CATALYTIC FUNCTIONALIZATION OF C-H BONDS BY ISONITRILE INSERTION - PREPARATION, CHARACTERIZATION, AND REACTIVITY OF RHCL(PR3)2(CNR')

A series of complexes of the type trans-RhCl(PR3)2(CNR'), where R = Me, Et, i-Pr and R' = neopentyl, 2,6-xylyl, or Me, have been prepared and examined for C-H bond activation. All of the neopentyl complexes produce 2,2-dimethyl-5-phenyl-4-aza-4-pentene (5a) upon irradiation in benzene solvent. In the presence of low concentrations of added isonitrile the production of 5a is catalytic, with the R = isopropyl giving the highest yields. Two of the precursors were structurally characterized. The trans-RhCl[P(i-Pr)3]2- (CNCH2CMe3) (2c) crystallizes in the monoclinic space group P21/c with a = 13.894 (5) Å, b = 12.014 (6) Å, c = 18.896 (9) Å, β = 103.58 (4)°, V = 3066 (5) Å3, and Z = 4. The complex trans-RhCl[P(i-Pr)3]2- (CN-2,6-xylyl) (2e) crystallizes in orthorhombic space group Pnna with a = 14.620 (2) Å, b = 16.07 (2)Å, c = 15.358 (4) Å,V= 3608 (5) Å3, and Z = 4. At higher concentrations, a solution of 2c and neopentyl isocyanide in benzene produces the complex {trans-Rh[P(i-Pr)3]2(CNCH2CMe3)2}+Cl- (3a), which precipitates from solution. Complex 3a crystallizes in the monoclinic space group P21/n with a = 11.633 (3) Å, b = 13.945 (3) Å, c = 23.050 (9) Å, β = 92.69 (2)°, V = 3735 (3) Å3, and Z = 4. Complex 3a is also found to serve as a catalyst for production of 5a, but the PF6- salt 3b is inactive. © 1990, American Chemical Society. All rights reserved.