Heterobimetallic templates for Carbon–Carbon bond formation by migratory insertion reactions involving CO, isonitriles or olefins

Braunstein, Pierre; Knorr, Michael; Stährfeldt, Thomas

doi:10.1039/c39940001913

Cited by 42 publications

(34 citation statements)

References 24 publications

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“…Although bridging silyl ligands have rarely been considered, this bonding situation has been structurally characterized in boranes, [30] in Li(THF) 4 [Cu 5 Cl 4 {Si(SiMe 3 ) 3 } 2 ], [31] and very recently in [(iPr 3 P)Rh(H)(m-Cl)(m-SiPh 2 )(m-SiPh 3 )Rh(H)(PiPr 3 )], which was prepared according to [Eq. (6)]. [32] These last results nicely support our mechanistic considerations about the migration of silyl ligands from one metal to another.…”

Section: Scheme 1 Formation and Dynamic Behavior Of A H 2 -M 2 -Si-osupporting

confidence: 73%

“…The yellow product was filtered and dried under vacuum. Yield: 87 mg, 90 %; elemental analysis calcd (%) for C 39 X-ray structure analyses: A summary of crystal data, data collection, and structure analysis for compounds 2 b, 2 c, 3 c, 6, and 12 f are given in Table 7. Data for 2 b and 2 c were collected on a Nonius CAD4-F diffractometer with Mo Ka graphite monochromated radiation (l 71.069 pm).…”

Section: Methodsmentioning

confidence: 99%

“…dppm bis(diphenylphosphino)methane), and we could take advantage of the resulting masked coordination site available on palladium to perform multi-insertion of organic isonitriles, sequential CO/olefin insertion into the Pd-Me bond, [6,7] or catalytic dehydrogenative coupling of stannanes. [8,9] In the course of our studies on the carbonylation of alkyl complexes, we observed a bimetallic rearrangement involving migration of the iron-bound alkoxysilyl or siloxysilyl ligand to the oxygen atom of the palladium-bound acyl ligand, thus leading to a rare example of bridging siloxycarbene ligand [Eq.…”

Section: Scheme 1 Formation and Dynamic Behavior Of A H 2 -M 2 -Si-omentioning

confidence: 99%

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Novel Metal-to-Metal Silyl-Migration Reactions in Heterometallic Complexes

Braunstein¹,

Knorr²,

Reinhard³

et al. 2000

Chem. Eur. J.

