(2 e ) and [ Rh( C=CCH20Me) (HgPh) C1( PiPr3) (6d) have been determined.Currently, there is much interest in the chemistry of vinylidene transition-metal complexes[*], which are key species in the transformation of two-carbon ligands and play an important role in organometallic as well as in organic synthesisL31. After we had discovered that not only terminal alkynes H C 4 R but also trimethylsilyl and triphenylsilyl derivatives, RC=CSiMe3 and RC=CSiPh3, can be converted in the coordination sphere of rhodium to the corresponding vinylidenes :C=C(R)SiR'3[41, we set out to investigate whether a similar rearrangement proceeds with stannyl-substituted acetylenes, too. We expected that due to the decrease in bond strength along the series C-Si > C-Ge > C-Sn['] a 1,2-SnR3 shift should be less activated than a 1,2-SiR3 shift. However, due to the reduced bond strength and the higher electrophilicity of tetravalent tin, an increased tendency to undergo side reactions was also expected. In this context, we note that Lewis et a1.L61 have recently shown that mono-, oligo-, and polymeric alkynylrhodium(II1) complexes are obtained on treatment of [Rh(PMe3)4]C1 with SnR3-substituted alkynes, one of the driving forces in these processes being the formation of R3SnCl.In the present paper we report that with [RhC1(PiPr3)z], (1) and RC=CSnPh3 as starting materials square-planar vinylidenerhodium(1) complexes bearing a SnPh3 group at the P-carbon atom of the vinylidene ligand can be prepared. They readily react not only with proton sources by C-Sn bond cleavage but also with PhHgCl to give a novel type of Rh-Hg dimetallic products.
Vinylidenerhodium Complexes from RC=CSnPh3Since we had found that trimethylsilyl-substituted alkynes are more reactive toward 1 than the SiPh3-substituted we began our studies with alkynes RC=CSnMe3 (R = H, tBu, Ph, C02Me) as substrates. However all attempts to coordinate these alkynes to the [RhC1(PiPr3 A clean reaction occurs by adding triphenylstannyl-substituted alkynes RC=CSnPh3 (R = H, Me, Ph) to a solution of 1 in THF at -50 to -78°C. After slow warming to room temperature, red to violet microcrystalline solids are isolated which according to the spectroscopic data are not the alkyne but the isomeric vinylidene complexes 2a-c. Diagnostic, in particular[2a], are the two signals at low field in the I3C-NMR spectra in the range of 6 = 270-290 and 80-110 which are both split into doublets of triplets due to Rh-C and P-C coupling. The absence of a C=C stretching frequency in the IR spectra at about 1800-1850 cm-' further supports the proposed coordination of a vinylidene instead of an alkyne ligand.[RhC1(PiPrJz], 1
This paper treats the stability of two superposed gravitating streams rotating about the axis transverse to the horizontal magnetic field. The critical wave number for instability is found to be affected by rotation for propagation perpendicular to the axis about which the system rotates. The critical wave number for instability is not affected by rotation when waves propagate along the axis of rotation. The critical wave number is affected by both the magnetic field and the streaming velocity in both cases. Both the magnetic field and the rotation are stabilizing, while the streaming velocity is destabilizing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.