Design of new heteroscorpionate ligands and their coordinative ability toward Group 4 transition metals; an efficient synthetic route to obtain enantiopure ligands

The reaction of different types of bis(pyrazol-1-yl)methane derivatives with Bu(n)Li and alkyl or aryl-containing-isocyanates or isothiocyanates, some of these as chiral reagents, gives rise to the preparation of new heteroscorpionate ligands in the form of the lithium derivatives [Li(NNE)]2 (1-10), although a similar process with trimethylsilyl isocyanate or isothiocyanate gave the complexes [Li(NCX)(bdmpzs)(THF)](X = O, 11; X = S, 12)[bdmpzs = bis(3,5-dimethylpyrazol-1-yl)trimethylsilylmethane]. Compounds 1-8 reacted with [TiCl4(THF)2] or [MCl4](M = Zr, Hf) to give a series of cationic complexes [MCl3{kappa3-NNE(H)}]Cl (13-36) where the heteroscorpionate ligand contains either an acetamide or thioacetamide group resulting from the protonation of the corresponding acetamidate or thioacetamidate. However, under appropriate experimental conditions neutral Ti complexes were isolated-namely [TiClx(NMe2)3-x(S-mbbpam)](37-39)[S-mbbpam =(S)-(-)-N-alpha-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate]. Finally, two alkoxide-containing titanium complexes [TiClx(OR)3-x(S-mbbpamH)]Cl (40-41) were also prepared. The structures of these complexes have been determined by spectroscopic methods and, in addition, the X-ray crystal structures of 1, 12, and 19 were also established.     

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.     

New complexes of zirconium(IV) and hafnium(IV) with heteroscorpionate ligands and the hydrolysis of such complexes to give a zirconium cluster

A series of zirconium and hafnium heteroscorpionate complexes have been prepared by the reaction of MCl4 (M = Zr, Hf) with the compounds [[Li(bdmpza)(H2O)](4)] [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], [[Li(bdmpzdta)(H2O)](4)] [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], and (Hbdmpze) [bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] (the latter with the prior addition of Bu(n)Li). Under the appropriate experimental conditions, mononuclear complexes, namely, [MCl3(kappa3-bdmpzx)] [x = a, M = Zr (1), Hf (2); x = dta, M = Zr (3), Hf (4); x = e, M = Zr (5), Hf (6)], and dinuclear complexes, namely, [[MCl2(mu-OH)(kappa3-bdmpzx)]2] [x = a, M = Zr (7), Hf (8); x = dta, M = Zr (9); x = e, M = Zr (10)], were isolated. A family of alkoxide-containing complexes of the general formula [ZrCl2(kappa3-bdmpzx)(OR)] [x = a, R = Me (11), Et (12), iPr (13), tBu (14); x = dta, R = Me (15), Et (16), iPr (17), tBu (18); x = e, R = Me (19), Et (20), (i)Pr (21), (t)Bu (22)] was also prepared. Complexes 11-14 underwent an interesting hydrolysis process to give the cluster complex [Zr6(mu3-OH)8(OH)8(kappa2-bdmpza)8] (23). The structures of these complexes have been determined by spectroscopic methods, and the X-ray crystal structures of 7, 8, and 23 were also established.     

Lithium, titanium, and zirconium complexes with novel amidinate scorpionate ligands

