Osmium octahedral complexes

Dahl (175). The basic structure is defined by an octahedral core with trans-tellurium atoms and is isoelectronic with the ruthenium complex 183. Both clusters may also be compared with the ruthenium and osmium bismuth complexes, 125 and 129, which, although octahedral, contain two less electrons. A complex containing an additional carbonyl group, viz. [Te2Co4(CO)u], 185, has been described by Rauchfuss (172) as resulting from the reaction... 

Bursten BE (1982) Ligand additivity applications to the electrochemistry and photoelectron spectroscopy of d octahedral complexes. J Am Chem Soc 104 1299-1304 Birtje K (1987) Neue bindungsisomere Thiocyanato-und Selenocyanatokomplexe des drei-und vierwertigen Osmiums. Ph.D. thesis, Kiel University... 

The trigonal bipyramidal osmium carbyne complex 115 adds HCl across the metal-carbon triple bond to give the octahedral carbene complex 116 [Eq. (101)] (56). Protonation of 115 with aqueous HCIO4 gives the cationic... 

Reaction of (NH4)20sCl6 with EPhj (E = P or As) allows isolation of trans-OsCl4(EPh3)2. A paramagnetic, octahedral osmium(iv) complex of 3,3 -diamino-4,4 -dihydroxydiphenyl-sulphone has been prepared.The thermal decomposition of Os(phthalocyanine)S04 has been studied. 

Ruthenium(III) and osmium(III) complexes are all octahedral and low-spin with 1 unpaired electron. Iron(III) complexes, on the other hand, may be high or low spin, and even though an octahedral stereochemistry is the most common, a number of other geometries are also found. In other respects, however there is a gradation down the triad, with Ru occupying an intermediate position between Fe and Os . For iron the oxidation state +3 is one of its two most common and for it there is an extensive, simple, cationic chemistry (though the aquo... 

A range of five- and six-coordinate osmium boryl complexes has been synthesized making use of similar approaches to those reported above for ruthenium. In particular, the reaction of phenylosmium(II) precursors with boranes, which proceed via elimination of benzene, has been shown to be a useful entry point into octahedral and square pyramidal osmium boryl complexes. Significant further chemistry has been reported on these systems, including substitution at both boron and metal centres, which has shed light on fundamental issues of structure/bonding and reactivity [12]. 

All four halide ions from octahedral complexes with the metal. Fluorides or fluoro complexes are known for osmium(VII) to osmium(IV) inclusive, with rather tenuous evidence for OsFj OsF is a rare example of seven coordination for the metal. The other halides prefer the IV and III states, though osmium(V) chloride and chloro complexes have recently been made and also [OsBr ]". Although [RuFs] " is well known there is no osmium analogue, in keeping with the general tendency of third-row elements to display higher oxidation states than their second-row partners. 

Gut. D. Rudi, A. Kopilov, J. Goldberg. I. Kol. M. Pairing of propellers Dimerization of octahedral ruthe-nium(II) and osmium(II) complexes of eilatin via n-n stacking featuring heterochiral recognition. J. Am. Chem. 

Only one osmium complex of this type is known. The osmium(II) complex [Os2Cl3(PPh2Et)fi]Cl, containing three bridging chlorine atoms, is reported to react with cycloocta-1,5-diene to give presumably octahedral ir-CgH,208(PPh2Et)2Cl2 (24). 

The formal similarity of these ruthenium and osmium compounds to the octahedral Group VI carbyne compounds would lead to an expectation of reactivity towards nucleophiles. In fact the neutral octahedral complexes prove to be rather unreactive compounds but the cationic complexes do react with nucleophiles. Mention has already been made of the hydrolysis of [Ru(=CPh)ClI(CO)(PPh3)2]I to RuPhCl(CO)2g Ph3)2. A very clear-cut example is provided by the reaction of [0s(sCR)Cl2(CNR )(PPh3)2]C104 (R=p-dimethylaminophenyl, R =p-tolyl) with NaSH. 

For trinuclear cluster complexes, open (chain) or closed (cycHc) stmctures are possible. Which cluster depends for the most part on the number of valence electrons, 50 in the former and 48 in the latter. The 48-valence electron complex Os2(CO)22 is observed in the cycHc stmcture (7). The molecule possesses a triangular arrangement of osmium atoms with four terminal CO ligands coordinated in a i j -octahedral array about each osmium atom. The molecule Ru (00) 2 is also cycHc and is isomorphous with the osmium analogue. 

The most important members of this class are the osmium nitrido, and the osmyl complexes. The reddish-purple K2[OsNCl5] mentioned above is the result of reducing the osmiamate. The anion has a distorted octahedral structure with a formal triple bond Os=N (161pm) and a pronounced /ram-influence (pp. 1163-4), i.e. the Os-Cl distance trans to Os-N is much longer than the Os-Cl distances cis to Os-N (261 and 236 pm respectively). The anion [OsNCls] also shows a rram-effect in that the Cl opposite the N is more labile than the others, leading, for instance, to the formation of [Os NCl4] , which has a square-pyramidal structure with the N occupying the apical position. 

There is a wide range of diketonates, such as Ru(acac)3, with octahedral coordination [133b] (they do not seem, however, to be oxidized to the +4 state this is possible with osmium) similarly several salts of the tris(oxalato) complex Ru(C204)3 have been isolated. 

The pattern of behaviour in osmium nitrosyls seems to be similar to that seen with ruthenium, though fewer data are available. The most common type of complex has octahedrally coordinated osmium(II) with linear Os-N-O linkage. Some syntheses are shown in Figure 1.67. 

Coordination about the osmium in 47 is best regarded as distorted trigonal bipyramidal with axial triphenylphosphine ligands. The distortion is toward a square pyramidal geometry with an apical nitrosyl ligand. Coordination about Os in the six-coordinate phenylcarbene complex is octahedral, as expected. 

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