N‐Heterocyclic Carbene Ligands and Iron: An Effective Association for Catalysis

Although iron has been known and widely used in coordination and organometallic chemistry for decades and N-heterocyclic carbenes (NHCs) have also been used for about half a century, their combination surprisingly did not become a hot topic in chemistry until this last decade. This review presents several recent and stimulating developments in homogeneous catalysis done mainly using iron/NHC-based catalysts. Of particular interest are the roles of iron/NHC complexes in cross-coupling Kochi reactions, CC bond formation reactions and hydrofunctionalization, and more particularly in hydrosilylation. Our review summarizes the key developments in these fields.

[1]  J. Mérour,et al.  Reactions d'alkylation de chlorures, formate et acetates allyliques catalyses par des complexes du fer et du cobalt , 1979 .

[2]  Jean-Baptiste Sortais,et al.  N-Heterocyclic Carbene Piano-Stool Iron Complexes as Efficient Catalysts for Hydrosilylation of Carbonyl Derivatives , 2011 .

[3]  W. Herrmann,et al.  Metallkomplexe heterocyclischer Carbene ‐ ein neues Katalysator‐Strukturprinzip in der homogenen Katalyse , 1995 .

[4]  J. Yaouanc,et al.  Modeling [FeFe] hydrogenase: Synthesis and protonation of a diiron dithiolate complex containing a phosphine-N-heterocyclic-carbene ligand , 2009 .

[5]  J. Kochi Electron-transfer mechanisms for organometallic intermediates in catalytic reactions , 1974 .

[6]  Joseph A. Wright,et al.  Molecular N2 complexes of iron stabilised by N-heterocyclic 'pincer' dicarbene ligands. , 2005, Chemical communications.

[7]  T. Roisnel,et al.  Iron piano-stool phosphine complexes for catalytic hydrosilylation reaction , 2012 .

[8]  J. Kochi,et al.  The Reactions of Grignard Reagents with Transition Metal Halides: Coupling, Disproportionation, and Exchange with Olefins , 1971 .

[9]  M. Beller,et al.  A convenient and general iron-catalyzed reduction of amides to amines. , 2009, Angewandte Chemie.

[10]  Yongsheng Wang,et al.  Enolate chelating N-heterocyclic carbene complexes of Fe(II): Synthesis, structure and their catalytic activity for ring-opening polymerization of ɛ-caprolactone , 2007 .

[11]  J. Long,et al.  First-row transition metal complexes of the strongly donating pentadentate ligand PY4Im. , 2010, Inorganic chemistry.

[12]  T. Hatakeyama,et al.  Highly selective biaryl cross-coupling reactions between aryl halides and aryl Grignard reagents: a new catalyst combination of N-heterocyclic carbenes and iron, cobalt, and nickel fluorides. , 2009, Journal of the American Chemical Society.

[13]  J. Kochi,et al.  Vinylation of Grignard reagents. Catalysis by iron , 1971 .

[14]  B. Trost,et al.  The atom economy--a search for synthetic efficiency. , 1991, Science.

[15]  K. Nicholas,et al.  Iron-catalyzed allylic alkylation , 1985 .

[16]  J. Kochi,et al.  Coupling of Grignard Reagents with Organic Halides , 1971 .

[17]  H. Brunner,et al.  Katalytische Hydrosilylierung oder Hydrierung an einer Koordinationsstelle von [Cp′Fe(CO)(X)]‐Fragmenten , 1990 .

[18]  Ming Zhang,et al.  Iron-catalyzed hydrosilylation reactions , 2010 .

[19]  H. Nishiyama,et al.  Highly efficient catalytic system for hydrosilylation of ketones with iron(II) acetate–thiophenecarboxylate , 2008 .

[20]  M. Hojo,et al.  Iron-Catalyzed Regio- and Stereoselective Carbolithiation of Alkynes. , 2001, Angewandte Chemie.

[21]  L. Zani,et al.  Selective hydrosilylation of ketones catalyzed by in situ‐generated iron NHC complexes , 2011 .