The reaction of bis(3,5-dimethylpyrazol-1-yl)methane (bdmpzm) with BunLi and carbodiimide derivatives, namely, N,N'-diisopropyl, dicyclohexyl, and 1-tert-butyl-3-ethyl carbodiimides, enables the preparation of new heteroscorpionate ligands in the form of the lithium derivatives [Li(NNN)(THF)] (NNN = pbpamd (1) (pbpamd = N,N'-diisopropylbis(3,5-dimethylpyrazol-1-yl)acetamidinate); cbpamd (2) (cbpamd = N,N'-dicyclohexylbis(3,5-dimethylpyrazol-1-yl)acetamidinate); and tbpamd (3) (tbpamd = N-ethyl-N'-tert-butylbis(3,5-dimethylpyrazol-1-yl)acetamidinate)), although a similar process with N,N'-dimethylcarbodiimide gave the dinuclear complex [Li(bpzii)(THF)]2 (4) (bpzii = N-(dimethylamino)-N'-[(dimethylamino)bis(3,5-dimethylpyrazol-1-yl)methylimino]imino). When this last reaction was carried out in an air atmosphere, the cluster complex [Li8(mu4-O)2(mu4-OH)2(mu4-pz)2(kappa2-bpziLi)2(bpzCN)2(THF)4] (5) (bpziLi = dimethylaminobis(3,5-dimethylpyrazol-1-yl)methyliminolithium, bpzCN = bis(3,5-dimethylpyrazol-1-yl)acetonitrile) was isolated and characterized by X-ray analysis. Finally, when the same process was carried out in the presence of water the amidine-scorpionate (bpzan) (6) (bpzan = N,N-dimethylbis(3,5-dimethylpyrazol-1-yl)acetamidine) was obtained. Compounds 1 and 3 reacted with [TiCl4(THF)2] or [ZrCl4] to give complexes of stoichiometry [MCl3((kappa3-NNN))] (M = Ti, Zr) (7-10). The structures of the different compounds were determined by spectroscopic methods and, in addition, the X-ray crystal structures of 1, 3, 4, 5, and 6 were also established.     

High-temperature single-site ethylene polymerization behavior of titanate complexes supported by 1,3-bis(3,5-dialkylpyrazol-1-yl)propan-2-olate ligation

Titanate(1-) complexes Na[(THF)(kappa1-O-bdbpzp)TiCl4] (1) and Na[(THF)(kappa1-O-bdmpzp)TiCl4] (2) and titanate(2-) complexes [Na(THF)]2[(kappa1-O-bdbpzp)2TiCl4] (4) and [Na(THF)]2[(kappa1-O-bdmpzp)2TiCl4] (5) were obtained in good yield from reaction of Na[bdbpzp] or Na[bdmpzp] (sodium salt of 1,3-bis(3,5-di-tert-butylpyrazol-1yl)propan-2-ol or 1,3-bis(3,5-dimethylpyrazol-1yl)propan-2-ol) with TiCl4 (in the appropriate molar ratio) at 0-25 degrees C. Protonolysis of TiCl4 with 1 equiv of bdmpzpH furnished related zwitterionic titanate(1-) complex 3 that possessed a kappa2-N,O-coordinated pyrazolyl-alkoxide with pendant pyrazolium group. Methylalumoxane (MAO) activation of 1-5 under high-temperature solution polymerization conditions produced active single-site ethylene polymerization catalysts that exhibit considerably higher thermal stability (especially 2/MAO, 3/MAO, and 5/MAO) than previously reported for Cp2TiCl2/MAO or Ti catalysts supported by related heteroscorpionate or scorpionate ligation.     

Direct synthesis of NNN-donor enantiopure scorpionate ligands by an efficient diastereoselective nucleophilic addition to imines

