The mononuclear vinylidene complexes of the type Mn(C5H 4R′)(R″2PCH2CH2PR″ 2)(=C= C(R1)(SnMe3)) were obtained by the reaction of Mn(C5H4R′)(η6- cycloheptatriene) (R′ = H, 1a; CH3, 1b) with 1 equiv of R 1-C≡C - SnMe3 (R1 = SnMe3, C6H5, C4H3S, C6H 4CH3) and R″2PCH2CH 2PR″2 (R″ = CH3 (dmpe), C 2H5 (dmpe)) in toluene at 50°C for 3 h. The reactions of these tin-substituted complexes with 1 equiv of 1.0 M TBAF yielded the corresponding parent vinylidene species Mn(C5H4R′) (R″2PCH2CH2PR″2)(=C= C(R1)(H)). Treatment of some of these vinylidene species with 1 equiv of [Cp2Fe] [PF6] led to the oxidative coupling product [(C5H4R′)(R″2PCH2CH 2PR′2)Mn≡C-CHR1-CHR 1-C≡Mn(R″2PCH2CH 2PR″2)(C5H4R″)]-[PF 6]2 (R′ = CH3) R″ = CH3, R1 = H; R′ = CH3, R″ = CH3, R1 = C6H5; R′ = CH3, R″ = CH 3, R1 = C4H3S; R′ = H, R″ = C2H5, R1 = H; R′ = H, R″ = C2H5, R1 = C6H5; R′ = H, R″ = C2H5, R1 = C 4H3S). In some cases these products of oxidative coupling, [(C5H4R′)(R″2PCH 2CH2-PR″2)Mn≡C-CHR 1-CHR1-C≡Mn(R″2PCH 2CH2PR″2)(C5H 4R′)] [PF6]2 were accompanied by formation of dinuclear complexes of the type [(C5H 4R′(R″2PCH2CH2PR″ 2)Mn≡C-CR1=CR1- C≡Mn(R″2PCH2CH2PR″ 2(C2H4R′)][PF6]2 and of the cationic carbyne complexes [(C5H4R′) (R″2PCH2CH2PR″2) Mn≡C-CH2R1] [PF5] obtained by proton transfer. Reduction of these dinuclear complexes with Cp2*Co yielded back the corresponding mononuclear precursor complexes involving a reductive decoupling process. Both the reductive coupling and the oxidative coupling are fully reversible, which is supported by DFT calculations. The mononuclear and the dinuclear compounds were characterized by NMR, IR, and cyclic voltammetric studies. X-ray diffraction studies have been performed on complexes 3a, 11, 13a, 15a, and 22b.