Sulfur-alkylation-initiated CpRu thiyl radicals

The formation of thiyl radicals from [Cp^∗Ru^III{κ³SSS′-tpdt}] (1A) and [Cp^∗Ru^III{κ³SSN-apdt}] (1B) {Cp^∗ = η⁵-C₅Me₅; tpdt = S(CH₂CH₂S⁻)₂; apdt = HN(CH₂CH₂S⁻)₂} has been initiated by thiolate alkylation or oxidation with iodine. Subsequent electron transfer processes yielded disulfide-bridged dinuclear complexes. The mechanistic pathways of these processes will be discussed.     

Half-sandwich dibenzyl complexes of scandium: Synthesis, structure, and styrene polymerization activity

Half-sandwich dibenzyl complexes of scandium have been prepared by stepwise treatment of scandium trichloride with lithium derivatives of silyl-functionalized tetramethylcyclopentadienes (C₅Me₄H)SiMe₂R (R = Me, Ph) and benzyl magnesium chloride. The resulting complexes [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] and [Sc(η⁵-C₅Me₄SiMe₂Ph)(CH₂Ph)₂(1,4-dioxane)] show structure related to that of the corresponding bis(trimethylsilylmethyl) compounds [Sc(η⁵-C₅Me₄SiMe₂R)(CH₂SiMe₃)₂(THF)]. The four-coordinate complexes display η¹-coordinated benzyl ligands without significant interaction of the ipso-carbon of the phenyl moiety. Conversion of [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] into the cationic species by treatment with triphenylborane in THF led to the formation of a stable charge separated complex [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)(THF)_x][BPh₃(CH₂Ph)]. Benzyl cation formed using [Ph₃C][B(C₆F₅)₄] in toluene resulted in a moderately active syndiospecific styrene polymerization catalyst.     

Rare earth metal bis(alkyl) complexes bearing amino phosphine ligands: Synthesis and catalytic activity toward ethylene polymerization

Reactions of neutral amino phosphine compounds HL^1-3 with rare earth metal tris(alkyl)s, Ln(CH₂SiMe₃)₃(THF)₂, afforded a new family of organolanthanide complexes, the molecular structures of which are strongly dependent on the ligand framework. Alkane elimination reactions between 2-(CH₃NH)-C₆H₄P(Ph)₂ (HL¹) and Lu(CH₂SiMe₃)₃(THF)₂ at room temperature for 3 h generated mono(alkyl) complex (L¹)₂Lu(CH₂SiMe₃)(THF) (1). Similarly, treatment of 2-(C₆H₅CH₂NH)-C₆H₄P(Ph)₂ (HL²) with Lu(CH₂SiMe₃)₃(THF)₂ afforded (L²)₂Lu(CH₂SiMe₃)(THF) (2), selectively, which gradually deproportionated to a homoleptic complex (L²)₃Lu (3) at room temperature within a week. Strikingly, under the same condition, 2-(2,6-Me₂C₆H₃NH)-C₆H₄P(Ph)₂ (HL³) swiftly reacted with Ln(CH₂SiMe₃)₃(THF)₂ at room temperature for 3 h to yield the corresponding lanthanide bis(alkyl) complexes L³Ln(CH₂SiMe₃)₂(THF)_n (4a: Ln = Y, n = 2; 4b: Ln = Sc, n = 1; 4c: Ln = Lu, n = 1; 4d: Ln = Yb, n = 1; 4e: Ln = Tm, n = 1) in high yields. All complexes have been well defined and the molecular structures of complexes 1, 2, 3 and 4b-e were confirmed by X-ray diffraction analysis. The scandium bis(alkyl) complex activated by AlEt₃ and [Ph₃C][B(C₆F₅)₄], was able to catalyze the polymerization of ethylene to afford linear polyethylene.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Mechanistic studies on the alcoholysis and aminolysis of [(MeZn)2{μ-N(H)tBu}{μ-N(CH2Py)2}]

