Synthesis and characterisation of [AlMen{Si(SiMe3)3}3−n(thf)] (n = 1 or 2)

The crystalline compounds [AlMe_n{Si(SiMe₃)₃}_3−n(thf)] [n = 2 (1) or 1 (2)] were prepared from the lithium sisyl [Li{Si(SiMe₃)₃}(thf)₃] (A) and the appropriate methylaluminium chloride [AlCl_3−nMe_n] in thf. The X-ray structure of 1 is reported. Unlike A or a magnesium sisyl [Mg{Si(SiMe₃)₃}₂(thf)₂] (B), neither 1 nor 2 underwent an insertion reaction with an α-H-free nitrile.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Synthesis and structures of crystalline lithium 1-azaallyls and a 1,3-diazaallyl derived from Li{CH(SiMe3)(SiMe3−n(OMe)n)} (n=1 or 2) and Li{CH(SiMe2OMe)2} and RCN (R=Bu, Ph, 2,5-Me2C6H3, or Ad)

Crystalline [Li{N(SiMe₂OMe)C(^tBu)C(H)(SiMe₃)}]₂ (5), [Li{N(SiMe₂OMe)C(Ph)C(H)(SiMe₃)}]₂ (6), [C(C₆H₃Me₂-2,5)C(H)(SiMe₃)}(TMEDA)](7), [Li{N(SiMe(OMe)₂)C(^tBu)C(H)(SiMe₃)}(THF)]₂ (8), Li{N(SiMe(OMe)₂)C(Ph)C(H)(SiMe₃)}(TMEDA) (9) and [Li{N(SiMe₂OMe)C(^tBu)C(H)(SiMe₂OMe)}]₂ (10) were readily obtained at ambient temperature from (i) [Li{CH(SiMe₃)(SiMe₂OMe)}]₈ (1) and an equivalent portion of RCN (R=^tBu (5), Ph (6) or 2,5-Me₂C₆H₃ (7)); (ii) [Li{CH(SiMe₃)(SiMe(OMe)₂)}]_∞ (2) and an equivalent portion of ^tBuCN (8) or PhCN (9); and (iii) [Li{CH(SiMe₂OMe)₂}]_∞ (3) and one equivalent of ^tBuCN (10). Reactions (i) and (ii) were regiospecific with SiMe_3−n(OMe)_n>SiMe₃ in 1,3-migration from C (in 1 or 2)→N. The 1-azaallyl ligand was bound to the lithium atom as a terminally bound κ¹-enamide (8 and 10), a bridging η³-1-azaallyl (6), or a bridging κ¹-enamide (5). The stereochemistry about the CC bond was Z for 5, 8 and 10 and E for 7. X-ray data are provided for 5, 6, 7, 8 and 10 and multinuclear NMR spectra data in C₆D₆ or C₆D₅CD₃ for each of 5-10.     

Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe3)2(SiMe2H) and C(SiMe2Ph)2(SiMe2H)

Metallation of (HMe₂Si)(Me₃Si)₂CH (1) by LiMe gave the organolithium compound Li(THF)₂C(SiMe₃)₂(SiMe₂H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)₄][Li{C(SiMe₃)₂(SiMe₂H)}₂] (2b). Treatment of a mixture of 1 and LiMe with KOBu^t gave KC(SiMe₃)₂(SiMe₂H) (3). This reacted with AlMe₂Cl in hexane/THF to give Al(THF)Me₂{C(SiMe₃)₂(Si Me₂H)} (4). Treatment of (HMe₂Si)(PhMe₂Si)₂CH (5) with LiMe in Et₂O/THF gave the THF adduct [Li(THF)₂C(SiMe₂Ph)₂(SiMe₂H)] (6); in the presence of KOBu^t the solvent-free [K][C(SiMe₂Ph)₂(SiMe₂H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe₂Cl to give [AlClMe{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (8) and AlMe₃. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.     

