Reactions of the Re(CO)₃(H₂O)₃ ⁺ Synthon with Monodentate Ligands under Aqueous Conditions

Abstract

The reactions of ammonia, pyridine (py), N-methyl imidazole (N-MeIm), tetrahydrothiophene (tht), and piperidine (pip) with Re(CO) 3(H 2O) 3 (+), 1 ( + ), were investigated employing aqueous conditions under atmospheric dioxygen. The reaction of [ 1]Br in aqueous ammonia led to [Re(CO) 3(NH 3) 3]Br ([ 2]Br) as the only product isolated. For the aqueous reactions of [ 1]Br with py, N-MeIm, and tht, mixtures of products are formed because of competition between the bromide and added ligand, even when the ligand is present in excess. Substitution of the PF 6 (-) anion for Br (-) leads to the clean formation of [Re(CO) 3L 3][PF 6] ([ 3][PF 6]-[ 5][PF 6]) for py, N-MeIm, and tht, respectively, as the only products observed. Reaction of [ 1][PF 6] with pip produces the dimeric species, (pip)(CO) 3Re(micro-OH) 2Re(CO) 3(pip), 6. Reactions of [ 1]Br were also performed in methanol for comparison purposes. The reaction with pip in this solvent led to the analogous dimer, (pip)(CO) 3Re(micro-OMe) 2Re(CO) 3(pip), 7; however, reactions with py, N-MeIm, and tht gave Re(CO) 3L 2Br, 8- 10, respectively, as the only products. The crystal structures of compounds [ 2]Br- 10 are reported.

Preparation and characterization of rhenium (I) tricarbonyl dithiocarbamate compounds; Re(CO)3(S2CNMe2)(L)

“…The dithiocarbamate ligand has an average bite angle of 70.4(4)°, similar to the range of 69-71°measured for other rhenium (I) dithiocarbamates [10][11][12]. The Re-N distance of 2.228(5) Å measured for 1 is comparable to the average value of 2.23(1) Å recorded for [Re(CO) 3 (NH 3 ) 3 ]Br and Re(CO) 3 (NH 3 ) 2 Br [22,29]. The average Re-N distance for 2 and 3 is 2.223(5) Å, comparable to the average value of 2.21(2) Å for the series of [Re-(CO) 3 L 3 ][PF 6 ] and Re(CO) 3 L 2 Br with N-heterocyclic base ligands [22].…”

“…The Re-N distance of 2.228(5) Å measured for 1 is comparable to the average value of 2.23(1) Å recorded for [Re(CO) 3 (NH 3 ) 3 ]Br and Re(CO) 3 (NH 3 ) 2 Br [22,29]. The average Re-N distance for 2 and 3 is 2.223(5) Å, comparable to the average value of 2.21(2) Å for the series of [Re-(CO) 3 L 3 ][PF 6 ] and Re(CO) 3 L 2 Br with N-heterocyclic base ligands [22]. The Re-N value of 2.173(10) Å measured for 4 is at the low end of the range of values, 2.17-2.20 Å, observed for comparable pyrazole complexes [30][31][32][33][34].…”

“…It made no difference in outcome whether Re(CO) 5 3 ]Á6H 2 O [28]) was used as the reagent. Previously, we found that Re(CO) 3 L 3 + (L = NH 3 , tetrahydrothiophene, N-methylimidazole and pyridine) compounds could be readily prepared in water [22]. In this study, immediate precipitation, presumably of neutral Re(CO) 3 (dmtc)(H 2 O), occurred when reactions were attempted in water; this compound was never isolated, and the use of water as a solvent was abandoned.…”

“…One reason for this focus is that there remain common ligands that have not been extensively applied to the group 7 d 6 systems. We have presented reports on monodentate [22], bidentate [23,24], and tridentate [25,26] ligand systems over the past several years. In this paper we continue this series, looking at simple complexes of the dithiocarbamate ligand prepared in a straightforward manner.…”

Post-Protein-Binding Reactivity and Modifications of the fac-[Re(CO)3]+ Core

“…On the other hand, reactions of the solvated metal ion 1 with im gave a mixture of products (i.e., mono-, bis-, and tris-substituted complexes), and those with py gave the well-defined fac-[Re(CO) 3 (py) 2 (OH 2 )] + complex. 27 The fundamental reasons underlying these differences were not clear at this point. We speculated that hydrogen-bonding interactions between the incoming ligands and the amino acid residues in close proximity to the Re binding site may play an important role in determining the reactivity of the metal ion.…”