Tetrahedra capping

Sdts of the deep violet anion [V2 Vg026] " have been obtained adventitiously from nonaqueous media. The crystal stmcture of the tetramethylamraonium salt shows an anion of virtual Sg symmetry composed of a ring of eight corner-shared V 04 tetrahedra capped on either side by square pyramids." The polymeric anion in K2V3O8, which is obtained... 

The structure of [ Cu(bpy) 2(V02)3(P04)(HP04)2], shown in Figure 80, may be best described as Cu2(bpy)2(V0)2(P04)2(HP04)2 chains linked through square pyramidal VO5 units into a 2D network. Embedded within the chain are Cu2(bpy)2(V0)2(P04)2 clusters, constructed of a central ring of edge- and comer-sharing VOs octahedra and PO4 tetrahedra capped by two... 

Basic aqueous solutions of Pb11 yield crystals containing the cluster [OPb6(OH)6]4+ (6f)221 with a centred (p4-0)Pb4 tetrahedron capped on two faces by (p3-OH)3Pb units. There are three types of Pb coordination, and the Pb—<) distances range from 2.2-3.0 A.221 X-ray scattering data, vibrational spectra and potentiometric titration data222 indicate that this cluster also exists in solution. 

The structures of crystalline materials can be relatively simple, such as that of [CyF5N(H)Li(thf)2]2, which has a Li2N2 ring with planar N21, or more complicated, such as that of Ii3(RNCH2CH2)3N, Li3(Me3SiNCH2CH2)3N(thf)2,22 or the tetrameric [CsNH(SiMe3)]4, which has a Cs4 tetrahedron capped on each face by /x3-amido groups.23... 

The octanuclear cage [Cog(0)4(02CPh)i2(H20XMeCN)3] 41 [38] features a central cobalt tetrahedron capped on each face by a (14-0x0 imit which binds to a further Co atom above the face (Figure 18). The structure could therefore be... 

It can be viewed as a MoFe3 tetrahedron capped by a Fe2(S)2(CO)6 unit. Each face of the tetrahedron is triply bridged by a Sulfur atom. 

Os atoms define distorted tetrahedron capped 23 by the N-atom of methylnitrene group on the face containing three longer Os-Os distances (2.834 A) d(Os-Os) = 2.75-2.835 A. 

Figure 25.11 Metal frameworks of some high-nuclearity binary carbonyl and carbonylate clusters of osmium (a) Os5(CO)i6 (trigonal bipyramid) (b) Os6(CO)ig (bicapped tetrahedron, or capped trigonal bipyramid) (c) [Os6(CO)ig] (octahedron) (d) Os7(CO)2i (capped octahedron) (e) [Osg(CO)22] (bicapped octahedron) (f) [Osi7(CO)36] (3 shaded atoms cap an Osu trigonal bipyramid).

The field of alkyl and aryl Co complexes in low formal oxidation states has been extensively studied, and is frequently associated with cluster chemistry.92 Alkyl and aryl ligands, with or without additional functionality, are often co-ligands with tt acceptors such as carbonyls and/or phosphines, e.g., (MeOCOCH2)Co(CO)3(PPh3).93 A simple example of a cluster is (RC)Co3(CO)9, where the triangular Co(CO)3 3 moiety is capped by the 73-alkyl fragment, which occupies the apex of a distorted Co3C tetrahedron. 

Kadokura, M., Wada, T., Urashima, C., and Sekine, M. (1997). Efficient synthesis of g-methyl-capped guanosine. V-mphosphate as a SLtcrminal unique structure of U6 RNA via a new triphosphate bond formation involving activation of methyl phosphor-imidazolidate using ZnCl2 as a catalyst in DMF under anhydrous conditions. Tetrahedron Lett. 38, 8359-8362. 

B. W. Greatex, S. J. Brodie, R. H. Fumeaux, S. M. Hook, W. T. McBumey, G. F. Painter, T. Rades, and P. M. Rendle, The synthesis and immune stimulating action of mannose-capped lysine-based dendrimers, Tetrahedron, 65 (2009) 2939-2950. 

One of the most efficient structure building principles in lithium organic chemistry is the Lis triangle /zs-capped by a carbanionic Ca atom. This structural motif can further be aggregated to build deltahedral metal cores. The Li4 tetrahedron is found in various lithium organic tetramers while the Lie octahedron is present in many hexamers (Figure 4). 

C -coordinated. Aryl-substituted alkyl C-Li bond. Within intact tetrahedron. Within broken tetrahedron. Within Lis center coordinated Lij triangle. N-bridged Li- Li vector. Li- -Li vector coordinated by two Cp atoms. Oxygen atom caps adjacent Lis triangle. caps adjacent Lis triangle. 

He, F.-C., Liu, L.-B., and Li, X.-V. (1990). Molecular models constructed in an easy way. Part 1. Models of tetrahedron, trigonal bipyramid, octahedron, pentagonal bipyramid and capped octahedron, y. Chem. Educ. 67,556—558. 

Ru(0) (0H)] ESR spectra of [RuO ] in aqueous base suggest that this species may be present, having a flattened monocapped tetrahedral structure with a long Ru-O(OH) bond, or a bi-capped tetrahedron [Ru(0) (0H)3] [456]. It has however also been suggested that such an ESR signal could arise from [Ru(0)/0Hy - [474]. 

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