Synthesis of (O2CEPh)1- ligands (E = S, Se) by CO2 insertion into lanthanide chalcogen bonds and their utility in forming crystallographically characterizable organoaluminum complexes [Me2Al(mu-O2CEPh)]2

CO(2) inserts into the Sm-S and Sm-Se bonds of [(C(5)Me(5))(2)Sm(mu-EPh)](2) (E = S, Se) to form the first crystallographically characterized (O(2)CEPh)(1-) complexes, [(C(5)Me(5))(2)Sm(mu-O(2)CEPh)](2). These complexes are structurally analogous to [(C(5)Me(5))(2)Sm(mu-O(2)CR)](2) complexes, but they are less soluble. This feature was utilized in the reaction of Me(2)AlCl with [(C(5)Me(5))(2)Sm(mu-O(2)CEPh)](2), which forms crystallographically characterizable [Me(2)Al(mu-O(2)CEPh)](2) complexes. Such complexes could not be isolated from an analogous carboxylate reaction. [(C(5)Me(5))(2)Sm(mu-O(2)CSePh)](2) decarboxylates in THF to form (C(5)Me(5))(2)Sm(SePh)(THF). The loss of CO(2) rather than COSe with formation of (C(5)Me(5))(2)Sm(OPh)(THF) was established by (13)CO(2) studies and independent synthesis of (C(5)Me(5))(2)Sm(OPh)(THF) from (C(5)Me(5))(2)Sm[N(SiMe(3))(2)] and PhOH.     

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.     

Well-defined imidotitanium alkyl cations: agostic interactions, migratory insertion vs.[2+2] cycloaddition, and the first structurally authenticated AlMe(3) adduct of any transition metal alkyl cation

The imidotitanium alkyl cations [Ti(NtBu)(Me3[9]aneN3)R]+ (R = Me (3+) or CH2SiMe3(4+)) possess either a very weak alpha-agostic or beta-Si-C agostic interactions, respectively, according to 13C and 29Si NMR and DFT studies; reaction of (4+) with iPrNCNiPr gives totally selective insertion into the Ti-alkyl bond; reaction of 3+ with AlMe3 gives the first structurally characterised AlMe3 adduct of a transition metal alkyl cation (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).     

Four-coordinate, 14-electron Ru(II) complexes: unusual trigonal pyramidal geometry enforced by bis(phosphino)silyl ligation

Unprecedented diamagnetic, four-coordinate, formally 14-electron (Cy-PSiP)RuX (Cy-PSiP = [κ(3)-(2-R(2)PC(6)H(4))(2)SiMe](-); X = amido, alkoxo) complexes that do not require agostic stabilization and that adopt a highly unusual trigonal pyramidal coordination geometry are reported. The tertiary silane [(2-Cy(2)PC(6)H(4))(2)SiMe]H ((Cy-PSiP)H) reacted with 0.5 [(p-cymene)RuCl(2)](2) in the presence of Et(3)N and PCy(3) to afford [(Cy-PSiP)RuCl](2) (1) in 74% yield. Treatment of 1 with KO(t)Bu led to the formation of (Cy-PSiP)RuO(t)Bu (2, 97% yield), which was crystallographically characterized and shown to adopt a trigonal pyramidal coordination geometry in the solid state. Treatment of 1 with NaN(SiMe(3))(2) led to the formation of (Cy-PSiP)RuN(SiMe(3))(2) (3, 70% yield), which was also found to adopt a trigonal pyramidal coordination geometry in the solid state. The related anilido complexes (Cy-PSiP)RuNH(2,6-R(2)C(6)H(3)) (4, R = H; 5, R = Me) were also prepared in >90% yields by treating 1 with LiNH(2,6-R(2)C(6)H(3)) (R = H, Me) reagents. The solid state structure of 5 indicates a monomeric trigonal pyramidal complex that features a C-H agostic interaction. Complexes 2 and 3 were found to react readily with 1 equiv of H(2)O to form the dimeric hydroxo-bridged complex [(Cy-PSiP)RuOH](2) (6, 94% yield), which was crystallographically characterized. Complexes 2 and 3 also reacted with 1 equiv of PhOH to form the new 18-electron η(5)-oxocyclohexadienyl complex (Cy-PSiP)Ru(η(5)-C(6)H(5)O) (7, 84% yield). Both amido and alkoxo (Cy-PSiP)RuX complexes reacted with H(3)B·NHRR' reagents to form bis(σ-B-H) complexes of the type (Cy-PSiP)RuH(η(2):η(2)-H(2)BNRR') (8, R = R' = H; 9, R = R' = Me; 10, R = H, R' = (t)Bu), which illustrates that such four-coordinate (Cy-PSiP)RuX (X = amido, alkoxo) complexes are able to undergo multiple E-H (E = main group element) bond activation steps. Computational methods were used to investigate structurally related PCP, PPP, PNP, and PSiP four-coordinate Ru complexes and confirmed the key role of the strongly σ-donating silyl group of the PSiP ligand set in enforcing the unusual trigonal pyramidal coordination geometry featured in complexes 2-5, thus substantiating a new strategy for the synthesis of low-coordinate Ru species. The mechanism of the activation of ammonia-borane by such low-coordinate (R-PSiP)RuX (X = amido, alkoxo) species was also studied computationally and was determined to proceed most likely in a stepwise fashion via intramolecular deprotonation of ammonia and subsequent borane B-H bond oxidative addition steps.     

