Β-diketiminato Ligand Research Articles

Sterically crowded triazenides as novel ancillary ligands in copper chemistry

We have synthesized copper salts MN3RR′ derived from the biphenyl- or m-terphenyl-substituted triazenes Tph2N3H (1a) and Dmp(Tph)N3H (1b) (Dmp=2,6-Mes2C6H3 with Mes=2,4,6-Me3C6H2; Tph=2-TripC6H4 with Trip=2,4,6-i-Pr3C6H2). The homoleptic copper triazenide [CuN3Tph2] (2a) was obtained in high yield from the metallation of 1a with mesityl copper in n-heptane, while the complex [CuN3(Dmp)Tph] (2b) was generated by the same method in situ only. Reaction of 2a with triphenylphosphane gave the 2:1 adduct [CuN3Tph2(PPh3)2] (3a), regardless of the used complex/donor ratio, while reaction of 2a or 2b with a stochiometric amount of t-butylisonitrile afforded the 1:1 adducts [Tph2N3CuCNtBu] (4a) and [Dmp(Tph)N3CuCNtBu] (4b). All new compounds (except 2b) have been characterized by 1H NMR, 13C NMR and IR spectroscopy, elemental analysis, melting point (not 2a), and X-ray crystallography. The IR spectroscopic examination of the ν(CN) stretch in the isonitrile adducts 4a and 4b revealed the weaker donor character of the supporting triazenido ligands compared to related β-diketiminato ligands.

Synthesis and reactivity of cationic niobium and tantalum methyl complexes supported by imido and β-diketiminato ligands

The synthesis and reactivity of the cationic niobium and tantalum monomethyl complexes [(BDI)MeM(N(t)Bu)][X] (BDI = [Ar]NC(CH(3))CHC(CH(3))N[Ar], Ar = 2,6-(i)Pr(2)C(6)H(3); M = Nb, Ta; X = MeB(C(6)F(5))(3), B(C(6)F(5))(4)] was investigated. The cationic alkyl complexes failed to irreversibly bind CO but formed phosphine-trapped acyl complexes [(BDI)(R(3)PC(O)Me)M(N(t)Bu)][B(C(6)F(5))(4)] (R = Et, Cy) in the presence of a combination of trialkylphosphines and CO. Treatment of the monoalkyl cationic Nb complex with XylNC (Xyl = 2,6-Me(2)-C(6)H(3)) resulted in irreversible formation of the iminoacyl complex [(BDI)(XylN[double bond, length as m-dash]C(Me))Nb(N(t)Bu)][B(C(6)F(5))(4)], which did not bind phosphines but would add a methide group to the iminoacyl carbon to provide the known ketimine complex (BDI)(XylNCMe(2))Nb(N(t)Bu). Further stoichiometric chemistry explored i) migratory insertion reactions to form new alkoxide, amidinate, and ketimide complexes; ii) protonolysis reactions with Ph(3)SiOH to form thermally robust cationic siloxide complexes; and iii) catalytic high-density polyethylene formation mediated by the cationic Nb methyl complex.

Ligand-controlled synthesis of vanadium(i) β-diketiminates and their catalysis in cyclotrimerization of alkynes

Three dimeric vanadium(I) β-diketiminates [V{μ-(η(6)-ArN)C(Me)CHC(Me)C(N-Ar)}](2) (Ar = 2,6-Me(2)C(6)H(3) (2), 2,6-Et(2)C(6)H(3) (3), 9-anthracenyl (4)) were prepared and isolated upon reduction of their corresponding dichloro precursors VCl(2)(Nacnac). Compounds 2-4 all show a structure with each vanadium atom being η(2) bonded to the β-diketiminate framework and η(6) bonded to a flanking ring of a β-diketiminato ligand, attached to the other vanadium centre within the dimer. No metal-metal bonding interactions are observed in these dimers due to long vanadium-vanadium separations. Compounds 2-4 display an antiferromagnetic exchange between the two vanadium centres. An imido azabutadienyl complex (η(2)-PhCC(H)C(Ph)NC(6)H(3)-2,6-(i)Pr(2))VN(C(6)H(3)-2,6-(i)Pr(2))(OEt(2)) (5) was isolated from the reduction of VCl(2)(HC(C(Ph)NC(6)H(3)-2,6-(i)Pr(2))(2)) by KC(8). Compounds 2-4 and the inverted-sandwich divanadium complex (μ-η(6):η(6)-C(6)H(5)Me)[V(HC(C(Me)NC(6)H(3)-2,6-(i)Pr(2))(2))](2) (1) reduce Ph(2)S(2) to give two vanadium dithiolates V(SPh)(2)[(HC(C(Me)NC(6)H(3)-2,6-R(2))(2))] (R = Et (6), (i)Pr (7)) through an oxidative addition. Most notably, 1 and 3 catalyze the cyclotrimerization of alkynes, giving tri-substituted benzenes in good yields and a 1,3,5-triphenylbenzene coordinated intermediate 8 was isolated and characterized.

