Tetraosmium clusters

Carbon functional groups, attachment to polysilanes, 3, 585 Carbon-heteroatom bond formation via antimony(III) compounds, 9, 428 via antimony(V) compounds, 9, 432 via bismuth(III) compounds characteristics, 9, 440 with copper catalysts, 9, 442 non-catalyzed reactions, 9, 443 with bismuth(V) compounds, 9, 450 with bismuthonium salts, 9, 449 with bismuth ylides, 9, 450 Carbon-heteroatom ligands in tetraosmium clusters, 6, 967 in tetraruthenium clusters, 6, 960... 

An early example of surface-mediated synthesis led to the conversion of Os3(CO)i2 into [Os5C(CO)i4] [13]. Quantitative characterization of the formation of this cluster on MgO by C NMR spectroscopy [15] showed that the synthesis gave [OssCCCOIm] " in a yield of about 65% other products included triosmium and tetraosmium carbonyl clusters. A schematic representation of the surface chemistry is shown in Fig. 1. 

Butterfly clusters are still not common, and, at present, few catalytic processes based on them are known. They have, however, been considered as surface analogs for Fischer-Tropsch, nitrogen fixation, and isocyanite chemistry (26, 163). There is growing evidence that small ligands such as carbide and nitride coordinated within the cavity of a butterfly framework exhibit unusual patterns of chemical reactivity. The two tetraosmium nitride isomers have also been synthesized as follows (90) ... 

This chapter covers the literature on tetraruthenium and tetraosmium organometallic compounds from 1995 until late 2005. The literature search was carried out with SciFinder Scholar. Compounds containing other transition metals have for the most part been omitted. Although not strictly cluster compounds, compounds containing a chain of four Ru or Os metal atoms are included. Also included for their intrinsic interest are tetranuclear cage compounds with two or less metal-metal bonds. 

The neutral tetraosmium carbonyl cluster [Os4(CO)is], mentioned in COMC (1995), has an unusual planar OS4 skeleton with adjacent long and short peripheral metal-metal bonds (i.e., a kite structure). The stability of this planar metallic core configuration has been confirmed by extended Hilckel calculations. ... 

The details for the synthesis of the activated tetraosmium hydrido cluster [Os4(/r-H)4(CO)io(NCMe)2] 72 have been previously reported the X-ray structure has now been determined. It consists of a tetrahedral metal core with each hydride ligand bridging the four OsOs bonds which are longer (2.915(3)-2.998(3) A) compared to the remaining two (both 2.810(3) A). The two acetonitrile ligands are coordinated to the same osmium atom (OsN = 2.02(4) and 2.07(5) A). The molecule possesses approximate symmetry. 

The reaction between the lightly stabilized tetraosmium hydrido cluster Os4( -H)4(CO)io(NCMe)2 and cyclohexa-1,3-diene affords the trigonal-bipyramidal Oss(ai-H)2(CO)i3( -C6H8) 66 together with a number of tetraosmium products. ... 

The sequential synthesis of some tetraosmium-arene clusters has been described The synthesis and X-ray crystal structure of the triosmium cluster (71) containing a carbene in an unusual coordination mode has been reported. The synthesis and X-ray crystal structure of the trisomium cluster [Os3(H-H)(CO)9(p-C(H)NC5H4-T 2-CH=CH2)] (72) has been described5i7. The synthesis of the unique linear triosmium allyl clusters [Os3Br((X))io(CNR)(Ti3-C3H5)] (R = Pr", CH2Ph) has been reported l and the product stracturaUy characterised for R = Pr . 

Higher-nuclearity Osmium Clusters. The tetraosmium linear chain cluster [Os2(CO)5(thd)2]2 (thd = 2,2-dimethyl-3,5-heptanedionate) was obtained when... 

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