Reactions of Li- and Yb-coordinated N,N'-bis(trimethylsilyl)-beta-diketiminates: one- and two-electron reductions, deprotonation, and C-N bond cleavage

The synthesis and characterisation of novel Li and Yb complexes is reported, in which the monoanionic beta-diketiminato ligand has been (i) reduced (SET or 2 [times] SET), (ii) deprotonated, or (iii) C-N bond-cleaved. Reduction of the lithium beta-diketiminate Li(L(R,R'))[L(R,R')= N(SiMe(3))C(R)CHC(R')N(SiMe(3))] with Li metal gave the dilithium derivative [Li(tmen)(mu-L(R,R'))Li(OEt(2))](R = R'= Ph; or, R = Ph, R[prime or minute]= Bu(t)). When excess of Li was used the dimeric trilithium [small beta]-diketiminate [Li(3)(L(R,R[prime or minute]))(tmen)](2)(, R = R'= C(6)H(4)Bu(t)-4 = Ar) was obtained. Similar reduction of [Yb(L(R,R'))(2)Cl] gave [Yb[(mu-L(R,R'))Li(thf)](2)](, R = R[prime or minute]= Ph; or, R = R'= C(6)H(4)Ph-4 = Dph). Use of the Yb-naphthalene complex instead of Li in the reaction with [Yb(L(Ph,Ph))(2)] led to the polynuclear Yb clusters [Yb(3)(L(Ph,Ph))(3)(thf)], [Yb(3)(L(Ph,Ph))(2)(dme)(2)], or [Yb(5)(L(Ph,Ph))(L(1))(L(2))(L(3))(thf)(4)] [L(1)= N(SiMe(3))C(Ph)CHC(Ph)N(SiMe(2)CH(2)), L(2)= NC(Ph)CHC(Ph)H, L(3)= N(SiMe(2)CH(2))] depending on the reaction conditions and stoichiometry. The structures of the crystalline complexes 4, 6x21/2(hexane), 5(C(6)D(6)), and have been determined by X-ray crystallography (and have been published).     

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.     

Reactions between a sodium amide Na[N(SiMe3)R1] (R1 = SiMe3, SiMe2Ph or But) and a cyanoalkane RCN (R = Ad or Bu(t))

Reactions between sodium amides Na[N(SiMe3)R1] [R1 = SiMe3 (1), SiMe2Ph (2) or But (3)] and cyanoalkanes RCN (R = Ad or But) were investigated. In each case the nitrile adduct [Na{mu-N(SiMe3)2}(NCR)]2 [R = Ad (1a) or But (1b)], trans-[Na{mu-N(SiMe3)(SiMe2Ph)}(NCR)]2 [R = Ad (2a) or But (2b)], [(Na{mu-N(SiMe3)But})3(NCAd)3] (3a) or [(Na{mu-N(SiMe3)But})3(NCBut)n] [n = 3 (3b) or 2 (3c)] was isolated. The reaction of complexes 3a or 3b with benzene afforded the ketimido complex [Na{mu-N=C(Ad)(Ph)}]6.2C6H6 (4a) or [Na{mu-N=C(But)(Ph)}]6 (4b); the former was also prepared in more conventional fashion from NaPh and AdCN. The synthesis and structure of an analogue of complex 1a, [Li{mu-N(SiMe3)2}(NCAd)]2 (5a), is also presented. The compounds 1a, 1b, 2a, 2b, 3, 3b, 4a, 4b and 5a were characterised by X-ray diffraction.     

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.     

Synthesis and structures of crystalline Li, Al and Sn(II) 1-azaallyls and beta-diketiminates derived from [Li{mu,eta3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (Ad = 1-adamantyl)

