Metallorganische Lewis–Säuren, LVI

Lippmann, E.; Kerscher, Thomas; Aechter, B.; Robl, Christian; Beck, Wolfgang; Price, David W.; Metz, Markus; Hofmann, Peter

doi:10.1016/s0022-328x(97)00718-3

“…The first direct bis(alkyne)!cyclobutadiene conversion was reported for the 14-electron cation [Re(CO) 4 ] + . [18] Finally, a particular co-ligand effect has been noted with [CpMoX]. Only when X = I does the reaction with F 3 CCCCF 3 in the presence of carbon monoxide result in a cyclobutadiene complex, while with X = Cl, Br the symmetry-allowed cyclization to the cyclopentadienone complex occurred.…”

Section: )]mentioning

confidence: 98%

By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes?

Veiros

¹

,

Dazinger

²

,

Kirchner

³

et al. 2004

Chemistry A European J

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The mechanism of formation of an eta4-cyclobutadiene complex from a metallacycle, generated by oxidative coupling of two acetylenes with the fragments CpRuCl, [CpRu(PH3)]+, CpCo, and CpRh, was investigated by means of DFT/B3LYP calculations. Two distinct pathways can be envisaged. 1) A multistep reaction, which can be denoted the Vollhardt mechanism, proceeding via a cyclopropenyl carbene and a tetrahedrane-type intermediate. 2) A one-step transformation involving the formation of a third M-C bond with rearrangement of the metallacyclic ring. Although path 2 is definitely favored over path 1, both pathways are energetically prohibitive unless substituents are present on the acetylene. For the CpRuCl system with HC triple bond CR the barrier varies with R in the series H approximately Ph>Me>>SiMe3. On going from H to SiMe3, the barrier for path 2 drops from 41.1 to 26.8 kcal mol(-1). This latter value is already reachable, in agreement with experiment. Whereas the reaction mechanisms involving the fragments CpCo, CpRh, and CpRuCl are very similar (but not identical owing to the additional ligand in CpRuCl), those of [CpRu(PH3)]+ reveal a modification with serious consequences. In both paths 1 and 2, the originally planar metallacycle experiences first a bending distortion induced by the sigma-donor strength of P (in contrast to Cl), which compensates the loss of electrons from the ring brought about by bending. The bent metallacycle is already electronically asymmetric and thus the further course of the reaction is facilitated.

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“…± Schmelzpunkt: 257±260°C (Zers. Re(CO) 3 (Ph 2 PCHPPh 2 )(Ph 2 PCH 2 P'Ph 2 ) (19) 85 mg (0.25 mmol) (g 3 -C 3 H 5 )Re(CO) 4 und 88 mg (0.23 mmol) 1,2-Bis-(diphenylphosphino)-methan (DPPM) werden, wie fu È r 10 beschrieben, zur Reaktion gebracht. Bereits nach 30 min hat sich eine gelbe Lo È sung gebildet.…”

Section: Experimenteller Teilunclassified

“…Durch Umsetzung von (g 3 -C 3 H 5 )Re(CO) 4 mit den zweiza È hnigen Chelat-Liganden 1,2-Bis(diphenylphosphino)ethan und 1,3-Bis(diphenylphosphino)propan, (Ph 2 PCH 2 ) 3 CMe sowie 2,2'-Bipyridin (L±L) la È ût sich die g 3 ® g 1 Umlagerung des Allyl-Liganden erzwingen und es bilden sich die g 1 -AllylKomplexe (g 1 -C 3 H 5 )Re(CO) 3 (L±L). Bei der Reaktion mit Bis(diphenylphosphino)methan wird der Allyl-Ligand in (g 3 -C 3 H 5 )Re(CO) 4 protoniert und als Propen unter Bildung des Diphosphinomethanid-Komplexes (OC) 3 Re-(Ph 2 PCHPPh 2 )(g 1 -Ph 2 PCH 2 PPh 2 ) (19) abgespalten. Erhitzen von (g 3 -C 3 H 5 )Re(CO) 4 sowie von (g 3 -C 3 H 5 )Re(CO) 3 (CN-2,5-Me 2 C 6 H 3 ) (5) in Methanol liefert die methoxy-verbru È ckten Komplexe Re 4 (CO) 12 (OH)(OMe) 3 bzw.…”

unclassified

“…The g 3 -g 1 conversion of the allyl ligand occurs on reaction of (g 3 -C 3 H 5 )Re(CO) 4 with the bidendate ligands 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino)propane and with 2,2'-bipyridine (L±L) which gives the complexes (g 1 -C 3 H 5 )Re-(CO) 3 (L±L). By reaction of (g 3 -C 3 H 5 )Re(CO) 4 with bis(diphenylphosphino)methane the allyl group is protonated and under elemination of propene the complex (OC) 3 Re(Ph 2 PCHPPh 2 )(g 1 -Ph 2 PCH 2 PPh 2 ) (19) with a diphosphinomethanide ligand is formed. On heating solutions of (g 3 -C 3 H 5 )Re(CO) 4 and (g 3 -C 3 H 5 )Re(CO) 3 (CN-2,5-Me 2 C 6 H 3 ) (5) in methanol the methoxy bridged compounds Re 4 (CO) 12 (OH)(OMe) 3 and Re 2 (CO) 4 (CN-2,5-Me 2 C 6 H 3 ) 4 -(l-OMe) 2 (20) were isolated.…”

