PHOTOLYSIS OF TP'RH(CN-NEOPENTYL)(ETA-2-PHN=C=N-NEOPENTYL) IN ALKANES AND ARENES - KINETIC AND THERMODYNAMIC SELECTIVITY OF [TP'RH(CN-NEOPENTYL)] FOR VARIOUS TYPES OF C-H BONDS

Irradiation of the carbodiimide complex [HB(3,5-dimethylpyrazolyl)3]Rh(CNR)(PhN=C=NR) (R = neopentyl) in benzene, toluene, mesitylene, cyclopentane, cyclohexane, propane, or pentane solvent leads to both the clean elimination of the carbodiimide ligand and the formation of the C-H oxidative addition product [HB(3,5-dimethylpyrazolyl)3]Rh(CNR)(R')H. These products have been isolated as their chloride derivatives. Methane can be activated by exchange with the cyclohexyl derivative. The n-pentyl derivative [HB(3,5-dimethylpyrazolyl)3]Rh(CNR)(n-pentyl)Cl crystallizes in monoclinic space group P2(1)/c with a = 8.8865 (28) angstrom, b = 11.8016 (30) angstrom, c = 31.4597 (14) angstrom, beta = 90.727 (22)-degrees, Z = 4, and V = 3098 (2) angstrom3. Competitive studies show that both benzylic and aromatic C-H bonds react under conditions of kinetic control but that the aromatic activation products are thermodynamically preferred. Activation of primary alkane C-H bonds is preferred over secondary activation. This complex is found to be more selective than either [Cp*Rh(PMe3)] or [Cp*Ir(PMe3)]. The rates of reductive elimination of n-pentane, cyclopentane, cyclohexane, mesitylene, methane, and benzene have been measured and are used to establish relative Rh-R bond strengths for these ligands.