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Dehydrogenation of alcohols by three iridium pincer complexes, IrH(Cl)[2,6-(tBu2PO)2C6H3] (1), {IrH(acetone)[2,6-(tBu2PO)2C6H3]}{BF4} (2), and IrH(Cl)[{2,5-(tBu2PCH2)2C5H2}Ru(C5H5)] (3), is reported, in both the presence and the absence of a sacrificial hydrogen acceptor. Dehydrogenation of secondary alcohols proceeds in a catalytic mode with turnover numbers up to 3420 (85% conversion) for acceptorless dehydrogenation of 1-phenylethanol. Primary alcohols are readily decarbonylated even at room temperature to give catalytically inactive 16e Ir–CO adducts. The mechanism of this transformation was studied in detail, especially for EtOH; new intermediates were isolated and characterized.

The digold-tetrarhenium cluster Re4(AuPPh3)2(CO)12(μ3-C≡CFc)2 (1) was obtained by the thermolysis of known complex Re2(AuPPh3)(CO)8(μ-C≡CFc) (2) and fully characterized by a single crystal X-ray diffraction study. Cluster 1 has a butterfly Re4 geometry, and both Re3 wings are capped with AuPPh3 groups. Two ferrocenylethynyl ligands symmetrically coordinated within cavity of the wings. The dihedral angle between the Re3 wings is rather narrow, 73.2°, whereas the 64e butterfly clusters usually have a more flattened structure. An examination of the carbonyl region of the 13C NMR of 1 and 2 revealed that 1 is stereochemically rigid while 2 is fluxional with respect to a σ-π interconversion of the ferrocenyl ethynyl group across the Re−Re edge of the Re2Au triangle. Complex 1 revealed a very rare electronic communication between the ferrocene units across the cluster core. According to the cyclic voltammetric (CV) data, cluster 1 undergoes two reversible redox process with ferrocene oxidations separated by 109...

Novel bis(phosphine) pincer complexes of iridium based on ferrocene and ruthenocene have been synthesized. The reaction of 1,3-bis((di-tert-butylphosphino)methyl)metallocenes [t-BuP,CH,PM] (M = Fe, 10; M = Ru, 13) with [Ir(COE)2Cl]2 in refluxing toluene leads to the corresponding chloro-hydrido pincer complexes as a mixture of H-endo- (M = Fe, 11; M = Ru, 14) and H-exo-IrH(Cl)[t-BuP,C,PM] (M = Fe, 12; M = Ru, 15) isomers. Treatment of compounds 11, 12 and 14, 15 with NaH in hot cyclooctane generates corresponding dihydrido complexes IrH2[t-BuP,C,PM] (M = Fe, 6; M = Ru, 7). Reactivity of the chelated iridium atom in hydrido-iridium pincer complexes and oxidation centered at the iron atom of ferrocene-based pincer complexes were studied. Complexes H-exo-IrH(Cl)(CO)[t-BuP,C,PFe] (20), Ir(CO)[t-BuP,C,PFe] (21), and Ir(CO)[2,6-(tBu2PO)2C6H3] (30) were characterized by X-ray crystallography. On the basis of νCO values for carbonyl iridium derivatives, electronic characteristics of the corresponding fragments {I...

The Os3(μ-H)2(CO)7(μ-C6H4){μ3-Ph2PCH2P(C6H4)Ph} complex, which was isolated from the products of thermolysis of Os3(CO)10(μ-dppm) (dppm is Ph2PCH2PPh2) in toluene, was characterized by X-ray diffraction analysis. Protonation of the resulting complex with trifluoroacetic acid afforded the cationic complex [Os3(μ-H)3(CO)7(μ-C6H4){μ3-Ph2PCH2P(C6H4)Ph}]+.

The complex [Os3(μ-H)(CO)10(μ-η1:η2-CCCMe2)]BF4 (1) reacts with PPh3 at −78 °C to give isomeric phosphonium derivatives of the formula [Os3(μ-H)(CO)10(μ-σ:η2-C⋮CCMe2PPh3)]BF4 (2 and 3); the isomeri...

