Metal versus ligand alkylation in the reactivity of the (bis-iminopyridinato)Fe catalyst

The alkylation of the Brookhart-Gibson {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)} FeCl2 precatalyst with 2 equiv of LiCH2Si(CH3)3 led to the isolation of several catalytically very active products depending on the reaction conditions. The expected dialkylated species {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2}(C5H3N)Fe(CH2SiMe3)2 (2) was indeed the major component of the reaction mixture. However, other species in which alkylation occurred at the pyridine ring ortho position, {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2-2-CH2SiMe3}(C5H3N)Fe(CH2SiMe3) (1), and at the imine C atom, {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC(CH3)(CH2 SiMe3)](C5H3N)}Fe(CH2SiMe3) (3), have also been isolated and fully characterized. In addition, deprotonation of the methyl-imino functions and formation of a new divalent Fe catalyst {[2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}Fe(mu-Cl)Li(THF)3 (4) also occurred depending on the reaction conditions. In turn, the formation of 4 might trigger the reductive coupling of two units through the methyl-carbon wings. This process resulted in the one-electron reduction of the metal center, affording a dinuclear Fe(I) alkyl catalyst {[{[2,6-(i-Pr)2C6H5]N=C(CH3)}(C5H3N){[2,6-(i-Pr)26H5]N=CCH2}Fe(CH2SiMe3)]}2 (5). Different from other metal derivatives, complex 5 could not be prepared from the monodeprotonated version of the ligand. Its reaction with a mixture of FeCl2 and RLi afforded instead [{2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}FeCH2Si(CH3)3][Li(THF)4] (6) which is also catalytically active. All of these high-spin species have been shown to have high catalytic activity for olefin polymerization, producing polymers of two distinct natures, depending on the formal oxidation state of the metal center.     

Dinitrogen activation, partial reduction, and formation of coordinated imide promoted by a chromium diiminepyridine complex

Reduction of {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}CrCl (3) with NaH afforded the dinuclear dinitrogen complex {[{2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}Cr(THF)]2(mu-N2)}.THF (5). Reaction carried in exclusion of dinitrogen afforded instead deprotonation of the ligand with the formation of {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(THF) (4). Further reduction of 5 with NaH yielded a curious dinuclear compound formulated as [{2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}Cr(THF)][{2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(THF)](mu-N2 H)(mu-Na)2 (6) containing two sodium atoms only bound to the dinitrogen unit and the pi systems of the two diiminepyridine ligands. Subsequent reduction with NaH triggered a complex series of events, leading to the formation of a species formulated as {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(mu-NH)][Na(THF)] (7) on the basis of crystallographic, spectroscopic, isotopic labeling, and chemical degradation experiments.     

The impact of P-substituents on the structures, spectroscopic properties, and reactivities of POCOP-type pincer complexes of nickel(II)

The room temperature reaction of NiBr(2)(NCCH(3))(x) with the pincer-type ligand POCHOP(Ph) gave the new pincer complex (POCOP(Ph))NiBr (1, POCOP(Ph) = κ(P), κ(C), κ(P)-2,6-{Ph(2)PO}(2)C(6)H(3)). Complex 1 reacts with AgX to give the analogous Ni-X derivatives (X = CN, 2; OSO(2)CF(3), 3; OC(O)CH(3), 4; ONO(2), 5), whereas complex 3 reacts with phenylacetylene and NEt(3) to give the Ni-CCPh derivative 6. On the other hand, reaction of 1 or 3 with RLi or RMgI did not afford the desired Ni-R derivatives, giving instead the corresponding iodo and hydroxo derivatives. Complexes 1-6 have been characterized by NMR, IR, and UV-Vis spectroscopy and X-ray crystallography. The solid state structural and IR data indicate that Ni-C(sp) interaction is dominated by ligand-to-metal σ-donation in 2 and 6. Cyclic voltammetry measurements indicate that complexes 3 and 4 display reversible redox behaviour (Ni(II)/Ni(III)); comparison of the E(0)(1/2) values for these complexes and their POCOP(i-Pr) analogues shows that both the X ligands and the P-substituent have a considerable impact on the ease of oxidation in this family of complexes.     