The reaction of bis(2-pyridylmethyl)amine (II) with t-butylamine and dimethylzinc gives the heteroleptic [(MeZn)₂{μ-N(H)tBu}{μ-N(CH₂Py)₂}] (1). Stoichiometric alcoholysis of 1 with methanol leads to the exchange of the μ-N(H)tBu moiety. Almost quantitatively the corresponding methoxide [(MeZn)₂(μ-OMe){μ-N(CH₂Py)₂}] (2) is formed. Alternatively bis(alkylzinc)methoxide-bis(2-pyridylmethyl)amides (Alkyl = methyl (2), bis(trimethylsilyl)methyl) (3)) are also accessible by direct zincation of bis(2-pyridylmethyl)amine (II) and methanol with dialkylzinc regardless of the bulkiness of the alkyl groups. Extensive DFT calculations on the alcoholysis mechanism reveal the preferential insertion of methanol into a zinc amide bond rather than the cleavage of zinc carbon bonds. An intermediate with a Zn[μ-(MeO?H?NHR)]Zn functionality is predicted. Aminolyis of 1 with t-butylamine leads to intermediates with Zn[μ-(RNH ? H ? NHR)]Zn functionalities, respectively. We were able to detect the latter by ¹H NMR spectroscopy. The aminolysis of 1 with an excess of phenylamine results in a partial decomposition of the complex leading to the hexanuclear amide [{Zn(μ-N(H)Ph)}{MeZn(μ-N(H)Ph)}₂{μ-N(CH₂Py)₂}]₂ (4). Compound 2 is able to cleave silicon grease when dissolved in t-butylamine yielding [(MeZn)₂{μ-N(CH₂Py)₂}₂Zn{μ-(OMe₂Si)₂O}] (5). The X-ray structures of complexes 1-5 are discussed.     

Backbone modified small bite-angle diphosphines: Synthesis and molecular structures of [M(CO)4{X2PC(RR)PX2}] (M = Mo, W; X = Ph, Cy; R = H, Me, Et, Pr, allyl, R = Me, allyl)

A range of new small bite-angle diphosphine complexes, [M(CO)₄{X₂PC(R¹R²)PX₂}] (M = Mo, W; X = Ph, Cy; R¹ = H, Me, Et, Pr, allyl, R² = Me, allyl), have been prepared via elaboration of the methylene backbones in [M(CO)₄(X₂PCH₂PX₂)] as a result of successive deprotonation and alkyl halide addition. When X = Ph it proved possible to replace both methylene protons but for X = Cy only one substitution proved possible. This is likely due to the electron-releasing nature of the cyclohexyl groups but may also be due to steric constraints. Attempts to prepare the bis(allyl) substituted complex [Mo(CO)₄{Ph₂PC(allyl)₂PPh₂}] were only moderately successful. The crystal structures of nine of these complexes are presented.     

Reactions of 1,2-catechol with Bu3M (M = Ga, In). Structures of intermediate products

Reactions of 1,2-catechol with ^tBu₃M (M = Ga, In) have been studied. Trinuclear compounds [^tBu₅M₃(OC₆H₄O)₂] [M = Ga (1), M = In (2)] were synthesised in the reaction of 2 equiv. of C₆H₄(OH)₂ with 3 equiv. of ^tBu₃M in refluxing solvents. At room temperature the reaction of 1,2-catechol with ^tBu₃In in Et₂O leads to the formation of a binuclear complex [^tBu₄In₂(OC₆H₄OH)₂ · 2Et₂O] (3) possessing a four-membered In₂O₂ core and two unreacted hydroxyl groups. The same reaction carried out in a non-coordinating solvent (CH₂Cl₂) results in formation a compound [^tBu₃In₂(OC₆H₄O)(OC₆H₄OH)] (4), which undergoes a reaction with ^tBu₃In to yield the product 2. Moreover two intermediate isomeric products 5 and 6 of formula [^tBu₃Ga₂(OC₆H₄O)(OC₆H₄OH)] were isolated from the post-reaction mixture of 1,2-catechol with ^tBu₃Ga. The compound 6 possessing a different coordination of gallium atoms than 5 is a result of the intramolecular rearrangement of the compound 5 to decrease the steric repultion between ligands. Compounds 3 and 6 were structurally characterised. According to the structure of intermediate products 3-6 a reaction pathway of 1,2-catechols with group 13 metal trialkyls was proposed.     

