Facile access to redox-active C2-bridged complexes with half-sandwich manganese end groups.

The dinuclear mixed-valent complex [(MeC5H4)(dmpe)MnC(2)Mn(dmpe)(C5H4Me)](+)[(eta2-MeC5H4)3Mn](-)[1](+)[2]- (dmpe=1,2-bis(dimethylphosphanyl)ethane) was prepared by the reaction of [Mn(MeC5H4)2] with dmpe and Me(3)SnC[triple chemical bond]CSnMe3. The reactions of [1](+)[2]- with K[PF6] and Na[BPh4] yielded the corresponding anion metathesis products [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6] ([1][PF6]) and [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][BPh4] ([1][BPh4]). These mixed-valent species can be reduced to the neutral form by reaction with Na/Hg. The obtained complex [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)] (1) displays a triplet/singlet spin equilibrium in solution and in the solid state, which was additionally studied by DFT calculations. The diamagnetic dicationic species [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6]2 ([1][PF6]2) was obtained by oxidizing the mixed-valent complex [1][PF6] with one equivalent of [Fe(C5H5)2][PF6]. Both redox processes are fully reversible. The dinuclear compounds were characterized by NMR, IR, UV-visible, and Raman spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-ray diffraction studies were performed on [1][2], [1][PF6], [1][BPh4], and [1][PF6]2

Synthesis and some reactions of the heterometallic C(7) complex {Cp*(dppe)Ru}Ctriple barCCtriple barCCtriple barCC{Co(3)(mu-dppm)(CO)(7)}

Copyright © 2008 American Chemical SocietyThe heterometallic carbon-chain complex {Cp*(dppe)Ru} C≡CC≡CC≡CC{Co3(μ-dppm)(CO)7} (1) has been obtained by three routes that involve assembly of the C7 chain by combination of appropriate C1 + C6, C2 + C5, or C3 + C4 precursors. The Cp analogue 2 and Co3(CO)9 cluster analogue 3 were obtained via the C2 + C5 and C1 + C6 routes, respectively. Reaction of 1 with PPh3 gave 4 via substitution of a Co3 cluster-bonded CO group. Addition of MeOTf to the second carbon from the Ru center in 1 afforded the vinylidene [{Cp*(dppe)Ru}=C= CMeC≡CC≡CC{Co3(μ-dppm)(CO)7}]OTf (5), while addition of tcne or tcnq across the central C≡C bond gave {Cp*(dppe)Ru}C≡CC[=C(CN)2]C[=C(CN)2]- C≡CC{Co3(μ-dppm)(CO)7} (6) and {Cp*(dppe)Ru}C≡CC[=C6H4C(CN) 2]C[=C(CN)2]C≡CC{Co3(μ-dppm)(CO) 7} (7), respectively. The reaction between 1 and Fe 2(CO)9 was more complex, the major product being {Cp*(dppe)Ru}C≡CC{Fe3(CO)9}CC≡CC{Co 3(μ-dppm)(CO)7} (8), accompanied by an Fe 2(CO)6 derivative (9) of as yet undetermined structure. {Cp*(dppe)Ru} C≡CC≡CC≡CC {Co2Ni(μ-dppm) (CO)4Cp} (10) was obtained from the reaction with NiCp2. An unstable adduct containing two Co2(CO)6 groups attached to the C7 chain was formed in reactions between 1 and Co 2(CO)8. XRD structural studies of 1, 2, 6-8, and 10 are reported. Electrochemical measurements suggest that there is some interaction between the two end groups, although this cannot presently be quantified. It is concluded that the C7 chain is long enough for the properties of the individual end caps to be preserved, while steric inhibition from the phenyl groups of the dppe and dppm ligands directs addition to the central C≡C triple bond of the C7 chain. © 2008 American Chemical Society.Michael I. Bruce, Marcus L. Cole, Christian R. Parker, Brian W. Skelton and Allan H. Whit

Extending metal-capped polyynediyl molecular wires by insertion of inorganic metal units

Several symmetric and asymmetric bis(metalla-diynediyl)ruthenium(II) complexes of the general formula trans-{L xRu} C≡CC≡C{Ru(dppe) 2}C≡CC≡C{RuL′ y} (L x, L′ y = (PPh 3) 2Cp, (dppe)Cp, (dppe)Cp*), containing Ru(dppe) 2 as the central linking group, have been successfully synthesized and characterized spectroscopically. DFT calculations show that their HOMO's are delocalized over the Ru-C 4-Ru-C 4-Ru chain, suggesting that there is electronic interaction between the terminal RuL x groups through the C 4 chains and the Ru(dppe) 2 center. Limited electrochemical measurements reveal that the complexes undergo a series of five stepwise reversible or quasi-reversible oxidation processes. © 2012 American Chemical Society.Michael I. Bruce, Boris Le Guennic, Nancy Scoleri, Natasha N. Zaitseva, and Jean-François Hale

Redox-active complexes containing group 8 metal centers linked by C2 bridges

Copyright © 2007 American Chemical SocietyA series of complexes containing dicarbon ligands bridging redox-active group 8 metal-ligand fragments M(dppe)Cp′ (M = Fe, Ru, Os; Cp′ = Cp, Cp*) have been prepared. These complexes give up to four one-electron anodic processes at a platinum electrode, with separations of successive oxidation potentials of ca. 850 mV, giving rise to large comproportionation constants, K c (ca. 10 12). Examples of the 36-electron neutral, 35-electron monocationic, and 34-electron dicationic species, together with some related monoprotonated complexes, have been isolated. Structural studies of the 36-, 35-, and 34-electron species derived from the dicarbon complex featuring two Ru(dppe)Cp end-caps (7) show that shortening of the M - C and lengthening of the C - C bonds occur upon oxidation. A complementary spectroelectrochemical investigation has revealed an intense band near 14 300 cm -1 associated with [7]PF 6, which is tentatively attributed to a Ru(d) - [Ru(d)/C 2(π)]* transition, rather than a genuine IVCT band. These observations have been rationalized using DFT calculations and collectively indicate that the frontier orbitais are delocalized over both group 8 metal centers and the carbon chain. © 2007 American Chemical Society.Michael I. Bruce, Karine Costuas, Ben G. Ellis, Jean-François Halet, Paul J. Low, Boujemaa Moubaraki, Keith S. Murray, Nadia Ouddaï, Gary J. Perkins, Brian W. Skelton, and Allan H. Whit