Crystal structure of the new palladium complexes tetrakis(1,3-dimethylimidazolium-2-ylidene)palladium(II) hexadecacarbonyltetrarhenium diethyl ether disolvate and octa-μ-carbonyl-dicarbonyltetrakis(triphenylphosphane)palladiumdirhenium (unknown solvate)

Abstract

The investigation of the coordination chemistry of heterometallic transition-metal complexes of palladium (Pd) and rhenium (Re) led to the isolation and crystallographic characterization of tetrakis(1,3-dimethylimidazolium-2-ylidene)palladium(II) hexadecacarbonyltetrarhenium diethyl ether disolvate, [Pd(C5H8N2)4][Re4(CO)16]·2C4H10O or [Pd(IMe)4][Re4(CO)16]·2C4H10O, (1), and octa-μ-carbonyl-dicarbonyltetrakis(triphenylphosphane)palladiumdirhenium, [Pd4Re2(C18H15P)4(CO)10] or Pd4Re2(PPh3)4(μ-CO)8(CO)2, (2), from the reaction of Pd(PPh3)4 with 1,3-dimethylimidazolium-2-carboxylate and Re2(CO)10 in a toluene–acetonitrile mixture. In complex 1 the Re—Re bond lengths [2.9767 (3)–3.0133 (2) Å] are close to double the covalent Re radii (1.51 Å). The palladium–rhenium carbonyl cluster 2 has not been structurally characterized previously; the Pd—Re bond lengths [2.7582 (2)–2.7796 (2) Å] are about 0.1 Å shorter than the sum of the covalent Pd and Re radii (1.39 + 1.51 = 2.90 Å). One carbene ligand and a diethyl ether molecule are disordered over two positions with occupancy ratios of 0.5:0.5 and 0.625 (15):0.375 (15) in 1. An unidentified solvent is present in compound 2. The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s). The SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] in PLATON was used to remove the contribution of the electron density in the solvent region from the intensity data and the solvent-free model was employed for the final refinement. The cavity with a volume of ca 311 Å3 contains approximately 98 electrons.