Treatment of freshly made 1,4-diethynylnaphthalene with Cp*(dppe)FeCl in the presence of either NaPF 6 or NaBPh 4 salts provides the new binuclear organoiron bis(vinylidenes) [Cp*(dppe)FedCdCH-1,4-nph-CHdCdFe(dppe)Cp*][X] 2 (X=BPh 4 , PF 6 , Nph=naphthalenediyl, Cp*=η 5 -C 5 Me 5 , dppe= 1,2-bis(diphenylphosphino)ethane), 4H 2 [PF 6 ] 2 and 4H 2 [BPh 4 ] 2 . The daughter bis(acetylide) complex 4 was obtained upon deprotonation of the vinylidene precursor 4H 2 [PF 6 ] 2 by an excess of potassium tert-butoxide (80%). The heterotrimetallic complex [{Cp*(dppe)FedCdCH} 2 -{μ-(η 6 -1, 4-nph)RuCp*}][PF 6 ] 3 (5H 2 [PF 6 ] 3 ) was obtained upon reaction of the bis(vinylidene) 4H 2 [PF 6 ] 2 with [Cp*Ru(CH 3 CN) 3 ][PF 6 ] (82%). The regiopure bisacetylide isomer [Cp*(dppe)FeCtC-1,4-nph-(RuCp*)-CtCFe(dppe)Cp*][PF 6 ] (5B[PF 6 ]) was isolated as a dark brown powder (61%). The IR, 1 H, 13 C, and 31 P NMR, cyclic voltammetry, M€ ossbauer, and UV-vis data were obtained for the bisiron(II) complexes 4 and 5B[PF 6 ]. All these data and the X-ray crystal structure determined for 5B[PF 6 ] reveal a strong metal-metal interaction across the bridge reinforced by the Cp*Ru + arenophile. When reacted with 2 equiv of [(C 5 H 5 ) 2 Fe][PF 6 ], 4 and 5B[PF 6 ] provided the stable bisiron(III) complexes 4[PF 6 ] 2 and 5B[PF 6 ] 3 (60-80%), while treatment of 4 and 5B[PF 6 ] with 1 equiv of 4[PF 6 ] 2 and 5B[PF 6 ] 3 , respectively, gave the mixed valence (MV) compounds 4[PF 6 ] and 5B[PF 6] 2 (88-98%). All the iron(III) complexes can be isolated and stored at 20 °C. ESR spectroscopy and magnetization measurements established that strong superexchange interaction propagates through the 1,4-diethynylnaphthalene bridge (J = -517 cm -1 for 4[PF 6 ] 2 and J = -889 cm -1 for 5B[PF 6 ] 2 ). UV-vis-NIR spectra were obtained for the MV complexes, showing that a photodriven metal-metal electron-transfer process takes place over ca. 12 A ˚with a reorganization energy of ca. 4250 and 4410 cm -1 for 4[PF 6 ] and 5B[PF 6 ] 2 , respectively. According to the Robin and Day classification, both MV compounds constitute nice examples of strongly coupled class III organometallic MV compounds (H AD = 2140 cm -1 for 4[PF 6 ] and 2230 cm -1 for 5B[PF 6 ] 2 ).

The organoiron vinylidene derivatives [(η2-dppe)(η5-Cp*)FeCCH−(1-naphthyl)][X] (Cp* = C5Me5; dppe = 1,2-bis(diphenylphosphino)ethane; X = BPh4, 3[BPh 4 ]; X = PF6, 3[PF 6 ]) were synthesized from (η2-dppe)(η5-Cp*)FeCl and 1-naphthyl acetylene in the presence of NaBPh4 or NaPF6, respectively. The daughter organometallic acetylide complex, (η2-dppe)(η5-Cp*)Fe−C⋮C−(1-naphthyl), 4, was obtained, in 81% yield, upon deprotonation of the vinylidene precursor, 3[BPh 4 ], by t-BuOK in a MeOH/THF mixture at room temperature. One new dicationic heterobimetallic vinylidene Fe(II)−Ru(II) complex, 5[PF 6 ] 2 , was obtained, in 74% yield, upon reaction of the 1-naphthyl vinylidene precursor 3[PF 6 ], with [(η5-Cp*)Ru(CH3CN)3][PF6]. Binuclear acetylides were prepared via η6 complexation of the (η5-Cp*)Ru+ arenophile onto either the substituted or the free naphthyl ring of 1-naphthyl acetylide derivative 4, and both of these haptotropomers, 6A[PF 6 ] and 6B[PF 6 ], were isolated. A third bimetallic model compound, 2[PF 6 ], was prepared in 69% yield via (η5-Cp*Ru) coordination of the ethynyl phenyl ring of the known complex (η2-dppe)(η5-Cp*)Fe−C⋮C−Ph (1). All three complexations are regioselective, occurring only on the acetylenic aryl moiety instead of the competing dppe phenyls. The thermally stable FeIII counterparts, 2[PF 6 ] 2 , 4[PF 6 ], and 6B[PF 6 ] 2 , were obtained (70−86% isolated yield) upon oxidation, in THF at −60 °C, with ferrocenium hexafluorophosphate. All the new compounds were thoroughly authenticated using analytical and spectroscopic methods. In the heterobimetallic species, the aromaticity of the acetylide aryl linker is changed in situ via (i) the complexation of the (η5-Cp*)Ru+ arenophile and (ii) for the case of the 1-naphthyl substituent, by the η6−η6 inter-ring haptotropic migration of this group between naphthyl rings. The upshot is that these compounds exhibit significantly different degrees of electronic communication between the two organometallic termini across the length of the ethynediyl−aryl segment as a function of arenophile location:  either (i) collinear to the Fe−C⋮C wire-like segment (2[PF 6 ] and 6A[PF 6 ]) or (ii) on the free ring of the 1-naphthyl moiety (6B[PF 6 ]). To establish the degree of electron transfer within the novel compounds reported herein, their physical properties are compared using NMR, UV-vis, IR, Mössbauer, and electron spin resonance (ESR) spectroscopies, as well as cyclic voltammetry and X-ray crystallography. Accordingly, the solid-state structures of all seven novel, electron-rich organometallic acetylides are described, including both haptotropomers 6A[PF 6 ] and 6B[PF 6 ]. Finally, the first redox-driven inter-ring haptotropic rearrangement of (η5-Cp*)Ru+ between naphthyl rings was shown to occur.