Monooxygenase‐Like Reactivity of an Unprecedented Heterobimetallic {FeO2Ni} Moiety

Pool together: Oxidative addition of the superoxo ligand inherent to the nickel(II) superoxide 1 onto iron(I) precursor complexes 2 a/2 b leads unexpectedly and exclusively to the first NiFe alkoxo hydroxides 3 a (R=Me) and 3 b (R=tBu). The latter result from an unexpected, selective oxygenation of a CH bond of one of the isopropyl groups at the β-diketiminato ligand coordinated to nickel.

Halo, Alkyl, Aryl, and Bis(imido) Complexes of Niobium Supported by the β-Diketiminato Ligand

Synthesis of the complex (BDI)Nb(N(t)Bu)Cl(2)py (BDI = HC[C(Me)N(2,6-iPr(2)-C(6)H(3))](2)) was achieved in high yield following the treatment of Nb(N(t)Bu)Cl(3)py(2) with Li(BDI)(OEt(2)). Substitution of the chlorides for fluorides was effected by introducing 2.0 equiv of Me(3)SnF in toluene, providing the pyridine-coordinated difluoride complex (BDI)Nb(N(t)Bu)F(2)py in modest yield. The pyridine ligands from both halide compounds were removed by treatment of the pyridine adducts with B(C(6)F(5))(3), affording the Lewis base-free complexes (BDI)Nb(NtBu)X(2) (X = Cl, F). Additionally, the Lewis base-free dichlorides of the (t)Bu-imido and Ar-imido (Ar = 2,6-(i)Pr(2)-C(6)H(3)) complexes were obtained following treatment of Nb(NR)Cl(3)(dme) (R = tBu, Ar) with Li(BDI)(OEt(2)). The pyridine-coordinated dichloride was alkylated and arylated to form the dimethyl complex (BDI)Nb(N(t)Bu)Me(2) (described previously, see text) and the mono(p-tolyl) complex (BDI)Nb(N(t)Bu)Cl(p-tol), the latter of which was methylated with MeMgBr to yield the mixed alkyl/aryl complex (BDI)Nb(N(t)Bu)Me(p-tol) in good yield. A rare example of a Group 5 bis((t)Bu-imido) species was synthesized in good yield via treatment of (BDI)Nb(N(t)Bu)Cl(2)py with 2.0 equiv of LiNHtBu to form (BDI)Nb(NtBu)(2)py. Exchange of the coordinated pyridine ligand for either pyridine-d(5) or dmap (p-(dimethylamino)pyridine) was shown to occur through a dissociative mechanism, allowing for removal of the coordinated Lewis base by treatment with B(C(6)F(5))(3). The resulting average C(2v)-symmetric tetracoordinate bis(imido) complex (BDI)Nb(N(t)Bu)(2) was characterized in solution by NMR spectroscopy and observed to undergo clean thermal decomposition to yield (BDI(#))Nb(N(t)Bu)(NH(t)Bu) (BDI(#) = H(2)C=C(NAr)CH=C(NAr)Me) over several hours at room temperature. Treatment of the four-coordinate bis(imido) with (t)BuNCO resulted in clean [2 + 2] cycloaddition to yield an oxaazametallacyclobutane complex, which was further observed to extrude (t)BuN=C=N(t)Bu over 12 h at room temperature. The molecular structures of (BDI)Nb(N(t)Bu)Cl(2)py, (BDI)Nb(NAr)Cl(2), (BDI)Nb(N(t)Bu)Me(2), (BDI)Nb(N(t)Bu)Cl(p-tol), (BDI)Nb(N(t)Bu)(2)py, and (BDI)Nb(NtBu)(2)(dmap) were determined crystallographically. Finally, DFT (BP86) geometry optimization calculations on a model complex of the thermally unstable four-coordinate bis(imido) species allowed for identification of the orbital interactions leading to activation of the imido groups through mixing with the BDI frontier orbitals.