[22]  N. Lugan,et al.  A stable anionic N-heterocyclic carbene and its zwitterionic complexes. , 2008, Journal of the American Chemical Society.

[23]  G. Britovsek,et al.  Iron‐Catalyzed Polyethylene Chain Growth on Zinc: Linear α‐Olefins with a Poisson Distribution , 2002 .

[24]  Matthias Beller,et al.  Eisenkatalyse – ein nachhaltiges Prinzip mit Perspektive? , 2008 .

[25]  H. Nishiyama,et al.  An iron-catalysed hydrosilylation of ketones. , 2007, Chemical communications.

[26]  Jie Xiao,et al.  Synthesis, Structure, and Reactivity of Organo-Iron(II) Complexes with N-Heterocyclic Carbene Ligation , 2011 .

[27]  W. P. Fehlhammer,et al.  Ein Triscarben‐Chelatligand und sein Hexacarbeneisenkomplex , 1996 .

[28]  P. Forgione,et al.  Metal mediated carbometallation of alkynes and alkenes containing adjacent heteroatoms , 2001 .

[29]  T. Hatanaka,et al.  C-H bond activation/borylation of furans and thiophenes catalyzed by a half-sandwich iron N-heterocyclic carbene complex. , 2010, Chemistry, an Asian journal.

[30]  J. Kochi,et al.  Synthesis of olefins. Cross-coupling of alkenyl halides and Grignard reagents catalyzed by iron complexes , 1975 .

[31]  M. Beller,et al.  Asymmetrische Synthese von Aminen: eine allgemeine und effiziente eisenkatalysierte enantioselektive Transferhydrierung von Iminen , 2010 .

[32]  Alois Fürstner,et al.  The promise and challenge of iron-catalyzed cross coupling. , 2008, Accounts of chemical research.

[33]  T. Roisnel,et al.  Cyclopentadienyl–NHC Iron Complexes for Solvent‐Free Catalytic Hydrosilylation of Aldehydes and Ketones , 2012 .

[34]  M. Albrecht,et al.  Main-chain organometallic polymers comprising redox-active iron(II) centers connected by ditopic N-heterocyclic carbenes. , 2009, Dalton transactions.

[35]  T. Hatakeyama,et al.  Iron-catalyzed selective biaryl coupling: remarkable suppression of homocoupling by the fluoride anion. , 2007, Journal of the American Chemical Society.

[36]  T. Liu,et al.  Series of mixed valent Fe(II)Fe(I) complexes that model the Hox state of [FeFe]hydrogenase: redox properties, density-functional theory investigation, and reactivities with extrinsic CO. , 2008, Inorganic chemistry.

[37]  Wanzhi Chen,et al.  Direct synthesis of iron, cobalt, nickel, and copper complexes of N-heterocyclic carbenes by using commercially available metal powders. , 2009, Angewandte Chemie.

[38]  P. Luger,et al.  A Chelating Triscarbene Ligand and Its Hexacarbene Iron Complex , 1996 .

[39]  M. Beller,et al.  New catalytic properties of iron complexes: dehydration of amides to nitriles. , 2009, Chemical communications.

[40]  B. Trost,et al.  Asymmetric Transition Metal-Catalyzed Allylic Alkylations. , 1996, Chemical reviews.

[41]  Yong Zhang,et al.  Synthesis, structure of functionalized N-heterocyclic carbene complexes of Fe(II) and their catalytic activity for ring-opening polymerization of ε-caprolactone , 2006 .

[42]  David M. Jenkins,et al.  Synthesis of aziridines from alkenes and aryl azides with a reusable macrocyclic tetracarbene iron catalyst. , 2011, Journal of the American Chemical Society.

[43]  T. Liu,et al.  A mixed-valent, Fe(II)Fe(I), diiron complex reproduces the unique rotated state of the [FeFe]hydrogenase active site. , 2007, Journal of the American Chemical Society.

