Complexes polymetallic

2 Polymetallic Complexes Treatment of the acetylide cluster [Cp WRc2(CO)9(C R)] (R = Ph, C(Me)=CH2) with O2 or N2O afforded clusters containing a terminal 0x0 ligand of the type [Cp WRe2(0)(C0)g(CCR)], structurally characterised for R = C(Me)=CH2-Hydrogenation of the cluster afforded three isolable clusters, showing an example of oxo-mediated sequential conversion of acetylide to alkenyl and alkylidene. 

A kinetic and electrochemical study of the parallel 1x3-112 alkyne-cluster interaction in triiron compounds of the formula [Cp2Pte3(CO)5(CF3CCCF3)] has been reported.  

Cleavage of the acyl C-O bond in the mixed metal cluster [CpWOs3(CO) 11 (Jl3-Tl -C(0)CH2To1)] has been reported to afford the oxo-alkylidyne complex [CpWOs3(CO)io( i-0)(H3-CCH2To1)] and reactions of the product described. 

Syntheses and X-ray studies of ruthenium clusters obtained by reaction of (alkylthio)alkynes RCCSEt, (R = Me, Ph) with [Ru3(CO)i2l have been reported.  

The kinetics and mechanism of the hydrogenation of diphenylacetylene promoted by the alkenyl-bridged cluster [Ru3(CO)8(li3-Ti2-ampy)(p,-T T 2-PhC=CHPh)] (Hampy = 2-amino-6-methylpyridine) has been investigated497. The synthesis, structure and hydrogenation catalytic activity of the related [Ru3(CO)6(PPh3)2(lt3-r 2-ampy)(n- nl Ti2-PhC=CHPh)] have been described . Tri- and hexanuclear ruthenium complexes [Ru3(CO)8(lA-RCOCH=CPh)2l and [Ru6(CO)i2(lt-CO)2( X-H)2(M4-0)(p.-RCOCH=CPh)2] (R = Me, p-Tol) have been prepared and characterised by X-ray diffraction. 

Treatment of [Cp Re(NO)(PPh3)(GCLi)] with [Re2(CO)iol and [Me30BF4] followed by [BF3] affords O, after skeletal rearrangement, (62). 

Reaction of the l,r-dialkynylferrocene [(T)5-C5H4C-CR)2Fe] (R = Ph, SiMe3, Me) with excess [Co2(CO)8] afforded S [(nS-C5H4C5CR)2Fe Co2(CO)6 2] in which a Co2(CO)6) moiety is coordinated to each alkyne. 

The reaction of [Fe2(CO)6()i-S)2] with [Ni(T] -COD)2l at -78°C afforded the arachno-cluster [Fc2(CO)6()X3-S)2Ni2] which decomposed on warming to give FeNiS which was characterised by energy dispersive X-ray analysis (EDAX). The X-ray crystal structure of [(OC)3l e(p-PCy2) ji-Au(PPh3) 2Pt(Tl -COD)]+[PFe] has been reported S. 

The electrochemical two-electron reduction of [Fe3(CO)9(EtC CEt)] and [Os3(CO)7(dppm)(PhC=CPh)] has been investigated by fast-scan cyclic voltammetry and evidence provided for the reorientation of the alkynes on the trimetallic cluster during the reduction process. The electrochemical reduction of the clusters [ Ru3(CO)9(p,3-n2-C-CBu ))2Hg] and [Ru3(CO)9(li3-Tl2-C CBu )HgX] (X = Re(CO)5, MoCp(CO)3 has been studied377. 

Two diastereomers of the linear tetranuclear cluster [Ru4(CO)io(MeC=C(H)C(H)=NPr )2], (65), were separated by preparative HPLC and structurally characterised. Their intramolecular and intermolecular interconversion pathways were studied in detail. TTie X-ray crystal structures of nido-[Ru4(CO)io(li-CO)2 iU-n .1) , n -P(Ph)C(CiCMe)CMe) ], c/oso-[ Ru4(CO)io()l-CO)(P4- 

The reaction of alkynes [RCCR ] (R = R = Ph R = Ph, R = H R = R sH) with the tetrahedral heteronuclear cluster [RuCo3(CO)n(NO)] afforded338 a mixture of the butterfly cluster [RuCo3((X))9(NO)(P4- n -RCCR )], formed via specific insertion of the alkyne into the Co-Co bond, and the trinuclear cluster [RuCo2(CO)9(p3-Ti2-RCCR )]. The tnixture was analysed using 59co-NMR spectroscopy and the X-ray crystal structure of [RuCo3(CO)9(NO)(m- n2-PhCCH)] was determined. 

