Metal Carbonyl Derivatives Containing Phosphorus Donor Ligands

METAL CARBONYL DERIVATIVES CONTAINING PHOSPHORUS DONOR LIGANDS 

This class of compounds is conveniently investigated by CP/MAS NMR spectroscopy ( P, /= 1/2, 100% nat. ab.). The general considerations on the advantages of using solid state NMR described above for may be extended to P NMR. Furthermore, additional information is usually provided by the determination of the coordination shift [52] (i.e the difference between the solid state chemical shifts of free and coordinated P donor atoms). 

In the solid state spectra the chemical shift separation between the two resonances is 9.3 ppm, 2.7 ppm and very small, for CIO, BF4 and PF counterions, respectively. This is the result of minor differences in the geometry of the phosphorus atoms in the three solids with respect to the applied magnetic held as a consequence of the steric and electronic requirements of the counterions. Furthermore it was observed that y( Rh, P) coupling constants are highly sensitive probes for the changes in the counterions, which affect to a different extent the distorsion of the square-planar stereochemistry around Rh (Table 4). 

From these considerations it is clear that the solid state NMR information can be potentially useful for the evaluation of the bond angles in other related systems where X-ray data are not available. Furthermore, the knowledge by SSB analysis of the csa of phosphorus can be useful in the elucidation of the different relaxation mechanisms involved in the relaxation processes of these compounds in solution [56]. 

As for liquids, scalar coupling constants can be directly observed in solids only if the nuclei involved in the coupling have sufficiently long relaxation times, i.e. 

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Two significant surveys are published in the sane edition of Coordination Chemistry Reviews. Oxygen donor-ligand derivatives of tri-osmium dodecacarbonyl are covered by Frauenhoff and the reactions of transition metal dihydrogen complexes (of which many are carbonyl-containing) are outlined by Jessop and Morris. The crucial role of matrix Isolation studies is well covered in this article. A shorter review of interest here has been published on the role of the phosphorus d-orbitals in M-P bonding. ... 

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