New reaction of β-diketiminatoeuropium complex: sterically induced oxidation–coupling of β-diketiminato ligands

Attempted synthesis of sterically demanding tris-beta-diketiminate complexes of europium led to oxidation-coupling of beta-diketiminates and the formation of the THF-solvated divalent europium complex Eu(L(2,6-Me(2)))(2)(THF) (L(2,6-Me(2)) = [{N(2,6-Me(2)C(6)H(3))C(Me)}(2)CH](-)), while the normal tris-beta-diketiminate complex Eu(L(2-Me))(3) for the less bulky ligand L(2-Me) ([{N(2-MeC(6)H(4))C(Me)}(2)CH](-)) was isolated by the same procedure.

β-Diketiminato Nickel(I) Complexes with Very Weak Ligation Allowing for H2 and N2 Activation

Reaction of [LtBuNiBr] (LtBu = [HC(C(CMe3)NC6H3(iPr)2)2]−) with KC8 in toluene solution yields the complex [LtBuNi(toluene)], 1, where toluene is bound in a η2 mode via a C═C unit of the aromatic ring, as revealed by single-crystal X-ray crystallography and DFT calculations (B3LYP/6-31G*). Performing the same reaction in hexane as the solvent did not lead to a traceable product, so that the β-diketiminato ligand system was changed from LtBu to the less bulky LMe (LMe = [HC(CMeNC6H3(iPr)2)2]−). Reduction of [LMeNiBr]2 with KC8 in diethyl ether led to [LMeNi]2, 2, with intramolecular Ni−aryl interactions, while employment of [LMeNi(μ-Br)2Li(thf)2] as a precursor for a reaction with KC8 in OEt2 led to the complex [LMeNi(μ-Br)Li(thf)2]2, 3. Both complexes 2 and 3 could be fully characterized, also with the aid of XRD, and their reactivity with respect to H2 and N2 was examined. It turned out that they oxidatively add H2 to give the known compound [LMeNi(μ-H)]2, I, while the reaction with N2 provides the dinit...

Metalation-Resistant β-Diketiminato Ligands for Thermally Robust Organoscandium Complexes

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionMetalation-Resistant β-Diketiminato Ligands for Thermally Robust Organoscandium ComplexesAlyson L. Kenward, Jennifer A. Ross, Warren E. Piers*, and Masood ParvezCite this: Organometallics 2009, 28, 16, 4898Publication Date (Web):July 22, 2009Publication History Received8 July 2009Published online22 July 2009Published inissue 24 August 2009https://doi.org/10.1021/om900590yCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views602Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (597 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Group 15 compounds,Ligands Get e-Alerts

Low-Coordinate Organoyttrium Complexes Supported by β-Diketiminato Ligands

Several organoyttrium complexes stabilized by β-diketiminato ligands (Ar)NC(R)CHC(R)N(Ar) (Ar = 2,6-iPr2C6H3; R = CH3 (ligand a), R = iBu (ligand b)) have been prepared. Ligand-supported yttrium diiodides LYI2(THF)n were alkylated with organolithium or potassium reagents, yielding low-coordinate bis-alkyl derivatives. Several of these compounds have been characterized by X-ray crystallography, and a discussion of these structures in comparison to similar scandium complexes is presented. An out-of-plane bonding mode is observed in the solid state, analogous to that seen in scandium bis-alkyls, and spectroscopic studies reveal that fluxional behavior in solution is also comparable to that observed for the scandium species. The bis-alkyls LYR2 are susceptible to metalative alkane elimination at room temperature in solution. Activation of (Liga)YR2 with [HNMe2Ph][B(C6F5)4] generates alkyl cations stabilized with η6-arene-bound NMe2Ph. This unique coordination mode was studied via 1D 1H, 13C, and 15N NMR and 2D ROESY spectroscopy and appears to stabilize the alkyl cations against metalative alkane elimination.

Twice silicon-induced C–H activation and tautomerisation of a β-diketiminato ligand and formation of new types of N-heterocyclic silanes

Unexpected formation of the novel dianionic N,C-chelate ligand LD2- [HC[C(Me)-NR][C(NHR)=CH]]2- occurs by a twice silicon-assisted C-H bond activation of a terminal methyl group on a beta-diketiminato ligand backbone, starting from the corresponding lithium beta-diketiminide and silicon tetrabromide to give the new N-heterocyclic dibromosilanes and .

