1,2-eq,eq-[Re₂(CO)₈(THF)₂]:  A Reactive Re₂(CO)₈Fragment That Easily Activates H−H and C−H Bonds

Abstract

The reaction of [Re2(μ-H)2(CO)8] (1) with diazomethane at 193 K in THF-d 8 gives the unstable [Re2(μ-H)(μ-CH3)(CO)8] derivative (2) containing a methyl group arising from the insertion of CH2 into a Re−H−Re bond. Isotopic perturbation of the equilibria by partial deuteration demonstrated that the methyl bridges the Re−Re bond in an unsymmetrical way, with a fast exchange between one agostic and two terminal C−H bonds. At temperatures higher than 253 K, 2 decomposes, in THF solution, with CH4 elimination to give the novel red complex 1,2-eq,eq-[Re2(CO)8(THF)2] (3), which was characterized by NMR spectroscopy and X-ray analysis. In the solid form a staggered conformer of C 2 symmetry was found. 13C NMR analysis revealed the presence, in wet THF, of the aquo complexes [Re2(CO)8(THF)(H2O)] (4) and [Re2(CO)8(H2O)2] (5), whose formation is favored at low temperature (ΔH° for the formation of 5 from 4: −14.4(2) kJ mol-1). In solution, due to the lability of the THF ligands, 3 behaves as a “lightly stabilized” Re2(CO)8 fragment, capable of activating different E−H bonds. Reaction with HCl in THF leads to [Re2(μ-H)(μ-Cl)(CO)8], while with H2 the unsaturated starting material [Re2(μ-H)2(CO)8] is obtained. In THF solution, at room temperature, reactions with phenylacetylene, styrene, and acetaldehyde give the derivatives of C−H activation [Re2(μ-H)(μ-C⋮CPh)(CO)8], [Re2(μ-H)(μ-CHC(H)Ph)(CO)8], and [Re2(μ-H)(μ-η2-C(Me)O)(CO)8]. Moreover, the activation of an sp3 C−H bond in ethyl acetate occurs slowly when 3 is dissolved in the reactant itself, the resultant product being [Re2(μ-H)(μ-η2-CH2C(O)OEt)(CO)8].

Synthesis, Spectroscopic, and X-ray Characterization of Rhenium Carbonyl Complexes with Different Silsesquioxanes, as Models That Mimic the Chemical Behavior and the Topology of the Silica Surface

“…Finally In conclusion, this work and our previous investigation 16 have shown that by using silanolate ligands which better mimic the chemistry and topology of the silica surface it is reasonable to hypothesize that the first step of the interaction of [Re 2 (CO) 10 ] with the silica surface involves a [Re 2 (CO) 8 was prepared by following a reported procedure 23 and was usually contaminated with unreactive [Re 3 (µ-H) 3 (CO) 12 ] (ca. 10%), which could be easily removed after the reaction.…”

C–H and C–C bonds activation by iridium clusters: Synthesis and solid state structure of [Ir6(CO)14(μ3-η1:η2:η1-C7H8)]

“…Seminal studies on this subject have been performed on tri-and tetra-osmium clusters by Deeming et al [16], Shapley et al 10 , under UV irradiation [19], and on Re 2 (CO) 8 (THF) 2 [20]. As a result, cluster compounds containing g 2 -bound olefins are rather uncommon [21], and are usually stable at low temperature and in the presence of excess olefin [22].…”

[Re6(μ-H)5(CO)24]−: der erste Carbonylcluster mit einer cyclohexanartigen Struktur

“…[Re 6 (m-H) 5 (CO) 24 ] À : der erste Carbonylcluster mit einer cyclohexanartigen Struktur** Mirka Bergamo, Tiziana Beringhelli, Giuseppe DAlfonso,* Pierluigi Mercandelli, Massimo Moret* und Angelo Sironi Vor kurzem haben wir die Synthese des fünfkernigen ringförmigen Clusters [Re 5 (m-H) 4 (CO) 20 ] À beschrieben; [1] wir erhielten diesen durch die Cycloaddition des [Re 3 H 2 -(m-H) 2 (CO) 12 ] À -Anions und des Re 2 (CO) 8 -Fragments, das sich aus dem labilen Komplex [Re 2 (CO) 8 (thf) 2 ] [2] bildet (Schema 1). Die Reaktion beruht auf der wohlbekannten s-Donor-Fähigkeit von M-H-Bindungen gegenüber koordinativ Schema 1.…”

“…Dies könnte der Grund dafür sein, daû die zu 3 führende Cycloaddition weniger selektiv ist als die zum Re 5 -Ring führende Reaktion. [19] Experimentelles [Re 2 (m-H) 2 Neuartige ternäre Alkalimetallsilberacetylide M I AgC 2 (M I Li, Na, K, Rb, Cs)** Winfried Kockelmann und Uwe Ruschewitz* Vor kurzem konnten wir zeigen, daû durch Umsetzung von Na 2 C 2 mit Palladium oder Platin bei Temperaturen um 350 8C in einer Inertgasatmosphäre Na 2 PdC 2 und Na 2 PtC 2 hergestellt werden können. [1] Diese Verbindungen sind die ersten ternären Alkalimetallübergangsmetallacetylide.…”

“…Ihre Kristallstrukturen sind durch 1 I [M(C 2 ) 2À 2a2 ]-Ketten (M Pd, Pt) charakterisiert, die von den Natriumionen separiert werden. In der Zwischenzeit konnten wir diese Synthese auf die analogen Kalium-, Rubidium-und Caesiumverbindungen ausdehnen, [2] aber Versuche, ternäre Acetylide von anderen Übergangsmetallen durch diese Synthese herzustellen, blieben bislang erfolglos. 1963 wurde eine Synthese beschrieben, bei der das ternäre Silberacetylid KAgC 2 erhalten wurde.…”