Si(SiMe3)3]3Ge9M(CO)3(-) (M=Cr, Mo, W): coordination chemistry with metalloid clusters

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-)1 can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. So the reaction of 1 with Cr(CO)(3)(CH(3)CN)(3) leads to a cluster enlargement where the chromium atom is incorporated into the cluster core. Here further applications of 1 as a flexible ligand in coordination chemistry are presented where the reaction of 1 with Mo(CO)(3)(EtCN)(3) and W(CO)(3)(CH(3)CN)(3) leads to [(CO)(3)MoGe(9)R(3)](-)4 and [(CO)(3)WGe(9)R(3)](-)5 respectively (R = Si(SiMe(3))(3)), showing that 1 can indeed be used as a flexible ligand in coordination chemistry. Structural and electronic properties of the Ge(9)M clusters 4 and 5 are discussed as well as mechanistic aspects of their formation.     

Ge(14)[Ge(SiMe(3))(3)](5)Li(3)(THF)(6): the largest metalloid cluster compound of germanium: on the way to fullerene-like compounds?

The reaction of GeBr with LiGe(SiMe(3))(3) yields the largest metalloid cluster compound of germanium Ge(14)[Ge(SiMe(3))(3)](5)Li(3)(THF)(6), in which 14 germanium atoms are arranged as a hollow sphere in the cluster core, showing that in the case of germanium also fullerene-like compounds might be present in the borderland between the molecular and solid states.     

Si(SiMe(3))(3)](6)Ge(18)M (M = Cu, Ag, Au): metalloid cluster compounds as unusual building blocks for a supramolecular chemistry

Very recently it was shown that the metalloid cluster compound {Ge(9)[Si(SiMe(3))(3)](3)}(-) can be used for subsequent reactions as the shielding of the cluster core is rather incomplete. Here further reactions of with M(+) sources of group 11 metals are described, leading to metalloid cluster compounds of the formula {MGe(18)[Si(SiMe(3))(3)](6)}(-) (M = Ag, Cu). These reactions can be seen as first steps into a supramolecular chemistry with metalloid cluster compounds. Beside this feature, the structural properties as well as the bonding situations in these cluster compounds are discussed.     

The electronic structure of Ge9[Si(SiMe3)3]3-: a superantiatom complex

We report on the electronic structure of Ge(9)[Si(SiMe(3))(3)](3)(-). Systematic density functional theory analysis of the electronic shell structure of the cluster and its derivatives reveals that the Ge(9)[Si(SiMe(3))(3)](3)(-) and its neutral counterpart have electronic shells that can be explained using the superatom model. The ligand-core interaction of these complexes is distinctly different from previously identified gold, gallium, and aluminium superatom complexes, indicating an electron-donating rather than electron-withdrawing ligand. We modify the electron-counting rule for this case and introduce a simple picture for superatom and superantiatom complexes. Discussions comparing shell models, Zintl clusters, the superhalogen Al(13) and superatom complexes to Ge(9)[Si(SiMe(3))(3)](3)(-) are presented.     

Reactions of LiE(SiMe(3))(3), E = Si, Ge: X-ray Crystal Structure of the Cyclotetrastannane [ClSnSi(SiMe(3))(3)](4)

Reaction of SnCl(2).dioxane with 2 equiv of Li(THF)(3)Si(SiMe(3))(3) in hexane afforded the cyclotetrastannane [(Me(3)Si)(3)SiSnCl](4) in reasonable yield. From pentane, the product crystallized as a red-orange disolvate in the P&onemacr; space group (triclinic) with a = 14.735(2) ?, b = 14.976(2) ?, c = 24.066(3) ?, alpha = 76.94 degrees, beta = 76.19 degrees, gamma = 62.11 degrees, V = 4517.5 ?(3), and Z = 2. The Sn(4) ring consisted of a slightly distorted, nonplanar (fold angle = 18.9 degrees ) rectangle with Sn-Sn distances of 2.8054(6), 2.8111(6), 2.9122(6), and 2.9146(6) ?. The pentane molecules were disordered. Selected mono- and dihalogermanes were treated with 1 equiv of Li(THF)(3)Si(SiMe(3))(3) or Li(THF)(2.5)Ge(SiMe(3))(3), affording (Me(3)Si)(3)EGe(CF(3))(3) (E = Si, Ge) and (Me(3)Si)(3)GeGeR(3) (R = Cl, CH(3), C(6)H(5)). Besides the monosubstitution product, the reaction of GeCl(4) with 1 equiv of Li(THF)(2.5)Ge(SiMe(3))(3) also gave a small amount of the linear tetragermane (Me(3)Si)(3)GeGeCl(2)GeCl(2)Ge(SiMe(3))(3). Good yields of the analogous phenyl derivative, (Me(3)Si)(3)GeGePh(2)GePh(2)Ge(SiMe(3))(3), were obtained by treating Ph(2)GeCl(2) with 2 equiv of the lithium-germyl reagent.     