Dinitrogen partial reduction by formally zero- and divalent vanadium complexes supported by the bis-iminopyridine system

Reduction of the two trivalent 2,6-{[2,6-(i-Pr)2C6H5]N=C(CH3)}2(C5H3N)VCl3 and {[2,6-{[2,6-(i-Pr)2C6H3]N-C=(CH2)}2(C5H3N)]VCl(THF) complexes with excess NaH afforded two corresponding end-on dinitrogen-bridged complexes [2,6-{[2,6-(i-Pr)2C6H5]N=C(CH3)}2(C5H3N)V]2(m-N2).(hexane) (1) and [{[2,6-{[2,6-(i-Pr)2C6H3]N-C=(CH2)}2(C5H3N)]V]2(m-N2).(hexane) (3). Despite their very close structural similarity, the two species have completely different natures. The first is paramagnetic and may be regarded as generated by the two-electron attack of two formally zerovalent vanadium moieties on the same N2 unit. In the nearly diamagnetic 3 instead, the N2 unit has been reduced by two vanadium atoms, formally divalent. Structural analysis and DFT calculations have indicated that partial reduction of the bridging nitrogen occurred for both complexes while, in the case of 1, substantial metal-to-ligand electron transfer also occurs.     

Ni(II) complexes featuring non-metallated pincer-type ligands

Attempts to prepare pincer-type Ni complexes from the ligands (i-Pr(2)POCH(2))(2)CH(2) and (pz*CH(2))(2)CH(2) (pz* = 3,5-dimethylpyrazol-1-yl) gave instead the complexes cis-{kappa(P),kappa(P')-(i-Pr(2)POCH(2))(2)CH(2)}NiCl(2) and {kappa(N),kappa(N')-(pz*CH(2))(2)CH(2)}NiBr(2). X-Ray diffraction studies confirmed that these potentially pincer-type ligands have not undergone metallation, serving instead as chelating ligands in essentially square-planar or tetrahedral complexes. Heating of these compounds failed to induce metallation of the coordinated ligands.     

Preparation, characterization, and magnetic behavior of the ln derivatives (ln = nd, la) of a 2,6-diiminepyridine ligand and corresponding dianion

An unprecedented Nd[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N)]NdI(2)(THF) (1) complex was prepared by oxidizing metallic Nd with I(2) in THF and in the presence of 2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N). The magnetic behavior at variable T clearly indicated that the complex should be regarded as a trivalent Nd atom antiferromagnetically coupled to a radical anion. By using the doubly deprotonated form of the diimino pyridine ligand [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)](2-) (2) the corresponding trivalent complexes [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)]Ln (THF)](mu-Cl)(2)[Li(THF)(2)].0.5 (hexane) [Ln = Nd (3), La (4)] were obtained and characterized. Reduction of these species afforded electron transfer to the ligand system which gave ligand dimerization via C-C bond formation through one of the two ene-amido functions of each molecule. The resulting dinuclear [[([2,6-(i-Pr)(2)C(6)H(5)]N-C=(CH(2)))(C(5)H(3)N)([2,6-(i-Pr)(2)C(6)H(5)]N=CCH(2))]Ln(THF)(2)(mu-Cl)[Li(THF)(3)])(2).2(THF) [Ln = Nd (5), La (6)] were isolated and characterized.     

New pincer-type diphosphinito (POCOP) complexes of NiII and NiIII

This communication reports the synthesis and characterization of the new, pincer-type, square-planar, 16-electron compounds {2,6-(OPPr(i)(2))(2)C(6)H(3)}Ni(II)Br, 1, and {(Pr(i)(2)POCH(2))(2)CH}Ni(II)Br, 2, and the square-pyramidal, 17-electron complex {(Pr(i)(2)POCH(2))(2)CH}Ni(III)Br(2), 3.     

