(μ-SeCHPhSe), and Se2Fe2(CO)6(μ-CH2)2

The reactions of the tetrahedral cluster [SeFe3(CO)9]2- with some transition-metal complexes and organic halides were investigated. The mixed-metal cluster [Et4N]2[SeFe2Ru3(CO)14] (1) was obtained from the reaction of [Et4N]2[SeFe3(CO)9] with Ru3(CO)12 in acetone. Further reaction of [Et4N]2[SeFe3(CO)9] with HgI2 produces the HgI-bridged cluster [Et4N][SeFe3(CO)9(μ-HgI)] (2). While [SeFe3(CO)9]2- reacts with CHPhCl2 to produce the CHPh-bridged cluster Fe2(CO)6(μ-SeCHPhSe) (3), treatment with CH2I2 forms the major product Se2Fe2(CO)6(μ-CH2)2 (4). Complex 1 displays an octahedral metal core with a μ4-Se atom and two carbonyl groups bridging the Ru−Ru and Ru−Fe bonds. Cluster 2 consists of a SeFe3 core with a HgI fragment bridging one Fe−Fe bond, and cluster 3 exhibits a Se2Fe2 butterfly geometry with the wingtip linked by a CHPh moiety. On the other hand, cluster 4 contains a planar Se2Fe2 moiety with two CH2 groups bridging the two Se−Fe bonds. Complexes 1−4 have been fully structurally characterized by sp...

Synthesis and characterisation of the hexanuclear ruthenium diphosphine clusters [Ru6C(CO)15{μ-Ph2P(CH2 )nPPh2}] (n = 1–4); crystal structures where n = 1–3

Treatment of a hexane solution of the complex [Ru 6 C(CO) 17 ] and 1 equivalent of the organodiphosphine ligands Ph 2 P(CH 2 ) n PPh 2 (n = 1–3) produced the series of derivatives [Ru 6 C(CO) 15 {µ-Ph 2 P(CH 2 ) n PPh 2 }] 1–3, respectively, in ca. 74–94% yield. These clusters have been characterised by IR and NMR spectroscopy and in the solid state by X-ray analyses. The three related compounds all adopt a similar octahedral metal core geometry with the bidentate diphosphine ligand bridging one Ru–Ru edge of the metal polyhedron. Reaction of [Ru 6 C(CO) 17 ] with 1,4-bis(diphenylphosphine)butane, Ph 2 P(CH 2 ) 4 PPh 2 , yielded two products which differ in the mode of bonding of the disphospine ligand, the major product [Ru 6 C(CO) 16 {Ph 2 P(CH 2 ) 4 PPh 2 -P}] 4a in ca. 74% yield and the minor product [Ru 6 C(CO) 15 {µ-Ph 2 P(CH 2 ) 4 PPh 2 }] 4b in ca. 10% yield.

The Crystal and Molecular Structure of [Co(tmen)3](C7H7SO3)3·2 H2O and [Co(tmen)3](CH3SO3)2·EtOH·1/2 H2O (tmen = 2,3-dimethylbutane-2,3-diamine)

The molecular structure of the two complex ions [Co(tmen)3]3+ and [Co(tmen)3]2+ (tmen = 2,3-dimethylbutane-2,3-diamine) have been determined at 100 K. They show a strong trigonal distortion of the octahedral CoN6 core. The twist angle is 26.2(2.8)° for CoII and 43.9(9)° for CoIII. Average CoN distances are 2.193(13) A (CoII) and 1.997(2) A (CoIII), 0.02 A longer than for the main body of CoIII amines.

