The compounds [Mo(NPh)(eta (2)-olefin){o-(Me3SiN)(2)C6H4}] (olefin = propene 1a or isobutene 1b) react with excess pyridine affording the Mo(iv) bis-pyridine complex, [Mo(NPh)(Py)(2){o-(Me3SiN)(2)C6H4}] 2 which when heated to 90 degreesC in toluene undergoes a C-N bond cleavage reaction and is converted to 3, a bimetallic molybdenum species; the crystal structures of both 2 and 3 are reported.