Synthesis of the (N2)3- radical from Y2+ and its protonolysis reactivity to form (N2H2)2- via the Y[N(SiMe3)2]3/KC8 reduction system

Examination of the Y[N(SiMe(3))(2)](3)/KC(8) reduction system that allowed isolation of the (N(2))(3-) radical has led to the first evidence of Y(2+) in solution. The deep-blue solutions obtained from Y[N(SiMe(3))(2)](3) and KC(8) in THF at -35 °C under argon have EPR spectra containing a doublet at g(iso) = 1.976 with a 110 G hyperfine coupling constant. The solutions react with N(2) to generate (N(2))(2-) and (N(2))(3-) complexes {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2)) (1) and {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)] (2), respectively, and demonstrate that the Y[N(SiMe(3))(2)](3)/KC(8) reaction can proceed through an Y(2+) intermediate. The reactivity of (N(2))(3-) radical with proton sources was probed for the first time for comparison with the (N(2))(2-) and (N(2))(4-) chemistry. Complex 2 reacts with [Et(3)NH][BPh(4)] to form {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-N(2)H(2)), the first lanthanide (N(2)H(2))(2-) complex derived from dinitrogen, as well as 1 as a byproduct, consistent with radical disproportionation reactivity.     

(N2)3- radical chemistry via trivalent lanthanide salt/alkali metal reduction of dinitrogen: new syntheses and examples of (N2)2- and (N2)3- complexes and density functional theory comparisons of closed shell Sc3+, Y3+, and Lu3+ versus 4f(9) Dy3+

New syntheses of complexes containing the recently discovered (N(2))(3-) radical trianion have been developed by examining variations on the LnA(3)/M reductive system that delivers "LnA(2)" reactivity when Ln = scandium, yttrium, or a lanthanide, M = an alkali metal, and A = N(SiMe(3))(2) and C(5)R(5). The first examples of LnA(3)/M reduction of dinitrogen with aryloxide ligands (A = OC(6)R(5)) are reported: the combination of Dy(OAr)(3) (OAr = OC(6)H(3)(t)Bu(2)-2,6) with KC(8) under dinitrogen was found to produce both (N(2))(2-) and (N(2))(3-) products, [(ArO)(2)Dy(THF)(2)](2)(μ-η(2):η(2)-N(2)), 1, and [(ArO)(2)Dy(THF)](2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 2a, respectively. The range of metals that form (N(2))(3-) complexes with [N(SiMe(3))(2)](-) ancillary ligands has been expanded from Y to Lu, Er, and La. Ln[N(SiMe(3))(2)](3)/M reactions with M = Na as well as KC(8) are reported. Reduction of the isolated (N(2))(2-) complex {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2)), 3, with KC(8) forms the (N(2))(3-) complex, {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)], 4a, in high yield. The reverse transformation, the conversion of 4a to 3 can be accomplished cleanly with elemental Hg. The crown ether derivative {[(Me(3)Si)(2)N](2)Y(THF)}(2)(μ-η(2):η(2)-N(2))[K(18-crown-6)(THF)(2)] was isolated from reduction of 3 with KC(8) in the presence of 18-crown-6 and found to be much less soluble in tetrahydrofuran (THF) than the [K(THF)(6)](+) salt, which facilitates its separation from 3. Evidence for ligand metalation in the Y[N(SiMe(3))(2)](3)/KC(8) reaction was obtained through the crystal structure of the metallacyclic complex {[(Me(3)Si)(2)N](2)Y[CH(2)Si(Me(2))NSiMe(3)]}[K(18-crown-6)(THF)(toluene)]. Density functional theory previously used only with reduced dinitrogen complexes of closed shell Sc(3+) and Y(3+) was extended to Lu(3+) as well as to open shell 4f(9) Dy(3+) complexes to allow the first comparison of bonding between these four metals.     

