Reaction of KPPh 2 and Br(CH 2 ) 5 CHCH 2 gives the phosphine PPh 2 (CH 2 ) 5 CHCH 2 (89%), which is treated with the platinum tetrahydrothiophene complex [Pt(μ-Cl)(C 6 F 5 )(S(CH 2 CH 2 –) 2 )] 2 to yield trans-(Cl)(C 6 F 5 )Pt(PPh 2 (CH 2 ) 5 CHCH 2 ) 2 (4b, 80%). Ring-closing alkene metathesis (Grubbs’ catalyst) gives (5b, 84%), which features a trans-spanning diphosphine ligand. The Z/E CC mixture is hydrogenated (1atm, 10% Pd/C) to give (6b, 99%). The crystal structures of 4b and (Z)-5b are determined. In the former, both (CH 2 ) 5 CHCH 2 moieties are directed on the same side of the platinum square plane. Low temperature 13 C NMR spectra of 6b show two sets of signals for the diastereotopic PPh 2 groups. These coalesce upon warming, which requires the passage of the chloride ligand through the macrocycle. Analysis by the complete bandwidth method gives ΔH ‡ and ΔS ‡ values of 6.0±0.4kcalmol −1 and −13.9±2.6eu. The 31 P, 13 C, and 2 H CP/MAS NMR spectra of polycrystalline 6b and 6b-d 2 are studied, and indicate appreciable conformational mobility of the methylene chain in the solid state.