Masanobu Watanabe

57Fe Mössbauer spectra and X-ray structural analyses of iodide salts for 1′,1‴-bis(α- and β-naphthylmethyl)-1,1″-biferrocenes

Abstract The relation between the mixed-valence state and crystal structure of iodide salts for 1′,1‴-bis(α- and β-naphthylmethyl)-1,1″-biferrocenes has been studied by means of 57Fe Mossbauer spectroscopy and X-ray structural analysis. Time change of 57Fe Mossbauer spectroscopy was first observed for only the α-naphthylmethyl derivative; the trapped-valence state (metastable phase) of the Fe atom in the salt gradually changes into the detrapped-valence state (stable phase) on standing at room temperature for one month. There are two independent monocations in the β-naphthylmethyl derivative. Both salts (α-naphthylmethyl derivative in stable phase and β-naphthylmethyl derivative) gave the detrapped-valence state of 57Fe Mossbauer spectra, implying the equivalence of the oxidation state of the two Fe atoms. X-ray diffraction studies of both salts support the above results, i.e. both monocations sit on the center of symmetry and the Feue5f8C(Cp) distances (2.064(2) A for the α-naphthylmethyl derivative and 2.061(9) and 2.056(7) A for the β-naphthylmethyl derivative) are close to the mean values of ferrocene and ferrocenium ion.

Molecular structure of chlororuthenocenium +BF4− and chlorobiruthenocenium +BF4− salts

Abstract The structures of chlororuthenocenium +BF4− ([RcHCl]+BF4−, 1) and chlorobiruthenocenium +BF4− ([RcRcCl]+BF4−, 2) were determined by single-crystal X-ray diffraction studies. The crystal form of 1 is monoclinic, space group P2 1 /c, a = 7.801(6), b = 14.370(6), c = 10.422(3) A , β=91.91(4)°, Z=4, with the final R=0.032 and Rw=0.038 . The cyclopentadienyl (Cp) rings in the cation are slanted greatly (dihedral angle, 34.54 °) according to the RuIVue5f8Cl bond (2.417(2) A) formation. The crystal form of 2 is monoclinic, space group P2 1/n , a=24.539(4), b=10.627(5), c=7.333(4) A , β=93.57(3)°, Z=4, with the final R=0.044 and Rw = 0.033 . The cation formulated as [RuIICp(C5H4C5H4)CpRuIVCl]+ exists in a trans-conformation, as in the case of neutra biruthenocene (RcRc). The distance between the RuII and RuIV (5.366(1) A) indicates the absence of metal-metal interaction. The Cp and C5H4 planes in the [Cp(C5H4)RuCl]+ moiety are more slanted (dihedral angle, 39.98°) than that of 1. Moreover, the fulvalence ligand (C5H4C5H4) is not planar owing to the repulsion between the two Cl and the C1 atoms which connect the two C5H4 moieties.

Molecular structure of α,α-carbonium [1.1]ferrocenylruthenocenophane + BF4− salt

The oxidation of [1.1]ferrocenylruthenocenophane ( 1 ) with bromo- or chlororuthenocenium + BF 4 − ([RcHX] + BF 4 − ;X = Br, Cl) was carried out giving a diamagnetic salt 2 . The crystal form of 2 is monoclinic, space group P2 i /n, a = 10.556(3), b = 13.634(3), c = 13.795(2)A˚, β = 107.27(2)°, V = 1896.0(8)A˚ 3 , Z = 4, and the final R = 0.045andR w = 0.040, based on the results of the single-crystal X-ray diffraction study. The distance between the Ru and Fe is ca. 4.495(2)A˚, which is much shorter than 1 (4.792(2)A˚). The structure of the cation is illustrated as a resonance hybrid canonical structure of α,α-carbonium-type expressed as [Fe 11 (C 5 H 4 CH 2 C 5 H 4 )(C 5 H 4 CHC 5 H 4 )Ru] + andη 6 -fulvalne-type as [Fe 11 (C 5 H 4 CH 2 C 5 H 4 )(C 5 H 4 CH C 5 H 4 )Ru] + . The two C 5 H 4 rings on the Ru side are tilted greatly (the dihedral angle of the rings is 10.92°) owing to the Ru C α + bond formation (2.407(6)A˚), which gives the stability of the carbonium center -CH + -. 57 Fe Mo¨ssbauer, 1 H, 13 C and 13 C CP/MAS NMR spectroscopic studies support the above formula.