Rational synthesis of [Ge9{Si(SiMe3)3}3]- from its parent Zintl ion Ge9(4-)

Reported is the first rational synthesis of a trisubstituted deltahedral Zintl ion, [Ge(9){Si(SiMe(3))(3)}(3)](-) in this case, by the addition of the three substituents in a reaction of the parent naked deltahedral Zintl ion Ge(9)(4-) with {(Me(3)Si)(3)Si}Cl. The new species were crystallized and structurally characterized in [K(2,2,2-crypt)](2)[Ge(9){Si(SiMe(3))(3)}(3)] (monoclinic, P2(1)/c, a = 26.497(3) ?, b = 24.090(2) ?, c = 29.268(3) ?, β = 113.888(2)°, V = 17082(3) ?(3), Z = 8, R1/wR2 = 0.0436/0.0812 for the observed data and 0.1023/0.1010 for all data).     

Iron-arylimide clusters [Fe(m)()(NAr)(n)Cl(4)](2)(-) (m,n = 2, 2; 3, 4; 4, 4) from a ferric amide precursor: synthesis,characterization, and comparison to Fe-S chemistry

Tetrahedral FeCl[N(SiMe(3))(2)](2)(THF) (2), prepared from FeCl(3) and 2 equiv of Na[N(SiMe(3))(2)] in THF, is a useful ferric starting material for the synthesis of weak-field iron-imide (Fe-NR) clusters. Protonolysis of 2 with aniline yields azobenzene and [Fe(2)(mu-Cl)(3)(THF)(6)](2)[Fe(3)(mu-NPh)(4)Cl(4)] (3), a salt composed of two diferrous monocations and a trinuclear dianion with a formal 2 Fe(III)/1 Fe(IV) oxidation state. Treatment of 2 with LiCl, which gives the adduct [FeCl(2)(N(SiMe(3))(2))(2)](-) (isolated as the [Li(TMEDA)(2)](+) salt), suppresses arylamine oxidation/iron reduction chemistry during protonolysis. Thus, under appropriate conditions, the reaction of 1:1 2/LiCl with arylamine provides a practical route to the following Fe-NR clusters: [Li(2)(THF)(7)][Fe(3)(mu-NPh)(4)Cl(4)] (5a), which contains the same Fe-NR cluster found in 3; [Li(THF)(4)](2)[Fe(3)(mu-N-p-Tol)(4)Cl(4)] (5b); [Li(DME)(3)](2)[Fe(2)(mu-NPh)(2)Cl(4)] (6a); [Li(2)(THF)(7)][Fe(2)(mu-NMes)(2)Cl(4)] (6c). [Li(DME)(3)](2)[Fe(4)(mu(3)-NPh)(4)Cl(4)] (7), a trace product in the synthesis of 5a and 6a, forms readily as the sole Fe-NR complex upon reduction of these lower nuclearity clusters. Products were characterized by X-ray crystallographic analysis, by electronic absorption, (1)H NMR, and M?ssbauer spectroscopies, and by cyclic voltammetry. The structures of the Fe-NR complexes derive from tetrahedral iron centers, edge-fused by imide bridges into linear arrays (5a,b; 6a,c) or the condensed heterocubane geometry (7), and are homologous to fundamental iron-sulfur (Fe-S) cluster motifs. The analogy to Fe-S chemistry also encompasses parallels between Fe-mediated redox transformations of nitrogen and sulfur ligands and reductive core conversions of linear dinuclear and trinuclear clusters to heterocubane species and is reinforced by other recent examples of iron- and cobalt-imide cluster chemistry. The correspondence of nitrogen and sulfur chemistry at iron is intriguing in the context of speculative Fe-mediated mechanisms for biological nitrogen fixation.     

