Cyclooctadiene complexes

Several authors developed the method further of Ni(0)-mediated couplings to generate several PPP derivatives (9, 13, 14. They described homocouplings of various 1,4-dihalobcnzene derivatives by means of nickel(lI)chloridc/triphenylpho-sphine/zinc or the niekel(0)/cyclooctadiene complex. 

The synthetic route represents a classical ladder polymer synthesis a suitably substituted, open-chain precursor polymer is cyclized to a band structure in a polymer-analogous fashion. The first step here, formation of the polymeric, open-chain precursor structure, is AA-type coupling of a 2,5-dibromo-1,4-dibenzoyl-benzene derivative, by a Yamamoto-type aryl-aryl coupling. The reagent employed for dehalogenation, the nickel(0)/l,5-cyclooctadiene complex (Ni(COD)2), was used in stoichiometric amounts with co-reagents (2,2 -bipyridine and 1,5-cyclooctadiene), in dimethylacetamide or dimethylformamide as solvent. 

In 2004, Dieguez et al. reported the development of novel C2-symmetric dithioether ligands derived from the corresponding binaphthyl or biphenanthryl diols. Thus, various (i )-binaphthyl dithiols substituted by alkyl groups on the sulfur atom in order to increase the steric bulk were synthesised, and the corresponding mononuclear cationic Ir(I) -cyclooctadiene complexes were prepared and characterised (Scheme 8.20). NMR studies demonstrated that, in all cases, the coordination of the ligands proceeded with complete stereoselectivity at the... 

The cyclooctadiene complex H2Ir2Cl2(l,5-C8H12)(PPh3)2, believed to have structure 62, catalyzes the hydrogenation of 1,5- and 1,4-cyclooc-tadienes to cyclooctene (525, 526). 

Square-planar Rh(I)-l,5-cyclooctadiene complexes with antitumor activity include 47-50. In these complexes, the bidentate cycloocta-... 

Such diene complexes can be used to prepare homogeneous hydrogenation catalysts in situ, especially where a variable tertiary phosphine/rhodium ratio is required3 or where an asymmetric tertiary phosphine is employed for asymmetric synthesis.4 The cyclooctadiene complex is also the starting point for the preparation a number of complexes of the type [Rh(l, 5-C8H12)L2]+ (L represents a variety of P— and N— donor ligands) of interest in homogeneous catalysis.s... 

The 1,5-cyclooctadiene complex IrCl(COD)PCy3 is formed when phosphine is added to the easily made and handled [HIrCl2(COD)]2... 

In a different system, l-(trimethylsilyl)cycloocta-l,5-diene forms complexes with Ag(I), Rh(I), Pd(H) and Pt(II), in which the metals are pushed away from the Me3Si group267. The distortion in their structures, in comparison with the near-symmetrical structures of the corresponding 1,5-cyclooctadiene complexes, changes the characteristics of their 111 and 13 C NMR spectra. 

Until recently, little work had been reported on the preparation of metallocarboranes containing more diverse counterligands. The tetra-phenylcyclobutadienc complex [(C6H6) iCi]Pd(l, 2-C2B Hn) was reported in 1966 96), and a cyclooctadiene complex of platinum (II) was subsequently prepared (95). Only in the past 2 years have the existence of phosphine-substituted doso-metallocarborancs been established, and a rich new area of metallocarborane chemistry thereby developed. 

Many of the complexes can be prepared by displacing ethylene from Cramer s compound (equation 19). However, it is more difficult to displace all the cycloocta- 1,5-diene from [RhCl(cod)]2 (equation 20) unless excess ligand is used an intermediate cyclooctadiene complex is formed.77... 

The enthalpies of these exothermic reactions have been determined for chloro, bromo and iodo species.86 Other complexes that have been obtained from the cyclooctadiene complex include [RhCl(PF3)2]2,36 [RhCl P(OMe)3 2]2 and [RhCl PF2(OPr) 2]2.76... 

Many organometallic complexes use cod as a ligand because it can be easily substituted. For that reason, many cobalt cyclooctadiene complexes are important in catalytic reactions, particularly when used with cyclopentadienyl in complexes (Section 5.1.2). ... 

Photolysis of Os3(CO)i2 in the presence of a diene (1,3-butadiene, 1,3-pentadiene, 1,3-cyclooctadiene, or 1,3-cyclohexadiene) gives the mononuclear diene complexes Os(CO)3()]" -diene). The 1,3-cyclooctadiene complex OsCl2(COD)(PEtPh2)2 was prepared by the reduction of [OsCle] " in the presence of the diene followed by treatment withPEtPh2. 

The 1,5 cyclooctadiene complex [Cp Ru(jj rf--C Yiu) (CO)]OTf was isolated upon treatment of Cp Ru(j)" -butadiene)X (X = Cl, Br) with butadiene, AgOTf, and CO. A similar [4-1-4] cycloaddition (a thermally forbidden reaction see Woodward-Hoffmann Rules)) is observed when Cp Ru(isoprene)Cl is treated with iso-prene, AgOTf, and CO. Likewise, the reaction of 1,3-pentadiene with Cp Ru( ) -l,3-pentadiene)Cl results in linear dimerization to form [Cp Ru(4-methyl-(l,3-jj 6-8-j) )-nonadienediyl)]OTf. These types of dimerization occur with both stoichiometric and catalytic amounts of the ruthenium complex. ... 

In an ethanol solution of RhCl3, cis,irons-1,5-cyclodecadiene is converted to its cts,cis-l,6-isomer with subsequent formation of the dimeric rhodium complex [(l,6-CioHie)RhCl]2 which can also be prepared by direct interaction of the 1,6-olefin with RhCl3 in ethanol (579, 582). Spectral evidence suggests a configuration (192) much like that of the 1,5-cyclooctadiene complex with the 1,6-CioHie rings in a boat conformation. 

A 1,4-cyclooctadiene complex has also been recently reported 260). 

According to route A, functionalized organosilanes, derived from a commercially available precursor [68], are first reacted with a suitable metal compound, e. g., a rhodium cyclooctadiene complex, resulting in the formation of a monomeric metal-phosphine complex bearing alkoxysilyl groups. Subsequently in a... 

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