Molecular spectroscopy of uranium(IV) bis(ketimido) complexes. rare observation of resonance-enhanced raman scattering from organoactinide complexes and evidence for broken-symmetry excited states

Electronic absorption and resonance-enhanced Raman spectra for ketimido (azavinylidene) complexes of tetravalent uranium, (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) (R = Ph, Me, and CH(2)Ph), have been recorded. The absorption spectra exhibit four broad bands between 13 000 and 24 000 cm(-1). The highest-energy band is assigned to the ketimido-localized p( perpendicular)(N)-->pi(N=C) transition based on comparison to the spectra of (C(5)H(5))(2)Zr[-N=CPh(2)](2) and (C(5)Me(5))(2)Th[-N=CPh(2)](2). Upon excitation into any of these four absorption bands, the (C(5)Me(5))(2)U[-N=C(Ph)(R)](2) complexes exhibit resonance enhancement for several Raman bands attributable to vibrations of the ketimido ligands. Raman bands for both the symmetric and nominally asymmetric N=C stretching bands are resonantly enhanced upon excitation into the p( perpendicular)(N)-->pi(N=C) absorption bands, indicating that the excited state is localized on a single ketimido ligand. Raman excitation profiles for (C(5)Me(5))(2)U[-N=CPh(2)](2) confirm that at least one of the lower-energy electronic absorption bands (E(max) approximately 16300 cm(-1)) is a charge-transfer transition between the U(IV) center and the ketimido ligand(s). The observations of both charge-transfer transitions and resonance enhancement of Raman vibrational bands are exceedingly rare for tetravalent actinide complexes and reflect the strong bonding interactions between the uranium 5f/6d orbitals and those on the ketimido ligands.     

Synthesis, structure, and ligand-based reduction reactivity of trivalent organosamarium benzene chalcogenolate complexes (C(5)Me(5))(2)Sm(EPh)(THF) and [(C(5)Me(5))(2)Sm(mu-EPh)](2)

To compare the ligand-based reduction chemistry of (EPh)(-) ligands in a metallocene environment to the sterically induced reduction chemistry of the (C(5)Me(5))(-) ligands in (C(5)Me(5))(3)Sm, (C(5)Me(5))(2)Sm(EPh) (E = S, Se, Te) complexes were synthesized and treated with substrates reduced by (C(5)Me(5))(3)Sm: cyclooctatetraene; azobenzene; phenazine. Reactions of PhEEPh with (C(5)Me(5))(2)Sm(THF)(2) and (C(5)Me(5))(2)Sm produced THF-solvated monometallic complexes, (C(5)Me(5))(2)Sm(EPh)(THF), and their unsolvated dimeric analogues, [(C(5)Me(5))(2)Sm(mu-EPh)](2), respectively. Both sets of the paramagnetic benzene chalcogenolate complexes were definitively identified by X-crystallography and form homologous series. Only the (TePh)(-) complexes show reduction reactivity and only upon heating to 65 degrees C.     