A molecular structure of mixed valence biruthenocenium (RuIIRuIV) salts [RuIICp(C5H4C5H4)CpRuIVL]2+(BF4−)2 (L NCCH3, N(CH)4N)

Abstract The conformation of the oxidation product (A) of biruthenocene (RcRc) with p-benzoquinone containing boron trifluoride diethylether complex is [RcRcC6H4O2]2+(BF4−)2 in which p-benzoquinoen is ligated to the RuIV center. The recrystallization of A from the mixture of nitromethhane containing small amount of acetonitrile or pyrazine gives mixed-valence cations formulated as [RuIICp(C5H4C5H4)CpRuIVL]2+ (L = acetonitrile 1 and pyrazine 2), in which L is coordinated to the RuIV center. The crystal of 1 formulated as [RuIICp(C5H4C5H4)CpRuIVNCCH3]2+ (BF4−)2. CH3NO2 (1), is found to be orthorhombic, space group Pbca, a = 14.255(7), b = 37.105(10), c = 10.051(4) A , V = 5316(4), Z = 8 and the final R = 0.054 and Rw = 0.059. The similar pyrazine salt 2 formulated as [RuIICp(C5H4C5H4)CpRuIVN(CH)4N]2+ (BF4−)2(CH3NO2)2is found to be triclinic, space group P 1 , a = 9.006(2), b = 19.233(4), c = 28.907(10) A , α = 89.45(1)°, β = 86.10(3)°, γ = 87.85(2)°, V = 4991(2), Z = 2, and the final R = 0.077 and RW = 0.090. The unit cell has three independent molecules (2A, 2B, 2C). The Ru(IV)-N distances (2.15(1) A for 2A, 2.11(1) for 2B and 2.15(1) for 2C) are longer by ca. 0.1 A than that of 1 because of bulky molecule of pyrazine. Both cations (1,2) have wedge-sharp structure due to the Ruue5f8N bond, the dihedral angles between the Cp and C5H4 rings of the [LRuIVCp(C5H4)]2+ moiety are 38.70° for 1, 38.77° (2A), 40.84° (2B) and 41.67° (2C) for 2. The nucleophilicity to the RuIV increases in the order Cl− > pyrazine > acetoritrile > p-benzoquinone and unlike the case of mixed-valence halobiruthenocenium cations ([RcRcX]+: X ue5fb Cl, Br, I), no temperature dependent 1H - and 13C-NMR spectra were observed for 1 and 2 in solution, implying the absence of two-electron exchange reaction between the RuII and RuIV.

Molecular structure of iodo [1.1]ferrocenylruthenocenophanium+ BF4− salt

Abstract The structure of iodo[1.1]ferrocenylruthenocenophanium+ BF4− (1), prepared by oxidation of [1.1]ferrocenylruthenocenophane ([1.1])FcRc) with iodoruthenocenium+ BF4− ([RcHI]+ BF4−) was analyzed by single-crystal X-ray diffraction. The crystal form of 1 is triclinic, space group P 1 , a = 9.794( 2 ), b = 14.393( 4 ), c = 7.777(2) A , α = 101.62(4), β = 93.17(4), γ = 72.09(2)°, Z = 2 , and the final R and Rw were both 0.052. The cation exists in a syn-conformation, as with other [1.1]metallocenophanes, and is given the formula [Fe(II)(C5H4CH2C5H4)2Ru(IV)I]+ with Ru(IV)-I bond (2.751(1) A) formation in the solid. The distance between the Ru(IV) and Fe(II) atoms is 4.719(1) A, which is slightly shorter than the value for [1.1]FcRc, and the bond angle of Iue5f8Ru(IV)ue5f8Fe(II) is 91.50(1)°. The cation has two kinds of twisted C5H4CH2C5H4 systems. The cyclopentadienyl rings in the [Cp(C5H4)RuI]+ moiety are highly slanted (the dihedral angle between the Cp ring and fulvenide ligand is 33.87°) owing to the Ru(IV)-I bond. Large downfield shifts of the 13C CP/MAS NMR signals for the ruthenocene moiety are explained by the same fact.

