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Facile Formation of a Rhenium Allenylcarbene Complex with an Internal Dithioalkyne
Author(s) -
Seidel Wolfram W.,
Meel Matthias J.,
Schallenberg David,
Pape Tania,
Villinger Alexander,
Michalik Dirk
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201000370
Subject(s) - cyclobutadiene , alkyne , chemistry , ring (chemistry) , rhenium , carbene , crystallography , resonance (particle physics) , ring strain , stereochemistry , polymerization , bond length , triple bond , crystal structure , double bond , molecule , polymer chemistry , catalysis , organic chemistry , physics , polymer , particle physics
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 favorable over the isomeric η 4 ‐cyclobutadiene complex 3a with four thiobenzyl substituents, while the opposite holds true for the phenyl‐substituted derivative. According to calculations on potential intermediates and transition states, the rate‐determining step is the conversion of a bis(alkyne) into a mixed alkyne/vinylidene complex by 1,2‐SBn shift, while the formation of 3 via the η 4 ‐cyclobutadiene complex 3a is improbable. Allenyl carbene complexes are of great interest as alkyne polymerization intermediates.