Butterfly structures

Surprisingly, X-ray structural analysis of the dark-green, hygroscopic tetrabutylam-monium salt of 5//-dibenz[6,/]azepine reveals that the potentially antiaromatic 5//-dibenz-azepine anion has a less pronounced nonplanar butterfly structure (161° vs. 144 ) than 5H-dibenz[6,/]azepine.243... 

The 8V+ 2 rule has been completely substantiated by the calculated ground state geometries of tetramers in Table 2 [7], The cluster (lOe) is linear [11]. The Si/" cluster (18e) has a butterfly structure (Dp [18],... 

In addition, a butterfly structure (Figure 11) which contains two tin atoms in a dimeric representation [n-BuSn(OH)(02P(CgHii)2)2]2 arises in the same reaction as the cube (Kumara Swamy, K. C. Day,... 

By slight modification of the synthetic procedure outlined in Equation (35), a P2 unit side-on bound to two Ni° complex fragments can be obtained according to Equation (36) (1060). X-ray crystallography shows a butterfly structure with d(P=P) = 2.121(6) A 2 48... 

Particular organic ligands such as acetylenes and allenes can induce opening of the tetrahedron to give a folded rhombus, which is usually classified as a butterfly structure (Fig. 17). This butterfly structure is also rather surprisingly found for the anion [Fe4(CO)13H] 178, as shown in Fig. 18. 

Butterfly. While Tl2Te22- has a (2)(1) + (2)(4) + 2 = 12 skeletal electron count isoelectronic and isolobal with neutral cyclobutadiene, it undergoes a different Jahn-Teller-like distortion to the butterfly structure discussed by Bums and Corbett [81]. 

The tetrahedral geometry of the [Fe4(CO)i3]2 precursor is lost, being replaced by a butterfly structure. The Fe2-Fe3 bond constitutes the body of the butterfly, while the FelFe2Fe3 and Fe4Fe2Fe3 triangles constitute the wings. It can be seen that the carbide carbon atom is positioned half way between the tips of the two wings. 

To do this, two additional electrons must be added to the tetrahedron to keep all electrons paired. In feet this is a general principle Adding electrons to a closn complex opens the structure, converting it to one ot lower symmetry. The butterfly structure results when an edge is removed from the tetrahedron. 

If we add two electrons to the butterfly structure, another edge is lengthened (another bond broken) and we end up with a square plane. 

Figure 1 Structural relationships between the cores of (a) (p3-X)8M4 core (6m), (b) (p-OPr )8Mo4Cl4, (c) the Mo4Br4 OPr )g butterfly structure, and (d) the [Mo4In]2 butterfly structure...

A variety of oligomers with novel drum and ladder structures have also been prepared. They have the formulas [R Sn(0)02CR]6 and [(R Sn(0)02CR)2 R Sn(02CR)3 2, and contain four- and six-membered rings. They can be synthesized by the reaction of stannoic acid with a carboxylic acid, but the reaction of RSnCl3 with the silver salt of a carboxylic acid can also be used. If diphenylphosphinic acid or dicyclohexylphosphinic acid is used instead of the carboxylic acid, oxygen-capped clusters or cubic and butterfly structures are obtained.69... 

The hinged butterfly structure (a) is exhibited by Ru5C(CO)16, while the bowtie structure (b) is found for Os5(CO)19. These have N values of 7 and 6 respectively, consistent with the number of M-M bonds in each case. 

In the terminology used in Wade s rules1" , the 60-electron tetrahedral cluster [HFeRu3(CO)i3] is considered a closo species (XXIX) and the 62-electron open butterfly structure of [HFe4(CO)13] is considered a nido species (XXX). The structural difference is related to the fact that one of the CO groups is a 2-electron donor in the former and a 4-electron donor in the latter. 

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