Ruthenium coordination polymers

Well-defined and readily soluble ruthenium coordination polymers (61) have been synthesized through the reaction of a bisbidentate ligand and a metal center that already possesses one bidentate ligand (189-191). In these complexes, the random stereospecificity at the ruthenium centers results in a ribbon-like conformation of the polynners with the extension of the chain dependent upon the substituent R. The Ru centers appear to behave independently and the polymers appear to be stable against heat and uv irradiation. They have molecular weights on the order of Mw = 40,000-50,000. 

Polymers containing benzimidazole units in their backbones have also been used in the synthesis of coordination metallopolymers (159-162). Osmium and ruthenium coordinated polymers with bipyridine ligands have been prepared (159,160). These polymers (72, 73) possessed metal-metal interactions through their conjugated backbones. Communication between the ruthenium centers of 72 increased by deprotonating the imidazole protons (160). The osmium coordinated polymer (73) showed two reduction waves separated by 0.32 V, indicative of strong cnmmimication between the Os centers (159). 

Petzold and Harruna have synthesized three-dimensional high-performance coordination polymers. A munber of these thermally stable, soluble ruthenium-coordinated polymers (47) were examined by optical spectroscopy. Solutions of rigid polyamides exhibited birefringence and the 3D polymers emitted at a Vax of 620 nm. 

Kelch, S. and Rehahn, M. (1997) High-molecular-weight ruthenium(II) coordination polymers synthesis and solution properties, Macromolecules, 30, 6185-6193. 

C. Carraher, A. Murphy, Ruthenium-Containing Polymers for Solar Energy Conversion, Chapter 13 in Macromolecules Containing Metal and Metal-Like Elements, Vol. 5, Metal Coordination Polymers, A. Abd-El-Aziz, C. E. Carraher, Jr., C. U. Pittman, Jr., M. Zeldin, Eds., pp. 325-342, Wiley, Hoboken, NJ, 2005. 

Lidrissi et al. synthesized air-sensitive, water-soluble coordination polymers containing two different organometallic moieties.198 After reacting a cyclopentadienylruthenium complex containing water-soluble phosphane groups with AgOTf, polymers were isolated containing both ruthenium and silver (Scheme 2.33). 

CD study shows that the configuration of the octahedral chiral element is controlled by that of the hgand, being (A) for the hgand (—)-[ctpy-x-ctpy] (6.54). The chemistry of these coordination polymers is directly related to the work of von Zelewsky on the enantioselective formation of chiral mono- and binuclear ruthenium (II) complexes. 

R 473 G. J. Kleywegt, K. Hendrick, E. J. Dodson and D. M. F. Van Aalten, Pound-Wise but Penny-Foolish How Well Do Micromolecules Fare in Macromolecular Refinement , Structure, 2003,11,1051 R 474 R. Knapp, S. Kelch, O. Schmelz and M. Rehahn, Synthesis and Properties in Solution of Ruthenium(II) Coordination Polymers , Macromol. Symp., 2003,204, 267... 

More polar functional groups such as ketones are hydrogenated effectively with homogeneous cationic rhodium and ruthenium complexes. Polymer catalysts active for both olefin and ketone hydrogenation activity were synthesized from ionic precursors such as Rh(norbornadiene)(acac) + HCIO4 or Rh(norbornadiene)(PE 3)2 + C104. Two types of coordination were observed, depending on the method of attachment " ... 

Impressive results in terms of the synthesis and characterization of soluble linear Ru-polypyridyl coordination polymers were reported in 1997 [10]. Reaction of tetrapyridylphenazine (tppz) with impure ruthenium precnirsors [Ru(R2bpy)Q3]x was found to give fairly low molecular weight polymers 7.3 with M 16,000 (DPn 15) (Eq. 7.2). However, when stoichiometric balance was possible due to... 

Very recently, several five and six-coordinate ruthenium monocarbene complexes have also been structurally characterized by the groups of Che [141] and Miyamoto [142-144], X-ray crystal structure determinations revealed Ru = C distances of 1.806(3)-1.876(3) A, comparable to those in the previously reported analogues (Table 3). In one case, (TPFPP)Ru[C (p-C6H40Me)2], the complex is a one-dimensional coordination polymer [141]. In this particular complex, the carbene groups function as bridges through the carbene carbon atom and one of the two methoxy oxygen atoms. Many of these complexes were also characterized by H and C NMR [141]. 

