Synthesis cluster complexes

One of the m jor attractions in the metal-atom synthesis of dimer and cluster species is the ability to isolate highly unsaturated species, M Lm, that may then be considered to be models for chemisorption of the ligand, L, on either a bare, or a supported, metal surface (,100). It is quite informative to compare the spectral properties of these finite cluster-complexes to those of the corresponding, adsorbed surface-layers (100), in an effort to test localized-bonding aspects of chemisorption, and for deciphering UPS data and vibrational-energy-loss data for the chemisorbed state. At times, the similarities are quite striking. 

Synthesis and Structure of Molecular M3Q4 and M3Q7 Cluster Complexes 107 7.2... 

Many carbonyl and carbonyl metallate complexes of the second and third row, in low oxidation states, are basic in nature and, for this reason, adequate intermediates for the formation of metal— metal bonds of a donor-acceptor nature. Furthermore, the structural similarity and isolobal relationship between the proton and group 11 cations has lead to the synthesis of a high number of cluster complexes with silver—metal bonds.1534"1535 Thus, silver(I) binds to ruthenium,15 1556 osmium,1557-1560 rhodium,1561,1562 iron,1563-1572 cobalt,1573 chromium, molybdenum, or tungsten,1574-1576 rhe-nium, niobium or tantalum, or nickel. Some examples are shown in Figure 17. 

The incentive for synthesis of molecular cluster complexes with the cluster cores M6E8 (M = Cr, Mo, W E = S, Se, ) has been to solve some of the structural problems in the Chevrel phases (40) and to find solution chemistry to prepare chromium or tungsten Chevrels (28, 77). 

The current interest in cluster complexes as possible catalysts has made desirable a method of synthesis of selectively substituted derivatives, which does not suffer the disadvantages just outlined. Cluster-bound molecules have high and often unique reactivity, and the introduction of tertiary phosphines containing functional groups is often difficult. 

Initial attack of hydroxide ions onto Ni(CO)4 gives as yet uncharacterized species,1 which readily condense with unreacted Ni(CO)4 to give variable mixtures of [Ni5(CO)12]2- and [Ni6(CO)12]2-. Hydrolysis of [Ni5(CO)12]2- in water produces [Ni6(CO)12]2-, according to the above reaction. The dianion [Ni CO) 2]2- is isolated as the tetramethylam-monium salt in a crystalline state in 70% yield. The [Ni6(CO)12]2 dianion is a starting material for the synthesis of several other homo- and heteromet-allic nickel carbonyl cluster complexes.1-9... 

The [Pt6(CO)12]2- dianion can be used as starting material for the synthesis of other platinum carbonyl cluster complexes.1,3... 

SYNTHESIS OF GOLD-CONTAINING MIXED-METAL CLUSTER COMPLEXES... 

Synthesis of Gold-containing Mixed-metal Cluster Complexes 325... 

The complex forms purple air-stable crystals and has good solubility in both polar and nonpolar solvents (e.g., acetone, dichloromethane, tetrahydro-furan, benzene, and hexane). It has been characterized crystallographically.7 The structure is an open, but folded, ladder-like array of six metal atoms with the two platinum atoms in the center. The IR spectrum (hexane) exhibits V(co> bands at 2085 (m), 2062 (vs), 2035 (vs), 2016 (w). Pt2Ru4(CO)18 has been found to be very useful for the synthesis of new platinum-ruthenium cluster complexes.10,12,13... 

Cluster complexes can also be used as starting compounds for the synthesis of heterocarbonyl compounds via ligand replacement. Treatment of [Os3(H)2(CO)9(NMe3)] with S = CPh2 afforded two different osmium clusters depending on the reaction conditions. Each contained a 77 -bound thiobenzophenone ligand.117... 

A novel method for synthesizing polythiaether macrocycles with Re cluster complex was proposed by Adams and coworkers [185]. This process involves catalysis by the Re complex rather than the stoichiometric displacement of dithiol or dithiolates by organic halides, and first example of a catalytic procedure for synthesis of polythiaether macrocycle using thietanes. The macro-cyclic products formed are shown in Fig. 56. 

Fig. 1. Examples of the synthesis of heteronuclear gold cluster complexes by the reaction of Au(PPh3)Cl with transition metal anions.

Oxidation of these complexes releases the apical carbon atom and its substituent in the form of an organic derivative.2 Thus ceric ammonium nitrate oxidation of an RCCo3(CO)9 complex produces the carboxylic acid, RC02H, when the reaction is carried out in aqueous acetone. Thermolysis of RCCo3(CO)9 produces acetylenes or acetylene hexacarbonyl dicobalt complexes, depending on the reaction conditions. Useful applications of these cluster complexes in organic synthesis remain to be developed. 

S. Fedrigo, T. L. Haslett, M. Moskovits, Direct Synthesis of Metal Cluster Complexes by Deposition of Mass-Selected Clusters with Ligand Iron with CO. J. Am. Chem. Soc. 1996, 118, 5083-5085. 

A recent and quite original approach to the synthesis of RejX, cluster complexes involves the cocondensation of rhenium atoms, generated from a positive hearth electron-gun furnace, and reactive halocarbons such as 1,2-dibromo- (or dichloro-) ethane. Extraction of the reaction matrix at room temperature with THF gives Re3X9(THF)3 (X = Cl or Br) in yields of 90%.185 This strategy will likely see further developments in the future. 

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