Oxidation of the hexairidium cluster [Ir6(CO)isP with ferridnium salts in the presence oi diphenylacetylene afforded [Ir6(CO)i4( x-Ti2-PhCCPh)], which was charactoised by X-ray diffraction340. When this product was heated with excess diphenylacetylene, the cluster [Ir6(CO)i2(M.-T 2-PhCCPh)2], also crystallographically characterised, was obtained O. Both compounds were found to consist of an octahedron of iridium atoms with alkynyl units coordinated to triangular faces of the metallic cores in (p3- n2 -fashion. 

Werner, C.B. Dobson and G.R. Dobson, Inorg. Chem., 

Barker, S.L. Cook, M.E. Lastenra-Sanchez and SJE. Thomas, J. Chem. Soc., Chem. Commun., 1992, 830. 

Merle-Mejean, C. Cosse-Mertens, S. Bouchareb, F. Ga J. Mascetd and M. Tranquillc, J. Phys. Chem., 1992.96,9148. 

H3-vinyl complex (147). Reaction with a V2u lety of 2e ligands 

Induces hydrogen migration thus, treatment with CO or PEt  

CP3M3(H3-CO)(u -PhC = CPh) (M = Rh, Ir) undergo alkyne scission on flash pyrolysis to give Cp M (u -CPh)2 complexes  

Kane-Magulre, E.D. Bonlg and D.A. Swelgart, Chem. Reviews, 1984, 

Kane-Nagulre, Hech. Inorg. Organomet. React., 1984, 301. 

Treatment of [Ru3Pt( j-H) (p4-t -C CBu ) (CO) 9 (dppe) ] with Ph2PC CPPh2 gave the butterfly cluster [RU3Pt(p-PPh2)-( P4-ti -C CBu ) (CO) 7 (dppe) ] which was crystallographically characterised . 

The synthesis and molecular structure of the alkyne-bridged mixed-metal butterfly cluster [Co2Rh2-( i-CO) 2(CO) 7 (m4-ti -HC2Bu ) (PPhs) 3 have been achieved . The 

-Hslung Wang, P.H. Wermer, C.B. Dobson and G.R. Dobson, Inorg. Chim. Acta, 1991, 183, 31. 

Enders, T. Schmitz, G. Raabe and C. KrOger, Acta Crystallogr., Sect. C, 1991, 47, 37. 

Irvine, C. Glldewell, D.J. Cole-Hamilton, J.C. Barnes and A. Howie, J. Chem. Soc., Dalton Trans., 1991, 1765 

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Magnetic exchange, 1,257, 267 polymetallic complexes, 1,138 Magnetic moment, 1, 259 Magnetic properties atomic systems, 1,260 cubic field systems, 1,263 free-atom states and terms, I, 260 lower symmetry, 1, 264 zero-field splitting, 1,262 Magnetic susceptibility, 1,256, 259 Magnetism... 

The interaction of butadiynediyl dimetal complexes [Fp -C -CsC-M, Fp =FeCp (CO)2, M= Fp, Rp, SiMea, Rp= RuCp(CO)2] with diiron nonacarbonyl, Fe2(CO)9, results in the formation of a mixture of products, as is also observed in the case of their interaction with organic acetylenes. Interesting polymetallic complexes, propargylidene-ketene compounds, zwitterionic cluster compounds, and pa-p -propargylidene-cyclobutene compoimds were isolated from the reaction mixtures and successfully characterized. The product distributions were found to be dependent on the metal fragment (M) at the other end of the C4 rod. The results of the reaction are described... 

