Tetrahydrofuran ring opening and unexpected oxidation of the furyl ring in the reaction of bis(2-furyl) ditelluride with iodine and triphenylphosphine

Abstract

The reaction of bis(2-furyl) ditelluride Fu2Te2 (1) with iodine in diethyl ether under ambient conditions expectedly yields FuTeI (2). The in situ reaction of 2 with triphenylphosphine affords Ph3PTe(Fu)I (3), which was characterized in the solid state by single crystal X-ray crystallography. The crystal structure of 3 shows linear P–Te–I backbone and T-shaped coordination around the tellurium atom. In the solid lattice, 3 exists as discrete molecules, which are lined together by a H⋯I hydrogen bonding network. There is no evidence of the secondary bonding Te⋯I or I⋯I interactions, which are typical for many tellurium–iodine compounds. When this two-step reaction of Fu2Te2 with I2 and PPh3 is carried out in tetrahydrofuran, a mixture of products is obtained. The main products, which were identified by single-crystal X-ray crystallography, are {Ph3P(C4H5O2)}2[TeI4] (4), {Ph3P(CH2)4PPh3}[TeI4]·2CH2Cl2 (5·2CH2Cl2), Fu2Te (6), (CH2)4TeI2 (7), Ph3PO, and elemental tellurium. The formation of the products has been discussed in terms of THF ring opening, abstraction of tellurium by PPh3, and the conversion of the furyl ring in FuTeI into a lactone ring due to the presence of atmospheric moisture.