Ionic-liquid-based synthesis of tellurium-rhenium carbonyls with specific reaction control.

The novel tellurium rhenium carbonyls [TeI2Re(CO)5][AlCl4] (1), [BMIm][Te2I4(μ-I)2Re(CO)4] (2), {Te3I2(μ-I)3(μ3-I)}Re(CO)3 (3) and [BMIm][(Te2)3{Re(CO)3}2{Re(CO)4}3] (4) were prepared by reacting TeI4 and Re2(CO)10 in ionic liquids (ILs). [TeI2Re(CO)5][AlCl4] (1) was obtained in a mixture of [BMIm]Cl (BMIm: 1-butyl-3-methylimidazolium) and AlCl3 (ratio: 1 : 1) and contains a [TeI2Re(CO)5]+ cation. Increasing the amount of AlCl3 ([BMIm]Cl : AlCl3 = 1 : 2) results in [BMIm][Te2I4(μ-I)2Re(CO)4] (2) with the anion [Te2I4(μ-I)2Re(CO)4]-. At a [BMIm]Cl to AlCl3 ratio of 1 : 3, {Te3I2(μ-I)3(μ3-I)}Re(CO)3 (3) was realized with a Te3I3 ring and μ3-coordinating iodine. Finally, [BMIm][(Te2)3{Re(CO)3}2{Re(CO)4}3] (4) was prepared in [BMIm][OTf] (OTf: triflate) and contains the ufosan-like anion [(Te2)3{Re(CO)3}2{Re(CO)4}3]- with three Te22- and two Re(CO)3+ units that establish a distorted heterocuban-like cage. The compounds were characterized by single-crystal structure analysis, energy dispersive X-ray (EDX) analysis, thermogravimetry (TG), and infrared spectroscopy (FT-IR). The course of the reaction and the formation of the four novel tellurium-rhenium carbonyls can be directly correlated to the reaction conditions and especially to the acidity of the IL.