U(SMes*)n, (n = 3, 4) and Ln(SMes*)3 (Ln = La, Ce, Pr, Nd): lanthanide(III)/actinide(III) differentiation in agostic interactions and an unprecedented eta3 ligation mode of the arylthiolate ligand, from X-ray diffraction and DFT analysis

Reaction of U(NEt(2))(4) with HS-2,4,6-(t)Bu(3)C(6)H(2) (HSMes) gave U(SMes)(3)(NEt(2))(py) (1), whereas similar treatment of U[N(SiMe(3))SiMe(2)CH(2)][N(SiMe(3))(2)](2) afforded U(SMes)[N(SiMe(3))(2)](3) (2) and U(SMes)(3)[N(SiMe(3))(2)]. The first neutral homoleptic uranium(IV) thiolate to have been crystallographically characterized, U(SMes)(4) (4), was isolated from the reaction of U(BH(4))(4) and KSMes. The first homoleptic thiolate complex of uranium(III), U(SMes)(3) (5), was synthesized by protonolysis of U[N(SiMe(3))(2)](3) with HSMes in cyclohexane. The crystal structure of 5 exhibits the novel eta(3) ligation mode for the arylthiolate ligand. Comparison of the crystal structure of 5 with those of the isomorphous lanthanide congeners Ln(SMes)(3) (Ln = La, Ce, Pr, and Nd) indicates that the U-S, U-C(ipso)(), and U-C(ortho)() bond lengths are shorter than the corresponding ones in the 4f-element analogues, when taking into account the variation in the ionic radii of the metals. The distance between the uranium and the carbon atoms involved in the U...H-C epsilon agostic interaction of each thiolate ligand is shorter, by approximately 0.05 A, than that expected from a purely ionic bonding model. The lanthanide(III)/actinide(III) differentiation was analyzed by density functional theory (DFT). The nature of the M-S bond is shown to be ionic strongly polarized at the sulfur for M = U and iono-covalent (i.e. strongly ionic with low orbital interaction), for M = Ln. The strength of the U...H-C epsilon agostic interaction is proposed to be controlled by the maximization of the interaction between U(+) and S(-) under steric constraints. The eta(3) ligation mode of the arylthiolate ligand is also obtained from DFT.     

Synthesis and luminescence studies of mono- and C3-symmetric, tris(ligand) complexes of Sm(III), Y(III) and Eu(III) with sulfur-bridged binaphtholate ligands

A series of trivalent mono- and tris(ligand) lanthanide complexes of a sulfur-bridged binaphthol ligand [1,1'-S(2-HOC(10)H(4)Bu(t)(2)-3,6)(2)] H(2)L(SN), have been prepared and characterised both structurally and photophysically. The H(2)L(SN) ligand provides an increased steric bulk and offers an additional donor atom (sulfur) as compared with 1,1'-binaphthol (BINOL), a ligand commonly used to complex Lewis acidic lanthanide catalysts. Reaction of the diol H(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] affords silylamido- and amino- derivatives [Sm(L(SN))[N(SiMe(3))(2)][HN(SiMe(3))(2)]] and the crystallographically characterised [Sm(L(SN))[N(SiMe(3))(2)](thf)(2)] with different degrees of structural rigidity, depending on the presence of coordinating solvents. The binaphthyl groups of the L(SN) ligand act as sensitisers of the metal centred emission, which is observed for the Eu(III) and Sm(III) complexes studied. We have therefore sought to use emission spectroscopy as a non-invasive technique to monitor a monomer-dimer equilibrium in these complexes. A dramatic difference between the emission properties of the unreactive dimeric Sm(III) aryloxide complex, the solvated monomeric analogues and the amido adduct demonstrated the potential use of such a technique. For a few representative lanthanides (Ln = Sm, Eu and Y) the reaction of the dilithium salt Li(2)L(SN) with either [Ln[N(SiMe(3))(2]3)] or [LnCl(3)(thf)(3)] affords only the homoleptic complex [Li(S)(3)][LnL(SN)(3)](S = thf or diethyl ether); we report the structural characterisation of the Sm complex. However, the reactions of this dipotassium salt K(2)L(SN) with [Sm[N(SiMe(3))(2)](3)] or [SmCl(3)(thf)(3)] give only [SmL(SN)N(SiMe(3))(2)], or intractable mixtures respectively, in which no (tris)binaphtholate is observed. The only isolable lanthanide-L(SN) halide adduct so far is [YbL(SN)I(thf)].     

