The interactions of NH3 with the transition metal complexes M(NH3)n+ (M=Fe, Ru, Os; n=0−4) were investigated theoretically with the aim of analyzing the factors that determine their reactivity patterns and product distributions. The reactions of ammonia with the low‐coordination complexes of the three metallic ions (n=1−3) lead only to the addition product M(NH3)n+1+. However, once the highest‐coordinated complex M(NH3)4+ is reached, each of the reactions evolves to metal‐inserted species through low energy channels. For osmium, the hydrogen abstraction from an additional NH3 molecule by the inserted intermediate H−Os(NH3)4‐NH2+ leads to H2 elimination products along a favorable pathway. The facile breaking of the strong N−H bond of ammonia by these Werner‐type complexes is by far the most striking finding emerging from this study. Hopefully, this could inspire future contributions in the areas of chemical and bioinorganic catalysis.

Energy profiles for the lowest lying triplet and singlet electronic pathways that link the reactants Zr + CHCH with the products observed under matrix-isolation conditions were obtained from DFT and CASSCF-MRMP2 calculations. The insertion of the metal into the C-H bond of the organic molecule to yield the oxidative addition product is not favorable for any of the investigated channels. However, the inserted structure H-Zr-CHCH can be obtained from two sequential reactions involving the radical species ZrH and CHCH. According to this scheme, a first reaction produces the radical fragments from the ground state of the reactants. Then, the radicals can recombine themselves in a second reaction to form the inserted species H-Zr-CHCH. As the triplet and singlet radical asymptotes ZrH + CHCH that vary only in spin of the non-metallic fragment are degenerate, the rebounding of the radicals can occur through both multiplicity channels. It is shown that the low spin channel leads to the most stable structures of the dihydride ZrH-(CH) and the vinyl metal trihydride complexes ZrH-CH=CH experimentally determined for this reaction under matrix-isolation conditions. The description attained for this interaction does not invoke interactions between the triplet and singlet electronic states emerging from the reactants, as proposed by other authors.

The sequential addition of NH3 molecules to Zr+ and Re+ was investigated through CASSCF-CASPT2 calculations with the aim to analyze the effect of the metal-ligand interactions on the potential of...