Preparation, molecular structure, and fundamental vibrational modes of the dinuclear complexes trans-[{RhX(PiPr3)2}2{μ-1,3-(CN)2C6H4}]

The reaction of [RhCl(C8H14)2]2 with 4 equiv. of PiPr3 and an equimolar amount of 1,3-C6H4(NC)2 in benzene–ether led to the formation of the dinuclear diisonitrile complex trans-[{RhCl(PiPr3)2}2{μ-1,3-(CN)2C6H4}] (2) in 75% yield. The related iodo compound trans-[{RhI(PiPr3)2}2{μ-1,3-(CN)2C6H4}] (3) was obtained from 2 and NaI by salt metathesis. Density functional theory (DFT) calculations have been carried out for the model complexes trans-[RhX(CNC6H5)(PMe3)2] (X=F, Cl) and trans-[{RhF(PMe3)2}2{μ-1,3-(CN)2C6H4}] in order to assign the vibrational modes of compounds 2 and 3. Moreover, the FT-Raman spectrum of the free ligand m-diisocyanobenzene has been measured and analyzed based on the calculation of the Raman intensities for the normal modes using the BPW91/6-31+G(d) method. The most noteworthy result is that the RhC stretching mode of 2 appears at almost the same wavenumber as that of the vinylidene complex trans-[RhCl(CCHC6H5)(PiPr3)2]. The crystal and molecular structure of 2 has been determined by X-ray crystallography.