四个基于间苯二(取代水杨醛酰腙)的有机锡配合物的溶剂热合成、结构和荧光性能

采用间苯二（取代水杨醛酰腙）（H₄L）与R₃²SnOH溶剂热反应,或间苯二甲酰肼、3-叔丁基水杨醛和三环己基氢氧化锡一锅溶剂热法反应,合成了4个新的有机锡配合物（SnR²）₂L（1~4）,其中,H₄L=m-Ph（CONH—N=CH（o-OH） PhR¹）₂;R¹=NEt₂,R²=Ph（1）;R¹=3,5-di-tert-butyl=3,5-t-2Bu,R²=Ph（2）;R¹=3,5-t-2Bu,R²=Cy（3）;R¹=3-tert-butyl=3-t-Bu,R²=Cy（4）。经元素分析、红外光谱和（¹H、¹³C、¹¹9Sn）核磁共振谱表征,并用X射线衍射方法确证配合物1~4的结构。配体H₄L的2个取代水杨醛酰腙链向内取向并与锡原子配位形成3个内向E型配合物1~3,取代水杨醛酰腙链向外取向并与锡原子配位形成外向E型配合物4。配合物1、2和4属于三斜晶系P1空间群,配合物3属于单斜晶系P2₁/c空间群。中心锡与配位原子构成畸形双角三锥构型。配体、配合物-三氯甲烷溶液的荧光性能表明,当具有弱荧光的配体m-Ph（CONH—N=CH（o-OH） PhNEt₂）₂（H₄L¹）和无荧光的配体m-Ph（CONH—N=CH（o-OH） Ph（3,5-t-2Bu））₂（H₄L²）分别与苯基锡、环己基锡配位后,配合物-三氯甲烷溶液发出强荧光。     

Elementorganische Amin/Imin-Verbindungen,XXXI. Cyclometallierung bei N-tert-Butyl-Phosphor-Stickstoff-Iridiumkomplexen

Element-Organic Amine/Imine Compounds, XXXI. - Cyclometallation with N-tert-Butyl-Phosphorus-Nitrogen Iridium Complexes The interaction of R¹R²N–PNR³ ( 1 ) (R¹  SiMe₃, tBu, iC₃H₇; R²  R³  SiMe₃, tBu) with [M(COD)(μ-Cl)]₂ ( 2 ), M  Rh, Ir, affords the amino(imino)phosphane complexes 3 , whose PN bond adds methanol with formation of the diamidophosphite complexes 4 . Already below 0°C the iridium compounds of 4 undergo cyclometallation of a tBu methyl group (R²) with formation of the hydrido-iridium metallaheterocycles 5 . The structures of 4b and 5a are elucidated by X-ray analyses.     

A Comparative Study on the Thermodynamics of Halogen Bonding of Group 10 Pincer Fluoride Complexes

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R₂-^tBuPOCOP^tBu)MF] (3,5-R₂-^tBuPOCOP^tBu=κ³-C₆HR₂-2,6-(OPtBu₂)₂ with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs.     

Addition of iodine-based electrophilic reagents to some vinylsilanes

The addition of some Iodine-based electrophillic reagents to the cyclic vinylsilanes (1) and (4,R=Bu^t,R¹=H) and (4,R=H,R¹-OMe) occurs with high regio-and stereo-specificity to give (2,X=OMe,N₃, and NCS) and (5,R=Bu^t,R¹=H,X=OMe and N₃) and (5, R=H,R¹-OMe,X-OMe). Similar additions to 2-trimethylsilylhept-1-ene (6) are less efficient and occur with lower regioselectivity. Some of the adducts (2) and (5) have been transformed into functionalised organosilanes. Compounds (10,X=OMe,N₃, and NCS) and (12)–(15) are thereby obtained.     

DFT/TDDFT studies of the ancillary ligand effects on structures and photophysical properties of rhenium (I) tricarbonyl complexes with the imidazo[4,5‐f]‐1,10‐phenanthroline ligand

