Synthesis of tricarbonyl derivatives of rhenium(I) with Group 16 donor atoms. Crystal and molecular structure of di-mu-bromo-mu-1,8-naphthalenedisulfide-bis(fac-tricarbonylrhenium(I))

Abstract

The tetrahydrofuran adduct Re2Br2(CO)(6)(THF)(2) reacts with 1,8-naphthalenedisulfide (NDS) to give Re2Br2(CO)(6)(NDS), which crystallizes in the monoclinic system, space group P2(1)/c, with cell constants a=10.071(4), b=21.229(5), c=10.135(7) Angstrom; beta=105.73(5)degrees, and Z=4 molecules per unit cell. The final R value is 0.044 for 2035 data (Mo-K-alpha). The Re2Br2(CO)(6) fragment is the same as in all previously determined structures of this series, having bridging bromides and a fac tricarbonyl arrangement about each rhenium atom. The rhenium atoms are also bridged by the disulfide fragment of NDS forming two five-membered rings of composition Re-S-S-Re-Br. The fold angle across the Br ... Br vector is 29 degrees. The Re-Br distances are unequal, with the shorter distances to the bromine closer to the naphthalene fragment; this bromine is further from the S-S bridge than the other. The Re-S and S-C distances average 2.48 and 1.78 Angstrom, respectively, while the S-S bond is 2.16 Angstrom long. Both the Re-S-S-Re and C-S-S-C torsion angles are nearly 0 degrees, which is a significant distinction from the previously investigated structures of this type. The NDS ligand is significantly non-planar, and this may be due to steric repulsion from the nearby carbonyl groups. The dibenzyldisulfide and dibenzyldiselenide complexes Re-2(mu-I)(2)(CO)(6)(E(2)Bz(2)), E=S, Se, have been prepared starting from the same THF rhenium(I) precursor. The Se NMR data of the dibenzyldiselenide complex show a downfield shift of about 165 ppm with respect to the uncomplexed molecule under the same conditions. Bis(dimethylphosphine)ethane gives ReI(CO)(3)(Me(2)PCH(2)CH(2)PMe(2)); iodide abstraction from the latter by silver triflate gave Re(SO3CF3)(CO)(3)(Me(2)PCH(2)CH(2)PMe(2)), which is suggested to contain the monodentate triflato ligand