Rhenium(i) tris(carbonyl) complexes with soft scorpionates

Abstract

The novel tris(mercaptoimidazolyl)borate ligands Li[RB(tim^Me)₃] (R = Me (1), Ph (2)) have been synthesized by reaction, in refluxing toluene, of 2-mercapto-1-methylimidazole with lithium methylborohydride or phenylborohydride, respectively. By reacting 1 and 2 with the Re(I) starting material (NEt₄)₂[Re(CO)₃Br₃], the tris(carbonyl) complexes [Re{RB(tim^Me)₃-κ³S,S,S}(CO)₃] (R = Me (3), Ph (4)) have been obtained in moderate yields. Compounds 1–4 have been characterized by IR, ¹H, and ¹¹B NMR spectroscopies, and also by X-ray crystallographic analysis in the case of 3. The X-ray diffraction analysis of 3 showed that the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. The three remaining coordination positions are occupied by the thione sulfur atoms from the tripodal methyltris(2-mercapto-1-methylimidazolyl)borate, which adopts a typical propeller-like configuration.