Reactions of tetrakis(dimethylamide)-titanium, -zirconium and -hafnium with silanes: synthesis of unusual amide hydride complexes and mechanistic studies of titanium-silicon-nitride (Ti-Si-N) formation

M(NMe(2))(4) (M = Ti, Zr, Hf) were found to react with H(2)SiR'Ph (R' = H, Me, Ph) to yield H(2), aminosilanes, and black solids. Unusual amide hydride complexes [(Me(2)N)(3)M(mu-H)(mu-NMe(2))(2)](2)M (M = Zr, 1; Hf, 2) were observed to be intermediates and characterized by single-crystal X-ray diffraction. [(Me(2)N)(3)M(mu-D)(mu-NMe(2))(2)](2)M (1-d(2), 2-d(2)) were prepared through reactions of M(NMe(2))(4) with D(2)SiPh(2). Reactions of (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) with H(2)SiR'Ph were found to give aminosilanes and (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6). These reactions are reversible through unusual equilibria such as (Me(2)N)(3)ZrSi(SiMe(3))(3) (5) + H(2)SiPh(2) right arrow over left arrow (Me(2)N)(2)Zr(H)Si(SiMe(3))(3) (6) + HSi(NMe(2))Ph(2). The deuteride ligand in (Me(2)N)(2)Zr(D)Si(SiMe(3))(3) (6-d(1)) undergoes H-D exchange with H(2)SiR'Ph (R' = Me, H) to give 6 and HDSiR'Ph. The reaction of Ti(NMe(2))(4) with SiH(4) in chemical vapor deposition at 450 degrees C yielded thin Ti-Si-N ternary films containing TiN and Si(3)N(4). Ti(NMe(2))(4) reacts with SiH(4) at 23 degrees C to give H(2), HSi(NMe(2))(3), and a black solid. HNMe(2) was not detected in this reaction. The reaction mixture, upon heating, gave TiN and Si(3)N(4) powders. Analyses and reactivities of the black solid revealed that it contained -H and unreacted -NMe(2) ligands but no silicon-containing ligand. Ab initio quantum chemical calculations of the reactions of Ti(NR(2))(4) (R = Me, H) with SiH(4) indicated that the formation of aminosilanes and HTi(NR(2))(3) was favored. These calculations also showed that HTi(NH(2))(3) (3b) reacted with SiH(4) or H(3)Si-NH(2) in the following step to give H(2)Ti(NH(2))(2) (4b) and aminosilanes. The results in the current studies indicated that the role of SiH(4) in its reaction with Ti(NMe(2))(4) was mainly to remove amide ligands as HSi(NMe(2))(3). The removal of amide ligands is incomplete, and the reaction thus yielded "=Ti(H)(NMe(2))" as the black solid. Subsequent heating of the black solid and HSi(NMe(2))(3) may then yield TiN and Si(3)N(4), respectively, as the Ti-Si-N materials.     

Electronic Structure of [Ta(5)(NH)(4)Cl(17)](6-): A Cluster with a Distorted Square Pyramidal Ta(5) Core

We report approximate molecular orbital calculations on the [Ta(5)(NH)(4)Cl(17)](6-) cluster synthesized by Simon and Meyer. The cluster is based on a "flattened" square pyramid of tantalum atoms, basal bridging imides, and terminal chlorides. This cluster was of interest to us due to the unusual presence of imide ligands, the distorted nature of the metal core, and the possible resemblance to B(5)H(9). Our calculations indicate that metal-metal bonding is limited to Ta(apical)-Ta(basal) bonding, with no significant bonding between the basal metal atoms. The imide ligands, which bridge the base of the pyramid, were found to have a significant amount of capping character. The metal-metal bonding orbitals have some unusual features due to the pyramid's distortion. Additionally, the flattened nature of the pyramid leads to an interesting energy ordering of the metal-metal bonding orbitals.     

Reactivity of [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (tim(Me) = 2-mercapto-1-methylimidazolyl) toward neutral substrates

