Ligand exchange reactions of [Re2(μ-OR)3(CO)6]− (R = H, Me) with sulfur, selenium, phosphorus and nitrogen donor ligands, investigated by electrospray mass spectrometry †

Abstract

Negative-ion electrospray mass spectrometry has been used to investigate the reactions of the dinuclear rhenium aggregates [Re2(μ-OH)3(CO)6]−1 and [Re2(μ-OMe)3(CO)6]−2 with a range of thiols, benzeneselenol, and some other sulfur-, phosphorus- and nitrogen-based ligands. Typically up to three of the hydroxo ligands are replaced by simple thiolates, giving the series of species [Re2(OH)2(SR)(CO)6]−, [Re2(OH)(SR)2(CO)6]−, and [Re2(SR)3(CO)6]−. Similarly, reaction of 1 with H2S gives the species [Re2(μ-SH)3(CO)6]−, which undergoes an analogous fragmentation process to [Re2(μ-OH)3(CO)6]−, at high cone voltages, by loss of H2S and formation of [Re2(S)(SH)(CO)6]−. With ligands which are good chelating agents (such as dithiocarbamates R2NCS2−, and thiosalicylic acid, HSC6H4CO2H) initial substitution of one or two OH groups readily occurs, but on standing the dimer is cleaved giving [Re(S2CNR2)2(CO)3]− and [Re(SC6H4CO2)(CO)3]−. The different reactivities of the dithiol reagents benzene-1,2- and benzene-1,4-dimethanethiol towards 1 are also described. Complex 1 also reacts with aniline, and with primary (but not secondary) amides RC(O)NH2, giving monosubstituted species [Re2(OH)2(NHPh)(CO)6]− and [Re2(OH)2{NHC(O)R}(CO)6]− respectively. The reactions with adenine and thymine, and with the inorganic anions thiocyanate and thiosulfate, are also described.