Osmium , crystal structure

The ruthenium-copper and osmium-copper systems represent extreme cases in view of the very limited miscibility of either ruthenium or osmium with copper. It may also be noted that the crystal structure of ruthenium or osmium is different from that of copper, the former metals possessing the hep structure and the latter the fee structure. A system which is less extreme in these respects is the rhodium-copper system, since the components both possess the face centered cubic structure and also exhibit at least some miscibility at conditions of interest in catalysis. Recent EXAFS results from our group on rhodium-copper clusters (14) are similar to the earlier results on ruthenium-copper ( ) and osmium-copper (12) clusters, in that the rhodium atoms are coordinated predominantly to other rhodium atoms while the copper atoms are coordinated extensively to both copper and rhodium atoms. Also, we conclude that the copper concentrates in the surface of rhodium-copper clusters, as in the case of the ruthenium-copper and osmium-copper clusters. 

Fig. 24. Comparison between the osmium- and ruthenium-arenes, exemplified by the respective [M(ri6-bip)Cl(en)]+ complexes. Although the crystal structures show the complexes to be isostructural with similar M-Cl bond lengths (a), the properties of the complexes are quite different, illustrated by the differences in hydrolysis rate h1/2), pAa, and 5 -GMP binding (the black box denotes the amount of OP03-bound 5 -GMP) (b).

The crystal structure of (ij4-cyclooctatetraene)(hexamethylbenzene)ruthenium (16) indicates bonding as a tetrahapto ligand60. For this complex and similar iron-, ruthenium- and osmium-(ij4-cyclooctatetraene)(arene) complexes, their XH and 13C NMR spectra exhibit only a single signal for the cyclooctatetraene ligand at temperatures as low as —145 °C. Using this temperature, the barrier-to-metal migration is estimated to be <6.6 kcal mol 1. 

There are a number of osmium(VI) oxo complexes containing cyanide ligand, but none have been reported for ruthenium. The ion [0s(0)2(CN)4] can be prepared by reaction of [OSO4] with aqueous KCN. The X-ray crystal structure of Cs2[Os(0)2(CN)4] (85) shows that it has trans-6ioxo groups with 0s=0 distances of 1.750 [0s(0)2(CN)4] is luminescent both in the solid state... 

An unusual osmium(Vl) monooxo species stabilized by amido ligands, [Os (0)(tmen-2H)(tmen-H)]" ", has been prepared by treatment of [0s (0)2(tmen)2] " (97b) with a base such as collidine in acetonitrile." The crystal structure of the perchlorate salt has been determined the osmium atom is displaced 0.67 A from the plane of the four N atoms. The Os=0 distance is 1.72 A, and the Os—N distances of 1.85 A and 1.99 A indicate double bond character. 

A number of /.t-oxo-osmium(IV) porphyrin complexes have been prepared by aerial oxidation of [Os OEP)(CO)(MeOH)] in the presence 2,3-dimethylindole in CH2Cl2. " Cyclic voltammetric studies show that [0s2(0)(0EP)2(0Me)2] can undergo reduction to give an Os —O—Os dimer. The X-ray crystal structure of [0s(0EP)(0Me)]2( -0) shows a linear Os—O—Os backbone with Os—O and Os—OCH3 distances of 1.808 A and 1.997 A, respectively. 

Alkylations, osmium(ll), 37 348 Alkyl azides, UV spectra, 26 178 Alkylbarium halides, solvated, 11 390 Alkylbery Ilium alkoxides, 11 395 alkylperoxides, 11 395 amides, 11 401 03 anions, 11 369-370 crystal structure of, 11 369 halides, solvated, 11 389 hydrides, 11 371-373 B-Alkylborolane, 16 241... 

Diol complexes, 9 211 d ion complexes, heavier, structure changes prior to ligand exchange, 34 258-259 Diopside, 4 61 crystal structure of, 4 51 p-Dioxane complexes, osmium, 37 312... 

Reaction of (-)-a-pinene (1) with stoich. RuO /CCl gave a ketoaldehyde (2), probably via a Ru(VI) diester (4). If the reaction is performed using RuO in acetone rather than CCl, the a-ketol (3) is the main product. It is likely that a Ru(VI) diester (4) is involved such a species was isolated and both H and NMR data suggest the structure shown in (Fig. 3.8). An X-ray crystal structure determination was carried out on the osmium analogue of (4) [178]. 

In the solid state, the equilibrium is in favor of the hydrido complex (III), and its crystal structure and that of the osmium(II) analog have been determined (38). Chatt also observed that, on heating the equilibrium mixture of (II) and (III), naphthalene was eliminated and the product Ru(dmpe)2 was also a tautomeric mixture. Here the tautomer-ism involves breaking and re-formation of carbon-hydrogen bonds in the methyl groups of the phosphine ligands (IV and V) ... 

Ruthenium and osmium have hep crystal structures. These metals have properties similar to the refractory metals, ie, they are hard, britde, and have relatively poor oxidation resistance (see Refractories). Platinum and palladium have fee structures and properties akin to gold, ie, they are soft, ductile, and have excellent resistance to oxidation and high temperature corrosion. 

The Criegee mechanism originally proposed involves the formation of an osmium(VI)-ester complex (106) from the [4+2] cycloaddition of the Osvul cis-dioxo moiety with an alkene, followed by the hydrolysis or reduction of (106) to cis-glycol and reduced osmium species. In support of this mechanism a variety of Osvl cyclic esters such as (107) or (108) (L = quinuclidine) have recently been synthesized from Os04 and the alkene, and characterized by an X-ray crystal structure.290,343 In solution the dimeric complex (108) dissociates to give the monomeric dioxo trigonal-bipyramidal complex (109), which is similar to (106).344... 

The X-ray crystal structure of [cis-l,2-ethanediaminebis(l,2-ethanediaminato(l-)]osmium(IV) dibromide has been determined (100). The short Os—N(aminate) bonds (1.90 A) are attributed to the bonding interaction between the filled pn orbitals of the ligands and the empty d orbitals on Os(IV). 

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