Time-resolved IR characterization of cis- and trans-[LW(CO)4(solvent)] [L = PPh3, P(OCHMe2)3, and P(OEt)3] in n-heptane solution. The solvent as a token ligand in short-lived reaction intermediates

Abstract

282ChemInform Abstract Time-resolved IR studies provide confirmation that both title isomers are important intermediates in the photolysis of LW(CO)5 and cis-(Pip)LW(CO)4 compounds (Pip: piperidine). These isomers react with CO at different rates, indicating that these isomers are not stereochemically interconvertible on the time scale of their reaction with CO even in a solvent as nonpolar as n-heptane. All of these formally unsaturated species appear to be solvated to give pseudooctahedral quasicoordination compounds. The term "Token Ligand" is proposed to signify this specific interaction of a solvent molecule with an otherwise vacant coordination site in reaction intermediates.

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

“… 41 We show here that the rhodium sigma-alkane complex [1-NBA][BAr F 4 ] (that is prepared by solid/gas routes itself) acts as a synthetic starting point for a variety of reactive and unusual alkene complexes that are challenging to prepare pure by solution routes. The alkane thus acts as “token” ligand, 121 and it is the unique environment provided by the solid-state packing of anions that allows for such single-crystal to single-crystal transformation to occur at such reactive but well-defined molecular cations. When experimental observations are combined with periodic DFT and chemical shift calculations a very complete picture of structure, mobility and reactivity in the solid-state can be formed, as we have also recently demonstrated in [1-NBA][BAr F 4 ] and other systems.…”

New Directions in Inorganic and Metal-Organic Coordination Chemistry in Supercritical Fluids

“…The work of Turner, briefly mentioned above, has left no doubt that, in solution, most 402 if not all 403 coordinatively unsaturated metal centers interact with the solvent. SCFs offer unique opportunities to study such interactions because the density of the solvent can be varied without changing many of the other reaction parameters (T, concentration of the reactants, etc.).…”

Solid–State Molecular Organometallic Catalysis in Gas/Solid Flow (Flow-SMOM) as Demonstrated by Efficient Room Temperature and Pressure 1-Butene Isomerization

“…This allows for the synthesis of a range of cationic σ-alkane complexes. , For example, [Rh­(Cy 2 PCH 2 CH 2 PCy 2 )­(η 2 η 2 –NBA)]­[BAr F 4 ], 2 , Scheme A, comes from hydrogenation of a diene-precursor, i.e., [Rh­(Cy 2 PCH 2 CH 2 PCy 2 )­(η 2 η 2 –NBD)]­[BAr F 4 ] 1 (NBA = norbornane, NBD = norbornadiene, Ar F = (CF 3 ) 2 C 6 H 3 ). ,− This reactivity and stability is facilitated by the [BAr F 4 ] − anions that form a well–defined (often) octahedral cage in the solid–state, providing a nanoreactor around the reactive cation. Moreover, the alkane ligand in 2 acts as a weakly bound “token” ligand that can be displaced in a SC–SC transformation by simple alkenes (e.g., propene and butene) to form, in the solid-state, complexes exemplified by [Rh­(Cy 2 PCH 2 CH 2 PCy 2 )­(propene)]­[BAr F 4 ], 3 , in which the alkene binds as a π-ligand with supporting agostic Rh···H 3 C interactions (Scheme B) . In the solid-state at 298 K the propene ligand undergoes a rapid, reversible, degenerate 1,3-hydride shift via an π-allyl intermediate ( I ), a key step in alkene isomerization…”