Clusters complexes

Three new mixed-metal cluster species derived from (Taf,Cl,2) , [(Tas-MoC1 2)Cl6] and [(Ta Mo2Clj2)Clg] , have been prepared by 

Niobium(m) and Tantalum(in) Complexes.—The first tantalum(iii) compounds have been reported. TaCl and MeCN react at 100 °C to form the diamagnetic dimer [TaCl3(MeCN)2]2- The compound exhibits five i.r. bands in the 23(X) cm region, suggesting more than one environment for the MeCN groups the structure (44), analogous to that of [WCl3(py)2]2, has been proposed for the 

The use of dppf as a flexible and versatile ligand with catalytic potential is too important to be left out of a study of metal cluster chemistry. Its variable coordination modes in adapting to metals of different steric and electronic demands and its ability to span a wide range of M-M distances make it a very attractive stabilizing ligand for metal clusters. 

Ru-P distance (average bond length 2.3503(8) A) being marginally shorter than that in Ru3(CO)i 1 (PFcPhj) (2.369(1) A), which has a shorter Ru-Ru bond (average bond length 2.88 A) [9]. 

This ring thereby constitutes an unusual yu-ij. ij -vinyl group whereby the phosphino carbon is also metalated. Intramolecular oxidative addition of the ortho C-H bond of the phenyl substituents is a common feature in crowded iridium phosphine complexes [65, 309, 310]. 

Mixed-metal clusters of dppf have also been reported. One special example is M4(/i-H)(CO)i2( 6-B)Au2(/i-dppf) (M = Fe, Ru, 7) [55], whereby a butterfly cluster is capped with a heterometal moiety Au2(dppf)j with an Au-Au length of 2.818(2) A. This Au-Au interaction is in contrast to the large Au-Au separation in Ru4(jU-H)(CO)i2(/i-BH)Au 2(/r-dpp0 [55], which can be considered as two 

The compounds described below contain two or more different types of metal atom at least one of these atoms is that of a transition metal. In most, but not all, of the structures direct metal-metal bonding is thought to be present. Homonuclear metal cluster compounds are described in the chapters devoted to the appropriate metal, 

For many of the compounds discussed the failure of spectroscopic methods to indicate an unambiguous structure has made resort to X-r y analysis necessary. Structural studies have also been motivated by interest in the nature of metal-metal bonding. In this connection a recent paper on the general theory of bonding in cluster and ring compounds of main-group and transition metals is of interest.  

1 Complexes containing Atoms of Two Different Transition Metals 

Au-Co bond length of 2.50(1) A is believed to be consistent with a bond order of unity. The Co-C distances range from 1.56(9) to 1.83(9) A. The equatorial carbonyl groups are bent significantly towards the gold atom and away from the axial carbonyl, the Au-Co-C(equatorial) angles varying between 

74(3) and 82(3)°. The Au-P distance is 2.23(2) A and the gold co-ordination is almost exactly linear, the Co-Au-P angle being 177.5(5)°. In the related complex (2) the cobalt atom again has trigonal-bipyramidal co-ordination an axial site is occupied by a silver atom and the Ag-Co-C(equatorial) 

Edge-shared tetrahedra Centred crown Trigonal prism Octahedral Cube 

Centred cube Pentagonal bipyramid Centred icosahedron Complex structure 

Note Some of the structures in this table are known to have analogues 

While some cluster complexes are based on the more symmetrical polyhedra such as the tetrahedron or octahedron (Table 8.12), others appear to form condensed and distorted versions of these and are generally less symmetrical. The larger complexes are frequently unique and difficult to describe in simple geometrical terms. 

Metal cluster compounds of this type are currently of interest because they may show a transition from insulating to electrically conducting properties, as their molecular or particle size is increased. Metal particles are known to become non-conducting when their size is reduced below certain critical limits. 

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For trinuclear cluster complexes, open (chain) or closed (cycHc) stmctures are possible. Which cluster depends for the most part on the number of valence electrons, 50 in the former and 48 in the latter. The 48-valence electron complex Os2(CO)22 is observed in the cycHc stmcture (7). The molecule possesses a triangular arrangement of osmium atoms with four terminal CO ligands coordinated in a i j -octahedral array about each osmium atom. The molecule Ru (00) 2 is also cycHc and is isomorphous with the osmium analogue. 

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... 

Figure 13.24 Structure of the cubane-like mixed metal-metal cluster complex [Sb4- Co(CO)3l4].

Pyrazole and [Os3(CO)io(AN)2] form two isomeric cluster complexes 90 and 91 (82IC634 84POL1175), corresponding to metallation of both basic nitrogen atoms (the major product having the symmetrical structure 90) and C,N-metallation... 

Gold, unlike silver, forms a wide range of cluster complexes [184] where the average oxidation state of the metal is below +1 they may be synthesized by reduction of gold(I) phosphine complexes ... 

The hydrido-transition metal cluster complexes. A. P. Humphries and H. D. Kaesz, Prog. Inorg. Chem, 1979, 25,145-222 (244). 

Recent advances in the vibrational spectroscopy of metal cluster complexes. I. A. Oxton, Rev. Inorg. Chem., 1982,4, 1-26 (107). 

Electronic structures of transition metal cluster complexes. M. C. Manning and W. C. Trogler, Coord. Chem. Rev., 1981, 38, 89-138 (406). 

Cluster complexes containing opened transition metal polyhedra. M. O. Albers, D. J. Robinson and N. J. Coville, Coord. Chem. Rev., 1986,69,127 (357). 

The electronic structure of transition metal cluster complexes with weak- and strong-field ligands. G. P. Kostikova and D. V. Korol kov, Russ. Chem. Rev. (Engl. Transl.), 1985,54, 344 (137). 

Strictly speaking, a cluster complex, as generally considered in or-ganometallic chemistry, consists of a framework of more than two transition-metal atoms. However, in this Section, we shall ignore tra-... 

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. 

Tetraruthenium cluster complexes have been synthesized by the reaction of [ Ru(Cl)(P(OMe)3)2 2(/t-Cl)2(/t-S2)] with Mg, Na, or Na amalgam (Scheme 67). The removal of the terminal chlorine atoms from... 

Group 6 Metal Chalcogenide Cluster Complexes and Their Relationships to Solid-State Cluster Compounds Taro Saito... 

The exploratory solid-state synthetic work of John Corbett has illustrated the diversity, beauty and richness of this chemistry with a large variety of new phases and structures [1-3]. John Corbett was also the pioneer who recognized the potential of these cluster polymers in the development of a versatile solution chemistry [4]. Once the cluster unit has been identified in the solid state, the excision of this motif appears as the most rational method for accessing these cluster complexes in solution [5]. 

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

A systematic study of this class of compounds did not start until twenty years later and led to the preparation of a series of M3Q7X4 (M = Mo, W Q = S, Se and X = C1, Br) inorganic polymers by high-temperature reactions (ca. 350 °C) of the elements in a sealed tube [10-14]. The interest on these cluster phases was mainly motivated by their excellent role as synthons for the preparation of molecular M3Q7 and M3Q4 cluster complexes, as will be presented in this section. 

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