New enantiopure imines (1-9) with a chiral substrate to control the stereochemistry of a newly created stereogenic center have been synthesized by reaction of the commercially available (1R)-(-)-myrtenal and different primary amines. The diastereomerically enriched lithium-scorpionate compounds [Li(κ(3)-mobpza)(THF)] (10) (mobpza = N-p-methylphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-mobpza)(THF)] (11) (mobpza = N-p-methoxyphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-fbpza)(THF)] (12) (fbpza = N-p-fluorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), and [Li(κ(3)-clbpza)(THF)] (13) (clbpza = N-p-chlorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide) were obtained by a diastereoselective 1,2-addition of an organolithium reagent to imines in good yield and with good diastereomeric excess (ca. 80%). The complexes [LiCl(κ(2)-R,R-fbpzaH)(THF)] (14) and [LiCl(κ(2)-R,R-clbpzaH)(THF)] (15) were obtained in enantiomerically pure form by the treatment of THF solutions of 12 or 13 with NH(4)Cl. The enantiomerically pure amines (R,R-mbpzaH) (16), (R,R-mobpzaH) (17), (R,R-fbpzaH) (18), and (R,R-clbpzaH) (19) were obtained by hydrolysis of the lithium-scorpionate compounds 10-13 with H(2)O. The lithium compound 12 was reacted with [TiCl(4)(THF)(2)] or [ZrCl(4)] to give the enantiopure complexes [MCl(3)(κ(3)-R,R-fbpza)] [M = Ti (20), Zr (21)]. The amine compound 18 reacted with [MX(4)] (M = Ti, X = O(i)Pr, OEt; M = Zr; X = NMe(2)) to give the complexes [MX(3)(κ(3)-R,R-fbpza)] (22-24). The reaction of Me(3)SiCl with [Zr(NMe(2))(3)(κ(3)-R,R-fbpza)] (24) in different molar ratios led to the halide-amide-containing complexes [ZrCl(NMe(2))(2)(κ(3)-R,R-fbpza)] (25) and [ZrCl(2)(NMe(2))(κ(3)-R,R-fbpza)] (26) and the halide complex 21. The isolation of only one of the three possible diastereoisomers of complexes 25 and 26 revealed that chiral induction from the ligand to the zirconium center took place. The structures of these compounds were elucidated by (1)H and (13)C{(1)H} NMR spectroscopy, and the X-ray crystal structures of 5, 12, 14, 15, and 24 were also established.     

Titanium and niobium imido complexes stabilized by heteroscorpionate ligands

The reaction of [Ti(NR)Cl(2)(py)(3)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) with [{Li(bdmpza)(H(2)O)}(4)][bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] and [{Li(bdmpzdta)(H(2)O)}(4)][bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate] affords the corresponding complexes [Ti(NR)Cl(kappa(3)-bdmpzx)(py)](x = a, R = (t)Bu 1, p-tolyl 2, 2,6-C(6)H(3)(i)Pr(2) 3; x = dta, R =(t)Bu 4, p-tolyl , 2,6-C(6)H(3)(i)Pr(2) 6), which are the first examples of imido Group 4 complexes stabilized by heteroscorpionate ligands. The solid-state X-ray crystal structure of 1 has been determined. The titanium centre is six-coordinate with three fac-sites occupied by the heteroscorpionate ligand and the remainder of the coordination sphere being completed by chloride, imido and pyridine ligands. The complexes are 1-6 fluxional at room temperature. The pyridine ortho- and meta-proton resonances show evidence of dynamic behaviour for this ligand and variable-temperature NMR studies were carried out in order to study their dynamic behaviour in solution. The complexes [Nb(NR)Cl(3)(py)(2)](R = (t)Bu, p-tolyl, 2,6-C(6)H(3)(i)Pr(2)) reacted with [{Li(bdmpza)(H(2)O)}(4)] and (Hbdmpze)[bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide], the latter with prior addition of (n)BuLi, to give the complexes [Nb(NR)Cl(2)(kappa(3)-bdmpzx)](x = a, R =(t)Bu 7, p-tolyl 8, 2,6-C(6)H(3)(i)Pr(2) 9; x = e, R = (t)Bu 10, p-tolyl 11, 2,6-C(6)H(3)(i)Pr(2)) 12 and these are the first examples of imido Group 5 complexes with heteroscorpionate ligands. The structures of these complexes have been determined by spectroscopic methods.     

