Metal Amido Complexes Research Articles

Coinage metal amido and thiolate SNS complexes: consequences of catalyst speciation in Cu(I)-catalysed carbonyl hydroboration.

Three new IPr-Ag- and -Au-SNS amido and thiolate complexes were synthesized and compared to their previously reported Cu analogues as carbonyl hydroboration catalysts (IPr = bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Although these complexes showed no catalytic activity, treatment of the IPr-Ag-SNS amido complex with pinacolborane released the N-borylated ligand, SMeNBpinSMe, (L1-Bpin). This finding led us to reinvestigate the IPr-Cu-SNS amido precatalyst, revealing that immediate loss of L1-Bpin converts our catalyst system to [CuH(IPr)]2.

Ether/Thioether-Functionalized Dianionic α-Iminopyridine Rare-Earth Metal Amido Complexes and Their Catalytic Activity toward Hydrophosphination of Alkenes

The double deprotonation of 2-aminomethyl pyridine by rare-earth metal triamido complexes was found to be an alternative strategy to anchor dianionic iminopyridine on rare-earth metal centers with the morpholinyl group previously. To verify the generality of the protocol with different appendant donor groups, reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with ether/thiotether-substituted 2-aminomethyl pyridine 2-(CH3DCH2CH2NHCH2)-6-R-C5H3N (D = O, R = H (1), Ph (2); D = S, R = H (3)) were performed, leading to the formation of ether/thioether-functionalized dianionic α-iminopyridine rare-earth metal amido complexes {μ-η2:σ1:κ1:κ1-2-[CH3ECH2CH2NCH]-6-R-C5H3N}2RE2[N(SiMe3)2]2 (D = O, R = H, RE = Dy (4a), Y (4b), Er (4c), Yb (4d), Lu (4e), R = Ph, RE = Dy (5a), Y (5b), Er (5c), Lu (5d); D = S, R = H, RE = Y (6a), Er (6b), Lu (6c)). These results supported the ability of oxygen or sulfur coordination in promoting the double deprotonation of 2-aminomethyl pyridine to construct new iminopyridine rare-earth metal complexes in the dianionic form. Further examination of these rare-earth metal amido complexes displayed good catalytic activity for hydrophosphination of alkenes, affording anti-Markovnikov addition products under solvent-free conditions.

Synthesis and Characterization of Rare-Earth Metal Complexes Bearing a 2-N,N-Dimethylamino-Ethylene-Imino-Functionalized Indolyl Ligand and Their Catalytic Activities Toward Hydrosilylation of Imines

The reactions of 2-N,N-dimethylamino-ethylene-imino-functionalized indolyl proligand 2-(Me2NCH2CH2N = CH)C8H5NH (HL) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 in toluene afforded a series of rare-earth metal amido complexes [κ3-(N,N,N)-2-(Me2NCH2CH2N = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Y (1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)). While the reaction of HL with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 produced the europium(II) complex in a dimeric form [{(η5-μ-η1:η1:η1)-2-(Me2NCH2CH2N═CH)C8H5N}Eu{N(SiMe3)2}]2 (2), which is believed to have happened through the homolysis of the Eu–N bond. Further reaction of complex 1a with PhCH═NPh provided an unexpected rare-earth metal complex [κ2-(N,N)-PhN{PhCH(CH2SiMe2)}N(SiMe3)]YL (7) through the sp3 C–H bond activation of the methyl on the silicon atom to form a Y–C bond followed by the insertion of the C═N bond of the imine PhCH═NPh to form an amido group connected to the central metal. All complexes were characterized by spectroscopic methods, elemental analyses, and single-crystal X-ray diffraction, and complexes 1a–1c and 7 were additionally characterized by NMR spectroscopy. The catalytic performance of complexes 1a–1g for the hydrosilylation of imines was investigated, and the catalytic mechanism was proposed based on the experimental results.

