Arsine pseudohalide

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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