Experimental and Computational Studies on Quadruply Bonded Dimolybdenum Complexes with Terminal and Bridging Hydride Ligands.

This contribution focuses on complex [Mo (H) (μ-Ad ) ] (1) and tetrahydrofuran and pyridine adducts [Mo (H) (μ-Ad ) (L) ] (1⋅thf and 1⋅py), which contain a trans-(H)Mo≣Mo(H) core (Ad =HC(NDipp ) ; Dipp=2,6-iPr C H ). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo H unit of 1, with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe , can bind to 1, causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond (2⋅PMe ). A DFT analysis of the terminal and bridging hydride coordination to the Mo≣Mo bond is also reported, along with reactivity studies of the Mo-H bonds of these complexes. Reactions investigated include oxidation of 1⋅thf by silver triflimidate, AgNTf , to afford a monohydride [Mo (μ-H)(μ-NTf )(μ-Ad ) ] (4), with an O,O'-bridging triflimidate ligand.