Rare-earth Metal Alkyl Complexes Research Articles

Reactivity of Rare Earth Metal Alkyl Complexes with Nitriles or Isonitrile: Versatile Ways toward Multiply Functionalized β-Diketiminato, (Iso)indolyl, and Imidazolyl Chelating Rare Earth Metal Complexes.

The reactivity of the rare earth metal alkyl complexes LRE(CH2SiMe3)(THF)2 (1RE) [RE = Y (1Y), Yb (1Yb), Lu (1Lu); L = 2,5-[(2-pyrrolyl)CPh2]2(N-methylpyrrole)] with various nitriles and isonitriles has been fully developed. Treatment of the yttrium monoalkyl complex (1Y) with 2 equiv of aromatic nitriles afforded the symmetric trisubstituted β-diketiminato yttrium complexes (2Y(H), 2Y(Me), and 2Y(F)) through successive cyano group insertion into the RE-C bond and 1,3-H shift or the unsymmetric trisubstituted β-diketiminato yttrium complex (3Y) unexpectedly via a 1,3-SiMe3 shift when 4-(trifluoromethyl)benzonitrile was used in this reaction under the same conditions. By treating 1Y with 2 equiv of tolyl acetonitrile, an activation of the sp3 C-H bond occurred to form the corresponding β-aryl keteniminato complexes 4Y(p-tol) and 4Y(m-tol). Remarkably, a heteroleptic cleavage of the CO-CN bond took place in the reaction of 1Y with benzoyl nitrile, affording the unsymmetric trinuclear yttrium complex 5Y bridged by three cyanide groups. Dinuclear ytterbium and lutetium complexes 6Yb and 6Lu containing a functionalized isoindole fragment were synthesized from the reactions of 1 with phthalonitrile by tandem insertion and cyclization. Further studies indicated that the temperature and stoichiometric ratio have a great influence on the reactivity patterns between the reactions of 1RE with benzylisonitrile: two tetrasubstituted β-diketiminato complexes 8 and 9 were obtained at -30 °C, and tetrasubstituted imidazolyl yttrium and lutetium complexes 7 were isolated at elevated temperature, respectively. In addition, the tetrasubstituted β-diketiminato complexes 8 and 9 could be irreversibly converted to the cyclization products 7 by elevating the reaction temperature not only on the NMR scale but also on the preparative scale. Notably, when the phenyl isonitrile instead of benzyl isonitrile was reacted with 1Yb, a 2,3-functionalized indolyl ytterbium complex 10Yb was isolated.

Aryl C-H bond functionalization with diphenyldiazomethane induced by rare-earth metal alkyl complexes.

The first examples of regioselective aryl ortho-C-H functionalization with diphenyldiazomethane for the construction of Caryl-Nhydrazinato bonds were accomplished via the activation of C-H bonds and the subsequent reaction of diphenyldiazomethane with the RE-Caryl bond. The reactions of rare-earth metal monoalkyl complexes LRE(CH2SiMe3)(THF)2 (L = 2,5-[(2-pyrrolyl)CPh2]2(N-Me-pyrrole)) supported by a neutral N-methylpyrrole anchored dipyrrolyl ligand with 2 equiv. of Ph2CN2 gave irreversibly unprecedented hydrazonato-functionalized imino rare-earth metal complexes LRE(Ph2CNNC6H4-(o-CNHPh) (RE = Y (2a), Lu (2a')) in good yields involving a rather complex process including the interaction of a diazo unit with a RE-Calkyl bond, a β-H elimination, a N-N cleavage, 1,4-hydrogen transfer and the subsequent C-N coupling with another diphenyldiazomethane. More important is that regioselective aryl C-H bond functionalization with diphenyldiazomethane to construct the Caryl-Nhydrazinato bonds can be easily achieved by three-component reactions of rare-earth metal monoalkyl complexes, a wide range of substituted imines (including aldimines, ketimines or analogous 2-phenylpyridine) and diphenyldiazomethane, affording various hydrazonato-functionalized phenyl, thienyl imino or pyridyl rare-earth metal complexes 2b-2j at room temperature. A further study indicated that the substituents on the phenyl ring have a great effect on the reaction pathway and governed the Caryl-Nhydrazinato bond construction. Moreover, the experimental studies show that the formation of the Caryl-Nhydrazinato bonds is thermodynamically facile, which could be realized at room temperature easily.

