Octahedral geometry cadmium

One unexpected square planar complex [Cd(OAr)2(thf)2] (Fig. 12.4) has recently been reported.13 It is the first example in this geomelry for d10 Cd2. Inasmuch as a closely related complex of the smaller zinc ion, [Zn(OAr )2(thf)2], has distorted tetrahedral geometry,14 simple steric factors cannot account for the pseudo-C2/i symmetry of the cadmium complex, though to be sure, the steric relaxation of the target metal atom and the perpendicular planes of the thf and phenoxide rings are nicely accommodated by it. Furthermore, octahedral geometry would rot be unusual in ad10... 

An X-ray spectroscopic study of aqueous solutions of cadmium-en complexes has shown that, like their zinc(II) counterparts, the ions [Cd(en)2]2+ and rCd(en)3]2+, respectively, involve a tetrahedral and an octahedral geometry at the metal atom.175... 

The crystal structure of [Cd(GlyGly)(Im)Cl] has been reported72 and shown to involve dimeric units with a distorted octahedral geometry about each metal atom this complex has also been studied in a 13C NMR investigation of a range of nucleoside and peptide complexes of cadmium(II).430... 

As expected, the majority of zinc compounds have the metal in tetrahedral co-ordination, whUst those of cadmium adopt mostly octahedral geometry. Exceptions do occur in each case, however. 

Both 2,2 -bpy, 1,10-phen, and their derivatives bind to both zinc (551, 591, 1158, 1906-1909, 1914, 1918, 1919, 1923, 1936-1939) and cadmium (1924-1930) in a bidentate manner leading to the generation of six-coordinate centers, with a distorted octahedral geometry. An elongation of the zinc-sulfur bonds by 0.2 A when compared to simple bis(dithiocarbamate) complexes is probably due to steric rather than electronic factors (1906), although binding of the base does result in an increase of electron density on zinc as shown by electrochemical and XPS studies (551, 552). 

In both, the cadmium(II) S-methyl-cysteine and methionine systems, mono-, bis-, and tris(ligand) complexes are formed corresponding to the six-coordinated octahedral geometry of cadmium(II). Although the corresponding zinc(ll) complexes... 

The other general characteristic feature of cadmium(ll) complexes with thiol derivatives is the formation of di- or trinuclear species, in which thiol sulfur atoms behave as bridging ligands. The existence of polynuclear species was observed in nickel(ll)- and zinc(ll)-cysteine systems with similar stoichiometry, but cadmium(ll) complexes have usually an octahedral geometry, while in the nickel(ll) complexes this coordination mode results in four-coordinated square planar complexes. 

X-Ray structural determinations on [(2,2 6, 2"-terpyridyl)Cd Mn(CO)5 2] and [Hg Mn(CO)5)2] have been reported. The former has distorted trigonal-bipyramidal geometry at the cadmium atom and shows considerable distortion of the octahedral co-ordination around the manganese atoms, and the latter contains a linear Mn—Hg—Mn system, the Mn(CO)5 groups being eclipsed. The complexes [X In Mn(CO)5)3 J (X = Cl or Bf n = 0—2) have been prepared and studied in detail. The indium-manganese bonds are readily... 

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