TY - JOUR
T1 - One-Electron Oxidation of a Disilicon(0) Compound
T2 - An Experimental and Theoretical Study of [Si2]+ Trapped by N-Heterocyclic Carbenes
AU - Arz, Marius I.
AU - Straßmann, Martin
AU - Meyer, Andreas
AU - Schnakenburg, Gregor
AU - Schiemann, Olav
AU - Filippou, Alexander C.
N1 - Publisher Copyright:
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - One-electron oxidation of the disilicon(0) compound Si2(Idipp)2 (1, Idipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with [Fe(C5Me5)2][B(ArF)4] (ArF=C6H3-3,5-(CF3)2) affords selectively the green radical salt [Si2(Idipp)2][B(ArF)4] (1-[B(ArF)4). Oxidation of the centrosymmetric1 occurs reversibly at a low redox potential (E1/2=-1.250V vs. Fc+/Fc), and is accompanied by considerable structural changes as shown by single-crystal X-ray structural analysis of 1-B(ArF)4. These include a shortening of the S-Si bond, a widening of the Si-Si-CNHC angles, and a lowering of the symmetry, leading to a quite different conformation of the NHC substituents at the two inequivalent Si sites in 1+. Comparative quantum chemical calculations of 1 and 1+ indicate that electron ejection occurs from the symmetric (n+) combination of the Si lone pairs (HOMO). EPR studies of 1-B(ArF)4 in frozen solution verified the inequivalency of the two Si sites observed in the solid-state, and point in agreement with the theoretical results to an almost equal distribution of the spin density over the two Si atoms, leading to quite similar 29Si hyperfine coupling tensors in 1+. EPR studies of 1-B(ArF)4 in liquid solution unraveled a topomerization with a low activation barrier that interconverts the two Si sites in 1+. The radical salt [Si2(Idipp)2][B(ArF)4] was obtained upon one-electron oxidation of the disilicon(0) compound Si2(Idipp)2. The open-shell compound was characterized by experimental and quantum-chemical methods, providing a detailed insight into the unusual electronic structure and bonding situation of this σ-type radical.
AB - One-electron oxidation of the disilicon(0) compound Si2(Idipp)2 (1, Idipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with [Fe(C5Me5)2][B(ArF)4] (ArF=C6H3-3,5-(CF3)2) affords selectively the green radical salt [Si2(Idipp)2][B(ArF)4] (1-[B(ArF)4). Oxidation of the centrosymmetric1 occurs reversibly at a low redox potential (E1/2=-1.250V vs. Fc+/Fc), and is accompanied by considerable structural changes as shown by single-crystal X-ray structural analysis of 1-B(ArF)4. These include a shortening of the S-Si bond, a widening of the Si-Si-CNHC angles, and a lowering of the symmetry, leading to a quite different conformation of the NHC substituents at the two inequivalent Si sites in 1+. Comparative quantum chemical calculations of 1 and 1+ indicate that electron ejection occurs from the symmetric (n+) combination of the Si lone pairs (HOMO). EPR studies of 1-B(ArF)4 in frozen solution verified the inequivalency of the two Si sites observed in the solid-state, and point in agreement with the theoretical results to an almost equal distribution of the spin density over the two Si atoms, leading to quite similar 29Si hyperfine coupling tensors in 1+. EPR studies of 1-B(ArF)4 in liquid solution unraveled a topomerization with a low activation barrier that interconverts the two Si sites in 1+. The radical salt [Si2(Idipp)2][B(ArF)4] was obtained upon one-electron oxidation of the disilicon(0) compound Si2(Idipp)2. The open-shell compound was characterized by experimental and quantum-chemical methods, providing a detailed insight into the unusual electronic structure and bonding situation of this σ-type radical.
KW - N-heterocyclic carbenes
KW - multiple bonds
KW - radical ions
KW - silicon
UR - http://www.scopus.com/inward/record.url?scp=84939471442&partnerID=8YFLogxK
U2 - 10.1002/chem.201502199
DO - 10.1002/chem.201502199
M3 - Article
AN - SCOPUS:84939471442
SN - 0947-6539
VL - 21
SP - 12509
EP - 12516
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 35
ER -