Ruthenium Catalyzed Homocoupling of Terminal Alkynes

Abstract

Several complexes of the type RuTp(L)(L H )Cl (L, L H P, N, O donors) were tested with respect to their ability of promoting catalytic C±C-coupling reactions of terminal acetylenes. When L tertiary phosphine, predominantly dimerization occurs, RuTp(PPh 3 ) 2 H being the most ef®cient pre-catalyst. In the absence of a phosphine ligand, polymerization takes place with RuTp(COD)Cl as the most effective pre-catalyst. Both product distribution and conversion depend strongly on the substituent of the alkyne and to a lesser extent on the co-ligands of the ruthenium complex. The catalytically active species is the 16e À alkynyl complex RuTp(L)(±C:C±R) which in case of L PCy 3 and R Bu n could be trapped as RuTp(PCy 3 )(±C:CBu n )(CO).

Dimerization of terminal alkynes catalyzed by chloro(η5-pentadienyl) bis(triphenylphosphine)ruthenium(II) and kinetics of phosphine substitution

“…Lesser amounts are seen in the presence of (g 5 -C 9 H 7 )Ru-(PPh 3 ) 2 H [15]. The polymerization of terminal alkynes is also observed in the presence of TpRu(COD)Cl [19]. The COD ligand in both (g 5 -indenyl)Ru(COD)Cl and TpRu-(COD)Cl is very labile and may be responsible for opening two coordination sites at ruthenium upon dissociation and polymerization.…”

Addition of Acetylenes to Olefins. Oxidative Coupling versus [2+2] Cycloaddition to a Vinylidene Intermediate

“…Complex 1 adopts the usual three-legged piano stool structure. The olefin moiety of the Ph 2 PCH 2 CH 2 CHdCH 2 ligand is bonded almost symmetrically to the metal center, with the Ru-C bonds to the internal and terminal carbon atoms C(20) and C(21) being 2.250 (6) and 2.217(7) Å, respectively. The CdC double bond is almost perpendicular to the Ru-N bond.…”

“…However, NMR monitoring of the progress of this reaction indicated complete consumption of 1 after 1 h, giving 2a and 2b in 3.3:1.0 ratio, with no evidence found for the formation of 2c but small amounts of polymeric materials (Table 1). 6 The coupling reaction turned out to be not restricted to terminal alkynes. Thus, in similar fashion, 1 was found to react with 1.5 equiv of internal alkynes R 1 Ct CR 2 (R 1 ) R 2 ) Ph, Et; R 1 ) Ph, R 2 ) Et) to give the η 4 -butadiene complexes [RuCp(κ 1 (P),η 4 -(3Z,5Z)-PPh 2 -CH 2 CH 2 CHdCH-CPhdCHPh)]PF 6 (3), [RuCp(κ 1 (P),η 4 -(3Z,5E)-PPh 2 CH 2 CH 2 CHdCH-CEtdCHEt)]PF 6 (4), and 5 (in the form of the two regioisomers [RuCp(κ 1 (P),η 4 -(3Z,5E)-PPh 2 CH 2 CH 2 CHdCH-CEtdCHPh)]PF 6 (5a) and [RuCp(κ 1 (P),η 4 -(3Z,5Z)-PPh 2 CH 2 CH 2 CHdCH-CPhd CHEt)]PF 6 (5b)) in high yields (Table 1).…”

“…(i) In the absence of base, the reaction of 1 with DCtCPh gives complexes 2a D and 2b D , where the deuterium is attached at C 5 and C, 6 respectively, and anti to the metal center. This implies that the syn hydrogen originates exclusively and in all cases from the olefin.…”

Reactions of ruthenium(II) tris(pyrazolyl)borate and tris(pyrazolyl)methane complexes with diphenylvinylphosphine and 3,4-dimethyl-1-phenylphosphole

“…There have been several ruthenium tris(pyrazolyl)borate vinylidene complexes reported such as (Tp)Ru(PPh 3 )Cl( Ä/C Ä/ CPhH) [30,53], [(Tp)Ru(PPh 3 ) 2 (Ä/C Ä/CHR)] ' [26,54], [55] (dippe 0/( i Pr) 2 PCH 2 CH 2 P( i Pr) 2 ). Many of the TpRu Á/vinylidene complexes are used for the dimerization of terminal alkynes to form enynes [26,30,34,35]. We attempted the syntheses of vinylidene complexes by reacting complexes 10, 11 and 13 with phenylacetylene under a variety of conditions but in each case only starting materials were obtained.…”