The structural chemistry of cobalt

Group VIII and Other Transition Metals The structural chemistry of cobalt The stereochemistry of cobalt (ll)-d  

We have to discuss the spatial arrangement of 4, 5, or 6 bonds. At one time many deductions of bond arrangements were made from magnetic moments, which would be expected to have the following (spin-only) values  

Square coplanar bonds are formed only in complexes with certain polydentate ligands or combinations of ligands such that steric factors prevent a tetrahedral configuration. They include the phthalocyanine (low-spin), the bis-salicylaldehyde diimine complex (a) (in which the maximum deviation of any atom from the mean plane of the complex is 0 6 A and Co-O(N) is 1-85 A), and the ion (b) in the salt [Co(mnt)2] [N(C4H9)4] 2. The magnetic moment of this salt (3-92 BM) corresponds to 3 unpaired electrons (d ). The Ni((ii) compound is isostructural. Ions [M(mnt)2] are formed by Ni(m) and Cu(iii). The similar ion formed by 

Co(iii) and the ligand (c) has a magnetic moment of 3T8 BM, slightly higher than the spin-only value for 2 unpaired electrons (d ) it also is planar.  

The planar molecule rra s-Co(PEt2 0] 2(mesityl)2 is an example of a spin-paired d complex with monodentate ligands. 

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