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An unprecedented, intramolecular metal-to-metal silyl ligand migration reaction has been discovered in a series of phosphido-bridged iron-platinum complexes and which may be triggered by an external nucleophile. Thus, reaction of solutions of [(OC)3-(R1/3Si)Fe(mu-PR2R3)Pt(1,5-COD) (1a R1 = OMe, R2 = 3 = Ph; 1b R1 = OMe, R2 = R3 = Cy; 1c R1 = Ph, R2 = R3 = Ph; 1d R1 = Ph, R2 = R3 = Cy; 1e R1 = Ph, R1 = H, R3 = Ph) in CH2Cl2 with CO rapidly afforded the corresponding complexes [(OC)4Fe(mu-PR2R3)Pt(SiR1/3)-(CO)] (2a-e) in which the silyl ligand has migrated from Fe to Pt, while two CO ligands have been ligated, one on each metal. When 1a or 1c was slowly treated with two equivalents of tBuNC at low temperature, quantitative displacement of the COD ligand was accompagnied by silyl migration from Fe to Pt and coordination of an isonitrile ligand to Fe and to Pt to give [(OC)3-(tBuNC)Fe(mu-PPh2)Pt[Si(OMe)3](CNtBu)] (3a) and [(OC)3(tBuNC)-Fe(mu-PPh2)Pt[SiPh3](CNtBu)] (3c). Reaction of 2a with one equivalent of tBuNC selectively led to substitution of the Pt-bound CO to give [(OC)4-Fe(mu-PCy2)Pt[Si(OMe)3](CNtBu)] (4b), which reacted with a second equivalent of tBuNC to give [(OC)4Fe(mu-PCy2)-Pt[Si(OMe)3](CNtBu)2] (5b) in which the metal-metal bond has been cleaved. Opening of the Fe-Pt bond was also observed upon reaction of 3a with tBuNC to give [(OC)3(tBuNC)-Fe(mu-PPh2)Pt[Si(OMe)3](CNtBu)2] (6). The silyl ligand migrates from Fe, in which it is trans to mu-PR2R3 in all the metal-metal-bonded complexes, to a position cis to the phosphido bridge on Pt. However, in 5a,b and 6 with no metal-metal bond, the Pt-bound silyl ligand is trans to the phosphido bridge. The intramolecular nature of the silyl migration, which may be formally viewed as a redox reaction, was established by a cross-over experiment consisting of the reaction of 1a and 1d with CO; this yielded exclusively 2a and 2d. The course of the silyl-migration reaction was found to depend a) on the steric properties of the -SiR1/3 ligand, and for a given mu-PR2R3 bridge (R2 = R3 = Ph), the migration rate decreases in the sequence Si(OMe)3> SiMe2Ph> SiMePh2>>SiPh3; b) on the phosphido bridge and for a given silyl ligand (R1 = OMe), the migration rate decreases in the order mu-PPh2 >> mu-PHCy; c) on the external nucleophile since reaction of 1c with two equivalents of P(OMe)3, P(OPh)3 or Ph2PCH2C(O)Ph led solely to displacement of the COD ligand with formation of 11a-c, respectively, whereas reaction with two equivalents of tBuNC gave the product of silyl migration 3c. Reaction of [(OC)3-[(MeO)3Si]Fe(mu-PPh2)Pt(PPh3)2] (7a) with tBuNC (even in slight excess) occurred stereoselectively with replacement of the PPh3 ligand trans to mu-PPh2, whereas reaction with CO led first to [(OC)3((MeO)3Si)Fe(mu-PPh2)Pt(CO)-(PPh3)] (8a), which then isomerized to the migration product [(OC)4Fe(mu-PPh2)Pt[Si(OMe)3](PPh3)] (9a). Most complexes were characterized by elemental analysis, IR and 1H, 31P, 13C, and 29Si NMR spectroscopy, and in five cases by X-ray diffraction.

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Section: Scheme 1 Formation and Dynamic Behavior Of A H 2 -M 2 -Si-osupporting

confidence: 73%

Section: Methodsmentioning

confidence: 99%

Section: Scheme 1 Formation and Dynamic Behavior Of A H 2 -M 2 -Si-omentioning

confidence: 99%

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Novel Metal-to-Metal Silyl-Migration Reactions in Heterometallic Complexes

Braunstein¹,

Knorr²,

Reinhard³

et al. 2000

Chem. Eur. J.

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“…We have shown in recent publications that the dianionic tin ligands [EB 11 H 11 ] 2-(E = Ge, Sn) substitute halides in various transition metal complexes and furthermore are able to replace chelating diolefin ligands like 1,5- (M = Pd, Pt; E = Ge, Sn). [21,25] Thus it is not surprising, that a mixture of isocyanide palladium complex [(RNC) 2 -PdCl 2 ] (RNC = benzyl, tert-butyl, cyclohexyl, 2,6-dimethylphenyl) with four equivalents of tin nucleophile reacts to give the known square-planar complex [Pd(SnB 11 H 11 ) 4 ] 6-.…”

Section: Resultsmentioning

confidence: 99%

“…[9,10] Besides coordinating at palladium atoms isocyanides can also insert into palladium-carbon bonds, palladium-platinum bonds or react catalytically with palladium complexes to insert into silicon-silicon or silicon-tin bonds. [11][12][13][14][15][16][17][18][19][20] As part of our coordination chemistry project we are studying the ligand abilities of the germylene and stannylene type ligands [GeB 11 [21][22][23][24][25][26][27][28][29][30][31][32][33] In this publication we are presenting the results of our studies of the palladium coordination chemistry with stanna-closododecaborate and isocyanide ligands. Substitution reactions and insertion reactions are discussed.…”

Section: Introductionmentioning

confidence: 99%

Palladium Chemistry with Stanna‐closo‐dodecaborate and Isocyanides

Hornung

Wesemann

2010

Eur J Inorg Chem

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The substitution equilibrium between isocyanides and stanna‐closo‐dodecaborate with palladium(II) was investigated. The mixed substituted products of type [(RNC)2Pd(SnB11H11)2]2– and [(RNC)Pd(SnB11H11)3]4– were characterized by X‐ray crystal structure analysis, elemental analysis and NMR spectroscopy. Isocyanide insertion into palladium–carbon bonds was also found. The zwitterionic complexes isolated from the reaction of [(P′2)Pd(Me)(SnB11H11)]– (P′2 = dppe, dppp, dppf) with isocyanides were characterized.