Reactions of acetylide clusters M3H(C⋮CFc)(CO)9 (1a, M = Ru; 1b, M = Os; Fc = ferrocenyl) with Ru3(CO)12 in refluxing hexane yield the tetranuclear clusters RuM3H(C⋮CFc)(CO)12 (2a,b) with a butterfly metal core. The μ4-acetylide ligand of these complexes undergoes migration, indicated by variable-temperature 1H and 13C NMR studies. Compounds 2a and 2b are relatively unstable in solution as well as in the solid state and decompose with formation of corresponding trinuclear acetylide precursors and Ru3(CO)12. The molecular structures of 1a and 2a were established by the X-ray diffraction study of a mixed crystal, which contains both clusters in a 1:1 ratio.

The reaction of Ru3(CO)12 with ferrocenylacetylene FcCCH in refluxing hexane gives Ru3(μ-H)(CO)9(μ3-η2-CCFc) I, Ru2(CO)6[C4H2(Fc)2] II and Ru2(CO)6[μ-C(H)C(Fc)COC(H)C(Fc)] III. Complexes I–III were characterized by IR and NMR spectroscopy, and II also by X-ray diffraction. Complex II crystallizes in the space group Cmc21 with a = 20.072(4), b = 14.322(2), c = 9.703(2) A, and Z = 4. The structure was solved by the heavy-atom method and refined by least-squares analysis to R = 0.031 and Rw = 0.037 for 1677 unique observed reflexions. Molecule II contains a ruthenacyclopentadiene ring, π-bonded to a Ru(CO)3 group. The Ru2(CO)6 moiety adopts a “sawhorse” geometry, in contrast to the known structures of ruthenium complexes of this type, which have a “non-sawhorse” structure. Compound III possesses a nonsymmetrical diruthenacycloheptadienone moiety. The 1H NMR spectroscopy of III did not reveal any fluxionality of the “flyover” bridge leading to the exchange of σ- and π-bonds at two ruthenium atoms.

The results of studies of the reactions of ruthenium and osmium cluster carbonyls with metal alkynes, silylalkynes, propargyl alcohols and their derivatives, diynes, enynes, and ferrocenylacetylene are summarized. Intramolecular rearrangements in the cluster complexes including migrations of carbonyl, hydride, and hydrocarbon ligands as well as the metal core reorganization are considered.

Several 57Fe-labeled ferrocene derivatives and other cyclopentadienyliron complexes were studied by 57Fe and 13C NMR with respect to isotope-induced chemical shifts 1Δ12/13C(57Fe) and the magnitude and sign of coupling constants 1J(57Fe,13C) and 2J(57Fe,1H). The geometries of the complexes were optimized by DFT methods [B3LYP/6–311+G(d,p)] and chemical shifts (GIAO) and coupling constants were calculated at the same level of theory. The trends in calculated 57Fe nuclear shielding agree well with the experimental data and, in the case of coupling constants 1J(57Fe,13C) and 2J(57Fe,1H), both sign and magnitude are correctly reproduced. Copyright © 2004 John Wiley & Sons, Ltd.

International audience; Palladium P,C,P pincer complexes based on ferrocene were synthesized for the first time. The reaction of the 1,3-bis((dialkylphosphino)methyl)ferrocenes {1,3-(R2PCH2)2C5H3}Fe(C5H5) (2a, R = Pri; 2b, R = But) with PdCl2(NCPh)2 in refluxing 2-methoxyethanol leads to the corresponding pincer complexes PdCl[{2,5-(R2PCH2)2C5H2}Fe(C5H5)] (3a,b). The ferrocene-based binuclear compound 3b reacts with [Cp2Fe]PF6 to form the ferrocenium-based pincer complex {PdCl[{2,5-(But2PCH2)2C5H2}Fe(C5H5)]}PF6 (4b), and this is the first example of ferrocene-based phosphine chelate oxidation centered on the iron atom. Treatment of complexes 3a,b with NaBH4 in refluxing ethanol affords the complexes Pd(BH4)[{2,5-(R2PCH2)2C5H2}Fe(C5H5)] (5a, R = Pri; 5b, R = But), containing a BH4− group coordinated to the metal in the rarely occurring unidentate mode. The structures of 3a,b and 5b were confirmed by X-ray analyses. Cyclic voltammetric investigations of complexes 2b and 3a,b are also reported. The structural and spectroscopic features of the palladium ferrocene-based pincer complexes are discussed and compared with those of related compounds.

