Synthesis, Molecular Structure, and Reactivity of Neutral and Cationic Areneosmium(II) Complexes with Diarylcarbenes as Ligands

Autor: Gerhard Henig, Martin A. Bennett, Birgit Weberndörfer, David C. R. Hockless, Helmut Werner
Rok vydání: 2003
Předmět:
Zdroj: Organometallics. 22:744-758
ISSN: 1520-6041
0276-7333
DOI: 10.1021/om0207109
Popis: While the dinuclear compounds [(η 6 -mes)Os{κ 1 -OC(O)CF 3 (μ-Cl)] 2 (2) and [(η 6 -mes)Os{κ 1 -OS(O) 2 CF 3 }(μ-Cl)] 2 (3), prepared from [(η 6 -mes)OsCl(η 3 -C3H5)] (1) and CF 3 CO 2 H or CF 3 SO 3 H by elimination of propene, are not suitable precursors for the synthesis of osmium carbenes, the bis(trifluoroacetato) derivatives [(η 6 -arene)Os{κ 1 -OC(O)CF 3 }(κ 2 -O 2 CCF 3 )] (4, 9, 10) are useful starting materials. They react with diaryldiazomethanes R 2 CN 2 to give the half-sandwich-type complexes [(η 6 -arene)Os{κ 1 -OC(O)CF 3 } 2 (=CR 2 )] (11-17) in good to excellent yields. The bis(tosylatolosmium(II) compounds [η 6 -arene)Os{κ 1 -OS(O) 2 R}{ κ 2 -O 2 S(O)R} (20, 21; R = p-C 6 H 4 CH 3 ) behave differently and upon treatment with Ph 2 CN 2 and PhCHN 2 afford tetraphenylethene and a mixture of (E)- and (Z)-stilbene. The reaction of 12-15 and 17 with either Me 3 SiX or NH4X (X = Cl, Br, I) leads to the replacement of the trifluoroacetato ligands and the formation of the corresponding carbene complexes [(η 6 -arene)OsX 2 (=CR 2 )] (22-31) in 67-91% yield. An exchange of trifluoroacetate for chloride or bromide by using HCl or HBr is also possible. Treatment of [(η 6 -mes)OsCl 2 (=CPh 2 )] (28) with M(acac-[F n ]) (M = Na, Tl; n = 0, 3, or 6) affords the chelate compounds [(η 6 -mes)OsCl(κ 2 -acac-[F n ])] (33-35) via elimination of the carbene ligand. Compounds 33-35 are also accessible from [(η 6 -mes)-OsCl 2 ] 2 (19) and Hacac/NEt 3 or Na(acac-[F n ]) (n = 3 or 6), respectively. While 14 (arene = mes; R = Ph) and 28 react with C 6 H 5 MgBr and CH 3 MgI only by displacement of trifluoroacetate or chloride for bromide or iodide, the reaction of 14 with CH 2 =CHMgBr gives the η 3 -allyl complex [(η 6 -mes)OsBr(η3-CH 2 CHCPh 2 )] (36). A C-C coupling also takes place upon treatment of 14 with CH 2 =CHOEt, resulting in the formation of the metallacyclic compound [(η 6 -mes)Os{κ 2 (C,O)-Ph 2 CCH=CHOEt}{κ 1 -OC(O)CF 3 }] (38). The bis(trifluoroacetato) derivatives 14, 15, and 17 react in acetone with water to afford the diaryl(carbonyl)-osmium(II) complexes [(η 6 -mes)OsR 2 (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 dichloro compounds 28 and 29 with PPh 3 in the presence of AgPF 6 gives the cationic carbene complexes [(η 6 -mes)OsCl(PPh 3 )(=CR 2 )]PF 6 (45, 46) in nearly quantitative yields. The molecular structures of 2, 15, 28, 35, and 46 were determined crystallographically.
Databáze: OpenAIRE
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