Effects of substituents on the formation of rhenium carbyne and η2-vinyl complexes from the reactions of ReH5(PMe2Ph)3 with terminal alkynes

Abstract

The reactions of the rhenium polyhydride complex ReH 5 (PMe 2 Ph) 3 with HCRCAr (Ar = p-C 6 H 4 CF 3 , o-C 6 H 4 CF 3 , o-C 6 H 4 Me and o-C 6 H 4 Br) have been carried out. Treatment of ReH 5 (PMe 2 Ph) 3 with HCRC(p-C 6 H 4 CF 3 ) in the presence of two equiv. of HCl produces a mixture of the carbyne complex Re(RCCH 2 (p-C 6 H 4 CF 3 ))Cl 2 (PMe 2 Ph) 3 and the Z 2 -vinyl complex Re(Z 2 -CH 2 C(p-C 6 H 4 CF 3 ))Cl 2 (PMe 2 Ph) 3 . Treatment of ReH 5 (PMe 2 Ph) 3 with HCRCAr (Ar = o-C 6 H 4 CF 3 , o-C 6 H 4 Me, o-C 6 H 4 Br) in the presence of two equiv. of HCl produces only the carbyne complexes Re(RCCH 2 Ar)Cl 2 (PMe 2 Ph) 3 . The mechanism of the reactions of ReH 5 (PMe 2 Ph ) 3 with HCRCR has also been studied with the aid of DFT calculations, which suggests that the reactions are kinetically controlled and the pathways leading to the carbyne and Z 2 -vinyl complexes are influenced by the steric and electronic effects of the substituents of the alkynes.Scheme 1 Reaction of ReH 5 (PMe 2 Ph) 3 with terminal alkynes.

Alkyne Metathesis Reactions of Rhenium(V) Carbyne Complexes

“…We have recently synthesized d 2 Re­(V) carbyne complexes of the type mer -Re­(CR)­Cl 2 (PMe 2 Ph) 3 . We reasoned that such carbyne complexes could undergo substitution reactions with alkynes to give alkyne-carbyne complexes with a structural feature similar to that of 8 , and therefore they may undergo cycloaddition or metathesis reactions with alkynes.…”

Synthesis of Rhenium Vinylidene and Carbyne Complexes from Reactions of [Re(dppm)3]I with Terminal Alkynes and Alkynols

“…The complex (mq)­(PPh 3 ) 2 HReCCH 2 R (mq = the anion of 2-mercaptoquinoline) was produced by deprotonation of [(mq)­(PPh 3 ) 2 H 2 ReCCH 2 R]­PF 6 . The complexes ReCl 2 (CCH 2 R)­(PMe 2 Ph) 3 and ReCl 2 (CCHCRR′)­(PMe 2 Ph) 3 were obtained in low yields from the reactions of ReH 5 (PMe 2 Ph) 3 with HCCR and HCCC­(OH)­RR′ in the presence of HCl. , The complex [Cp*Re­(CCMe 3 )­(PMe 3 ) 2 ]Cl was prepared by the reaction of Cp*ReCl 2 (CCMe 3 ) with excess PMe 3 …”

Tantalum η2-Vinyl Complexes Bearing an [η5:σ-Me2C(C5H4)(C2B10H10)]2– Ligand: Syntheses and Structural Characterizations

“…Transition-metal η 2 -vinyl complexes, also known as 1-metallacyclopropenes, in which both vinyl carbon atoms are bound to a single metal center, constitute an important subset of metal alkenyl complexes (Chart ). They are conceivable intermediates in various stoichiometric or catalytic reactions, such as insertion, oligomerization, cycloaddition, hydrogenation, and hydrofunctionalization of alkynes. , In these processes, the η 2 -vinyl ligand is thought to stabilize the unsaturated metal center, to interconvert with η 1 -vinyl ligands, and to have an impact on the regio- and stereochemistry of the products. − ,,− ,, Isomerization of metal η 2 -vinyl complexes to metal carbene, carbyne, vinylidene, allene, and η 3 -allyl complexes was also well demonstrated. ,, In the last few decades, numerous η 2 -vinyl complexes of Cr, Mo, W, Re, and Os have been isolated, which were generally synthesized via insertion or nucleophilic/electrophilic addition of alkyne ligands. ,, However, isolable η 2 -vinyl complexes beyond groups 6–8 transition metals remain unknown. Group 9 and 10 metal complexes are commonly too electron-rich to accommodate the π-electrons from the alkenyl moiety, while group 4 and 5 transition metals are mostly at their highest oxidation state, missing an occupied d orbital appropriate for π-backdonation to the alkenyl π* orbital .…”