Tantalum dihydrogen complexes

In the case of the tantalum complexes 100, reversible hydrogen migration may occur at room temperature in the presence of carbon monoxide, or at 70°C with dihydrogen or dimethylphosphino ethane to afford complexes 106, 107, and 108, respectively.92,95 In contrast, the phosphametallacycle remains intact when 100 is treated with halogenated reagents such as CH3X (X = Cl, Br, I).92,95... 

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... 

In summary, the tantalum hydride system adds to the few previously reported well-defined organometallic complexes capable of cleaving N-H bonds of ammonia to yield either an amido or an imido complex, and achieves unprecedented dinitrogen N=N triple bond cleavage with dihydrogen on isolated tantalum atoms to yield reduction of both N atoms. 

Lewis base complexes, 83 Dichromates, 941, 943 Dihydrogen oxidative addition niobium(II) complexes, 678 niobium(III) complexes, 660 tantalum(II) complexes, 678 tantalum(III) complexes, 660... 

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