Molecular nitrides with titanium and rare-earth metals

A series of titanium-group 3/lanthanide metal complexes have been prepared by reaction of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] (1) with halide, triflate, or amido derivatives of the rare-earth metals. Treatment of 1 with metal halide complexes [MCl(3)(thf)(n)] or metal trifluoromethanesulfonate derivatives [M(O(3)SCF(3))(3)] at room temperature affords the cube-type adducts [X(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (X = Cl, M = Sc (2), Y (3), La (4), Sm (5), Er (6), Lu (7); X = OTf, M = Y (8), Sm (9), Er (10)). Treatment of yttrium (3) and lanthanum (4) halide complexes with 3 equiv of lithium 2,6-dimethylphenoxido [LiOAr] produces the aryloxido complexes [(ArO)(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (M = Y (11), La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe(3))(2)}(3)] in toluene at 85-180 °C to afford the corner-shared double-cube nitrido compounds [M(μ(3)-N)(3)(μ(3)-NH)(3){Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}(2)] (M = Sc (13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe(3))(2) elimination. A single-cube intermediate [{(Me(3)Si)(2)N}Sc{(μ(3)-N)(2)(μ(3)-NH)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium bis(trimethylsilyl)amido derivative [Sc{N(SiMe(3))(2)}(3)]. The X-ray crystal structures of 2, 7, 11, 14, 15, and 19 have been determined. The thermal decomposition in the solid state of double-cube nitrido complexes 14, 15, and 18 has been investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements, as well as by pyrolysis experiments at 1100 °C under different atmospheres (Ar, H(2)/N(2), NH(3)) for the yttrium complex 14.     

Postfunctionalization of periodic mesoporous silica SBA-1 with magnesium(II) and iron(II) silylamides

Magnesium silylamide complexes Mg[N(SiHMe(2))(2)](2)(THF)(2) and Mg[N(SiPhMe(2))(2)](2) were synthesized according to transsilylamination and alkane elimination protocols, respectively, utilizing Mg[N(SiMe(3))(2)](2)(THF)(2) and [Mg(n-Bu)](2) as precursors. Cage-like periodic mesoporous silica SBA-1 was treated with donor solvent-free dimeric [Mg{N(SiHMe(2))(2)}(2)](2), [Mg{N(SiMe(3))(2)}(2)](2) and monomeric Mg[N(SiPhMe(2))(2)](2), producing hybrid materials [Mg(NR(2))(2)]@SBA-1 with magnesium located mainly at the external surface. Consecutive grafting of [Mg{N(SiHMe(2))(2)}(2)](2) and [Fe(II){N(SiHMe(2))(2)}(2)](2) onto SBA-1 led to heterobimetallic hybrid materials which exhibit complete consumption of the isolated surface silanol groups, evidencing intra-cage surface functionalization. All materials were characterized by DRIFT spectroscopy, nitrogen physisorption and elemental analysis.     

Synthesis and characterization of new biphenolate and binaphtholate rare-Earth-metal amido complexes: catalysts for asymmetric olefin hydroamination/cyclization

Monomeric diolate amido yttrium complexes [Y[diolate][N(SiHMe(2))(2)](thf)(2)] can be prepared in good yield by treating [Y[N(SiHMe(2))(2)](3)(thf)(2)] with either 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diol (H(2)(Biphen)), 3,3'-bis(2,4,6-triisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Trip(2)BINO)) or 3,3'-bis(2,6-diisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Dip(2)BINO)) in racemic and enantiopure form. The racemic complex [Y(biphen)[N(SiHMe(2))(2)](thf)(2)] dimerizes upon heating to give the heterochiral complex (R,S)-[Y(biphen)[N(SiHMe(2))(2)](thf)](2). The corresponding dimeric heterochiral lanthanum complex was the sole product in the reaction of H(2)(Biphen) with [La[N(SiHMe(2))(2)](3)(thf)(2)]. Single-crystal X-ray diffraction of both dimeric complexes revealed that the two Ln(biphen)[N(SiHMe(2))(2)](thf) fragments are connected through bridging phenolate groups of the biphenolate ligands. The two different phenolate groups undergo an intramolecular exchange process in solution leading to their equivalence on the NMR timescale. All complexes were active catalysts for the hydroamination/cyclization of aminoalkynes and aminoalkenes at elevated temperature, with [Y((R)-dip(2)bino)[N(SiHMe(2))(2)](thf)(2)] being the most active one giving enantioselectivities of up to 57 % ee. Kinetic resolution of 2-aminohex-5-ene proceeded with this catalyst with 6.4:1 trans selectivity to give 2,5-dimethylpyrrolidine with a k(rel) of 2.6.     