The crystalline dimeric 1-azaallyllithium complex [Li{mu,eta(3-N(SiMe3)C(Ad)C(H)SiMe3}]2 (1) was prepared from equivalent portions of Li[CH(SiMe3)2] and 1-cyanoadamantane (AdCN). Complex was used as precursor to each of the crystalline complexes 2-8 which were obtained in good yield. By 1-azaallyl ligand transfer, 1 afforded (i) [Al{eta3-N(SiMe3)C(Ad)C(H)SiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (5) with [AlCl2Me](2), (ii) [Sn{eta3-N(SiMe3)C(Ad)C(H)SiMe3}2] (7) with Sn[N(SiMe3)2]2, and (iii) [Li(N{C(Ad)=C(H)SiMe3-E}{Si(NN)SiMe3})(thf)2] (8) with the silylene Si[(NCH(2)Bu(t))2C6H(4)-1,2] [= Si(NN)]. By insertion into the C[triple bond, length as m-dash]N bond of the appropriate cyanoarene RCN, gave the beta-diketiminate [Li{mu-N(SiMe3)C(Ad)C(H)C(R)NSiMe3}]2 [R = Ph (2), C(6)H(4)Me-4 (3)], and yielded [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}{kappa1-N(SiMe3)C(Ad)=C(H)SiMe3-E}Me] (6). The beta-diketiminate [Al{kappa2-N(SiMe3)C(Ad)C(H)C(Ph)NSiMe3}Me2] (4) was prepared from 2 and [AlClMe2]2. The X-ray structures of 1 and 3-8 are presented. Multinuclear NMR spectra in C6D6 or C6D5CD3 have been recorded for each of 1-8; such data on 8 revealed that in solution two minor isomers were also present.     

Synthetic and structural experiments on yttrium, cerium and magnesium trimethylsilylmethyls and their reaction products with nitriles; with a note on two cerium beta-diketiminates

The yttrium, cerium and magnesium bis(trimethylsilyl)methyls [Ln[CH(SiMe3)2]3][Ln = Y (1), Ce (2)], and the known compound Mg[[CH(SiMe3)2]2 (C) and [Mg(mu-Br)[CH(SiMe3)2](OEt2)]2 (D) formed the crystalline nitrile adducts [1(NCBut)2] (5), [2(NCPh)] (6), [C(NCR)2][R = But (8), Ph (9), C6H3Me2-2,6 (10)] and [Mg(mu-Br)[CH(SiMe3)2](NCR)]2 [R = But (11), Ph (12), C6H3Me2-2,6 (13)], rather than beta-diketiminato-metal insertion products. The beta-diketiminato-cerium complex [Ce[(N(SiMe3)C(C6H4But-4))2CH][N(SiMe3)2]2] (16) was obtained from [Ce[N(SiMe3)2]3] and the beta-diketimine H[[N(SiMe3)C(C6H4But-4)]2CH]]. The cerium alkyl 2 and [Ln[CH(SiMe3)(SiMe2OMe)]3][Ln = Y (3), Ce (4)] were obtained from the appropriate lithium alkyl precursor and [Ce(OC6H2But2-2,6-Me-4)3] or LnCl3, respectively. Heating complex 3 with benzonitrile in toluene afforded 2,2-dimethyl-4,6-diphenyl-5-trimethylsilyl-1,3-diaza-2-silahexa-1,3-diene (7), a member of a new class of heterocycles. The X-ray structures of the crystalline compounds, D, [Mg[CH(SiMe3)2]2(OEt2)2], the known [Ce(Cl)[(N(SiMe3)C(Ph))2CH]2] (E) and 16 are reported. The cerium alkyl (like 1) has one close Ce...C contact for each ligand, attributed to a gamma-C-Ce agostic interaction. The Ln alkyls and have a trigonal prismatic arrangement of the chelating ligands (each of the same chirality at Calpha) around the metal. In an arene solution at 313 K exists as two isomers, as evident from detailed NMR spectroscopic experiments.     

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.     

Synthesis, structure and hydrosilylation activity of neutral and cationic rare-earth metal silanolate complexes

