-and suprafacial rearrangements in solution I Unsymmetrical q3-benzyl-to-metal bonding in the solid state / Rhodium, q'-benzyl(carbony1) compound / Rhodium, monomeric square-planar q2-carboxylato complexes / q3-Allyl(q I-carboxy1ato)hydridometal intermediates, formation by oxidative addition q3-Allyl and q3-Benzyl Rhodium Complexes: Synthesis, Structure Dynamic, and Reactions with Carboxylic AcidsThe (q3-ally1)rhodium complexes [Rh(q3-2-RC3H4)(PiPr3),] (3-5) have been prepared in 70-90% yield from the in situ generated chlororhodium precursor [RhCl(PiPr,),] (2) and 2-RC,H,MgX. On a similar route, the corresponding ethene-(phosphane) derivative [Rh(i13-2-MeC3H4)(C2H4)(PiPr3)] (9) has been obtained. Compound 9 smoothly reacts with PiPr3 and PMe, to give 4 (R = Me) and [Rh(q3-2-MeC3H4)(PMe3)-(PiPr,)] (lO), respectively. In contrast to the q3-allyl complexes which are configurationally stable, the q3-benzyl analogues [Rh(i13-CH2C6H4R)(PiPr3),] (11, 12), prepared from 2 and 4-RC6H4CH2MgC1, are highly fluctional in solution. At room temperature, an antarafacial (71-0-71) as well as a suprafacial rearrangement occurs, the first one of which is frozen out at 263 K. On cooling to 193 K, the faster process (equally designated as a metallotropic shift) is also slowed down, and the rigid structure of 11 and 12 is observed. The AG* values for the antara and suprafacial rearrangements of 11 and 12 which have been determined from the 'H-and ,lP-NMR spectra at variable temperature are 60.0 ? 1.5 and 39.5 ? 1.0 kJ/mol, respectively. The q3-benzyl compound 11 reacts even at -78°C with CO to give the monocarbonylrhodium(1) complex trans-[Rh(q '-CH2C6H,) (CO) (PiPr3),] (13). Treatment of 3,4, or 11 with RC0,H (R = CF3, CH3, C6H5, C6H4-4-OMe, C6H4-4-N02) affords the monomeric q2-carboxylatorhodium (1)

No abstract

The transformation of a methoxy or methylamino group into a carbene ligand is possible if it is part of a phosphane. Complexes 1 and 2 can be prepared from the efficient one‐pot reaction of OsCl3 · 3H2O or [OsCl2(PPh3)3] and the phosphanes iPr2PCH2CH2Y (Y = OMe or NMe2). The reaction with the phosphane iPr2PCH2CO2Me provides an osmium(II) complex which reacts with phenylacetylene to furnish the vinylidene complex 3 in quantitative yield.

No abstract

Die Umwandlung einer Methoxy‐oder Methylamino‐Gruppe in einen Carben‐Liganden gelingt, wenn diese Teil eines Phosphans sind, So lassen sich in einer ergiebigen Eintopfsynthese die Komplex 1 und 2 aus OsCl3 · 3H2O bzw.[OsCl2(PPh3)3] und den phosphanen iPr2PCH2CH2Y (YOMe bzw. NMe2)herstellen. Mit dem Phosphan iPr2PCH2CO2Me kann ein Osmium(II)‐Komplex isoliert werden, der mit Phenylacetylen quantitativ zum Vinylidenkomplex 3 reagiert.