The molecular structures of two isomers of Fe3(CO)8(C6H5C2C6H5)2

Dodge, Richard P.; Schomaker, Verner

doi:10.1016/s0022-328x(00)84647-1

Cited by 113 publications

(16 citation statements)

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“…Such interconversion involves three catalytic reactions: activation of the alkane CÀH bond, olefin metathesis, and hydrogenation of the formed olefins. However, because of the cross-metathesis of the alkenes during the recombination process, the product will have a molecular weight distribution to some extent.Coupling reactions between two hydrocarbyl ligands placed on both faces of a trimetallic plane have often been seen in organometallic chemistry, [2] as has CÀC bond scission on a cluster. [3] These reactions have attracted considerable attention and are considered to be characteristic of cluster compounds.…”

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confidence: 99%

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Metathesis Reaction of Hydrocarbyl Ligands across the Triruthenium Plane

Tahara¹,

Kajigaya²,

Moriya³

et al. 2010

Angew Chem Int Ed

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Carbon-chain recombination, similar to that observed during the cracking of alkanes and in the Shell higher olefin process, is one of the most important reactions in the chemical industry. There has been a continuous demand for a process that can yield hydrocarbons of desired chain length. Recently, a method for converting lower alkanes into higher alkanes, which is referred to as alkane metathesis, has been reported. [1] Alkane metathesis has considerable scientific and industrial importance because it can convert gaseous hydrocarbons into liquid fuels. Such interconversion involves three catalytic reactions: activation of the alkane CÀH bond, olefin metathesis, and hydrogenation of the formed olefins. However, because of the cross-metathesis of the alkenes during the recombination process, the product will have a molecular weight distribution to some extent.Coupling reactions between two hydrocarbyl ligands placed on both faces of a trimetallic plane have often been seen in organometallic chemistry, [2] as has CÀC bond scission on a cluster.[3] These reactions have attracted considerable attention and are considered to be characteristic of cluster compounds. We have studied C À C bond formation on a triruthenium cluster by directing our attention to the roles of an MÀM bond.[4] Recently, we reported the synthesis of 2 using the coupling reaction of m 3 -benzyne and m 3 -vinylidene ligands separated by the Ru 3 plane of 1 (Scheme 1).[4c] In this reaction, the formation of the ruthenacyclopentadiene skeleton was accompanied by the rupture of a Ru À Ru bond. We also reported the scission of a CÀC bond in a ruthenacyclopentadiene skeleton in which a Ru 3 triangle was reconstructed.[4a] Such flexibility in a cluster skeleton would enable a novel recombination of hydrocarbons. Herein, we report an unprecedented selective interconversion of two C 5 fragments into C 8 and C 2 fragments on a triruthenium cluster.The thermolysis of 4, which was obtained by the sequential treatment of 3 with 1-pentene and 1-pentyne, [5] resulted in the quantitative formation of an equilibrated mixture of 5 a and 5 b (Scheme 2). At ambient temperature, the motion of the hydrido ligand was so rapid that the signals of 5 a and 5 b coalesced. For simplification, we denote this equilibrated mixture as 5.[6] The structures of 4 and 5 were determined by X-ray diffraction studies (Figure 1 and Figure 2, respectively).[7] These results clearly indicate that the m 3 -pentylidyne and m 3 -pentyne ligands in 4 were respectively transformed into the m 3 -ethylidyne and m 3 -octyne ligands in 5.This rearrangement required the migration of the C 3 fragment across the Ru 3 plane. In order to elucidate the mechanism, we monitored the reaction by means of NMR spectroscopy. Upon heating at 80 8C, formation of the m 3 -butylidyne-m 3 -hexyne complex 6 was observed (Path a in Scheme 3). For the formation of 6, a carbyne group must Scheme 1. CÀC bond formation in a trimetallic cluster accompanied by MÀM bond breaking. Cp* = pentamethylcyclopentadienyl. Sche...

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“…Coupling reactions between two hydrocarbyl ligands placed on both faces of a trimetallic plane have often been seen in organometallic chemistry, [2] as has CÀC bond scission on a cluster. [3] These reactions have attracted considerable attention and are considered to be characteristic of cluster compounds.…”

mentioning

confidence: 99%

Metathesis Reaction of Hydrocarbyl Ligands across the Triruthenium Plane

Tahara¹,

Kajigaya²,

Moriya³

et al. 2010

Angew Chem Int Ed

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“…Another example, one of many that might be given, is the violet iron carbonyl diphenylacetylene complex Fe3(C-O)g(C6HsC2C6Hs)2 (15). Each iron atom achieves the valence 9 by receiving an electron from one carbonyl group, with which it forms a single bond (Fe-OO:+).…”

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Maximum-valence radii of transition metals

Pauling¹

1975

Proc. Natl. Acad. Sci. U.S.A.