Preparation of new monoanionic "scorpionate" ligands: synthesis and structural characterization of titanium(IV) complexes bearing this class of ligand

The preparation of new "scorpionate" ligands in the form of the lithium derivatives [(Li(bdmpzdta)(H(2)O))(4)] (1) [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], [Li(bdphpza)(H(2)O)(THF)] (2) [bdphpza = bis(3,5-diphenylpyrazol-1-yl)acetate], and [Li(bdphpzdta)(H(2)O)(THF)] (3) [bdphpzdta = bis(3,5-diphenylpyrazol-1-yl)dithioacetate] has been carried out. Furthermore, a series of titanium complexes has been prepared by reaction of TiCl(4)(THF)(2) with the lithium reagents [(Li(bdmpza)(H(2)O))(4)] (4) [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] and 1. Under the appropriate experimental conditions neutral complexes, namely [TiCl(3)(kappa(3)-bdmpza)] (5), [TiCl(3)(kappa(3)-bdmpzdta)] (6), and [TiCl(2)(kappa(2)-bdmpzdta)(2)] (7), and cationic complexes, namely [TiCl(2)(THF)(kappa(3)-bdmpza)]Cl (8) and [TiCl(2)(THF)(kappa(3)-bdmpzdta)]Cl (9), were isolated. Complexes 8 and 9 undergo an interesting nucleophilic THF ring-opening reaction to give the corresponding alkoxide-containing species [TiCl(2)(kappa(3)-bdmpza)(O(CH(2))(4)Cl)] (10) and [TiCl(2)(kappa(3)-bdmpzdta)(O(CH(2))(4)Cl)] (11). A family of alkoxide-containing complexes of general formulas [TiCl(2)(kappa(3)-bdmpza)(OR)] [R = Me (12); R = Et (14); R = (i)Pr (16); R = (t)Bu (18)] and [TiCl(2)(kappa(3)-bdmpzdta)(OR)] [R = Me (13); R = Et (15); R = (i)Pr (17)] was also prepared. The structures of these complexes have been determined by spectroscopic methods, and in addition, the X-ray crystal structures of 3, 7, 10, and 11 were also established.     

Novel rhenium(V) oxo complexes containing bis(pyrazol-1-yl)acetate and bis(pyrazol-1-yl) sulfonate as tripodal N,N,O-heteroscorpionate ligands

Reactions of [NBu4][Re(O)Cl4] with bis(pyrazol-1-yl)methane (bpzm) and bis(pyrazol-1-yl)acetate (Hbpza) and with the lithium salts lithium [bis(3,5-dimethylpyrazol-1-yl)acetate] (Libdmpza) and lithium [bis(3,5-dimethylpyrazol-1-yl)methanesulfonate] (Libdmpzs) produce a series of new compounds containing either a kappa2-N,N bidentate pyrazolyl ligand [Re(O)(bpzm)Cl3 (1), Re(O)(bpzm)(OMe)Cl2 (2), Re(O)(bpzaOMe)(OMe)Cl2 (4)] or a kappa3-N,N,O heteroscorpionate [Re(O)(bpza)Cl2 (3), Re(O)(bdmpza)Cl2 isomers 5 and 6, Re(O)(bdmpza)(OMe)Cl (7), Re(O)(bdmpza)(OEt)Cl (8), Re(O)(bdmpzs)(OMe)Cl (9), Re(O)(bdmpzs)(OEt)Cl (10)]. X-ray analyses of 1 and 3 show in both cases a distorted octahedral environment around the rhenium atom. The nature and the geometry of the products are strongly determined by the reaction solvent and by the heteroscorpionate ligand itself. When scorpionates bear methylated pyrazolyl rings mixed heterocomplexes Re(O)(bdmpza)(glycol) (11) and Re(O)(bdmpzs)(glycol) (12) are obtained (H2glycol = ethylene glycol). Also 11 shows an octahedral geometry as assessed by X-ray study.     

Ruthenium(II) and palladium(II) complexes with 2,6-(bispyrazol-1-yl)pyridines

Ruthenium(II) and palladium(II) complexes [Ru(DMSO)(L)Cl₂] and [Pd(L)Cl]Cl, where L = 2,6-bis(pyrazol-1-yl)pyridine (bpp) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (bdmpp) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H NMR, UV-Vis, and cyclic voltammetry measurements.     