Flexible Coordination of the Bis(amino-oxazoline) Ligand in Rare-Earth Metal Complexes: Synthesis, Structure, and Their Reactivity and Polymerization Performance.

Mononuclear rare-earth metal alkyl complexes supported by tetradentate dianionic bis(amino-oxazoline) ligands have been synthesized, and their reactivity toward small molecules and catalytic performance on ring-opening polymerization have been studied. Treatment of Ln(CH2SiMe3)3(THF)2 (Ln = Sc, Y; THF = tetrahydrofuran) with the bis(amino-oxazoline) proligand H2L afforded the corresponding rare-earth metal monoalkyl complexes L-Ln(CH2SiMe3)(THF)x (Ln = Sc, x = 0 (1); Ln = Y, x = 1 (2)). The isopropyl-substituted Sc alkyl complex L'-Sc(CH2SiMe3) (3) and the analogue Y silylamide complex L-Y[N(SiHMe2)2] (4) have been prepared by a similar method. Complexes 1 and 2 were stable in solution at room temperature but transformed gradually at elevated temperature to give a nucleophilic addition product for Sc (5) and an oxazoline ring-opened dimeric complex for Y (6). Reactions of 1 with elemental sulfur and selenium each led to insertion of one chalcogen into the Sc-C bond, and the corresponding six-coordinate mononuclear chalcogenolate complexes L-Sc(ECH2SiMe3)(THF) (E = S (7), Se (8)) were isolated. Treatment of 1 with an equimolar amount of aniline yielded the Sc anilide complex L-Sc(NHC6H5) (9), whereas the reaction of 1 with [NHEt3][BPh4] afforded the Sc ion-pair [L-Sc][BPh4] (10), which upon recrystallization led to formation of a THF-solvated product [L-Sc(THF)][BPh4] (11). Single-crystal X-ray diffraction analyses of complexes 1-3, 7-9, and 11 revealed the flexible coordination capability of the tetradentate bis(amino-oxazoline) ligand of upholding a mononuclear metal center via a torsion of the diaminobiphenyl axis. Complexes 1-4 were active catalysts for initiating the ring-opening polymerization of rac-lactide with good activity (TOF up to 3204 h-1) and heteroselectivity (Pr = 0.65-0.71). This study highlights the applicability of the well-defined tetradentate bis(amino-oxazoline) ligands for mononuclear rare-earth metal complexation and shed light on the new potential of rare-earth metal catalysts bearing this type of easily derivatizable polydentate ligand.

Synthesis, structure of dinuclear o-phenylene linked bis(amidinate) rare-earth metal complexes and their catalytic activity towards Strecker reaction

New dinuclear o-phenylene linked bis(amidinate) rare-earth metal alkyl complexes [{C6H4–1,2-(NCtBuNC6H5)2}RECH2SiMe3]2 (RE = Y (1), Er (2), Yb (3)) were synthesized in high yields. All complexes were established by single-crystal X-ray diffraction studies, which revealed that each bis(amidinate) ligand linked to two metal ions with one amidinate group coordinated to the metal ion in classical κ2-N,N’ modes, while the other amidinate group worked as a bridge coordination with the two metal ions in μ-κ2:κ1 chelating mode, resulting in the formation of amidinate group bridged dinuclear complexes. The complexes exhibited excellent catalytic reactivity for the Strecker reaction with wide range of unactivated imines under solvent-free conditions in presence of 1.0 mol% catalyst loading.

Trivalent rare-earth metal cyclic (alkyl)(amino)carbene complexes.

Coordination chemistry of cyclic (alkyl)(amino)carbene (CAAC) ligands has blossomed in recent years, exemplified by their strong σ-donating and π-accepting ability. However, trivalent rare-earth metal CAAC complexes remain elusive. By using M(CH2SiMe3)3(THF)2 (M = Sc, Y and Lu) as precursors, we synthesized mono CAAC coordinated rare-earth metal trisalkyl complexes, (RCAAC)M(CH2SiMe3)3 (R = Me and Et, M = Sc, Y and Lu). In addition, when MI3(Et2O)n (M = Y and Yb) were employed as metal precursors, bis(CAAC)-stabilized rare-earth metal triiodide complexes (MeCAAC)2MI3 (M = Y and Yb) could be obtained. All new compounds were characterized by X-ray crystallography, elemental analysis and NMR spectroscopy. Density functional theory calculations were conducted for these rare-earth metal CAAC complexes to gain insight into their electronic structures and bonding interactions. The bonding analysis unveils that the CAAC ligands act as σ donors to trivalent rare-earth metal ions and may be involved in π-bonding upon reduction.

