Thermal and photochemical substitution reactions of CpRe(PPh 3) 2H 2 and CpRe(PPh 3)H 4. Catalytic insertion of ethylene into the C-H bond of benzene

Abstract

The thermal and photochemical reactions of CpRe(PPh 3) 2H 4 and CpRe(PPh 3)H 4 (Cp = η 5-C 5H 5) with PMe 3, P( p-tolyl) 3, PMe 2Ph, DMPE, DPPE, DPPM, CO, 2,6-xylylisocyanide and ethylene have been examined. While CpRe(PPh 3) 2H 2 is thermally inert, it will undergo photochemical substitution of one or two PPh 3 ligands. With ethylene, substitution is followed by insertion of the olefin into the C-H bond of benzene, giving ethylbenzene. CpRe(PPh 3)H 4 undergoes thermal loss of PPh 3, which leads to substituted products of the type CpRe(L) H 4. Photochemically, reductive elimination of dihydrogen occurs preferentially. The complex 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) Å, β = 92.11(6)°, V = 1443.7(2.9) Å and Z = 4. The complex trans-CpRe(PMe 2Ph) 2H 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) Å, β = 100.16(4)°, V = 2070.2(3.4) Å 3 and Z = 4.