The complex [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (2a) (tim(Me) = 2-mercapto-1-methylimidazolyl) reacts with a variety of neutral substrates to afford new complexes featuring the dihydrobis(2-mercapto-1-methylimidazolyl)borate coordinated in a bidentate or unidentate fashion. By treating 2a with unidentate ligands, the mononuclear complexes [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)(L)] (L = imidazole (5), 4-(dimethylamino)pyridine (6), tert-butylisonitrile (7), triphenylphosphine (8)) were formed, upon replacement of the agostic B-H...Re bond by the correspondent unidentate ligand. With potentially bidentate substrates, 2a is transformed into mononuclear or dinuclear complexes, depending on the atom donor set of the reacting substrates. Reaction of compound 2a with ethylenediamine (en) gave the complex [Re[kappa(1)-H(2)B(tim(Me))(2)](CO)(3)(en)] (9), because of cleavage of the agostic interaction, dechelation of one mercaptoimidazolyl ring, and bidentate coordination of the amine. By contrast, 1,2-bis(diphenyl)phosphinoethane (dppe) is not able to replace the mercaptoimidazolyl ring, and the dimer [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)](2)(mu-dppe) (10) was formed. The novel Re(I) tricarbonyl complexes (5-10) have been fully characterized, including by X-ray diffraction analysis in the case of 6, 8, 9, and 10. The X-ray diffraction study confirmed the unprecedented unidentate coordination mode of the dihydrobis(2-mercapto-1-methylimidazolyl)borate in complex 9.     

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.     

Synthetic and structural studies of donor-functionalized alkoxy derivatives of gallium

The synthesis of a range of alkyl/chloro-gallium alkoxide and amido/alkoxide compounds was achieved via a series of protonolysis and alcoholysis steps. The initial reaction involved the synthesis of [Me(Cl)Ga{N(SiMe(3))(2)}](2) (1) via methyl group transfer from the reaction of GaCl(3) with two equivalents of LiN(SiMe(3))(2). Reaction of 1 with varying amounts of ROH resulted in the formation of [Me(Cl)Ga(OR)](2) (2, R = CH(2)CH(2)OMe; 3, CH(CH(3))CH(2)NMe(2)), [Me(Cl)Ga{N(SiMe(3))(2)}(μ(2)-OR)Ga(Cl)Me] (4, R = CH(2)CH(2)NMe(2)), or [MeGa(OR)(2)] (5, R = CH(CH(3))CH(2)NMe(2)). Compound 4 represents an intermediate in the formation of dimeric complexes, of the type [Me(Cl)Ga(OR)](2), when formed from compound [Me(Cl)Ga{N(SiMe(3))(2)}](2). A methylgallium amido/alkoxide complex [MeGa{N(SiMe(3))(2)}(OCH(2)CH(2)OMe)](2) (6) was isolated when 2 was further reacted with LiN(SiMe(3))(2). In addition, reaction of 2 with HO(t)Bu resulted in a simple alcohol/alkoxide exchange and formation of [Me(Cl)Ga(O(t)Bu)](2) (7). In contrast to the formation of 1, the in situ reaction of GaCl(3) with one equivalent of LiN(SiMe(3))(2) yielded [Cl(2)Ga{N(SiMe(3))(2)}](2) in low yield, where no methyl group transfer has occurred. Reaction of alcohol with [Cl(2)Ga{N(SiMe(3))(2)}](2) was then found to yield [Cl(2)Ga(OR)](2) (8, R = CH(2)CH(2)NMe(2)), and further reaction of 8 with LiN(SiMe(3))(2) yielded the gallium amido alkoxide complex, [ClGa{N(SiMe(3))(2)}(OR)](2) (9, R = CH(2)CH(2)NMe(2)), similar to 6. The structures of compounds 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction.     

Expanding dinitrogen reduction chemistry to trivalent lanthanides via the LnZ3/alkali metal reduction system: evaluation of the generality of forming Ln2(mu-eta2:eta2-N2) complexes via LnZ3/K

The Ln[N(SiMe(3))(2)](3)/K dinitrogen reduction system, which mimicks the reactions of the highly reducing divalent ions Tm(II), Dy(II), and Nd(II), has been explored with the entire lanthanide series and uranium to examine its generality and to correlate the observed reactivity with accessibility of divalent oxidation states. The Ln[N(SiMe(3))(2)](3)/K reduction of dinitrogen provides access from readily available starting materials to the formerly rare class of M(2)(mu-eta(2):eta(2)-N(2)) complexes, [[(Me(3)Si)(2)N](2)(THF)Ln](2)(mu-eta(2):eta(2)-N(2)), 1, that had previously been made only from TmI(2), DyI(2), and NdI(2) in the presence of KN(SiMe(3))(2). This LnZ(3)/alkali metal reduction system provides crystallographically characterizable examples of 1 for Nd, Gd, Tb, Dy, Ho, Er, Y, Tm, and Lu. Sodium can be used as the alkali metal as well as potassium. These compounds have NN distances in the 1.258(3) to 1.318(5) A range consistent with formation of an (N=N)(2)(-) moiety. Isolation of 1 with this selection of metals demonstrates that the Ln[N(SiMe(3))(2)](3)/alkali metal reaction can mimic divalent lanthanide reduction chemistry with metals that have calculated Ln(III)/Ln(II) reduction potentials ranging from -2.3 to -3.9 V vs NHE. In the case of Ln = Sm, which has an analogous Ln(III)/Ln(II) potential of -1.55 V, reduction to the stable divalent tris(amide) complex, K[Sm[N(SiMe(3))(2)](3)], is observed instead of dinitrogen reduction. When the metal is La, Ce, Pr, or U, the first crystallographically characterized examples of the tetrakis[bis(trimethylsilyl)amide] anions, [M[N(SiMe(3))(2)](4)](-), are isolated as THF-solvated potassium or sodium salts. The implications of the LnZ(3)/alkali metal reduction chemistry on the mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.     

