Competitive carbon-sulfur vs carbon-carbon bond activation of 2-cyanothiophene with [Ni(dippe)H]2.
The processes of C-C and C-S bond cleavage have been studied with the homogeneous organometallic compound [Ni(dippe)H](2) (1). When 1 is reacted with 2-cyanothiophene at room temperature, cleavage of the nitrile-substituted C-S bond occurs, forming the Ni-metallacycle complex (dippe)Ni(kappa(2)-S,C-SCH=CHCH=C(CN)) (2a), which has been fully characterized by NMR spectroscopy and X-ray diffraction. 2a was converted to the C-CN cleavage product (dippe)Ni(CN)(2-thiophenyl) (3) when heated in solution. On closer inspection, four other intermediates were observed by (31)P NMR spectroscopy at low temperature. Structures for the intermediates were elucidated through a combination of independent synthesis, theoretical calculations, chemical characterization, and experimental precedent. A kinetic product (dippe)Ni(kappa(2)-S,C-SC(CN)=CHCH=CH) (2b) was formed from cleavage of the nonsubstituted C-S bond, as well as a Ni(0) eta(2)-nitrile intermediate, (dippe)Ni(eta(2)-C,N-2-cyanothiophene) (4), and a dinuclear mixed Ni(0)-Ni(II) product (6b). A complete DFT analysis of this system has been carried out to reveal comparative details about the two bond cleavage transition states.
Grochowski
Matthew R
MR
Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
Li
Ting
T
Brennessel
William W
WW
Jones
William D
WD
D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*
D009942:Organometallic Compounds; D013876:Thiophenes; D013455:Sulfur; D002244:Carbon