Rare-earth metal alkyl tri(tert-butoxy)silanolate complexes [Ln{mu,eta2-OSi(O(t)Bu)3}(CH2SiMe3)2]2 (Ln = Y (1), Tb (2), Lu (3)) were prepared via protonolysis of the appropriate tris(alkyl) complex [Ln(CH2SiMe3)3(thf)2] with tri(tert-butoxy)silanol in pentane. Crystal structure analysis revealed a dinuclear structure for with square pyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an eta2-bridging coordination mode giving a 4-rung truncated ladder and non-crystallographic inversion centre. Addition of two equiv. of 12-crown-4 to a pentane solution of 1 or 3 respectively gave [Ln{OSi(O(t)Bu)(3)}(CH2SiMe3)2(12-crown-4)].12-crown-4 (Ln = Y (4), Lu (5)). Crystal structure analysis of 5 showed a slightly distorted octahedral geometry at the lutetium centre. The silanolate ligand adopts an eta(1)-terminal coordination mode, whilst the crown ether unit coordinates in an unusual kappa3-fashion. Reaction of 1-3 with [NEt3H]+[BPh4]- in thf yielded the cationic derivatives [Ln{OSi(O(t)Bu)3}(CH2SiMe3)(thf)4]+[BPh4]- (Ln = Y (6), Tb (7) and Lu (8)); coordination of crown ether led to compounds of the form [Ln{OSi(O(t)Bu)3}(CH2SiMe3)(L)(thf)n]+[BPh4]- (Ln = Y, Lu, L = 12-crown-4, n = 1 (9,10); Ln = Y, Lu, L = 15-crown-5, n = 0 (11,12)). Reaction of 1 with [NMe2PhH]+[B(C6F5)4]-, [Al(CH2SiMe3)3] or BPh3 in thf gave the ion pairs [Y{OSi(O(t)Bu)3}(CH2SiMe3)(thf)4]+[A]- ([A]- = [B(C6F5)4]- (13), [Al(CH2SiMe3)4]- (14), [BPh3(CH2SiMe3)]- (15)), whilst two equiv. [NMe2PhH]+[BPh4]- with 1 in thf produced the dicationic ion triple [Y{OSi(O(t)Bu)3}(thf)6]2+[BPh4]-2 (16). Crystal structure analysis revealed that 16 is mononuclear with pentagonal bipyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an eta(1)-terminal fashion. All diamagnetic compounds have been characterized by NMR spectroscopy. 1, 3, 4, 6 and 13 were tested as olefin hydrosilylation pre-catalysts with a variety of substrates; 1 was found to be highly active in 1-decene hydrosilylation.     

Electronic response of a (P,N)-based ligand on metal coordination

The reaction of [(THF)Li(Ph(2)PC(H)Py)] with ZnCl(2) in the presence of ZnO yields the zinc complex [Zn(3)(Ph(2)PC(H)Py)(4)O] (1). Deprotonation of the phosphane Ph(2)P(CH(2)Py) with [Fe(N(SiMe(3))(2))2] gives the iron complexes [(Ph(2)P(CH(2)Py))Fe(Ph(2)PC(H)Py)2] (2) and [Fe(Ph(2)PC(H)Py)(N(SiMe(3))(2))]2 (3), depending on the ratio of phosphane. The solid state structures of the metal complexes illustrate the coordination flexibility of the [Ph(2)C(H)Py](-)-anion. Depending on the electronic requirements of the coordinated metal the anion acts as a (P,N)-chelating amide or C-coordinating carbanion with the P- and N-heteroatoms as donor bases.     

An electrochemical and DFT study on selected beta-diketiminato metal complexes

Selected homoleptic metal beta-diketiminates M(I)L and M(II)L2 [M(I) = Li or K, M(II) = Mg, Ca or Yb; L: L(Ph) = [N(SiMe3)C(Ph)]2CH, L(Bu(t)) = N(SiMe3)C(Ph)C(H)C(Bu(t))N(SiMe3), L* = [N(C6H3Pr(i)2-2,6)C(Me)]2CH] have been studied by cyclic voltammetry (CV). The primary reduction (E(p)red, the peak reduction potential measured vs. SCE in thf containing 0.2 M [NBu4][PF6] with a scan rate 100 mV s(-1) at a vitreous carbon electrode at ambient temperature) is essentially ligand-centred: E(p)red being ca. -2.2 V (LiL(Ph) and KL(Ph)) and -2.4 V [Mg(L(Ph))2, LiL(Bu(t)) and Ca(L(Ph))2], while LiL* is significantly more resistant to reduction (E(p)red = -3.1 V). These observations are consistent with the view that the two (L(Ph)) or single (L(Bu(t))) C-phenyl substituent(s), respectively, are available for -electron-delocalisation of the reduced species, whereas the N-aryl substituents of L* are unable to participate in such conjugation for steric reasons. The primary reduction process was reversible on the CV-time scale only for LiL(Bu(t)), Ca(L(Ph))2 and Yb(L(Ph))2. For the latter this occurs at a potential ca. 500 mV positive of Ca(L(Ph))2, consistent with the notion that the LUMO of Yb(L(Ph))2 has substantial metal character. The successive reversible steps, each separated by ca. 500 mV, indicate that there is strong electronic communication between the two ligands of Yb(L(Ph))2. The overall three-electron transfer sequence shows that the final reduction level corresponds to [Yb(II)(L(Ph))2-(L(Ph))3-]. DFT calculations on complexes Li(L(Ph))(OMe2)2 and Li2(L(Ph))(OMe2)3 showed that both HOMO and LUMO orbitals are only based on the ligand with a HOMO-LUMO gap of 4.21 eV. Similar calculations on a doubly reduced complex Yb[(mu-L(Ph))Li(OMe2)]2 demonstrated that there is a considerable Yb atomic orbital contribution to the HOMO and LUMO of the complex.     