Syntheses of Rare-Earth Metal Alkyl Complexes Bearing a Dianionic α-Iminopyridyl Ligand and Their Catalytic Activities toward Polymerization of 2-Vinylpyridine

Syntheses of Rare-Earth Metal Alkyl Complexes Bearing a Dianionic α-Iminopyridyl Ligand and Their Catalytic Activities toward Polymerization of 2-Vinylpyridine

Synthesis, Characterization, and Catalytic Activity of Dinuclear Rare-Earth Metal Alkyl Complexes Bearing 2,6-Diisopropylphenylamidomethyl Functionalized Pyrrolyl Ligand

Synthesis, Characterization, and Catalytic Activity of Dinuclear Rare-Earth Metal Alkyl Complexes Bearing 2,6-Diisopropylphenylamidomethyl Functionalized Pyrrolyl Ligand

Dehydrogenative Coupling of Terminal Alkynes with O/N-Based Monohydrosilanes Catalyzed by Rare-Earth Metal Complexes.

Newly synthesized rare-earth metal alkyl complexes bearing a tripyrrolyl ligand act as excellent precatalysts for the cross-dehydrogenative coupling between various terminal alkynes and O/N-based monohydrosilanes of HSi(OEt)3/HSi(NMe2)3, leading to the formation of a variety of alkoxysilylalkyne and aminosilylalkyne derivatives in good to high yields. The precatalysts LRE(CH2SiMe3)(thf)2 (RE = Y(1a), Er(1b), Yb(1c), L = 2,5-[(2-C4H3N)CPh2]2(C4H2NMe), thf = tetrahydrofuran) were easily prepared in high yields via the reactions of RE(CH2SiMe3)3(thf)2 with the proligand H2L in a single step. Mechanistic studies reveal that treatment of 1 with phenylacetylene could generate the active catalytic species: dinuclear rare-earth metal alkynides (L(thf)n[RE(μ-C≡CPh)]2L) (RE = Y(5a), n = 1; Yb(5c), n = 0), which could react with HSi(OEt)3 to produce the coupling product 4aa and the dinuclear rare-earth metal hydrides (L (thf)[RE(μ-H)]2L) (RE = Y(6a); Yb(6c)). By contrast, prior treatment of 1c with HSi(OEt)3 proceeds via cleavage of the Si-O bond to produce the dinuclear ytterbium alkoxide (LYb(μ-OEt))2 7c, which is inert in the dehydrogenative coupling reaction. The results of the mechanistic studies are consistent with the observation that the reaction is greatly influenced by the addition sequence of precatalyst/alkynes/silanes.

Multimetallic Rare Earth and Group 4 Transition Metal Hydrides for Novel Transformations of Small Molecules

Hydrogenolysis of mono(cyclopentadienyl (Cp))-ligated rare earth metal alkyl complexes with H2 affords a variety of multimetallic rare earth hydride complexes, which can serve as a unique platform ...

Samarium(II) Monoalkyl Complex Supported by a β-Diketiminato-Based Tetradentate Ligand: Synthesis, Structure, and Catalytic Hydrosilylation of Internal Alkynes.

The synthesis and catalytic applications of trivalent rare-earth metal alkyl complexes have been well developed, but the chemistry of divalent rare-earth metal alkyl complexes lagged much behind. Herein, we report the synthesis, structure, and catalytic applications of a samarium(II) monoalkyl complex supported by a β-diketiminato-based tetradentate ligand, [LSmCH(SiMe3 )2 ] (L=[MeC(NDipp)CHC(Me)NCH2 CH2 N(Me)CH2 CH2 NMe2 ]- , Dipp=2,6-(iPr)2 C6 H3 ). This complex is synthesized by the salt metathesis reaction of samarium iodide [LSm(μ-I)]2 and KCH(SiMe3 )2 in 63 % yield. Its structure is characterized by single-crystal X-ray diffraction, showing a distorted square-pyramid coordination geometry. This samarium(II) monoalkyl complex exhibits high catalytic activity in the hydrosilylation of aryl and methyl-substituted unsymmetrical internal alkynes with secondary hydrosilanes, selectively providing the α-(E) products in high yields.

