Fluxional phosphine complexes

The concept of dynamic NMR and in particular stereochemical nonrigidity has been dealt with previously by many authors. A recent volume [219] contains a section relevant to phosphine complexes and is therefore especially noteworthy however, as we have just introduced a five coordinate potentially fluxional system in which the... 

Phosphorus-31 NMR has also been employed in identifying fluxionalities of various metal phosphine complexes. Bis- and tris-(ether phosphine) ruthenium(II) chloro and acetato complexes exhibit exchange between the... 

The hydride complexes [MoH(CO)2(chel)2]+ (chel = variety of chelating diphosphines and arsines) are prepared by protonation of the parent Mo° dicarbonyls and appear to have a monocapped octahedral structure in solution, with the fluxional hydride moving around the possible capping positions. This process has been extensively studied by NMR.65 A number of other cationic seven-coordinate analogues [MoX(CO)2(chel)2]+ (X = halide or pseudohalide chel = chelating ligand usually phosphine or arsine) are also known (Table 5).la... 

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