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.     

Synthesis with structural and electronic characterization of homoleptic Fe(II)- and Fe(III)-fluorinated phenolate complexes

Four Fe(III) compounds and one Fe(II) compound containing mononuclear, homoleptic, fluorinated phenolate anions of the form [Fe(OAr)(m)](n-) have been prepared in which Ar(F) = C(6)F(5) and Ar' = 3,5-C(6)(CF(3))(2)H(3): (Ph(4)P)(2)[Fe(OAr(F))(5)], 1, (Me(4)N)(2)[Fe(OAr(F))(5)], 2, {K(18-crown-6)}(2)[Fe(OAr(F))(5)], 3a, {K(18-crown-6)}(2)[Fe(OAr')(5)], 3b, and {K(18-crown-6)}(2)[Fe(OAr(F))(4)], 6. Two dinuclear Fe(III) compounds have also been prepared: {K(18-crown-6)}(2)[(OAr(F))(3)Fe(μ(2)-O)Fe(OAr(F))(3)], 4, and {K(18-crown-6)}(2)[(OAr(F))(3)Fe(μ(2)-OAr(F))(2)Fe(OAr(F))(3)], 5. These compounds have been characterized with UV-vis spectroscopy, elemental analysis, Evans method susceptibility, and X-ray crystallography. All-electron, geometry-optimized DFT calculations on four [Ti(IV)(OAr)(4)] and four [Fe(III)(OAr)(4)](-) species (Ar = 2,3,5,6-C(6)Me(4)H, C(6)H(5), 2,4,6-C(6)Cl(3)H(2), C(6)F(5)) with GGA-BP and hybrid B3LYP basis sets demonstrated that, under D(2d) symmetry, π donation from the O 2p orbitals is primarily into the d(xy) and d(z(2)) orbitals. The degree of donation is qualitatively consistent with expectations based on ligand Br?nsted basicity and supports the contention that fluorinated phenolate ligands facilitate isolation of nonbridged homoleptic complexes due to their reduced π basicity at oxygen.     

Lanthanide amido complexes incorporating amino-coordinate-lithium bridged bis(indolyl) ligands: synthesis, characterization, and catalysis for hydrophosphonylation of aldehydes and aldimines

Two series of new lanthanide amido complexes supported by bis(indolyl) ligands with amino-coordinate-lithium as a bridge were synthesized and characterized. The interactions of [(Me(3)Si)(2)N](3)Ln(III)(μ-Cl)Li(THF)(3) with 2 equiv of 3-(CyNHCH(2))C(8)H(5)NH in toluene produced the amino-coordinate-lithium bridged bis(indolyl) lanthanide amides [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm (1), Eu (2), Dy (3), Yb (4)) in good yields. Treatment of [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] with THF gave new lanthanide amido complexes [μ-{[η(1):η(1)-3-(CyNHCH(2))Ind](2)Li(THF)}Ln[N(SiMe(3))(2)](2)] (Ln = Eu (5), Dy (6), Yb (7)), which can be transferred to amido complexes 2, 3, and 4 by reflux the corresponding complexes in toluene. Thus, two series of rare-earth-metal amides could be reciprocally transformed easily by merely changing the solvent in the reactions. All new complexes 1-7 are fully characterized including X-ray structural determination. The catalytic activities of these new lanthanide amido complexes for hydrophosphonylation of both aromatic and aliphatic aldehydes and various substituted aldimines were explored. The results indicated that these complexes displayed a high catalytic activity for the C-P bond formation with employment of low catalyst loadings (0.1 mol?% for aldehydes and 1 mol?% for aldimines) under mild conditions. Thus, it provides a convenient way to prepare both α-hydroxy and α-amino phosphonates.     

