Redox Chemistry of (1,4,7-Tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7- triazacyclononane)ruthenium(III), [Ru^IIIL]:  Synthesis and Characterization of [Ru^II₂(L−L)](BPh₄)₄·10CH₃CN and [LRuRuRuL](PF₆)₂·H₂O

Abstract

The mononuclear blue complex [Ru(III)L] (1) where L represents the trianion of 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane has been synthesized by the reaction of H(3)L.3HPF(6) with [Ru(II)Cl(2)(dmso)(4)] in refluxing CH(3)OH in the presence of air. Chemical or electrochemical oxidation of 1 generates [Ru(II)(2)(L-L)](PF(6))(4) (2), a dinuclear species containing two Ru(II) ions and a neutral tris(disulfide) ligand L-L. The reaction of 1 with 1 equiv of [Ru(II)Cl(2)(dmso)(4)] produces the trinuclear species [LRuRuRuL](PF(6))(2) (3) in low yield. Complexes 2 and 3 have been structurally characterized by X-ray crystallography: [Ru(II)(2)(L-L)](BPh(4))(4).10CH(3)CN, C(194)H(218)B(4)N(16)Ru(2)S(6), crystallizes in the monoclinic space group C2/c with a = 28.734(5) Å, b = 16.347(3) Å, c = 37.986(7) Å, beta = 102.35(2) degrees, and Z = 4 whereas [LRuRuRuL](PF(6))(2).H(2)O, C(78)H(110)F(12)N(6)OP(2)Ru(3)S(6), crystallizes in the monoclinic space group P2(1)/n with a = 18.755(4) Å, b = 22.278(4) Å, c = 21.920(4) Å, beta = 91.69(3) Å, and Z = 4. The electro- and spectroelectrochemistry of 1-3 have been studied in detail as have their electronic structures by (1)H NMR, EPR, UV-vis, IR, and Raman spectroscopy.

Molecular and Electronic Structure of Two Linear Thiophenolate-Bridged Heterotrinuclear Complexes [LFeRuFeL]2+/3+ (L = 1,4,7-Tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane)

“…[5] 4 ] (dmso ϭ dimethyl sulfoxide) in the ratio that the two isoelectronic dications display an S t ϭ 1 ground state in the case of the tri-iron species but an S t ϭ 0 1:1 in methanol, under argon, at elevated temperatures, produced a clear, dark brown solution from which, upon adground state for the triruthenium species. In contrast, both trications have an S t ϭ 1/2 ground state.…”

“…Complex 1 is EPR-silent. Å [5] and in [LFeFeFeL] 2ϩ the Fe···Fe distance is 2.848(1) Å . [3] Figure 4.…”

“…[3,5,6] The staggered configuration of the six tertiary butyl groups (looking down the Fe···Ru···Fe axis) in the achiral stereoisomer ∆(λλλ)···Λ(δδδ) yields a stable structure which has been observed in all cases where the M1···M2 distance is >2.9 Å . Only in enantiomer Λ(δδδ)···Λ(δδδ)] diastereomer been observed.…”

“…[3] If we take these compounds as a reference S(1)ЈϪRu (1)ϪS (2) 95.54 (4) S (1)ϪFe (1)ϪS (2) 89.69(5) S(1)ϪRu(1)ϪS(3) 85.20 (5) N (3)ϪFe (1)ϪS (3) 92.28 (12) series (Table 3) we can determine the iron valences of 1 and S(2)ϪRu (1) 2. In particular, the Mössbauer isomer shift is a sensitive S(1)ϪRu(1)ϪS(3)Ј 94.80 (5) S (1)ϪFe (1)ϪS (3) 90.39 (5) parameter for this purpose because it is a measure of the S(2)ϪRu(1)ϪS(3)Ј 96.88 (5) S (2)ϪFe (1)ϪS (3) 88.44 (5) charge density at the iron nucleus. The apparently linear correlation of oxidation state and isomer shift shown in found for the measurements at liquid helium temperatures, Figure 7B reveals an iron oxidation state of 2.9 for 2 (ഠ we can exclude the possibility of dynamic processes like val-ϩIII) and an intermediate value of 2.5 for the reduced anaence detrapping playing a role.…”

Carbon-sulfur bond formation via alkene addition to an oxidized ruthenium-thiolate.

“…Disulfide radicals are good reducing agents and the odd electron is transferred to the metal. 18 The Ru(II)-disulfide product is silent in the electronic spectrum between 400 nm and 1000…”