Imido Complexes Derived from the Reactions of Niobium and Tantalum Pentachlorides with Primary Amines: Relevance to the Chemical Vapor Deposition of Metal Nitride Films

Reactions of niobium and tantalum pentachlorides with tert-butylamine (>/=6 equiv) in benzene afford the dimeric imido complexes [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (90%) and [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) (79%). The niobium complex exists as two isomers in solution, while the tantalum complex is composed of three major isomers and at least two minor isomers. Analogous treatments with isopropylamine (>/=7 equiv) give the monomeric complexes NbCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%) and TaCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2) (84%). The monomeric complexes are unaffected by treatment with excess isopropylamine, while the dimeric complexes are cleaved to the monomers MCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)(2) upon addition of excess tert-butylamine in chloroform solution. Treatment of niobium and tantalum pentachlorides with 2,6-diisopropylaniline affords insoluble precipitates of [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%) and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (100%), which react with 4-tert-butylpyridine to afford the soluble complexes [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (45%) and [4-t-C(4)H(9)C(5)H(4)NH](2)[TaCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] (44%). Sublimation of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), MCl(2)(N(i)Pr)(NH(i)Pr)(NH(2)(i)Pr)(2), and [NH(3)(2,6-(CH(CH(3))(2))(2)C(6)H(3))](2)[MCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] leads to decomposition to give [MCl(3)(NR)(NH(2)R)](2) as sublimates (32-49%), leaving complexes of the proposed formulation MCl(NR)(2) as nonvolatile residues. By contrast, [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) sublimes without chemical reaction. Analysis of the organic products obtained from thermal decomposition of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2) showed isobutylene and tert-butylamine in a 2.2:1 ratio. Mass spectra of [NbCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), [TaCl(2)(N(t)Bu)(NH(t)Bu)(NH(2)(t)Bu)](2), and [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) showed the presence of dimeric imido complexes, monomeric imido complexes, and nitrido complexes, implying that such species are important gas phase species in CVD processes utilizing these molecular precursors. The crystal structures of [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))], [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2), [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2), and [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) were determined. [4-t-C(4)H(9)C(5)H(4)NH](2)[NbCl(5)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))] crystallizes in the space group P2(1)/c with a = 12.448(3) ?, b = 10.363(3) ?, c = 28.228(3) ?, beta = 94.92(1) degrees, V = 3628(5) ?(3), and Z = 4. [NbCl(3)(N(i)Pr)(NH(2)(i)Pr)](2) crystallizes in the space group P2(1)/c with a = 9.586(4) ?, b = 12.385(4) ?, c = 11.695(4) ?, beta = 112.89(2) degrees, V = 1279.0(6) ?(3), and Z = 2. [NbCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.285(3) ?, b = 11.208(3) ?, c = 23.867(6) ?, beta = 97.53 degrees, V = 2727(1) ?(3), and Z = 2. [TaCl(3)(N(2,6-(CH(CH(3))(2))(2)C(6)H(3)))(NH(2)(2,6-(CH(CH(3))(2))(2)C(6)H(3)))](2) crystallizes in the space group P2(1)/n with a = 10.273(1) ?, b = 11.241(2) ?, c = 23.929(7) ?, beta = 97.69(2) degrees, V = 2695(2) ?(3), and Z = 2. These findings are discussed in the context of niobium and tantalum nitride film depositions from molecular precursors.     