Counter anion effect on molecular structures of some iodobiruthenocenium and iodoferrocenylruthenocenium salts

Abstract Oxidations of biruthenocene (RcRc) and ferrocenylruthenocene (FcRc) with an equivalent amount of iodine or iodoruthenocenium +Y− ([RcHI]+Y−), Y ue5fb BF4− and PF6−) gave monocationic halometallocenium salts formulated as [M11Cp(C5H4C5H4)CpRuIVI]+Y− (M ue5fb Ru, Y ue5fb I3 1, BF4 2; M ue5fb Fe, Y ue5fb I3 3, BF4 4, PF6 5). The crystal structure of 1, 3 and 4 were analyzed by single-crystal X-ray diffraction. The crystal of 1 is monoclinic, space group P2 1 c , a = 10.737(3), b = 23.957(3), c = 9.936(3) A , β = 110.96(2)°, Z = 4, final R = 0.084 . The crystal of 3 is monoclinic, space group P2 1 c , a = 10.575(3), b = 9.902(4) a , β = 110.85(3)°, Z = 4 , final R = 0.049. The crystal of 4 is orthorhombic, space group P2 1 2 1 2 1 , a = 9.871(10), b = 25.581(10), c = 7.810(3) A , Z = 4, final R = 0.094. The most interesting structural difference between the I3− (1.3) and other salts (2, 4, 5) is found in the direction of the RuIV−1 bond with respect to the remaining half of the M11Cp(C5H4) (M ue5fb Ru, Fe) moiety. Because one end of the I3−1 anion sits above the C5H4 plane of the M11Cp(C5H4) moiety, the RuIV-I− bons is fixed in the trans position to the M11Cp(C5H4) moiety, avoiding steric hindrance between them when the I3− salts (1 and 3) are crystallized. In the case of the BF4− and PF6− salts, the RuIV-I− bond sits in the cis position to the M11Cp(C[in5H4) moiety, as shown in Scheme 1, and this conformation gives larger tilting angles between the two ν5-Cp and ν5-C5H4 on the RuIV side (e.g. tilting angles 42.4° and 39.21° for 2 and 4 respectively) than those of both I3− salts (31.08° for 1, 32.73° for 3) due to the van der Waals contact between I and the C5H4C5H4 plane. Such large conformational differences between the salts 1, 3 and 2, 4, 5 were observed from the results of 13C CP/MAS NMR and 57Fe-Mossbauer spectroscopic studies; i.e. large temperature dependent 57Fe-Mossbauer spectra were found for 4 and 5, unlike the case of 3, probably because of the delocalization of the higher positive [IRuIVCp(C5Hin4)]su1 charge to the Fe11Cp(C5H4) moiety for 4 and 5.