Synthesis, Characterization, and Reaction of Aluminum Halide Amides Supported by a Bulky β-Diketiminato Ligand

Monomeric aluminum chloride amides with the general formula LAl(Cl)NR2 (1, R = Me; 2, R = iPr; 3, R = SiMe 3; L = HC[C(Me)N(Ar)]2; Ar = 2,6- iPr2C6H3) were prepared by selected routes. Treatment of LAlBr 2 (4) and LAlI2 with LiNMe2 yielded LAl(Br)NMe2 (5) and LAl(I)NMe2 (6), respectively. The alkylation of 1 and 2 with MeLi gave the corresponding methylated compounds LAl(Me)NR2 (7, R = Me; 8, R = iPr); however, no reaction of 3 with MeLi was observed because of steric hindrance. Subsequent fluorination of 1- 3 afforded LAl(F)NR2 (9, R = Me; 10, R = iPr; 11, R = SiMe3). Compounds 1-11 were characterized by multinuclear NMR, electron impact mass spectrometry, and IR. The constitution of compounds 1-3 was confirmed by single-crystal X-ray diffraction studies.

Preparation of the hydrocarbon-soluble trifluoro complex LTiF 3 with a β-diketiminato ligand

The β-diketiminato fluoride complex (LTiF 3) ( 1) (L = HC(CMeN(2,6- iPr 2C 6H 3)) 2, “NacNac”) has been obtained using two synthetic routes, interaction of TiF 4 and NacNacK·2THF in toluene and interaction of LTiCl 3 and 3 equiv. of Me 3SnF in toluene. The trifluoro complex (LTiF 3) ( 1) is soluble in the non-polar solvents toluene and hexane and moderately active in polymerization of ethylene; the activity is higher than that of LTiMe 3 and comparable with that of the oxo-bridged complexes LTiCl(μ-O) 2TiClL and LTiMe(μ-O) 2TiMeL·toluene. Compound 1 was characterized by single crystal X-ray structural analysis, elemental analysis, NMR spectroscopy, and mass spectrometry. Complex 1 in the solid state is a centrosymmetric dimer containing two LTiF 2 moieties connected by two bridging fluorines, whereas C 6D 6 and CD 3CN solutions of 1 contain the monomeric complex at room temperature.

Organoaluminum Hydroxides Supported by β-Diketiminato Ligands: Synthesis, Structural Characterization, and Reactions

Three β-diketiminato ligands (L1 = HC[C(Me)N(Ar)]2, Ar = 2,4,6-Me3C6H2; L2 = HC[C(Me)N(Ar)]2, Ar = 2,6-iPr2C6H3; L3 = HC[C(tBu)N(Ar)]2, Ar = 2,6-iPr2C6H3) were employed to prepare the organoaluminum hydroxides LAlR(OH) (R = Me, Et, Ph, OEt, OSiMe3) by hydrolysis of the corresponding chlorides in the presence of a N-heterocyclic carbene as HCl scavenger. Reaction of the organoaluminum hydroxide with Cp2ZrMe2 in toluene afforded the heterobimetallic oxide LAlR(μ-O)ZrMeCp2 under evolution of methane. All compounds were characterized by multinuclear NMR, IR, mass spectrometry, and elemental analysis. The structures of L1AlPh(OH) (10), L2AlPh(OH) (11), L2AlOEt(OH) (12), L2AlOSiMe3(OH) (13), and L2AlPh(μ-O)ZrMeCp2 (17) were determined by single-crystal X-ray diffraction studies. The polymerization of ethylene was studied with compound 17, which exhibits moderate catalytic activity.

Functionalized phosphorus analogues of the β-diketiminato ligand systems: bis(N-arylphosphinimino)acetonitrile-derived complexes of rhodium and iridium

Staudinger reaction of dppm-CN (5) gave the corresponding bis(N-phenylphosphinimino)acetonitrile system (6). Deprotonation with LDA furnished the corresponding anionic ligand 9. Its reaction with [(CO)(2)RhCl](2) gave the corresponding kappa(2)N,N'-chelate complex 11. X-Ray diffraction revealed a non-planar boat-like conformation of the six-membered chelate ring in the crystal. Treatment of 9 with [(nbd)RhCl](2) gave the six-membered chelate complex 12 which features a different twist-like structure in the solid state, as does 13, which was formed by reacting 9 with [(cod)IrCl](2).