The synthesis and characterization of mono and dinuclear group 13 complexes derived from a Schiff base

The coordination preferences of the tetradentate Schiff base, N,N'-ethylenebis(acetylacetoimine), H(2)L, with a variety of group 13 precursors, led to the formation of a series of mono and binuclear products. The reaction of H(2)L with AlMe(3) and Me(2)GaCl afforded the binuclear complexes, [L{Al(Me)(2)}(2)] 1 and [H(2)L{GaCl(Me)(2)}(2)], 3, the latter an adduct of the neutral ligand. Treatment of 1 with iodine generated the cationic Al(III) complex, [LAl(thf)(2)]I, 2, while the addition of n-BuLi to H(2)L, followed by reaction with GaCl(3) and InCl(3) led to an ionic complex [{LGaCl}(2)(μLi)]GaCl(4), 4, an In(III) dimer, [LInCl](2), 5 and monomeric [LInCl(thf)], 6. In contrast, the reaction of [In{N(SiMe(3))(2)}(3)] with H(2)L yielded a homoleptic, air stable, indium complex, [L(3)In(2)], 7. All products were definitively characterized by X-ray crystallography and their structures confirmed by pertinent spectroscopic techniques.     

Synthesis and structures of some new types of lithium beta-diketiminates

The tetracyclic dilithio-Si,Si'-oxo-bridged bis(N,N'-methylsilyl-beta-diketiminates) 2 and 3, having an outer LiNCCCNLiNCCCN macrocycle, were prepared from [Li{CH(SiMe(3))SiMe(OMe)(2)}](infinity) and 2 PhCN. They differ in that the substituent at the beta-C atom of each diketiminato ligand is either SiMe(3) (2) or H (3). Each of and has (i) a central Si-O-Si unit, (ii) an Si(Me) fragment N,N'-intramolecularly bridging each beta-diketiminate, and (iii) an Li(thf)(2) moiety N,N'-intermolecularly bridging the two beta-diketiminates (thf = tetrahydrofuran). Treatment of [Li{CH(SiMe(3))(SiMe(2)OMe)}](8) with 2Me(2)C(CN)(2) yielded the amorphous [Li{Si(Me)(2)((NCR)(2)CH)}](n) [R = C(Me)(2)CN] (4). From [Li{N(SiMe(3))C(Bu(t))C(H)SiMe(3)}](2) (A) and 1,3- or 1,4-C(6)H(4)(CN)(2), with no apparent synergy between the two CN groups, the product was the appropriate (mu-C(6)H(4))-bis(lithium beta-diketiminate) 6 or 7. Reaction of [Li{N(SiMe(3))C(Ph)=C(H)SiMe(3)}(tmeda)] and 1,3-C(6)H(4)(CN)(2) afforded 1,3-C(6)H(4)(X)X' (X =CC(Ph)N(SiMe3)Li(tmeda)N(SiMe3)CH; X' = CN(SiMe3)Li(tmeda)NC(Ph)=C(H)SiMe3)(9). Interaction of A and 2[1,2-C(6)H(4)(CN)(2)] gave the bis(lithio-isoindoline) derivative [C6H4C(=NH)N{Li(OEt2)}C=C(SiMe3)C(Bu(t))=N(SiMe3)]2 (5). The X-ray structures of 2, 3, 5 and 9 are presented, and reaction pathways for each reaction are suggested.     