Hydroaminoalkylation of alkenes using transition metals complexes grafted on silica SBA15 as catalysts

The gas-phase hydroaminoalkylation reaction of propene catalyzed by group 4 (M = Ti, Zr and Hf) metal amido complexes [(≡Si–O-)(M(-NMe2)3] was investigated by using PBE0-D3/SVP//TZVP level of theory. The geometrical analysis traced the formation of the metallaaziridines and the azametallacyclopentanes as key intermediates in these reactions. The metallaaziridines were simulated through the activation of α-C-H bonds of the amido groups; while the azametallacyclopentanes were configured by slotting the propene double bond onto the M − C bonds of the metallaaziridines. The latter reaction was considered the rate-determining step. Thermochemical calculations showed that the order of catalytic activity is: Ti ≥ Zr > Hf; while the preference of the azametallacyclopentanes is: Hf > Zr ≥ Ti.

Role of Temperature, Pressure, and Surface Oxygen Migration in the Initial Atomic Layer Deposition of HfO2on Anatase TiO2(101)

The atomic layer deposition of HfO2 on a TiO2(101) surface from tetrakis(dimethylamido)hafnium and water is investigated using a combination of in situ vacuum X-ray photoelectron spectroscopy (XPS) and time-resolved ambient pressure XPS. Precursor pressures and surface temperature are tuned as to map the space state of the deposition. In the initial stages of ALD, a reaction mechanism based on dissociative adsorption dominates over a classic ligand exchange mechanism, typically evoked when metal-amido complexes and water are used as the precursors for metal oxide ALD. Surface species, including a dimethyl ammonium ion and an imine, are identified. It is found that they can be formed only if the active role of the TiO2(101) surface is taken into consideration. The temperature of the surface enhances the formation of these species based on an insertion reaction of a hydrogen atom, which then assists the formation of more than the expected monolayer of HfO2. A HfO2 overlayer is produced already during the first half-cycle, enabled by a reduction of the TiO2 support. Dosing water at high pressure allows hydroxyl formation, which marks the transition toward a well-described ligand exchange reaction type. From the experiments performed, we find that the ALD of HfO2 at room temperature, performed at high pressure, is mainly based on dissociation and that no side reaction occurs. These insights into the ALD reaction mechanism highlight how in situ studies can help understand how deposition parameters affect the growth of HfO2 and how the ALD model for transition metal oxide formation from amido complexes and water can be extended.

Continuous Flow Synthesis of NHC‐Coinage Metal Amido and Thiolato Complexes: A Mechanism‐based Process Development

AbstractThe first continuous flow syntheses of amido and thiolato families are reported. Our studies focused on [M(NHC)(Cbz)] (Cbz=carbazolyl) and [M(NHC)(SPh)] (NHC=N‐heterocyclic carbene) as general proof‐of‐concepts and has led to a simple protocol with unprecedented short reaction times and high product yields. The scope of supporting ligands and substrates permits to assess the versatility of the process and a one‐pot synthesis starting from the imidazolium salt, metal source and carbazole substrate highlights the simplicity and sustainability of this operating design. The process was made possible through a detailed mechanistic understanding of the underlying reaction chemistry.

Syntheses and structures of bimetallic rare-earth complexes supported by pyrrolyl ligands and their high performance in isoprene polymerization

• A series of the pyrrolyl-ligated bimetallic rare earth metal amido complexes were synthesized and characterized. • Complexes used as catalyst for the polymerization of isoprene. • They were to be highly cis-1,4 selective for isoprene polymerization. The reactions of pyrrole with rare-earth metal amides [(Me 3 Si) 2 N] 3 RE( μ -Cl)Li(THF) 3 produced the bimetallic rare earth metal amido complexes (RE = Y( 1 ), Nd( 2 ), Yb( 3 )) in high yields. X-ray diffraction analysis revealed that the pyrrole was deprotonated with the pyrrolyl ring coordinated to one rare-earth metal in an η 5 mode and the nitrogen atom coordinated to another rare-earth metal in an η 1 modes forming the centrosymmetric structures. Complexes 1 – 3 as precatalysts for isoprene polymerization were investigated. Results showed that except for ytterbium system, all other complexes could initiate effectively the polymerization of isoprene to afford polyisoprene with high conversion, high regio- and stereo-selectivity (1,4- cis selectivity up to 95.2%) in the presence of cocatalysts. A types of pyrrolyl-ligated bimetallic rare earth metal amido complexes were constructed, and their coordinated modes and catalytic activity were studied.

Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen.

The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element-hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element-hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol-1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry.

Synthesis, structure and catalytic activity of rare-earth metal amino complexes incorporating imino-functionalized indolyl ligand

The reactions of the imino-functionalized indolyl ligand (HL, L = 3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5N) with the rare-earth metal amides [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 producing different types of rare-earth metal amido complexes were investigated. The reactions of HL with 1 equiv. of [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 generated a series of hetero-nuclear bimetallic rare-earth metal amino complexes {[η1:µ-η2-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5]RE[N(SiMe3)2]2(µ-Cl)Li(THF)} (RE = Y(1), Sm(2), Gd(3), Er(4), Yb(5)). By extending the reaction time, only the reaction of HL with [(Me3Si)2N]3Gd(µ-Cl)Li(THF)3 gave an unexpected binuclear rare-earth metal complex {[(µ-η5:η1):η1:η1-3-[(Me2N)2-C14H9]-(NCH2CH2-C8H5N)2]Gd2[N(SiMe3)2]3} (6) incorporating a novel polycyclic ligand through C-C and C-N coupling. Treatment of HL with [(Me3Si)2N]3Sm(µ-Cl)Li(THF)3 in a 2:1 ratio generated the bis(indolyl) heteronuclear bimetallic rare-earth metal amino complex {(η1:η1-[µ-η2:η1-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5]Li[µ-η2:η1-3-(4-Me2N-C6H4CH=N-CH2CH2)C8H5])Sm[N(SiMe3)2]2} (7) in low yield probably due to accompanying with the formation of the complex 2. The above results indicated that reaction conditions play important roles in the formation of different coordination modes of the imino-functionalized indolyl rare-earth metal amido complexes. All new complexes 1−7 are fully characterized including X-ray structural determination. The catalytic activity of complexes 1-7 for the addition of amines to carbodiimides was explored. The results showed that all complexes displayed an excellent activity towards the addition of amines to carbodiimides producing guanidine under solvent-free condition.

Cis-1,4-Polymerization of isoprene catalyzed by rare-earth metal amido complexes supported by 2-t-butylimino- or 2-amino-functionalized indolyl ligand

Aiming at developing highly efficient and more conveniently treated rare-earth metal catalyst systems, the performance of a series of the rare-earth metal amido complexes bearing 2-t-butylimino- or 2-amino-functionalized indolyl ligands as precatalysts toward isoprene polymerization was investigated. Under the activation of borate activator [Ph3C][B(C6F5)4] and AlR3, the monomeric bis(amido) complexes [2-(tBuN = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Er (1), Y (2), Sm (3), Nd (4)) and the dinuclear complex {[µ-η5:η1:η1-2-(2,6-iPr2C6H3NCH2)C8H5N]Nd[N(SiMe3)2]}2 (5) exhibit different catalytic activities and cis-1,4-selectivities for isoprene polymerization depending on cocatalysts of aluminum alkyls, central rare-earth metals and the solvents. Among them, the homogeneous ternary system Nd complex 4 or 5/ [Ph3C][B(C6F5)4]/AliBu3 could very efficiently catalyze polymerization of isoprene under the relatively mild conditions to afford the cis-1,4-polyisoprenes (up to 98.3%) with high number-average molecular weights and narrow to moderate molecular weight distributions.

Syntheses of Dianionic α-Iminopyridine Rare-Earth Metal Complexes and Their Catalytic Acitivities toward Dehydrogenative Coupling of Amines with Hydrosilanes.

