Tetranuclear

Molecular examples of trivalent molybdenum are known in mononuclear, dinuclear, and tetranuclear complexes, as illustrated in Figure 5. The hexachloride ion, MoCk (Fig- 5a) is generated by the electrolysis of Mo(VI) in concentrated HCl. Hydrolysis of MoCP in acid gives the hexaaquamolybdenum(III) ion, Mo(H20) g, which is obtainable in solution of poorly coordinating acids, such as triflic acid (17). Several molybdenum(III) organometaUic compounds are known. These contain a single cyclopentadienyl ligand (Cp) attached to Mo (Fig. 5d) (27). 

For tetranuclear cluster complexes, three stmcture types are observed tetrahedral open tetrahedral (butterfly) or square planar, for typical total valence electron counts of 60, 62, and 64, respectively. The earliest tetracarbonyl cluster complexes known were Co4(CO)22, and the rhodium and iridium analogues. The... 

Ta, tetranuclear, orange coloured derivatives Li4[Nb4S2(SPh),2] > and [Nb4S2(SPh) -(PMe2R)4] (R = Me, have been shown to... 

Mono(cyclopentadienyl), or half-sandwich poly-oxo complexes are of interest as hydrocarbon-soluble models for oxide catalysts. The action of water on [Ta( j -C5Me5)(PMe3)2] yields the colourless [Ta4( j -C5Me5)407(0H)2] which has a tetranuclear butterfly core (Fig. 22.12c).( >... 

Pd2L(AN)2l(C104)2 (H2L = /VjV-diethyl-2,6-dialdiminobenzene) and pyrazole form [Pd2L(Hpz)4](C104)2 (91POL1513). With excess pyrazole and in the presence of triethylamine, the tetranuclear complex 248 is formed. 

Biimidazole and bibenzimidazole with [(ri -2-RC3H )Pd(p-Cl)]2 (R = H, Me) taken in the 2 1 molar ratio in the presence of methanolic potassium hydroxide give complexes of the type 146 (83JCS(D)1729) and with [(ti -2-RC3H ) Pd(Mc2C0) ](C10 ) - 147. When the ratio of 2,2 -biimidazole or 2,2 -bibenz-imidazole and [(Ti -2-RC3H )Pd(p-Cl)]2 (R = H, Me) is 1 1, the homo-tetranuclear species 148 result. Heterotetranuclear palladium(II)-rhodium(I) complexes 149 (L2 = cod) follow from [(TiLcod)Rh(Hbim)] and [(ri -2-R-C3H )Pd(acac)]. They are readily carbonylated with complete substitution of... 

Interaction of the latter with triphenylphosphine in the presence of sodium perchlorate leads to the cationic complex [(dppm)Au2(li-L)Pd(C Fj)(PPh3)]C10. Reactions of [L Au(p-L)AuL ] (L = bibenzimidazolate L = PPh, dppm)] with [Pd(0C103)(C Fj)(PPh3)2] do not lead to the tetranuclear products. Only the bibenzimidazolate (L) dinuclear product [(PPh3)(C F3)Pd(p-L)Pd(C, F3)(PPh3)] could be isolated in both cases. 

L = C3H3, C H ) and then [Rh(acac)(CO),] to yield the tetranuclear species 180 (85ICA(i00)L5), where the heterocyclic ligands are tridentate. The product reacts with the rhodium(I) dimer [Rh(CO)2Cl]3 to give the trinuclear complex 181. In the solid state, the molecules of this complex form the intermolecular stacks along the z-axis. 

R = R2 = R3 = R4 = R5 = Me] also reacts with [(i -C2H4)2RhCl] to give the tetranuclear product 3 formulated as a pentadecker species with two central bridging chlorine atoms. 

In the rhodium and iridium complexes, the C-coordination, carbene function, and cyclometallated cases prevail. Benzothiazole-2-thione was studied extensively as a ligand and various situations of the exocyclic S-monodentate coordination as well as N,S-combinations in the di-, tri-, and tetranuclear species were discovered. 

All three M+ ions are known to form compounds with the unusual digonal linear coordination (see also section 4.9.7), though this is most common for gold. As a result, complexes R3PMX of copper and silver are normally di-and tetranuclear species with 3- or 4-coordinate metals, while the gold analogues are 2-coordinate monomers. This is the reverse of what would be expected on steric grounds [13, 14],... 

In tetranuclear dyes such as in Scheme 69 with two independent chromophoric chains, providing the chains are of different length, the absorptions maxima lie at the same A as each of the component cyanine but chains of equal lengths produce a shift of the two A, one toward longer... 

The reaction of diisopropylcarbodiimide with ZnMe2 (90 °C, 60 h) was recently reported to yield a product mixture, from which three unusual compounds could be isolated and structurally characterized, including two tetranuclear zinc amidinate clusters (Scheme 162). ... 

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