mentioning

confidence: 99%

“…Aus g 3 -Benzyltetracarbonylrhenium sind Radikal-Komplexe zuga È nglich[14 b]. Butin[19] addiert werden ko È nnen. Isocyaniden sowie Benzonitril entstehen unter Substitution von CO die Tricarbonyl-Komplexe 1±6, mit Diphosphanen und mit 1,2-Bis(4-pyridyl)ethan die zweikernigen, ligandverbru È ckten Komplexe 7±9.…”

unclassified

See 2 more Smart Citations

Synthese, Struktur und Reaktivität von η1und η3-Allyl-Rhenium-Carbonylen

Aechter

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Polborn

²

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Beck

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2001

Z. anorg. allg. Chem.

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Rhenium: Organometallic Chemistry

Romão

¹

2005

Encyclopedia of Inorganic Chemistry

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The organometallic chemistry of Rhenium spans 11 oxidation states. Since many ligands stabilize several oxidation states, this chemistry is described by ligand type. Re‐Re multiple bonded organometallic complexes, Polynuclear organometallic complexes, and Bioorganometallic Chemistry, uncoverable in this fashion, are treated separately. The CO ligand dominates the chemistry of the lower oxidation states (Re −III to Re II ) most of which is derived from Re 2 (CO) 10 and the consequences of the rupture of its Re‐Re bond. [Re(CO) 5 ] • , [Re(CO) 5 ] − and Re(CO) 5 X are the most important products of Re‐Re homolysis, reduction and oxidation, respectively, and originate a vast chemistry. [ReX x (CO) y L z ] is the largest family of organorhenium complexes. The luminescent fac ‐[ReX(CO) 3 L 2 ] molecules assume high practical relevance in photoresponsive materials and sensors. Polyhydrides [ReH x L y ] lose H 2 upon thermal, photochemical or oxidative activation promoting alkane dehydrogenation. The abundant [Re(CO) x H y ] clusters are important building blocs for catalysts and materials. [ReH(CO) 4 ] n are analogues of cycloalkanes. Mononuclear homoleptic alkyls and aryls of Re in high oxidation states are limited to ReMe 6 and [Re(2‐MeC 6 H 4 ) 4 ]. Instead, carbenes and carbynes, as the remarkable [Re(≡CCMe 3 )(=CHCMe 3 )(CH 2 CMe 3 ) 2 ], are common. Re VII oxo and imido complexes also originate carbene/carbyne complexes active in olefin metathesis catalysis. ReO 3 Me (MTO) is a uniquely versatile catalyst in a wide variety of oxidation and O transfer catalysis. ReO 2 Me derivatives are active catalysts namely in aldehyde olefination. η 2 ‐, η 3 ‐, η 4 ‐ (dienes), η 6 ‐ (arenes) and η 7 ‐ (cycloheptatrienyl) ligands play a limited role in the organorhenium chemistry. Exceptional is, however, the activation of η 2 ‐arenes by Re I complexes. The dearomatized benzene ring in TpRe(CO)(MeIm)(η 2 ‐C 6 H 6 ) reacts as a diene. Unusual alkyne complexes appear in Re III and Re V oxides, e.g. ReR(O)(η 2 ‐RCCR) (R = H, alkyl). [Cp'Re(CO) 2 (η 3 ‐propargyl)] + complexes reveal a fascinating series of structural transformations and rearrangements. The cyclopentadienyl ligand (η 5 ‐C 5 R 5 = Cp’) shapes the large families of complexes of the fragments Cp’ 2 Re (rhenocene) Cp'Re(CO) 2 , [Cp'Re(NO)(PPh 3 )] + and Cp'ReO x X y . Hydrocarbyl transformations at these fragments and the understanding of the stereochemical control in enantioselective transformations of ligands bound to the chiral‐at‐metal fragment [Cp'Re(NO)(PPh 3 )] + are of outstanding relevance. Isoelectronic neutral or negative 6 e donors may enhance these transformations and support new ones. [Cp*Re(CO) 2 ] 2 and [Re(≡CCMe 3 )(OCMe 3 ) 2 ] 2 are rare examples of unsupported dimers of 16e fragments. Re isocyanide and nitrosyl complexes follow most of the structural and chemical patterns found for the carbonyl ligand. However, recent findings revealed that the participation of the O atom of the NO ligand in H bonding may lead to unexpected reactivity. Polynuclear Re complexes span a bewildering variety of synthetic methods and structural motifs. The ultimate rationale for their study is cooperative catalysis, as modelled in alkene hydrogenation with a Re/Pt binuclear complex and applied in petroleum refining with Pt x Re y clusters. Bioorganometallic chemistry is rapidly evolving into practical medical applications in diagnostics and therapy. Stable Re(CO) 3 fragments decorated with biologically active molecules are able to target Re compounds to specific tissues/organs. New synthetic methods have been developed for the synthesis of the required molecules in aqueous solution, avoiding the use of CO gas and classical high pressure synthesis.

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Metallorganische Lewis–Säuren, LVI

Cited by 11 publications

References 78 publications

By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes?

By What Mechanisms Are Metal Cyclobutadiene Complexes Formed from Alkynes?

Synthese, Struktur und Reaktivität von η1und η3-Allyl-Rhenium-Carbonylen

Rhenium: Organometallic Chemistry

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