Isolation of (CO)1- and (CO2)1- radical complexes of rare earths via Ln(NR2)3/K reduction and [K2(18-crown-6)2]2+ oligomerization

Deep-blue solutions of Y(2+) formed from Y(NR(2))(3) (R = SiMe(3)) and excess potassium in the presence of 18-crown-6 at -45 °C under vacuum in diethyl ether react with CO at -78 °C to form colorless crystals of the (CO)(1-) radical complex, {[(R(2)N)(3)Y(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 1. The polymeric structure contains trigonal bipyramidal [(R(2)N)(3)Y(μ-CO)(2)](2-) units with axial (CO)(1-) ligands linked by [K(2)(18-crown-6)(2)](2+) dications. Byproducts such as the ynediolate, [(R(2)N)(3)Y](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 2, in which two (CO)(1-) anions are coupled to form (OC≡CO)(2-), and the insertion/rearrangement product, {(R(2)N)(2)Y[OC(═CH(2))Si(Me(2))NSiMe(3)]}[K(18-crown-6)], 3, are common in these reactions that give variable results depending on the specific reaction conditions. The CO reduction in the presence of THF forms a solvated variant of 2, the ynediolate [(R(2)N)(3)Y](2)(μ-OC≡CO)[K(18-crown-6)(THF)(2)](2), 2a. CO(2) reacts analogously with Y(2+) to form the (CO(2))(1-) radical complex, {[(R(2)N)(3)Y(μ-CO(2))(2)][K(2)(18-crown-6)(2)]}(n), 4, that has a structure similar to that of 1. Analogous (CO)(1-) and (OC≡CO)(2-) complexes of lutetium were isolated using Lu(NR(2))(3)/K/18-crown-6: {[(R(2)N)(3)Lu(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 5, [(R(2)N)(3)Lu](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 6, and [(R(2)N)(3)Lu](2)(μ-OC≡CO)[K(18-crown-6)(Et(2)O)(2)](2), 6a.     

Lithiation of tris(alkyl- and arylamido)orthophosphates EP[N(H)R]3 (E = O,S, Se): imido substituent effects and P=E bond cleavage

In the solid state, OP[N(H)Me](3) (1a) and OP[N(H)(t)Bu](3) (1b) have hydrogen-bonded structures that exhibit three-dimensional and one-dimensional arrays, respectively. The lithiation of 1b with 1 equiv of (n)BuLi generates the trimeric monolithiated complex (THF)[LiOP(N(t)Bu)[N(H)(t)Bu](2)](3) (4), whereas reaction with an excess of (n)BuLi produces the dimeric dilithium complex [(THF)(2)Li(2)OP(N(t)Bu)(2)[N(H)(t)Bu]](2) (5). Complex 4 contains a Li(2)O(2) ring in an open-ladder structure, whereas 5 embraces a central Li(2)O(2) ring in a closed-ladder arrangement. Investigations of the lithiation of tris(alkyl or arylamido)thiophosphates, SP[N(H)R](3) (2a, R = (i)Pr; 2b, R = (t)Bu; 2c, R = p-tol) with (n)BuLi reveal interesting imido substituent effects. For the alkyl derivatives, only mono- or dilithiation is observed. In the case of R = (t)Bu, lithiation is accompanied by P-S bond cleavage to give the dilithiated cyclodiphosph(V/V)azane [(THF)(2)Li(2)[((t)BuN)(2)P(micro-N(t)Bu)(2)P(N(t)Bu)(2)]] (9). Trilithiation occurs for the triaryl derivatives EP[N(H)Ar](3) (E = S, Ar = p-tolyl; E = Se, Ar = Ph), as demonstrated by the preparation of [(THF)(4)Li(3)[SP(Np-tol)(3)]](2) (10) and [(THF)(4)Li(3)[SeP(NPh)(3)]](2) (11), which are accompanied by the formation of small amounts of 10.[LiOH(THF)](2) and 11.Li(2)Se(2)(THF)(2), respectively.     

Yttrium complexes incorporating the chelating diamides [ArN(CH2)xNAr]2- (Ar = C6H3-2,6-iPr2, x= 2, 3) and their unusual reaction with phenylsilane

Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)).     

