Jacky Rosé

Synthesis of Co2Pt, Co2Pd and MoPd2 mixed-metal clusters with the P–N–P assembling ligands (Ph2P)2NH (dppa) and (Ph2P)2NMe (dppaMe). Crystal structure of [Co2Pt(μ3-CO)(CO)6(μ-dppa)]

Heterometallic triangular platinum–cobalt, palladium–cobalt and palladium–molybdenum clusters stabilized by one or two bridging diphosphine ligands such as Ph2PNHPPh2 (dppa) or (Ph2P)2NMe (dppaMe) or by mixed ligand sets Ph2PCH2PPh2 (dppm)/dppa have been prepared with the objectives of comparing the stability and properties of the clusters as a function of the short-bite diphosphine ligand used and of the metal carbonyl fragment they contain. Ligand redistribution reactions were observed during the purification of [Co2Pd(μ3-CO)(CO)4(μ-dppa)(μ-dppm)] (4) by column chromatography with the formation of [Co2Pd(μ3-CO)(CO)4(μ-dppm)2] and the dinuclear complex [(OC)2Cl] (5). The latter was independently prepared by reaction of [Pd(dppa-P,P′)2](BF4)2 with Na[Co(CO)4]. Attempts to directly incorporate the ligand (Ph2P)2N(CH2)3Si(OMe)3 (dppaSi) into a cluster or to generate it by N-functionalization of coordinated dppa were unsuccessful, in contrast to results obtained recently with related clusters. The crystal structure of [Co2Pt(μ3-CO)(CO)6(μ-dppa)] (1) has been determined by X-ray diffraction.

Synthesis and structure of the mixed-metal ruthenium-cobalt alkyne clusters NEt4[RuCo3(μ-CO)2(CO)8(μ4-η2-PhCCPh)] and RuCo2(CO)9(μ3-η2-PhCCPh)

Abstract The tetrahedral cluster NEt4[RuCo3(CO)12] was prepared in 90% yield, and on treatment with excess PhCCPh gave the “butterfly” cluster NEt4[RuCo3(μ-CO)2(CO)8(μ4-η2-PhCCPh)]. Reaction of the latter with HCl gave the neutral trimetallic cluster RuCo2(CO)9(μ3-η2-PhCCPh). Both products were characterized by single-crystal X-ray diffraction studies.

On the nature of metallic nanoparticles obtained from molecular Co3Ru–carbonyl clusters in mesoporous silica matrices

We report on the impregnation of THF solutions of the low-valent heterometallic cluster NEt(4)[Co(3)Ru(CO)(12)] into two mesoporous silica matrices, amorphous xerogels and ordered MCM-41, and a study of its thermal decomposition into metallic nanoparticles by X-ray diffraction, transmission electron microscopy and in situ magnetic measurements under controlled atmospheres. The decomposition of the cluster was monitored as a function of temperature by examining the chemical composition of the particles, their size distributions and their structures as well as their magnetic properties. Treatment under inert atmosphere (i.e. argon) at temperatures below 200 degrees C resulted in the formation of segregated spherical particles of hcp-ruthenium (2.3 +/- 1.0 nm) and hcp-cobalt (3.1 +/- 0.9 nm). The latter is transformed to fcc-cobalt (3.2 +/- 1.0 nm) above 270 degrees C. At higher temperatures, Co-Ru alloying takes place and the Ru content of the particles increases with increasing temperature to reach the nominal composition of the molecular precursor, Co(3)Ru. The particles are more evenly distributed in the MCM-41 framework compared to the disordered xerogel and also show a narrower size distribution. Owing to the different magnetic anisotropy of hcp- and fcc-cobalt, which results in different blocking temperatures, we were able to clearly identify the products formed at the early stages of the thermal decomposition procedure.

Syntheses, structures, and bonding of heteropentametallic clusters [MCo3(CO)12{µ3-M′(EPh3)}](M = Fe or Ru; M′= Cu or Au; E = P or As): X-ray crystal structures of [RuCo3(CO)12{µ3-M′(PPh3)}](M′= Cu or Au)

The cluster anions [MCo3(CO)12]–[M = Fe (1) or Ru (2)] react with [{Cu(PPh3)Cl}4] in toluene to give the neutral pentametallic clusters [FeCo3(CO)12{µ3-Cu(PPh3)}](3) and [RuCo3(CO)12{µ3-Cu(PPh3)}](4). The latter two products react with PPh3 to give the ionic cluster species [Cu(PPh3)3][MCo3(CO)12]. The pentametallic cluster [RuCo3(CO)12{µ3-Au(PPh3)}](5), obtained by reaction of (2) with Au(PPh3)Cl in diethyl ether-toluene, also reacts with PPh3 to give [Au(PPh3)2][RuCo3(CO)12]. The structures of (4) and (5) have been determined by X-ray methods. Crystals of (4) are monoclinic, space group P 21/m, with Z= 2 in a unit cell of dimensions a= 9.122(3), b= 15.010(6), c= 12.580(7)A, and β= 107.86(3)°. Crystals of (5) are monoclinic, space group P21/c, with Z= 4 in a unit cell of dimensions a= 8.921 (3), b= 14.165(2), c= 26.72(1)A, and β= 91.95(4)°. The structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R= 0.049 and 0.058 for 1 329 and 1 994 observed reflections, respectively. Both structures consist of a trigonal bipyramid of metal atoms with the cobalt atoms occupying the triangular equatorial plane and the copper or gold and ruthenium atoms situated at the apices. Three carbonyl groups bridge the Co–Co edges; the other nine are terminal, three attached to the Ru atom and two to each Co atom. Similarities in the bonding relationships of (4) and (5) are analyzed and rationalized through extended Huckel calculations.

