THERMAL AND PHOTOCHEMICAL SUBSTITUTION-REACTIONS OF CPRE(PPH3)(2)H-2 AND CPRE(PPH3)H-4 - CATALYTIC INSERTION OF ETHYLENE INTO THE C-H BOND OF BENZENE

The thermal and photochemical reactions of CpRe(PPh3)(2)H-2 and CpRe(P Ph3)H-4 (Cp = eta(5)-C5H5) with PMe3, P(p-tolyl)(3), PMe2Ph, DMPE, DPP E, DPPM, CO, 2,6-xylylisocyanide and ethylene have been examined. Whil e CpRe(PPh3)(2)H-2 is thermally inert, it will undergo photochemical s ubstitution of one or two PPh3 ligands. With ethylene, substitution is followed by insertion of the olefin into the C-H bond of benzene, giv ing ethylbenzene. CpRe(PPh3)H-4 undergoes thermal loss of PPh3, which leads to substituted products of the type CpRe(L)H-4. Photochemically, reductive elimination of dihydrogen occurs preferentially. The comple x trans-CpRe(DMPE)H-2 was structurally characterized, crystallizing in the monoclinic space group P2(1)/n (No. 14) with a=6.249(6), b=16.671 (8), c=13.867(7) Angstrom, beta=92.11(6)degrees, V=1443.7(2.9) Angstro m(3) and Z = 4. The complex trans-CpRe(PMe2Ph)(2)H-2 was structurally characterized, crystallizing in the monoclinic space group P2(1)/n (No . 14) with a=7.467(3), b=23.874(14), c=11.798(6) Angstrom, beta=100.16 (4)degrees, V=2070.2(3.4) Angstrom(3) and 2=4. (C) 1998 Elsevier Scien ce S.A.