Pseudooctahedral coordination

Figure 13.11 Structure of the binuclear anion [Sbj OCle] " showing the bridging oxygen and chlorine atoms and the pseudooctahedral coordination about Sb the O atom is at the common apex of the face-shared square pyramids and the lone-pairs are trans- to this below the SbCU bases. The bridging distances Sb-Cl are substantially longer than the terminal distances Sb-Cl,.

Pseudooctahedral coordination of rhenium(III) centers has also been found for mixed-ligand complexes with tertiary phosphines and A-heterocyclic thiols which coordinate as their neutral thione tautomers. A representative example with thiazoline-2-thiol (HSthiaz) has been characterized structurally. The paramagnetic complex [ReCl3(HSthiaz)2(PPh3)] (235) contains the HSthiaz ligands in trans position. ... 

The pentacoordinated indium(m) compound 13 has a quasi-square-pyramidal environment rather than trigonal bipyramidal with a short indium-axial iodine bond distance (2.713 A) as compared to those in equatorial positions (2.780 A) <1998EJI203>. An example of pseudooctahedral coordination around an indium(m) center can be given by the [(bipy)InCl(SC 0 Ph)2] structure in which the indium center is coordinated to a planar bipyridine ligand, a chloride ion, and two thiobenzoate anions <2002MI467>. Of the latter, one thiobenzoate ligand binds in a bidentate fashion, while the other is bonded mainly through the sulfur atom. 

Only one example for the transition metal complex 75 coordinated to an arsetane is known now <19950M1434>. This compound was synthesized in a similar manner as the phosphorus analogue 74. The structure of 75 was confirmed by X-ray crystallographic analysis revealing a pseudooctahedral coordination environment around iron. The Fe-As bond is similar to that in [(r 5-C5H5)(CO)2Fe(AsPh3)]BF4 (Figure 14). 

So far, we have confined our discussion to compounds Ms[M (CN)6]r where the metal ion M- is octahedrally or pseudooctahedrally coordinated. The ambident linkage of the cyanide ion is a decisive structural element also in silver hexacyanometalates, Agj M (CN)6, where the silver ion is linearly coordinated by two nitrogen atoms 59), A similar structural behavior is exhibited by hydrogen. N—H—N groups are found in the lattices of several cyanometal acids of the general formula HfcMB(CN)e 29, 60, 61). 

Fig. 6. Coordination about one, (Na- )+, of two independent Na cations of Na2Fe(CO)4 fC4H802, emphasizing the I —CO— interaction of four [Fe(CO)4]2 units with the (Na-1)+ center. Two C4Hs02 molecules complete the pseudooctahedral coordination about the cation. [By permission from the American Chemical Society, H. B. Chin and R. Bau, J. Am. Chem. Soc. 98, 2434 (1976).]...

Reduction reactions that involve titanium(lll) species are common in preparative organic chemistryl 9 but relatively rare in coordination chemistry. However, Floriani and coworkers " have described the reduction of vanadium complexes, [VO(salophen)] and [VO(acacen)], by the titanium(IIl) solvento-complex, [TiCl3(THF)3]. Reaction of these vanadyl complexes in THF results in formation of [VCl(salophen)(THF)] and [VCl(acacen)(THF)]. Both compounds have been structurally characterized and an X-ray diffraction study of [VCl(salophen)(THF)] indicated pseudooctahedral coordination for V(Ill). Further, the CP and THF ligands were found to be trans to each other in the axial positions, while the equatorial plane was defined by the salophen ligand. Figure 9.7.1fl The proposed mechanism 2 for these conversions is shown in Scheme 9.7. 

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