Thiosemicarbazone derivatives of nickel and copper: the unprecedented coordination of furan ring in octahedral nickel(II) and of triphenylphosphine in three-coordinate copper(I) complexes

The influence of substituents at the C(2) carbon of N(1)-substituted thiosemicarbazones, {C(4)H(3)X-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2)} (X = O, S) on the geometry of nickel(ii) complexes has been investigated. The presence of a methyl group at the C(2) position of 2-acetylfuran-N(1)-substituted thiosemicarbazones {(C(4)H(3)O)-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2), R(2) = CH(3), HaftscN-Me; C(2)H(5), HaftscN-Et; C(6)H(5), HaftscN-Ph} induces unusual coordination by the furan ring and yielded high spin octahedral nickel(II) complexes, [Ni(κ(3)-O, N(3), S-aftscN-R(2))(2)], CH(3)1, C(2)H(5)2, and 2[Ni((κ(3)-O, N(3), S-aftscN-Ph)(2)] 3 (μ(eff) = 2.98, 1; 2.96, 2; 2.92, 3). With 2-acetylthiophene-N(1)-substituted thiosemicarbazones, {(C(4)H(3)S)-C(2)(CH(3))=N(3)-N(2)H-C(1)(=S)N(1)HR(2), R(2) = CH(3), HattscN-Me; C(2)H(5), HattscN-Et; C(6)H(5), HattscN-Ph}, N(3), S chelated low spin trans square planar complexes, {[Ni(κ(3)-O, N(3), S-attscN-R(2))(2)], R(2) = CH(3), 4; C(2)H(5), 5; C(6)H(5), 6} with pendant thiophene rings have been obtained. The bigger sized sulfur atoms of the thiophene rings form short intramolecular contacts with the deprotonated hydrazinic nitrogen atoms (SN(2)) inhibiting its lability for possible coordination to nickel(II). Complexes have one independent molecule (1) or two independent molecules (2, 3) in their respective crystal lattices. The simultaneous presence of methyl groups at the C(2) and N(1) atoms of 2-acetylthiophene-N(1)-methylthiosemicarbazone (HattscN-Me) have facilitated the binding of triphenylphosphine in three-coordinate copper(i) halide complexes, [CuX(η(1)-S-HattscN-Me)(Ph(3)P)] (X, Br, 7; Cl, 8), which represent an unusual donor set of ligands, namely, triphenylphosphine, sulfur of a thio-ligand and a halide.     

2-[1-(2,6-Dibenzhydryl-4-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(II) dichlorides: synthesis, characterization and ethylene polymerization behavior

A series of unsymmetrical 2,6-bis(imino)pyridylcobalt(II) complexes, {2-[2,6-(CH(C(6)H(5))(2))(2)-4-Me-C(6)H(2)N==C(CH(3))]-6-(2,6-R(1)(2)-4-R(2)-C(6)H(2)N==CCH(3))-C(5)H(3)NCoCl(2)} where R(1) = Me, Et or (i)Pr, R(2) = H or Me, together with the new symmetrical complex 2,6-[2,6-(CH(C(6)H(5))(2))(2)-4-Me-C(6)H(2)N==C(CH(3))](2)-C(5)H(3)NCoCl(2), were synthesized. All of the compounds were fully characterized by (1)H NMR and IR spectroscopy, as well as by elemental analysis. The molecular structures of Co1 (R(1) = Me, R(2) = H) and Co5 (R(1) = Et, R(2) = Me) were further confirmed by single crystal X-ray diffraction, which indicated that the cobalt centres were penta-coordinate with a pseudo square-pyramidal geometry. Upon treatment with MAO or MMAO, these cobalt pre-catalysts exhibited higher activities than any previously reported cobalt pre-catalysts, with values as high as 4.64 × 10(6) g PE mol(-1)(Co) h(-1) for ethylene polymerization at atmospheric pressure. The polyethylenes obtained were of high molecular weight and narrow molecular weight distribution.     

