Guanidinato Ligands Research Articles

Reactivity of a mixed methyl-aminobenzyl guanidinate lutetium complex towards iPrNCNiPr, CS2 and Ph2PH.

A heteroleptic terminal alkyl lutetium complex stabilized by a bulky guanidinato ligand, LLu(CH2C6H4NMe2-o)(Me)(THF) (1) (L = (PhCH2)2NC(NC6H3iPr2-2,6)2) has been synthesized by the treatment of LLu(CH2C6H4NMe2-o)2 with AlMe3 (1 equiv.) via an alkyl-exchange reaction in toluene/THF (4 : 1) solution and fully characterized. The difference in the activities of aminobenzyl and methyl was also proven through their selective reactivity, including complex 1 with one equivalent of DIC, CS2 and HPPh2, to afford complexes LLu[(NiPr2)2CMe](CH2C6H4NMe2-o) (2), L2Lu2[μ-η1:η2-S2CCHC6H4NMe2-o][μ-η2:η2-S2CCHC6H4NMe2-o](THF) (4), and {LLu(Me)[μ-O(CH2)4 PPh2]}2 (5), respectively. The subsequent transformations have also been investigated, obtaining complexes LLu[(NiPr2)2CMe][(NiPr2)2C CH2C6H4NMe2-o] (3), {LLu[O(CH2)4PPh2][μ-O(CH2)4PPh2]}2 (6) and dimeric lutetium phosphide {LLu[μ-O(CH2)4PPh2]}2(Me)(PPh2) (7). In addition, the guanidinate bimetallic alkynyl-bridged lutetium complex [LLu(μ-CCPh)]2(μ-η2:η2-PhC4Ph) (8) bearing the μ2-butatrienediyl group was obtained from the reaction of 1 with PhCCH (2 equiv.). The guanidinate lutetium μ-imido complex [LLu(μ-NPh)(THF)]2 (10) was also obtained in good yield by the treatment of 1 with PhNH2.

Synthesis and Characterization of Tungsten Nitrido Amido Guanidinato Complexes as Precursors for Chemical Vapor Deposition of WNxCy Thin Films.

Tungsten nitrido amido guanidinato complexes of the type WN(NR2)[(NR')2C(NR2)]2 (R = Me, Et; R' = i Pr, Cy) were synthesized as precursors for aerosol-assisted chemical vapor deposition (AACVD) of WNxCy thin films. The reaction of tungsten nitrido amido complexes of the type WN(NR2)3 (R = Me, Et) with two equivalents of a carbodiimide R'N=C=NR' (R' = i Pr, Cy) resulted in two insertions of a carbodiimide into W-N(amido) bonds, affording bis(guanidinato) amido nitrido tungsten complexes. These compounds were characterized by 14N NMR, indicating distinctive chemical shifts for each type of N-bound ligand. Crystallographic structure determination of WN(NMe2)[(N i Pr)2C(NMe2)]2 showed the guanidinato ligands to be non-equivalent. The complex WN(NMe2)[(N i Pr)2C(NMe2)]2 was demonstrated to serve as a precursor for AACVD of WNxCy thin films, resulting in featureless, X-ray amorphous thin films for growth temperatures 200 - 400 °C.

Bis(amidinato)- and bis(guanidinato)silylenes and silylenes with one sterically demanding amidinato or guanidinato ligand: synthesis and reactivity.

This article deals with the synthesis and reactivity of the bis(amidinato)silylene [iPrNC(Ph)NiPr]2Si (5), the bis(guanidinato)silylene [iPrNC(NiPr2)NiPr]2Si (6), the mono(amidinato)silylene [DippNC(Ph)NDipp]SiNMe2 (Dipp = 2,6-diisopropylphenyl) (8) and the mono(guanidinato)silylene [DippNC(NMe2)NDipp]SiN(SiMe3)2 (9). The reactions studied include (i) nucleophilic substitutions, (ii) Lewis acid/base reactions, (iii) Brønsted acid/base reactions, (iv) oxidative additions (bond activations, small-molecule activations), (v) cycloaddition reactions with unsaturated organic substrates, (vi) reductions and (vii) radical formation by muonium addition. Silylenes 5, 6, 8 and 9 have been demonstrated to display unique reactivity profiles and to be versatile precursors for the synthesis of novel four- or five-coordinate silicon(ii) and four-, five- or six-coordinate silicon(iv) complexes with unprecedented structural motifs. This article also deals with the structural characterisation of all the new silicon(ii) and silicon(iv) compounds synthesised. Crystal structure analyses and 29Si NMR spectroscopic studies in the solid state and in solution were used to characterise the silicon coordination polyhedra of these compounds.