Bis(imidazolin-2-iminato) rare earth metal complexes: synthesis, structural characterization, and catalytic application

Reaction of anhydrous rare earth metal halides MCl(3) with 2 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH) and 2 equiv of trimethylsilylmethyl lithium (Me(3)SiCH(2)Li) in THF furnished the complexes [(Im(Dipp)N)(2)MCl(THF)(n)] (M = Sc, Y, Lu). The molecular structures of all three compounds were established by single-crystal X-ray diffraction analyses. The coordination spheres around the pentacoordinate metal atoms are best described as trigonal bipyramids. Reaction of YbI(2) with 2 equiv of LiCH(2)SiMe(3) and 2 equiv of the imino ligand Im(Dipp)NH in tetrahydrofuran did not result in a divalent complex, but instead the Yb(III) complex [(Im(Dipp)N)(2)YbI(THF)(2)] was obtained and structurally characterized. Treatment of [(Im(Dipp)N)(2)MCl(THF)(n)] with 1 equiv of LiCH(2)SiMe(3) resulted in the formation of [(Im(Dipp)N)(2)M(CH(2)SiMe(3))(THF)(n)]. The coordination arrangement of these compounds in the solid state at the metal atoms is similar to that found for the starting materials, although the introduction of the neosilyl ligand induces a significantly greater distortion from the ideal trigonal-bipyramidal geometry. [(Im(Dipp)N)(2)Y(CH(2)SiMe(3))(THF)(2)] was used as precatalyst in the intramolecular hydroamination/cyclization reaction of various terminal aminoalkenes and of one aminoalkyne. The complex showed high catalytic activity and selectivity. A comparison with the previously reported dialkyl yttrium complex [(Im(Dipp)N)Y(CH(2)SiMe(3))(2)(THF)(3)] showed no clear tendency in terms of activity.     

Activation of carbodiimide and transformation with amine to guanidinate group by Ln(OAr)3(THF)2 (Ln: lanthanide and yttrium) and Ln(OAr)3(THF)2 as a novel precatalyst for addition of amines to carbodiimides: influence of aryloxide group

Reaction of Ln(OAr(1))(3)(THF)(2) (Ar(1)= [2,6-((t)Bu)(2)-4-MeC(6)H(2)] with carbodiimides (RNCNR) in toluene afforded the RNCNR coordinated complexes (Ar(1)O)(3)Ln(NCNR) (R = (i)Pr (isopropyl), Ln = Y (1) and Yb (2); R = Cy (cyclohexyl), Ln = Y (3)) in high yields. Treatment of 1 and 2 with 4-chloroaniline, respectively, at a molar ratio of 1:1 yielded the corresponding monoguanidinate complex (Ar(1)O)(2)Y[(4-Cl-C(6)H(4)N)C(NH(i)Pr)N(i)Pr](THF) (4) and (Ar(1)O)(2)Yb[(4-Cl-C(6)H(4)N)C(NH(i)Pr)N(i)Pr](THF) (5). Complexes 4 and 5 can be prepared by the reaction of Ln(OAr(1))(3)(THF)(2) with RNCNR and amine in toluene at a 1:1:1 molar ratio in high yield directly. A remarkable influence of the aryloxide ligand on this transformation was observed. The similar transformation using the less bulky yttrium complexes Y(OAr(2))(3)(THF)(2) (Ar(2) = [2,6-((i)Pr)(2)C(6)H(3)]) or Y(OAr(3))(3)(THF)(2) (Ar(3) = [2,6-Me(2)C(6)H(3)]) did not occur. Complexes Ln(OAr(1))(3)(THF)(2) were found to be the novel precatalysts for addition of RNCNR with amines, which represents the first example of catalytic guanylation by the lanthanide complexes with the Ln-O active group. The catalytic activity of Y(OAr(1))(3)(THF)(2) was found to be the same as that of monoguanidinate complex 4, indicating 4 is one of the active intermediates in the present process. The other intermediate, amide complex (Ar(1)O)(2)Ln[(2-OCH(3)-C(6)H(4)NH)(2-OCH(3)-C(6)H(4)NH(2))] (6), was isolated by protonolysis of 4 with 2-OCH(3)-C(6)H(4)NH(2). All the complexes were structurally characterized by X-ray single crystal determination.     

