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Summary: Different electronic structure of phosphonyl radical adducts of N-heterocyclic
carbenes, silylenes and germylenes: EPR spectroscopic study and DFT
calculations
Dennis Sheberla,a
Boris Tumanskii,*a
Adam C. Tomasik,b
Amitabha Mitra,b
Nicholas J. Hill,b
Robert West*b
and Yitzhak Apeloiga
Received 21st January 2010, Accepted 18th March 2010
DOI: 10.1039/c0sc00143k
Stable N-heterocyclic carbenes and germylenes were allowed to react with a phosphonyl radical,
(i-PrO)2(O)P (7), generated by photolysis of [(i-PrO)2(O)P]2Hg. The products were identified by EPR
spectroscopy. An unsaturated carbene (1) and germylene (3) react with 7 at the divalent atom to give
unstable radical products (s½ ¼ 0.2 s). A benzo-annulated carbene (4) and a saturated germylene (6)
react with 7 to give more active radicals. An unsaturated (2) and a saturated silylene (5) undergo rapid
reaction (in the dark) with [(i-PrO)2(O)P]2Hg to yield unusual silyl phosphites. In these cases only
secondary radicals were observed. DFT (PBE0/TZVP//B3LYP/6-31+G(d)) calculations of the radical
adducts of the different (C, Si, Ge) unsaturated N-heterocyclic divalent species with the phosphonyl
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