Coordination number seven

Complexes of 3d Metals with Coordination Number Seven and Macrocyclic 2,6-Diacetylpyridine and Some Related... 

Following Co(II) complexes, the most frequently found hepta-coordinate structures among 3d metals are those of Mn(II) complexes. Based on literature data, 21 X-ray analyses of Mn(II) complexes with coordination number seven have been reported so far. They include... 

Until several years ago, most of the known compounds of Wn were monomeric complexes, which exhibit mainly coordination number seven, and cluster compounds containing the octahedral W6 nucleus with W—W single bonds. The most important advance in the chemistry of W11 has undoubtedly been the preparation and characterization of dinuclear compounds containing W—W quadruple bonds. 

There are many complexes of lanthanides of coordination number seven [11]. There are many polyhedra for this coordination number, namely pentagonal bipyramid (Dsh) capped octahedron (C3V), tetragonal base trigonal base (Cs), capped trigonal prism (C2V) and capped trigonal prism (C3V). Inter ligand repulsivities have been studied as the function of the form of power law used for energy comparisons between different polyhedra for several coordination numbers [45,46], The order of preference for the different idealized... 

After the advent of the nonclassical if-Vi.2 complexes, polyhydrides had to be reinterpreted [14]. Thus, RuH4(PPh3)3 is not a classical tetrahydride of coordination number seven at the ruthenium atom but a dihydride-dihydrogen complex Ru(H2)(H)2(PPh3)3 of octahedral geometry [25]. 

Regarding the A Os-ZrOa mixed oxides, the cationic radius of Zr (0.079 nm) is larger than those corresponding to Ti and in octahedral coordination (0.060 and 0.053 nm, respectively) [15]. Moreover, its oxygen coordination number (seven or eight) is very different to that of the cationic positions in a pseudospinel structure (four- or sbc-coordinated). Owing to that, it is not probable that Zr" cations could enter the AI2O3 matrix. 

Coordination number seven. The seven-coordinate polyhedron of maximum symmetry is the pentagonal bipyramid (Figure 1) with sp d (xy,x y, z ) hybridization. This polyhedron is commonly found in seven-coordinate complexes. Other polyhedra found in seven-coordinate complexes include the capped octahedron with sp d z, xz,yz) or sp d (z, xy,x - y ) hybridization and the 4-capped trigonal prism with sp d (z, xy,xz) or sp d (x - y, .yy,j z) hybridization. Note that the choice... 

Coordination number six appears, from the limited available data, the most common (Table 7). Lower coordination numbers are known but appear to be fairly rare three is represented by some silylamides (Section 41.3.3.1) and in a dehydrated zeolite (Section 41.3.5.2.i) four-planar is known only for macrocyclic [N,] systems and as [MnOJ in a few unusual crystalline compounds and four-tetrahedral is well characterized but still apparently less common than for Zn, Co and possibly even Ni. Coordination number five is also known, but few examples are yet characterized. On the other hand, higher coordination numbers seven and eight are less unusual here—hardly surprising in view of the larger size of Mn". Examples include seven coordinate [Mn(edta)H20] (Section 41.3.9), [Mn(py3tren)] (Section 41.3.3.6) and an [Mn07] species (Section 41.3.5.3.iii), and eight coordinate [Mn(04)2] species (Section 41.3.5.4). 

Figure 11. The crystal structure of Pb°-EDTA contains both a monomeric form and a dimeric form of the compound (170, 203). The monomeric form (a) has coordination number seven with oxygen from a coordinated water providing the seventh donor ligand. The dimeric form (h) has a coordination number eight with the eighth ligand provided by an oxygen from a carboxylate group from an adjoining molecule. Coordinates downloaded from the CSD.

Complexes oe 3d Metaes with Coordination Number Seven and Macrocyceic 2,6-Diacetyepyridine and Some Reeated... 

Each of the iron atoms in diiron nonacarbonyl has three terminal carbonyl groups, as shown in Figure 20. The remaining three carbon monoxide ligands act as P2 CC) groups. In addition to this, there is a weak Fe—Fe bond (2.46 A) formed by the sharing of two unpaired electrons present in the 3d orbitals of iron atoms. Thus, both of the iron atoms in the molecule are identical with coordination number seven. Since the molecule does not have any unpaired electrons, it is diamagnetic. 

The knowledge of d( Sn) chemical shifts is very important for predicting the geometry of coordination polyhedra of tin compounds in solution. In the case of tetravalent tin compounds, an increase in tin coordination number from four to five corresponds to an increase in tin shielding by -150-200 ppm. Similar increases are generally associated with six and seven coordination. The (5( Sn) for PhSn(edtc)2Br [2], a hexacoordinate pseudooctahedral tin complex, is -704.1 ppm, whereas d( Sn) for PhSn(edtc)3 [3] in which the central Sn has coordination number seven and the shape is distorted pentagonal bipyra-midal is -806.5 ppm. 

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