How do nitriles compare with isoelectronic alkynyl groups in the electronic communication between iron centers bridged by phenylenebis- and -tris(nitrile) ligands? An electronic and crystal-structure study

Crystal structure of ruthenocenecarbo-nitrile

The mol-ecular structure of ruthenocenecarbo-nitrile, [Ru(η(5)-C5H4C N)(η(5)-C5H5)], exhibits point group symmetry m, with the mirror plane bis-ecting the mol-ecule through the C N substituent. The Ru(II) atom is slightly shifted from the η(5)-C5H4 centroid towards the C N substituent. In the crystal, mol-ecules are arranged in columns parallel to [100]. One-dimensional inter-molecular π-π inter-actions [3.363 (3) Å] between the C N carbon atom and one carbon of the cyclo-penta-dienyl ring of the overlaying mol-ecule are present.

Crystal structure of paddle-wheel sandwich-type [Cu2{(CH3)2CO}{μ-Fe(η(5)-C5H4C N)2}3](BF4)2·(CH3)2CO

The mol-ecular structure of (acetone-κO)tris-(μ-ferrocene-1,1'-dicarbo-nitrile-κ(2) N:N')dicopper(I) bis-(tetra-fluorido-borate) acetone monosolvate, [Cu2Fe3(C6H4N)6(C3H6O)](BF4)2·C3H6O, consists of two Cu(I) ions bridged by a ferrocene-1,1'-dicarbo-nitrile moiety in a paddle-wheel-architectured sandwich complex with two BF4 (-) units as counter-ions. One of the latter is equally disordered over two sets of sites. The two Cu(I) ions are complexed in a trigonal-planar manner by three nitrile N-donor atoms. Further inter-actions by the O atom of an acetone mol-ecule to one of the Cu(I) atoms and a weak η(2),π-inter-action of two atoms of a cyclo-penta-dienyl ring to the other Cu(I) atom complete a distorted trigonal-pyramidal environment for each of the metal ions. A further acetone mol-ecule is also present as a solvent mol-ecule. The crystal packing is consolidated by several π-π inter-actions.

Hybrid molecular systems containing tetrathiafulvalene and iron-alkynyl electrophores: five-component functional molecules obtained from C-H bond activation

Treatment of [Cp*(dppe)Fe-C≡C-TTFMe3] (1) with Ag[PF6] (3 equiv) in DMF provides the binuclear complex [Cp*(dppe)Fe=C=C=TTFMe2 =CH-CH=TTFMe2 =C=C=Fe(dppe)Cp*][PF6]2 (2[PF6 ]2) isolated as a deep-blue powder in 69 % yield. EPR monitoring of the reaction and comparison of the experimental and calculated EPR spectra allowed the identification of the radical salt [Cp*(dppe)Fe=C=C=TTFMe2 =CH][PF6]2 ([1-CH][PF6]) an intermediate of the reaction, which results from the activation of the methyl group attached in vicinal position with respect to the alkynyl-iron on the TTF ligand by the triple oxidation of 1 leading to its deprotonation by the solvent. The dimerization of [1-CH][PF6] through carbon-carbon bond formation provides 2[PF6]2. The cyclic voltammetry (CV) experiments show that 2[PF6]2 is subject to two sequential well-reversible one-electron reductions yielding the complexes 2[PF6] and 2. The CV also shows that further oxidation of 2[PF6]2 generates 2[PF6]n (n=3-6) at the electrode. Treatment of 2[PF6]2 with KOtBu provides 2[PF6] and 2 as stable powders. The salts 2[PF6] and 2[PF6]2 were characterized by XRD. The electronic structures of 2(n+) (n=0-2) were computed. The new complexes were also characterized by NMR, IR, Mössbauer, EPR, UV/Vis and NIR spectroscopies. The data show that the three complexes 2[PF6]n are iron(II) derivatives in the ground state. In the solid state, the dication 2(2+) is diamagnetic and has a bis(allenylidene-iron) structure with one positive charge on each iron building block. In solution, as a result of the thermal motion of the metal-carbon backbone, the triplet excited state becomes thermally accessible and equilibrium takes place between singlet and triplet states. In 2[PF6], the charge and the spin are both symmetrically distributed on the carbon bridge and only moderately on the iron and TTFMe2 electroactive centers.