Crystal structures of mercury(II) chloride and bromide addition complexes of carbonylchlorobis(triphenylphosphine)iridium(I)

Abstract

The crystal structures of the oxidative-addition products of trans-[IrCl(CO)(PPh₃)₂] with HgCl₂ and HgBr₂ have been determined by X-ray diffraction. The structure of [IrCl₂(HgCl)(CO)(PPh₃)₂] was refined by least squares to R 0.059 (3 430 observed reflections). Crystals are monoclinic, space group P2₁/n, a= 15.805(2), b= 21.734(3), c= 10.537(1)Å, β= 92.13(2)°, Z= 4. The two chlorines bonded to the pseudo-octahedral iridium are mutually cis[Ir-Cl, 2.453(5), 2.401 (4)Å]. while the two PPh₃ ligands are trans[Ir–;P, 2.387(4), 2.378(4)Å], with the HgCl group trans to the Ir–Cl bond [Ir–Hg, 2.570(1)Å]. The mercury atom lies close to a centre of symmetry and Ir–Hg–Cl is slightly perturbed from linearity by interaction of Hg with the chlorine of its inversion image [Hg–Cl, 2.366(5), Hg ⋯ Cl′, 3.148(5)Å; Ir–Hg–Cl, 172.2(1)°]. The structure of the isomorphous [IrBrCl(HgBr)(CO)(PPh₃)₂][a= 16.021(7), b= 21.788(6), c= 10.568(4)Å, β= 93.11(3)°] indicates that the oxidative-addition reaction is predominantly trans in this instance: the partial bromine occupancy of the equatorial chlorine site is ca. 0.15; R was 0.072 for 3 810 observed reflections.