New trans-[Fe(cyclam) (C equivalent to CR)(2)]OTf compounds 2a/2b [cyclam = 1,4,8,11-tetraazacyclotetradecane, R = (SiPr3)-Pr-i (a) or Ph (b), and OTf= trifluoromethanesulfonate] were prepared from the reaction between trans-[Fe(cyclam)(OTf)(2)]OTf(1) and LiC equivalent to CR. The trans arrangement of the acetylide ligands in 2 was established from the X-ray diffraction study of 2a, and the density functional theory calculations revealed significant d pi-pi(C equivalent to C) interactions.