Guanidinato-based precursors for MOCVD of metal nitrides (M xN: M = Ta,W)

Refractory metal nitrides such as TaN and W x N are interesting candidates as novel gate electrodes in CMOS technology. MOCVD and, in particular, ALD are desirable deposition processes and the development of new complexes and the precursor chemistry plays a vital role. We are interested in fine-tuning the properties of key precursors by ligand variation and introducing the chelating all-nitrogen coordinating groups such as guanidinato and β-diketiminato ligands. Guanidinato ligand-based complexes of groups V and VI, especially Ta, and W are interesting precursors for MOCVD and ALD of respective metal nitride thin film growth. As a representative example, evaluation of Ta- and W-based guanidinato complexes as MOCVD precursors and thermal analysis of the new complexes by TG–DTA analysis will be presented. The MOCVD of TaN, W x N thin film growth using our novel mixed ligand precursors and the film characterization by XRD, SEM, cross-sectional SEM, SNMS and conductivity measurements (four-point probe analysis) is discussed in detail. Ta-guanidinato complexes were also used as a single source precursor for MOCVD of TaN. Nearly stoichiometric cubic TaN films with very less carbon content were obtained with good conductivity values.

The reactions of phosphorus(III) halides with β-diketiminato ligands

Reactions of the lithium or sodium salt, [HC(CMeNDipp)2]M (Dipp = 2,6-diisopropylbenzene, M = Li or Na), with PBr3 or PCl3 affords a series of phosphenium cations that were characterized in the solid state by X-ray crystallography. Solid-state analysis reveals that for compounds 1 and 2, C–H activation of the ligand occurs and the phosphorus is bound to a nitrogen and carbon atom of the ligand. Compound 3 exhibits the more traditional nitrogen chelation of the ligand to the phosphorus atom.

Synthesis and properties of alkaline metal complexes with new overcrowded β-diketiminato ligands

Enaminoimines TbtNHC(Me)CHC(Me)NAr ( 5, Tbt = 2,4,6-[CH(SiMe 3) 2] 3C 6H 2) bearing a Tbt group were synthesized by the two steps condensation of acetylacetone with bulky amines. Enaminoimines 5 were treated with n-BuLi to give the corresponding lithium β-diketiminates, [Li{TbtNHC(Me)CHC(Me)NAr}] ( 1). The X-ray structural analysis of [Li{TbtNC(Me)CHC(Me)NMes}] ( 1c, Mes = mesityl) revealed that it is a monomeric, solvent-free lithium β-diketiminate. The equilibrium between free 1c plus THF and THF-coordinated ( 1c · thf) was investigated in detail by the determination of the association constant ( K a) in C 6D 6 at 293 K and the Job’s plot. The heavier alkali metal complexes, sodium and potassium β-diketiminates ( 6c– 9c), were prepared by the two routes. THF-coordinated [M{TbtNC(Me)CHC(Me)NMes}(thf)] ( 6c: M = Na. 7c: M = K) were prepared by the reaction of 5c (Ar = Mes) with MH (M = Na, K). Solvent-free [M{TbtNC(Me)CHC(Me)NMes}] ( 8c: M = Na. 9c: M = K) were prepared by the reaction of 1c with t-BuOM (M = Na, K).

β-Diketiminato Scandium Chemistry: Attempted Deprotonation of Cationic Amido Complexes

Treatment of the β-diketiminato-supported scandium amido methyl derivatives [ArNC(tBu)CHC(tBu)NAr]Sc(Me)(NHR) (Ar = 2,6-iPr2-C6H3; R = tBu, 2,6-iPr2-C6H3) with 1 equiv of tris(pentafluorophenyl)borane resulted in the formation of scandium amido ion pairs, 1a and 1b, respectively, in good yields. A single-crystal X-ray analysis of 1a was undertaken, and two crystallographically independent molecules were observed in which one contains an N−H···F−C hydrogen bond while the other does not. Several attempts to deprotonate the amido ligand to yield a neutral imido species resulted in either attack of the base at the metal center or deprotonation of the β-diketiminato ligand. For example, treatment of 1a with tert-butyllithium gave [ArNC(tBu)CHC(tBu)NAr]Sc(CMe3)(NHtBu) (2), while treatment with the phosphazene base [(Me2N)3PN]3PNtBu gave the previously characterized metalated complex 3.