Reactions of [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with aminomethylene-substituted pyridine 2-[O(CH2CH2)2NCH2CH2NCH2]C5H4N (1) gave the dianionic α-iminopyridine rare-earth metal amido complexes {μ-η2:σ1:κ1:κ1-2-[O(CH2CH2)2NCH2CH2NCH]C5H4N}2RE2[N(SiMe3)2]2 (RE = Y(2a), La(2b), Pr(2c), Nd(2d), Sm(2e), Dy(2f), Er(2g), and Lu (2h)). However, reaction of [(Me3Si)2N]3Y(μ-Cl)Li(THF)3 with pyridin-2-ylmethyl-substituted amines such as 2-(RNHCH2)C5H4N (R = tBu (3a) and 2,6-iPr2Ph (3b)) or benzyl-substituted amine O(CH2CH2)2NCH2CH2NHCH2C6H5 (5) afforded the corresponding yttrium complexes containing monoanionic ligands [2-(RNCH2)C5H4N]2YN(SiMe3)2 (R = tBu (4a) and 2,6-iPr2Ph (4b)) or [O(CH2CH2)2NCH2CH2NCH2C6H5][(Me3Si)2N)]Y(μ-Cl)(μ-η3-O(CH2CH2)2NCH2CH2NCH2C6H5)Li(THF) (6). Dianionic α-iminopyridine rare-earth metal amido complexes showed high catalytic activities for the dehydrogenation coupling reaction of hydrosilanes and amines providing a variety of silylamines in high yields.

Synthesis and characterization of 2-t-butylimino-functionalized indolyl rare-earth metal amido complexes for the catalytic addition of terminal alkynes to carbodiimides: the dimeric complexes with the alkynide species in the μ-η1:η2 bonding modes.

A series of new rare-earth metal amido complexes bearing a 2-t-butylimino-functionalized indolyl ligand were synthesized via dehydrogenation of a secondary amine, and their reactivities and catalytic performances were investigated. The reactions of 2-(tBuNHCH2)C8H5NH (1) with rare-earth metal amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 afforded the complexes [2-(tBuN[double bond, length as m-dash]CH)C8H5N]RE[N(SiMe3)2]2 (RE = Er (2), Y (3), Dy (4), Sm (5), Nd (6)) containing the bidentate ligand via dehydrogenation of the amine to the imine group. Complexes 2-6 exhibited an excellent catalytic activity for the addition of terminal alkynes to carbodiimides affording a series of corresponding N,N'-dialkyl-propiolamidines. The catalysts can also be efficiently used for the preparation of the sterically bulky N,N'-diaryl-propiolamidine. Furthermore, the dimeric complexes {(μ-η1:η2-RC[triple bond, length as m-dash]C)RE[2-(tBuN[double bond, length as m-dash]CH)C8H5N]2}2 (11: RE = Y, R = Ph; 12: RE = Yb, R = SiMe3), with the alkynyl ligand in the μ-η1:η2 haptic modes, were isolated in attempts to study the catalytic mechanism.

Well-Defined Amidate-Functionalized N-Heterocyclic Carbene -Supported Rare-Earth Metal Complexes as Catalysts for Efficient Hydroboration of Unactivated Imines and Nitriles

Four amidate-functionalized N-heterocyclic carbene (NHC) rare-earth metal amido complexes [(κ2-N,O-κ1-L)2REN(SiMe3)2] (L = 1-(C6H5C═ONCH2CH2)-3-(CH3)3C6H2(N(CH)2NC)) [RE = Er (1), Y (2), Dy (3), Gd (4)] were synthesized by one-pot reactions of 2 equiv of (1-(C6H5C═ONHCH2CH2)-3-(CH3)3C6H2-(N(CH)2NCH))Br (H2LBr) with 5 equiv of KN(SiMe3)3 followed by treatment with 1 equiv of RECl3 in tetrahydrofuran at -40 °C. These complexes were fully characterized, and their catalytic activities toward hydroboration of unactivated imines and nitriles were investigated, and it was found that these complexes displayed excellent activities as well as remarkable functional group compatibility for imine and nitrile substrates such as halo-, alkyl-, hydroxyl-, N, N-dimethylamino-, and nitro- substituents. Among those, the chemoselectivity for this reaction among the common unsaturated functional groups was achieved in the order C═O ≫ C═N > C≡N > CO2Et > C═C in the current catalytic system, which may facilitate their further application in synthetic chemistry.