Macrocyclic copper(II) and zinc(II) complexes incorporating phosphate esters

Slow evaporation of solutions prepared by adding either Cu(ClO(4))(2).6H(2)O or Zn(ClO(4))(2).6H(2)O to solutions containing appropriate proportions of Me(3)tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) and sodium phenyl phosphate (Na(2)PhOPO(3)) gave dark blue crystals of [Cu(3)(Me(3)tacn)(3)(PhOPO(3))(2)](ClO(4))(2).(1)/(2)H(2)O (1) and colorless crystals of [Zn(2)(Me(3)tacn)(2)(H(2)O)(4)(PhOPO(3))](ClO(4))(2).H(2)O (2), respectively. Blue crystals of [Cu(tacn)(2)](BNPP)(2) (3) formed in an aqueous solution of [Cu(tacn)Cl(2)], bis(p-nitrophenyl phosphate) (BNPP), and HEPES buffer (pH 7.4). Compound 1 crystallizes in the triclinic space group P1 (No. 2) with a = 9.8053(2) A, b = 12.9068(2) A, c = 22.1132(2) A, alpha = 98.636(1) degrees, beta = 99.546(1) degrees, gamma = 101.1733(8) degrees, and Z = 2 and exhibits trinuclear Cu(II) clusters in which square pyramidal metal centers are capped by two phosphate esters located above and below the plane of the metal centers. The trinuclear cluster is asymmetric having Cu...Cu distances of 4.14, 4.55, and 5.04 A. Compound 2 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 13.6248(2) A, b = 11.6002(2) A, c = 25.9681(4) A, beta = 102.0072(9) degrees, and Z = 4 and contains a dinuclear Zn(II) complex formed by linking two units of [Zn(Me(3)tacn)(OH(2))(2)](2+) by a single phosphate ester. Compound 3 crystallizes in the monoclinic space group C2/c (No. 15) with a = 24.7105(5) A, b = 12.8627(3) A, c = 14.0079(3) A, beta = 106.600(1) degrees, and Z = 4 and consists of mononuclear [Cu(tacn)(2)](2+) cations whose charge is balanced by the BNPP(-) anions.     

Synthesis and reactivity of a conveniently prepared two-coordinate bis(amido) nickel(II) complex

A strictly two-coordinate nickel(II) bis(amido) complex has been prepared and its reactivity towards a variety of small molecules is described. Ni[N(SiMe(3))(DIPP)](2) reacts with DMAP and acetonitrile to form T-shaped three-coordinate complexes, and preliminary results show that Ni[N(SiMe(3))(DIPP)](2) is a catalyst for the hydrosilation of olefins with secondary silanes at ambient temperature.     

Cube-type nitrido complexes containing titanium and alkali/alkaline-earth metals

Treatment of [[Ti(eta(5)-C(5)Me(5))(mu-NH)](3)(mu(3)-N)] with alkali-metal bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)]] in toluene affords edge-linked double-cube nitrido complexes [M(mu(4)-N)(mu(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]](2) (M = Li, Na, K, Rb, Cs) or corner-shared double-cube nitrido complexes [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Na, K, Rb, Cs). Analogous reactions with 1/2 equiv of alkaline-earth bis(trimethylsilyl)amido derivatives [M[N(SiMe(3))(2)](2)(thf)(2)] give corner-shared double-cube nitrido complexes [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = Mg, Ca, Sr, Ba). If 1 equiv of the group 2 amido reagent is employed, single-cube-type derivatives [(thf)(x)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Mg, x = 0; M = Ca, Sr, Ba, x = 1) can be isolated or identified. The tetrahydrofuran molecules are easily displaced with 4-tert-butylpyridine in toluene, affording the analogous complexes [(tBupy)[(Me(3)Si)(2)N]M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)]] (M = Ca, Sr). The X-ray crystal structures of [M(mu(3)-N)(mu(3)-NH)(5)[Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)](2)] (M = K, Rb, Cs) and [M[(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3))-N)](2)] (M = Ca, Sr) have been determined. The properties and solid-state structures of the azaheterometallocubane complexes bearing alkali and alkaline-earth metals are discussed.