Preferred Coordination Sites for Metal Fragments in σ,π-Bimetallic Complexes. Detailed Mechanistic Insight from Heteroatom, Bridging Ligand, Solvent, Temperature, and Pressure Effects on the Irreversible Exchange of Coordination Sites<sup>1</sup>
作者:Thomas A. Waldbach、Rudi van Eldik、Petrus H. van Rooyen、Simon Lotz
DOI:10.1021/om970494h
日期:1997.9.1
thiophene and selenophene ligands, (η1:η5-XCRCHCHCMn(CO)5)Cr(CO)3 (X = S, R = H (1), R = Me (2); X = Se, R = H (3)), were synthesized from (η5-XCRCHCHCLi)Cr(CO)3 and Mn(CO)5Hal (Hal = Cl-, Br-, CF3SO3-). The complexes 1−3 irreversibly convert at 0 °C in acetone into the complexes (η1:η5-XCRCHCHCCr(CO)5)Mn(CO)3 (X = S, R = H (4), R = Me (5); X = Se, R = H (6)) by exchanging coordination sites. The σ,π- exchange
Synthesis and structure of bimetallic complexes with σ,π-bridged monocarbene ligands
作者:Yvette M. Terblans、Simon Lotz
DOI:10.1039/a700229g
日期:——
The Fischer method was employed to synthesize bimetallic monocarbene
complexes from lithiated
[Cr(SC
4
H
4
)(CO)
3
] and metal
hexacarbonyls. In addition to the formation of
[MC[η
5
-C
4
H
3
SCr(CO)
3
]OEt}(CO)
5
] (M = Cr 1 or W 2) the
complexes
[MC[η
5
-C
4
H
3
SCr(CO)
3
]O(CH
2
)
4
OEt}(CO)
5
]
(M = Cr 3 or W 4), were also obtained. The formation of 3
and 4 is ascribed to the activation of tetrahydrofuran (thf) by a
Ï,Ï-co-ordinated acyl metalate, which triggers the cleavage of
the thf ring and leads to its inclusion into the alkoxy substituent of
the resulting carbene moiety. In polar solvents the Cr(CO)
3
fragments are displaced to give known
pentacarbonyl[ethoxy(thienyl)carbene] complexes and the new mononuclear
carbene complexes
[MC(C
4
H
3
S)O(CH
2
)
4
OEt
}(CO)
5
] (M = Cr 5 or W 6). The analogous
benzo[b]thienyl carbene complex
[CrC[η
6
-C
8
H
5
SCr(CO)
3
]OEt}(CO)
5
] 7 was prepared similarly, but did not
afford the thf-inserted product and the corresponding conversion into
the mononuclear carbene complex
[CrC(C
8
H
5
S)OEt}(CO)
5
] 8, was
much slower.
采用费舍尔法从石化[Cr(SC 4 H 4 )(CO) 3 ]和金属六羰基合成双金属单羰基络合物。除了形成 [MC[δ- 5 -C 4 H 3 SCr(CO) 3 ]OEt}(CO) 5 ](M = Cr 1 或 W 2)络合物外,还得到了 [MC[δ- 5 -C 4 H 3 SCr(CO) 3 ]O(CH 2 ) 4 OEt}(CO) 5 ](M = Cr 3 或 W 4)络合物。3 和 4 的形成是由于四氢呋喃(thf)被Ï,Ï-配位的酰基金属酸盐活化,从而引发了thf 环的裂解,并导致其被纳入所产生的碳烯分子的烷氧基取代基中。在极性溶剂中,Cr(CO) 3 片段发生位移,生成已知的五羰基[乙氧基(噻吩基)碳]配合物和新的单核碳烯配合物 [MC(C 4 H 3 S)O(CH 2 ) 4 OEt }(CO) 5 ](M = Cr 5 或 W 6)。类似的苯并[b]噻吩碳络合物[CrC[δ- 6 -C 8 H 5 SCr(CO) 3 ]OEt}(CO) 5 ]也是这样制备的。类似地制备了 7,但没有得到插入thf的产物,相应地转化为单核碳烯配合物[CrC(C 8 H 5 S)OEt}(CO) 5 ]8 的过程也要慢得多。
The diastereoselectivity of the addition of tricarbonyl-(η6-2-lithiothiophene) chromium(O) complexes on aldehydes
作者:Milan Struhárik、Štefan Toma
DOI:10.1016/0022-328x(94)87009-8
日期:1994.1
It has been shown that the reactions of tricarbonyl(η6 -2-lithiothiophene)chromium(O) with various arene carboxaldehydes yields mixtures of unequal amounts of diastereoisomers, which can be separated by flash chromatography. The structures of the products have been established by 1H NMR spectroscopy and by independent synthesis. A novel synthesis of tricarbonyl(η6-thiophene)-chromium(O) (1) is described
已经显示的是三羰基的反应(η 6 -2- lithiothiophene)铬(O)与不等量对映异构体,其可以通过快速色谱法分离各种芳烃羧醛的产率的混合物。产物的结构已通过1 H NMR光谱和通过独立合成而建立。三羰基的新型的合成(η 6 -噻吩) -铬(O)(1)进行说明。