Surface organobarium and organomagnesium chemistry on periodic mesoporous silica MCM-41: convergent and sequential approaches traced by molecular models

The alkaline earth metal alkyl complexes [Ba(AlEt(4))(2)](n) and Mg(AlMe(4))(2) were directly grafted onto periodic mesoporous silica MCM-41, which had been dehydroxylated at 270 °C (specific surface area a(s): 1023 m(2) g(-1); pore volume V(p): 1.08 cm(3) g(-1); main pore diameter 3.4 nm). Alternatively, barium alkyl surface species were generated by sequential grafting of MCM-41 with Ba[N(SiHMe(2))(2)](2)(thf)(4) and AlEt(3) to yield the hybrid material AlEt(3)@Ba[N(SiHMe(2))(2)](2)(thf)(4)@MCM-41. For a better understanding of the surface chemistry, AlEt(3)@MCM-41 was also accessed. All hybrid materials were analyzed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, nitrogen physisorption, and solid-state NMR spectroscopy; this clearly revealed distinct surface chemistry for the alkylaluminate-treated materials [Ba(AlEt(4))(2)]@MCM-41 and Mg(AlMe(4))(2)@MCM-41. In an attempt to mimic the surface chemistry, the organometallic precursors were treated with HOSi(OtBu)(3). The reaction of equimolar amounts of {Ba[N(SiHMe(2))(2)](2)}(n) and HOSi(OtBu)(3) produced a mixed silylamido/siloxide cluster of Ba(3)[OSi(OtBu)(3)](3)[N(SiHMe(2))(2)](3) with bridging-only siloxide ligands as well as one bridging and two terminal silylamido ligands. The Schlenk equilibrium was found to govern the [Ba(AlEt(4))(2)](n)-HOSi(OtBu)(3) and Mg(AlMe(4))(2)-HOSi(OtBu)(3) reactions, leading to the isolation of complexes of [Ba(AlEt(4))(2) (toluene)](2) and Mg[OSi(OtBu)(3))](2)(AlMe(3))(2), respectively. Allowing for a donor-induced cleavage of Mg(AlMe(4))(2), the reaction of [MgMe(2)] with one or two equivalents of HOSi(OtBu)(3) was studied. While putative Mg[OSi(OtBu)(3)](Me) and Mg[OSi(OtBu)(3)](2) could not be crystallized from the reaction mixtures, cluster complexes Mg(5)(O)[OSi(OtBu)(3)](5)Me(3) and Mg(4)(OH)(2)[OSi(OtBu)(3)](6) could be unambiguously identified by X-ray crystallography.     

Synthesis and structures of the C5Me4SiMe3-supported polyhydride complexes over the full size range of the rare earth series

The acid-base reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] with Cp'H gave the corresponding half-sandwich rare earth dialkyl complexes [(Cp')Ln(CH(2)SiMe(3))(2)(thf)] (1-Ln: Ln=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp'=C(5)Me(4)SiMe(3)) in 62-90% isolated yields. X-ray crystallographic studies revealed that all of these complexes adopt a similar overall structure, in spite of large difference in metal-ion size. In most cases, the hydrogenolysis of the dialkyl complexes in toluene gave the tetranuclear octahydride complexes [{(Cp')Ln(μ-H)(2)}(4)(thf)(x)] (2-Ln: Ln=Sc, x=0; Y, x=1; Er, x=1; Tm, x=1; Gd, x=1; Dy, x=1; Ho, x=1) as the only isolable product. However, in the case of Lu, a trinuclear pentahydride [(Cp')(2)Lu(3)(μ-H)(5)(μ-CH(2)SiMe(2)C(5)Me(4))(thf)(2)] (3), in which the C-H activation of a methyl group of the Me(3)Si unit on a Cp' ligand took place, was obtained as a major product (66% yield), in addition to the tetranuclear octahydride [{(Cp')Lu(μ-H)(2)}(4)(thf)] (2-Lu, 34%). The use of hexane instead of toluene as a solvent for the hydrogenolysis of 1-Lu led to formation of 2-Lu as a major product (85%), while a similar reaction in THF yielded 3 predominantly (90%). The tetranuclear octahydride complexes of early (larger) lanthanide metals [{Cp'Ln(μ-H)(2)}(4)(thf)(2)] (2, Ln=La, Ce, Pr, Nd, Sm) were obtained in 38-57% isolated yields by hydrogenolysis of the bis(aminobenzyl) species [Cp'Ln(CH(2)C(6)H(4)NMe(2)-o)(2)], which were generated in-situ by reaction of [Ln(CH(2)C(6)H(4)NMe(2)-o)(3)] with one equivalent of Cp'H. X-ray crystallographic studies showed that the fine structures of these hydride clusters are dependent on the size of the metal ions.     

