1346267-01-3Relevant academic research and scientific papers
Platinum allenylidene complexes and formation of platinum and palladium acetonitrile alkynyl complexes
Kessler, Florian,Wuttke, Evelyn,Lehr, Daniela,Wang, Yan,Weibert, Bernhard,Fischer, Helmut
experimental part, p. 278 - 287 (2011/09/15)
The platinum(0) complex [Pt(PPh3)4] reacts with brominated propargylic amides and esters in benzene by oxidative addition to give trans-[Br(PPh3)2Pt-C≡C-C(O)R] complexes whereas no reaction occurs when halogenated solvents (CH2Cl2, CHCl3) are used. The cis-ligands PPh3 can be replaced by P(iPr)3 and the bromide by trifluoroacetate. O-Alkylation of those trans-[X(PR′3)2Pt-C≡C-C(O)R] complexes (X = Br, CF3COO; R′ = Ph, iPr) derived from propargylic amides with MeOTf or [Me3O]BF4 in CH 2Cl2 gives the first cationic monoallenylidene complexes of platinum, trans-[X(PR′3)2PtC≡CC(OMe)NR 2]+Y- (Y = OTf, BF4). In contrast, trans-[Br(PPh3)2Pt-C≡C-C(O)OMenthyl] derived from a propargylic ester does not react with MeOTf in CH2Cl2. However, in acetonitrile instead of O-methylation the substitution of acetonitrile for the bromide ligand to yield the cationic acetonitrile alkynyl platinum complex trans-[MeCN(PPh3)2Pt-C≡C-C(O) OMenthyl]+OTf- is observed. The related palladium complexes trans-[X(PR′3)2Pd-C≡C-C(O)OR] (X = Br, CF3COO; R′ = Ph, iPr, R = menthyl, Et) react with MeOTf or [Et3O]BF4 analogously affording trans-[MeCN(PR′3)2Pd-C≡C-C(O)OR] +Y- (Y = OTf, BF4).
Palladium alkynyl and allenylidene complexes: Very efficient precatalysts for C-C coupling reactions
Wuttke, Evelyn,Naegele, Bettina,Weibert, Bernhard,Kessler, Florian
experimental part, p. 6270 - 6282 (2012/01/04)
Oxidative addition of BrC≡CC(=O)O-menthyl (1a) to [Pd(PPh 3)4] affords the alkynyl complex trans-[Br(PPh 3)2Pd-C≡CC(=O)O-menthyl] (2a). Subsequent reaction of 2a with trifluoroacetate gives trans-[(F3CCOO)(PPh 3)2Pd-C≡CC(=O)O-menthyl] (3a). Reaction of trans-[Br(PPh3)2Pd-C≡CC(=O)NC4H 8] (2b) with 10 equiv of NaI gives trans-[I(PPh3) 2Pd-C≡CC(=O)NC4H8] (4b). The efficiency of the new palladium complexes 3a and 4b as precatalysts is compared with that of recently published cationic palladium allenylidene complexes in C-C coupling reactions. Further trans-bis(alkynyl)palladium complexes, trans-[(PEt 3)2Pd(-C≡CC{=O}NR2)2] (NR 2 = N(CH2)4 (9b), NMe2 (9c), N(CH2)4O (9d), N(CH2)5 (9e)), trans-[(PiPr3)2Pd(-C≡CC{=O}NMe 2)2] (11c), and trans-[(PPh3) 2Pd(-C≡CC{=O}NR2)2] (NR2 = N(CH2)4 (13b), NMe2 (13c), N(CH 2)4O (13d)), were synthesized by treating HC≡CC(=O)NR2 with AgNO3 followed by transmetalation of the alkynyl ligand from silver to [PdCl2(PEt3) 2], [PdCl2(PiPr3)2], or [PdCl2(PPh3)2], respectively. Methylation of complexes 9b-e with MeOTf yields dicationic bis(allenylidene) complexes of palladium, trans-[(PEt3)2Pd{=C=C=C(OMe)NR 2}2]2+(OTf)-2 (NR 2 = N(CH2)4 (10b-OTf), NMe2 (10c-OTf), N(CH2)4O (10d-OTf), N(CH2) 5 (10e-OTf). Alkylation of complex 9e with [Me3O]BF 4 or [Et3O]BF4 gave trans-[(PEt 3)2Pd{=C=C=C(OR)N(CH2)5} 2]2+(BF4)-2 (R = Me (10e-BF4), Et (10e′-BF4)). Complexes 11c and 13b-d were methylated accordingly to obtain the corresponding bis(allenylidene) complexes 12c-OTf, 12c-BF4, 14b-OTf, 14c-OTf, and 14d-OTf. The catalytic activities of the new bis(alkynyl) and bis(allenylidene) complexes were investigated and compared with those of the mono(alkynyl) and mono(allenylidene) complexes. The palladium alkynyl and allenylidene complexes are both found to be very efficient precatalysts for Heck, Suzuki, and Sonogashira reactions. Even aryl chlorides were efficiently coupled in Heck and Suzuki reactions when complex 9e was used as precatalyst. Powder diffraction, TEM, and DLS measurements indicate that palladium nanoparticles are not formed during catalysis in the Heck reaction.