Synthesis and structures of 3-sila-β-diketiminato complexes of the coinage metals

The dimeric copper(I) 3-sila-β-diketiminate [Cu{(N(R)C(Ar))₂SiR}]₂ · (thf) (1) was obtained from CuI and [Li{(N(R)C(Ar))₂SiR}(thf)₂] (B) in toluene (R = SiMe₃, Ar = C₆H₃Me₂-2,6). When [CuI(PPh₃)₃] was used as a starting material, the LiI-containing compound [Cu{Si(R)(C(Ar)N(R))₂Li(μ-I)}(PPh₃)] (2) was isolated. The reaction of [MI(PPh₃)_n] (M = Ag, n = 3; M = Au, n = 2) with two equivalents of B in toluene gave the isomorphous silver and gold 3-sila-β-diketiminates [M{Si(R)(C(Ar)N(R))₂Li}₂(μ-I)] [M = Ag (3), Au (4)]. Each of 1-4 was characterised by the multinuclear NMR spectroscopy and single-crystal X-ray diffraction crystallography.     

New orthopalladated complexes of phosphorus ylides: Crystal structure of [Pd{CH{P(C7H6)(p-tolyl)2}COCH3}Cl{P(p-tolyl)3}]

This work reports on the preparation of the complexes [PdCl₂(Y¹)₂], [PdCl₂(Y²)₂] (Y¹ = (p-tolyl)₃PCHCOCH₃ (1a); Y² = Ph₃PCHCO₂CH₂Ph (1b)), [Pd{CHP(C₇H₆)(p-tolyl)₂COCH₃}(μ-Cl)]₂ (2a), [Pd{CHP(C₆H₄)Ph₂CO₂CH₂Ph}(μ-Cl)]₂ (2b), [Pd{CH{P(C₇H₆)(p-tolyl)₂}COCH₃}Cl(L)] (L = PPh₃ (3a), P(p-tolyl)₃ (4a)) and [Pd{CH{P(C₆H₄)Ph₂}CO₂CH₂Ph}Cl(L)] (L = PPh₃ (3b), P(p-tolyl)₃ (4b)). Orthometallation and ylide C-coordination in complexes 2a–4b are demonstrated by an X-ray diffraction study of 4a.     

Assembly molecular architectures based on structural variation of metalloligand [Cu(PySal)2] (PySal = 3-pyridylmethylsalicylideneimino)

A versatile neutral metalloligand [Cu(PySal)₂] (1) (PySal = 3-pyridylmethylsalicylidene-imino) was exploited as a building unit to construct five complexes {Cu[Cu(PySal)₂]₂}(ClO₄)₂ (2), {Cd[Cu(PySal)₂]₂(H₂O)₂]} (NO₃)₂ · 2H₂O · 4CH₃OH (3), {Zn[μ₂-Cu(PySal)₂]Cl₂}_n · nCH₃OH (4), {Hg[μ₂-Cu(PySal)₂]I₂}_n (5) and {Cd[μ₂-Cu(PySal)₂]Cl₂}_n · nCH₂Cl₂ (6). [Cu(PySal)₂] acts as a chelating ligand in discrete complexes 2 and 3 with unbound anions, but as a bis-monodentate bridging ligand in polymers 4, 5 and 6 when halogen anions coordinated cooperatively to metal cations. The coordination geometry of Cu²⁺ is well-defined square planar in bridging [Cu(PySal)₂], analogous to that in free metalloligand (1), but it is distorted square planar in chelating [Cu(PySal)₂].     

Syntheses and structures of [Me2Si{As(PBu)3}2] and [(CyP)3SiMe2] (Cy = cyclohexyl, C6H11)

The reaction of the anion [(^tBuP)₃As]⁻ (1) with Me₂SiCl₂ results in nucleophilic substitution of the Cl⁻ anions, giving the di- and mono-substituted products [Me₂Si{As(P^tBu)₃}₂] (3a) and [Me₂Si(Cl){As(P^tBu)₃}] (3b). Analogous reactions of the pre-isolated [(CyP)₄As]⁻ anion (2) (Cy = cyclohexyl) with Me₂SiCl₂ produced mixtures of products, from which no pure materials could be isolated. However, reaction of 2 [generated in situ from CyPHLi and As(NMe₂)₃] gives the heterocycle [(CyP)₃SiMe₂] (4). The X-ray structures of 3a and 4 are reported.     

Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Syntheses of rac/meso-{PhP(3-t-Bu-C5H3)2}-Zr{RN(CH2)3NR}, structural analyses of rac-{PhP(3-t-Bu-C5H3)2}Zr{RN(CH2)3NR} (where R is SiMe3 or Ph), and meso to rac isomerization

Syntheses of rac/meso-{PhP(3-t-Bu-C₅H₃)₂}Zr{Me₃SiN(CH₂)₃NSiMe₃} (rac-3/meso-3) and rac/meso-{PhP(3-t-Bu-C₅H₃)₂}Zr{PhN(CH₂)₃NPh} (rac-4/meso-4) were achieved by metallation of K₂[PhP(3-t-Bu-C₅H₃)₂] · 1.3 THF (2) with Zr{RN(CH₂)₃NR}Cl₂(THF)₂ (where R = SiMe₃ or Ph, respectively) using ethereal solvent. These isomeric pairs were characterized by ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy; rac-3 and rac-4 were also examined via single crystal X-ray crystallography. The structures of rac-3 and rac-4 are notable in the tendency of the cyclopentadienyl rings towards η³ coordination. While isolated samples of rac-3/meso-3 and rac-4/meso-4 slowly isomerize in tetrahydrofuran-d₈ to equilibrium ratios, the isomerization rate for 3 is more than 15-fold greater than that for 4. In addition, equilibrium ratios are rapidly reached when isolated samples of rac-3/meso-3 and rac-4/meso-4 are exposed to tetrabutylammonium chloride in tetrahydrofuran-d₈ solvent. We propose that a nucleophile (either chloride or the phosphine interannular linker) brings about dissociation of one cyclopentadienyl ring, thus promoting the rac/meso isomerization mechanism.     

On the reactivity of [IrCl(N2)(PPh3)2] with alkynylsilanes - A new route to vinylidene iridium(I) complexes

The iridium dinitrogen complex [IrCl(N₂)(PPh₃)₂] (1) was found to react with alkynylsilanes to form the vinylidene iridium(I) complexes trans- (R/R′ = Ph/Me, 2; Me/Me, 3; Bn/Me, 4; SiMe₃/Me, 5; SiEt₃/Et, 6; ⁱPr/Me, 7) and with Me₃SiCCC(O)R to yield the iridium η²-alkyne complexes trans-[IrCl{η²-Me₃SiCCC(O)R}(PPh₃)₂] (R = OEt, 9; Me, 11). Complex 9 was found to isomerize upon heating or upon UV irradiation yielding the vinylidene complex trans-[IrCl{CC(SiMe₃)CO₂Et}(PPh₃)₂] (10). The reaction of 1 with Me₃SiCCCCSiMe₃ yielded the complex trans-[IrCl{CC(SiMe₃)CCSiMe₃}(PPh₃)₂] (8), whereas with MeO₂CCCCO₂Me the iridacyclopentadiene complex [Ir{C₄(CO₂Me)₄}Cl(PPh₃)₂] (13) was formed. The complexes were characterized by means of ¹H, ¹³C and ³¹P NMR spectroscopy as well as by IR spectroscopy and microanalysis.     

Formation and structural characterization of mercury complexes from Te(R)CH2SiMe3 (R = Ph, CH2SiMe3) and HgCl2

The reaction of HgCl₂ and Te(R)CH₂SiMe₃ [R = CH₂SiMe₃ (1), Ph (2)] in ethanol yielded a mononuclear complex [HgCl₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 3a; R = CH₂SiMe₃, 3b). The recrystallization of 3a or 3b from CH₂Cl₂ produced a dinuclear complex [Hg₂Cl₂(μ-Cl)₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 4a; R = CH₂SiMe₃, 4b). When 3a was dissolved in CH₂Cl₂, the solvent quickly removed, and the solid recrystallized from EtOH, a stable ionic [HgCl{Te(Ph)CH₂SiMe₃}₃]Cl·2EtOH (5a·2EtOH) was obtained. Crystals of [HgCl₂{Te(CH₂SiMe)₂}]·2HgCl₂·CH₂Cl₂ (6b·2HgCl₂·CH₂Cl₂) were obtained from the CH₂Cl₂ solution of 3b upon prolonged standing. The complex formation was monitored by ¹²⁵Te-, and ¹⁹⁹Hg NMR spectroscopy, and the crystal structures of the complexes were determined by single crystal X-ray crystallography.     