[44]  A. Fürstner,et al.  A cheap metal for a "noble" task: preparative and mechanistic aspects of cycloisomerization and cycloaddition reactions catalyzed by low-valent iron complexes. , 2008, Journal of the American Chemical Society.

[45]  B. Plietker,et al.  Dual Catalysis: Vinyl Sulfones through Tandem Iron‐Catalyzed Allylic Sulfonation Amine‐Catalyzed Isomerization , 2012 .

[46]  V. Guerchais,et al.  Syntheses, Properties, and X-ray Crystal Structures of Piano-Stool Iron Complexes Bearing an N-Heterocyclic Carbene Ligand , 2003 .

[47]  Licheng Sun,et al.  Preparation, characteristics and crystal structures of novel N -heterocyclic carbene substituted furan- and pyridine-containing azadithiolate Fe–S complexes , 2007 .

[48]  F. Hahn,et al.  Ruthenium(II) and iron(II) complexes of N-pyridyl substituted imidazolin-2-ylidenes , 2008 .

[49]  F. Heinemann,et al.  Unexpected reactivity resulting from modifications of the ligand periphery: Synthesis, structure, and spectroscopic properties of iron complexes of new tripodal N-heterocyclic carbene (NHC) ligands , 2010 .

[50]  A. Danopoulos,et al.  Structural and reactivity studies of "pincer" pyridine dicarbene complexes of Fe0: experimental and computational comparison of the phosphine and NHC donors. , 2009, Chemistry.

[51]  R. Grubbs,et al.  Highly active iron imidazolylidene catalysts for atom transfer radical polymerization , 2000 .

[52]  B. Plietker Iron Catalysis in Organic Chemistry , 2008 .

[53]  S. Enthaler A Facile and Efficient Iron‐Catalyzed Reduction of Sulfoxides to Sulfides , 2011 .

[54]  Jeremy M. Smith,et al.  A new synthetic route to bulky "second generation" tris(imidazol-2-ylidene)borate ligands: synthesis of a four coordinate iron(II) complex. , 2005, Chemical communications.

[55]  B. Plietker,et al.  Ligand‐Dependent Mechanistic Dichotomy in Iron‐Catalyzed Allylic Substitutions: σ‐Allyl versus π‐Allyl Mechanism , 2008 .

[56]  F. Glorius,et al.  Synthesis of Bis(N-heterocyclic carbene) Complexes of Iron(II) and Their Application in Hydrosilylation and Transfer Hydrogenation , 2012 .

[57]  H. Brunner,et al.  Catalytic Hydrosilylation or Hydrogenation at One Coordination Site of [Cp′Fe(CO)(X)] Fragments , 1990 .

[58]  D. Bruce,et al.  Iron-phosphine, -phosphite, -arsine, and -carbene catalysts for the coupling of primary and secondary alkyl halides with aryl Grignard reagents. , 2006, The Journal of organic chemistry.

[59]  M. Darensbourg,et al.  A {Fe(NO)3}10 trinitrosyliron complex stabilized by an n-heterocyclic carbene and the cationic and neutral {Fe(NO)2}(9/10) products of its NO release. , 2010, Journal of the American Chemical Society.

[60]  Jesse W. Tye,et al.  Dual electron uptake by simultaneous iron and ligand reduction in an N-heterocyclic carbene substituted [FeFe] hydrogenase model compound. , 2005, Inorganic chemistry.

[61]  B. Plietker,et al.  α-Sulfonyl succinimides: versatile sulfinate donors in Fe-catalyzed, salt-free, neutral allylic substitution. , 2011, Chemistry.

[62]  T. Hatanaka,et al.  C-H bond activation of heteroarenes mediated by a half-sandwich iron complex of N-heterocyclic carbene. , 2008, Journal of the American Chemical Society.

[63]  C. Pickett,et al.  Structural and functional analogues of the active sites of the [Fe]-, [NiFe]-, and [FeFe]-hydrogenases. , 2009, Chemical reviews.

[64]  F. Glorius,et al.  An Iron(II) Complex of a Diamine-Bridged Bis-N-Heterocyclic Carbene , 2012 .