Silver(I)-dithiolate chemistry: Syntheses and characterizations of three new Ag1 cluster anions containingi-MNT [i-MNT= S2CC(CN) in2 su2− ] ligands-[Ag4(i-MNT)4]4−, [Ag8(i-MNT)6(PPh3)4]4−, and [Ag9(i-MNT)6(PPh3)6]3−

The reaction of AgNO3 with [(“Bu4N2i-MNT)]3 in CH3CN produces a new silver cluster anion [Ag4(i-MNT)4]4− ,3, a species having a tetrahedral arrangement of silver atoms bridged by fouri-MNT ligands which has been isolated and characterized by X-ray crystallography as [Bu4N]2[(PPh3)2]2 [Ag4(i-MNT)4],4. The reaction of two or three equivalents of Ag(PPh3)2NO3 with [BzEt3N]6[Ag6(i-MNT)6] in CH3CN produces two new clusters, [BzEt3N]4[Ag8(i-MNT)6(PPh3)4],6, and [BzEt3N]3[Ag4(i-MNT)6(PPh3)6], 7, having the common structural feature of an octahedral Ag6S12 core. The octanuclear Ag8 cluster also can be synthesized from the reaction of 4 and PPh3 in CH2Ck2 and compound 5 has been structurally characterized as [Bu4N]2[(PPh3)2N]2[Ag8(i-MNT)6(PPh3)4]. The31P{1H} NMR spectrum of 6 in CD3CN at −43° shows two sets of two doublets. The corresponding chemical shift and coupling constant of each species is 9.32 ppm (354, 408.8 Hz) and 9.45 ppm (346.7, 401.7 Hz), respectively. Pertinent crystallographic data are as follows: Compound 4 crystallizes in the orthorhombic space group Cc2a, witha=18.668(3)A,b=36.793(4) A,c=17.836(3)A, Z=4, andV= 12250(3)A3. Compound 5 crystallizes in the triclinic space group P1, witha=16.506(3)A,b=17.280(3)A,c=19.144(4) A,x=98.485(14)°, β= 105.44(2)°.y=94.63(2),Z= 1, andV = 5164(2)A3. Compound6 crystallizes in the monoclinic space group C2/m, witha= 25.341(9)A,b= 25.289(9)A,c= 15.076(7)A, β= 107.19(5)°,Z=2, and V=9230(6)A3. Compound7 crystallizes in the monoclinic space group C2/c, witha=25.872(6)A,b=21.288(4) A,c=35,928(5), β=100.98(1)°,Z-4, andV=19426(6)A3.

Synthesis, Structure, and Electrochemistry of a Dodecanuclear Chromium Cluster Complex [Cr12S16(PEt3)10

Abstract A dodecanuclear chromium sulfide cluster complex [Cr12S16(PEt3)10] has been synthesized by the reaction of a hexanuclear cluster complex [Cr6S8(PEt3)6] with sulfur. This complex has two octahedral Cr6S8 cores that are linked by two Cr-S bonds. The intercluster bonding mode is similar to that in the Chevrel phases. Cyclic voltammetry shows the existence of the intercluster electronic interaction between the two Cr6S8 cluster units.

(2,9-Dimethyl-1,10-phenanthroline-N1,N10)bis(O-ethyl dithiocarbonato-S,S')nickel(II)

The crystal structure of [Ni(C2H5OCS2)2(C14H12N2)] cis- [Ni(EtXA)2(2,9-dmphen)] (EtXA = ethyl xanthate, 2,9-dmphen = 2,9-dimethyl-1,10-phenanthroline), containing a distorted octahedral NiS4N2 core, is reported. The Ni—S bond lengths range from 2.376 (2) to 2.522 (2) A and the Ni—N bond lengths are 2.107 (4) and 2.153 (3) A, while the N(1)—Ni—N(2) chelate angle is 78.3 (1)°.

