Group 10 and 11 Complexes

As mentioned in the Introduction, one of the synthetic approaches to stable nucleophilic carbenes involves C-deprotonation of imidazol-ium and related cations with alkali metal salts of strong bases such as NaH and KO Bu. Accordingly, the interactions with alkali metal cations with stable nucleophilic carbenes could prove to be important for understanding the solution behavior of the latter. Until recently, however, there were no examples of complexes of stable carbenes with 

Like L (vide infra), can form bis(carbene) complexes, 9 (13), These homoleptic complexes, which feature C-H-C interactions, were formed by treatment of 4 (R = Mes R = H) with the corresponding 

Nucleophilic carbene 4 (R = Me, R = H) has been shown to disrupt the polymeric structure of beryllium dichloride to form an ionic carbene complex, 10 15). The crystal structure of 10 revealed that the cation possesses a distorted tetrahedral coordination geometry at the beryllium center. The average Be-Cl bond distance (2.083(7) A) is 

CsMes rings (16, 17). (The Sr(i7-C5Me5)2 OEt2 product was not suitable for complete X-ray crystallographic assay). A third coordination mode, namely bis-monohapto (18), was evident in the product of the Zn r] -C5Me5)(i7 -C5Me5) reaction. For each of the complexes 15-18, the shortest metal-carbon distances are those to the carbene center (2.194(2), 2.561(3), 2.951(3), and 2.022(3) A in 15, 16, 17, and 18, respectively). If the centroids of the rf-C Me rings are considered to 

It is also possible to isolate bis(carbene) complexes involving the heavier alkaline earth metals. Thus, the reaction of two equivalents of 4 (R = Me or Bu, R = H) with calcium, strontium and barium bis(trimethylsilyl)amides [M N(SiMe3)2 2(thf)2] (M = Ca, Sr, Ba) resulted in the displacement of two thf molecules to afford the corresponding biscarbene species, 19 19). The solubilities and stabilities of these complexes were found to decrease from calcium to barium. 

Complex 5um of Pn angles (°) Pn-M bond length (A) 5umof Pn-M covalent radii [155] (A) References 

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Coles MP, Hitchcock PB. Bicyclic guanidinates in mono- and di-valent metal complexes, including group 1/2 and group 1/12 heterometaDic systems. Angew Chem Int Ed. 2013 66(10) 1124-1130. 

The water initiated polymerization of lactams represents the classical, industrially widely used process and, therefore, a large effort has been devoted to the investigation of the kinetics and mechanism of the individual reactions. In order to establish the accepted reaction mechanism, the concentration of all components involved in the complex set of reactions had to be followed during polymerization and determined at equilibrium. Thorough studies by Hermans, Heikens, Kruissink, Reimschuessel, Staverman and by van der Want as well as by Wiloth elucidated the complex scheme of equilibrium reactions involving water, cyclic and open chain amide groups, amine and carboxyl groups [1, 2, 4, 5, 12, 13, 15, 22, 23,177, 214-235]. 

Oxidative insertion into the arylbromide, carbonylation, and nucleophilic attack on the carbonyl M. Mori et al Heterocycles, group with elimination of Pd(0) completes the catalytic cycle. No doubt the palladium has a 1979,12, 921. number (1-2) of phosphines complexed to it during the reaction and these keep the Pd(0) in solution between cycles. 

A rhodium complex 4b or 5b, bearing a triethoxysilyl group (0.2 mmols) in dry dichloromethane was added to a suspension of zeolite (1 g, previously dried at 140°C/0.01 mm Hg) in dry toluene and the mixture was stirred for 24 hours at room temperature. The solid was then filtered and Soxhlet-extracted with dichloromethane-diethyl ether (1 2) for 12 hours to remove the remaining non-bonded complex, and dried in vacuo. The analytical data for the supported complexes are shown in Table 3. 

The complexes between lanthanoid salts and crown ethers are usually isolated from nonaqueous solutions, the Ln(III)/polyether interaction being very small in water due to unfavorable energetics in removing water molecules from the inner coordination sphere of the metal ion. We report here the synthesis and the properties of complexes with 12-crown-4, 15-crown-5, and 18-crown-6 ethers, having different metal/crown ratios, namely 1 1, 1 2, and 4 3. The singlecrystal X-ray structures of four complexes have been solved. In the 1 1 complexes Eu(N03)3 (12-crown-4) and Eu(N03)3-(15-crown-5), which crystallize in a chiral space group, and Nd(N03)3-(18-crown-6), the metal ion displays coordination numbers of 10, 11, and 12, respectively. The first two complexes have similar structures the polyether sits to one side of the Eu(III) ions and the three bidentate nitrate groups are coordinated on the opposite side. The structure of [Nd(N03)3]4-(18-crown-6)3 revealed that this complex has to be formulated as [Nd(N03)2-( 18-crown-6)]3[Nd(N03)3]6. 

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