Ruthenium geometries

Thermal arene exchange of tetramethylthiophene with [(/ -cymene)RuCl2]2 affords 130 (89JA8828), which on reaction with AgBE4 and excess tetramethylthiophene yields 131. The Ru—S thiophenic cluster, 132, was synthesized by reaction of 130 with (Mc3Si)2S followed by anionic metathesis and formation of the PFg salt. The coordination geometry around each ruthenium atom is pseudooctahedral. 

The virtual identity of the Ru-N bonds and coordination geometries in the ruthenium(II and III) complexes is noteworthy and accounts for the... 

The second complex has been characterized by X-ray crystallography223. The ruthenium(II) atom is coordinated to three Me2SO molecules via the oxygen atom and to three via the sulphur atom to give the irregular octahedral geometry as shown in Scheme 18. 

The complex 65 was synthesized by reaction of the imidazolinium salt with the precursor ruthenium complex 67 (catalytically inactive) in the presence of silver carbonate (Scheme 42). The complex being air-stable and stable on silicagel was isolated in 52% yield after chromatography. The diastereomeric and enantiomeric purity of 65 was determined by HPLC analysis and found to be above 98% (de and ee). The molecular structure was determined by X-ray analysis and showed the unusual twist geometry of this complex. 

The precursor of ° Ru is ° Rh (tip, = 3 years). It is prepared by irradiating natural ruthenium metal with 20 MeV deuterons, " Ru (d, n) Rh. The target is then allowed to decay for several months to diminish the accompanying Rh activity. In a report on ° Ru Mossbauer spectroscopy [111], the authors reported on spectra of Ru metal, RuOa, and [Ru(NH3)4(HS03)2] at liquid helium temperature in standard transmission geometry using a Ge(Li) diode to detect the 127 keV y-rays. The absorber samples contained 1 g of ruthenium per cm. ... 

General Structural Features. The general structure of halfsandwich ruthenium(II)-arene complexes is shown in Fig. 12. The structural, stereochemical and electronic features of metal-arene complexes have been discussed (63). A typical piano-stool geometry consists of an rj6-arene occupying three coordination sites of the pseudo-octahedral complex, leaving the three legs X, Y, and Z available for coordination. The sites X and Y can be taken up by two monodentate ligands, but are more commonly... 

The idea of determining the site of initiation via the substitution pattern of the olefin has also been used by Blechert et al. during the course of a stereocon-trolled RCM process (Scheme 10). Again, the reaction starts most likely at the terminal olefin site in 33 independent of whether 1 or 24 is used as catalyst however, due to the different coordination geometries of ruthenium and molybdenum, the evolving carbene reacts with either diastereotopic olefin attached to... 

The tetraene precursor 14, assembled in a similar way to 11, underwent smooth cyclization using the ruthenium initiator 3 (0.1 equiv) to give macrolactone 15, again in good yield and with complete E-selectivity. Despite the incorrect olefin geometry, transformation into epoxides 16 provided further encour-... 

Another example of a ruthenium-catalyzed reaction appeared in 1996 for the dimerization of PhCH2C=CH (193) [136]. The catalyst used for the reaction was Cp RuH3(PCy3) and the butatriene 194 was obtained as a single isomer in 93% yield with >95% selectivity however, the geometry of 194 could not be determined unambiguously (Scheme 3.95). 

Whereas d ruthenium complexes add protic nucleophiles to the C3=C4 of the butatrienylidene ligand to give alkenylallenylidene complexes (see Scheme 3.22), iridium complex 11 adds trifluoroacetic add to the C2=C3 bond to form an alkenylvinylidene complex [2, 3]. The corresponding reaction of 11 with two equivalents of HCl yields, presumably again via an alkenylvinylidene complex, a five-coordinate alkenyl(dichloro) complex with a trigonal-bipyramidal coordination geometry (Scheme 3.29) [3]. 

One of the most studied ligand-metal complexes is the bis(oxazoline)-ruthe-nium(ll) complex.Kurasowa and co-workers proposed that the aqua and amine complexes of bis(oxazoline)-ruthenium(ll) 17a-d also adopt a tetrahedral geometry about the metal center. These are only a few of many examples of the complexes formed between a variety of transition metals and bis(oxazoline) ligands that have been studied. ... 

Various X-ray crystal structures of metal-ligand complexes provided evidence of the geometry of the complexes in the solid state, even though the structure of these complexes may differ in solution. The hrst crystal structure of a bis(oxazoline)-metal complex was determined in 1994 by Brown and co-workers. " This group crystallized and elucidated the structure of V,V-bis-[2-((45)-(methyl)-l,3-oxazoli-nyl)]methane-bi(ri ethene)rhodium(I), 18a, as depicted in Figure 9.3. The key features of this crystal structure include the C2-axis of symmetry, the axial positions of the methyl groups and the orientation of the ethene molecules, orthogonal to the complexation square plane. In 1995, Woodward and co-workers were able to crystallize and determine the structure of benzylbis(oxazoline) with ruthenium... 

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