The stereochemistry of Ti iv in some finite complexes

Examples of 5-coordination include the square pyramidal anion (c) in (TiCl40)(NEt4)2, which is isostructural with the corresponding V compound, and the bridged molecule (d), in which the coordination is described as close to 

We noted above the acetylacetone complexes Ti(acac)2Cl2 and [Ti(acac)3] . In the orange-yellow Ti2Cl20(acac)4, which crystallizes with one molecule of 

The structural chemistry of V in various oxidation states (ii-v) in binary compounds has been noted in previous chapters, in particular the unusual coordination of V(v) by oxygen in oxides and oxy-salts, where there is very irregular square pyramidal or octahedral coordination (in addition to tetrahedral coordination). Our chief concern here is with compounds of V(iv), but we shall mention incidentally several complexes of V(iii) and V(v). 

0 neighbours in these complexes is similar to V-0 (1-98 A) in V (acac)3/ a compound that is readily oxidized to VO(acac)2. We have included in the Table examples of complexes containing mono-, bi-, and quadri-dentate ligands the skeleton of the ligand acen is shown in Fig. 27.2(b). The divanadyl-d/-tartrate ion has an interesting structure containing two V atoms, both of which form square pyramidal bonds (Fig. 27.2(c)). 

We comment elsewhere on the rarity of trigonal prism coordination, which has been observed in complexes M(S2C202)3 iti which M is V, Cr, Mo, or Re. In the V complex V-S = 2-34 A and S-V-S = 82° (mean), and the shortest distances between S atoms of different ligands are close to 3T A tlie dimensions of the Re and Mo complexes are almost identical to those of the V complex. It has been suggested that some type of weak interaction between the S atoms stabilizes this 

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