C-X bond formation and cleavage in the reactions of the ditungsten hydride complex [W2(η5-C5H5)2(H)(μ-PCy2)(CO)2] with small molecules having multiple C-X bonds (X = C, N, O)

Two molecules of C(2)(CO(2)Me)(2) or isocyanides could be added to the title hydride complex under mild conditions to give dienyl-[W(2)Cp(2){μ-η(1),κ:η(2)-C(CO(2)Me)=C(CO(2)Me)C(CO(2)Me)=CH(CO(2)Me)}(μ-PCy(2))(CO)(2)] (Cp = η(5)-C(5)H(5)), diazadienyl-[W(2)Cp(2){μ-κ,η:κ,η-C{CHN(4-MeO-C(6)H(4))}N(4-MeO-C(6)H(4))}(μ-PCy(2))(CO)(2)] or aminocarbyne-bridged derivatives [W(2)Cp(2){μ-CNH(2,6-Me(2)C(6)H(3))}(μ-PCy(2)){CN(2,6-Me(2)C(6)H(3))}(CO)]. In contrast, its reaction with excess (4-Me-C(6)H(4))C(O)H gave the C-O bond cleavage products [W(2)Cp(2){CH(2)(4-Me-C(6)H(4))}(O)(μ-PCy(2))(CO)(2)] and [W(2)Cp(2){μ-η:η,κ-C(O)CH(2)(4-Me-C(6)H(4))}(O)(μ-PCy(2))(CO)].     

Multiple pathways for dinitrogen activation during the reduction of an Fe Bis(iminepyridine) complex

Reduction of the bis(iminopyridine) FeCl(2) complex {2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(C(5)H(3)N)}FeCl(2) using NaH has led to the formation of a surprising variety of structures depending on the amount of reductant. Some of the species reported in this work were isolated from the same reaction mixture, and their structures suggest the presence of multiple pathways for dinitrogen activation. The reaction with 3 equiv of NaH afforded {2-[2,6-(iPr)(2)PhN=C(CH(3))]-6-[2,6-(iPr)(20PhN-C=CH(2)](C(5)H(3)N)}Fe(micro,eta(2)-N(2))Na (THF) (1) containing one N(2) unit terminally bound to Fe and side-on attached to the Na atom. In the process, one of the two imine methyl groups has been deprotonated, transforming the neutral ligand into the corresponding monoanionic version. When 4 equiv were employed, two other dinitrogen complexes {2-[2,6-(iPr)(2)PhN=C(CH(3))]-6-[2,6-(iPr)(2)PhN-C=CH(2)](C(5)H(3)N)}Fe(micro-N2)Na(Et(2)O)(3) (2) and {2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(C(5)H(3)N)}Fe(micro-N(2))Na[Na(THF)(2)] (3) were obtained from the same reaction mixture. Complex 2 is chemically equivalent to 1, the different degree of solvation of the alkali cation being the factor apparently responsible for the sigma-bonding mode of ligation of the N(2) unit to Na, versus the pi-bonding mode featured in 1. In complex 3, the ligand remains neutral but a larger extent of reduction has been obtained, as indicated by the presence of two Na atoms in the structure. A further increase in the amount of reductant (12 equiv) afforded a mixture of {2-[2,6-(iPr)(2)PhN=C(CH(3))]-6-[2,6-(iPr)(2)PhN-C=CH(2)](C(5)H(3)N)}Fe-N(2) (4) and [{2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(C(5)H(3)N)}Fe-N(2)](2)(micro-Na) [Na(THF)(2)](2) (5) which were isolated by fractional crystallization. Complex 4, also containing a terminally bonded N(2) unit and a deprotonated anionic ligand bearing no Na cations, appears to be the precursor of 1. The apparent contradiction that excess NaH is required for its successful isolation (4 is the least reduced complex of this series) is most likely explained by the formation of the partner product 5, which may tentatively be regarded as the result of aggregation between 1 and 3 (with the ligand system in its neutral form). Finally, reduction carried out in the presence of additional free ligand afforded {2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(C(5)H(3)N)}Fe(eta(1)-N(2)){2,6-[2,6-(iPr)(2)PhN=C(CH(3))](20(NC(5)H(2))}[Na(THF)(2)] (6) and {2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(C(5)H(3)N)}Fe{2,6-[2,6-(iPr)(2)PhN=C(CH(3))](2)(NC(5)H(2))}Na(THF)(2)) (7). In both species, the Fe metal is bonded to the pyridine ring para position of an additional (L)Na unit. Complex 6 chemically differs from 7 (the major component) only for the presence of an end-on coordinated N(2).     