Syntheses, structures and reactions of a series of beta-diketiminatoyttrium compounds

This paper describes the synthesis and selected reactions of a series of crystalline mono(beta-diiminato)yttrium chlorides , , , , , , and . The X-ray structure of each has been determined, as well as of [YCl()(2)] (), [Y()(2)OBu(t)] () and [Y{CH(SiMe(3))(2)}(thf)(mu-Cl)(2)Li(OEt(2))(2)(mu-Cl)](2) (). The N,N'-kappa(2)-beta-diiminato ligands were [{N(R)C(Me)}(2)CH](-) [R = C(6)H(4)Pr(i)-2 (); R = C(6)H(4)Bu(t)-2 (); R = C(6)H(3)Pr(i)(2)-2,6 ()], [{N(SiMe(3))C(Ph)}(2)CH)](-) () and [{N(C(6)H(3)Pr(i)(2)-2,6)C(H)}(2)CPh](-) (). Equivalent portions of Li[L(x)] and YCl(3) in Et(2)O under mild conditions yielded [Y(mu-Cl)(L(x))(mu-Cl)(2)Li(OEt(2))(2)](2) [L(x) = () or ()] and [Y(mu-Cl)()(mu-Cl)Li(OEt(2))(2)(mu-Cl)](2) () or its thf (instead of Et(2)O) equivalent . Each of the Li(OEt(2))(2)Cl(2) moieties is bonded in a terminal () or bridging () mode with respect to the two Y atoms; the difference is attributed to the greater steric demand of than or . Under slightly more forcing conditions, YCl(3) and Li() (via) gave the lithium-free complex [YCl(2)()(thf)(2)] (). Two isoleptic compounds and (having in place of in , and , respectively) were obtained from YCl(3) and an equivalent portion of K[] and Na[], respectively; under the same conditions using Na[], the unexpected product was [YCl()(2)] () (i.e. incorporating only one half of the YCl(3)). A further unusual outcome was in the formation of from and 2 Li[CH(SiMe(3))(2)]. Compound [Y(){N(H)C(6)H(3)Pr(i)(2)-2,6}(thf)(mu(3)-Cl)(2)K](2).4Et(2)O (), obtained from and K[N(H)C(6)H(3)Pr(i)(2)-2,6], is noteworthy among group 3 or lanthanide metal (M) compounds for containing MClKCl (M = Y) moieties.     

Rare-earth-metal-hydrocarbyl complexes bearing linked cyclopentadienyl or fluorenyl ligands: synthesis, catalyzed styrene polymerization, and structure-reactivity relationship

A series of rare-earth-metal-hydrocarbyl complexes bearing N-type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized. Treatment of [Y(CH(2)SiMe(3))(3)(thf)(2)] with equimolar amount of the electron-donating aminophenyl-Cp ligand C(5)Me(4)H-C(6)H(4)-o-NMe(2) afforded the corresponding binuclear monoalkyl complex [({C(5)Me(4)-C(6)H(4)-o-NMe(μ-CH(2))}Y{CH(2)SiMe(3)})(2)] (1a) via alkyl abstraction and C-H activation of the NMe(2) group. The lutetium bis(allyl) complex [(C(5)Me(4)-C(6)H(4)-o-NMe(2))Lu(η(3)-C(3)H(5))(2)] (2b), which contained an electron-donating aminophenyl-Cp ligand, was isolated from the sequential metathesis reactions of LuCl(3) with (C(5)Me(4)-C(6)H(4)-o-NMe(2))Li (1 equiv) and C(3)H(5)MgCl (2 equiv). Following a similar procedure, the yttrium- and scandium-bis(allyl) complexes, [(C(5)Me(4)-C(5)H(4)N)Ln(η(3)-C(3)H(5))(2)] (Ln=Y (3a), Sc (3b)), which also contained electron-withdrawing pyridyl-Cp ligands, were also obtained selectively. Deprotonation of the bulky pyridyl-Flu ligand (C(13)H(9)-C(5)H(4)N) by [Ln(CH(2)SiMe(3))(3)(thf)(2)] generated the rare-earth-metal-dialkyl complexes, [(η(3)-C(13)H(8)-C(5)H(4)N)Ln(CH(2)SiMe(3))(2)(thf)] (Ln=Y (4a), Sc (4b), Lu (4c)), in which an unusual asymmetric η(3)-allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium-trisalkyl complex [Y(CH(2)C(6)H(4)-o-NMe(2))(3)], the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η(3)-C(13)H(8)-C(5)H(4)N)Y(CH(2)C(6)H(4)-o-NMe(2))(2)] (5). Complexes 1-5 were fully characterized by (1)H and (13)C NMR and X-ray spectroscopy, and by elemental analysis. In the presence of both [Ph(3)C][B(C(6)F(5))(4)] and AliBu(3), the electron-donating aminophenyl-Cp-based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph(3)C][B(C(6)F(5))(4)] only, the electron-withdrawing pyridyl-Cp-based complexes 3, in particular scandium complex 3b, exhibited outstanding activitiy to give perfectly syndiotactic (rrrr >99%) polystyrene, whereas their bulky pyridyl-Flu analogues (4 and 5) in combination with [Ph(3)C][B(C(6)F(5))(4)] and AliBu(3) displayed much-lower activity to afford syndiotactic-enriched polystyrene.     

Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] (Ln=Y, Yb, and Lu) with one equivalent of Me(2)Si(C(5)Me(4)H)NHR' (R'=Ph, 2,4,6-Me(3)C(6)H(2), tBu) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me(2)Si(C(5)Me(4))(NR')}Ln(CH(2)SiMe(3))(thf)(n)] (1: Ln = Y, R' = Ph, n=2; 2: Ln = Y, R' = C(6)H(2)Me(3)-2,4,6, n=1; 3: Ln = Y, R' = tBu, n=1; 4: Ln = Yb, R' = Ph, n=2; 5: Ln = Lu, R' = Ph, n=2) in high yields. These complexes, especially the yttrium complexes 1-3, serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a series of guanidine derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C[triple chemical bond]N, C[triple chemical bond]CH, and aromatic C--X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN==C==NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y(NEt(2))(thf)(2)] (40) and [{Me(2)Si(C(5)Me(4))(NPh)}Y(NHC(6)H(4)Br-4)(thf)(2)] (42), and the guanidinate complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrNC(NEt(2))(NiPr)}(thf)] (41) and [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrN}C(NC(6)H(4)Br-4)(NHiPr)}(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed by acid-base reaction between a rare-earth metal alkyl bond and an amine N--H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.     

Synthesis and structures of the [benzamidinato]3- complexes Li3(tmeda)(L1)]2 and [Li(thf)4][Li5(L2)(OEt2)2] [L1 = N(SiMe3)C(Ph)N(SiMe3) and L2 = N(SiMe3)C(C6H4-4)NPh

Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis.     

A slipped multi-decker zirconium complex with an η7:η2-bridging cycloheptatrienyl ligand

The complex [(η(7)-C(7)H(7))Zr{N(SiMe(3))(2)}(thf)] (2) loses THF upon sublimation to afford a chain polymer consisting of [(η(7)-C(7)H(7))Zr{N(SiMe(3))(2)}] (3) units; they are connected by cycloheptatrienyl ligands in an unprecedented antifacial η(7):η(2)-bridging mode. The basicity of the bis(trimethylsilyl)amido ligand can also be used to introduce other ligands by acid-base reactions.     

BiPh3--a convenient synthon for heavy alkaline-earth metal amides

Environmentally friendly, commercially available BiPh(3) reacts with heavy alkaline-earth metals (Ae) and bulky trimethylsilylamines to give the corresponding amides [Ae{N(SiMe(3))(R)}(2)(thf)(n)] (R = SiMe(3), 2,4,6-Me(3)C(6)H(2), 2,6-(i)Pr(2)C(6)H(3)) in good yields, providing proof of concept for a general synthetic method.     