Reactivity of functionalized indoles with rare-earth metal amides. Synthesis, characterization and catalytic activity of rare-earth metal complexes incorporating indolyl ligands.

The reactivity of several functionalized indoles 2-(RNHCH2)C8H5NH (R = C6H5 (1), (t)Bu (2), 2,6-(i)Pr2C6H3 (3)) with rare-earth metal amides is described. Reactions of 1 or 2 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Eu, Yb) respectively produced the europium complexes [2-(C6H5N[double bond, length as m-dash]CH)C8H5N]2Eu[N(SiMe3)2] (4) and [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]Eu[N(SiMe3)2]2 (5), and the ytterbium complex [2-((t)BuN[double bond, length as m-dash]CH)C8H5N]2Yb[N(SiMe3)2] (6), containing bidentate anionic indolyl ligands via dehydrogenation of the amine to the imine. In contrast, reactions of the more sterically bulky indole 3 with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 afforded complexes [2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2](THF)2 (RE = Yb (7), Y (8), Er (9), Dy (10)) with the deprotonated indolyl ligand. While reactions of 3 with yttrium and ytterbium amides in refluxing toluene respectively gave the complexes [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]3Y (11) and [2-(2,6-(i)Pr2C6H3N[double bond, length as m-dash]CH)C8H5N]2Yb(II)(THF)2 (12), along with transformation of the amino group to the imino group, and also with a reduction of Yb(3+) to Yb(2+) in the formation of 12. Reactions of 3 with samarium and neodymium amides provided novel dinuclear complexes {[μ-η(5):η(1):η(1)-2-(2,6-(i)Pr2C6H3NCH2)C8H5N]RE[N(SiMe3)2]}2 (RE = Sm (13), Nd (14)) having indolyl ligands in μ-η(5):η(1):η(1) hapticities. The pathway for the transformation of the amino group to the imino group is proposed on the basis of the experimental results. The new complexes displayed excellent activity in the intramolecular hydroamination of aminoalkenes.

CNC-Pincer Rare-Earth Metal Amido Complexes with a Diarylamido Linked Biscarbene Ligand: Synthesis, Characterization, and Catalytic Activity

In preparation of CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand, it is found that conditions have a key influence on final products. Reaction of a THF suspension of bis[2-(3-benzylimidazolium)-4-methylphenyl]amine dichlorides (H3LCl2) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Yb, Eu, Sm) in THF at room temperature afforded the only unexpected fused-heterocyclic compound 8,9-dibenzyl-3,14-dimethyl-8a,9-dihydro-8H-benzo[4,5]imidazo[2′,1′:2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline (1) containing an imidazolyl ring and a piperidyl ring, which formed through carbene C–C and C–N coupling. However, the reaction of H3LCl2 with [(Me3Si)2N]3Er(μ-Cl)Li(THF)3 in toluene afforded the CNC-pincer erbium amido complex incorporating a diarylamido linked biscarbene ligand LEr[N(SiMe3)2]2 (2) in low yield and the above fused-heterocyclic compound 1. The stepwise reaction of H3LCl2 with strong bases (n-BuLi or LiCH2SiMe3) in THF for 4 h, followed by treatment with [(Me3Si)2N]3RE(μ-Cl)...

Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ–η5:η1bonding indolyl and μ3-oxo groups

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75-80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ-η(5):η(1) bonding modes and a μ3-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η(1) bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C-P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.

