Facile Formation of a Rhenium Allenylcarbene Complex with an Internal Dithioalkyne

Abstract

The η 2 -alkyne complex [(η 5 -C 5 H 5 )Re(1)Br 2 ], 2, (1 = BnSC 2 SBn) reacts with an excess of the dithioalkyne 1 to give the addition product [(η 5 -C 5 H 5 )ReBr 2 {η 3 -(BnS) 2 C 2 C(SBn)-C(SBn)}], 3, displaying a ReC 3 ring with an exocyclic double bond. The molecular structures of the complexes 2 and 3 were determined by single-crystal X-ray diffraction. The nonplanarity of the ReC 3 ring and the largely equal C-C bond lengths within the ring reveal 3 to be a resonance hybrid of an allenylcarbene complex and a folded rhenacyclobutene system. DFT calculations show that complex type 3 is

Square Planar Coordination of Silver in a η4‐Cyclobutadiene‐(η5‐C5H5)ReBr2 Complex Framework

“…In turn, the Re–Br distances are affected only marginally by the Ag + coordination. The bond lengths Re1–Br1 and Re1–Br2 in 8 + at 2.5565(7) and 2.5603(5) Å, respectively, are only slightly shortened compared with 2.574(4) and 2.581(4) Å in 4a …”

“…The outcome of the reaction of [(η 5 ‐C 5 H 5 )Re(CO) 2 X 2 ], ( X = Br, I), with tolane or the related sulfide derivative C 2 (SBn) 2 can partially be controlled by stoichiometry and reaction time. The alkyne complexes 1a , 2a (Scheme ), and [(η 5 ‐C 5 H 5 )Re{C 2 (SBn) 2 )I 2 ] ( 2b ) are the main products, if the alkynes were applied in moderate excess with short reaction times. Herein, the iodido derivative 2b was isolated and fully characterized.…”

“…Extension of the reaction time and increase of the alkyne excess forced to the addition of a second alkyne equivalent but resulting in a different connectivity. For the sulfur‐based derivative 2a formation of the allenylcarbene complex 3 as C4 building block was observed . In contrast, the η 4 ‐cyclobutadiene complex 4a was prepared from [(η 5 ‐C 5 H 5 )Re(CO) 2 Br 2 ] and an excess of tolane in boiling toluene according to Dossett et al The respective iodido derivative 4b proved accessible by the same procedure using [(η 5 ‐C 5 H 5 )Re(CO 2 )I 2 ].…”

“…In preceding studies we found that the Re III complex [(η 5 ‐C 5 H 5 )Re(CO) 2 Br 2 ] reacted at elevated temperature with bis(benzylsulfanyl)acetylene to yield the rhenaallenylcarbene complex 3 by 1,2 shift of one benzylsulfanyl substituent (Scheme ) . In contrast, Green at al.…”

“…Mechanistic conceptions almost always include the formation of intermediate metallacyclopentadienes . In this conjunction, the formation and interconvertion of alternatively connected products by combination of two alkynes and a central metal atom are of interest either as bypasses like η 4 ‐cyclobutadiene and η 3 ‐allenylcarbene, complexes or as potential intermediates like folded metallacyclopentatrienes , …”