Containing Metallocycles

When the reaction between [(2-MeC3H4)Pd(C5H5)] and dimethyl H-phosphonate is carried out at low temperatures and excess of phosphonate, the main reaction product is a 7t-(2-methyl)allyl-containing metallocycle [430]. 

Mixed phosphorus compounds, bearing at least two different tervalent phosphorus moieties have been developed and have found several applications in catalysis. Iri li described the synthesis of aminophosphine-phosphinite ligands 149 and 150, from the commercially available 3-piperidinemethanol and 3-(methylamino) pro-pan-l-ol. Their palladium and platinum complexes 151 and 152, containing metallocyclic rings, were obtained as air-stable compounds with high yields, and characterized by P, and NMR spectroscopy, FTIR spectroscopy and X-ray crystallography. The Pd complexes were effective catalysts on Suzuki-Miyaura cross-coupling reactions of various aryl chlorides and atyl bromides with phe-nylboronic acid. 

When acetylthiophenes are subjected to orthomanganation, formation of the 2,3-, 103, and 3,4-, 104, metallocycles is observed [88JOM(349)197]. Complex 103 contains two coplanar live-membered heterocycles with octahedral manganese. Complex 104 is also planar. In both cases, substantial delocalization of the TT-electron density follows from the structural parameters. 

Depending on the nature of the substrates, selectivity could be completely reversed between the two isomeric products. For example, switching R1 group between Buc and Ph gave high yields of the first and second product structures, respectively. The authors noted that the reaction did not proceed if the imine contained an ortho-MeO group at R2 or if the imine was replaced with an aldehyde, oxime, or hydrazone. The catalytic cycle is initiated by C-H activation of the imine, that is, the formation of a five-membered metallocycle alkyne insertion affords the intermediate drawn in Scheme 69. It is noteworthy that this is the first report of catalytic synthesis of indene derivatives via a C-H insertion mechanism (C-H activation, insertion, intramolecular addition). 

The asymmetric structures which incorporate Al-0 edge-fused rings of different size all contain (AlO) metallocycles in which n = 2, 5 or, in an isolated instance, 8. The retention of at least one four-membered heterocycle n = 2) relates these systems to the symmetric polycycles discussed above in all but one aluminium oxide. 

Decomposition reactions following the (3-elimination mechanism are generally considerably faster than the decomposition reactions of the corresponding alkyl complexes. The decompositions of the L, M"+I CR R2CR3R4X transients that follow first order rate laws, are often acid catalyzed and produce usually the corresponding alkenes, Mre+1Lm, and X- as the final stable products. In some cases intermediates containing the alkenes bound to the metal-complex are observed (55,71,144). Thus the first product in all (3-elimination processes seems to be a -complex (or actually a structure between the extreme descriptions as -complex and that as a 3-ring metallocycle)... 

The reaction of 36 with carbon monoxide results in the formation of the neutral [Ira CO C/ -COX/ -C Xdppm ] 39, which, according to an X-ray crystallographic analysis, no longer contains an Ir—Ir bond [the M-M separation is 3.388(2) ]. This compound may be the first example of a compound that contains a five-membered metallocycle in which the -02- unit and the carbonyl unit are both bridging. 

Ni(cod)2] in the presence of the diphosphines Ph2P(CH2) PPh2 (n = 1-4) catalyzes the reaction of 1-hexyne with C02 to give the lactone (125) in addition to products not containing C02 (equation 155).586 The best results regarding the phosphorus ligands were obtained with n=4. The reaction was believed to proceed via a metallocycle formed by dimerization of the 1-hexyne at a nickel(0)-phosphine complex (equation 156). 

Another example of an eight-membered metallocycle containing Au(II) centers is the dithiocarbamate complex (9) (20), obtained from the gold(I) dithiocarbamate complex (8) with halogens or pseudohalogens at -78° in C. However, these compounds disproportionate to form mixed-valence salts (10). It was shown that the vCs band of the coordinated dithiocarbamate is sensitive to the oxidation state of the gold, increasing in the order 1495, 1523, and 1547 cm-1 for the Au(I), Au(II), and Au(III) complexes, respectively (20). 

The complex obtained on the basis of thiocarbazone of 2-furylaldehyde has the structure containing a five-member metallocycle [821]. Two five-member and one six-member metal-cycles are formed in the nickel complex shown by 466 [822],... 

Silylenes can be defined as molecules containing a neutral dicoordinate metallene atom possessing two unshared valence-shell electrons. The addition of these short-lived species to double and triple bonds is a practical route for the synthesis of three-membered metallocycles. However, if the [2+1] cycloaddition is followed by insertion of a second silylene molecule, the formation of a four-membered metallocycle takes place. 

Besides metallocycles, metallodendrimers, and metallo-supramolecular polymers [58], few examples of hollow supramolecular architectures have been obtained from polytopic ligands containing terpyridine units. Lehn et al. used heteroaromatic ligands with terpyridine type coordination sites to obtain cylindrical self-assembled architectures (Fig. 11) [60]. For synthesis of the cage 37, tris-2,4,6-(2-pyrimidyl)-l,3,5-triazine (35) was mixed with lead triflate in... 

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