[65]  Gregory A. Solan,et al.  IRON AND COBALT ETHYLENE POLYMERIZATION CATALYSTS BEARING 2,6-BIS(IMINO)PYRIDYL LIGANDS : SYNTHESIS, STRUCTURES, AND POLYMERIZATION STUDIES , 1999 .

[66]  Neil J Wells,et al.  Reactions of 'pincer' pyridine dicarbene complexes of Fe(0) with silanes. , 2009, Dalton transactions.

[67]  J. Yaouanc,et al.  N-Heterocyclic Carbene Ligands in Nonsymmetric Diiron Models of Hydrogenase Active Sites , 2007 .

[68]  B. Plietker,et al.  Präformierte π‐Allyl‐Eisen‐Komplexe als potente, definierte Katalysatoren für die allylische Substitution , 2009 .

[69]  João M. S. Cardoso,et al.  Unprecedented synthesis of iron-NHC complexes by C-H activation of imidazolium salts. Mild catalysts for reduction of sulfoxides. , 2012, Chemical communications.

[70]  G. Hilt,et al.  An iron-catalysed chemo- and regioselective tetrahydrofuran synthesis. , 2005, Chemical communications.

[71]  C. Bolm,et al.  Iron-catalysed carbon-heteroatom and heteroatom-heteroatom bond forming processes. , 2008, Chemical Society reviews.

[72]  Elina Buitrago,et al.  Efficient and Selective Hydrosilylation of Carbonyl Compounds Catalyzed by Iron Acetate and N-Hydroxyethylimidazolium Salts , 2012 .

[73]  B. Plietker,et al.  Fe-catalyzed multicomponent reactions: the regioselective alkoxy allylation of activated olefins and its application in sequential Fe catalysis. , 2012, Chemistry.

[74]  B. Liu,et al.  Facile synthesis of metal N-heterocyclic carbene complexes. , 2011, Chemical communications.

[75]  G. Britovsek,et al.  Iron-Catalyzed Polyethylene Chain Growth on Zinc: Linear α-Olefins with a Poisson Distribution This work was supported by BP plc. Dr. Gary Audley and Dr. Jane Boyle are thanked for GPC and NMR measurements, respectively. , 2002 .

[76]  H. Nagashima,et al.  New catalyst systems for iron-catalyzed hydrosilane reduction of carboxamides. , 2011, Chemical communications.

[77]  Mei Wang,et al.  Carbene-pyridine chelating 2Fe2S hydrogenase model complexes as highly active catalysts for the electrochemical reduction of protons from weak acid (HOAc). , 2007, Dalton transactions.

[78]  L. Zani,et al.  Iron-catalyzed reactions in organic synthesis. , 2004, Chemical reviews.

[79]  S. Okamoto,et al.  Iron-catalyzed intramolecular cyclotrimerization of triynes to annulated benzenes , 2006 .

[80]  R. S. Smith,et al.  Mechanistic studies of iron catalysis in the cross coupling of alkenyl halides and Grignard reagents , 1976 .

[81]  Robert H Morris,et al.  Asymmetric hydrogenation, transfer hydrogenation and hydrosilylation of ketones catalyzed by iron complexes. , 2009, Chemical Society reviews.

[82]  J. Weigand,et al.  Template-Controlled Formation of an [11]ane-P2CNHC Macrocyclic Ligand at an Iron(II) Template , 2010 .

[83]  M. Beller,et al.  Homogeneous catalysis using iron complexes: recent developments in selective reductions. , 2011, Chemical communications.

[84]  M. Albrecht,et al.  Piano-stool iron(II) complexes as probes for the bonding of N-heterocyclic carbenes: Indications for pi-acceptor ability , 2006 .

[85]  R. Grubbs,et al.  Carbenes As Catalysts for Transformations of Organometallic Iron Complexes , 2009, Science.

[86]  K. Bica,et al.  An iron-containing ionic liquid as recyclable catalyst for aryl grignard cross-coupling of alkyl halides. , 2006, Organic letters.

