Synthesis, Structure, and Reactivity of Four-, Five-, and Six-Coordinate Ruthenium Carbyne Complexes

Abstract

Square-planar carbyne complexes of the form Ru(tCR)(PCy 3 ) 2 X (X ) F, Cl, Br, I, O 3 SCF 3 ) are prepared by net dehydrohalogenation of the Grubbs catalysts Ru(dCHR)(PCy 3 ) 2 Cl 2 followed by substitution of the chloride ligand (when X * Cl). The dehydrohalogenation can be effected in one step (R ) n-Bu, Ph, p-C 6 H 4 Me) by Ge(CH[SiMe 3 ] 2 ) 2 or in two steps via treatment with excess aryloxide such as NaO-p-C 6 H 4 -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(tCR)(PCy 3 ) 2 X (X ) Cl, Br, I) affords Ru(dCHR)(PCy 3 ) 2 ClX; those with mixed halide ligand sets undergo rapid halide exchange in solution. Upon treatment with the appropriate oxidant, each Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X complex undergoes two-electron oxidation. Oxidation of Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X (X ) F, Cl, Br, I) by XeF 2 , C 2 Cl 6 , Br 2 , and I 2 , respectively, yields either six-coordinate bis-phosphine complexes Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X 3 (X ) F, Cl) or square-pyramidal mono-phosphine complexes Ru(tC-p-C 6 H 4 Me)(PCy 3 )X 3 (X ) Br, I) depending on the size of the halide ligands. Cationic square-pyramidal complexes of the form [Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X 2 ] + (X ) Cl, I) can be prepared from Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 Cl 3 by chloride abstraction using [Ph 3 C]BF 4 and from Ru(tC-p-C 6 H 4 -Me)(PCy 3 )X 3 by addition of PCy 3 . Hydride addition to Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 Cl 3 yields the carbene complex Ru(dCHR)(PCy 3 ) 2 Cl 2 , whereas fluoride addition affords the carbyne complex Ru(tC-p-C 6 H 4 -Me)(PCy 3 ) 2 Cl 2 F, results with important implications for metathesis of vinyl fluorides. X-ray structures of Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X 2 F (X ) F, Cl), [Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 Cl 2 ]BF 4 , and Ru(tC-p-C 6 H 4 -Me)(PCy 3 )I 3 reveal short RutC bonds in the 1.670(5)-1.714(3) Å range; when two PCy 3 ligands are present, they are mutually trans. The benzylidyne ligands occupy the apical sites in the two squarepyramidal complexes. Of the five-and six-coordinate complexes, only the two fluoride-containing complexes Ru(tC-p-C 6 H 4 Me)(PCy 3 ) 2 X 2 F (X ) F, Cl) display reactivity toward alkynes, serving as alkyne dimerization catalysts.

Synthesis of ruthenium phenylindenylidene, carbyne, allenylidene and vinylmethylidene complexes from (PPh3)3−4RuCl2: A mechanistic and structural investigation

“…The Ru-Cl distances cis to the carbyne moiety are 235.90(15) pm and 240.93 (15) pm whereas the trans-Cl bond is elongated to 249.66 (17) pm. The Ru-C a distance (172.5(7) pm) is in the range of previously reported ruthenium carbyne complexes (170.3(9)-176.6(3) pm) [36,45]. The C-C distances in the C 3 -spine (C a -C b : 137.9(9) pm and C b -C c : 137.6(9) pm) are almost identical and in similar range as the literature complex.…”

“…As expected, the C 3 -spine has lost the linearity at the C b atom (Ru-C a -C b : 167.1(5)°, C a -C b -C c : 127.7(7)°). However, the angle at the C a atom also is somewhat significantly bent and smaller than any other such angle observed with ruthenium carbyne complexes (168.8(4)-179.9(7)°) [36,45]. This may come as a result of steric interference with the terminal phenyl groups.…”

A Unique Ruthenium Carbyne Complex: A Highly Thermo‐endurable Catalyst for Olefin Metathesis

“…Unlike its bisphosphine analogues, 11a and 11b ,7a the new Ru‐carbyne complex does not exist as a neutral, six‐coordinate Ru‐carbyne structure, which may be due to the large steric effect of the N‐heterocarbene preventing the coordination of the iodide ligand to the ruthenium center. The molecular structure of 11 was established by X‐ray diffraction (Figure 2).…”

“…For example, the ring‐opening metathesis polymerization (ROMP) of cyclic olefin substrates is catalyzed by a carbyne complex 8. Some of the carbyne complexes are known for catalyzing the dimerization of alkynes rather than for alkyne metathesis 7a. There is a general belief that ruthenium carbyne complexes are inert towards olefin metathesis 9.…”

Triphenylcarbenium Tetrafluoroborate

“…In the organometallic series, transformation of neutral η n haptic complexes of transition metals to η n+1 cationic complexes was achieved by abstraction of alkoxides 72 or halides. 73 Reaction with Small-sized Rings. Epoxides were opened for the formation of polyethylene glycol derivatives.…”