Synthesis and characterization of heterobimetallic oxo-bridged aluminum-rare earth metal complexes

Reaction of the aluminum hydroxide LAl(OH)[C(Ph)CH(Ph)] (1, L = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(6)H(3)) with Y(CH(2)SiMe(3))(3)(THF)(2) yielded the oxo-bridged heterobimetallic yttrium dialkyl complex LAl[C(Ph)CH(Ph)](μ-O)Y(CH(2)SiMe(3))(2)(THF)(2) (2). Alkane elimination reaction of 2 with 2-(imino)pyrrole [NN]H ([NN]H = 2-(ArN═CH)-5-tBuC(4)H(2)NH) afforded the yttrium monoalkyl complex LAl[C(Ph)CH(Ph)] (μ-O)Y(CH(2)SiMe(3))[NN](THF)(2) (5). Alternatively, 5 can be prepared in high yield by reaction of 1 with [NN]Y(CH(2)SiMe(3))(2)(THF)(2) (3). The analogous samarium alkyl complex LAl[C(Ph)CH(Ph)](μ-O)Sm(CH(2)SiMe(3))[NN](THF)(2) (6) was prepared similarly. Reactions of 5 and 6 with 1 equiv of iPrOH yielded the corresponding alkoxyl complexes 7 and 8, respectively. The molecular structures of 3, 6, and 8 have been determined by X-ray single-crystal analysis. Complexes 2, 3, 5, 7, and 8 have been investigated as lactide polymerization initiators. The heterobimetallic alkoxyl 8 is highly active to yield high molecular weight (M(n) = 6.91 × 10(4)) polylactides with over 91% conversion at the lactide-to-initiator molar ratio of 2000.     

Synthesis and structures of a 3-sila-beta-diketiminatomagnesium bromide, ketenimide and triflate

The crystalline compounds [Mg(Br)(L)(thf)].0.5Et2O [L = {N(R)C(C6H3Me2-2,6)}2SiR, R = SiMe3] (1), [Mg(L){N=C=C(C(Me)=CH)2CH2}(D)2] [D = NCC6H3Me2-2,6 (2), thf (3)] and [{Mg(L)}2{mu-OSO(CF3)O-[mu}2] (4) were prepared from (a) Si(Br)(R){C(C6H3Me2-2,6)=NR}2 and Mg for (1), (b) [Mg(SiR3)2(thf)2] and 2,6-Me2C6H3CN (5 mol for (2), 3 mol for (3)), and (c) (2) + Me3SiOS(O)2CF3 for (4); a coproduct from (c) is believed to have been the trimethylsilyl ketenimide Me3SiN=C=C{C(Me)=CH}2CH2 (5).     