Mixed valence state associated with halogen migration in diruthenocenylmethane and its related compounds

Abstract Diruthenocenylketone (RcCORc, 1 ) as a precursor of diruthenocenylmethane (RcCH 2 Rc, 2 ), was first prepared in 30% yield in a one-step reaction of ruthenocene (RcH) with butyllithium (BuLi) and N , N -dimethylcarbamyl chloride. Reaction of 2 with I 2 and iodoruthenocenium(IV) + PF 6 − ([RcHI] + PF 6 − ) gives mixed valence salts formulated as [Ru II Cp(C 5 H 4 CH 2 C 5 H 4 )CpRu IV I] + Y − (Y=I 3 ( 3 ), PF 6 ( 4 )) in which the intramolecular electron exchange reaction associated with iodine migration between the Ru II and Ru IV atoms is observed. The activation energy of the reaction ( E a ) is estimated to be 31.0±0.6 kJ mol −1 for 3 in acetone, which is smaller than the corresponding value of a mixed valence [RcRcI] + I 3 − salt (36.5±0.6 kJ mol −1 ). Reaction of 2 with the [RcHCI] + PF 6 − or [RcHBr] + PF 6 − salts gives an α,α-diruthenocenylmethylium + PF 6 − salt formulated as [Ru II Cp(C 5 H 4 CH + H 4 C 5 )CpRu II ]PF 6 − ( 5 ).

Molecular structure of some [1.1 ]ferrocenylruthenocenophaniumn+ (n = 1,2 polyiodides salts

Oxidation of [1.1]ferrocenylruthenocenophane with a large excess and 1.5 equivalents of iodine gives dicationic iodo[1.1]ferrocenylruthenocenophanium2+I3− · 0.5I22 (1) and monocationic [1.1]ferrocenylruthenocenophanium+I3− (2) salts respectively. The structures of 1 and 2 were analyzed by single-crystal X-ray diffraction studies. The crystal form of 1 is monoclinic space group C2/c, a = 21.35](5), b = 20.594(5), c = 17.397(4) A, β = 124.17(1)°, Z = 8, and the final R = 0.068 and Rw = 0.070. The cation formulated as [FeIII(C5H4CH2C5H4)2RuIVI]2+ exists in a syn-conformation as in the cases of the neutral compound. The distance between the RuIV and FeII is 4.656(4) A, which is much shorter than the value of the neutral compound (4.792(2) A), and the bond angle of Iue5f8RuIV,FeIII is 81.26°. The dihedral angle between the two η5-C5H4 (fulvenide) rings on the RuIV moiety is 37.56° due to the RuIVue5f8I bond (2.758(3) A). These two rings of FeIII and RuIV moieties are essentially eclipsed. The unit cell has three kinds of I3− (I3a−, I3b− and I3c−) and one I2, and the formula of 1 is given as [FeIII(C5H4CH2CSH4)2RuIVI]2+I3− · 0.5(I3−)2 · 0.5I2. The crystal of 2 formulated as [FeIII(C5H4CH2C5H4)2RuII]+I3− is triclinic space group P1, a = 13.487(6), b = 15.404(7), c = 11.458(4) A, α = 95.59(3)°, β = 101.00(3)° γ = 79.38(3)°, Z = 2, and the final R = 0.067 and Rw = 0.068. The unit cell has two independent molecules (unit A and B); i.e. two kinds of distance between the RuII and FeIII, are observed; one (A) is 4.615(3) and the other (B) is 4.647(3) α. The two η5-C5H4 rings of both FeIII and RuII are essentially staggered and the dihedral angles between the rings of FcH and RcH moieties are less than 5.8°. Typical ferrocenium-type broad singlet 57Fe-Mossbauer lines are observed for both salts (1, 2) at all temperatures.

Phase Transition in 1′, 1′″-Dihexylbiferrocenium Triiodide Accompanied by a Change In Mixed-Valence State

Abstract Two different crystals of 1′, 1′″-dihexylbiferrocenium triiodide were obtained from the different solution (hexane or dichloromethane). The salt prepared from hexane has a longer interlayer distance and gives trapped-valence state of Fe atoms, while the salt recrystallized from dichloromethane has a shorter interlayer distance and gives typical fusion-type valence detrapping of the mixed- valence state on the 57Fe Mossbauer spectroscopy. By annealed at 323 K the latter changes into the former salt. The X-ray diffraction study of the latter supports the results of the 57Fe Mossbauer spectroscopy.