The reaction of Li[Al(OR)4] R = OC(CF3)2Ph, OC(CF3)3 with NO/NO2 giving NO[Al(OR)4], Li[NO3] and N2O. The synthesis of NO[Al(OR)4] from Li[Al(OR)4] and NO[SbF6] in sulfur dioxide solution

NO[Al(OC(CF(3))(2)Ph)(4)] 1 and NO[Al(OC(CF(3))(3))(4)] 2 were obtained by the metathesis reaction of NO[SbF(6)] and the corresponding Li[Al(OR)(4)] salts in liquid sulfur dioxide solution in ca 40% (1) and 85% (2) isolated yield. 1 and 2, as well as Li[NO(3)] and N(2)O, were also given by the reaction of an excess of mixture of (90 mol%) NO, (10 mol%) NO(2) with Li[Al(OR)(4)] followed by extraction with SO(2). The unfavourable disproportionation reaction of 2NO(2)(g) to [NO](+)(g) and [NO(3)](-)(g)[DeltaH degrees = +616.2 kJ mol(-1)] is more than compensated by the disproportionation energy of 3NO(g) to N(2)O(g) and NO(2)(g)[DeltaH degrees =-155.4 kJ mol(-1)] and the lattice energy of Li[NO(3)](s)[U(POT)= 862 kJ mol(-1)]. Evidence is presented that the reaction proceeds via a complex of [Li](+) with NO, NO(2)(or their dimers) and N(2)O. NO(2) and Li[Al(OC(CF(3))(3))(4)] gave [NO(3)(NO)(3)][Al(OC(CF(3))(3))(4)](2), NO[Al(OC(CF(3))(3))(4)] and (NO(2))[Al(OC(CF(3))(3))(4)] products. The aluminium complex [Li[AlF(OC(CF(3))(2)Ph)(3)]](2) 3 was prepared by the thermal decomposition of Li[Al(OC(CF(3))(2)Ph)(4)]. Compounds 1 and 3 were characterized by single crystal X-ray structural analyses, 1-3 by elemental analyses, NMR, IR, Raman and mass spectra. Solid 1 contains [Al(OC(CF(3))(2)Ph)(4)](-) and [NO](+) weakly linked via donor acceptor interactions, while in the SO(2) solution there is an equilibrium between the associated [NO](+)[Al(OC(CF(3))(2)Ph)(4)](-) and separated solvated ions. Solid 2 contains essentially ionic [NO](+) and [Al(OC(CF(3))(3))(4)](-). Complex 3 consists of two [Li[AlF(OC(CF(3))(2)Ph)(3)]] units linked via fluorine lithium contacts. Compound 1 is unstable in the SO(2) solution and decomposes to yield [AlF(OC(CF(3))(2)Ph)(3)](-), [(PhC(CF(3))(2)O)(3)Al(mu-F)Al(OC(CF(3))(2)Ph)(3)](-) anions as well as (NO)C(6)H(4)C(CF(3))(2)OH, while compound 2 is stable in liquid SO(2). The [small nu](NO(+)) in 1 and [NO](+)(toluene)[SbCl(6)] are similar, implying similar basicities of [Al(OC(CF(3))(2)Ph)(4)](-) and toluene.     

A kinetic study of the silyl substitution in tantalum amide silyl complex (Me(2)N)(3)Ta[Si(SiMe(3))(3)](2)

Kinetic studies have been performed for the substitution of the first silyl ligand in (Me(2)N)(3)Ta[Si(SiMe(3))(3)](2) (1) by Li(THF)(3)SiButPh(2) at 233 K (THF = tetrahydrofuran). In the presence of excess Li(THF)(3)SiButPh(2), these studies reveal that the reaction likely follows a dissociative pathway. THF, a polar solvent, is found to promote the substitution, and the order of the reaction with respect to THF is 1.7(0.3).     

