Insertion of CS<SUB>2</SUB> into a metal acetylide bond and conversion of the bonding mode of S<SUB>2</SUB>CC&#8801;CPh from &#951;<SUP>2</SUP> to &#951;<SUP>3</SUP>

Photolysis of a benzene solution containing [(L)Mo(CO)3(C&#8801;CPh)] (L=&#951;5-C5H5 1; &#951;5-C5Me5 2) and CS2 leads to the formation of dithiopropiolato containing complexes, [(L)Mo(CO)2(&#951;2-S2CC&#8801;CPh)] (L=&#951;5-C5H5 4; L=&#951;5-C5Me5 5). In presence of air, [(&#951;5-C5H5)Mo(CO)3(C&#8801;CPh)] reacts with CS2 to give 4 as the major and [(&#951;5-C5H5)Mo(O)(&#951;3-S2CC&#8801;CPh)] (6) as minor products. Similarly, [(&#951;5-C5Me5)Mo(CO)3(C&#8801;CPh)] reacts with CS2 under aerobic conditions to give compound 5 along with [(&#951;5-C5Me5)Mo(O)(&#951;3-S2CC&#8801;CPh)] (7) as minor product. When solutions of 4 or 5 are photolysed under a constant purge of air, 4 gives 6, and 5 gives 7 in high yields. Room temperature stirring of 5 with [W(CO)5(THF)] forms [&#951;5-C5Me5)Mo(CO)2CS2{W(CO)5}2C&#8801;CPh] (9). All new compounds have been characterised by IR and 1H-NMR spectroscopy and the structures of 4, 6, 7 and 9 have been established crystallographically