Pseudo-piano-stool

An X-ray structure determination was carried out on (C5Me5)RuBr2(Jt-C3H5), and showed a pseudo-piano-stool structure with two Br atoms and two terminal carbons for the endo-Jt-allyl ligand located at the basal positions. A crystal mirror plane bisects the pentamethylcyclopentadienyl and jt-allyl ligands. The oxidative addition of allylic halides to (C5R5)Ru(CO)2X is reversible, since the reductive elimination of... 

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 molecular structure of 9d (Fig. 3) reveals a pseudo-tetragonal pyramidal piano stool arrangement of the ligands at the central tungsten atom with the cyclopentadienyl ligand in the... 

The solid-state IR spectrum of Cp OsH5 features three Os-H stretching bands 2214 (weak), 2083 (strong), and 2065 (shoulder) cm whereas the Raman spectrum contains vqs-h bands at 2214 (polarized) and 2096 cm The IR spectrum resembles that calculated for the observed pseudo-octahedral structure of pseudo-Q symmetry (under point mass approximation for the Cp ring), but is rather different from that predicted for a five-legged piano stool geometry of symmetry. 

The interest in different ligand combinations on a metal center is due to the multiple reactive coordination sites offering multiple reactive positions at the neutral electrophilic metal center on a pseudo bent metallocene coordination sphere. The structure of the borohydride complex (COT)U(BH4)2(OPPh3) (Baudry et al. 1990a) consists of discrete molecules with a piano stool configuration, it is the first to be determined for a mono-COT U derivative. Mixed ligand Th derivatives can be obtained by the reaction... 

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