A flexible framework obtained from oxidative additions upon the binuclear complex [Ir2(µ-pz)(µ-SBut)(CO)2{P(OMe)3}2]: preparation and X-ray structures of [Ir2(µ-pz)(µ-SBut)(µ-L)(CO)2{P(OMe)3}2] and [Ir2(µ-pz)(µ-SBut)(µ-L)I2(CO)2-{P(OMe)3}2](Hpz = pyrazole, L = dimethyl acetylenedicarboxylate)

Abstract

The formation and properties of the heterobridged complexes [Ir₂(µ-pz)(µ-SBu^t)(cod)₂](1)(cod = cyclo-octa-1,5-diene, pz = pyrazolate) and [Ir₂(µ-pz)(µ-SBu^t)(CO)₂{P(OMe)₃}₂](2) are reported. Compound (2) undergoes stepwise addition of molecular iodine to yield the complexes [Ir₂(µ-pz)(µ-SBu^t)I_n;(CO)₂{P(OMe)₃}₂][n= 2 (3) and 4 (4)]. Interaction of complex (2) with dimethyl acetylenedicarboxylate affords the triply heterobridged complex [Ir₂(µ-pz)(µ-SBu^t)(µ-MeO₂CCCCO₂Me)(CO)₂{P(OMe)₃}₂](5). Compound (5) undergoes a further oxidative addition with I₂ to form [Ir₂(µ-pz)(µ-SBu^t)(µ-MeO₂CCCCO₂Me)I₂(CO)₂{P(OMe)₃}₂](6). Compound (6) can be also obtained using mercury(II) iodide as oxidant, and similarly, [Ir₂(µ-pz)(µ-SBu^t)(µ-MeO₂CCCCO₂Me)Cl₂(CO)₂{P(OMe)₃}₂](7) using mercury(II) chloride. The structures of (5) and (6) have been determined by X-ray diffraction methods. Crystals of (5) are monoclinic, space group P2₁/n, with a= 18.040(7), b= 15.986(6), c= 11.085(4)Å, β= 92.68(2)°, and Z= 4. Complex (6) is orthorhombic, space group P2₁2₁2₁ with a= 13.522(5), b= 20.871 (8), c= 12.649(7)Å, with Z= 4. Both complexes are binuclear with the metal atoms held in proximity by a triple bridge: a pyrazolate anion, a Bu^tS group and a dimethyl acetylenedicarboxylate ligand bonded as a cis-dimetallated olefin. The oxidative addition of I₂ to (5) originates a remarkable change in the Ir–Ir distance from 2.614(2) to 3.626(2)Å, leaving practically unaltered the bridging framework.