Diamino‐Substituted Carbene Transfer between Transition Metal Ions

Diamino‐carbene ligand transfer between various metalions is studied, particularly with Pd (II) to Rh(I), Rh(I) to Au(I). Reactions of various carbene complexes with AgPF₆ result in the cleavage of the M=C bond to give the protonated carbene species, imidazolidin‐2‐ylidinium salt, indicating the presence of free carbene ligand in the reaction medium. When the carbene transfer process was carried out in tetrahydrofuran, the polymerization of tetrahydrofuran occurred.     

1,2,4-Triazolium-5-ylidene and 1,2,4-triazol-3,5-diylidene as new ligands for transition metals

Ab initio calculations show the 1,2,4-triazolium-5-ylidene (3a) and 1,2,4-triazol-3,5-diylidene (4a) are true minima on the potential surface. As expected, 4a is much higher in energy than its triazole isomers 5a, 6a and 8a and the 1,2,4-triazol-3-ylidene (7a). Sodium methoxyde adds to the diquaternary salt of 1,2,4-triazoles (9b,c) to give the corresponding monocationic heterocycles 10b,c in 70 and 50% yield, respectively. One equivalent of silver(I) acetate reacts with 9b leading to the bis(1,2,4-triazolium-5-ylidene)silver(I) complex (11b) in 80% yield. Under the same experimental conditions, but using two equivalents of silver(I) acetate, solid-state one-dimensional polymers 12′b,c featuring the coplanar 1,2,4-triazol-3,5-diylidene ligands coordinated to silver(I) are obtained in 90% yield. 12′c has been fully characterized including a single-crystal X-ray diffraction study.     

Carbene Complexes of Pnictogen Pentafluorides and Boron Trifluoride

Summary.  Synthesis, characterization, and solid state X-ray crystallographic structures for 12-Pn-6 complexes derived from carbene 4,5-dichloro-1,3-dimesitylimidazol-2-ylidene and phosphorus, arsenic, or antimony pentafluoride are reported. The adducts show octahedral geometries at the pnictogen centers with C-Pn bond distances of 189.8 (P), 199.9 (As), and 217.5 (Sb) pm. The structures are those of internal zwitterions with imidazolium ion character in the heterocyclic ring and a pentafluoropnictanide anion bonded to C². Adducts of BF₃ with 1,3-dimesitylimidazol-2-ylidene and 4,5-dichloro-1,3-dimesitylimidazol-2-ylidene are also reported for comparison. Although the reactivity of chlorinated and non-chlorinated carbenes varies considerably, the spectroscopic and structural properties of analogous adducts are remarkably similar. Received September 6, 1999. Accepted (revised) October 20, 1999     

卡宾与醚C—H键插入反应的理论研究（Ⅳ）：CX2（X=H,F,Cl）与甲基苄基醚C—H键的插

卡宾与醚类中不同 C—H键的插入反应可生成众多的不同产物 ,是有机化学中令人感兴趣的研究课题 ,对此已有一些实验研究[1～ 5] ,其主要结论由产率分析而得 .在前文[6～ 8] 中 ,我们曾用量子化学方法分别研究了 CX2 (X=H,F,Cl)与二甲醚和甲乙醚的 C— H键插入反应 .林启君等[3] 在实验上研究了二溴卡宾与甲基苄基醚的 C—H键插入反应 ,从产率分析可知 :苯基将使其相邻的碳原子即苄基中与氧原子相连的 α-C上的 C—H键更容易与卡宾发生插入反应 .本文用密度泛函理论在 B3 L YP/ 6-3 1 G(d)水平上研究了卡宾 CX2 (X=H,F,Cl)与甲基苄…     

Dimensional Matching versus Induced-Fit Distortions: Binding Affinities of Planar and Curved Polyaromatic Hydrocarbons with a Tetragold Metallorectangle

A tetragold(I) rectangle-like metallocage containing two pyrene-bis-imidazolylidene ligands and two carbazolyl-bis-alkynyl linkers is used for the encapsulation of a series of polycyclic aromatic hydrocarbons (PAHs), including corannulene. The binding affinities obtained for the encapsulation of the planar PAHs guests in CD₂Cl₂ are found to exponentially increase with the number of π-electrons of the guest (1.3 > logK >6.6). For the bowl-shaped molecule of corannulene, the association constant is much lower than the expected one according to its number of electrons. The molecular structure of the host–guest complex formed with corannulene shows that the molecule of the guest is compressed, while the host is expanded, thus showing an interesting case of artificial mutual induced-fit arrangement.