Iron(II), Cobalt(II), Nickel(II), and Zinc(II) Silylene Complexes: Reaction of the Silylene [iPrNC(NiPr2 )NiPr]2 Si with FeBr2 , CoBr2 , NiBr2 ⋅MeOCH2 CH2 OMe, ZnCl2 , and ZnBr2.

Reaction of the donor-stabilized silylene [iPrNC(NiPr2 )NiPr]2 Si (1) with FeBr2 , CoBr2 , NiBr2 ⋅MeOCH2 CH2 OMe, ZnCl2 , and ZnBr2 afforded the respective transition-metal silylene complexes 4-8, the formation of which can be described in terms of a Lewis acid/base reaction (4, 5, 7, 8) or a nucleophilic substitution reaction (6). However, the reactivity profile of silylene 1 is not only based on its strong Lewis base character; the different coordination modes of the two guanidinato ligands (4-6 vs. 7 and 8) add an additional reactivity facet. The paramagnetic compounds 4 and 5 and the diamagnetic compounds 6⋅THF, 7, and 8⋅0.5 Et2 O were structurally characterized by single-crystal X-ray diffraction. In addition, compound 6⋅THF was studied by 15 N and 29 Si solid-state NMR spectroscopy, and 7 and 8 were characterized by NMR spectroscopic studies in the solid state (15 N, 29 Si) and in solution (1 H, 13 C, 29 Si). Compounds 4-8 represent very rare examples of FeII , CoII , NiII , and ZnII silylene complexes. Four-coordinate silicon(II) compounds with an SiN3 M skeleton (M=Fe, Co, Ni) and M in the formal oxidation state +2 (4-6) have not yet been reported, and five-coordinate silicon(II) compounds with an SiN4 Zn skeleton (7, 8) are also unprecedented.

Synthesis, characterization, thermal properties of silicon(iv) compounds containing guanidinato ligands and their potential as CVD precursors

The title compounds of the type (Me3Si)2N–C(N′R)(–N′′RSiMe3) (with R = iPr or Cy) as potential CVD precursors have been synthesized and characterized by X-ray diffraction, 1H NMR, 13C NMR, 29Si NMR and elemental analysis where necessary.

Synthesis and structure of the first tin(II) amidinato-guanidinate [DippNC(nBu)NDipp]Sn{pTol-NC[N(SiMe3)2]N-pTol}

The preparation, via transmetallation reaction of an appropriate lithium precursor and a tin(II)-containing compound, spectral properties (1H and 119Sn NMR spectroscopy) and structure of the tin(II) complex [DippNC(nBu)NDipp]Sn{pTol-NC[N(SiMe3)2]N-pTol} containing both amidinato and guanidinato ligands is reported.

Donor‐Stabilized Silylenes with Guanidinato Ligands

AbstractThe first donor‐stabilized silylenes with guanidinato ligands, compounds 4 and 6, were synthesized and structurally characterized in the solid state and in solution. As demonstrated by single‐crystal X‐ray diffraction studies, compound 4 contains a bidentate and a monodentate guanidinato ligand of the type [iPrNC(NiPr2)NiPr]–, and compound 6 contains the bidentate guanidinato ligand [ArNC(NMe2)NAr]– (Ar = 2,6‐diisopropylphenyl) and the monodentate amido ligand [(Me3Si)2N]–. Both silicon(II) complexes exist also in solution.

The Ligand‐Based Quintuple Bond‐Shortening Concept and Some of Its Limitations

Herein, the ligand-based concept of shortening quintuple bonds and some of its limitations are reported. In dichromium-diguanidinato complexes, the length of the quintuple bond can be influenced by the substituent at the central carbon atom of the used ligand. The guanidinato ligand with a 2,6-dimethylpiperidine backbone was found to be the optimal ligand. The reduction of its chromium(II) chloride-ate complex gave a quintuply bonded bimetallic complex with a Cr-Cr distance of 1.7056 (12) Å. Its metal-metal distance, the shortest observed in any stable compound yet, is of essentially the same length as that of the longest alkane C-C bond (1.704 (4) Å). Both molecules, the alkane and the Cr complex, are of remarkable stability. Furthermore, an unsupported Cr(I) dimer with an effective bond order (EBO) of 1.25 between the two metal atoms, indicated by CASSCF/CASPT2 calculations, was isolated as a by-product. The formation of this by-product indicates that with a certain bulk of the guanidinato ligand, other coordination isomers become relevant. Over-reduction takes place, and a chromium-arene sandwich complex structurally related to the classic dibenzene chromium complex was observed, even when bulkier substituents are introduced at the central carbon atom of the used guanidinato ligand.