Dispersion Force Stabilized Two-Coordinate Transition Metal–Amido Complexes of the −N(SiMe3)Dipp (Dipp = C6H3-2,6-Pri2) Ligand: Structural, Spectroscopic, Magnetic, and Computational Studies

A series of high spin, two-coordinate first row transition metal-amido complexes, M{N(SiMe3)Dipp}2 {M = Fe (1), Co (2), or Ni (3); Dipp = C6H3-2,6-Pr(i)2} and a tetranuclear C-H activated chromium amide, [Cr{N(SiMe2CH2)Dipp}2Cr]2(THF) (4), were synthesized by reaction of their respective metal dihalides with 2 equiv of the lithium amide salt. They were characterized by X-ray crystallography, electronic and infrared spectroscopy, SQUID magnetic measurements, and computational methods. Contrary to steric considerations, the structures of 1-3 display planar eclipsed M{NSiC(ipso)}2 arrays and short M-N distances. DFT calculations, corrected for dispersion effects, show that dispersion interactions involving C-H-H-C moieties likely stabilize the structures by 21.1-29.4 kcal mol(-1), depending on the level of the calculations employed. SQUID measurements confirm high spin electron configurations for all the complexes and substantial orbital contributions for 1 and 2.

Rare-earth metal amido complexes supported by bridged bis(β-diketiminato) ligand as efficient catalysts for hydrophosphonylation of aldehydes and ketones

A series of rare-earth metal amides supported by a cyclohexyl-linked bis(β-diketiminato) ligand were synthesized, and their catalytic activities for hydrophosphonylation of aldehydes and ketones were developed. Reaction of [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 with the cyclohexyl-linked bis(β-diketimine) H2L (1) (L = Cy[NC(Me)CHC(Me)NAr]2, Cy = cyclohexyl, Ar = 2, 6-i-Pr2C6H3) gave the rare-earth metal amides LREN(SiMe3)2 (RE = Nd(2), Sm(3), Dy(4), Er(5), Y(6)). All complexes were fully characterized by elemental, spectroscopic and single-crystal X-ray analyses. Investigation of the catalytic properties of the complexes reveals that these complexes exhibited a high catalytic activity towards the hydrophosphonylation of aldehydes and ketones in the presence of a very low loading of rare-earth metal amides (0.1–1 mol%) at room temperature in a short time.

Highly Efficient Hydrophosphonylation of Aldehydes and Unactivated Ketones Catalyzed by Methylene‐Linked Pyrrolyl Rare Earth Metal Amido Complexes

A series of rare earth metal amido complexes bearing methylene-linked pyrrolyl-amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent-free conditions for liquid substrates. Treatment of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) with 2-(2,6-Me(2)C(6)H(3)NHCH(2))C(4)H(3)NH (1, 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ-η(5):η(1)):η(1)-2-[(2,6-Me(2)C(6)H(3))NCH(2)](C(4)H(3)N)LnN(SiMe(3))(2)}(2) [Ln=Y (2), Nd (3), Sm (4), Dy (5), Yb (6)] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by (1)H NMR spectroscopic analyses. The structures of complexes 2, 3, 4, and 6 were determined by single-crystal X-ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol%) afforded the products in high yields (up to 99%) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99% with employment of low loadings (0.1 to 0.5 mol%) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α-hydroxy diaryl phosphonates in moderate to high yields.

Synthesis of an iridium porphyrin amido complex

A synthetic route for iridium porphyrin amido complexes has been established. Treatment of a THF solution of Ir(ttp)(CO)Cl (1) (ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) with an aqueous mixture of NaOH and NaBH4, followed by 2-iodoethanol leads to the clean formation of the β-hydroxyethyl complex Ir(ttp)(C2H4OH) (2) in 92% yield. Heating a pyridine solution of complex 2 in the presence of ca. 5–10 equiv. of phthalimide (HNC8H4O2; HPhth) leads to the formation of Ir(ttp)(C5H5N)(CH2CH2Phth) (3). The replacement of pyridine by THF as the reaction solvent leads to the formation of the THF adduct Ir(ttp)(THF)(Phth) (4), which has been characterized spectroscopically. Heating a solution of 4 in pyridine leads to the formation of Ir(ttp)(C5H5N)(Phth) (5), which has been isolated in 72% yield. Complexes 3 and 5 have been characterized by X-ray crystallographic studies. Complexes 4 and 5 are rare examples of monomeric late transition metal-amido complexes and are the first examples of iridium-amido complexes featuring a porphyrin as a supporting ligand.