Facile Substitution of Bridging SO₂^2– Ligands in Re₁₂ Bioctahedral Cluster Complexes

Abstract

Selective substitution of μ-SO groups by either O or Se ions occurs upon heating the bioctahedral rhenium cluster complex K[ReCS(μ-SO)(CN)] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [ReCS(μ-O)(CN)], [ReCS(μ-Se)(CN)], and [ReCS(μ-O)(OH)], were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported μ-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [ReCS(μ-Q)L] (Q = O, S, Se, L = CN; Q = O, S, L = OH), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the substitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.

Selective Oxidation of Inner Pnictogenide Ligands in Mixed-Ligand Rhenium Cubane-Type Cluster Complexes

“…Similar to [{Re 4 (AsO) 3 S}­(CN) 12 ] 7– , the metal cluster “expands” from the average Re–Re distance of 2.78(1) Å in the unoxidized cluster to 2.89(3) Å in the oxidized one. The Re–As and Re–Se bond lengths are in the ranges of 2.4313(16)–2.4716(16) and 2.4747(13)–2.4939(14) Å, respectively, and are in good agreement with the data for the complexes [{Re 4 Se 4 }­(CN) 12 ] 4– ,,, and [{Re 4 (AsO) 4 }­(CN) 12 ]. − …”

“…The Re–Te bonds [2.6424(6)–2.6504(6) Å] practically do not change upon the oxidation of the compound with the {Re 4 (AsO) 2.25 As 0.75 Te} 5+ core, where these distances are in the range from 2.6464(5) to 2.6534(5) Å. The Re–As and As–O bond lengths are 2.4286(9)–2.4529(9) and 1.655(6)–1.669(6) Å, respectively, and are in good agreement with the values observed in both [{Re 4 (AsO) 3 Q}­(CN) 12 ] 7– (Q = S, Se) and [{Re 4 (AsO) 4 }­(CN) 12 ]. − The bond lengths for complexes 1–3 are summarized in Table . One can see that the cluster core slightly expands in the row of Q = S–Se–Te, which is associated with an increase in the ionic radius of the chalcogen.…”

“…However, the inner ligands affect the electronic structure and physical properties of cluster compounds to a much greater extent than the apical ligands. As typical examples of such an influence, chalcogenide and halide clusters of molybdenum and tungsten with the {M 6 Q 8 } (Q = S, Se) or {M 6 X 8 } (X = Cl, Br, I) cluster cores, chalcohalide rhenium clusters with {Re 6 Q 8– n X n } cores, and 12-nuclear clusters with {Re 12 CS 14 (Q/X) 3 } cores should be mentioned. These compounds exhibit very different optical, chemical, and electrochemical properties, depending on the composition of the inner ligand environment.…”

Transition Metal Carbide Complexes

“…The SO 2 2– ligands are relatively labile and peripheral modifications are possible with retention of the central carbide moiety. Thus, reaction with KSeCN results in selenide-bridged K 6 [Re 12 (μ 6 -C)­(μ-Se) 3 (μ 3 -S) 14 (CN) 6 ], while reaction with O 2 and KOH results in substitution of both the cyanide and SO 2 2– ligands, yielding the oxide-hydroxide complex, K 6 [Re 12 (μ 6 -C)­(μ-O) 3 (μ 3 -S) 14 (OH) 6 ] . Reaction of the oxide-hydroxide complex with HCl or HBr proceeds with two-electron reduction of the cluster, affording (Et 4 N) 5 [Re 12 (μ 6 -C)­(μ-Cl) 3 (μ 3 -S) 14 Cl 6 ] or (Et 4 N) 5 [Re 12 (μ 6 -C)­(μ-Br) 3 (μ 3 -S) 14 Br 6 ] …”

“…Thus, reaction with KSeCN results in selenide-bridged K 6 [Re 12 (μ 6 -C)(μ-Se) 3 (μ 3 -S) 14 (CN) 6 ], while reaction with O 2 and KOH results in substitution of both the cyanide and SO 2 2− ligands, yielding the oxide-hydroxide complex, K 6 [Re 12 (μ 6 -C)(μ-O) 3 (μ 3 -S) 14 (OH) 6 ]. 202 Reaction of the oxide-hydroxide complex with HCl or HBr proceeds with two-electron reduction of the cluster, affording 203 Triple bond metathesis between the homoleptic {WW} complex, [( t BuO) 3 WW(O t Bu) 3 ], and alkynes or acetylides readily leads to carbyne or carbide complexes (Figure 36). By contrast, Wolczanski found that the heteroleptic {WW} complex, [( t Bu 3 SiO) 2 ClWWCl(OSi t Bu 3 ) 2 ] reacts with CO and CNAr (Ar = 2,6-Me 2 C 6 H 3 ) to form the 1:2 and 1:…”