Hydridopentacarbonylrhenium reacts with 3,3,3-trifluoropropyne to give cis-CF3·CH:CH·Re(CO)5 as principal product. The hydride HFe(CO)2(π-C5H5) affords a mixture of cis-CF3·CH:CH·Fe(CO)2(π-C5H5) and CH2:C(CF3)·Fe(CO)2(π-C5H5), in which the latter predominates: while trans-(Et3P)2Pt(H)Cl affords cis-(Et3P)2Pt(C(CF3):CH2)Cl. Reaction between hydridopentacarbonylmaganese and the acetylene gives a mixture of CH2:C(CF3)·Mn(CO)5 and a tetracarbonyl complex, in larger yield, believed to have a cyclic structure (OC)4M[graphic omitted]. Methylpentacarbonylmanganese reacts to give apparently a similar tetracarbonyl manganese complex. Reactions between 3,3,3-trifluoropropynne and (Ph3P)4Pt or (π-C5H5)2Ni afford (Ph3P)2Pt(CF3·C2H) and [π-C5H5Ni]2(CF3·C2H), respectively. Cobaltocene gives [π-C5H5]Co[π-C5H5(CCCF3)]. The reaction between octacarbonyldicobalt and the alkyne has also been studied and the complexes (CF3·C2H)Co2(CO)6 CF3·CH2·C[Co(CO)3]3 and (CF3·C2H)3Co2(CO)4 isolated.