Iron silylamide-grafted periodic mesoporous silica

The surface chemistry of a series of well-defined metalorganic ferrous and ferric iron complexes on periodic mesoporous silica (PMS) was investigated. In addition to literature known Fe(II)[N(SiMe(3))(2)](2)(THF), Fe(II)[N(SiPh(2)Me(2))(2)](2), and Fe(III)[N(SiMe(3))(2)](2)Cl(THF), the new complexes [Fe(II){N(SiHMe(2))(2)}(2)](2) and Fe(III)[N(SiHMe(2))(2)](3)(μ-Cl)Li(THF)(3) were employed as grafting precursors. Selection criteria for the molecular precursors were the molecular size (monoiron versus diiron species), the oxidation state of the iron center (II versus III), and the functionality of the silylamido ligand (e.g., built-in spectroscopic probes). Hexagonal channel-like MCM-41 and cubic cage-like SBA-1 were chosen as two distinct PMS materials. The highest iron load (12.8 wt %) was obtained for hybrid material [Fe(II){N(SiHMe(2))(2)}(2)](2)@MCM-41 upon stirring the reaction mixture iron silylamide/PMS/n-hexane for 18 h at ambient temperature. Size-selective grafting and concomitantly extensive surface silylation were found to be prominent for cage-like SBA-1. Here, the surface metalation is governed by the type of iron precursor, the pore size, the reaction time, and the solvent. The formation of surface-attached iron-ligand species is discussed on the basis of diffuse reflectance infrared Fourier transform (DRIFT) and electron paramagnetic resonance (EPR) spectroscopy, nitrogen physisorption, and elemental analysis.     

Highly efficient ethylene polymerisation by scandium alkyls supported by neutral fac-kappa3 coordinated N3 donor ligands

Reaction of [M(CH2SiMe3)3(THF)2] (M = Sc or Y) with the neutral fac-kappa3 N3 donor ligands (L) Me3[9]aneN3 or HC(Me2pz)3 gave the corresponding trialkyls [M(L)(CH2SiMe3)3]; activation of the scandium congeners with B(C6F5)3 in the presence of ethylene afforded highly active polymerisation catalysts (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).     

Living photolytic ring-opening polymerization of amino-functionalized [1]ferrocenophanes: synthesis and layer-by-layer self-assembly of well-defined water-soluble polyferrocenylsilane polyelectrolytes

Facile synthetic routes have been developed that provide access to cationic and anionic water-soluble polyferrocenylsilane (PFS) polyelectrolytes with controlled molecular weight and narrow polydispersity. Living photolytic ring-opening polymerization of amino-functionalized [1]ferrocenophane (fc) monomers [fcSiMe{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}] (3), [fcSi{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}(2)] (10), [fcSiMe(C[triple chemical bond]CCH(2)NMe(2))] (14), and [fcSiMe(p-C(6)H(4)CH(2)NMe(2))] (20) yielded the corresponding polyferrocenylsilanes [(fcSiMe{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)})(n)](5), [(fcSi{C[triple chemical bond]CCH(2)N(SiMe(2)CH(2))(2)}(2))(n)] (11), [{fcSiMe(C[triple chemical bond]CCH(2)NMe(2))}(n)] (15), and [{fcSiMe(p-C(6)H(4)CH(2)NMe(2))}(n)] (21) with controlled architectures. Further derivatization of 5, 15, and 21 generated water-soluble polyelectrolytes [(fcSiMe{C[triple chemical bond]CCH(2)N(CH(2)CH(2)CH(2)SO(3)Na)(2)})(n)] (6), [{fcSiMe(C[triple chemical bond]CCH(2)NMe(3)OSO(3)Me)}(n)] (7), and [{fcSiMe(p-C(6)H(4)CH(2)NMe(3)OSO(3)Me)}(n)] (22), respectively. The polyelectrolytes were readily soluble in water and NaCl aqueous solutions, with 6 and 22 exhibiting long-term stability in aqueous media. The PFS materials 6 and 22, have been utilized in the layer-by-layer (LbL) self-assembly of electrostatic superlattices. Our preliminary studies have indicated that films made from controlled low molecular-weight PFSs possess a considerably thinner bilayer thickness and higher refractive index than those made from PFSs that have an uncontrolled high molecular-weight. These results suggest that the structure and optical properties of LbL ultra-thin films can be tuned by varying polyelectrolyte chain length. The water-soluble low molecular weight PFSs are also useful materials for a range of applications including LbL self-assembly in highly confined spaces.     