We cite here two examples of triiron complexes which can depict well the possible intramolecular electronic interactions in polymetallic complexes. First of all we take into account that, as discussed in Chapter 2, Section 1.5.1 and Chapter 4, Section 1.3, from the electrochemical viewpoint, the existence of a mutual electronic (through-space or through-bond) interaction in molecules containing two or more redox-active centres leads to the appearance of separate electron transfer processes. There are, however, two main classes of polynuclear molecules ... 

In the case under examination (heterogeneous catalysis in the presence of coordinated polymetallic complexes) the molecular weight of the polymer is generally almost independent of the polymerization time, whenever the polymerization lasts for more than about 10 min. 

Studies of a number of polymetallic complexes also provided evidence for C—H coordination. Particularly notable was a beautiful NMR study by Calvert and Shapley of a triosmium complex, which was shown to exist as an equilibrium mixture of two structures, one of which included a C—H—Os linkage.,JJ... 

A new field of coordination chemistry is that of polymetallic cage and cluster complexes [Mm(p-X)xLJz with molecular (i.e. discrete) structure. They contain at least three metal atoms, frequently with bridging ligands X and terminal ligands L. These compounds link the classical complexes (m = 1) and the non-molecular (m - oo) binary and ternary compounds of the metals.1 Molecular polymetallic clusters (with finite radius) also provide a link with the surfaces (infinite radius) of metals and their binary compounds.2"5 Polymetallic complexes are known for almost all metals except the actinides. 

A key property of these polymetallic complexes is geometrical structure, more variable and diverse than the coordination stereochemistries of monometallic complexes or the symmetrical lattices of non-molecular compounds. The following well-defined aggregation modes illustrate the geometrical scope of the field. 

The development of the relatively youthful class of polymetallic complexes has depended on the advent of routine X-ray structure determination, and consequently the bulk of the information and understanding at present involves geometrical structure. This metrical bias, reinforced by the intriguing unpredictability of many aggregate structures, determines the content and organization of this chapter. The primary classification of compounds is structural, according to increasing numbers of metal atoms. 

Lack of space has forced exclusion of some clusters, and topics described in reviews elsewhere are afforded reduced coverage. Literature citation for established classes of aggregates such as the polyoxometallates is limited to contemporary leading references. Dimetallic and linear polymetallic complexes are excluded. 

Polymetallic complexes presenting directional energy migration are of much significance for the design of photochemical molecular devices. Large arrays of multiple photoactive and redox-active building blocks (of ruthenium- or osmium tris(bipyri-dine)-type for instance) have been constructed for such purposes [A. 10,8.25-8.27]. 

The C02-bridged polymetallic complexes involve coordination of the carboxyl carbon to one metal and bonding of one or two carboxyl oxygens to a second (or third) metal center, leading to compounds of the gm-T n type, as described in Figure 4.2. The first bridged C02 complexes to be structurally characterized were Fe-Re, Ir-Zr, and Rh-Os bimetallic complexes, or polymeric Co, Os, and Ru clusters (for a review, see Ref. [4] and references therein for details). 

Winpenny, Richard E.P., Design and Serendipity in the Synthesis of Polymetallic Complexes of the 3d-Metals, 5, 193. 

In a general sense, metal clusters have been regarded as electron reservoirs which can gain or lose electrons at will without molecular disruption. However, few real species possess this property, and the addition or subtraction of more than one electron usually leads to structural changes, and a concomitant increase in reactivity. Detailed studies are being made, therefore, of redox-induced changes in structure and reactivity, studies which promise to provide rational routes to new polymetallic complexes and information about electronic structure. 

Wang, R., Liu, H., Carducci, M.D., Jin, T, Zheng, C., and Zheng, Z. (2001) Lanthanide coord with a-amino acids under near physiological pH conditions polymetallic complexes containing the cubane-like [Ln (P3-0H)6] cluster core. Inorganic Chemistry, 40, 2743-2750. 

Winpenny, R.E.P. (1999) Design and serendipity in the synthesis of polymetallic complexes of the 3d-metals. Perspectives in Supramolecular Chemistry, 5 (Transition Metals in Supramolecular Chemistry) 193-223. 

Polymetallic complexes with suitable bridging ligands can be useful models of molecular wires. In the present chapter, we shall consider mainly bimetallic systems in which two metal atoms are connected by a bridging ligand, with the general topology shown in Figure 1. 

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