Reactivity of the Dimer [{RuCl(μ-Cl)(η³:η³‑C₁₀H₁₆)}₂] (C₁₀H₁₆ = 2,7-Dimethylocta-2,6-diene-1,8-diyl) toward Guanidines: Access to Ruthenium(IV) and Ruthenium(II) Guanidinate Complexes

The novel bis­(allyl)­ruthenium­(IV) guanidinate complexes [RuCl­{κ2(N,N′)-C­(NR)­(NiPr)-NHiPr}­(η3:η3-C10H16)] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl; R = Ph (3a), 4-C6H4F (3b), 4-C6H4Cl (3c), 4-C6H4Me (3d), 3-C6H4Me (3e) 4-C6H4tBu (3f)) have been synthesized by treatment of the dimeric precursor [{RuCl­(μ-Cl)­(η3:η3-C10H16)}2] (1) with 4 equiv of the corresponding guanidine (iPrHN)2CNR (2a–f). The easily separable guanidinium chloride salts [(iPrHN)2C­(NHR)]­[Cl] (4a–f) are also formed in these reactions. Attempts to generate analogous Ru­(IV) guanidinate complexes from (iPrHN)2CNR (R = 2-C6H4Me (2g), 2,4,6-C6H2Me3 (2h), 2,6-C6H3iPr2 (2i)) failed, due probably to the steric hindrance associated with the aryl group in these guanidines. On the other hand, the reaction of the dimer [{RuCl­(μ-Cl)­(η3:η3-C10H16)}2] (1) with (iPrHN)2CN-4-C6H4CN (2j) led to the selective formation of the mononuclear derivative [RuCl2(η3:η3-C10H16)­{NC-4-C6H4-NC­(NHiPr2)2}] (5), in which the guanidine coordinates to ruthenium through the pendant nitrile unit. This result contrasts with that obtained by employing the related Ru­(II) dimer [{RuCl­(μ-Cl)­(η6-p-cymene)}2] (6), whose reaction with 2j afforded the expected guanidinate complex [RuCl­{κ2(N,N′)-C­(N-4-C6H4CN)­(NiPr)-NHiPr}­(η6-p-cymene)] (7). Treatment of 7 with dimer 1 yielded the dinuclear Ru­(II)/Ru­(IV) derivative 8, via cleavage of the chloride bridges of 1 by the CN group of 7. Reductive elimination of the 2,7-dimethylocta-2,6-diene-1,8-diyl chain in [RuCl­{κ2(N,N′)-C­(NR)­(NiPr)-NHiPr}­(η3:η3-C10H16)] (3a–f) readily took place in the presence of an excess of 2,6-dimethylphenyl isocyanide, thus allowing the high-yield preparation of the octahedral ruthenium­(II) compounds mer-[RuCl­{κ2(N,N′)-C­(NR)­(NiPr)-NHiPr}­(CN-2,6-C6H3Me2)3] (9a–f). The structures of [RuCl­{κ2(N,N′)-C­(N-4-C6H4Me)­(NiPr)-NHiPr}­(η3:η3-C10H16)] (3d), [RuCl­{κ2(N,N′)-C­(N-4-C6H4CN)­(NiPr)-NHiPr}­(η6-p-cymene)] (7), and mer-[RuCl­{κ2(N,N′)-C­(N-4-C6H4tBu)­(NiPr)-NHiPr}­(CN-2,6-C6H3Me2)3] (9f), as well as those of the guanidinium chloride salts 4a–c, were unequivocally confirmed by X-ray diffraction methods. In addition, the catalytic behavior of the guanidinate complexes 3a–f and 9a–f in the redox isomerization of allylic alcohols was also explored.新型双(烯丙基)钌(IV)胍基配合物[RuCl{κ²(N,N′)-C(NR)(NiPr)-NHiPr}(η³:η³-C₁₀H₁₆)]（其中C₁₀H₁₆代表2,7-二甲基辛-2,6-二烯-1,8-二基；R=Ph(3a)、4-C₆H₄F(3b)、4-C₆H₄Cl(3c)、4-C₆H₄Me(3d)、3-C₆H₄Me(3e)、4-C₆H₄tBu(3f)），可通过二聚体前驱体[{RuCl(μ-Cl)(η³:η³-C₁₀H₁₆)}₂](1)与4当量的相应胍(iPrHN)₂C=NR(2a–f)反应合成得到。该反应同时生成易于分离的胍氯化物盐[(iPrHN)₂C(NHR)][Cl](4a–f)。 尝试以(iPrHN)₂C=NR（R=2-C₆H₄Me(2g)、2,4,6-C₆H₂Me₃(2h)、2,6-C₆H₃iPr₂(2i)）合成类似的钌(IV)胍基配合物的尝试均告失败，这可能归因于这些胍分子中芳基所带来的空间位阻。另一方面，二聚体[{RuCl(μ-Cl)(η³:η³-C₁₀H₁₆)}₂](1)与(iPrHN)₂C=N-4-C₆H₄C≡N(2j)的反应选择性生成单核衍生物[RuCl₂(η³:η³-C₁₀H₁₆){N≡C-4-C₆H₄-N=C(NHiPr₂)₂}](5)，其中胍通过悬垂的腈单元与钌配位。 这一结果与使用相关二聚体[{RuCl(μ-Cl)(η⁶-对伞花烃)}₂](6)的反应形成鲜明对比：后者与2j反应得到预期的胍基配合物[RuCl{κ²(N,N′)-C(N-4-C₆H₄C≡N)(NiPr)-NHiPr}(η⁶-p-cymene)](7)。将7与二聚体1反应，可通过7的C≡N基团断裂1的氯桥键，得到双核Ru(II)/Ru(IV)衍生物8。 在过量2,6-二甲基苯基异氰酸酯存在的条件下，配合物3a–f中的2,7-二甲基辛-2,6-二烯-1,8-二基链可轻易发生还原消除反应，从而以高产率制备得到八面体构型的钌(II)化合物mer-[RuCl{κ²(N,N′)-C(NR)(NiPr)-NHiPr}(CN-2,6-C₆H₃Me₂)₃](9a–f)。 通过X射线衍射分析法，明确确认了配合物[RuCl{κ²(N,N′)-C(N-4-C₆H₄Me)(NiPr)-NHiPr}(η³:η³-C₁₀H₁₆)](3d)、[RuCl{κ²(N,N′)-C(N-4-C₆H₄C≡N)(NiPr)-NHiPr}(η⁶-p-cymene)](7)、mer-[RuCl{κ²(N,N′)-C(N-4-C₆H₄tBu)(NiPr)-NHiPr}(CN-2,6-C₆H₃Me₂)₃](9f)以及胍氯化物盐4a–c的晶体结构。此外，本研究还考察了胍基配合物3a–f与9a–f在烯丙醇氧化还原异构化反应中的催化行为。