Photochemical reactions of [CH<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)<sub>2</sub>][Rh(C<sub>2</sub>H<sub>4</sub>)<sub>2</sub>]<sub>2</sub>with silanes: evidence for Si–C and C–H activation pathways
作者:Jenny L. Cunningham、Simon B. Duckett
DOI:10.1039/b417171c
日期:——
Photochemical reaction of [CH2(η5-C5H4)2][Rh(C2H4)2]21 with dmso led to the stepwise formation of [CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)]
2a and [CH2(η5-C5H4)2][Rh(C2H4)(dmso)]22b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(η5-C5H4)2][Rh(CH2CHSiMe3)2]2, 3a,3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d6-benzene, H/D exchange between the solvent and the α-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(η2-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et3SiH yielded the sequential substitution products [CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiEt3)H]
4a, [CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H]24b, [CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2]
4c and [CH2(η5-C5H4)2][Rh(SiEt3)2(H)2]24d; deuteration of the α-ring proton sites, and all the silyl protons, of 4d was demonstrated in d6-benzene. This reaction is further complicated by the formation of two SiâC bond activation products, [CH2(η5-C5H4)2][RhH(μ-SiEt2)]25 and [CH2(η5-C5H4)2][(RhEt)(RhH)(μ-SiEt2)2]
6. Complex 5 was also produced when 1 was photolysed with Et2SiH2. When the photochemical reactions with Et3SiH were repeated at low temperatures, two isomers of the unstable CâH activation products, the vinyl hydrides [CH2(η5-C5H4)2][Rh(SiEt3)H}Rh(SiEt3)}(μ-η1,η2-CHCH2)]
7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(η5-C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]28 while 4b formed [CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2
(9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me3SiH yielded the expected products [CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H]
10a, [CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H]210b, [CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2]
10c and [CH2(η5-C5H4)2][Rh(SiMe3)2(H)2]210d. However, three SiâC bond activation products, [CH2(η5-C5H4)2][(RhMe)(RhH)(μ-SiMe2)2]
11, [CH2(η5-C5H4)2][(RhSiMe3})(RhMe)(μ-SiMe2)2]
12 and [CH2(η5-C5H4)2][(RhSiMe3})(RhH)(μ-SiMe2)2]
13 were also obtained in these reactions.
[CH2(η5-C5H4)2][Rh(C2H4)2]21与dmso的光化学反应导致[CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)]2a和[CH2(η5-C5H4)2][Rh(C2H4)(dmso)]22b的逐步形成。1与乙烯基三甲基硅烷的光解反应最终产生[CH2(η5-C5H4)2][Rh(CH2CHSiMe3)2]2的三种异构体产物3a、3b和3c,它们通过乙烯基硅烷的相对取向区分。当此反应在d6-苯中进行时,揭示了溶剂与乙烯基硅烷的α-氢之间的H/D交换。此外,在这些及相关实验中,当光解在低温下完成且无底物时,获得了溶剂络合物[CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(η2-甲苯)]两种异构体的证据,尽管未观察到H/D交换的证据。1与Et3SiH的光解反应产生顺序取代产物[CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiEt3)H]4a、[CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H]24b、[CH2(η5-C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2]4c和[CH2(η5-C5H4)2][Rh(SiEt3)2(H)2]24d;在d6-苯中证明了4d的α-环质子位点和所有硅基质子的氘化作用。该反应进一步复杂化,形成两种Si-C键活化产物,[CH2(η5-C5H4)2][RhH(μ-SiEt2)]25和[CH2(η5-C5H4)2][(RhEt)(RhH)(μ-SiEt2)2]6。当1与Et2SiH2光解时也生成了5。当在低温下重复Et3SiH的光化学反应时,获得了不稳定的C-H活化产物、乙烯基氢化物[CH2(η5-C5H4)2][Rh(SiEt3)H}Rh(SiEt3)}(μ-η1,η2-CHCH2)]7a和7b的两种异构体。热力学上,4c被证明形成环取代的硅基迁移产物[(η5-C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]28,而4b与过量硅烷反应形成[CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2(9a和9b)。对应的光化学反应与Me3SiH产生预期的产物[CH2(η5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H]10a、[CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H]210b、[CH2(η5-C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2]10c和[CH2(η5-C5H4)2][Rh(SiMe3)2(H)2]210d。然而,这些反应中还获得了三种Si-C键活化产物,[CH2(η5-C5H4)2][(RhMe)(RhH)(μ-SiMe2)2]11、[CH2(η5-C5H4)2][(RhSiMe3})(RhMe)(μ-SiMe2)2]12和[CH2(η5-C5H4)2][(RhSiMe3})(RhH)(μ-SiMe2)2]13。