Distorted-cube complexes

Interestingly, the Mo2S " 4 (Fig- 3f) core stmcture can be viewed as occupying six of the eight vertices of a distorted cube. Reaction of the dinuclear complexes having the Mo2S " 4 core with appropriate metal ions leads to the plaimed assembly of M2M02S4 thiocubane stmctures (19,20). When M = Co (Fig. 3h) the compounds are potential precursors for hydrodesulfurization catalysts (15). 

Lithium halides disrupt the dimeric structures of 59a or 59c to give distorted cubes of the type 60, in which a molecule of the lithium halide is entrapped by a Li2[E(NtBu)3] monomer.164,165 Similar structures are found for the MeLi, LiN3 and LiOCH=CH2 adducts of 59a.166 168 The pyramidal dianion [Te(N Bu)3]2 has a rich coordination chemistry,169 171 although redox processes are sometimes observed in metathetical reactions with metal halides. For example, reaction with PhPCl2 gives a spirocyclic Te(IV) complex of the [PhP(NtBu)3]2 dianion,163 while treatment with Sn(II) salts generates a complex with a four-coordinate Sn(IV) = Te functionality.172... 

Octacoordination is often encountered in lanthanide complexes. The preferred poly-hedra for eight coordination expected on the basis of interligand repulsivities are square antiprism (D ), dodecahedron with triangular faces (Z)2d), bicapped octahedron (D3(i), truncated octahedron (Z)2ft), 4,4-bicapped trigonal prism (C2v), distorted cube (C2v), and cube (0/,). The most commonly observed polyhedra for this coordination number are, however, the square antiprism and the dodecahedron. 

Among the first to be described was the iminoindane complex [ MeIn(NC6H4F-4)-(thf) 4] prepared as shown in Scheme 8.1. The framework consists of a distorted cube with In and N atoms at alternating corners (In—N bond lengths are between 2.19 and 2.41 A). The distorted trigonal pyramidal coordination geometry at each indium atom is... 

A number of interesting modes of coordination are found with simple organic molecules as ligands, e.g. a crystal structure determination of the tetrameric methylzinc(II) derivative MeZn(OMe) 4684 shows the structure to be as in (101). Closely related to this is the structure of the polymerization catalyst Zn(OMe)2(EtZnOMe)6 (102).686 The centrosymmetric complex consists of two enantiomorphic distorted cubes which share a comer the zinc atoms occupy the comers of a tetrahedron and oxygen atoms the comers of an interpenetrating, but smaller, tetrahedron (Zn—O = 2.06 A). 

On complexing with alkali-metal ions the molecule curls up to enclose the cation in an eight-membered distorted cube of oxygen atoms (labelled 4, 54, 12, 62,17, 67,22, and 72, according with the original article) as shown in (6). The complex compounds are all monoclinic, with the properties shown in Table 5 ... 

Special catalyst complexes, like [Zn(OCH3)2 (C2H50CH3)6], form through careful control of reaction conditions by adding 16 moles of methyl alcohol to 14 moles of diethylzinc in heptmie under an argon atmosphere. X-ray analysis shows two different structures one of them is a centrosymmetric complex of two enantiomorphic distorted cubes that share a comer Zn atom. The two would be equivalent if they were not distorted. Another structure, also centrosymmetric, consists of two enantiomorphic distorted structures that resemble chairs without legs, where the surfaces share a common seat. Both types of complexes are active initiators for polymerization of propylene... 

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