Syntheses and structures of lithiated sulfones Li[CR(R′)SO2Ph] - C versus O bound lithium. [{Li{CH(Me)SO2Ph}(thf)}∞] - The structure of a C-bound derivative

Sulfones RCH(R′)SO₂Ph were reacted with n-BuLi in thf/n-hexane (R/R′ = H/Me, Me/Et, H/CH₂Ph) and toluene/n-hexane (R/R′ = Me/Ph) yielding under deprotonation Li[CR(R′)SO₂Ph] which reacted with Me₃SiCl and n-Bu₃SnCl forming the requisite trimethylsilyl and tri(n-butyl)tin substituted derivatives . Performing the reactions of RCH(R′)SO₂Ph with n-BuLi in n-hexane (instead of thf/n-hexane) and toluene/n-hexane, respectively, resulted in the precipitation of the organo lithium compounds Li[CR(R′)SO₂Ph] (1-4) which were isolated as strongly moisture-sensitive yellow powders in essentially quantitative yields. Their identities were confirmed by ¹H and ¹³C NMR spectroscopic measurements in thf-d₈. Solutions of each 1, 3, and 4 in thf/n-hexane and thf/n-pentane afforded crystals of each [{Li{CH(Me)SO₂Ph}(thf)}_∞] (1a), [{Li{CH(CH₂Ph)SO₂Ph}(thf)}_∞] (3a), and [{Li{CMe(Ph)SO₂Ph}(thf)₂}₂] (4a), respectively, whose structures were determined by single-crystal X-ray crystallography. The compounds 1a and 3a crystallize in 1D polymeric ladder-like structures. The strands of 1a are built-up by eight-membered Li₂C₂S₂O₂ rings having direct Li-C bonding interactions (Li-C 2.215(5) Å). The donor set of Li is completed by three oxygen atoms, one from the thf ligand and two from SO₂ groups of neighboring Li{CH(Me)SO₂Ph}(thf) entities. The strands of 3a are built-up of alternating Li₂S₂O₄ eight- and Li₂O₂ four-membered rings. Each lithium atom is coordinated to three oxygen atoms, two from O₂S(Ph)CHCH₂Ph groups and one from thf oxygen atom. There is no Li-C bonding. Compound 4a crystallizes in dimers consisting of eight-membered Li₂S₂O₄ rings in which the two lithium atoms are bridged by two O₂S(Ph)CHMePh groups. The coordination sphere of lithium is completed by two oxygen atoms of the thf ligands.     

Syntheses of platinum(II) complexes of cyclo-octenyl group and isolation of a self-assembled oxo-bridged macrocyclic complex [Pt4(Spy)4(C8H12-O-C8H12)2]

Reactions of [Pt₂(μ-Cl)₂(C₈H₁₂OMe)₂] (1) (C₈H₁₂OMe = 8-methoxy-cyclooct-4-ene-1-yl) with various anionic chalcogenolate ligands have been investigated. The reaction of 1 with Pb(Spy)₂ (HSpy = pyridine-2-thiol) yielded a binuclear complex [Pt₂(Spy)₂(C₈H₁₂OMe)₂] (2). A trinuclear complex [Pt₃(Spy)₄(C₈H₁₂OMe)₂] (3) was isolated by a reaction between 2 and [Pt(Spy)₂]_n. The reaction of 1 with HSpy in the presence of NaOMe generated 2 and its demethylated oxo-bridged tetranuclear complex [Pt₄(Spy)₄(C₈H₁₂-O-C₈H₁₂)₂] (4). Treatment of 1 with ammonium diisopropyldithiophosphate completely replaced C₈H₁₂OMe resulting in [Pt(S₂P{OPrⁱ}₂)₂] (5), whereas non-rigid 5-membered chelating ligand, Me₂NCH₂CH₂E⁻, produced mononuclear complexes [Pt(ECH₂CH₂NMe₂)(C₈H₁₂OMe)] (E = S (6), Se (7)). These complexes have been characterized by elemental analyses, NMR (¹H, ¹³C{¹H}, ¹⁹⁵Pt{¹H}) and absorption spectroscopy. Molecular structures of 2, 3, 4, 5 and 7 were established by single crystal X-ray diffraction analyses. Thermolysis of 2, 6 and 7 in HDA gave platinum nanoparticles.     