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands: Synthesis, characterization and ethylene polymerization

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands, bis((3,5-di-tert-butyl-C₆H₂-2-O)R₁CN (2-R₂-C₆H₄))ZrCl₂ {R₁ = Me, R₂ = H (2a); R₁ = Et, R₂ = H (2b); R₁ = Ph, R₂ = H (2c); R₁ = 2-Me-Ph, R₂ = H (2d); R₁ = 2-F-Ph, R₂ = H (2e); R₁ = 2-Cl-Ph, R₂ = H (2f); R₁ = 2-Br-Ph, R₂ = H (2g); R₁ = Ph, R₂ = Me (2h); R₁ = Ph, R₂ = F (2i)}, have been prepared, characterized and tested as catalyst precursors for ethylene polymerization. Crystal structure analysis reveals that complex 2c has a six coordinate center in a distorted octahedral geometry with trans-O, cis-N, cis-Cl arrangement which possesses approximate C₂ symmetry. When activated with methylaluminoxane (MAO), complexes 2a-2i exhibited high ethylene polymerization activities of 10⁶-10⁸ g PE (mol M h)⁻¹. Compared with the bis(phenoxyimine) zirconium analogues bis((3,5-di-tert-butyl-C₆H₂-2-O)CHNC₆H₅)ZrCl₂ (3), the introduction of substituent on the carbon atom of the imine double bond enhanced the catalytic activity and molecular weight of prepared polyethylene. Especially, when the H atom at the carbon atom of the imine double bond was replaced by 2-fluoro-phenyl with strong electronic-withdrawing property, complex 2e displayed the highest catalytic activity, and the polyethylene obtained possessed the highest molecular weight and melt point.     

Synthesis and structures of some sterically hindered zinc complexes containing 6-membered and rings

Zinc β-diketiminates containing the N,N′-chelating ligand [{N(SiMe₃)C(Ph)}₂CH]⁻ (≡LL⁻) [Zn(LL)(μ-Cl)]₂ (1) and [ZnEt(LL)thf] (2) were prepared from 2ZnCl₂ + [Li(LL)]₂ and ZnEt₂ + H(LL), respectively. The new phenols 2-(N-R-piperazinyl-N′-methyl)-4,6-di-tert-butylphenol [R = Ph (3a), Me (3b)] and 2,2-[μ-N,N′-piperazindiyldimethyl]-bis(4,6-di-tert-butylphenol) (4) were obtained from 2,4-tBu₂C₆H₃OH, (CH₂O)_n and the appropriate piperazine. Zinc phenoxides 5, 7 and 8 were derived from 2ZnEt₂ with 2(3a), 2(3b) and 4, respectively. Controlled methanolysis of 5 furnished the bis(phenoxo)zinc compound Zn[OC₆H₂tBu₂-2,4-{CH₂N(CH₂CH₂)₂NPh}-6]₂ (6). The X-ray structures of the crystalline zinc compounds 1, 2, 5, 6, 7 and 8, are presented; each of 5-8 contains two six-membered rings. The centrosymmetric molecule 1 has a rhomboidal (ZnCl)₂ core with exceptionally different Zn-Cl and Zn-Cl′ bond lengths of 2.248(1) and 2.509(1) Å, respectively. None of 1, 2 or 5-8 was an effective catalyst for the copolymerisation of an oxirane and CO₂.     

Synthesis of a Stable Biphenyl‐Bis(carbene) and ‐Bis(silylene) [M{(NCH2But)2C6H3‐3,4}]2 (M = C or Si)

Treatment of the biphenyl derivative [S=C{(NCH₂Bu^t)₂C₆H₃‐3,4}]₂ or [Cl₂Si{(NCH₂Bu^t)₂C₆H₃‐3,4}]₂ with C₈K afforded the new bis(carbene) 1 or the first bis(silylene) 2 , respectively. The X‐ray structure of 2 is presented.     

Ring-opening polymerization of l-lactide by organotin(IV)alkoxides,R2Sn(OPr)2: Estimation of the activation parameters

The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R₂Sn(OPrⁱ)₂ compounds, where R = Buⁿ and p-XC₆H₄ (X = CF₃, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH^≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol⁻¹. The entropy of activation, ΔS^≠, is consistently large and negative, −50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph₂Sn(OPrⁱ)₂, (p-FC₆H₄)₂Sn(OPrⁱ)₂ and (p-Me₂NC₆H₄)₃SnOPrⁱ are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPrⁱ ligands.     