The seven rhenium (I) tricarbonyl complexes having a general formula fac‐[ReBr(CO)₃(R₁,R₂,R₃‐N^{^}N)] (N^{^}N = imidazo[4,5‐f]‐1,10‐phenanthroline; R₁ = ? ^tBu, R₂ = R₃ = ? H, 1 ; R₁ = ? C?CH, R₂ = R₃ = ? H, 2 ; R₁ = ? ^tBu, R₂ = ? C?CH, R₃ = ? H, 3 ; R₁ = ? ^tBu, R₂ = R₃ = ? C?CH, 4 ; R₁ = ? ^tBu, R₂ = ? CH₃, R₃ = ? H, 5 ; R₁ = ? ^tBu, R₂ = R₃ = ? CH₃, 6 ; R₁ = ? ^tBu, R₂ = ? OCH₃, R₃ = ? H, 7 ) have been investigated theoretically by density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods. The different substituted groups on N^{^}N ligand induce changes on the electronic structures and photophysical properties for these complexes. It is found that the introduction of ? C?C decreases the energy level of lowest unoccupied molecular orbital (LUMO) while the introduction of ? CH₃ or ? OCH₃ lead to increase the energy level of LUMO. The order of LUMO energy level rising is in line with the increasing of donating abilities of substituted groups; and the influence of R₂ position is greater than that of R₁ position on LUMO energy level. The lowest energy absorption bands have changes in the order of 7 < 6 < 5 < 1 < 2 < 3 < 4 . These results of electronic affinity (EA), ionization potential (IP), and reorganization energy (λ) indicate that all of these complexes can be used as electron transporting materials. Moreover, the smallest difference between λ_electron and λ_hole of 4 indicates that it is better to be used as an emitter in the organic light‐emitting diodes. © 2015 Wiley Periodicals, Inc.     

Distibanes and Distibenes from Reduction of Sb(NONR)Cl by using MgI Reagents

The bis(amidodimethyl)disiloxane antimony chlorides Sb(NON^R)Cl (NON^R=[O(SiMe₂NR)₂]²⁻; R=tBu, Ph, 2,6-Me₂C₆H₃=Dmp, 2,6-iPr₂C₆H₃=Dipp, 2,6-(CHPh₂)₂-4-tBuC₆H₂=tBu-Bhp) are reduced to Sb^II and Sb^I species by using Mg^I reagents, [Mg(BDI^R′)]₂ (BDI=[HC{C(Me)NR′}₂]⁻; R′=2,4,6-Me₃C₆H₂=Mes, Dipp). Stoichiometric reactions with Sb(NON^R)Cl (R=tBu, Ph) form dimeric Sb^II stibanes [Sb(NON^R)]₂, shown crystallographically to contain Sb−Sb single bonds. The analogous distibane with R=Dmp substituents has an exceptionally long Sb−Sb interaction and exhibits spectroscopic and reactivity properties consistent with radical character in solution. When R=Dipp, reductions with Mg^I reagents directly give distibenes [Sb(μ-NON^Dipp)Mg(BDI^R′)(THF)_n]₂ (R′=Mes, n=1; R′=Dipp, n=0). Crystallographic analysis shows a trans-substitution of the Sb=Sb double bond, with bridging NON^Dipp-ligands between the Sb^I and Mg^II centres. An attempt to access the NON^Ph-analogue using the same protocol afforded the polystibide cluster Sb₈[μ₄,η^2:2:2:2-Mg(BDI^Mes)]₄, which co-crystallized with the ligand transfer product, [Mg(BDI^Mes)]₂(μ-NON^Ph).     

Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations

Molybdenum(VI) bis(imido) complexes [Mo(NtBu)₂(L^R)₂] (R=H 1 a ; R=CF₃ 1 b ) combined with B(C₆F₅)₃ ( 1 a /B(C₆F₅)₃, 1 b /B(C₆F₅)₃) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H₂ and Et₃SiH affords ion pairs [Mo(NtBu)(NHtBu)(L^R)₂][HB(C₆F₅)₃] (R=H 2 a ; R=CF₃ 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H₂O leads to [Mo(NtBu)(NHtBu)(L^R)₂][(HO)B(C₆F₅)₃] (R=H 3 a ; R=CF₃ 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C₆F₅)₃]⁻. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(L^R)₂][{PhCH₂O}B(C₆F₅)₃] (R=H 4 a ; R=CF₃ 4 b ). Catalysis occurs at [HB(C₆F₅)₃]⁻ while [Mo(NtBu)(NHtBu)(L^R)₂]⁺ (R=H or CF₃) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).     

Synthesis and Crystal Structures of t‐Butyl‐Pyridine Adducts of ZnR2 (R = Me,i‐Pr,t‐Bu,Cp*)

Lewis acid‐base adducts of the general type R₂Zn(4‐tBuPy)_x (R = Me 1 , iPr 2 , tBu 3 , Cp* 4 ; x = 1, 2) were obtained in high yields from reactions of ZnR₂ with the Lewis base 4‐tBu‐Pyridine. Compounds 1 – 4 were characterized by multinuclear NMR (¹H, ¹³C) and IR spectroscopy and elemental analyses, 1 and 4 also by X‐ray diffraction at single crystals.     