Coordination of 2,2'-bipyridyl and 1,10-phenanthroline to yttrium and lanthanum complexes based on a scorpionate ligand

Reaction of yttrium and lanthanum trichloride with 1 equiv of sodium or potassium hydrotris(3,5-dimethylpyrazolyl)borate and 1 equiv of 2,2'-bipyridine gives good yields of the complexes [MCl(2)(Tp(Me2))(C(10)H(8)N(2))] (M = Y (1), La (2)). The analogous compounds with 1,10-phenanthroline, [MCl(2)(Tp(Me2))(C(12)H(8)N(2))] (M = Y (3), La (4)), have been obtained by a similar procedure. The solid-state structures of 2-4 were determined by single-crystal X-ray diffraction and revealed that the compounds are all seven-coordinate with capped octahedral geometry. In contrast, reaction of yttrium trichloride with 1 equiv of sodium hydrotris(3,5-dimethylpyrazolyl)borate in the presence of 1 equiv of neocuproine affords [YCl(3)(Tp(Me2))][Na(neoc)(3))] (5). Compounds 1 and 2 provide an entry for the synthesis of complexes containing the bipyridyl ligand in a radical anionic form or in a dianionic form. Reaction of 1 and 2 with an excess of sodium amalgam gives [Y(Tp(Me2))(bipy)(THF)(2)] (6) and [La(Tp(Me2))(2)(bipy)] (7), respectively. The structures of both compounds have been determined by X-ray crystallography. Compound 7 can be oxidized with iodine to give [La(Tp(Me2))(2)(bipy)]I (8).     

Structural diversity in solvated lithium aryloxides. Syntheses, characterization, and structures of [Li(OAr)(THF)x]n and [Li(OAr)(py)x]2 complexes where OAr = OC6H5, OC6H4(2-Me), OC6H3(2,6-(Me))2, OC6H4(2-Pr(i)), OC6H3(2,6-Pr(i)))2, OC6h4(2-Bu(t)), OC6H3(2,6-Bu(t)))2

A series of sterically varied aryl alcohols H-OAr [OAr = OC6H5 (OPh), OC6H4(2-Me) (oMP), OC6H3(2,6-(Me))2 (DMP), OC6H4(2-Pr(i)) (oPP), OC6H3(2,6-(Pr(i)))2 (DIP), OC6H4(2-Bu(t)) (oBP), OC6H3(2,6-(Bu(t)))2 (DBP); Me = CH3, Pr(i) = CHMe2, and Bu(t) = CMe3] were reacted with LiN(SiMe3)2 in a Lewis basic solvent [tetrahydrofuran (THF) or pyridine (py)] to generate the appropriate "Li(OAr)(solv)x". In the presence of THF, the OPh derivative was previously identified as the hexagonal prismatic complex [Li(OPh)(THF)]6; however, the structure isolated from the above route proved to be the tetranuclear species [Li(OPh)(THF)]4 (1). The other "Li(OAr)(THF)x" products isolated were characterized by single-crystal X-ray diffraction as [Li(OAr)(THF)]4 [OAr = oMP (2), DMP (3), oPP (4)], [Li(DIP)(THF)]3 (5), [Li(oBP)(THF)2]2, (6), and [Li(DBP)(THF)]2, (7). The tetranuclear species (1-4) consist of symmetric cubes of alternating tetrahedral Li and pyramidal O atoms, with terminal THF solvent molecules bound to each metal center. The trinuclear species 5 consists of a six-membered ring of alternating trigonal planar Li and bridging O atoms, with one THF solvent molecule bound to each metal center. Compound 6 possesses two Li atoms that adopt tetrahedral geometries involving two bridging oBP and two terminal THF ligands. The structure of 7 was identical to the previously reported [Li(DBP)(THF)]2 species, but different unit cell parameters were observed. Compound 7 varies from 6 in that only one solvent molecule is bound to each Li metal center of 7 because of the steric bulk of the DBP ligand. In contrast to the structurally diverse THF adducts, when py was used as the solvent, the appropriate "Li(OAr)(py)x" complexes were isolated as [Li(OAr)(py)2]2 (OAr = OPh (8), oMP (9), DMP (10), oPP (11), DIP (12), oBP (13)) and [Li(DBP)(py)]2 (14). Compounds 8-13 adopt a dinuclear, edge-shared tetrahedral complex. For 14, because of the steric crowding of the DBP ligand, only one py is coordinated, yielding a dinuclear fused trigonal planar arrangement. Two additional structure types were also characterized for the DIP ligand: [Li(DIP)(H-DIP)(py)]2 (12b) and [Li2(DIP)2(py)3] (12c). Multinuclear (6,7Li and 13C) solid-state MAS NMR spectroscopic studies indicate that the bulk powder possesses several Li environments for "transitional ligands" of the THF complexes; however, the py adducts possess only one Li environment, which is consistent with the solid-state structures. Solution NMR studies indicate that "transitional" compounds of the THF precursors display multiple species in solution whereas the py adducts display only one lithium environment.     