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).     

Structures and magnetic properties of an antiferromagnetically coupled polymeric copper(II) complex and ferromagnetically coupled hexanuclear nickel(II) clusters

Reactions between 2,6-diformyl-4-methylphenol (DFMF) and tris(hydroxymethyl) aminomethane (THMAM = H(3)L2) in the presence of copper(II) salts, CuX(2) (X = CH(3)CO(2)(-), BF(4)(-), ClO(4)(-), Cl(-), NO(3)(-)) and Ni(CH(3)CO(2))(2) or Ni(ClO(4))(2)/NaC(6)H(5)CO(2), sodium azide (NaN(3)), and triethylamine (TEA), in one pot self-assemble giving a coordination polymer consisting of repeating pentanuclear copper(II) clusters {[Cu(2)(H(5)L(2-))(μ-N(3))](2)[Cu(N(3))(4)]·2CH(3)OH}(n) (1) and hexanuclear Ni(II) complexes [Ni(6)(H(3)L1(-))(2)(HL2(2-))(2)(μ-N(3))(4)(CH(3)CO(2))(2)]·6C(3)H(7)NO·C(2)H(5)OH (2) and [Ni(6)(H(3)L1(-))(2)(HL2(2-))(2)(μ-N(3))(4)(C(6)H(5)CO(2))(2)]·3C(3)H(7)NO·3H(2)O·CH(3)OH (3). In 1, H(5)L(2-) and in 2 and 3 H(3)L1(-) and HL2(2-) represent doubly deprotonated, singly deprotonated, and doubly deprotonated Schiff-base ligands H(7)L and H(4)L1 and a tripodal ligand H(3)L2, respectively. 1 has a novel double-stranded ladder-like structure in which [Cu(N(3))(4)](2-) anions link single chains comprised of dinuclear cationic subunits [Cu(2)(H(5)L(2-))(μ-N(3))](+), forming a 3D structure of interconnected ladders through H bonding. Nickel(II) clusters 2 and 3 have very similar neutral hexanuclear cores in which six nickel(II) ions are bonded to two H(4)L1, two H(3)L2, four μ-azido, and two μ-CH(3)CO(2)(-)/μ-C(6)H(5)CO(2)(-) ligands. In each structure two terminal dinickel (Ni(2)) units are connected to the central dinickel unit through four doubly bridging end-on (EO) μ-azido and four triply bridging μ(3)-methoxy bridges organizing into hexanuclear units. In each terminal dinuclear unit two nickel centers are bridged through one μ-phenolate oxygen from H(3)L1(-), one μ(3)-methoxy oxygen from HL2(2-), and one μ-CH(3)CO(2)(-) (2)/μ-C(6)H(5)CO(2)(-) (3) ion. Bulk magnetization measurements on 1 show moderately strong antiferromagnetic coupling within the [Cu(2)] building block (J(1) = -113.5 cm(-1)). Bulk magnetization measurements on 2 and 3 demonstrate that the magnetic interactions are completely dominated by ferromagnetic coupling occurring between Ni(II) ions for all bridges with coupling constants (J(1), J(2), and J(3)) ranging from 2.10 to 14.56 cm(-1) (in the ? = -J(1)(?(1)?(2)) - J(1)(?(2)?(3)) - J(2)(?(3)?(4)) - J(1)(?(4)?(5)) - J(1)(?(5)?(6)) - J(2)(?(1)?(6)) - J(3)(?(2)?(6)) - J(3)(?(2)?(5)) - J(3)(?(3)?(5)) convention).     