Polymers whose backbones consisted solely of metal-metal bonds have been synthesized by electrochemical reduction of ruthenium and osmium complexes (47,48). Reduction of [M Htra s-Cl2)(bipy)(CO)2] (M = Ru, Os) (24) to M° complexes generated a polymeric film (25) following loss of the trans chloride ligands (48) (eq. 8). Both the ruthenium- and osmium-based coordination polymers were selective for the reduction of carbon dioxide. 

There are numerous examples of dendrimers and star polymers containing metal coordination complexes (253-259). The synthesis of polypsrridine ruthenium coordination complexes incorporating Fe and Co (113) has been established (255). A ruthenium star-shaped complex with a CpFe" "-coordinated arene as the core has also been reported (254). 

Pyrolysis products from organometallic phosphazenes can give nano-structured materials. Mixtures of AuCllPPhs) and poly[2,2 -dioxy-l,l -biphenylphosphazene] were pyrolyzed by heating the sample at 10 °C/min. to 800 °C, which was held for 2 hours under a flow of air. Characterization of the products by X-ray diffraction revealed a nanostructured Au material. Additional experiments were performed with metal centers directed bound to the phosphazene substrate. Structure (43) shows a phosphazene linear polymer substituted with 2,2 -biphenol and 4-hydroxyphenylacetonitrile pendant groups, with ruthenium coordinated to the terminal cyano groups. 

Collman JP, McDevitt JT, Leidner CR, Yee GT, Torrance JB, Little WA (1987) Synthetic, electrochemical, optical, and conductivity studies of coordination polymers of iron, ruthenium, and osmium octaethylporphyrin. J Am Chem Soc 109 4606-4614... 

Dembek et al. later prepared polyaromatic ethers and thioethers coordinated to pentamethylcyclopentadienylruthenium moieties (Scheme 11) The inherent viscosities of the polymer solutions (0.5%) were measiued in DMF to be between 0.52 and 1.49 dL/g. Lithium chloride was added to these ruthenium-based polymers (48) in order to suppress polyelectrolyte effects. 

A number of examples of oligomers and polymers containing metal-metal multiple bonds also have been reported. " Chisohn has synthesized polymers with metal-metal single and multiple bonds from bimetallic carboxylates and coordinating ligands. Scheme 24 illustrates the synfliesis of a ruthenimn coordination polymer that contains Ru-Ru double bonds. Polymer 81 was prepared from reaction of the ruthenium carboxylate monomer (79) wifli pyrazine (80). The polymer dissociated in coordinating solvents such as THF, and the MW was dependent on its concentration in noncoordinating solvents such as benzene. The polymer was thermally stable only to 140°C, at which point pyrazine was evolved. 

There are numerous examples of dendrimers and star polymers that contain metal coordination complexes based on pyridine ligands. There is also interest in the incorporation of more than one type of metal complex into these materials. Constable and coworkers have reported the synthesis of heptametallic complexes containing six peripheral ruthenium coordination complexes and a central iron or cobalt complex. Scheme 21 illustrates the reaction of 89 with either iron or cobalt complexes to produce the heptametallic dendrimer 90. A heptametallic star-shaped complex with a CpFe -coordinated arene as the core and ruthenium Aexa-pyridine complexes at the periphery has also been reported by Astruc. ... 

Newcome and coworkers have reported the synthesis of a tetraarm complex containing two ruthenium coordination complexes in each branch. Polymer 91 was prepared by reaction of a core molecule containing four terpyridine units with 4 eq of a bimetallic complex containing a reactive ruthenium trichloride moiety. 

Hinderberger D, Schmelz O, Rehahn M, Jeschke G (2004) Electrostatic site attachment of divalent counterions to rodlike ruthenium(II) coordination polymers characterized by EPR spectroscopy. Angew Chem Int Ed 43 4616-4621... 

Smaller ruthenium-based macrocycle [(Ru(acac)2)2(it -dppa)2] (104) with dppa bridges was prepared recently by heating coordination polymer 103, which was obtained from Ru(acac)2(coe)2 by ligand exchange (Fig. 2.37) [101]. The crystal... 

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