Coordination and oligomerisation of the siloxanephosphane cage compound [P(2){(SiMe(2))(2)O}(3)].
Coordination and oligomerisation of the siloxanephosphane cage compound [P(2){(SiMe(2))(2)O}(3)].
复制标题
硅氧烷膦笼化合物[P(2){(SiMe(2))(2)O}(3)]的配位和低聚。
DOI：
10.1002/chem.200901775
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Sven Stahl
中科院分区：
文献类型：
--
作者：
C. von Hänisch;F. Weigend;O. Hampe;Sven Stahl
Salts of weekly coordinating anions have been applied for several purposes in recent years. For example, ammonium salts of such anions can form ionic liquids, and other compounds of this type have been applied as co-catalysts.[1] In this paper we describe the application of the salt Li [Al-ACHTUNGTRENNUNG (ORF) 4](RF= CACHTUNGTRENNUNG (CF3) 3) as a reagent for a dimerisation of a main-group-element cage compound. This reaction yields a new macrocyclic molecule, which could not be obtained by classical synthetic strategies. Cyclosiloxanes have been known since the mid 1940s, however, the coordination chemistry of these compounds remained widely unexplored until recently.[2] In 2006 the group of Passmore was able to synthesise complexes of the ligands (SiMe2O) 5 and (SiMe2O) 6 (D5 and D6, respectively) systematically by reactions with the lithium salt of the weakly coordinating anion [AlACHTUNGTRENNUNG (ORF) 4] Ā.[3] In the obtained products [Li@ D5][AlACHTUNGTRENNUNG (ORF) 4] and [Li@ D6][AlACHTUNGTRENNUNG (ORF) 4], the lithium ion is located in the middle of the almost planar siloxane rings. In the same year, ring transformations were observed in reactions of the cyclosiloxanes Dn (n= 3–6) with AgSbF6. From these reactions, mixtures of the complex cations [Ag@ D6]+,[Ag@ D7]+ and [Ag@ D8]+ could be obtained.[4] These results showed that cyclosiloxanes can be considered as inorganic analogues of the well-established crown ether ligands. In this respect the cage [P2ACHTUNGTRENNUNG {(SiiPr2) 2O} 2-ACHTUNGTRENNUNG {Me2SiACHTUNGTRENNUNG (OSiMe2) 2}](1) described recently corresponds to a cryptand. This analogy could be confirmed by the synthesis of the lithium complex [Li@ 1]+(see Scheme 1).[5] The large distances between the phosphorus and the lithium atoms within the complex [Li@ 1]+, as well as the fact that only three of the four oxygen atoms coordinate to the lithium ion, led us to question whether a smaller cage with three disiloxane bridges instead of two disiloxane and one trisiloxane bridges could still accomodate a Li+ ion. A cage of this kind with the composition [P2ACHTUNGTRENNUNG {(SiMe2) 2O} 3](2) could be obtained from the reaction of OACHTUNGTRENNUNG (SiMe2Cl) 2 with [Li-ACHTUNGTRENNUNG (dme) PH2] in diethyl ether. Work-up of the reaction mixture yielded compound 2 as colourless crystals that were suitable for crystal structure analysis, as shown in Figure1.[6] To obtain information about the ligand properties of this cage we investigated the reaction of 2 with the lewis acids AlEt3 and GaEt3 as well as the lithium salt Li [AlACHTUNGTRENNUNG (ORF) 4]. The reaction of 2 with two equivalents of AlEt3 yielded the complex [P2ACHTUNGTRENNUNG {(SiMe2) 2O} 3ACHTUNGTRENNUNG (AlEt3) 2](3; Figure2), which could be crystallised from n-pentane as colourless crystals. The crystal structure analysis showed that both phosphorus atoms of cage 2 coordinate to an AlEt3 unit. The structural parameters of the cage only slightly differ from those of compound 2. Thus, the SiĀP bonds are longer in 3 at approximately 2 pm, and the Si-P-Si angles in 3 are on average 38 larger than in 2. The AlĀP bonds are between 253.5 and 256.0 pm long. Analogously, from the reaction of 2 with GaEt3 the compound [P2ACHTUNGTRENNUNG {(SiMe2) 2O} 3ACHTUNGTRENNUNG (GaEt3) 2](4) can be [a] Dr. C. von Hänisch, Dr. F. Weigend, Dr. O. Hampe, S. Stahl Institut für Nanotechnologie, Forschungszentrum Karlsruhe Postfach 3640, 76021 Karlsruhe (Germany) Fax:(+ 49) 7247-82-6368 E-mail: carsten. vonhaenisch@ int. fzk. de Supporting …