[87]  A. J. von Wangelin,et al.  On direct iron-catalyzed cross-coupling reactions , 2010 .

[88]  A. Fürstner,et al.  Cycloisomerization of enynes catalyzed by iron(0)-ate complexes. , 2005, Journal of the American Chemical Society.

[89]  Yukihiro Motoyama,et al.  Hydrosilane reduction of tertiary carboxamides by iron carbonyl catalysts. , 2009, Angewandte Chemie.

[90]  Joseph A. Wright,et al.  N-Heterocyclic Pincer Dicarbene Complexes of Iron(II): C-2 and C-5 Metalated Carbenes on the Same Metal Center , 2004 .

[91]  N. Nomura,et al.  Iron-Catalyzed Kharasch-Type Reaction Between Grignard Reagents and Allylic Phosphates.Highly SN2 Selective Cross-Coupling Process , 1991 .

[92]  Barry M. Trost,et al.  Atom Economy—A Challenge for Organic Synthesis: Homogeneous Catalysis Leads the Way , 1995 .

[93]  Malcolm L. H. Green,et al.  Migratory insertion in N-heterocyclic carbene-containing Fe carbonyl complexes: an experimental and theoretical study. , 2006, Dalton transactions.

[94]  Richard L. Harlow,et al.  A stable crystalline carbene , 1991 .

[95]  Jeremy M. Smith,et al.  Structural and spectroscopic characterization of an electrophilic iron nitrido complex. , 2008, Journal of the American Chemical Society.

[96]  B. Plietker,et al.  Selective C-S bond formation via Fe-catalyzed allylic substitution. , 2009, Organic letters.

[97]  B. Plietker Regioselective iron-catalyzed allylic amination. , 2006, Angewandte Chemie.

[98]  M. Beller,et al.  A convenient and general iron-catalyzed hydrosilylation of aldehydes. , 2007, Organic letters.

[99]  F. Gloaguen,et al.  N-Heterocyclic Carbene Ligands as Cyanide Mimics in Diiron Models of the All-Iron Hydrogenase Active Site , 2005 .

[100]  S. Okamoto,et al.  Intramolecular cyclotrimerization of triynes catalyzed by N-heterocyclic carbene-CoCl2/Zn or -FeCl3/Zn. , 2005, Organic letters.

[101]  Shogo Watanabe,et al.  Iron-catalyzed carbolithiation of alkynes having no heteroatoms. , 2009, Chemical Communications.

[102]  A. Fürstner,et al.  Iron-catalyzed cross-coupling reactions. , 2002, Journal of the American Chemical Society.

[103]  B. Plietker,et al.  Preformed pi-allyl iron complexes as potent, well-defined catalysts for the allylic substitution. , 2009, Angewandte Chemie.

[104]  B. Åkermark,et al.  Iron‐Catalyzed Nucleophilic Substitution of Allylic Acetate , 2007 .

[105]  L. Phong,et al.  Iron- and cobalt-catalyzed asymmetric hydrosilylation of ketones and enones with bis(oxazolinylphenyl)amine ligands. , 2010, Chemistry.

[106]  Matthias Beller,et al.  Sustainable metal catalysis with iron: from rust to a rising star? , 2008, Angewandte Chemie.

[107]  J. Ready,et al.  Iron-catalyzed carbometalation of propargylic and homopropargylic alcohols. , 2006, Journal of the American Chemical Society.

[108]  J. Cvengroš,et al.  Coming of age: sustainable iron-catalyzed cross-coupling reactions. , 2009, ChemSusChem.

[109]  M. Albrecht,et al.  Probing the potential of N-heterocyclic carbenes in molecular electronics: redox-active metal centers interlinked by a rigid ditopic carbene ligand. , 2008, Dalton transactions.

[110]  Chang-Liang Sun,et al.  Direct C-H transformation via iron catalysis. , 2011, Chemical reviews.