Reactions of M[CH(SiMe3)2] (M = Na or K) with PhCN, and related chemistry

A number of metal complexes containing one of the following ligands: the 1-azaallyl [N(R)C(Ph)C(H)R]- ([triple bond]L-), the 1,3-diazaallyl([triple bond]LL'-) and the isomeric beta-diketiminate [{N(R)C(Ph)]}2CH]- ( identical with LL-) have been prepared (R = SiMe(3)). These are the crystalline compounds H(LL) (2), Na(LL) (3), [Na(LL)(thf)2] (4), Na(L) (6), [Na(mu-LL')]8 (7), [K(mu-L)(eta6-C6H6)]2 (8), [K(mu-LL')(thf)]2 (9), [K(thf)2(mu-LL)](infinity) (10) and [Ni(LL')2] (11). A new synthesis of Na[C(H)R2] (1) involved Hg[C(H)R2]2 and Na/Hg as reagents. The beta-diketimine 2 was obtained from Li(LL) and cyclopentadiene. Under different conditions compounds 3, 6 and 7 were isolated from 1 and benzonitrile, and compounds 8, 9 and 10 from K[C(H)R2] and PhCN. Complex 11 was derived from [Li(LL')]2 and [NiBr(2)(dme)]. The solution obtained from 1 + 2 PhCN in Et2O at ambient temperature was a mixture (5) of 3 (predominantly) and 7. The 1-azaallyl complex 8 has the ligand bound to the metal as the enamide, and this is also probably (NMR) the case for 6. The molecular structures of the crystalline complexes 7, 8 and 11 are presented; that of 10 was published earlier. Compound 7, a cyclooctamer, is particularly interesting, in that each LL'- ligand is bridging via one of its N atoms to two neighbouring sodium ions and is not only N,N'- but also (eta2-C[=]C)-chelating to one of them.     

Syntheses, structure, and derivatization of potassium complexes of penta(organo)[60]fullerene-monoanion, -dianion, and -trianion into hepta- and octa(organo)fullerenes

Two-electron reduction of penta(organo)[60]fullerenes C(60)Ar(5)H (Ar = Ph and biphenyl) by potassium/mercury amalgam afforded potassium complexes of the corresponding open-shell radical dianions [K+(thf)n]2[C60Ar5(2-.)]. These compounds were characterized by UV-visible-near-IR and electron spin resonance spectroscopy in solution. Anaerobic crystallization of [K+(thf)n]2[C60(biphenyl)(5)(2-.)] that exists largely as a monomer in solution gave black crystals of its dimer [K+(thf)3]4[(biphenyl)5C60-C60(biphenyl)5(4-)], in which the two fullerene units are connected by a C-C single bond [1.577(11) A] as determined by X-ray diffraction. Three-electron reduction of C60Ar5H with metallic potassium gave a black-green trianion [K+(thf)n]3[C60Ar5(3-)]. The reaction of the trianion with an alkyl halide RBr (R = PhCH(2) and Ph(2)CH) regioselectively afforded a hepta-organofullerene C60Ar5R2H, from which a potassium complex [K+(thf)n][C60(biphenyl)5(CH2Ph)(2)(-)] and a palladium complex Pd[C60(biphenyl)5(CH2Ph)2](pi-methallyl) as well as octa-organofullerene compounds C60(biphenyl)5(CH2Ph)3H2 and Ru[C60(biphenyl)5(C2Ph)3H]Cp were synthesized. These compounds possess a dibenzo-fused corannulene pi-electron conjugated system and are luminescent.     

Scandium alkyl and amide complexes containing a cyclen-derived (NNNN) macrocyclic ligand: synthesis, structure and ring-opening polymerization activity toward lactide monomers

Cyclic polyamine 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, (Me(3)TACD)H (= Me(3)[12]aneN(4)), reacted with [K{N(SiHMe(2))(2)}] in benzene-d(6) to give [K{(Me(3)TACD)SiMe(2)N(SiHMe(2))}] (1) under hydrogen evolution. Single-crystal X-ray diffraction of 1 shows a dinuclear structure in the solid state, featuring a bridging μ-amido and a weak β-agostic Si-H bond. 1,7-Dimethyl-1,4,7,10-tetraazacyclododecane (Me(2)TACD)H(2) (= Me(2)[12]aneN(4)) and (Me(3)TACD)H were reacted with [Sc{N(SiHMe(2))(2)}(3)(thf)] in benzene-d(6) to give [{(Me(2)TACD)SiMe(2)N(SiHMe(2))}Sc{N(SiHMe(2))(2)}] (2) and [(Me(3)TACD)Sc{N(SiHMe(2))(2)}(2)SiMe(2)] (3), respectively. Both compounds are monomeric in solution and X-ray diffraction studies showed the scandium metal centers to be six-coordinate. The scandium alkyl complex [Sc(Me(3)TACD)(CH(2)SiMe(3))(2)] (4) was obtained by reacting (Me(3)TACD)H with [Sc(CH(2)SiMe(3))(3)(thf)] in benzene-d(6). The scandium amide complexes 2 and 3 catalyzed the ring-opening polymerization (ROP) of meso-lactide to give syndiotactic polylactides.     

