SELECTIVITY IN THE ACTIVATION OF FLUORINATED AROMATIC-HYDROCARBONS BY[(C5H5)RH(PME3)] AND [(C5ME5)RH(PME3)]

Thermolysis of (C5Me5)Rh(PMe3)(Ph)H (1) in neat fluorobenzene, o-diflu orobenzene, p-difluorobenzene, or 1,3,5-trifluorobenzene results in th e formation of the new aryl hydride complexes (C5Me5)Rh(PMe3)(aryl(F)) H (aryl(F) = 2-C6H4F, 2,3-C6H3F2,2,5-C6H3F2, or 2,4,6-C6H2F3). Short t erm thermolysis of 1 in m-difluorobenzene produces a kinetic mixture o f products resulting from activation of all possible C-H bond position s. Continued thermolysis of this mixture results in exclusive formatio n of the thermodynamic product (C5Me5)Rh(PMe3)(2,6-C6H3F2)H. Irradiati on Of (C5Me5)Rh(PMe3)H2 in o-difluorobenzene at -30-degrees-C gives bo th (C5Me5)-Rh(PMe3)(2,3-C6H3F2)H and (C5Me5)Rh(PMe3)(3,4-C6H3F2)H as t he kinetic products. Thermolysis of this mixture results in exclusive formation of the thermodynamic product (C5Me5)-Rh(PMe3)(2,3-C6H3F2)H. These aryl hydrides are readily converted to their bromo derivatives b y reaction with bromoform. Photochemical reaction of (C5H5)Rh(PMe3)(C2 H4)(2) with o-, m-, and p-difluorobenzene, 1,3,5-trifluorobenzene, 1,2 ,4,5-tetrafluorobenzene, or pentafluorobenzene at room temperature giv es single aryl hydride products (C5H5)Rh(PMe3)(aryl(F)H (aryl(F) = 2,3 -C6H3F2, 2,6-C6H3F2, 2,5-C6H3F2, 2,4,6-C6H2F3, 2,3,5,6-C6HF4, or C6F5) in which C-H insertion occurs adjacent to a fluorine. Photochemical r eaction of 2 with alpha,alpha,alpha-trifluorotoluene gives both m- and p-trifluorotolyl insertion products. These compounds are also convert ed to their bromo derivatives by reaction with bromoform. Photochemica l reaction of 2 with 2,3,4,5,6-pentafluorotoluene gives an eta2-arene complex with metal coordination in the 3,4 positions. The (C5Me5)Rh(PM e3)(aryl(F)Br complexes were structurally characterized. (C5Me5)Rh(PMe 3)(2,3-C6F2H3) crystallizes in monoclinic space group C2/c (No. 15) wi th Z = 8, a = 14.071(9) angstrom, b = 9.640(5) angstrom, c = 30.774(12 ) angstrom, beta = 97.48(4)degrees, and V = 4139(7) angstrom3. (C5Me5) Rh(PMe3)(2,4-C6F2H3) crystallizes in monoclinic space group C2/c (No. 15) with Z = 8, a = 14.073(8) angstrom, b = 9.505(3) angstrom, c = 30. 910(10) angstrom, beta = 97.30(5)degrees and V = 4101(5) angstrom3, an d also in monoclinic space group P2(1)/c (No. 14) with Z = 4, a = 9.40 1(6) angstrom, b = 11.595(4) angstrom, c = 18.809(8) angstrom, beta = 91.38(4)degrees, and V = 2049(3) angstrom3. (C5Me5)Rh(PMe3)(2,4,6-C6F3 H3) crystallizes in monoclinic space group C2/c (No. 15) with Z = 8, a = 14.263(9) angstrom, b = 9.492(2) Angstrom, c = 30.917(17) angstrom, beta = 97.99(2)degrees, and V = 4145(6) angstrom3.