[111]  J. Steed,et al.  Bis(carbene)pyridine Complexes of the Early to Middle Transition Metals: Survey of Ethylene Oligomerization and Polymerization Capability , 2004 .

[112]  E. Shirakawa,et al.  Arylmagnesiation of alkynes catalyzed cooperatively by iron and copper complexes. , 2005, Journal of the American Chemical Society.

[113]  S. Kotha,et al.  Transition Metal Catalyzed (2+2+2) Cycloaddition and Application in Organic Synthesis , 2005 .

[114]  A. Fürstner,et al.  Advances in Iron Catalyzed Cross Coupling Reactions , 2005 .

[115]  Andrew J. P. White,et al.  Novel olefin polymerization catalysts based on iron and cobalt , 1998 .

[116]  M. Beller,et al.  Enantioselective synthesis of amines: general, efficient iron-catalyzed asymmetric transfer hydrogenation of imines. , 2010, Angewandte Chemie.

[117]  Bernd Plietker,et al.  Ligandenabhängige mechanistische Dichotomie in Eisen‐katalysierten allylischen Substitutionen: σ‐Allyl‐ kontra π‐Allyl‐Mechanismus , 2008 .

[118]  Bernd Plietker Die regioselektive eisenkatalysierte allylische Aminierung , 2006 .

[119]  Zhaoyang Li,et al.  Transition Metal-Catalyzed Carbocyclizations in Organic Synthesis. , 1996, Chemical reviews.

[120]  B. M. Trost Atomökonomische Synthesen – eine Herausforderung in der Organischen Chemie: die Homogenkatalyse als wegweisende Methode , 1995 .

[121]  Ying Xia,et al.  Synthesis of Anionic Iron(II) Complex Bearing an N-Heterocyclic Carbene Ligand and Its Catalysis for Aryl Grignard Cross-Coupling of Alkyl Halides , 2010 .

[122]  E. Peris,et al.  Iron(II) Complexes Bearing Chelating Cyclopentadienyl-N-Heterocyclic Carbene Ligands as Catalysts for Hydrosilylation and Hydrogen Transfer Reactions , 2010 .

[123]  Bernd Plietker Eine hochregioselektive, salzfreie Eisen‐katalysierte allylische Alkylierung , 2006 .

[124]  Li-Cheng Song,et al.  Synthesis, characterization and electrochemical behavior of some N -heterocyclic carbene-containing active site models of [FeFe]-hydrogenases , 2009 .

[125]  Bo Zhou,et al.  Studies on the enantioselectivity in Bu4N[Fe(CO)3NO]-catalyzed nucleophilic substitution of optically active allylic carbonates with malonate , 1988 .

[126]  B. Plietker A highly regioselective salt-free iron-catalyzed allylic alkylation. , 2006, Angewandte Chemie.

[127]  M. Ingleson,et al.  N-Heterocyclic carbene chemistry of iron: fundamentals and applications. , 2012, Chemical communications.

[128]  G. Venkanna,et al.  Well‐Defined Cyclopentadienyl NHC Iron Complex as the Catalyst for Efficient Hydrosilylation of Amides to Amines and Nitriles , 2011 .

[129]  M. Lautens,et al.  Transition Metal-Mediated Cycloaddition Reactions. , 1996, Chemical reviews.

[130]  J. Kochi,et al.  Iron catalysis in the reaction of grignard reagents with alkyl halides , 1971 .

[131]  W. Herrmann,et al.  Metal Complexes of N‐Heterocyclic Carbenes—A New Structural Principle for Catalysts in Homogeneous Catalysis , 1995 .

[132]  L. C. M. Castro,et al.  NHC-carbene cyclopentadienyl iron based catalyst for a general and efficient hydrosilylation of imines. , 2012, Chemical communications.

[133]  Maurice Brookhart,et al.  Highly Active Iron and Cobalt Catalysts for the Polymerization of Ethylene , 1998 .

[134]  Bo Zhou,et al.  On the regio- and stereoselectivity of Bu4N[Fe(CO)~3NO]- catalyzed allylic alkylation , 1987 .