When is metal-centered pseudocontact shift expected

When is metal-centered pseudocontact shift expected  

31P contact shifts in ligands coordinating through P-O moieties in oxovana-dium(IV), cobalt(II) and nickel(II) complexes are downfield and of the order of 103 ppm [69-71]. Smaller downfield shifts are observed for nickel-coordinated P-S moieties [72]. Direct P-M coordination gives rise to even larger hyperfine coupling than in P-O moieties. In low spin cobalt(H) complexes A/h values of the order of 102 MHz are found [73]. 

6 WHEN IS METAL-CENTERED PSEUDOCONTACT SHIFT EXPECTED  

Pseudocontact shift is expected every time there are energy levels close to the ground state. This causes orbital contributions to the ground state, and such contributions are orientation dependent. Therefore, the magnetic susceptibility tensor is anisotropic. Anisotropy of the magnetic susceptibility tensors arises also from sizable ZFS of the S manifold (Section 1.4). 

Hyperfine ( hyp) and pseudocontact (S1 ) shifts of the H and 13C nuclei of pyridine bis-coordinated to cobalt(II) bis-acetylacetonate [74] 

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