Chiral uranium phosphonates constructed from achiral units with three-dimensional frameworks

Two chiral, porous uranium methylenediphosphonates, [C(2)H(10)N(2)]{UO(2)[CH(2)(PO(3))(2)]}·H(2)O (UC1P2N-1) and [N(C(2)H(5))(4)]K{(UO(2))(3)[CH(2)(PO(3))(2)](2)(H(2)O)(2)}·1.5H(2)O (KUC1P2-1), have been synthesized without chiral starting materials. Both compounds display channels ~1 × 1 nm that are large enough for these materials to conduct ion-exchange with coordination complexes such as [Co(en)(3)](3+).     

Substituent effects on Ni-S bond dissociation energies and kinetic stability of nickel arylthiolate complexes supported by a bis(phosphinite)-based pincer ligand

Pincer complexes of the type [2,6-(R(2)PO)(2)C(6)H(3)]NiSC(6)H(4)Z (R = Ph and i-Pr; Z = p-OCH(3), p-CH(3), H, p-Cl, and p-CF(3)) have been synthesized from [2,6-(R(2)PO)(2)C(6)H(3)]NiCl and sodium arylthiolate. X-ray structure determinations of these thiolate complexes have shown a somewhat constant Ni-S bond length (approx. 2.20 ?) but an almost unpredictable orientation of the thiolate ligand. Equilibrium constants for various thiolate exchange (between a nickel thiolate complex and a free thiol, or between two different nickel thiolate complexes) reactions have been measured. Evidently, the thiolate ligand with an electron-withdrawing substituent prefers to bond with "[2,6-(Ph(2)PO)(2)C(6)H(3)]Ni" rather than "[2,6-(i-Pr(2)PO)(2)C(6)H(3)]Ni", and bonds least favourably with hydrogen. The reactions of the thiolate complexes with halogenated compounds such as PhCH(2)Br, CH(3)I, CCl(4), and Ph(3)CCl have been examined and several mechanistic pathways have been explored.     

Solution- and solid-state characterisation of a configurationally-stable beta-diketiminato-supported calcium primary amide

'Selective' protonolysis of the beta-diketiminato calcium derivative [Ca[(NDippCMe)(2)CH][N(SiMe(3))(2)](THF)] Dipp = C(6)H(3)(i)Pr(2)-2,6) with H(2)N(CH(2))(2)OCH(3) produced the dimeric species [Ca[(NDippCMe)(2)CH][mu-NH(CH(2))(2)OMe]](2), which has been fully characterised in solution and in the solid state.     

Osmium-mediated C--H and C--C bond cleavage of a phenolic substrate: p-quinone methide and methylene arenium pincer complexes

The diphosphine 2,4,6-(CH(3))(3)-3,5-(iPr(2)PCH(2))(2)C(6)OH (1) reacts with [OsCl(2)(PPh(3))(3)] in presence of an excess of triethylamine to yield the isomeric para-quinone methide derivatives [Os{4-(CH(2))-1-(O)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))] (2 and 3), which differ in the positions of the mutually trans hydride and chloride ligands. Complex 2 reacts with CO to afford the dicarbonyl species [Os{1-(O)-2,4,6-(CH(3))(3)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(CO)(2)] (4), which results from hydride insertion into the quinonic double bond. Protonation of 2 and 3 leads to the formation of the methylene arenium derivative [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))][OSO(2)CF(3)] (5 a). The diphosphine 1 reacts with [OsCl(2)(PPh(3))(3)] at 100 degrees C under H(2) to afford [Os{1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H(2))(PPh(3))] (6), a PCP pincer complex resulting formally from C(sp(2))--C(sp(3)) cleavage of the C--CH(3) group in 1. C--C hydrogenolysis resulting in the same complex is achieved by heating 2 under H(2) pressure. Reaction of the diphosphine substrate with [OsCl(2)(PPh(3))(3)] under H(2) at lower temperature allows the observation of a methylene arenium derivative resulting from C--H activation, [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(2)(H)] (7). This compound reacts with PPh(3) in toluene to afford the ionic derivative [Os{4-(CH(2))-1-(OH)-2,6-(CH(3))(2)-3,5-(iPr(2)PCH(2))(2)C(6)}(Cl)(H)(PPh(3))]Cl (5 b). X-ray diffraction studies have been carried out on compounds 2, 3, 4, 5 b, 6, and 7, which allows the study of the structural variations when going from methylene arenium to quinone methide derivatives.     