ChemInform Abstract: Lanthanides and Actinides: Annual Survey of Their Organometallic Chemistry Covering the Year 2015

AbstractReview: 176 refs.

ChemInform Abstract: Palladium‐Catalyzed C(sp3)—C(sp2) Cross‐Coupling of Homoleptic Rare‐Earth Metal Trialkyl Complexes with Aryl Bromides: Efficient Synthesis of Functionalized Benzyltrimethylsilanes.

The first C(sp3)–C(sp2) cross-coupling of rare-earth metal alkyl complexes with aryl bromides has been developed. This reaction was conducted at low catalyst loading (0.5 mol%) and exhibited a broad substrate scope, thus providing a facile method for the synthesis of benzyltrimethylsilanes with diverse functional groups.

Simple entry into N-tert-butyl-iminophosphonamide rare-earth metal alkyl and chlorido complexes.

In situ protolysis reaction of a highly basic and sterically hindered N,N'-di-tert-butyl-iminophosphonamide ligand Ph2P([double bond, length as m-dash]N-tBu)(NH-tBu) = (NPN(tBu))H (1) with equimolar or hemimolar amounts of rare-earth metal tris-alkyls leads to dialkyl [(NPN(tBu))Ln(CH2SiMe3)2(THF)n] (Ln = Sc, n = 0 (2), Ln = Y, n = 1 (3)) and monoalkyl species [(NPN(tBu))2Ln(CH2SiMe3)] (Ln = Y (4), Nd (6), Sm (7)). One-pot reaction of [ScCl3(THF)3]/1/MeLi in 1/2/3 eq. ratio gives [(NPN(tBu))2Sc(THF)CH3] 5. Further reaction of 4 with phenylacetylene resulted in the formation of the Y-alkynyl complex [(NPN(tBu))2Y(-C[triple bond, length as m-dash]CPh)] 8. Alkyl abstraction in 2, 3 and 4 by reaction with [PhNMe2H](+)[B(C6F5)4](-) resulted in the formation of cationic alkyl complex ion-pairs [(NPN(tBu))Ln(CH2SiMe3)(THF)n](+)[B(C6F5)4](-) (Ln = Sc (9), Y (10)) and [(NPN(tBu))2Y(THF)n](+)[B(C6F5)4](-)11, as confirmed by NMR data. The reaction of bis-NPN alkyl complexes with CHCl3 is the simplest and most reliable protocol to synthesize bis-NPN-chlorido complexes [(NPN(tBu))2Ln-Cl] (Ln = Sc (12), Y (13), Nd (14), Sm (15), Gd (16), Tb (17), Yb (18) and Lu (19)), which can become new post-metallocene alternatives to the prominent organolanthanide building blocks [Cp*2LnX]. Partial hydrolysis of 12 leads to the formation of the oxido/chlorido-capped trinuclear complex [{(NPN(tBu))Sc(μ2-Cl)}3(μ3-O)(μ3-Cl)] 20. Molecular structures of 4, 6, 7, 13, 19 and 20 were confirmed by X-ray structure analyses.

Palladium-catalyzed C(sp(3))-C(sp(2)) cross-coupling of homoleptic rare-earth metal trialkyl complexes with aryl bromides: efficient synthesis of functionalized benzyltrimethylsilanes.

The first C(sp(3))-C(sp(2)) cross-coupling of rare-earth metal alkyl complexes with aryl bromides has been developed. This reaction was conducted at low catalyst loading (0.5 mol%) and exhibited a broad substrate scope, thus providing a facile method for the synthesis of benzyltrimethylsilanes with diverse functional groups.

Rare-earth metal alkyl complexes bearing an alkoxy N-heterocyclic carbene ligand: synthesis, characterization, catalysis for isoprene polymerization

The new rare-earth metal alkyl complexes bearing alkoxy NHC ligands were prepared, which showed moderate cis-1,4 selectivity for isoprene polymerization.

Dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in μ-η(2) :η(1) :η(1) hapticities and their high catalytic activity for isoprene 1,4-cis-polymerization.