Synthesis and crystal structure of [C6H5Hg(H2NSiMe3)][H2N{B(C6F5)3}2], a phenyl-mercury(II) cation stabilised by a non-coordinating counter-anion

The new heteroleptic mercury(II) complex PhHgN(SiMe₃)₂(1) reacts with the strong Brønsted acid [H(OEt₂)₂][H₂N{B(C₆F₅)₃}₂] with cleavage of a N-Si bond to give [C₆H₅Hg(H₂NSiMe₃)][H₂N{B(C₆F₅)₃}₂] (2), a phenyl-mercury(II) cation stabilised by a primary amine and a non-coordinating counter-anion. Attempts to generate donor-free aryl mercury cations were not successful. The crystal structure of 2 · CH₂Cl₂ shows short π-bonding interactions between the metal and the phenyl ring of a neighbouring cation; the geometry about the mercury(II) atom is nearly linear. The X-ray structures of the new salts [H₂N(SiMe₃)₂ · H₃NSiMe₃][B(C₆F₅)₄]₂ and [Et₃O][H₂N{B(C₆F₅)₃}₂] · CH₂Cl₂ are also presented.     

Structural investigations on new iron-acyl derivatives of B(C6F5)3

Reactions between [Fe(η-C₅H₅)(MeCO)(CO)(L)], L = PPh₃ (1), PMe₃ (2), PPhMe₂ (3), PCy₃ (4), CO (5), and B(C₆F₅)₃ give new complexes [Fe(η-C₅H₅){MeCOB(C₆F₅)₃}(CO)(L)] L = PPh₃ (7), PMe₃ (8), PPhMe₂ (9), PCy₃ (10), CO (11), where B(C₆F₅)₃ coordinates selectively to the O-acyl groups. Hydrolysis of 7 gives [Fe(η-C₅H₅){HOB(C₆F₅)₃}(CO)(PPh₃)] (6). The X-ray structures of 6, 8 and 11 have been determined. Calculations, using density functional theory, demonstrate that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system. Both effects lead to a lengthening of the acyl C-O bond thus π populations cannot be inferred from the distance changes.     

Synthesis and derivatization, structures and transition metal (Mo(0), Fe(II), Pd(II) and Pt(II)) complexes of phenylaminobis(diphosphonite), PhN{P(OC6H4OMe-o)2}2

The synthesis, derivatization and coordination behavior of a new aminobis(diphosphonite), PhN{P(OC₆H₄OMe-o)₂}₂ (1) is described. The ligand 1 reacts with H₂O₂, elemental sulfur or selenium to give the corresponding dichalcogenides PhN{P(E)(OC₆H₄OMe-o)₂}₂ (E = O, 2; S, 3; Se, 4) in good yield. Reactions of 1 with Mo(CO)₆, Pd(NCCH₃)₂Cl₂ and Pt(COD)Cl₂ resulted in the formation of the chelate complexes, Mo(CO)₄[PhN{P(OC₆H₄OMe-o)₂}₂] (5) and MCl₂[PhN{P(OC₆H₄OMe-o)₂}₂] (M = Pd,7; M = Pt, 8) whereas in the reaction of 1 with [CpFe(CO)₂]₂, one of the P-N bonds cleaves due to the metal assisted hydrolysis to give a mononuclear complex, [CpFe(CO){P(O)(OC₆H₄OMe-o)₂}{PhN(H)(P(OC₆H₄OMe-o)₂)}] (6). The molecular structures of 1, 4, 5 and 6 are determined by X-ray studies.     