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Hemilabilität von Hybridliganden und die Koordinationschemie von Oxazolinliganden

2001

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Das Ligandendesign gewinnt auf dem Gebiet der chemischen Synthese immer mehr an Bedeutung, denn mit Hilfe von speziellen Liganden lassen sich die Eigenschaften von Komplexen in vielfältiger Weise beeinflussen. Liganden mit verschiedenen Funktionalitäten, z. B. solche mit harten und weichen Donoren, werden oft als Hybridliganden bezeichnet und zunehmend in der Molekülchemie verwendet. Zwar ist schon lange bekannt, dass die elektronischen und sterischen Eigenschaften der Koordinationssphäre eines Komplexes sehr eng mit dessen chemischen und physikalischen Eigenschaften zusammenhängen, doch ist eine Voraussage des Verhaltens von Liganden schwierig, nicht nur wegen der bei diesen Veränderungen auftretenden geringen Energiedifferenzen, sondern auch wegen der beträchtlichen Diversität innerhalb des Periodensystems – ein bestimmter Ligand kann sich gegenüber verschiedenen Metallen ganz unterschiedlich verhalten, und der Austausch eines Liganden gegen einen anderen in einem gegebenen Metallkomplex kann dessen Chemie vollkommen verändern. Neue Systeme könnten, auch rein zufällig, zu nützlichen, allgemein gültigen Konzepten führen, mit deren Hilfe Molekülstrukturen mit bestimmten Eigenschaften maßgeschneidert werden können. Einige Eigenschaften von zahlreichen Metallkomplexen mit Hybridliganden lassen sich mit der „Hemilabilität“ dieser Liganden erklären – einem sehr nützlichen Konzept, um die Eigenschaften der Metallkomplexe zu deuten und um neue Systeme für die molekulare Aktivierung und die homogene Katalyse sowie funktionelle Materialien und Sensoren für niedermolekulare Verbindungen zu entwerfen. In der homogenen enantioselektiven Katalyse wird in einem metallvermittelten Prozess durch sterische und/oder elektronische Kontrolle ein Stereoisomer bevorzugt gebildet. Die Verwendung von Liganden mit einem oder mehreren chiralen Oxazolinresten in diesen metallkatalysierten Reaktionen führte in vielen Fällen zu guten Ergebnissen. Die Einführung von Oxazolinresten in multifunktionelle Liganden erhöht deren Komplexität und die Wahrscheinlichkeit, dass hemilabile Eigenschaften auftreten, die bis vor kurzem in der Oxazolinchemie noch nicht beobachtet worden sind. In diesem Übersichtsartikel werden wir zunächst kurz auf die Definitionen und die Anwendungsmöglichkeiten hemilabiler Liganden eingehen, dann die Hauptklassen der Liganden mit einem oder mehreren Oxazolinresten vorstellen, wobei der Schwerpunkt auf den Hybridliganden liegt, und abschließend erläutern, warum die Kombination dieser beiden Aspekte des Ligandendesigns besonders viel versprechend erscheint.

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Heterobimetallic templates for Carbon–Carbon bond formation by migratory insertion reactions involving CO, isonitriles or olefins

Abstract: New patterns for heterobimetallic reactivity are presented that combine electronic effects (of the metal-metal bond) and steric control (by a bridging, hemilabile trialkoxysilyl ligand) in organometallic insertion reactions involving isonitriles, CO and olefins.

Cited by 42 publications

References 24 publications

Novel Metal-to-Metal Silyl-Migration Reactions in Heterometallic Complexes

Novel Metal-to-Metal Silyl-Migration Reactions in Heterometallic Complexes

Palladium Chemistry with Stanna‐closo‐dodecaborate and Isocyanides

Hemilabilität von Hybridliganden und die Koordinationschemie von Oxazolinliganden

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