Reactions of Fe(CO) 3 (η 4 -benzylideneacetone) and PhP((CH 2 ) m CHCH 2 ) 2 (m = a, 4; b, 5; c, 6) give trans-Fe(CO) 3 (PhP((CH 2 ) m CHCH 2 ) 2 ) 2 (2a−c, 28−70%), which are treated with Grubbs' catalyst (15 mol %; refluxing CH 2 Cl 2 ). NMR analyses of the crude interligand metathesis products trans-Fe(CO) 3 (PhP((CH 2 ) m CHCH(CH 2 ) m ) 2 PPh) (3a−c, 30−31%) suggest Z/E CC mixtures and/or byproducts from intraligand metathesis or oligomers. Subsequent hydrogenations (5 bar/cat. Rh(Cl)(PPh 3 ) 3 or PtO 2 ) afford trans-Fe(CO) 3 (PhP((CH 2 ) n ) 2 PPh) (4a−c, 69−77%; n = 2m + 2, synperiplanar phenyl groups), which density functional theory calculations show to be more stable than isomers derived from other metathesis modes. Crystallizations give (E,E)-3a and 4b, the X-ray structures of which are determined and analyzed. Variable-temperature 13 C{ 1 H} NMR experiments show that rotation of the Fe(CO) 3 moiety in 4b is rapid on the NMR time scale (RT to 0 °C; ΔG ⧧ 273 K ≤ 12.8 kcal/mol), but that in 4a is not (RT to 105 °C; ΔG ⧧ 378 K ≥ 17.9 kcal/mol). These data indicate rotational barriers lower than those in analogues in which three methylene chains connect the phosphorus atoms, trans-Fe(CO) 3 (P((CH 2 ) n ) 3 P).