Synthesis, Molecular Structure, and Reactivity of Neutral and Cationic Areneosmium(II) Complexes with Diarylcarbenes as Ligands
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- 作者：Birgit Weberndö ; rfer ; Gerhard Henig ; D. C. R. Hockless ; Martin A. Bennett ; and Helmut Werner
- 刊名：Organometallics
- 出版年：2003
- 出版时间：February 17, 2003
- 年：2003
- 卷：22
- 期：4
- 页码：744 - 758
- 全文大小：360K
- 年卷期：v.22,no.4(February 17, 2003)
- ISSN：1520-6041
文摘
While the dinuclear compounds [(
6-mes)Os{
1-OC(O)CF3}(
-Cl)]2 (2) and [(6-mes)Os{1-OS(O)2CF3}(-Cl)]2 (3), prepared from [(6-mes)OsCl(3-C3H5)] (1) and CF3CO2H or CF3SO3Hby elimination of propene, are not suitable precursors for the synthesis of osmium carbenes,the bis(trifluoroacetato) derivatives [(6-arene)Os{1-OC(O)CF3}(2-O2CCF3)] (4, 9, 10) areuseful starting materials. They react with diaryldiazomethanes R2CN2 to give the half-sandwich-type complexes [(6-arene)Os{1-OC(O)CF3}2(=CR2)] (11-17) in good to excellentyields. The bis(tosylato)osmium(II) compounds [(6-arene)Os{1-OS(O)2R}{2-O2S(O)R}] (20,21; R = p-C6H4CH3) behave differently and upon treatment with Ph2CN2 and PhCHN2 affordtetraphenylethene and a mixture of (E)- and (Z)-stilbene. The reaction of 12-15 and 17with either Me3SiX or NH4X (X = Cl, Br, I) leads to the replacement of the trifluoroacetatoligands and the formation of the corresponding carbene complexes [(6-arene)OsX2(=CR2)](22-31) in 67-91% yield. An exchange of trifluoroacetate for chloride or bromide by usingHCl or HBr is also possible. Treatment of [(6-mes)OsCl2(=CPh2)] (28) with M(acac-[Fn]) (M= Na, Tl; n = 0, 3, or 6) affords the chelate compounds [(6-mes)OsCl(2-acac-[Fn])] (33-35)via elimination of the carbene ligand. Compounds 33-35 are also accessible from [(6-mes)OsCl2]2 (19) and Hacac/NEt3 or Na(acac-[Fn]) (n = 3 or 6), respectively. While 14 (arene =mes; R = Ph) and 28 react with C6H5MgBr and CH3MgI only by displacement oftrifluoroacetate or chloride for bromide or iodide, the reaction of 14 with CH2=CHMgBrgives the 3-allyl complex [(6-mes)OsBr(3-CH2CHCPh2)] (36). A C-C coupling also takesplace upon treatment of 14 with CH2=CHOEt, resulting in the formation of the metallacycliccompound [(6-mes)Os{2(C,O)-Ph2CCH=CHOEt}{1-OC(O)CF3}] (38). The bis(trifluoroacetato) derivatives 14, 15, and 17 react in acetone with water to afford the diaryl(carbonyl)osmium(II) complexes [(6-mes)OsR2(CO)] (39-41). On the basis of a labeling experiment,a mechanism for this unusual C-C cleavage reaction is proposed. The reaction of the dichlorocompounds 28 and 29 with PPh3 in the presence of AgPF6 gives the cationic carbenecomplexes [(6-mes)OsCl(PPh3)(=CR2)]PF6 (45, 46) in nearly quantitative yields. Themolecular structures of 2, 15, 28, 35, and 46 were determined crystallographically.
6-mes)Os{1-OC(O)CF3}(-Cl)]2 (2) and [(6-mes)Os{1-OS(O)2CF3}(-Cl)]2 (3), prepared from [(6-mes)OsCl(3-C3H5)] (1) and CF3CO2H or CF3SO3Hby elimination of propene, are not suitable precursors for the synthesis of osmium carbenes,the bis(trifluoroacetato) derivatives [(6-arene)Os{1-OC(O)CF3}(2-O2CCF3)] (4, 9, 10) areuseful starting materials. They react with diaryldiazomethanes R2CN2 to give the half-sandwich-type complexes [(6-arene)Os{1-OC(O)CF3}2(=CR2)] (11-17) in good to excellentyields. The bis(tosylato)osmium(II) compounds [(6-arene)Os{1-OS(O)2R}{2-O2S(O)R}] (20,21; R = p-C6H4CH3) behave differently and upon treatment with Ph2CN2 and PhCHN2 affordtetraphenylethene and a mixture of (E)- and (Z)-stilbene. The reaction of 12-15 and 17with either Me3SiX or NH4X (X = Cl, Br, I) leads to the replacement of the trifluoroacetatoligands and the formation of the corresponding carbene complexes [(6-arene)OsX2(=CR2)](22-31) in 67-91% yield. An exchange of trifluoroacetate for chloride or bromide by usingHCl or HBr is also possible. Treatment of [(6-mes)OsCl2(=CPh2)] (28) with M(acac-[Fn]) (M= Na, Tl; n = 0, 3, or 6) affords the chelate compounds [(6-mes)OsCl(2-acac-[Fn])] (33-35)via elimination of the carbene ligand. Compounds 33-35 are also accessible from [(6-mes)OsCl2]2 (19) and Hacac/NEt3 or Na(acac-[Fn]) (n = 3 or 6), respectively. While 14 (arene =mes; R = Ph) and 28 react with C6H5MgBr and CH3MgI only by displacement oftrifluoroacetate or chloride for bromide or iodide, the reaction of 14 with CH2=CHMgBrgives the 3-allyl complex [(6-mes)OsBr(3-CH2CHCPh2)] (36). A C-C coupling also takesplace upon treatment of 14 with CH2=CHOEt, resulting in the formation of the metallacycliccompound [(6-mes)Os{2(C,O)-Ph2CCH=CHOEt}{1-OC(O)CF3}] (38). The bis(trifluoroacetato) derivatives 14, 15, and 17 react in acetone with water to afford the diaryl(carbonyl)osmium(II) complexes [(6-mes)OsR2(CO)] (39-41). On the basis of a labeling experiment,a mechanism for this unusual C-C cleavage reaction is proposed. The reaction of the dichlorocompounds 28 and 29 with PPh3 in the presence of AgPF6 gives the cationic carbenecomplexes [(6-mes)OsCl(PPh3)(=CR2)]PF6 (45, 46) in nearly quantitative yields. Themolecular structures of 2, 15, 28, 35, and 46 were determined crystallographically.