Carbonyl, hydridocarbonyl, and hydridoalkoxycarbonyl complexes of iridium with phosphorus–sulphur hybrid ligands, and the crystal and molecular structure of [IrH(CO2Me)(Ph2PCH2CH2SEt)2]BPh4

Abstract

Treatment of trans-[IrCl(CO)(PPh₃)₂] with two equivalents of Ph₂P–CH₂–CH₂–SR (R = Me, P–SMe; R = Et, P–SEt) in dichloromethane–methanol affords yellow [Ir(CO)(P–SR)₂]⁺ complexes, which are isolated as [BPh₄]^– salts. These monocarbonyl complexes react with CO in dichloromethane solution yielding the corresponding dicarbonyl derivatives, identified by i.r. and ³¹P n.m.r. spectroscopy. Alternatively, treatment of trans-[IrCl(CO)(PPh₃)₂] with two equivalents of P–SR in dichloromethane–methanol at 70 °C for several hours affords white [IrH(CO₂Me)(P–SR)₂]⁺ complexes, isolated as [BPh₄]^– salts in good yield. These compounds can also be conveniently obtained by nucleophilic attack of an alcohol molecule on CO of the corresponding dicationic hydrido–carbonyl complexes of Ir^III. The [Ir(CO)(P–SEt)₂]⁺ cation reacts with HY (Y = Cl or BF₄) to afford cis- or trans-[IrH(CO)(P–SEt)₂]²⁺ derivatives according to the nature of Y; the reactivities and stabilities of these species are discussed. The new compounds have been characterized on the basis of i.r., ³¹P n.m.r., ¹H n.m.r., and conductivity data. A single-crystal X-ray diffractometric study of [IrH(CO₂Me)(P–SEt)₂] BPh₄ revealed the octahedral geometry of the complex cation, with trans-P atoms and cis-S atoms; the bonding of the methoxycarbonyl group is also discussed. Crystal data: orthorhombic system (space group P2₁2₁2₁), a= 12.242(2), b= 16.616(3), c= 26.992(2)Å, Z= 4; the structure was refined to R= 0.0515, R′= 0.0603.