Protonation of triosmium clusters Os3(μ-H)(CO)9(μ3-σ,η2-C≡C-R) (R=CMe2OH, C(Me)=CH2) affords a cationic complex containing a six-electron propargyl ligand which has been detected for the first time.

1-Metallocenyl-2-methylpropyl cations are found to be chiral using nuclei diastereotopism. The positive charge distribution over the cations and the effect of a central metal atom (iron, ruthenium, osmium) are discussed.

The 13 C NMR spectra ofthe series of α,α’ -dideuterated ferrocenylcarbenium ions and their precursors, ferrocenylcarbinols as well as other ferrocene derivatives have been measured. The structures of ferrocenylcarbenium ions is discussed.

The 13 C{ 57 Fe} double resonance method has been used to investigate 57 Fe-enriched samples of ferrocene derivatives, α-ferrocenyl carbocations and carbonyl complexes with various σ- and π-hydrocarbon ligands. In the α-ferrocenyl carbocations the 57 Fe resonances span a 1200 ppm range, being a sensitive tool of direct iron participation in the stabilization. The 57 Fe resonances in the carbocations [FcCH 2 ][HSO 4 ] (I), [FcCHMe][HSO 4 ] (II), [FcCHPh][HSO 4 ] (III), [FcCHC 5 H 4 Mn(CO) 3 ][CF 3 CO 2 ] (IV), [(Fc) 2 CH][BF 4 ] (V), [FcCHC 5 H 4 RuC 5 Hs][BF 4 ] (VI) and [FcCMe 2 ][HSO 4 ] (VII), −523.6, −219.3, 221.0, 368.7, 699.0, 405.0 and 288.5 ppm, respectively, relative to ferrocene, are interpreted in terms of rehybridization of the iron non-bonding d orbitals (shielding effect and the electron withdrawing effect of the substituent in the cyclic ligand (deshielding effect). The role of rehybridization of non-bonding iron orbitals in the low-frequency shift of the 57 Fe resonances, in addition to that in the previously investigated complex [(C 5 H 5 ) 2 FeH][BF 3 OH] (−1109.3 ppm), has been demonstrated for bridge-substituted [3]ferrocenophanes, whose ring tilting induces a low-frequency shift of up to 340 ppm relative to their unbridged analogues. The 13 C NMR spectra of carbocations V and VI reveal a temperature dependence due to the rotation around the C(1)C α exocyclic bonds. In carbocation VI the ruthenium atom effectively competes with the iron atom to bond with C α whereas in carbocation V two equivalent metal atoms possess the same ability for such bonding; as a result, complex V has a more pronounced “carbenium ion” nature than IV and VI, as indicated by the relative positions of the 13 C α resonances in carbocations IV, V and VI: δ 122.4, 147.2 and 116.9 ppm, respectively. The values of 57 Fe, 13 C coupling constants for α-ferrocenyl carbocations exclude Fe-C α σ-bonding and support a structure in which the iron atom is π-bonded with six carbon atoms of a fulvenoid ligand. According to the data on 57 Fe resonances and 57 Fe, 13 C coupling constants in α-ferrocenyl carbocations the strength of FeC α bonding is markedly influenced by the electronic effect of the substituent at C α , being even lower in carbocation I than that of Fe-cyclopentadienyl carbon atoms.

The chemical shifts of C(2,5) and C(3,4) carbons in the 13C NMR spectra of monosubstituted ferrocenes have been assigned using deuterium labelling. An analogy is observed between the shielding of C(2,5) and C(3,4) carbons of ferrocene derivatives and ortho- and para-carbons of benzene derivatives withthe same substituents. Electron-density distribution in the cyclopentadienyl ring is discussed on the basis of 13C NMR data.