Patent ID: 7544800

Claim:
A carbene precursor having the structure of formula (PI) wherein: E 1 and E 2 are independently selected from N, NR E , O, P, PR E , and S, R E is hydrogen, heteroalkyl, or heteroaryl, x and y are independently zero, 1, or 2, and are selected to correspond to the valence state of E 1 and E 2 , respectively, and wherein when E 1 and E 2 are other than 0 or S, then E 1 and E 2 may be linked through a linking moiety that provides a heterocyclic ring in which E 1 and E 2 are incorporated as heteroatoms; R 1 and R 2 are independently selected from branched C 3 -C 30 hydrocarbyl, substituted branched C 3 -C 30 hydrocarbyl, heteroatom-containing branched C 4 -C 30 hydrocarbyl, substituted heteroatom-containing branched C 4 -C 30 hydrocarbyl, cyclic C 5 -C 30 hydrocarbyl, substituted cyclic C 5 -C 30 hydrocarbyl, heteroatom-containing cyclic C 1 -C 30 hydrocarbyl, and substituted heteroatom-containing cyclic C 1 -C 30 hydrocarbyl; L 1 and L 2 are linkers containing 1 to 6 spacer atoms, and are independently selected from heteroatoms, substituted heteroatoms, hydrocarbylene, substituted hydrocarbylene, heteroatom-containing hydrocarbylene, and substituted heteroatom-containing hydrocarbylene; m and n are independently zero or 1; and R 7 is selected from heteroalkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl, substituted with at least one electron-withdrawing substituent, with the proviso that, when R 7 is heteroalkyl, then the at least one electron-withdrawing substituent is selected from the group consisting of fluoro, fluoroalkyl, chloro, nitro, and acytyl.