Mononuclear Rhenium Complexes

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

There are three rhenium xanthate structures in the literature and two of these are binuclear. The mononuclear complex of formula (Me5C5)ReCl3(S2COCy) (46) is represented in Fig. 26. The rhenium atom is considered to exist in a... 

It is noted [181] that mononuclear complexes of divalent rhenium are rare, and coordination of two different radical ligands to a single metal is also unique. ... 

The synthesis of pentacarbonyl rhenium(I) halides, Re(CO)5X, succeeded from simple and complex rhenium halides below 200 atm of CO at 200° C. The compounds are extraordinarily stable and form easily, often quantitatively, from carbon monoxide and rhenium metal in the presence of other heavy metal halides or halogen sources such as CC14. Later we prepared the corresponding carbonyl halides of manganese (67) and technetium (68) from their respective carbonyls. It was found that the corresponding binuclear tetracarbonyl halides [M(CO)4X]2 (M = Mn, Re) could be made by heating the mononuclear M(CO)5X complexes (15, 69), as well as by other methods. 

Suspected Si H—M interactions were also discussed in connection with the mononuclear complexes HReCp(CO)2(SiPh3) 161), HMnCp(CO)2(SiPh3) 161,162> and HFeCp(CO)2(SiF2Me)2 163>. From an analysis of known or estimated Si — H distances, it was concluded that Si — H interactions were most likely absent in the rhenium and iron complexes. In the case of HMnCp(CO)2(SiPh3), it was originally believed that a true example of Mn—H Si interaction existed162), but a subsequent re-assessment of the problem indicates that the structural evidence is, at best, inconclusive 161.163). 

Photochemical Reactions of the Ligand in Re(I) Complexes Rhenium(I) Complexes as Highly Efficient Photocatalyst A. Mononuclear Rhenium(I) Complexes Reaction Mechanism Multicomponent Systems... 

All these polymers, A (39), B (40), C (41,42), D (43), showed distinctive absorption and emission due to the MLCT transition of the rhenium(I) diimine complexes. Among these rhenium-containing polymers, polymer C has the most notable emission properties, with an emission quantum yield and a lifetime ( e = 0.132, Te = 2019ns in a deaerated CH2CI2 solution) comparable to those of the corresponding mononuclear complex (0e = O.181, Te = 2200 ns) (43). 

Binuclear complexes of naphthalene (VIII) and of benzene (IX) with [Os(NH3)5]2+ and [Ru(NH3)5]2+ moieties were reported by Taube et al. (19), in which anti- //-1,2-rj2 3,4- 2) coordination of the arene is present. This bonding mode was first observed by Pasman et al. (20) in the binuclear Rhenium complex X. Wolczanski et al. (21) obtained complex XI from the mononuclear complex [Ta(0—Si Bu3)3 2-(N,C)-pyridine ] and benzene. Each tantalum atom is bound unsymmetrically to one C=C bond of benzene with a weak interaction to a third carbon atom the bonding may be described as a distorted tj3-enyl. In the dinuclear cobalt complex XII, the xylene functions as a bis(enyl)-ligand (12,22). 

Re(CO)3(bpy)(OTf)] reacts with ligand 104 in ethanol to afford the mononuclear complex 105 (97JPC(B)3174). The product reacts further with [Re(CO)3(bpy)(OTf)] to yield the dinuclear complex 106. When anchored on the surface of silver or gold, 106 is rearranged to the surface mononuclear complex 107. Another surface complex on silica formed from the rhenium(I) species with similar ligands may be formulated as -[Si](CH2)4(Mebpy)2Re(CO)3Cl (92JCS(CC)1615). 

Finally, insertion of alkynes into dihydrogen mononuclear cationic rhenium complexes, stabilized by the triphos (= l,l,l-tris(diphenylphosphinomethyl)ethane) ligand, leads to vinylidene derivatives which react with water or ethanol eliminating silanols or methane, Fig. 18. Solvents were acetone or THF no chromatography was used. 

Most complexes of this oxidation state are derivatives of the rhenium(III) halides. They are classified according to the other ligands (if any) that are present. For example, ReChfPRjlj will be found under phosphine complexes rather than halide complexes . Mononuclear complexes of rhenium(III) are mostly of the types [ReX2L4]" and ReXjL, but rarely [ReX4L2] . Additionally, two very important classes of complexes exist that are derivatives of the quadruply bonded dinuclear [RcjXg] and doubly bonded trinuclear [RejX,2] anions (X = Cl, Br or I). ... 

The history of organometallic complexes suitable for cell imaging goes back to 2004 with the synthesis by Valliant and coworkers of the c-rheniirm tricarbonyl bispyridyl complex 4 (Scheme 11.3) [48,49]. Like most, if not all, of the rhenium mononuclear complexes used as luminescent agents for cell imaging, this complex contains a c-Re(CO)s unit and possesses the general formula of l /flc-[Re(CO)3(N N)L]. 

No technetium complexes of sulfoxides have been reported. Mononuclear rhenium(V) complexes of the types [Re02Cl(Me2S0)] (246) and... 

Compounds of the composition [ReOCl3(N N)] have also been isolated with pyridine-2-aldi-mine and rr-acidic arylazopyridine and arylazoimidazole ligands." The products (101) are readily reduced by oxygen atom transfer reactions from Re to phosphorus atoms of phosphines which results in the formation of rhenium(III) complexes. Depending on the reaction condition and the phosphines used either mononuclear or binuclear compounds are formed." " Azo splitting reactions with arylazopyridines give access to arylimido and binuclear oxo/imido com-plexes. "" ... 

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