Osmium complexes cyclopentadienyl

Arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal(O) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. 

Two arene cyclopentadienyl osmium complexes of type 191 have been prepared in moderate yields (17-43%) by reacting precursor 144 with thallium cylopentadienide in acetonitrile (73). 

Osmium forms a wide variety of alkyl and aryl complexes including homoleptic alkyl and aryl complexes and many complexes with ancillary carbonyl (see Carbonyl Complexes of the Transition Metals), cyclopentadienyl (see Cyclopenta-dienyl), arene (see Arene Complexes), and alkene ligands (see Alkene Complexes). It forms stronger bonds to carbon and other ligands than do the lighter elements of the triad. Because of this, most reactions of alkyl and aryl osmium complexes are slower than the reactions of the corresponding ruthenium complexes. However, because osmium is more stable in higher oxidation states, the oxidative addition (see Oxidative Addition) of C-H bonds is favored for osmium complexes. The rate of oxidative addition reactions decreases in the order Os > Ru Fe. 

Osmocene is a photoactive compound. Photolysis of osmocene in n-hexane led to metallic osmium by reductive elimination. In the LF excited triplet state, osmocene undergoes a distortion by bending, which facilitates the transfer of a CH group between the cyclopentadienyl ligands. The resulting intermediate is an osmium complex with benzene and cyclobutadiene ligands, that decomposes to osmium metal, benzene and cyclobutadiene. ... 

The preparation of two cyclo-octatetraene-gold complexes, (ct)AuCl and (cot)-AU2CI4, has been reported. The structures of biscyclo-octatetraenyl complexes of titanium, vanadium, thallium, and uranium, were deduced from their i.r. spectra. Protonation of (p-cyclo-octatetraene) (p-cyclopentadienyl) complexes has been studied. For the ruthenium and osmium complexes protonation occurs on the eight-membered ring to give CgH moiety co-ordinated to the metal atom via both an T -alkyl and an olefin-metal bond. For the cobalt and rhodium complexes a bicyclic cation (287) is produced which undergoes isomerization to the monocyclic (288). ... 

HjNiOcjOsjCuHs, Osmium, nonacarbonyl-( tl -cyclopentadienyl )tri- x-hydridonickeltri-, 26 362 H,NiO,Ru,C14H5, Ruthenium, nonacar-bonyl-f-rf-cyclopentadienyl)-tri-p.-hydridonickeltri-, 26 363 H4N, Hydrazine ruthenium(II) complexes, 26 72 H40 20sjCi , Osmium, dodecacarbonyl-tetra- x-hydrido-te/rahedro-tetra-,... 

Binding energy, pentacarbonyliron, 6, 3 Binuclear complexes bis-Cp titanium halides, 4, 522 with Ni-M and Ni-C cr-bonds heterometallic clusters, 8, 115 homometallic clusters, 8, 111 Binuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, with rand C5 ligands, 6, 178 Binuclear iridium hydrides, characteristics, 7, 410 Binuclear monoindenyl complexes, with Ti(IV), 4, 397 Binuclear nickel(I) carbonyl complexes, characteristics, 8, 13 Binuclear osmium compounds, with hydrocarbon bridges without M-M bonds, 6, 619... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Mononuclear osmium half-sandwiches, with rf-cyclopentadienyls and 7]5-indenyls alkenyls and allenyls with t/-M-C bonds, 6, 558 alkenyl vinylidenes, 6, 593 alkyl, aryl, acyl complexes, 6, 552 with alkylidyne complexes, 6, 599 alkynyl and enynyl complexes, 6, 567 allenylidene and cumulenylidene complexes,... 

N) and rf n) fashion. Besides in the complexes containing the fused cyclopentadienyl or phenyl ring, the coordination is fulfilled via the latter and these complexes possess valuable catalytic properties. Ruthenium and osmium compounds present a variety of the /(N)-coordinated structures, although in osmium chemistry, the rj2(C,C) coordination is also possible. 

While inorganic complexes of osmium in oxidation states +4 through +8 have been known for many years, the study of high-valent alkyl and aryl complexes of osmium is much more recent. The organometallic complexes include homoleptic see Homoleptic Compound) alkyls and aryls, oxo alkyls and aryls, nitrido/imido alkyls and aryls, and cyclopentadienyl see Cyclopentadienyl) alkyls and aryls. The majority of these are complexes of osmium(VI). 

A. G. (1980) Cyclopentadienyl-ruthenium and -osmium chemistry X. Reactions of vinylidene complexes with alcohols and water synthesis of alkoxy (alkyl) carbene, aryl and alkyl complexes. Australian Journal of Chemistry, 33, 1471-1483 (c) Bruce, M.I., Swincer, A.G., Thompson,... 

Fenske s theoretical studies on cyclopentadienyl-substituted carbyne complexes indicate a remarkable charge on the carbyne carbon atom [25]. This existence of a nucleophilic carbyne carbon becomes evident in the protonation of different carbyne complexes of molybdenum [26], tungsten [27-29]) and osmium [30]. 

---