Synthesis and Dynamic Properties of a Triruthenium Complex Containing μ₃-η²(∥)-Ethyne and μ₃-Methylidyne Ligands: Equilibrium of an Ethyne–Hydrido Complex with a Nonclassical μ₃-Vinyl Complex

Abstract

A triruthenium complex containing μ3-η2(∥)-ethyne and μ3-methylidyne ligands, (CpRu)3{μ3-η2(∥)-HCCH}­(μ3-CH)­(μ-H)2 (2a), was synthesized via the treatment of {Cp*Ru­(μ-H)}3(μ3-H)2 (3) (Cp* = η5-C5Me5) with propene. In the low-temperature region, VT 1H NMR spectra showed that complex 2a is in equilibrium with a nonclassical μ3-vinyl complex, (CpRu)3(μ3-η2:η2-HCCH2)­(μ3-CH)­(μ-H) (5a), which features an interaction between one of the β-vinyl protons and a Ru center. The presence of the unusual 3c-2e interaction of the β-C–H bond of the vinyl group is strongly supported by the small J C–H value (98 Hz) found for the β-carbon as well as the small J H–H value for the α-vinyl proton. Treatment of the equilibrated mixture of phenyl-substituted complexes (CpRu)3{μ3-η2(∥)-HCCPh}­(μ3-CH)­(μ-H)2 (2b) and (CpRu)3(μ3-η2:η2-HCCHPh)­(μ3-CH)­(μ-H) (5b) with tBuNC afforded a μ-styryl complex, (CpRu)3(μ-η2-HCCHPh)­(μ3-CH)­(μ-tBuNC)­(μ-H) (6), while analogous treatment of 2a and 5a resulted in the formation of μ3-dimetalloallyl complex (CpRu)3{μ3-η3-CHCHCN­(H)tBu}­(μ3-CH)­(μ-H) (7). These results imply that the coordinatively saturated μ3-η2(∥)-alkyne−μ3-alkylidyne complex can generate a vacant site via the migration of a hydrido ligand onto an alkyne ligand to yield a μ-vinyl intermediate.

Formation of a μ3-Acetylide on a Ru3 Cluster via Coupling of μ-Methylene with Isocyanide Accompanied by Elimination of Amine: A Model of Hydrogen-Assisted C–C Bond Formation on a Metal Surface

“…Instead, the hydride migrated to the nitrogen atom of the isocyanide, which resulted in the formation of μ-aminocarbyne intermediate A . Similar hydride transfer was observed in the reaction of a μ 3 -methylidyne-μ 3 -ethyne complex with t -BuNC, which yielded a μ 3 -dimetalloallyl complex containing a tert -butylamino group . Formation of a μ-aminocarbyne ligand via hydride migration is often reported in the reaction of di- and trinuclear hydrido complexes with isocyanide …”

“…Similar hydride transfer was observed in the reaction of a μ 3methylidyne-μ 3 -ethyne complex with t-BuNC, which yielded a μ 3 -dimetalloallyl complex containing a tert-butylamino group. 24 Formation of a μ-aminocarbyne ligand via hydride migration is often reported in the reaction of di-and trinuclear hydrido complexes with isocyanide. 25 The subsequent coupling of the μ-aminocarbyne with μmethylene afforded μ 3 -vinyl intermediate B-1.…”

The Mechanism of the Intramolecular Hydrocarbyl Metathesis within a Planar Triruthenium Cluster: Combining Core Flexibility with Hydride Mobility

“…This is obvious if we take into account that, while two of those H migrations must take place within each hydrocarbyl ligand, there is another one (from C8 into C5) whereby the H atom must cross the Ru 3 plane. In this sense, it is worth noting that the migration of bridging hydride ligands within this [19] and other [20] trinuclear complexes has been described, thus making likely their participation in the process. Nevertheless, to answer these questions the study was initiated by analysing whether 1,2‐H migrations within each hydrocarbyl ligand can take place without participation of μ‐H ligands or the metal centres (see Scheme 4).…”

“…There are two obvious mechanistic questionst hat one can think of at this point:a )inw hich order do these Hm igrations take place?A ssuming that each one represents an independente vent, there are six alternative ways or ordering them (see below); b) what is the most likely mechanism for each H migration and what is the role of the Ru 3 cluster?A sn oted above,i ti sl ogical to assume each of them has its own mechanistic details. This is obvious if we take into account that, while two of those Hm igrations must take place within each hydrocarbyl ligand,t here is another one (from C8 into C5) whereby the Ha tom must cross the Ru 3 plane.I nt his sense, it is worth noting that the migration of bridging hydride ligands within this [19] and other [20] trinuclear complexes has been described, thus making likely their participation in the process. Nevertheless, to answer these questions the study was initiated by analysing whether 1,2-H migrations within each hydrocarbyl ligand can take place withoutp articipation of m-H ligands or the metal centres (see Scheme 4).…”

Intramolecular Nitrene Transfer via the C≡N Bond Cleavage of Acetonitrile to a μ3-Alkylidyne Ligand on a Cationic Triruthenium Plane

“…A μ 3 -methylidyne-μ 3 -η 2 -ethyne complex has been shown to equilibrate with a β-agostic vinyl complex via reductive C–H bond formation between the μ 3 -η 2 -ethyne and hydride . A vacant site for the hydrogen uptake would be generated readily by the decoordination of the σ-coordinated C–H bond in the β-agostic vinyl group.…”