First complexes of scandium and yttrium with NNO and NNS heteroscorpionate ligands

The reaction of ScCl(3)(THF)(3) or YCl(3) in a 1:1 molar ratio under reflux for 8 h with [{Li(bdmpza)(H(2)O)}(4)] [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], [{Li(bdmpzdta)(H(2)O)}(4)] [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], and (Hbdmpze) [bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] affords the corresponding complexes [MCl(2)(kappa(3)-bdmpzx)(THF)] (x = a, M = Sc (1), Y (2); x = dta, M = Sc (3), Y (4); x = e, M = Sc (5), Y (6)). However, when the reaction was carried out for 1 h under reflux between ScCl(3)(THF)(3) and [{Li(bdmpzdta)(H(2)O)}(4)], a new anionic complex [Li(THF)(4)][ScCl(3)(kappa(3)-bdmpzdta)] (7) was obtained. Reaction of [{Li(bdmpza)(H(2)O)}(4)] with YCl(3) in a 2:1 molar ratio under reflux for 8 h gave the complex [YCl(kappa(3)-bdmpza)(2)] (8). The same reaction, but with the lithium compound [{Li(bdmpzdta)(H(2)O)}(4)], led to the formation of an anionic complex [Li(THF)(4)][YCl(3)(kappa(3)-bdmpzdta)] (9). The X-ray crystal structures of 7 and 9 were established. Finally, the addition of 1 equiv of [{Li(bdmpza)(H(2)O)}(4)] or [{Li(bdmpzdta)(H(2)O)}(4)] to a solution of YCl(3) in THF under reflux, followed by the addition of 1 equiv of 1,10-phenanthroline, resulted in the formation of the corresponding complexes [YCl(2)(kappa(3)-bdmpzx)(phen)] (x = a (10), x = dta (11)). These complexes are the first examples of group 3 metals stabilized by heteroscorpionate ligands. In addition, we have explored the reactivity of some of these complexes with alcohols and amides. For example, the direct reaction of [YCl(2)(kappa(3)-bdmpza)(THF)] (2) with several alcohols gave the alkoxide complexes [YCl(kappa(3)-bdmpza)(OR)] (R = Et (12), iPr (13)). Finally, the reaction between [ScCl(2)(kappa(3)-bdmpzdta)(THF)] (3) or [Li(THF)(4)][ScCl(3)(kappa(3)-bdmpzdta)] (7) and LiN(SiMe(3))(2).Et(2)O in 1:1 and 1:2 molar ratios gave rise to the complexes [ScCl(kappa(3)-bdmpzdta){N(SiMe(3))(2)}] (14) and [Sc(kappa(3)-bdmpzdta){N(SiMe(3))(2)}(2)] (15), respectively.     

Group 3 and lanthanide boryl compounds: syntheses, structures, and bonding analyses of Sc-B, Y-B, and Lu-B σ-coordinated NHC analogues

Reaction of [Ln(CH(2)SiMe(3))(2)(THF)(n)][BPh(4)] (Ln = Sc, Y, Lu ; n = 3, 4) with Li{B(NArCH)(2)}(THF)(2) (Ar = 2,6-C(6)H(3)(i)Pr(2)) formed the first group 3 and lanthanide boryl compounds, Sc{B(NArCH)(2)}(CH(2)SiMe(3))(2)(THF) and Ln{B(NArCH)(2)}(CH(2)SiMe(3))(2)(THF)(2) (Ln = Y, Lu), which contain two-center, two-electron Ln-B σ bonds. All of these systems were crystallographically characterized. Density functional theory analysis of the Ln-B bonding found it to be predominantly ionic, with covalent character in the σ-bonding Ln-B HOMO.     

Synthesis and reactivity of rare earth metal alkyl complexes stabilized by anilido phosphinimine and amino phosphine ligands