Guanidinato Complexes of Iridium: Ligand-Donor Strength, O2Reactivity, and (Alkene)peroxoiridium(III) Intermediates

A series of seven [Ir{ArNC(NR2)NAr}(cod)] complexes (1a-1g; where R = Me or Et; Ar = Ph, 4-MeC6H4, 4-MeOC6H4, 2,6-Me2C6H3, or 2,6-(i)Pr2C6H3; and cod = 1,5-cyclooctadiene) were synthesized by two different methods from the neutral guanidines, ArN═C(NR2)NHAr, using either MeLi and [{Ir(cod)}2(μ-Cl)2] or [{Ir(cod)}2(μ-OMe)2]. Reaction of 1a-1g with CO produced the corresponding [Ir{ArNC(NR2)NAr}(CO)2] complexes (2a-2g), which were characterized by NMR and solution- and solid-state IR spectroscopy. Complexes 1b (R = Et, Ar = Ph), 1d (R = Et, Ar = 4-MeC6H4), 1f (R = Me, Ar = 2,6-Me2C6H3), and 2b (R = Et, Ar = Ph) were characterized by X-ray crystallography as mononuclear complexes with a guanidinato-κ(2)N,N' ligand and a cod or two CO ligands coordinated to the Ir center in a distorted square-planar environment. On the basis of the CO stretching frequencies of 2a-2g [avg. νCO (n-pentane) = 2016-2019 cm(-1)] and the alkene (13)C chemical shifts of 1a-1g [δ((13)CC═C) = 58.7-61.0 ppm], the donor strength of the guanidinato ligands was evaluated and compared to that of related monoanionic ligands. Reaction of 1a-1g in solution with O2 at 20 °C afforded (alkene)peroxoiridium(III) intermediates, [Ir{ArNC(NR2)NAr}(cod)(O2)] (3). The steric properties of the supporting ligand play a decisive role in O2 binding in that complexes without ortho substituents react largely irreversibly with O2 (1a-1e; where Ar = Ph, 4-MeC6H4 or 4-MeOC6H4), whereas complexes with ortho substituents exhibit fully reversible O2 binding (1f and 1g; where Ar = 2,6-Me2C6H3 or 2,6-(i)Pr2C6H3). Complexes 3a-3f were characterized by (1)H NMR and IR spectroscopy (νOO = 857-872 cm(-1)). Decay of the new intermediates and subsequent reaction with cod produced 4-cycloocten-1-one and the respective Ir(I) precursor.

1,1-(Butane-1,4-diyl)-2,3-dicyclohexylguanidinato]dimethylaluminum(III).

In the crystal structure of the title complex, [Al(CH3)2(C17H30N3)], the AlIII cation is coordinated by two methyl ligands and two N atoms from the guanidinato ligand in a distorted tetra­hedral geometry. The dihedral angle between the CN2 and AlC2 planes is 85.37 (2)°. The two N atoms of the guanidinato ligand exhibit an almost uniform affinity to the metal atom.

Synthesis, Characterization, and O2 Reactivity of Iridium(I) Complexes Supported by Guanidinato Ligands

Mononuclear [Ir{ArNC(NR(2))NAr}(C(8)H(12))] complexes (where R = Me or Et; Ar = Ph, 4-MeC(6)H(4), or 2,6-Me(2)C(6)H(3); and C(8)H(12) = 1,5-cyclooctadiene) were synthesized from the neutral N,N-dialkyl-N',N''-diarylguanidines via deprotonation and transmetalation. As confirmed by single-crystal structure determinations, the guanidinato(1-) ligands coordinate the low-valent d(8) Ir(I) center in an N,N'-chelating binding mode, and the (13)C NMR chemical shifts of the alkene carbon atoms establish that these ligands function as stronger donors than related monoanionic, bidentate nitrogen-based ligands. In the reactions of the complexes with O(2), the observed reactivity trends correlate with the electronic and steric influences of the substituents of the guanidinato ligands.

