Cadmium amine ligands

Both zinc and cadmium form numerous complexes with amine ligands, ranging from NH3 through diamines such as ethylene diamine and substituted propylene diamines,54 to a variety of macrocycles.55 56 Pyridines and pyrazoles are also good ligands.57,58 In the case of 1,3,5-triaminocyclo-hexane, a regular octahedral complex cation is formed, as shown in Fig. 15-4. With 3-Me-pyrazine, tetrahedral [Zn(C4N2H6)4]2+ is formed.59... 

Cd. Cadmium perchlorate was found to catalyze allylation reactions using allyltributyltin in aqueous media very efficiently.177 These cadmium-catalyzed allylation reactions are accelerated by ligands such as N, N, N, N", A -pentamethyldicthylcnetri amine or 2,9-dimethylphenanthroline (Eq. 8.75). This accelerated the catalytic system to give allylation products of various aldehydes and ketones in high yields. 

Bis(2-dimethylaminoethyl)methylamine]Cd(NCS)2 contains five-coordinate cadmium in a square pyramidal environment the apical position is occupied by N-bonded thiocyanate (Cd—N = 2.18 A) while the basal positions are occupied bv the amine (Cd—N = 2.34-2.37 A) and the second thiocyanate (Cd—N = 2.21 A) ligands.217... 

Because the reactions of related in -cyclohexadienyl complexes are synthetically valuable, the reactions of this ligand have been studied extensively. An outline of how this chemistry can be conducted on the Fe(CO)j fragment is shown in Equation 11.51. A variety of cyclohexadienes are readily available from Birch reduction of substituted aromatics. Coordination and abstraction of a hydride, typically by trityl cation, leads to cationic cyclohexadienyl complexes. These cyclohexadienyl complexes are reactive toward organolithium, -copper, -cadmium, and -zinc reagents, ketone enolates, nitroal-kyl anions, amines, phthalimide, and even nucleophilic aromatic compounds such as indole and trimethoxybenzene. Attack occurs exclusively from the face opposite the metal, and exclusively at a terminal position of the dienyl system. This combination of hydride abstraction and nucleophilic addition has been repeated to generate cyclohexa-diene complexes containing two cis vicinal substituents. The free cyclohexadiene is ttien released from the metal by oxidation with amine oxides. ... 

Reactions of zinc(n) and cobalt(n) complexes of ida, Hida, nta , Eten, and dien with cydta - and Hcydta have been studied. The steric effect of the cyclohexane ring in cydta on the rate of substitution is discussed. Other reports of the replacement of one multidentate ligand by another have appeared for the systems Ni(Hida) + dtpa, Ni(edta-OH) -I- dtpa, and Co(gedta) + (edta-OH) [Hida = A-(2-hydroxyethyl)iminodiacetate, (edta-OH) = lV-(2-hydroxyethyI)ethylenedi-amine-AW A -triacetate, gedta = 2,2 -ethylenedioxybis(ethyIamine)-AAW JV -tetra-acetate). Similar studies of aminopolycarboxylate replacement have appeared for zinc(n), lead(n), and cadmium(n). ... 

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