Tetrahedral complexes configuration

Tetrahedral complexes arc also common, being formed more readily with cobali(II) than with the cation of any other truly transitional element (i.e. excluding Zn ). This is consistent with the CFSEs of the two stereochemistries (Table 26.6). Quantitative comparisons between the values given for CFSE(oct) and CFSE(let) are not possible because of course tbc crystal field splittings, Ao and A, differ. Nor is the CFSE by any means the most important factor in determining the stability of a complex. Nevertheless, where other factors are comparable, it can have a decisive effect and it is apparent that no configuration is more favourable than d to the adoption of a tetrahedral as opposed to... 

The next most common coordination number is 4. Two shapes are typically found for this coordination number. In a tetrahedral complex, the four ligands are found at the vertices of a tetrahedron, as in the tetrachlorocobaltate(ll) ion, [CoCl4]2 (2). An alternative arrangement, most notably for atoms and ions with ds electron configurations such as Pt2+ and Au +, is for the ligands to lie at the corners of a square, giving a square planar complex (3). 

Would Jahn-Teller distortion be as significant for tetrahedral complexes as it is for octahedral complexes For which of the electron configurations would Jahn-Teller distortion occur ... 

The preparation, and even more the resolution, of an asymmetric tetrahedral center in Werner-type complexes has been thwarted by the configurational instability of tetrahedral complexes. However the use of ligands of the strongly a, 7t bonding type imposes stability and the forma-... 

In tetrahedral symmetry, the d9 configuration has three orbital levels lowest as does d1 in octahedral symmetry. The similarity between the g values for tetrahedral and distorted octahedral symmetry indicates that the distortion in tetrahedral complexes of Cu2+ is large and leaves the unpaired electron in the (x2 — y2) orbital. In tetrahedral symmetry, 4p orbitals have the same symmetry as the d orbitals, and thus there can be a mixing of 4p and 3d orbitals. Sharnoff (281) has estimated from the spin Hamiltonian of CuClJ- that the unpaired electron is in an orbital that is 70 per cent 3d9 12 per cent 4p, 17 per cent 3p of Cl, and 1.3 per cent 3s of Cl. 

Only octahedral complexes have been discussed, mainly because much less is known about conformational effects in other configurations. In some tetrahedral complexes, for example, [Be(OCH2CH20)2]2 or [B(OCH2 CH20)2]-, the ligands may be sufficiently inert to dissociation to be examined with respect to their stereochemistry. Similar remarks apply to planar and other structures. 

Table 11.17 summarizes this information for weak field octahedral and tetrahedral complexes. Octahedral complexes having d1. d. d. and d9 configurations and weak field ligands should each give one absorption corresponding to A,r Configurations dz, d. d7, and d in weak octahedral fields each have three spin allowed transitions. (In each case is the energy difference between adjacent A2l, and terms.) As we have... 

The spherically symmetric dll) configuration affords no LFSE, so the preferred coordination is determined by other factors. For Cu(l) the preferred coordination appears to be linear ( p), two-coordination, although three-coordinate complexes are known as well as several tetrahedral complexes. Zinc(Il) is typically either tetrahedral (e.g., [ZnCl4J2-) or octahedral (e.g., [Zn(H20)6]2 ), but both trigonal bipyramidal and... 

Thioacetamide, MeC(=S)NH2 (taa), is isoelectronic with thiourea which it resembles by acting as a unidentate S-donor ligand. Thiobenzamide, PhC(=S)NH2 (tba), behaves similarly. Both thioamides form stable complexes with (b) class and borderline metals. Thioacetamide forms the tetrahedral complexes [MX2(taa)2] (M = Fe, Co, Zn X = Cl, Br, I, NCS).47,153-157 The v(M—S) frequency is rather low, ranging from 255 to 230cm, .14s The Mossbauer spectra of FeX2(taa)2 PC = Cl, Br) are consistent with a tetrahedral configuration.158... 

To illustrate the relationship between geometry and hybridization, let s consider the tetrahedral complex [CoCl4]2-. A free Co2+ ion has the electron configuration [Ar] 3d7, and its orbital diagram is... 

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