155806-23-8Relevant articles and documents
HDS model systems. Coordination, opening, and hydrogenation of benzo[b]thiophene at iridium
Bianchini, Claudio,Meli, Andrea,Peruzzini, Maurizio,Vizza, Francesco,Moneti, Simonetta,Herrera, Verónica,Sánchez-Delgado, Roberto A.
, p. 4370 - 4381 (2007/10/02)
The η4-benzene complexes [(triphos)Ir(C6H6)]Y (Y = BPh4, 1a; PF6, 1b) react with benzo[b]thiophene (BT) at room temperature to give the unprecedented [(triphos)Ir(η3-C,C,S-C8H6S)]Y (Y = BPh4, 2a; PF6, 2b) in which intact BT is coordinated to the metal center through the S atom and the C2=C3 bond. 2a and 2b are transformed upon mild thermolysis into the iridabenzothiabenzene complexes [(triphos)Ir(η2-C,S-C8H6S)]Y (Y = BPh4, 3a; PF6, 3b). An X-ray analysis has been carried out on 3a·1.5THF·0.5EtOH. The coordination geometry around iridium may be described as a distorted trigonal-bipyramid, the metal center being surrounded by the three phosphorus atoms of triphos and by a carbon and a sulfur atom from a C-S-cleaved BT molecule. Crystal data: triclinic, space group P1, a = 17.391(3) A?, b = 16.957(4) A?, c = 12.795(3) A?, α = 77.51(2)°, β= 80.98(2)°, γ = 75.50(2)°, Z = 2, dcalcd = 1.31 g cm-3, nobsd = 7636, R = 0.072. Interaction of 2a with CO (1 atm, 20°C) yields [(triphos)Ir(CO)2]BPh4 (4) plus free BT, whereas 3a requires more drastic conditions (5 atm, 70°C) to eliminate BT and produce 4. 2a also reacts with H2 (1 atm, 20°C) to produce [(triphos)Ir(H)2(η1-S-BT)]BPh4 (5), which can be independently prepared by treatment of [(triphos)Ir(H)2(THF)]BPh4 with BT; at 5 atm H2, free BT is obtained together with [(triphos)Ir(H)3], BPh3, and benzene, as a result of a heterolytic splitting of H2 at the [(triphos)Ir(H)2]+ fragment assisted by the BPh4- counteranion. The C-S-cleaved BT in 3a is readily hydrogenated (5 atm, 20°C) to 2-ethylbenzenethiolate, producing [(triphos)Ir(H)2{o-S-(C6H4)C2H 5}] (8) plus BPh3 and benzene also via heterolytic splitting of H2 assisted by BPh4-; protonolysis of 8 with 2 equiv HCl produces (triphos)IrCl3 with concomitant liberation of 2-ethylbenzenethiol, a primary product of BT HDS. If the PF6- analogue 3b is used instead, the reaction with H2 under identical conditions yields the thiolate-bridged dimer [(triphos)IrH{μ-o-S(C6H4)C2H 5}2HIr(triphos)] (PF6)2 (9b). 3a also reacts with LiHBEt3 to give [(triphos)Ir(H)(η2-C,S-C8H6S)] (11), which converts in THF solution at 66°C into [(triphos)Ir(η3-S(C6H4)-CH=CH2)] (12) by hydride migration to C2; neither 11 nor 12 react with H2 under mild conditions. Addition of HBF4·OEt2 to 12 yields [(triphos)Ir(η4-S(C6H4)C(H)Me)]BF 4 (13c), which does react with H2 even at 1 atm to give the thiolate-bridged dimer [(triphos)IrH{μ-o-S(C6H4)C2H 5}2HIr(triphos)](BF4)2 (9c). 13c also reacts with H- to give [(triphos)IrH(η2-S(C6H4)C(H)Me)] (14), which in turn reacts with H2 and HBF4·OEt2 to yield 8 and 9c, respectively.