Preparation and reactivity of iridium(III) hydride complexes with pyrazole and imidazole ligands

Pyrazole IrHCl₂(HRpz)P₂ [P = PPh₃, PⁱPr₃; R = H, 3-Me], bis(pyrazole) [IrHCl(HRpz)₂(PPh₃)₂]BPh₄ and imidazole IrHCl₂(HIm)(PPh₃)₂ derivatives were prepared by allowing the IrHCl₂(PPh₃)₃ complex to react with the appropriate azole in refluxing 1,2-dichloroethane. Nitrile IrHCl₂(CH₃CN)(PPh₃)₂ and 2,2′-bipyridine (bpy) [IrHCl(bpy)(PPh₃)₂]BPh₄ derivatives were also prepared using IrHCl₂(PPh₃)₃ as a precursor. The complexes were characterised spectroscopically (IR and NMR) and a geometry in solution was also established. Protonation with Brønsted acid of pyrazole IrHCl₂(Hpz)(PPh₃)₂ and imidazole IrHCl₂(HIm)(PPh₃)₂ complexes proceeded with the loss of the azole ligands and the formation of the unstable IrHCl₂(PPh₃)₂ derivative. Vinyl IrCl₂{CHC(H)R1}(HRpz)P₂ and IrCl₂{CHC(H)R1}(HIm)P₂ (R1 = Ph, p-tolyl, COOCH₃; P = PPh₃, PⁱPr₃) complexes were prepared by allowing hydride-pyrazole IrHCl₂(HRpz)P₂ and hydride-imidazole IrHCl₂(HIm)P₂ to react with an excess of terminal alkyne in 1,2-dichloroethane. The complexes were characterised spectroscopically and by the X-ray crystal structure determination of the IrCl₂{CHC(H)Ph}(Hpz)(PPh₃)₂ derivative.     

Lanthanide borohydrido complexes for MMA polymerization: syndio‐ vs iso‐ stereocontrol

This paper presents an extensive study of the polymerization of MMA with borohydrido lanthanide complexes for the first time. Catalytic systems are made from a lanthanide derivative bearing zero one, or two bulky ligands: substituted cyclopentadienyl (Cp^*′ = C₅Me₄nPr, Cp⁴ⁱ = C₅HiPr₄, Cp^Ph3 = H₂C₅Ph₃‐1,2,4), and/or diketiminate ([(p‐tol)NN] = [(p‐CH₃C₆H₄)N(CH₃)C]₂CH), in the presence of variable quantities of alkylating agent. With BuLi in apolar medium, highly isotactic polymer (up to 95.6%) is formed. In THF, syndiotactic‐rich PMMA is obtained whatever the nature of the co‐catalyst (BuLi or MgⁿBu₂). The presence of an electron‐withdrawing ligand such as Cp^Ph3 allows high syndioregularity, up to 81.8% at 0 °C, together with the highest conversion. There is quite good concordance between calculated and experimental molecular data in THF. Divalent Cp^*′₂Sm^II(THF) and (Cp^Ph3)₂Sm^II(THF) are active as single‐component initiators; the former affords PMMA 88% syndiotactic at 0 °C. Copyright © 2005 John Wiley & Sons, Ltd.     

Dinuclear nickel (II) complexes bearing two pyrazolylimine ligands: Synthesis characterization, and catalytic properties for vinyl-type polymerization of norbornene

A series of dinickel (II) complexes of bis-2-(C₃HN₂(R₁)₂-3,5)(C(R₂)N(C₆H₃(CH₃)₂-2,6)Ni₂Br₄ (complex 1: R₁ = CH₃, R₂ = Ph; complex 2: R₁ = CH₃, R₂ = 2,4,6-trimethylphenyl; complex 3: R₁ = R₂ = Ph; complex 4: R₁ = Ph, R₂  = 2,4,6-trimethylphenyl) were synthesized and characterized. The solid-state structures of complexes 1, 2 and 3 have been confirmed by X-ray single-crystal analyses to be in the form of a dinuclear and bromine-bridged structure. However, there is an equilibrium that shifts between the monomer and dimmer in toluene based on the characterization of UV-vis spectrophotometry. Activated by methylaluminoxane (MAO), these complexes are capable of catalyzing the polymerization of norbornene with moderate activity up to 6.64 × 10⁵ gPNBE/(molNi·h). The influences of polymerization parameters such as reaction temperature and Al/Ni molar ratio on catalytic activity and molecular weight of the polynorbornene were investigated in detail. The influence of the bulkiness of the substituents on polymerization activity was also studied. The obtained polynorbornenes were characterized by means of ¹H NMR, FTIR and TG techniques. The analyses results of polymers’ structures indicated that the norbornene polymerization is vinyl-type polymerization rather than ROMP.     