Synthesis and characterization of organo-scandium and yttrium complexes stabilized by phosphinoamide ligands

Addition of three equivalents of phosphinoamine, (ArNHP(i)Pr(2)) [Ar = 3,5-dimethylphenyl] to M(CH(2)SiMe(3))(3)(THF)(2) [M = Sc, Y] precursors gives complexes of the form (ArNP(i)Pr(2))(3)M(THF) [M = Sc, Y]. In the case of scandium, addition of Sc(CH(2)SiMe(3))(3)(THF)(2) to (ArNP(i)Pr(2))(3)Sc(THF) affords (ArNP(i)Pr(2))(2)Sc(CH(2)SiMe(3))(THF), which has been isolated and structurally characterized. In contrast, addition of Y(CH(2)SiMe(3))(3)(THF)(2) to (ArNP(i)Pr(2))(3)Y(THF) generates a distribution of phosphinoamide-containing products consistent with the formulations (ArNP(i)Pr(2))(2)Y(CH(2)SiMe(3))(THF) and (ArNP(i)Pr(2))Y(CH(2)SiMe(3))(2)(THF), as ascertained using NMR spectroscopy. Attempts to react the alkyl-containing phosphinoamide complexes with small molecules such as H(2) led to disproportionation type processes.     

(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.     

Structural and magnetic studies of the tris(cyclopentadienyl)manganese(II) "paddle-wheel" anions [Cp(3-n)(MeCp)(n)Mn](-) (n=0-3, MeCp=C(5)H(4)CH(3), Cp=C(5)H(5))

The ion-contact complexes [{(eta(5)-Cp)(2)Mn(eta(2):eta(5)-Cp)K}(3)]x0.5 THF (1x0.5 THF) and [{(eta(2)-Cp)(2)(eta(2);eta(5)-MeCp)MnK(thf)}]x2 THF (2x2 THF) and ion-separated complexes [Mg(thf)(6)][(eta(2)-Cp)(3)Mn](2) (3), [Mg(thf)(6)][(eta(2)-Cp)(eta(2)-MeCp)(2)Mn)](2)x0.5 THF (4x0.5 THF), [Mg(thf)(6)][(eta(2)-MeCp)(3)Mn)](2)x0.5 THF (5x0.5 THF) and [Li([12]crown-4)](5)[(eta-Cp)(3)Mn](5) (6) (Cp=C(5)H(5), CpMe=C(5)H(4)CH(3)), have been prepared and structurally characterised. The effects of varying the Cp and CpMe ligands in complexes 1-5 have been probed by variable-temperature magnetic susceptibility measurements and EPR spectroscopic studies.     