Protein–protein interactions in the pyruvate dehydrogenase multienzyme complex: dihydrolipoamide dehydrogenase complexed with the binding domain of dihydrolipoamide acetyltransferase

Background: The ubiquitous pyruvate dehydrogenase multienzyme complex is built around an octahedral or icosahedral core of dihydrolipoamide acetyltransferase (E2) chains, to which multiple copies of pyruvate decarboxylase (E1) and dihydrolipoamide dehydrogenase (E3) bind tightly but non-covalently. E2 is a flexible multidomain protein that mediates interactions with E1 and E3 through a remarkably small binding domain (E2BD). Results In the Bacillus stearothermophilus complex, the E2 core is an icosahedral assembly of 60 E2 chains. The crystal structure of the E3 dimer (101 kDa) complexed with E2BD (4 kDa) has been solved to 2.6 å resolution. Interactions between E3 and E2BD are dominated by an electrostatic zipper formed by Arg135 and Arg139 in the N-terminal helix of E2BD and Asp344 and Glu431 of one of the monomers of E3. E2BD interacts with both E3 monomers, but the binding site is located close to the twofold axis. Thus, in agreement with earlier biochemical results, it is impossible for two molecules of E2BD to bind simultaneously to one E3 dimer. Conclusion Combining this new structure for the E3–E2BD complex with previously determined structures of the E2 catalytic domain and the E2 lipoyl domain creates a model of the E2 core showing how the lipoyl domain can move between the active sites of E2 and E3 in the multienzyme complex.

Synthesis, Characterization, and Comparative Properties of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)

The reaction of [PPN](2)[Re(6)C(CO)(19)] with Mo(CO)(6) and Ru(3)(CO)(12) under sunlamp irradiation provided the new mixed-metal clusters [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)], which were isolated in yields of 85% and 61%, respectively. The compound [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] crystallizes in the monoclinic space group P2(1)/c with a = 20.190 (7) Å, b = 16.489 (7) Å, c = 27.778 (7) Å, beta = 101.48 (2) degrees, and Z = 4 (at T = -75 degrees C). The cluster anion is composed of a Re(6)C octahedral core with a face capped by a Mo(CO)(4) fragment. There are three terminal carbonyl ligands coordinated to each rhenium atom. The four carbonyl ligands on the molybdenum center are essentially terminal, with one pair of carbonyl ligands (C72-O72 and C74-O74) subtending a relatively large angle at molybdenum (C72-Mo-C74 = 147.2(9) degrees ), whereas the remaining pair of carbonyl ligands (C71-O71 and C73-O73) subtend a much smaller angle (C71-Mo-C73 = 100.5(9) degrees ). The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows signals for four sets of carbonyl ligands at -40 degrees C, consistent with the solid state structure, but the carbonyl ligands undergo complete scrambling at ambient temperature. The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] at 20 degrees C is consistent with the expected structure of an octahedral Re(6)C(CO)(18) core capped by a Ru(CO)(3) fragment. The visible spectrum of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows a broad, strong band at 670 nm (epsilon = 8100), whereas all of the absorptions of [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] are at higher energy. An irreversible oxidation wave with E(p) at 0.34 V is observed for [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)], whereas two quasi-reversible oxidation waves with E(1/2) values of 0.21 and 0.61 V (vs Ag/AgCl) are observed for [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)]. The molybdenum cap in [Re(6)C(CO)(18)Mo(CO(4))](2-) is cleaved by heating in donor solvents, and by treatment with H(2), to give largely [H(2)Re(6)C(CO)(18)](2-). In contrast, [Re(6)C(CO)(18)Ru(CO)(3)](2-) shows no tendency to react under similar conditions.

Tris(O,O'-dicyclohexyl dithiophosphato-S,S')chromium(III)

The title complex, [Cr{S 2 P(OC 6 H 11 ) 2 } 3 ], contains a CrS 6 distorted octahedral core, in which the Cr-S bond lengths range from 2.423(2) to 2.439(2)A and the S-Cr-S bidentate angles range from 81.39(6) to 81.66(7)°.