How the interplay of different control mechanisms affects the initiator efficiency factor in controlled radical polymerization: An investigation using organometallic Mo-based catalysts

Compound CpMoI₂(iPr₂dad) (iPr₂dad = iPrNCHCHNiPr), obtained by halide exchange from CpMoCl₂(iPr₂dad) and NaI, has been isolated and characterized by EPR spectroscopy, cyclic voltammetry, and X-ray crystallography. Its action as a catalyst in atom transfer radical polymerization (ATRP) and as a spin trap in organometallic radical polymerization (OMRP) of styrene and methyl acrylate (MA) monomers has been investigated and compared with that of the dichloro analogue. Compound CpMoCl₂(iPr₂dad) catalyzes the ATRP of styrene and MA with low efficiency factors f (as low as 0.37 for MA and ethyl 2-chloropropionate as initiator), while it irreversibly traps the corresponding growing radical chains under OMRP conditions. On the other hand, compound CpMoI₂(iPr₂dad) has a greater ATRP catalytic activity than the dichloro analogue and yields f = 1 for MA and ethyl 2-iodopropionate as initiator. Under OMRP conditions, it does not irreversibly trap the growing radical chains. This comparison serves to illustrate the general principle that low initiator efficiency factors, sometimes observed in ATRP, may result from the interplay of the ATRP and OMRP mechanisms, when the latter ones involves an irreversible radical trapping process.     

A study of β-hydride abstraction from alkanediyl homobimetallic complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 4-10, Cp = η-C5H5)

The alkyl-bridged iron(II) complexes [{Cp(CO)₂Fe}₂{μ-(C_nH_2n)}] (n = 6-10, Cp = η⁵-C₅H₅) undergo both single and double hydride abstraction when reacted with one equivalent of Ph₃CPF₆ to give both the monocationic complexes, [{Cp(CO)₂Fe}₂{μ-(C_nH_2n−1)}]PF₆, and the dicationic complexes, [{Cp(CO)₂Fe}₂{μ-(C_nH_2n−2)}](PF₆)₂. The ratios of monocationic to dicationic complexes decrease with the increase in the value of n. The complexes where n = 4 and 5 undergo only single hydride abstraction under similar conditions. When reacted with two equivalents of Ph₃CPF₆, the complexes where n = 6-10 undergo double hydride abstraction to give dicationic complexes only. In contrast, the complex where n = 5 gives equal amounts of the monocationic and the dicationic complexes, while the complex where n = 4 only gives the monocationic complex. ¹H and ¹³C NMR data show that in the monocationic complexes one metal is σ-bonded to the carbenium ion moiety while the other is bonded in a η²-fashion forming a chiral metallacylopropane type structure. In the dicationic complexes both metals are bonded in the η²-fashion. The monocationic complexes where n = 4-6, react with methanol to give η¹-alkenyl complexes[Cp(CO)₂Fe(CH₂)_nCHCH₂] (n = 2-4) as the major products and σ-bonded ether products [{Cp(CO)₂Fe}₂{μ-(CH₂)_nCH(OCH₃)CH₂}] as the minor products. The complex where n = 8 reacted with iso-propanol to give the η¹-alkenyl complex [Cp(CO)₂Fe(CH₂)₆CHCH₂]. The dicationic complexes where n = 5, 8 and 9 were reacted with NaI to give the respective α, ω-dienes and [Cp(CO)₂FeI].     

