Surface Organometallic Chemistry:  A New Synthesis of [Re₂(CO)₆(μ-OH)₃]^-from [Re(CO)₃OH]₄Supported on a Silica Surface Added with K₂CO₃; Evidence of Its Thermal Binding to the Surface via Re−O−Si⋮ Bonds Confirmed by the Synthesis of the Molecular Models [Re₂(CO)₆(μ-OH)_x(μ-OSiEt₃)_3-x]^-(x= 0, 1, or 2) by Reaction of [Re₂

Abstract

Reaction at 25 °C of [Re(CO) 3 OH] 4 on a silica surface added with K 2 CO 3 affords physisorbed K[Re 2 (CO) 6 (µ-OH) 3 ] which is anchored to the silica surface by further treatment at 200 °C. This novel surface chemistry is easily mimicked in solution: reaction of [Re(CO) 3 OH] 4 with K 2 CO 3 or [NEt 4 ]OH in water represents a new convenient synthesis for [Re 2 (CO) 6 (µ-OH) 3 ]which can be converted into the molecular models [Re 2 (CO) 6 (µ-OH) x (µ-OSiEt 3 ) 3-x ] -(x ) 0, 1, or 2) by reaction with Et 3 SiOH under well-defined conditions.

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

“…Very recently some of us reported on various anionic rhenium carbonyl species [Re 2 (CO) 6 (μ-OH) 3− x (μ-OSiEt 3 ) x ] − ( x = 1−3), obtained by reaction of [Re 2 (CO) 6 (μ-OH) 3 ] − with Et 3 SiOH, which can be considered models of silica-anchored species involving these anionic rhenium carbonyl moieties . Moreover, during our investigation on some aspects of the surface organometallic chemistry of [Re 2 (CO) 10 ] or [Re(CO) 3 OH] 4 supported on silica we obtained the unexpected evidence of a [Re(CO) 5 OSi] species encapsulated on the silica surface .…”

“…Other models of rhenium carbonyl surface species were synthesized and structurally characterized, such as the species [Re 2 (CO) 8 (μ-H)(μ-OSiR 2 R′)] (R = Et, Ph; R′ = Et, Ph, OH, OSiPh 2 OH), where the OSiR 2 R′ group may mimic the interaction with isolated, geminal, and vicinal surface silanols. By analogy with the known easy anchoring of [Os 3 (CO) 12 ] on the silica surface by oxidative addition to give the silica-anchored [Os 3 (CO) 10 (μ-H)(μ-OSi)] species, as confirmed by surface models, the latter Re complexes could be models of the silica-anchored [Re 2 (CO) 8 (μ-H)(μ-OSi)] species possibly formed by thermal or photochemical oxidative addition of [Re 2 (CO) 10 ] with the silica surface. , …”

“…Although models of silica-anchored carbonyl species of various noble metals (for example Rh, Os, , and Ru) have been thoroughly investigated, much less is known about models involving oxophilic metals such as rhenium, , despite the industrial relevance of catalysts based on rhenium supported on inorganic oxides for reactions such as olefin metathesis, epoxidation, hydrogenation, dehydrogenation, and petroleum refining…”

Organometallic Chemistry: Structural Isomerization Reactions in Confined Environments

“…[14Ϫ16] The methodology has also been exploited for the synthesis of organometallic complexes that can subsequently be extracted from surfaces. [17] …”

Low-Temperature Nucleophilic Attack of Me3SiO−and MeO−on Rhenium(I) and Rhenium(0) Carbonyl Complexes

“…The understanding of the structure and reactivity of silica-anchored organometallic species has improved by the help of the complementary synthesis of molecular models bearing silanolato ligands which mimic the silanol groups of the silica surface. − To get a more detailed insight into the surface organometallic chemistry involving rhenium carbonyl species supported on silica, recently some of us investigated silanolato carbonyl rhenium complexes in order to confirm the evidence of the silica-anchored rhenium pentacarbonyl species [Re(CO) 5 OSi], generated under CO from silica-supported [Re(CO) 3 OH] 4 . Such a surface species was unexpected, since organometallic species of the type [Re(CO) 5 OR] (R = alkyl, aryl) have so far eluded isolation, due to the strong cis-labilizing power of OR − groups, which favors the formation of dimeric complexes containing Re(CO) 3 units joined by alkoxo bridging groups. , The attempted synthesis of a molecular model of the silica-anchored [Re(CO) 5 OSi] by reaction of [Re(CO) 5 Cl] with Me 3 SiONa did not give the expected [Re(CO) 5 OSiMe 3 ] derivative.…”