摘要:
Platinum complexes of dibenzannelated didehydrotropone 5, didehydrooxepin 6, and didehydrocycloheptatriene 7 have been synthesized in good yields by base-induced dehydrobromination from the corresponding bromoalkenes in the presence of Pt(PPh(3))(3). Complex 5 crystallizes in triclinic space group P1: a 11.221(2) Angstrom, b 11.318(2) Angstrom, c 16.621(4) Angstrom, alpha = 74.22(2)degrees, beta = 78.86(2)degrees, gamma = 73.56(2)degrees, V= 2445.0(9) Angstrom(3), Z = 2, R = 5.79%. Reaction of 5 with tert-butyl isocyanide gives a single phosphine displacement product 11, and reaction with HBF4 and HBr gives oxidative addition products 8 and 12, respectively. Bis(dicyclohexylphospkino)ethane displaces triphenylphosphine from 5 and 6 to give 9 and 10, Complex 5 reacts with tetracyanoethylene to give the highly distorted substituted benzene 14 which was characterized by X-ray diffraction. Crystal data for 14: Space group P1, a = 11.274(2) Angstrom, b = 11.826(1) Angstrom, c = 13.474(2) Angstrom, alpha 111.79(1)degrees, beta 106.34(1)degrees, gamma = 98.54(1)degrees, V = 1534.9(4) Angstrom(3), Z = 2, R 6.17%. Complex 6 reacts with TCNE, to give the platinacyclopent-2-ene 15 (55%). Complex 15 crystallizes in monoclinic space group la: a = 17.175(3) Angstrom, b = 15.411(2) Angstrom, c = 18.661(2) Angstrom, beta = 91.86(1)degrees, V= 4915(2) Angstrom(3), R = 4.74%. Reaction of 7 with triphenylcarbenium tetrafluoroborate gives the dibenzannelated tropyne complex 16 which can be converted back to 7 with KBEt(3)H. Reaction of 16 with bis(dicyclohexylphosphino)ethane gives 17 (60%), and reaction with HBr gives the oxidative addition product 18 which slowly isomerizes to 19.