Addition of Propargyl Groups to [Fe2(CO)6(μ-E2)] (E=S, Se, Te) and Reactions of(left[ {Fe_2 left( {CO} ight)_6 left( {mu - ECH_2 C equiv CH} ight)_2 } ight]left( {E = S,Se} ight))with Co2(CO)8; Crystal Structures of(left[ {Fe_2 left( {CO} ight)_6 left( {mu - SeCH_2 C equiv CH} ight)_2 } ight],left[ {Fe_2 left( {CO} ight)_6 left{ {left( {mu - SCH_2 C = CH} ight)Co_2 left( {Co} ight)_6 } ight}_2 } ight])and(left[ {Fe_2 left( {CO} ight)_6 left{ {left( {mu - SeCH_2 C = CH} ight)Co_2 left( {Co} ight)_6 } ight}_2 } ight])