In Pursuit of the Molybdenum(III) Tris(thiolate) Fragment:  Unusual Structure of a Dimolybdenum μ-Nitrido Complex

Abstract

The new molybdenum nitrido−thiolate complex N⋮Mo(SAd)_3 (Ad = 1-adamantyl) was prepared by a ligand exchange route involving reaction of Ti(SAd)(O^(i)Pr)_3 with Chisholm's nitrido−butoxide complex N⋮Mo(O^(t)Bu)_3. In an effort to abstract the nitrido nitrogen from N⋮Mo(SAd)_3, the compound was treated with Mo(N[^(t)Bu]Ph)_3, a three-coordinate molybdenum(III) complex. This resulted in formation of the unusual and thermally unstable (μ-nitrido)dimolybdenum complex (AdS)_3Mo(μ-N)Mo(N[^(t)Bu]Ph)_3, which was isolated and characterized. An X-ray study revealed (AdS)_3Mo(μ-N)Mo(N[^(t)Bu]Ph)_3 to possess an unsymmetrical Mo−(μ-N)−Mo linkage, the Mo−thiolate fragment exhibiting a substantially longer bond to the bridging nitrogen atom. The structure of (AdS)_3Mo(μ-N)Mo(N[^(t)Bu]Ph)_3 is noteworthy, displaying trigonal monopyramidal coordination at the (μ-N)−Mo−thiolate Mo center. Since N⋮Mo(N[^(t)Bu]Ph)_3 is a good leaving group, (AdS)_3Mo(μ-N)Mo(N[^(t)Bu]Ph)_3 should be a source of the reactive Mo(SAd)_3 fragment. In all the studied reactions of the (μ-nitrido)dimolybdenum complex one of the observed products was N⋮Mo(N[^(t)Bu]Ph)_3. Two products containing the Mo(SAd)_3 fragment were observed:  (AdS)_3Mo⋮Mo(SAd)_3 and [(ON)Mo(μ-SAd)(SAd)_2]_2. Upon treatment with pyridine, the tris(thio-1-adamantyl)(nitrosyl)molybdenum dimer forms the pyridine adduct (AdS)_3Mo(NO)(py), which is a monomer.