Styrene polymerization with novel anilido-imino nickel complexes/MAO catalytic system: Catalytic behavior, microstructure of polystyrene and polymerization mechanism

The polymerization of styrene with novel catalytic systems of anilido-imino nickel complexes (Ar¹N = CHC₆H₄NAr²) NiBr (Ar¹ = Ar² = 2,6-dimethylphenyl, 1; Ar¹ = 2,6-dimethylphenyl, Ar² = 2,6-diisopropylphenyl, 2; Ar¹ = Ar² = 2,6-diisopropylphenyl, 3; Ar¹ = 2,6-diisopropylphenyl, Ar² = 2,6-dimethylphenyl, 4) activated by methylaluminoxane was investigated. The influence of reaction parameters (temperature, Al/Ni mole ratio, and polymerization time) on styrene polymerization was evaluated. The influence of the bulkiness of the substituents on polymerization activity and polymer characteristics was also ascertained. The obtained polystyrene was an iso-rich atactic polymer and its weight-average molecular weight reached 70 500. NMR analysis of the end groups further confirmed that styrene polymerization catalyzed by anilido-imino nickel complexes/MAO systems proceeded through a coordination mechanism, and the chain was initiated through styrene secondary insertion into the NiH and terminated mainly through β-H elimination of styrene producing the chain-end group (CHCHPh).     

Coordination and extraction studies of an unexplored bi-functional ligand,carbamoyl methyl pyrazole (CMPz) with uranium(VI), lanthanum(III) and cerium(III) nitrates

The bi-functional carbamoyl methyl pyrazole ligands, C₅H₇N₂CH₂CONBu₂ (L₁), C₅H₇N₂CH₂CONⁱBu₂ (L₂), C₃H₃N₂CH₂CONBu₂ (L₃), C₃H₃N₂CH₂CONⁱBu₂ (L₄) and C₅H₇N₂CH₂CON(C₈H₁₇)₂ (L₅) were synthesized and characterized by spectroscopic and elemental analysis methods. The selected coordination chemistry of L₁ to L₄ with [UO₂(NO₃)₂ · 6H₂O], [La(NO₃)₃ · 6H₂O] and [Ce(NO₃)₃ · 6H₂O] has been evaluated. Structures for the compounds [UO₂(NO₃)₂ C₅H₇N₂CH₂CONBu₂] (6) [UO₂(NO₃)₂ C₅H₇N₂CH₂CONⁱBu₂] (7) and [Ce(NO₃)₃{C₃H₃N₂CH₂CONⁱBu₂}₂] (11) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of the ligand L₅ with U(VI) and Pu(IV) in tracer level showed an appreciable extraction for U(VI) and Pu(IV) up to 10 M HNO₃ but not for Am(III). Thermal studies of the compounds 6 and 7 in air revealed that the ligands can be destroyed completely on incineration.     

Diazaallyls of group 4 metals based on trans-1,2-diaminocyclohexane

Amination of 1-bromo-2-methylpyridine with trans-1,2-diaminocyclohexane gives the corresponding bis(aminopyridine) H₂L¹. Conversion of the same diamine to the N,N′-bis(amino-4,4-dimethylthiazoline) H₂L² is also completed in three steps. The analogous aminooxazoline is however inaccessible, although the aminocyclohexane analogue is prepared readily. The proligand H₂L¹ forms bis(aminopyridinato) alkyl complexes of the type [ZrL¹R₂] (R = CH₂Ph, CH₂Bu^t). The molecular structure of the neopentyl complex shows that the chiral backbone leads to a puckering of the N₄Zr coordination sphere, which contrasts with the related cyclohexyl-bridged Schiff-base complexes which are essentially planar. [ZrL²(CH₂Bu^t)₂] - the first aminothiazolinato complex - is formed similarly. A comparison of the structures of [ZrL¹(CH₂Bu^t)₂] and [ZrL²(CH₂Bu^t)₂] indicates that the latter has a fully delocalised N-C-N system, rather similar to a bis(amidinate). Reaction of H₂L² with [Ti(NMe₂)₄] gives [TiL²(NMe₂)₂] which appears to be C₂-symmetric like the above complexes according to NMR spectra, but has one uncoordinated thiazoline unit in the solid state. This is a result of increased ring strain at the smaller titanium metal centre.     

The Monomerization of a Binuclear Molybdenum(VI) Dioxo Complex by an Unusual Silylation Reaction

The formation of a mononuclear molybdenum(VI) complex [MoO₂{O(CH₂)₂S(CH₂)₂OH}(OSiBu^tPh₂)] ( 2 ) derived from its binuclear precursor [MoO₂{O(CH₂)₂S(CH₂)₂O}]₂ ( 1 ) by a silylation reaction accompanied by the conversion of methanol to chloromethane is reported.