872371-77-2Relevant academic research and scientific papers
Synthesis, structure, and reactivity of four-, five-, and six-coordinate ruthenium carbyne complexes
Caskey, Stephen R.,Stewart, Michael H.,Yi, Joon Ahn,Johnson, Marc J. A.,Rowsell, Jesse L. C.,Kampf, Jeff W.
, p. 1912 - 1923 (2008/10/09)
Square-planar carbyne complexes of the form Ru(≡CR)(PCy 3)2X (X = F, Cl, Br, I, O3SCF3) are prepared by net dehydrohalogenation of the Grubbs catalysts Ru(≡CHR) (PCy3)2Cl2 followed by substitution of the chloride ligand (when X ≠ Cl). The dehydrohalogenation can be effected in one step (R = n-Bu, Ph, p-C6H4Me) by Ge(CH[SiMe 3]2)2 or in two steps via treatment with excess aryloxide such as NaO-p-C6H4-t-Bu followed by SnCl 2. The latter route gives greater yields but is more restricted in scope. Addition of HCl (1 equiv) to Ru(=CR)(PCy3)2X (X = Cl, Br, I) affords Ru(=CHR)(PCy3)2ClX; those with mixed halide ligand sets undergo rapid halide exchange in solution. Upon treatment with the appropriate oxidant, each Ru(=C-p-C6H4Me) (PCy3)2X complex undergoes two-electron oxidation. Oxidation of Ru(=C-p-C6H4Me)(PCy3)2X (X = F, Cl, Br, I) by XeF2, C2Cl6, Br 2, and, respectively, yields either six-coordinate bis-phosphine complexes Ru(=C-p-C6H4Me)(PCy3) 2X3 (X = F, Cl) or square-pyramidal mono-phosphine complexes Ru(≡C-p-C6H4Me)(PCy3)X 3 (X = Br, I) depending on the size of the halide ligands. Cationic square-pyramidal complexes of the form [Ru(=C-p-C6H 4Me)(PCy3)2X2]+ (X = Cl, I) can be prepared from Ru(≡C-p-C6H4Me)(PCy 3)2Cl3 by chloride abstraction using [Ph 3C]BF4 and from Ru(≡C-p-C6H 4-Me)(PCy3)X3 by addition of PCy3. Hydride addition to Ru(≡C-p-C6H4Me)(PCy 3)2Cl3 yields the carbene complex Ru(=CHR)(PCy3)2Cl2, whereas fluoride addition affords the carbyne complex Ru(≡C-p-C6H4-Me(PCy 3)2Cl2F, results with important implications for metathesis of vinyl fluorides. X-ray structures of Ru(≡C-p-C 6H4Me)(PCy3)2X2F (X = F, Cl), [Ru(≡C-p-C6H4Me)PCy3) 2Cl2]BF4, and Ru(≡C-p-C6H 4-Me)(PCy3)I3 reveal short Ru≡C bonds in the 1.670(5)-1.714(3) A range; when two PCy3 ligands are present, they are mutually trans. The benzylidyne ligands occupy the apical sites in the two square-pyramidal complexes. Of the five- and six-coordinate complexes, only the two fluoride-containing complexes Ru(≡C-p-C 6H4Me)(PCy3)2X2F (X = F, Cl) display reactivity toward alkynes, serving as alkyne dimerization catalysts.
Dehydrohalogenation by a germylene: Conversion of carbene ligands into carbynes at ruthenium
Caskey, Stephen R.,Stewart, Michael H.,Ahn, Yi Joon,Johnson, Marc J.A.,Kampf, Jeff W.
, p. 6074 - 6076 (2008/10/09)
The dialkylgermylene [Ge(CH[SiMe3]2)2] (3) converts the carbene complexes [Ru(CHR)(PCy3)2Cl 2] (R = p-C6H4Me [2], n-C4H 9 [6]) into the corresponding square-planar carbyne complexes [Ru(CR)(PCy3)2Cl] (R = p-C6H4Me [1], n-C4H9 [7]) cleanly within minutes at 25°C in benzene; addition of HCl to a benzene solution of 1 results in quantitative re-formation of 2. Replacement of chloride in 1 affords other halide and pseudohalide complexes, [Ru[C-p-C6H4Me)(PCy 3)2X] (X = p-OC6H4-t-Bu, Br, F, O3SCF3), cleanly.
