Reactivity of [Mo(CO)3(NCMe)3] towards pyrimidine-2-thiol (pymSH) and thiophenol (PhSH) in the presence of phosphine auxiliaries: Synthesis of mono- and dinuclear complexes bearing κ2 and µ,κ2-pymS coordination motifs

The reaction of [Mo(CO)3(NCMe)3] with added thiol in the presence of a phosphine auxiliary has been investigated. Treatment of [Mo(CO)3(NCMe)3] with pyrimidine-2-thiol (pymSH) and PPh3 at 60 °C in MeCN afforded the known mononuclear compounds cis-[Mo(CO)4(PPh3)2] (1) and [Mo(к2-pymS)4] (2), and the new binuclear compound [Mo2(CO)4(μ,к2-pymS)2(PPh3)2] (3), which possesses idealized C2 symmetry. A different product distribution was found when dppm was employed as the phosphine ligand. Of the five reaction products isolated, three consisted of mononuclear compounds, [Mo(CO)4(к2-dppm)] (4), [Mo(CO)3(κ2-dppm)(κ1-dppm)] (5) and [Mo(CO)(к2-pymS)2(к2-dppm)] (6), with the remaining two products corresponding to dinuclear compounds, [Mo2(CO)6(μ,к1-pymS)2(μ,к2-dppm)] (7) and [Mo2(CO)4(μ,к2-pymS)2(к2-dppm)] (8). Products 6–8 are new and have been fully characterized in solution by IR and NMR spectroscopy, and by X-ray crystallography in the case of 6 and 7. The reaction of [Mo(CO)3(NCMe)3] with PhSH and dppm at 60 °C in MeCN was also examined to assess the effect of thiol on the product distribution. The two principal products isolated were identified as the mononuclear compound [Mo(CO)2(κ1-PhS)2(κ2-dppm)] (9) and the dinuclear compound [Mo2(CO)6(μ,κ1-PhS)2(μ,κ2-dppm)] (10). The bonding in compounds 3, 6 and 7 was also examined by DFT, and highlights between the computational and experimental structures are discussed.