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

The novel tris(mercaptoimidazolyl)borate ligands Li[RB(timMe)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(timMe)3-(kappa)^3S,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.