Nitride formation by thermolysis of a kinetically stable niobium dinitrogen complex

The reduction of [P(2)N(2)]NbCl (where [P(2)N(2)] = PhP(CH(2)SiMe(2)NSiMe(2)CH(2))(2)PPh) with KC(8) under a dinitrogen atmosphere generates the paramagnetic dinuclear dinitrogen complex ([P(2)N(2)]Nb)(2)(mu-N(2)) (2). Complex 2 has been characterized crystallographically and by EPR spectroscopy. Variable-temperature magnetic susceptibility measurements indicate that 2 displays antiferromagnetic coupling between two Nb(IV) (d(1)) centers. A density functional theory calculation on the model complex [(PH(3))(2)(NH(2))(2)Nb](2)(mu-N(2)) was performed. Thermolysis of ([P(2)N(2)]Nb)(2)(mu-N(2)) in toluene generates the paramagnetic bridging nitride species where one N atom of the dinitrogen ligand inserts into the macrocycle backbone to form [P(2)N(2)]Nb(mu-N)Nb[PN(3)] (3) (where [PN(3)] = PhPMe(CHSiMe(2)NSiMe(2)CH(2)P(Ph)CH(2)SiMe(2)NSiMe(2)N)). Complex 3 has been characterized in the solid state as well as by variable-temperature magnetic susceptibility measurements. The reaction of ([P(2)N(2)]Nb)(2)(mu-N(2)) with phenylacetylene displaces the dinitrogen fragment to generate a paramagnetic eta(2)-alkyne complex, [P(2)N(2)]Nb(eta(2)-HCCPh) (4).     

Catalytic P--H activation by Ti and Zr catalysts

Catalytic dehydrocoupling of phosphines was investigated using the anionic zirconocene trihydride salts [Cp*2Zr(mu-H)3Li]3 (1 a) or [Cp*2Zr(mu-H)3K(thf)4] (1 b), and the metallocycles [CpTi(NPtBu3)(CH2)4] (6) and [Cp*M(NPtBu3)(CH2)4] (M=Ti 20, Zr 21) as catalyst precursors. Dehydrocoupling of primary phosphines RPH2 (R=Ph, C6H2Me3, Cy, C10H7) gave both dehydrocoupled dimers RP(H)P(H)R or cyclic oligophosphines (RP)n (n=4, 5) while reaction of tBu3C6H2PH2 gave the phosphaindoline tBu2(Me2CCH2)C6H2PH 9. Stoichiometric reactions of these catalyst precursors with primary phosphines afforded [Cp*2Zr((PR)2)H][K(thf)4] (R=Ph 2, Cy 3, C6H2Me3 4), [Cp*2Zr((PPh)3)H][K(thf)4] (5), [CpTi(NPtBu3)(PPh)3] (7) and [CpTi(NPtBu3)(mu-PHPh)]2 (8), while reaction of 6 with (C6H2tBu3)PH2 in the presence of PMe3 afforded [CpTi(NPtBu3)(PMe3)(P(C6H2tBu3)] (10). The secondary phosphines Ph2PH and (PhHPCH2)2CH2 also undergo dehydrocoupling affording (Ph2P)2 and (PhPCH2)2CH2. The bisphosphines (CH2PH2)2 and C6H4(PH2)2 are dehydrocoupled to give (PCH2CH2PH)2)(12) and (C6H4P(PH))2 (13) while prolonged reaction of 13 gave (C6H4P2)(8) (14). The analogous bisphosphine Me2C6H4(PH)2 (17) was prepared and dehydrocoupling catalysis afforded (Me2C6H2P(PH))2 (18) and subsequently [(Me2C6H2P2)2(mu-Me2C6H2P2)]2 (19). Stoichiometric reactions with these bisphosphines gave [Cp*2Zr(H)(PH)2C6-H4][Li(thf)4] (22), [CpTi(NPtBu3)(PH)2C6H4]2 (23) and [Cp*Ti(NPtBu3)(PH)2C6H4] (24). Mechanistic implications are discussed.     