Synthesis, Characterization, and Thermal Properties of Homoleptic Rare-Earth Guanidinates: Promising Precursors for MOCVD and ALD of Rare-Earth Oxide Thin Films

Eight novel homoleptic tris-guanidinato complexes M[(N(i)Pr)(2)CNR(2)](3) [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), (i)Pr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the (i)Pr-Me(2)N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd(2)O(3) and Dy(2)O(3) thin films on Si(100) substrates. The MOCVD grown films of Gd(2)O(3) and Dy(2)O(3) were highly oriented in the cubic phase, while the ALD grown films were amorphous.

Deposition of WNxCy for diffusion barrier application using the imido guanidinato complex W(NiPr)Cl3[PriNC(NMe2)NiPr

A solution of the tungsten imido guanidinato complex W(NPri)Cl3[PriNC(NMe2)NPri] (1) in benzonitrile was used to deposit tungsten nitride carbide (WNxCy) thin films by chemical vapor deposition in the temperature range of 400–750°C. Films grown with 1 were composed of W, N, C, and O as determined by Auger electron spectroscopy. X-ray photoelectron spectroscopy results indicated that no Cl impurity was present in the film. The apparent activation energy in the reaction limited growth regime was 0.54eV. The films deposited below 500°C were amorphous, while films deposited at and above 500°C were nanocrystalline (grain size <50Å). The lowest resistivity of 0.98mΩcm was obtained for film deposited at 450°C. Films, 45–55nm thick, deposited at 450–500°C were able to prevent bulk Cu diffusion after vacuum annealing at 500°C for 30min. The properties of thin films deposited with 1 were compared to those from the isopropyl imido complex, Cl4(RCN)W(NPri) (2a, R=CH3, 2b, R=Ph), to provide insight into the effect of imido and guanidinato ligands on film properties.

Hydrido Complexes of Yttrium and Lutetium Supported by Bulky Guanidinato Ligands [Ln(μ‐H){(Me3Si)2NC(NCy)2}2]2 (Ln = Y, Lu): Synthesis, Structure, and Reactivity

AbstractLewis base free hydrido complexes of yttrium and lutetium supported by bulky cyclohexyl‐substituted guanidinato ligands, [Ln(μ‐H){(Me3Si)2NC(NCy)2}2]2 (Ln = Y, Lu), were synthesized and characterized. Single‐crystal X‐ray diffraction studies revealed dimeric structures. 1H NMR spectroscopy shows that complex [Y(μ‐H){(Me3Si)2NC(NCy)2}2]2 retains its dimeric structure in C6D6 solution. Scrambling of the hydrido complexes [Ln(μ‐H){(Me3Si)2NC(NCy)2}2]2 (Ln = Y, Lu) in C6D6 resulted in an equilibrium mixture containing the heterodimetallic species [{(Me3Si)2NC(NCy)2}2Y(μ‐H)2Lu{(Me3Si)2NC(NCy)2}2], indicating the dissociation of dimers and the presence of monomeric species in solution. Both compounds initiate the polymerization of ethylene: the activity of the cyclohexyl‐substituted yttrium complex, [Y(μ‐H){(Me3Si)2NC(NCy)2}2]2, is much lower than that of the isopropyl‐substituted analogue, [Y(μ‐H){(Me3Si)2NC(NiPr)2}2]2, while in the case of lutetium the activities of [Ln(μ‐H){(Me3Si)2NC(NR)2}2]2 (R = iPr, Cy) are similar. Complexes [Ln(μ‐H){(Me3Si)2NC(NR)2}2]2 (Ln = Y, Lu; R = iPr, Cy) were shown to catalyze efficiently the hydrosilylation of 1‐nonene with PhSiH3 (at a 1:1 substrates mol ratio) to give the terminal silane PhSiH2(n‐C9H19) exclusively. If the hydrosilylation reaction is carried out in the presence of a twofold molar excess of 1‐nonene, double addition takes place and leads to the formation of tertiary silane PhSiH(n‐C9H19)2, which was obtained in 96 % yield. The hydrido complexes [Ln(μ‐H){(Me3Si)2NC(NiPr)2}2]2 (Ln = Y, Lu) efficiently initiate the ring‐opening polymerization of ϵ‐caprolactone to give polymers with molar mass up to 80000.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Dependence of the mutual ligand arrangement in guanidinate complexes of lanthanoids on the ligand solid angles§

