Iridium-assisted C(identical)C bond cleavage of 1-alkyne by water: preparation of new alkyl derivatives

Alkyl complexes IrCl2((eta)1-CH2Ar)(CO)(PPh3)2(1)[Ar = Ph (a), p-tolyl (b)] were prepared by allowing the hydride mer- or fac-IrHCl2 (PPh3)3 to react with terminal alkynes ArC(identical)CH in the presence of water. The complexes were characterized spectroscopically (IR and 1H, 31P, 13C NMR) and by the X-ray crystal structure determination of 1b. The acyl complex IrCl2{C(O)CH2C(CH3)3}(PPh3)2(2) was also prepared by reacting mer-IrHCl2(PPh3)3 with tert-butylacetylene HC(identical)CC(CH3)3 in the presence of H2O. A reaction path for the hydration of terminal alkyne in the presence of the Ir(III) complex leading to the cleavage of the C(identical)C bond, with the formation of the complexes 1 or 2 is also proposed. Acetylide complexes IrHCl(C(identical)CAr)(PPh3)3(3), IrHCl(C(identical)CAr) (AsPh3)3(4)[Ar = Ph (a), p-tolyl (b)] and IrHCl(C(identical)CPh){PPh(OEt)2}(PPh3)2(5) were prepared by reacting IrHCl2L3(L = PPh3, AsPh3) or IrHCl2{PPh(OEt)2}(PPh3)2 with lithium acetylide. Protonation reaction with Bronsted acids of the acetylide 3 was also studied and led to unstable vinyl derivatives. The stable vinyl [IrCl{(eta)2-CH=C(H)COOMe}L2]BPh4(6,7)[L = PPh3(6), AsPh3(7)] complexes, instead, were prepared by allowing IrHCl2L3 to react first with AgCF3SO3 and then with methyl propiolate.