Reduction of Tetravalent Group 4 Metal Complexes Supported by an Extremely Bulky, Unsymmetrically Substituted β-Diketiminato Ligand Leading to the Regioselective CN Bond Cleavage Giving Ring-Contracted Metal-Imido Complexes

Reductions of tetravalent group 4 metal β-diketiminates, [MIVCl3(nacnac)(thf)n] (2a, M = Ti; 3b, M = Zr; 3c, M = Hf; nacnac = {N(Tbt)C(Me)CHC(Me)N(Mes)}-, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl, n = 0, 1), with 2 equiv of KC8 in the presence of LiCl and tmeda afforded the metal-imido complexes [MNTbt{C(Me)CHC(Me)N(Mes)}(μ-Cl)2Li(tmeda)] (4a, M = Ti; 4b, M = Zr; 4c, M = Hf; tmeda = Me2NCH2CH2NMe2). The formation of imido complexes 4a−c can be explained in terms of the generation of the corresponding divalent complexes [MIICl(nacnac)(L)n] (6a, M = Ti; 6b, M = Zr; 6c, M = Hf; L = thf or Li(tmeda), etc.), followed by the reductive, regioselective cleavage of the CN bond tethered to the Tbt group. The intermediacy of the divalent titanium complex 6a was supported by the alternative formation of 4a in the reaction of [Li(nacnac)] (1) with [TiIICl2(tmeda)2]. Interestingly, 4a−c reacted with H2O to give the free ligand nacnacH (8).

Rare earth metal complexes based on β-diketiminato and novel linked bis(β-diketiminato) ligands: Synthesis, structural characterization and catalytic application in epoxide/CO 2-copolymerization

Mesityl substituted β-diketiminato lanthanum and yttrium complexes [(BDI)Ln{N(SiRMe 2)} 2] (BDI = ArNC(Me)CHC(Me)NAr, Ar = 2,4,6-Me 3C 6H 2, Ln = La, R = Me ( 1), H ( 2a); Ln = Y, R = H ( 2b)) can be prepared via facile amine elimination starting from [La{N(SiMe 3) 2} 3] and [Ln{N(SiHMe 2) 2} 3(THF) 2] (Ln = Y, La), respectively. The X-ray crystal structure analysis of 1 revealed a distorted tetrahedral geometry around lanthanum with a η 2-bound β-diketiminato ligand. A series of novel ethylene- and cyclohexyl-linked bis(β-diketiminato) ligands [C 2H 4(BDI Ar) 2]H 2 and [Cy(BDI Ar) 2]H 2 [Ar = Mes (=2,4,6-Me 3C 6H 2), DEP (=2,6-Et 2C 6H 3), DIPP (=2,6- i-Pr 2C 6H 3)] were synthesized in a two step condensation procedure. The corresponding bis(β-diketiminato) yttrium and lanthanum complexes were obtained via amine elimination. The X-ray crystal structure analysis of the ethylene-bridged bis(β-diketiminato) complex [{C 2H 4(BDI Mes) 2}YN(SiMe 3) 2] ( 3b) and cyclohexyl-bridged complexes [{Cy(BDI Mes) 2}LaN(SiHMe 2) 2] ( 7) and [{Cy(BDI DEP) 2}LaN(SiMe 3) 2] ( 8) revealed a distorted square pyramidal coordination geometry around the rare earth metal, in which the amido ligand occupies the apical position and the two linked β-diketiminato moieties form the basis. The geometry of the bis(β-diketiminato) ligands depends significantly on the linker unit. While complexes with an ethylene-linked ligand adopt a cisoid arrangement of the two aromatic substituents, complexes with cyclohexyl linker adopt a transoid arrangement. Either one ( 3b) or both ( 7, 8) of the β-diketiminato moieties are tilted out of the η 2 coordination mode, resulting in close Ln⋯C contacts. The β-diketiminato and linked bis(β-diketiminato) complexes were moderately active in the copolymerization of cyclohexene oxide with CO 2. A maximum of 92% carbonate linkages were obtained using the ethylene-bridged bis(β-diketiminato) complex [{C 2H 4(BDI Mes) 2}LaN(SiHMe 2) 2] ( 4).