Structure pentanuclear species

Figure 10.79 X-ray molecular structures of cyclic helicates (a) pentanuclear species formed from 10.124 and templated by Cl 87 (b) hexanuclear species formed from 10.126 and templated by C104 (reproduced by permission of The Royal Society of Chemistry).

Fe4N(CO)i2] and [Fe5N(CO)i4]" (90). After 1 hour at 130 C the tetranuclear cluster is isolated in 3.3% yield, while the pentanuclear species, which forms after longer reaction times (2 hours) at a slightly higher temperature (145 C), is produced in 66% yield. This anion could be protonated and the structure of HFesN(CO)i4 is shown in 22. It was noted that below 130°C a nitrosyl complex was formed. 

The pentanuclear carbido species Ms(CO)lsC (M = Fe, Ru, Os) have been prepared. The iron compound has been known for some considerable time (209), but the ruthenium and osmium complexes were prepared recently by pyrolysis reactions (210). The ruthenium adduct was only isolated in low yield (—1%), while the osmium complex was obtained in higher yield (—40%). The infrared spectrum and mass spectral breakdown pattern indicate a common structure to these compounds. The molecular structure of the iron complex is shown in Fig. 46. 

Selected examples of pentanuclear metal clusters are listed in Table 19.4.1. In these examples, the calculated bond valence b is exactly the same as the number of edges of the metal skeleton, indicating 2c-2e M-M bonds. In general, electron-rich species have lower bond valence and more open structures than... 

Pentanuclear Complexes. In [Cu5(/j,-SBu )6] there is tbp Cu1 with /X.-SR and this structure is also found in the aryl species (see later), MgCu4Ph6, [Cu5Ph6], and [Li2Cu3Ph6]. The phenyl groups bridge metal atoms that may be Cu only, Cu + Li, or Cu + Mg. 

The structural relationship between the pentanuclear, nonanuclear, and tetradecanuclear species can be easily discerned from Figure 6.38. 

Figure 6.38 Core structures of pentanuclear, nonanuclear, and tetradecanuclear complexes, by which the modular relationship between different species is revealed.

A novel class of chalcogen(II) halogen compounds was established recently by the preparation of the first simple binary mononuclear and oligomeric haloanions of divalent selenium and tellurium. The chemistry of these compounds is especially variable for selenium, and a number of highly interesting mono-, di-, tri, tetra- and pentanuclear anionic species with composition X Ym have been synthesized and characterized by structure analyses and spectroscopic studies up... 

The tetranuclear clusters are structurally the same as the aforementioned tetranuclear species (Figure 108), but with DBM rather than acac ligands building up the periphery. The pentanuclear clusters have a square pyramidal core (R = Dy, Figure 111). Each triangular face of the... 

A pentanuclear mixed chalcogen/carbonyl cluster complex with ethanethiolate ligands is the cobalt-containing species [Co5(SEt)5(CO)io], which was structurally characterized by X-ray methods (Fig. 22). 

As for tetranuclear clusters, pentanuclear transition metal clusters are only capable of partially encapsulating a main-group heteroatom. The c/o5o-pentanuclear cluster, the trigonal bipyramid, has an interstitial cavity of similar dimension to that of the tetrahedron, and must therefore open-up if it is to accommodate a semi-interstitial atom. The most commonly observed M5E clusters (E = main-group atom) adopt square based pyramidal structures, which can be derived from the trigonal bipyramid by M-M bond cleavage or can, alternatively, be viewed as /i/Jo-octahedral species (Scheme 2). 

A related pentanuclear / 3-oxo species 146 with a highly distorted bow-tie structure was isolated in low yield. " The mixed-metal clusters [Ru2Mo2(/i3-S)2(/ -SR)(/i-X)(GO)4Gp2] [X = SR, R = Et, Pf 147 or PPh2 148 ] were prepared by the treatment of 149 or 150 with Ru3(GO)i2, which involved the dealkylation of the thiol ligand at the dimolybdenum center. 

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