Ruthenium complexes macrocyclic

We have already seen that imines may be formed by the oxidative dehydrogenation of co-ordinated amines and that this is a commonly observed process, particularly in macrocyclic systems. Likely mechanisms for these dehydrogenations were suggested in Chapter 5, which emphasised the role of the variable oxidation state metal ions in the process. These reactions are quite general and many examples involving iron or ruthenium complexes have been studied in detail. 

Levason, W., Quirk, J. J., Reid, G., Smith, S. M., Synthesis, spectroscopic and redox properties of ruthenium complexes with selenoether macrocycles crystal structures of cis-[RuCl2([16]aneSe4)] and trans-[RuCl(PPh3)([16]aneSe4)]PF6 ([16]aneSe4 = 1,5,9,13-tetraselenacyclohexadecane). J. Chem. Soc., Dalton Trans. 1997, 3719-3724. 

Along with diene and diyne metathesis, ene-yne metathesis has also been employed to form macrocycles. This type of metathesis is performed with the catalysts used for olefin metathesis, and the yields are improved in the presence of ethylene, which forms the highly reactive [Ru]=CH2 species. Shair and coworkers took advantage of this reaction twice in the course of their total synthesis of longithorone A [40]. When ene-ynes 51 and 52 are treated with ruthenium complex G1 under an atmosphere of... 

The metallacycle ruthenium complex 39, bearing a tethered NHC-alkyli-dene unit, catalyzes the formation of cyclic polymers by ROMP of COD (Eq. 28). Polymer formation is believed to proceed through a transient macrocyclic complex in which both ends of the growing polymer chain remain attached to the ruthenium center. Subsequent intramolecular chain transfer releases cyclic polymer [90,91]. 

Ru(bpy)3] + core and six pendant threadlike substituents, forms pseudorotaxanes with macrocycle 4 +. In such pseudorotaxane species, efficient photoinduced electron transfer takes place from the excited state of the ruthenium complex of 19 + to the bipyridinium units of 4" +. 

Of particular interest are the cases where, by a suitable design of the complex, the factors (a) to (d) above can be eliminated so that the departure of the electrochemical response from the purely statistical behaviour arises solely from cause (e). Two examples of such complexes which have been well studied are binuclear ruthenium complexes bridged by 4,4 -bipyridyl type ligands, and binuclear complexes where L, the binucleating macrocyclic ligand, is a symmetric... 

The cyclic ruthenium complex 1 catalyses the polymerization of cis-cyclooctene through the formation of a transient macrocyclic complex 2... 

Figure 2 Nitrosyl macrocyclic ruthenium complexes structure. (A) frans-[RuCI [15]ane4) NO] " and (B) frans-[RuCI cyclam)NO]. The colored circles represent atoms in the chemical structure (cyan (light gray in the print version) carbon blue (black in the print version) nitrogen green (gray in the print version) chlorine red (dark gray in the print version) oxygen white hydrogen, and gray ruthenium).

Nonstrained heterocyclic systems can also serve as suitable substrates for domino ROM/RCM processes [11]. Scheme 2.16 illustrates extended RRM transformations of the tetraenes 38 and 40 embedding two dihydropyran moieties, which proceed with remarkable eflBciency using the ruthenium complex 2 to give the rearranged products 39 and 41, respectively, without unwanted side reactions such as dimer or macrocycle formation [11a]. 

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