Synthesis and structural characterization of alkaline-earth-metal bis(amido)silane and lithium oxobis(aminolato)silane complexes

Several of alkaline-earth-metal complexes [(η(2):η(2):μ(N):μ(N)-Li)(+)](2)[{η(2)-Me(2)Si(DippN)(2)}(2)Mg](2-) (4), [η(2)(N,N)-Me(2)Si(DippN)(2)Ca·3THF] (5), [η(2)(N,N)-Me(2)Si(DippN)(2)Sr·THF] (6), and [η(2)(N,N)-Me(2)Si(DippN)(2)Ba·4THF] (7) of a bulky bis(amido)silane ligand were readily prepared by the metathesis reaction of alkali-metal bis(amido)silane [Me(2)Si(DippNLi)(2)] (Dipp = 2,6-i-Pr(2)C(6)H(3)) and alkaline-earth-metal halides MX(2) (M = Mg, X = Br; M = Ca, Sr, Ba, X = I). Alternatively, compounds 5-7 were synthesized either by transamination of M[N(SiMe(3))(2)](2)·2THF (M = Ca, Sr, Ba) and [Me(2)Si(DippNH)(2)] or by transmetalation of Sn[N(SiMe(3))(2)](2), [Me(2)Si(DippNH)(2)], and metallic calcium, strontium, and barium in situ. The metathesis reaction of dilithium bis(amido)silane [Me(2)Si(DippNLi)(2)] and magnesium bromide in the presence of oxygen afforded, however, an unusual lithium oxo polyhedral complex {[(DippN(Me(2)Si)(2))(μ-O)(Me(2)Si)](2)(μ-Br)(2)[(μ(3)-Li)·THF](4)(μ(4)-O)(4)(μ(3)-Li)(2)} (8) with a square-basket-shaped core Li(6)Br(2)O(4) bearing a bis(aminolato)silane ligand. All complexes were characterized using (1)H, (13)C, and (7)Li NMR and IR spectroscopy, in addition to X-ray crystallography.     

Trivalent [(C5Me5)2(THF)Ln]2(mu-eta2:eta2-N2) complexes as reducing agents including the reductive homologation of CO to a ketene carboxylate, (mu-eta4-O2C-C=C=O)2-

The [Z(2)Ln(THF)](2)(mu-eta(2)():eta(2)()-N(2)) complexes (Z = monoanionic ligand) generated by reduction of dinitrogen with trivalent lanthanide salts and alkali metals are strong reductants in their own right and provide another option in reductive lanthanide chemistry. Hence, lanthanide-based reduction chemistry can be effected in a diamagnetic trivalent system using the dinitrogen reduction product, [(C(5)Me(5))(2)(THF)La](2)(mu-eta(2)():eta(2)()-N(2)), 1, readily obtained from [(C(5)Me(5))(2)La][BPh(4)], KC(8), and N(2). Complex 1 reduces phenazine, cyclooctatetraene, anthracene, and azobenzene to form [(C(5)Me(5))(2)La](2)[mu-eta(3):eta(3)-(C(12)H(8)N(2))], 2, (C(5)Me(5))La(C(8)H(8)), 3, [(C(5)Me(5))(2)La](2)[mu-eta(3):eta(3)-(C(14)H(10))], 4, and [(C(5)Me(5))La(mu-eta(2)-(PhNNPh)(THF)](2), 5, respectively. Neither stilbene nor naphthalene are reduced by 1, but 1 reduces CO to make the ketene carboxylate complex {[(C(5)Me(5))(2)La](2)[mu-eta(4)-O(2)C-C=C=O](THF)}(2), 6, that contains CO-derived carbon atoms completely free of oxygen.     

{Sn9[Si(SiMe3)3]3}− and {Sn8Si[Si(SiMe3)3]3}−: variations of the E9 cage of metalloid group 14 clusters

The disproportionation reaction of the subvalent metastable halide SnBr proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Hence, the neutral metalloid cluster compound Sn(10)[Si(SiMe(3))(3)](6) (3) was synthesized from the reaction of SnBr with LiSi(SiMe(3))(3). In the course of the reaction anionic clusters might also be present, and we now present the first anionic cluster compound {Sn(8)E[Si(SiMe(3))(3)](3)}(-) (E = Si, Sn), where one position in the cluster core is occupied by a silicon or a tin atom, giving further insight into structural variations of E(9) cages in metalloid group 14 cluster compounds.     