Tetravalent titanium, zirconium, and cerium oxo and peroxo complexes containing an imidodiphosphinate ligand

Dinuclear Ti(IV), Zr(IV), and Ce(IV) oxo and peroxo complexes containing the imidodiphosphinate ligand [N(i-Pr(2)PO)(2)](-) have been synthesized and structurally characterized. Treatment of Ti(O-i-Pr)(2)Cl(2) with KN(i-Pr(2)PO)(2) afforded the Ti(IV) di-μ-oxo complex [Ti{N(i-Pr(2)PO)(2)}(2)](2)(μ-O)(2) (1) that reacted with 35% H(2)O(2) to give the peroxo complex Ti[N(i-Pr(2)PO)(2)](2)(η(2)-O(2)) (2). Treatment of HN(i-Pr(2)PO)(2) with Zr(O-t-Bu)(4) and Ce(2)(O-i-Pr)(8)(i-PrOH)(2) afforded the di-μ-peroxo-bridged dimers [M{N(i-Pr(2)PO)(2)}(2)](2)(μ-O(2))(2) [M = Zr (3), Ce (4)]. 4 was also obtained from the reaction of Ce[N(i-Pr(2)PO)(2)](3) with 35% H(2)O(2). Treatment of (Et(4)N)(2)[CeCl(6)] with 3 equiv of KN(i-Pr(2)PO)(2) afforded Ce[N(i-Pr(2)PO)(2)](3)Cl (5). Reaction of (Et(4)N)(2)[CeCl(6)] with 2 equiv of KN(i-Pr(2)PO)(2) in acetonitrile, followed by treatment with Ag(2)O, afforded the μ-oxo-bridged complex [Ce{N(i-Pr(2)PO)(2)}Cl](2)[μ-N(i-Pr(2)PO)(2)](2)(μ-O) (6). 6 undergoes ligand redistribution in CH(2)Cl(2) in air to give 5. The solid-state structures of [K(2){N(i-Pr(2)PO)(2)}(2)(H(2)O)(8)](n) and complexes 1-6 have been determined.     

Synthesis and characterization of silver(I) adducts supported solely by 1,3,5-triazapentadienyl ligands or by triazapentadienyl and other N-donors

Halogenated 1,3,5-triazapentadienyl ligands [N{(C(3)F(7))C(C(6)F(5))N}(2)](-), [N{(CF(3))C(C(6)F(5))N}(2)](-) and [N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)](-), alone or in combination with other N-donors like CH(3)CN, CH(3)(CH(2))(2)CN, and N(C(2)H(5))(3), have been used in the stabilization of thermally stable, two-, three- or four-coordinate silver(i) adducts. X-Ray crystallographic analyses of {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag}(n), {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(NCCH(3))}(n), {[N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)]Ag(NCCH(3))}(n), {[N{(CF(3))C(C(6)F(5))N}(2)]Ag(NCCH(3))(2)}(n) and {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(NCC(3)H(7))}(n) revealed the presence of bridging 1,3,5-triazapentadienyl ligands bonded to silver through terminal nitrogen atoms. These adducts are polymeric in the solid state. [N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)]AgN(C(2)H(5))(3) is monomeric and features a 1,3,5-triazapentadienyl ligand bonded to Ag(I) in a κ(1)-fashion via only one of the terminal nitrogen atoms. The solid state structure of [N{(C(3)F(7))C(C(6)F(5))N}(2)]H has also been reported and it forms polymeric chains via inter-molecular N-H···N hydrogen-bonding.