Two series of new dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in novel μ-η(2) :η(1) :η(1) hapticities are synthesized and characterized. Treatment of [RE(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of 3-(tBuN=CH)C8 H5 NH (L1 ) in THF gives the dinuclear rare-earth metal alkyl complexes trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH(CH2 SiMe3 )}Ind)RE(thf)(CH2 SiMe3 )]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C=N group is transferred to the amido group by alkyl CH2 SiMe3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ-η(2) :η(1) :η(1) bonding modes, forming the dinuclear rare-earth metal alkyl complexes. When L1 is reduced to 3-(tBuNHCH2 )C8 H5 NH (L2 ), the reaction of [Yb(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of L2 in THF, interestingly, generated the trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (major) and cis-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (minor) complexes. The catalytic activities of these dinuclear rare-earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio- and stereoselectivities for isoprene 1,4-cis-polymerization.

Cationic Tropidinyl Scandium Catalyst: A Perfectly Acceptable Substitute for Cationic Half-Sandwich Scandium Catalysts in cis-1,4-Polymerization of Isoprene and Copolymerization with Norbornene

Different nonmetallocene rare earth metal alkyl complexes such as monotropidinyl (Trop) scandium dialkyl complex (Trop)Sc(CH2SiMe3)2(THF) (1), ditropidinyl yttrium alkyl complex (Trop)2Y(CH2SiMe3)(THF) (3) as well as binuclear lutetium alkyl complex bearing one tetradentate dianionic 6-N-methyl-1,4-cycloheptadienyl (NMCH) ligand [(NMCH)Lu(CH2SiMe3)(THF)]2 (2) have been synthesized in high yields via one-pot acid–base reaction by using of the tris(trimethylsilylmethyl) rare earth metal complexes with the readily available natural product tropidine. The polymerization experiments indicate that the monotropidinyl scandium dialkyl complex 1 displays reactivity akin to that of the analogous monocyclopentadienyl scandium dialkyl complexes. In the presence of activator and a small amount of AlMe3, complex 1 exhibits similar activities (up to 1.6 × 106 g molSc–1 h–1) but higher cis-1,4-selectivities (up to 100%) than (C5H5)Sc(CH2SiMe3)2(THF) (cis-1,4-selectivity as 95%) in the isoprene polymerization, yielding the pure cis-1,4-PIPs with moderate molecular weights (Mn = 0.5–11.2 × 104 g/mol) and bimodal molecular weight distributions (Mw/Mn = 1.48–6.07). Moreover, the complex 1/[Ph3C][B(C6F5)4/AliBu3 ternary system also shows good comonomer incorporation ability in the copolymerization of isoprene and norbornene similar to the [C5Me4(SiMe3)]Sc(η3-CH2CHCH2)2/activator binary system, affording the random isoprene/norbornene copolymers with a wide range of isoprene contents around 57–91 mol % containing cis-1,4 configuration up to 88%.

Phosphazene-Functionalized Cyclopentadienyl and Its Derivatives Ligated Rare-Earth Metal Alkyl Complexes: Synthesis, Structures, and Catalysis on Ethylene Polymerization