The beta-dialdiminato ligand [{N(C6H3Pri(2)-2,6)C(H)}2CPh]-: the conjugate acid and Li, Al, Ga and In derivatives

The synthesis of the following crystalline complexes is described: [Li(L)(thf)2] (), [Li(L)(tmeda)] (), [MCl2(L)] [M=Al (), Ga ()], [In(Cl)(L)(micro-Cl)2Li(OEt2)2] (), [In(Cl)(L){N(H)C6H3Pri(2)-2,6}] (), [In(L){N(H)C6H3Pri(2)-2,6}2] (), [{In(Cl)(L)(micro-OH)}2] (), [L(Cl)In-In(Cl)(L)] () (the thf-solvate, the solvate-free and the hexane-solvate), [{In(Cl)L}2(micro-S)] () and [InCl2(L)(tmeda)] () ([L]-=[{N(C6H3Pri(2)-2,6)C(H)}2CPh]-). From H(L) (), via Li(L) in Et2O, and thf, tmeda, AlCl3, GaCl3 or InCl3 there was obtained , , , or , respectively in excellent yield. Compound was the precursor for each of , and [{InCl3(tmeda)2{micro-(OSnMe2)2}}] () by treatment with one () or two () equivalents of K[N(H)(C6H3Pri(2)-2,6)], successively Li[N(SiMe3)(C6H3Pri(2)-2,6)] and moist air (), Na in thf (), tmeda (), or successively tmeda and Me3SnSnMe3 (). Crystals of (with an equivalent of In) and were obtained from InCl or thermolysis of [In(Cl)(L){N(SiMe3)(C6H3Pri(2)-2,6)}] () {prepared in situ from and Li[N(SiMe3)(C6H3Pri(2)-2,6)] in Et2O}, respectively. Compound was obtained from a thf solution of and sulfur. X-Ray data for crystalline , , , , , and are presented. The M(L) moiety in each (not the L-free ) has the monoanionic L ligated to the metal in the N,N'-chelating mode. The MN1C1C2C3N2 six-membered M(L) ring is pi-delocalised and has the half-chair (, and ) or boat (, and ) conformation.     

Vibrational and electronic structure of the dinuclear bis(mu-nitrido) vanadium(v) complex [V(N{N"}2)(mu-N)]2: spectroscopic properties of the M2(mu-N)2 diamond core

The vibrational and electronic structure of the bis(mu-nitrido) bridged complex [V(N{N"}2)(mu-N)]2 (1) (where [N{N"}2](2-)=[(Me3Si)N{CH(2)CH(2)N(SiMe3)}2](2-)) is analyzed. Assignment of the five modes of the V(2)(mu-N)2 core is based on (15)N isotope shifts and a DFT calculation on the calculated structure I which is an exact reproduction of 1. The three Raman active modes of the planar V(2)(mu-N)2 core are found in the Raman spectrum whereas the two IR allowed vibrations are identified in the infrared spectrum. Furthermore, the electronic structure of is described which complements earlier theoretical studies on the reaction pathway leading to 1(V. M. E. Bates, G. K. B. Clentsmith, F. G. N. Cloke, J. C. Green, H. D. L. Jenkin, Chem. Commun., 2000, 927). Based on the MO scheme of I the UV-vis transitions of 1 are assigned.     

Synthesis and characterisation of two monomeric crystalline thallium(I) beta-diketiminates

Treatment of the appropriate sodium beta-diketiminate NaL or NaL' with an equivalent portion of TlCl in thf under mild conditions furnishes in good yield the first structurally characterised thallium beta-diketiminates: the monomeric, orange, crystalline Tl(I) complexes TlL and TlL' [L = {N(SiMe3)C(Ph)}2CH, L' = {N(C6H3Pr(i)(2)-2,6)C(H)}2CPh].