Platinum allenylidene complexes and formation of platinum and palladium acetonitrile alkynyl complexes

Kessler, Florian; Wuttke, Evelyn; Lehr, Daniela; Wang, Yan; Weibert, Bernhard; Fischer, Helmut

doi:10.1016/j.ica.2011.02.074

Cited by 7 publications

(3 citation statements)

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“…Transition-metal vinylidene complexes have been invoked in a number of gold-catalyzed reactions of terminal alkynes (Scheme ) . To date, no gold vinylidene complexes have been directly observed, although a gold(I) complex with a related allenylidene ligand has been reported, as have other group 10 and group 11 species. In these cases the allenylidene ligand is supported by strong π-donor substituents and may be better described as a substituted propargyl cation …”

Section: Introductionmentioning

confidence: 99%

Computational Discovery of Stable Transition-Metal Vinylidene Complexes

et al. 2014

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Experimental results have long suggested that catalyst optimization is an inherently multivariate process, requiring the screening of reaction conditions (temperature, pressure, solvents, precursors, etc.), catalyst structure (metal and ligands), and substrate scope. With a view to demonstrating the feasibility and utility of multivariate computational screening of organometallic catalysts, we have investigated the structural and electronic properties of a library of transition-metal-coordinated alkyne and vinylidene tautomers in different coordination environments. By varying the substituents on the organic moiety of 60 alkyne/vinylidene pairs we were able to capture and quantify the key structural and electronic effects on tautomer preference. For a carefully selected subset of substituents, the effects of metal and ancillary ligands were then explored. We have been able to formulate a protocol for assessing the stabilization of vinylidenes in transition-metal complexes, suggesting that the d 6 square-based-pyramidal metal fragment [RuCl 2 (PR 2 3 )(CCHR 1 )], combined with electron-withdrawing substituents R 1 and electron-rich groups R 2 , would provide the ideal conditions favoring the vinylidene form thermodynamically.

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Section: Introductionmentioning

confidence: 99%

Computational Discovery of Stable Transition-Metal Vinylidene Complexes

et al. 2014

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“…In all three complexes the Pd–C3 chain is slightly bent: Pd–C1–C2 = 174.69(12) ( 9e ), 176.30(19) ( 11c ), 176.1(2)° ( 10e′-BF 4 ) and C1–C2–C3 = 177.30(15) ( 9e ), 177.7(2) ( 11c ), 171.6(2)° ( 10e′-BF 4 ). However, a modest deviation from linearity of the MCCC fragment in allenylidene complexes is often observed . The Pd–C and C1–C2 distances in the dicationic allenylidene complex 10e′-BF 4 (1.986(2) and 1.209(3) Å) compare well with the bond lengths in the corresponding alkynyl complex 9e (1.9990(16) and 1.208(2) Å).…”

Section: Resultsmentioning

confidence: 88%

“…The synthesis of the first allenylidene complexes [L n MCCC(R 1 )R 2 ] was simultaneously reported in 1976 by Fischer et al (M = Cr, W) and Berke (M = Mn) . Since then allenylidene complexes of many transition metals have been prepared, including complexes of titanium, chromium, tungsten, manganese, rhenium, iron, ruthenium, osmium, rhodium, iridium, and platinum . Some of these complexes have been used as catalyst precursors: for instance, in ring-closing metathesis, in ring-opening metathesis, in dehydrogenative dimerization of tin hydrides, and in selective transetherification of substituted vinyl ethers .…”

Section: Introductionmentioning

confidence: 99%

Palladium Alkynyl and Allenylidene Complexes: Very Efficient Precatalysts for C–C Coupling Reactions

et al. 2011

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Oxidative addition of BrCCC(O)Omenthyl (1a) to [Pd(PPh 3 ) 4 ] affords the alkynyl complex trans-[Br(PPh 3 ) 2 Pd−CCC(O)O-menthyl] (2a). Subsequent reaction of 2a with trifluoroacetate gives trans-[(F 3 CCOO)(PPh 3 ) 2 Pd−CCC(O)O-menthyl] (3a). Reaction of trans-[Br(PPh 3 ) 2 Pd−CCC(O)NC 4 H 8 ] (2b) with 10 equiv of NaI gives trans-[I(PPh 3 ) 2 Pd−CCC( O)NC 4 H 8 ] (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 ) 2 Pd(−CCC{O}NR 2 ) 2 ] (NR 2 = N(CH 2 ) 4 (9b), NMe 2 (9c), N(CH 2 ) 4 O (9d), N(CH 2 ) 5 (9e)), trans -[(P i Pr 3 ) 2 Pd(−CCC{O}NMe 2 ) 2 ] (11c), and trans-[(PPh 3 ) 2 Pd(−CCC{O}NR 2 ) 2 ] (NR 2 = N(CH 2 ) 4 (13b), NMe 2 (13c), N(CH 2 ) 4 O (13d)), were synthesized by treating HCCC(O)NR 2 with AgNO 3 followed by transmetalation of the alkynyl ligand from silver to [PdCl 2 (PEt 3 ) 2 ], [PdCl 2 (P i Pr 3 ) 2 ], or [PdCl 2 (PPh 3 ) 2 ], respectively. Methylation of complexes 9b−e with MeOTf yields dicationic bis(allenylidene) complexes of palladium, trans-[(PEt 3 ) 2 Pd{CCC(OMe)NR 2 } 2 ] 2+ (OTf) − 2 (NR 2 = N(CH 2 ) 4 (10b-OTf), NMe 2 (10c-OTf), N(CH 2 ) 4 O (10d-OTf), N(CH 2 ) 5 (10e-OTf). Alkylation of complex 9e with [Me 3 O]BF 4 or [Et 3 O]BF 4 gave trans-[(PEt 3 ) 2 Pd{CCC(OR)N(CH 2 ) 5 } 2 ] 2+ (BF 4 ) −2 (R = Me (10e-BF 4 ), Et (10e′-BF 4 )). Complexes 11c and 13b− d were methylated accordingly to obtain the corresponding bis(allenylidene) complexes 12c-OTf, 12c-BF 4 , 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.

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The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2011

Herndon

2013

Coordination Chemistry Reviews

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Platinum allenylidene complexes and formation of platinum and palladium acetonitrile alkynyl complexes

Cited by 7 publications

References 48 publications

Computational Discovery of Stable Transition-Metal Vinylidene Complexes

Computational Discovery of Stable Transition-Metal Vinylidene Complexes

Palladium Alkynyl and Allenylidene Complexes: Very Efficient Precatalysts for C–C Coupling Reactions

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2011

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