Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates

Abstract

Solid-state molecular organometallic catalysis (SMOM-cat): synthetic routes, unique structural motifs, mobility in the solid-state and very active gas/solid isomerization catalysts.

Reversible Encapsulation of Xenon and CH2Cl2 in a Solid‐State Molecular Organometallic Framework (Guest@SMOM)

“…Solid-state molecular organometallic chemistry (SMOM-Chem) [1] offers opportunities in synthesis and catalysis using well-defined organometallic species in single-crystal to singlecrystal (SC-SC) transformations. [2] Forexample,the isolation and characterization of s-alkane complexes in the solid state is achieved by as imple solid/gas SC-SC hydrogenation reaction of an alkene precursor such as [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(NBD)][BAr F 4 ]( NBD = norbornadiene,A r F = 3,5-(CF 3 ) 2 C 6 H 3 )t of orm the corresponding salkane complex, [BAr F 4 ] (Figure 1; norbornane = NBA).…”

“…Thes tability of these SMOM systems allows for these s-complexes to undergo further SC-SC transformations.For example,reaction with D 2 (leading to CÀH/CÀDe xchange at the alkane), [7,8] H 2 loss (acceptorless alkane dehydrogenation) [7] or substitution of the NBAligand, e.g.,F igure 1B. [1,7] Key to this reactivity is the well-defined confined microenvironment provided in the solid state by the [BAr F 4 ] À anions that provide arelatively robust encapsulating framework-related to MOFs [9] or supramolecular catalysts. [10] This supports the structural reorganization associated with the reactive metal center and also allows reversible access for gases and small organic compounds,albeit in what is essentially an on-porous material.…”

“…[10] This supports the structural reorganization associated with the reactive metal center and also allows reversible access for gases and small organic compounds,albeit in what is essentially an on-porous material. [1] That s-alkane complexes are unstable and transient in solution, even at low temperature, [11] demonstrates the stabilizing effect of the noncovalent anion microenvironment. While these systems also promote catalysis (e.g.…”

“…[1] That s-alkane complexes are unstable and transient in solution, even at low temperature, [11] demonstrates the stabilizing effect of the noncovalent anion microenvironment. [1,12] Ak ey question, then, is how substrate/product molecules move in and out of the crystalline lattice on the timescale of synthesis (minutes to hours). 1-butene isomerization) this may occur at, or close to,t he crystal surface.…”

“…However,a fter one week an ew, Xe@SMOM, product is formed, [Rh(Cy 2 PCH 2 PCy 2 )(NBD)]-[(Xe) 0.5 &BAr (3) ]. This provides aclue as to how gases (e.g.H 2 /D 2 , [8] hydrocarbons, [1] CO [12] )are primed for reaction at the metal center in solid/gas SC-SC SMOM reactions.M oreover,i nspection of the extended packing diagram of .W hen coupled with the encapsulated microenvironment in which the Rh-center sits,t here is aremarkable similarity between these guest@SMOM systems the hydrophobic channels that direct substrates and products towards,a nd away from, the active sites in metalloenzymes such as soluble methane monooxygenase hydroxylase or hydrogenases [21a-c] Thee ncapsulation of Xenon can also be followed by 31 P{ 1 H} and 129 Xe SSNMR spectroscopy at 298 K. Af reshly prepared sample of [2-NBD][(Xe) 0.5 &BAr F 4 ] was packed under an atmosphere of Xe (atmospheric pressure). Welldefined Xe···F intermolecular contacts are rare.E xamples include:[ C 6 F 5 Xe][B(CF 3 ) 4 ] À [Xe···F = 2.913(4) ], [29] Xe-(C 6 F 5 ) 2 [Xe···F 3.30(1)-3.536(9) ].…”