Treatment of Ln(CH2SiMe3)3(thf)2 (Ln = Sc, Y, and Lu) with 1 equiv of CpPN-type ligands C5H4═PPh2–NH–C6H3R2 (R = Me, L1(Me); R = iPr, L1(iPr)) at room temperature readily generated the corresponding CpPN-type bis(alkyl) complexes 1 and 2a–2c. Addition of 3 equiv of LiCH2SiMe3 to a mixture of L1(iPr) and LnCl3(thf)2 (Ln = Sm and Nd) also afforded the CpPN-type bis(alkyl) complexes 2d and 2e. The Cp moiety bonds to the central metal in a classical η5 mode in all CpPN-type complexes 1 and 2. In contrast, the CpMePN-type ligands C5Me4H–PPh2═N–C6H3R2 (R = Me, L2(Me); R = iPr, L2(iPr)) behaved differently. L2(Me) did not react with Sc(CH2SiMe3)3(thf)2. Similarly, L2(iPr) was also inert to Sc(CH2SiMe3)3(thf)2 even at 50 °C. When the central metal was changed to yttrium, however, the equimolar reaction between Y(CH2SiMe3)3(thf)2 and L2(iPr) in the presence of LiCl afforded two bis(alkyl) complexes 3a and 3b. In the main product 3a, [C5HMe3(η3-CH2)–PPh2═N–C6H3iPr2]Y(CH2SiMe3)2(thf), the ligand bonds to the Y3+ ion in a rare η3-allyl/κ-N mode, whereas in 3b, (C5Me4–PPh2═N–C6H3iPr2)Y(CH2SiMe3)2(LiCl)(thf), the Cp ring coordinates to the Y3+ ion in an η5 mode, and a LiCl unit is located between the Y3+ ion and the nitrogen atom. When the central metal was changed to lutetium, a bis(alkyl) complex 4a, [C5HMe3(η3-CH2)–PPh2═N–C6H3iPr2]Lu(CH2SiMe3)2(thf), and a bis(alkyl) complex 4b, (C5Me4–PPh2═N–C6H3iPr2)Lu(CH2SiMe3)2, were isolated. The protonolysis reaction of the IndPN-type ligands C9H7–PPh2═N–C6H3R2 (R = Me, L3(Me); R = Et, L3(Et); R = iPr, L3(iPr)) with Ln(CH2SiMe3)3(thf)2 (Ln = Sc, Y, and Lu) generated the IndPN-type bis(alkyl) complexes 5a–5c, 6, and 7a–7c, selectively, where the Ind moiety tends to adopt an η3-bonding fashion. The more bulky FluPN-type ligands C13H9–PPh2═N–C6H4R (R = H, L4(H); R = Me, L4(Me)) were treated with Ln(CH2SiMe3)3(thf)2 (Ln = Sc and Lu) to afford the FluPN-type bis(alkyl) complexes 8 and 9a and 9b, where the Flu moiety has a rare η1-bonding mode. Complexes 1–9 were fully characterized by 1H, 13C, and 31P NMR; X-ray; and elemental analyses. Upon activation with AlR3 and [Ph3C][B(C6F5)4], the scandium complexes showed good to high catalytic activity for ethylene polymerization. The effects of the sterics and electronics of the ligand, the loading and the type of AlR3, the polymerization temperature, and the polymerization time on the catalytic activity were also discussed.

One frontier of the rare-earth organometallic chemistry: The chemistry of rare-earth metal alkylidene, imido and phosphinidene complexes

The transition metal complexes, which contain M=E (E = C, N, P) double bond, are very important. Not only the understanding of the nature of transition metal-main group element double bond is of fundamental concern, but also these complexes have some excellent and unique reactivities. Rare-earth metal alkyl, amide and phosphide complexes have been extensively studied during the last three decades. However, the chemistry of rare-earth metal alkylidene, imido and phosphinidene complexes remain challenging. The efforts in this field led to some bridged alkylidene, imido and phosphinidene complexes, and phosphorus-stabilized “pincer” type alkylidene complexes. Although these reported complexes are different from their “terminal” cousins, which contain M=E (E = C, N, P) double bond, they shed light on the exploration to rare-earth metal terminal alkylidene, imido and phosphinidene complexes. This paper covers the synthesis, structures and reactivities of the bridged alkylidene, imido and phosphinidene complexes, phosphorus-stabilized “pincer” type alkylidene complexes as well as a recent breakthrough in the rare-earth metal terminal imido complexes.

C–H bond activation of N-heterocyclic carbene IMes by rare-earth metal alkyl complexes

Excess N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) reacted with the tris(trimethylsilylmethyl) rare-earth metal complex [Ln(CH 2SiMe 3) 3(THF) 2] (Ln = Y, Lu) in toluene to give a C 2-symmetric mono(trimethylsilylmethyl) complex with two IMes’ ligands [Ln(CH 2SiMe 3)(IMes’) 2] (IMes’ = IMes deprotonated at the ortho-methyl group of the mesityl substituent), formed by C–H bond activation of the mesityl substituents’ ortho-methyl groups. With one equivalent of IMes in THF, a mono-activated product [Ln(CH 2SiMe 3) 2(IMes’)(THF) n] is selectively formed. The molecular structure of the lutetium compound [Lu(CH 2SiMe 3) 2(IMes’)(THF)] in the crystal shows a strongly distorted trigonal bipyramid with a strained chelate ligand IMes’.