Bis(2,4–pentanedionato)vanadium(IV) aryloxides

Complexes of composition [VCl(acac)2(OAr1–4)] and [V(acac)2(OAr1–4)2] (HOAr1=HOC6H4NO2–4, HOAr2= HOC6H4OMe-4, HOAr3=HOC6H4But-4 and HOAr4= HOC6H2But-2,6–Me-4; acac=2,4–pentanedionato ion) have been synthesized by the reaction of [VCl2(acac)2] with the respective phenols or their trimethylsilyl derivatives. The complexes have been characterized by physicochemical and spectroscopic techniques. They are non-electrolytes in nitrobenzene. Room temperature magnetic moments in the 1.71–1.82B range are consistent with the VIV system. The reactions of [VCl(acac)2(OAr2)] and [VCl(acac)2(OAr3)] with chloride acceptors have been studied by conductance techniques and the formation of ionic complexes of the types [V(acac)2(OAr2,3)][MCl4] (M=Fe, Al or Sb) and [V(acac)2(OAr2,3)][MCl6] (M=P or Sb) is indicated by the conductance composition curves. Several of these complexes have been isolated and characterized.     

Transition metal complexes bearing a 2,2-bis(3,5-dimethylpyrazol-1-yl)propionate ligand: one methyl more matters

The new N,N,O ligand 2,2-bis(3,5-dimethylpyrazol-1-yl)propionic acid (2,2-Hbdmpzp) (2) and its transition metal complexes [Mn(2,2-bdmpzp)(CO)(3)] (3), [Re(2,2-bdmpzp)(CO)(3)] (4), [Cu(2,2-bdmpzp)(2)] (5), and [Ru(2,2-bdmpzp)Cl(L)(PPh(3))] [L = PPh(3) (6), N(2) (7), CO (8a/b), SO(2) (9a/b)] have been synthesized, characterized and compared to analogous complexes bearing a bis(3,5-dimethylpyrazol-1-yl)acetic acid. It was found that the additional methyl group has a remarkable influence on the stability and reactivity of transition metal complexes.     

New palladium(II) and platinum(II) complexes with the model nucleobase 1-methylcytosine: antitumor activity and interactions with DNA

Palladium and platinum complexes with the model nucleobase 1-methylcytosine (1-Mecyt) of the types [Pd(N-N)(C6F5)(1-Mecyt)]ClO4 [N-N = bis(3,5-dimethylpyrazol-1-yl)methane (bpzm), bis(pyrazol-1-yl)methane (bpzm), N,N,N',N'-tetramethylethylenediamine (tmeda), or 2,2'-bipyridine (bpy)] and [M(dmba)(L')(1-Mecyt)]ClO4 [dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl; L' = PPh(3) (M = Pd or Pt), DMSO (M = Pt)] have been obtained. Palladium and platinum complexes of the types cis-[M(C6F5)2(1-Mecyt)2] (M = Pd or Pt) and cis-[Pd(L')(C6F5)(1-Mecyt)2]ClO4 (L' = PPh(3) or t-BuNC) have also been prepared. The crystal structures of [Pd(bpzm)(C6F5)(1-Mecyt)]ClO4, [Pt(dmba)(DMSO)(1-Mecyt)]ClO4, cis-[Pd(C6F5)2(1-Mecyt)2], and cis-[Pd(t-BuNC)(C6F5)(1-Mecyt)2]ClO4 have been established by X-ray diffraction. There is extensive hydrogen bonding (N-H...O, C-H...F or C-H...O) in all the compounds. There are also intermolecular pi-pi interactions between pyrimidine rings of adjacent chains in [Pd(C6F5)2(1-Mecyt)2]. DNA adduct formation of the new complexes synthesized was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by the complexes on plasmid DNA pBR322 were also obtained. Values of IC(50) were also calculated for the new complexes against the tumor cell line HL-60. At a short incubation time (24 h) almost all new complexes were more active than cisplatin.