Ligands dihydrogen, displacement

Oxidative addition of dihydrogen to an unsaturated complex can, on occasion, lead to ligand displacement to further allow hydrogen addition to the complex . 

Scheme 8 Displacement of two dihydrogen ligands by the borane H2BMes to form K complex 31. ...

Green et al. observed that the tantalum complex 101 is converted into the bicyclic complex 109 after prolonged exposure to sodium and trimethyl-phosphine.930 Two phosphine ligands of 101 are easily displaced by butadiene, affording the complex 110, while treatment of 109 with dihydrogen leads to the reduction of the metallic center. In both cases, the metallacycle remains intact.930... 

Nitrogen complexes are usually made by reduction of halides or halide complexes with other ligands using sodium amalgam81 or other chemical reductants in an atmosphere of N2. They can also be made by displacement of rf-H2 in dihydrogen compounds (Section 2-16) by N2ffi representative syntheses are as follows ... 

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