Group 12 metal aryl selenolates. Crystal and molecular structure of [2-(Et2NCH2)C6H4]2Se2 and [2-(Me2NCH2)C6H4Se]2M (M = Zn, Cd)

Diorganodiselenide [2-(Et₂NCH₂)C₆H₄]₂Se₂ (1) was obtained by hydrolysis/oxidation of the corresponding [2-(Et₂NCH₂)C₆H₄]SeLi derivative. The treatment of [2-(Et₂NCH₂)C₆H₄]₂Se₂ with elemental sodium in THF resulted in [2-(Et₂NCH₂)C₆H₄]SeNa (2). Reactions between alkali metal selenolates [2-(R₂NCH₂)C₆H₄]SeM′ (R = Me, Et; M′ = Li, Na) and MCl₂ (M = Zn, Cd) in a 2:1 molar ratio resulted in the [2-(R₂NCH₂)C₆H₄Se]₂M species [R = Me, M = Zn (3), Cd (4); R = Et, M = Zn (5), Cd (6)]. The new compounds were characterized by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹³Cd) and mass spectrometry. The crystal and molecular structures of 1, 3 and 4 revealed monomeric species stabilized by N → Se (for 1) and N → M (for 3 and 4) intramolecular interactions.     

Synthesis and characterization of anionic lanthanide complexes {[o-(Me3SiN)2C6H4]Ln(MeC5H4)2}{Li(DME)3} (Ln = Yb, Sm, Nd) and their catalytic activity for the polymerization of methyl methacrylate

The syntheses and structures of a series of new lanthanide complexes supported by a chelating diamide ligand N,N′-bis(trimethylsilyl)-o-phenylenediamine are described. Anhydrous LnCl₃ reacts with Li₂[o-(Me₃SiN)₂C₆H₄], followed by treatment of NaC₅H₄Me in 1:1:2 molar ratio to afford the corresponding anionic complexes: {[o-(Me₃SiN)₂C₆H₄]Ln(MeC₅H₄)₂}{Li(DME)₃} [Ln = Yb (1), Sm (2), Nd(3)] in high yield. These complexes were characterized by elemental analysis, IR and ¹H NMR. The molecular structures of 1 and 2 were further determined by X-ray diffraction techniques to be an ion-pair complex composed by an anion [o-(Me₃SiN)₂C₆H₄]Ln(MeC₅H₄)₂] and a cation [Li(DME)₃]. Complexes 1-3 showed high catalytic activity for the polymerization of methyl methacrylate (MMA) at r.t., giving the syndiotactic-rich polymers with relatively narrow molecular weight distributions (M_w/M_n = 1.64-1.82).     

Synthesis of new chloro methyl niobium and tantalum complexes with silyl-cyclopentadienyl ligands: X-ray crystal structure of [Ta{η-C5H3(SiMe3)2}Cl2Me2]

Trichloro methyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₃Me] (X = Cl, 2; Me, 3), dichloro dimethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₂Me₂] (X = Cl, 4; Me, 5) and tetramethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Me₄] (X = Me, 6; Cl, 7) niobium complexes were synthesized by treatment of starting tetrachloro derivatives [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1a; Me, 1b) with dimethyl zinc or chloro methyl magnesium in different proportions and conditions. A mixture of trichloro methyl and dichloro dimethyl tantalum complexes [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl_4−xMe_x] (x = 1, 8; 2, 9) in a 2:1 molar ratio was obtained in the reaction of [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl₄] (1c) with 0.5 equivalents of ZnMe₂ in toluene at low temperature. 8 could be isolated as single compound when 1 equivalent of 1c was added to the mixtures of 8 and 9, while the reaction of 1c with 1.5 equivalents of dimethyl zinc gave 9 as unitary product. However, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 0.5 equivalents of alkylating reagent giving the trichloro methyl compound [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₃Me] (10) in good yield. On the other hand, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 2 equivalents of MgClMe in hexane at room temperature giving a mixture of dichloro dimethyl and chloro trimethyl complexes[Ta{η⁵-C₅H₃(SiMe₃)₂}Cl_4−xMe_x] (x = 2, 11; 3, 12), while the use of 4 equivalents of MgClMe converts 1c into the tetramethyl derivative [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Me₄] (13). Finally, a tetramethyl tantalum complex [Ta{η⁵-C₅H₃(SiMe₃)₂}Me₄] (14) was prepared by reaction of [Ta{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1c; Me, 1d) with 5 (X = Cl) or 4 (X = Me) equivalents of MgClMe in diethyl ether (X = Cl) or hexane (X = Me), respectively, as solvent. All the complexes were studied by IR and NMR spectroscopy and the molecular structure of the complex 11 was determined by X-ray diffraction methods.