The replacement of one hydrido-ligand in [(η-C5H5)NiOs3(µ-H)3(CO)9] by MPPh3+(M = Cu or Au). Crystal structure of [(η-C5H5)NiOs3(µ-H)2-(µ-AuPPh3)(CO)9], the first gold–nickel–osmium cluster

Abstraction by NaH in tetrahydrofuran of one hydride ligand of [(η-C5H5)NiOs3(µ-H)3(CO)9](3) leads to the anion [(η-C5H5)NiOs3(µ-H)2(CO)9]–, which upon reaction with M(PPh3) Cl (M = Au or Cu) leads to the pentametallic clusters [(η-C5H5)NiOs3(µ-H)2(µ-MPPh3)(CO)9][M = Au, (1); M = Cu, (2)]. The structure of (1) has been determined by X-ray methods. Crystals are triclinic, space group P with Z= 2 in a unit cell of dimensions a= 13.923(3), b= 14.213(4), c= 9.544(4)A, α= 93.81(4), β= 105.48(2), γ= 102.83(2)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares to R= 0.055 for 2 867 observed reflections. The structure of (1) can be derived from that of (3) by replacing one of the three equivalent hydride ligands by AuPPh3+. The metal cluster can be described as a NiOs3 tetrahedron with an Os–Os edge bridged by an Au atom.

Synthesis of heteropentametallic clusters containing three different metals: MCo3(CO)12M′L (M = Fe, Ru; M′ = Cu, Ag)

Abstract The new heteropentametallic clusters MCo 3 (CO) 12 M′L ( 1 – 7 ), of trigonal bipyramidal structure, have been prepared from the tetrametallic anions [MCo 3 (CO) 12 ] − (M = Fe, Ru) and L → M′Cl (M′ = Cu, Ag; L = PPh 3 , ) or [Cu(CH 3 CN) 4 ] + . Metal exchange is observed when Na[RuCo 3 (CO) 12 ] reacts with [Rh(μ-Cl)(CO)] 2 and with CpMo(CO) 3 Cl, affording RhCo 3 (CO) 12 and CpMoCo 3 (CO) 14 , respectively.

Spin-72 nutation and Hahn-echo amplitudes in model compounds and application to the tetrahedral cluster Co4(CO)12

Spin-7/2 central line intensities are calculated for any ratio of the quadrupolar coupling constant to the radiofrequency field for both one-pulse and two-pulse Hahn-echo experiments and tested by 59Co NMR on the model compounds, Na3[Co(NO2)6] and trans-[Co(en)2(NO2)2]NO3. The Hahn-echo sequence is then used to obtain the quadrupole coupling constant and asymmetry parameter on a powder sample of Co4(CO)12. This technique is found to be particularly useful when the NMR spectrum is broad and featureless.

59Co NMR in Tetrahedral Clusters

A 59Co NMR study of a series of mixed‐metal tetrahedral clusters prepared from the basic structures MCo3 (M = Fe, Ru) by the substitution of one, two or three carbonyl groups by phosphines, phosphites, thioethers or amines is described. The variations of the chemical shifts and the linewidths are discussed according to the nature of M and the type of ligand. Some theoretical considerations show the difficulty of interpreting rough correlations found between NMR parameters and electronic properties of the ligands.

Synthesis of Palladium Clusters with the P--N--P Assembling Ligands (Ph2P)2CH2 (dppm) and (Ph2P)2NH (dppa). Crystal Structure of [Pd4(μ-Cl)2(μ-dppm)2(μ-dppa)2](PF6)2

Tetrapalladium clusters containing dppa or dppa and dppm bridging ligands were prepared by condensation of dinuclear units. Reaction of [Pd2Cl2(μ-dppa)2] with [Cu(PPh3)]PF6 (generated in situ in THF) yielded [Pd4(μ-Cl)2(μ-dppa)4] (PF6)2 (4) in a virtually quantitative yield but [Pd4(μ-Cl)2(μ-dppm)2(μ-dppa)2] (PF6)2 (6) was best prepared in CH2Cl2 from [Pd2Cl2(μ-dppm)2] and [Pd2(MeCN)2(μ-dppa)2](PF6)2 (2). The structure of 6·2(CH3)2CO·2H2O was determined by X-ray diffraction. It consists of a planar, centrosymmetric 10-membered ring structure. The four bridging diphosphine ligands are of two types: two dppa ligands support the Pd Pd bonds [2.6055(4) Å], whereas the two dppm ligands bridge between two palladium atoms separated by 3.722(4) Å, which are also bridged by a chloride ligand.

Metallic nanoparticles from heterometallic Co–Rucarbonyl clusters in mesoporous silica xerogels and MCM-41-typematerials

Impregnation of a mesoporous xerogel or of MCM-41 with an organic solution of the heterometallic cluster [NEt4][Co3Ru(CO)12], followed by thermal treatment under an inert atmosphere, leads to highly dispersed magnetic nanoparticles under milder conditions than when conventional metal salts are used as precursors.