Hexamolybdenum Cluster with One Telluride and Seven Chloride Capping Ligands

Tetraethylammonium hepta-μ 3 -chloro-μ 3 -telluro-hexachlorohexamolybdate, (Et 4 N) 3 [(Mo 6 Cl 7 Te)Cl 6 ], has an octahedral hexamolybdenum cluster core whose faces are capped by seven Cl atoms and one Te atom. The capping telluride is disordered in the crystal. The average Mo-Mo distance is not much different from those in [(Mo 6 Cl 7 Z)Cl 6 ] 3- (Z = S, Se).

C4-ring ligand-transfer reactions: applications to cluster chemistry. Crystal structures of [Ru5C(CO)13(η-C4Ph4)] and [Ru6C(CO)15(η-C4Ph4)

Redox-mediated ligand-transfer reactions between the cationic complex [Pd(η-C4Ph4)(Me2CO)2]2+ and the dianionic clusters, [Ru5C(CO)14]2– and [Ru6C(CO)16]2– afforded [Ru5C(CO)13(η-C4Ph4)]1 and [Ru6C(CO)15(η-C4Ph4)]2, respectively. The new clusters 1 and 2 have been characterised by spectroscopic techniques in solution and in the solid-state by single-crystal X-ray diffraction. In 1 the ring is co-ordinated to a basal ruthenium atom of the square-pyramidal cluster framework, while in 2 the octahedral metal core of the parent complex has opened slightly through the elongation of one Ru–Ru bond. The reasons for this structureal change have been analysed using extended-Huckel molecular-orbital calculations.

Growth of lithium borate crystals from the vitreous state

The morphology and the growth mechanism of lithium borate crystals from the vitreous state have been studied for various compositions, X = B/(Li + B), from 0.62 to 0.75. Crystalline phases and morphology of grown crystals varied with the composition. Octahedral and/or spherical Li2B4O7 crystals are seen in the specimen with X = 0.62, 0.64, 0.67, and 0.68. The spherical crystal is composed of an octahedral core and fibrous crystals. The size of the core varied with the composition of the starting glass, X. The fibrous crystal growth is supposed to arise from the morphological instability due to the compositional variation caused by the solute pileup at the growth interface.

Synthesis and crystal structure of homoleptic uranium hexathiolates: [NEt2H2]2[U(SPh)6] and [(Ph3P)Cu(µ-SPh)3-U(µ-SPh)3Cu(PPh3)

Treatment of U(NEt2)4 with PhSH gave [NEt2H2]2[U(SPh)6]1, Reaction of UCl4 with NaSPh in the presence of CuSPh and PPh3 afforded [(Ph3P)Cu(µ-SPh)3U(µ-SPh)3Cu(PPh3)]2. The geometrical parameters of the octahedral US6 core are quite similar in the crystal structures of 1, 2·6thf and [(thf)3Na(µ-SPh)3U(µ-SPh)3Na(thf)3](thf = tetrahydrofuran). The U–Cu distance of 3.05(1)A supports the presence of a direct metal–metal interaction.

Synthesis, molecular and electronic structure of complexes [LNaMIVNaL](MRu,Os; H3L = 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane)

The trinuclear complexes [LNaMIVNaL](M = Ru 1, Os 2) where L represents the hexadentate ligand 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane have been synthesized and 1 has been characterized by X-ray crystallography; complex 1 contains an octahedral MIVS6 central core and two trigonal-prismatic terminal LNa units with an N3S3 donor set; the electronic structure of the MIVS6 core (M = Ru, Os), has been established as S= 1 by temperature-dependent magnetic susceptibility measurements.

Delton communications. Synthesis and characterization of a palladium–osmium mixed-metal cluster; crystal structure of [Os6Pd(CO)18(bipy)]·CHCl3(bipy = 2,2′-bipyridine)

The heterometallic cluster [Os6Pd(CO)18(bipy)](bipy = 2,2′-bipyridine) has been isolated in moderate yield from the reaction of [Os3(CO)10(MeCN)2] and [Pd(bipy)(CO2Me)2], and shown by a single-crystal X-ray structure analysis to contain a monocapped octahedral metal core with the palladium occupying one vertex of the octahedron.