Mutual ligand arrangement in binuclear lanthanoid complexes of the type [Gu2Ln(μ-H)]2, [Gu2Ln(μ-Cl)]2, and Gu2Ln(μ-Cl)2Li(THF)2, where Gu is a substituted guanidinato ligand, is quantitatively analyzed based on the ligand solid angle approach. In complexes of Nd, Sm, and Gd the Gu ligands shield up to 87% of the metal and the bidentate ligands on opposite metal centers are in the eclipsed arrangement; in complexes of lanthanoids with smaller ionic radii Y, Yb, and Lu the Gu ligands shield over 88.3% of the metal surface and their staggered conformation is observed. The ligand solid angle approach is illustrated and its application to describing multidentate ligands is demonstrated. §Dedicated to Professor Georgy A. Domrachev on the occasion of his 70th birthday

Mixed Guanidinato/Alkylimido/Azido Tungsten(VI) Complexes: Synthesis and Structural Characterization

A series of structurally characterized new examples of pentacoordinated heteroleptic tungsten(VI)-guanidinates complexes are described. Starting out from [WCl(2)(Nt-Bu)(2)py(2)] (1) (py = pyridine) and the guanidinato transfer reagents (TMEDA)Li[(Ni-Pr)(2)CNi-Pr(2)] (2a) (TMEDA = N,N,N',N'-tetramethylethylendiamine) and [Li(NC(NMe(2))(2))](x) (2b), the title compounds [WCl(Nt-Bu)(2)[(Ni-Pr)(2)CNi-Pr(2)]] (3) and [W(Nt-Bu)(2)Cl{NC(NMe(2))(2)]](2) (6) were selectively formed by the elimination of one mole equivalent of lithium chloride. The isopropyl-substituted guanidinato ligand [(Ni-Pr)(2)CNi-Pr(2)} of monomeric 3 is N(1),N(3)-bonded to the tungsten center. The introduction of the sterically less-demanding tetramethyl guanidinato ligand [NC(NMe(2))(2)] expectedly leads to dimeric 6 exhibiting a planar W(2)N(2) ring with the guanidinato group bridging the two tungsten centers via the deprotonated imino N-atom. The remaining chloro ligand of 3 is labile and can be substituted by sterically less-crowded groups such as dimethylamido or azido that yield the presumably monomeric compounds 4 and 5, respectively. A similar treatment of 6 with sodium azide yields the dimeric azido derivative 7. Reacting [WCl(2)(Nt-Bu)(2)py(2)] directly with an excess of sodium azide leads to the dimeric bis-azide species [[W(Nt-Bu)(2)(N(3))(mu(2)-N(3))py](2)]. The new compounds were fully characterized by single-crystal X-ray diffractometry (except 2, 4, and 5), NMR, IR, and mass-spectroscopy as well as elemental analysis. Compound 5, [W(N(3))(Nt-Bu)(2)[(Ni-Pr)(2)CNi-Pr(2)]], can be sublimed at 80 degrees C, 1 Pa.

Synthesis and structural investigation of N,N',N' '-trialkylguanidinato-supported zirconium(IV) complexes.

The addition of 2 equiv of N,N',N' '-triisopropylguanidine (guanH(2)) to Zr(CH(2)Ph)(4) produced the bis(guanidinato)bis(benzyl)zirconium complex [((i)PrNH)C(N(i)Pr)(2)](2)Zr(CH(2)Ph)(2) (1). The mono(guanidinato) complex [((i)PrN)(2)C(NH(i)Pr)]ZrCl(3) (2) was accessible by the reaction of 2 equiv of guanH(2) with ZrCl(4). Guanidinium hydrochloride, [C(NH(i)Pr)(3)]Cl, is a byproduct of this reaction. When crystallized from THF, complex 2 was isolated as the THF adduct [((i)PrNH)C(N(i)Pr)(2)]ZrCl(3)(THF) (2-THF). The mixed cyclopentadienyl guanidinato complex [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrCl(2) (3) was prepared by treatment of [1,3-(Me(3)Si)(2)C(5)H(3)]ZrCl(3) with the in situ generated lithium triisopropylguanidinate salt. The reaction of guanH(2) with [1,3-(Me(3)Si)(2)C(5)H(3)]ZrMe(3) affords the dimethyl derivative [eta(5)-1,3-(Me(3)Si)(2)C(5)H(3)][((i)PrNH)C(N(i)Pr)(2)]ZrMe(2) (4). Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray characterization of 1, 2-THF, and 3, which are presented. The extent of pi delocalization within the guanidinato ligand is discussed in the context of the metrical parameters obtained from these structural studies.