Anilido phosphinimino ancillary ligand H(2)L(1) reacted with one equivalent of rare earth metal trialkyl [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L(1)LnCH(2)Si(CH(3))(3)(THF)] (1 a: Ln=Y; 1 b: Ln=Lu). In this process, deprotonation of H(2)L(1) by one metal alkyl species was followed by intramolecular C--H activation of the phenyl group of the phosphine moiety to generate dianionic species L(1) with release of two equivalnts of tetramethylsilane. Ligand L(1) coordinates to Ln(3+) ions in a rare C,N,N tridentate mode. Complex l a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL(1))LnY(NHC(6)H(3)iPr(2)-2,6)(2)] (2) selectively, that is, the C--H activation of the phenyl group is reversible. When 1 a was exposed to moisture, the hydrolyzed dimeric complex [{(HL(1))Y(OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] with amino phosphine ligands HL(2-R) gave stable rare earth metal bis-alkyl complexes [(L(2-R))Ln{CH(2)Si(CH(3))(3)}(2)(thf)] (4 a: Ln=Y, R=Me; 4 b: Ln=Lu, R=Me; 4 c: Ln=Y, R=iPr; 4 d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4 a and 4 c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L(2-R))Y(NHC(6)H(3)iPr(2)-2,6)(2)(thf)] (5 a: R=Me; 5 b: R=iPr). Complexes 1 a,b and 4 a-d initiated the ring-opening polymerization of d,l-lactide with high activity to give atactic polylactides.     

Reactions of [Et(4)N](3)[Sb{Fe(CO)(4)}(4)] with Alkyl Halides and Dihalides: Formation of the Alkyl- and the Dialkylantimony-Iron Carbonyl Complexes

The reactions of [Et(4)N](3)[Sb{Fe(CO)(4)}(4)] (1) with RX (R = Me, Et, n-Pr; X = I) in MeCN form the monoalkylated antimony complexes [Et(4)N](2)[RSb{Fe(CO)(4)}(3)] (R = Me, 2; R = Et, 4; R = n-Pr, 6) and the dialkylated antimony clusters [Et(4)N][R(2)Sb{Fe(CO)(4)}(2)] (R = Me, 3; R = Et, 5; R = n-Pr, 7), respectively. When [Et(4)N](3)[Sb{Fe(CO)(4)}(4)] reacts with i-PrI, only the monoalkylated antimony complex [Et(4)N](2)[i-PrSb{Fe(CO)(4)}(3)] (8) is obtained. The mixed dialkylantimony complex [Et(4)N][MeEtSb{Fe(CO)(4)}(2)] (9) also can be synthesized from the reaction of 2 with EtI. While the reaction with Br(CH(2))(2)Br produces [Et(4)N](2)[BrSb{Fe(CO)(4)}(3)] (10), treatment with Cl(CH(2))(3)Br forms the monoalkylated product [Et(4)N](2)[Cl(CH(2))(3)Sb{Fe(CO)(4)}(3)] (11) and a dialkylated novel antimony-iron complex [Et(4)N][{&mgr;-(CH(2))(3)}Sb{Fe(CO)(4)}(3)] (12). On the other hand, the reaction with Br(CH(2))(4)Br forms the monoalkylated antimony product and the dialkylated antimony complex [Et(4)N][{&mgr;-(CH(2))(4)}Sb{Fe(CO)(4)}(2)] (13). Complexes 2-13 are characterized by spectroscopic methods or/and X-ray analyses. On the basis of these analyses, the core of the monoalkyl clusters consists of a central antimony atom tetrahedrally bonded to one alkyl group and three Fe(CO)(4) fragments and the dialkyl products are structurally similar to the monoalkyl clusters, with the central antimony bonded to two alkyl groups and two Fe(CO)(4) moieties in each case. The dialkyl complex 3 crystallizes in the monoclinic space group P2(1)/c with a = 13.014(8) ?, b = 11.527(8) ?, c = 17.085(5) ?, beta = 105.04(3) degrees, V = 2475(2) ?(3), and Z = 4. Crystals of 12 are orthorhombic, of space group Pbca, with a = 14.791(4) ?, b = 15.555(4) ?, c = 27.118(8) ?, V = 6239(3) ?(3), and Z = 8. The anion of cluster 12 exhibits a central antimony atom bonded to three Fe(CO)(4) fragments with a -(CH(2))(3)- group bridging between the Sb atom and one Fe(CO)(4) fragment. This paper discusses the details of the reactions of [Et(4)N](3)[Sb{Fe(CO)(4)}(4)] with a series of alkyl halides and dihalides. These reactions basically proceed via a novel double-alkylation pathway, and this facile methodology can as well provide a convenient route to a series of alkylated antimony-iron carbonyl clusters.