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In many of their compounds the transition metals have covalence 9, forming nine bonds with use of nine hybrid spd bond orbitals. A set of maximum-valence single-bond radii is formulated for use in these compounds. These have now found that the structures of many compounds of transition metals can be discussed in a satisfying way on the basis of covalence 9 (or 8 in some cases) and have formulated a corresponding set of maximum-valence single-bond radii, given in Table 1. These radii may be used in interpreting the experimental values of bond lengths.It was recognized long ago that the formulas of the carbonyls Cr(CO)6, Fe(CO)5, and Ni(CO)4 correspond to completion of the argon structure (9 outer electron pairs, shared or unshared) by the metal atom. In Ni(CO)4, for example, the nickel atom might form sp3 single bonds (a shared electron pair) with each of the four carbon atoms and have five unshared pairs in its 3d orbitals. This structure is not acceptable, however, because it gives the nickel atom the formal charge -4, which cannot be overcome by the partial ionic character of the bonds. The structure in which the nickel atom has one unshared pair and forms double bonds with each of the carbon atoms, giving nickel the covalence 8 and zero formal charge, was suggested in 1921 by Langmuir (5) and verified in 1935 by the determination of the nickel-carbon bond length as 182 + 3 pm by Brockway and Cross (6). In Fe(CO)5 we assign double bonds from the iron atom to four carbon atoms and a single bond (with transfer of an electron to the iron atom) to the fifth, and in Cr(CO)6 three double bonds and three single bonds to carbon atoms, giving valence 9 to iron and chromium. The amount of ionic character of the metal-carbon bonds is large enough to make these structures compatible with the electroneutrality principle.The structure for Co2(CO)8 with cobalt-carbon double bonds and a cobalt-cobalt single bond corresponds to valence 9 and the argon structure for cobalt. The observed cobaltcobalt bond length 252.4 i 0.2 pm (7) leads directly to 126.2 pm for the single-bond covalent radius for cobalt with valence 9. Similar values are reported for R1 (v = 9) in other molecules with cobalt-cobalt bonds: 123.5 pm in dicobalthexacarbonyl diphenylacetylene (8), 123.5 pm in ethylidene tri(cobalttricarbonyl) (9), 123.5 pm in bis(tricobaltenneacarbonyl)acetone (10), 122.4 to 124.3 pm in Cos(CO)1sC3H (11), and 124.4 pm in hexacarbonyl- 3,4,5,5,6,6-hexafluorocyclohexa-1-yne-3-enedicobalt (12). Values of R1 (v = 9) for iron are given by observed iron-iron bond lengths as, for example, 123 pm in Fe2(CO)9 (13), 132 pm in Fe5(CO)15C (14) Table 1, are from 8 to 12 pm larger than the single-bond metallic radii, which for these metals correspond to the valence 6.The following equation (17) is to be used in calculating the bond length for a bond with bond number n (less than 1) between atoms A and B: Bond length = R1(A) + R1(B) -60 pm log n -CIXA -XBI [1] In this equation XA is the electronegativity of atom A and c is the Schomaker-...

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“…No reaction occurred with 1c and [Fe 3 (CO) 12 ], whereas the trinuclear iron complexes Fe-I and Fe-II were selectively generated from reactions of [Fe 3 (CO) 12 ] and 2a at 60 and 120 8 8C, respectively. [10] Although no reaction took place with 1c and either Fe-I or Fe-II,they did catalyze the annulation of 1c with 2a to afford 3ca in comparable yields (Scheme 3c). Furthermore,d ifferent alkynes, 2g and 2b,were reacted with 1c under the catalysis of either Fe-I or Fe-II and only 3cg and 3cb were formed.…”

Section: Transition-metal-catalyzed Direct Transformations Of Inertmentioning

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Iron‐Carbonyl‐Catalyzed Redox‐Neutral [4+2] Annulation of N−H Imines and Internal Alkynes by C−H Bond Activation

Jia

Zhao

et al. 2016

Angew Chem Int Ed

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Stoichiometric C-H bond activation of arenes mediated by iron carbonyls was reported by Pauson as early as in 1965, yet the catalytic C-H transformations have not been developed. Herein, an iron-catalyzed annulation of N-H imines and internal alkynes to furnish cis-3,4-dihydroisoquinolines is described, and represents the first iron-carbonyl-catalyzed C-H activation reaction of arenes. Remarkablely, this is also the first redox-neutral [4+2] annulation of imines and alkynes proceeding by C-H activation. The reaction also features only cis stereoselectivity and excellent atom economy as neither base, nor external ligand, nor additive is required. Experimental and theoretical studies reveal an oxidative addition mechanism for C-H bond activation to afford a dinuclear ferracycle and a synergetic diiron-promoted H-transfer to the alkyne as the turnover-determining step.

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The molecular structures of two isomers of Fe3(CO)8(C6H5C2C6H5)2

Cited by 113 publications

References 8 publications

Metathesis Reaction of Hydrocarbyl Ligands across the Triruthenium Plane

Metathesis Reaction of Hydrocarbyl Ligands across the Triruthenium Plane

Maximum-valence radii of transition metals

Iron‐Carbonyl‐Catalyzed Redox‐Neutral [4+2] Annulation of N−H Imines and Internal Alkynes by C−H Bond Activation

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