Reaction of the silylene Si[(NCH2But)2C6H4-1,2] with the alkali metal silylamides M[N(SiMe3)R](M = Li, Na or K; R = SiMe3 or SiMe2Ph)

The thermally stable silylene Si[(NCH(2)Bu(t))(2)C(6)H(4)-1,2] 1 undergoes oxidative addition reactions with the alkali metal silylamides MN(SiMe(3))(2)(M = Li, Na or K) to afford the new alkali metal amides MN(SiMe(3))[(1)SiMe(3)][M = Li (2), Na (3) or K (4)]. Reaction of two equivalents of 1 with LiN(R)(SiMe(3)) leads in a two-step process to the compound LiN[(1)R][(1)SiMe(3)][R = SiMe(2)Ph (5) or SiMe(3) (6)]. Alternatively, 1 reacts with 3 to afford NaN[(1)SiMe(3)](2) (7). The structures of 2-5 and are presented and the formation of 2-7 is discussed.     

Unusual iron(III) ate complexes stabilized by Li-pi interactions

Several iron(III) complexes incorporating diamidoether ligands are described. The reaction between [Li(2)[RN(SiMe(2))](2)O] and FeX(3) (X=Cl or Br; R=2,4,6-Me(3)Ph or 2,6-iPr(2)Ph) form unusual ate complexes, [FeX(2)Li[RN(SiMe(2))](2)O](2) (2, X=Cl, R=2,4,6-Me(3)Ph; 3, X=Br, R=2,4,6-Me(3)Ph; 4, X=Cl, R=2,6-iPr(2)Ph) which are stabilized by Li-pi interactions. These dimeric iron(III)-diamido complexes exhibit magnetic behaviour characteristic of uncoupled high spin (S= 5/2 ) iron(III) centres. They also undergo halide metathesis resulting in reduced iron(II) species. Thus, reaction of 2 with alkyllithium reagents leads to the formation of iron(II) dimer [Fe[Me(3)PhN(SiMe(2))](2)O](2) (6). Similarly, the previously reported iron(III)-diamido complex [FeCl[tBuN(SiMe(2))](2)O](2) (1) reacts with LiPPh(2) to yield the iron(II) dimer [Fe[tBuN(SiMe(2))](2)O](2) but reaction with LiNPh(2) gives the iron(II) product [Fe(2)(NPh(2))(2)[tBuN(SiMe(2))](2)O] (5). Some redox chemistry is also observed as side reactions in the syntheses of 2-4, yielding THF adducts of FeX(2): the one-dimensional chain [FeBr(2)(THF)(2)](n) (7) and the cluster [Fe(4)Cl(8)(THF)(6)]. The X-ray crystal structures of 3, 5 and 7 are described.     

Homolysis of the Ln-N (Ln = Yb, Eu) bond. Synthesis, structural characterization and catalytic activity of ytterbium(II) and europium(II) complexes with methoxyethyl functionalized indenyl ligands

The interaction of methoxyethyl functionalized indene compounds (C(9)H(6)-1-R-3-CH(2)CH(2)OMe, R =t-BuNHSiMe(2)(1), Me(3)Si (2), H (3)) with [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5)) produced a series of new ytterbium(II) and europium(II) complexes via tandem silylamine elimination/homolysis of the Ln-N (Ln=Yb, Eu) bond. Treatment of the lanthanide(III) amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5) with 2 equiv. of, 1,2 and 3, respectively, produced, after workup, the ytterbium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Yb(II) (6), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Yb(II) (7), (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Yb(II)(8) and the corresponding europium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Eu(II)(9), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Eu(II)(10) and (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Eu(II)(11) in moderate to good yield. In contrast, interaction of the corresponding indene compounds 1, 2 or 3 with the lanthanide amides [(Me(3)Si)(2)N](3)Ln (Ln = Yb, Eu) was not observed, while addition of 0.5 equiv. of anhydrous LiCl to the corresponding reaction mixture produced, after workup, the corresponding ytterbium(II) or europium(II) complexes. All the new compounds were fully characterized by spectroscopic and elemental analyses. The structures of complexes, and were determined by single-crystal X-ray analyses. The catalytic activity of all the ytterbium(II) and europium(II) complexes on MMA polymerization was examined. It was found that all the ytterbium(II) and europium(II) complexes can function as single-component MMA polymerization catalysts. The temperature, solvent and ligand effects on the catalytic activity were studied.