Gold Sulfonium Benzylide Complexes Undergo Efficient Benzylidene Transfer to Alkenes

The gold sulfonium benzylide complexes [( P1 )AuCHPh(SR¹R²)]⁺ {B[3,5-CF₃C₆H₃]₄}⁻ [ P1 =P(tBu)₂o-biphenyl; R¹, R²=-(CH₂)₄- ( 1 a ); R¹=Et, R²=Ph ( 1 b ); R¹=R²=Ph ( 1 c )] were synthesized by reaction of the gold α-chloro benzyl complex ( P1 )AuCHClPh with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and excess sulfide. Complexes 1 undergo efficient benzylidene transfer to alkenes and DMSO under mild conditions without external activation. Kinetic analysis of the reaction of 1 c with styrene was consistent with the intermediacy of the cationic gold benzylidene complex [( P1 )AuCHPh]⁺ ( I ).     

Tuning a Single Ligand System to Stabilize Multiple Spin States of Manganese: A First Example of a Hydrazone‐Based Manganese(III) Spin‐Crossover Complex

A series of bis‐chelate pseudo‐octahedral mononuclear coordination complexes of manganese with the chromophore [MnN₄O₂]ⁿ⁺ (n=0, 1) have been generated in all three principal oxidation states of this transition‐metal center under ambient conditions by utilizing a readily tunable, versatile phenolic pyridylhydrazone ligand system (i.e., H₂(3,5‐R¹,R²)‐L; L=ligand). Strategic combinations of the nature and position of a variety of substituent groups afforded selective, spontaneous stabilization of multiple spin states of the manganese center, which, upon close crystallographic scrutiny, appears to be in part due to the occurrence or absence of hydrogen‐bonding interactions that involve the phenolate/phenolic oxygen atom. The divalent complexes are isolable in two forms, namely, molecular [Mn^II{H(3,5‐R¹,R²)‐L}₂] and ionic [Mn^II{H₂(3,5‐R¹,R²)‐L}{H(3,5‐R¹,R²)‐L}]ClO₄, with the latter complex converting easily into the former complex on deprotonation. Accessibility of the higher‐valent states is achievable only when the phenolate oxygen atom is sterically hindered from participation in hydrogen bonding. The [Mn^III{H(3,5‐tBu₂)‐L}₂]ClO₄ complex is the first example of a hydrazone‐based Mn^III complex to exhibit spin crossover. Formation of the tetravalent complexes [Mn^IV{(3,5‐R¹,R²)‐L}₂] (R¹=tBu, R²=H; R¹=R²=tBu) necessitates base‐assisted abstraction of the hydrazinic proton.     

Zincocene and Dizincocene N‐Heterocyclic Carbene Complexes and Catalytic Hydrogenation of Imines and Ketones

The N‐heterocyclic carbene (NHC) adducts Zn(Cp^R)₂(NHC)] (Cp^R=C₅HMe₄, C₅H₄SiMe₃; NHC=ItBu, IDipp (Dipp=2,6‐diisopropylphenyl), IMes (Mes=mesityl), SIMes) were prepared and shown to be active catalysts for the hydrogenation of imines, whereas decamethylzincocene [ZnCp*₂] is highly active for the hydrogenation of ketones in the presence of noncoordinating NHCs. The abnormal carbene complex [Zn(OCHPh₂)₂(aItBu)]₂ was formed from spontaneous rearrangement of the ItBu ligand during incomplete hydrogenation of benzophenone. Two isolated Zn^I adducts [Zn₂Cp*₂(NHC)] (NHC=ItBu, SIMes) are presented and characterized as weak adducts on the basis of ¹³C NMR spectroscopic and X‐ray diffraction experiments. A mechanistic proposal for the reduction of [ZnCp*₂] with H₂ to give [Zn₂Cp*₂] is discussed.     

Synthesis of a “Masked” Terminal Nickel(II) Sulfide by Reductive Deprotection and its Reaction with Nitrous Oxide

The addition of 1 equiv of KSCPh₃ to [L^RNiCl] (L^R={(2,6‐iPr₂C₆H₃)NC(R)}₂CH; R=Me, tBu) in C₆H₆ results in the formation of [L^RNi(SCPh₃)] ( 1 : R=Me; 2 : R=tBu) in good yields. Subsequent reduction of 1 and 2 with 2 equiv of KC₈ in cold (?25 °C) Et₂O in the presence of 2 equiv of 18‐crown‐6 results in the formation of “masked” terminal Ni^II sulfides, [K(18‐crown‐6)][L^RNi(S)] ( 3 : R=Me; 4 : R=tBu), also in good yields. An X‐ray crystallographic analysis of these complexes suggests that they feature partial multiple‐bond character in their Ni? S linkages. Addition of N₂O to a toluene solution of 4 provides [K(18‐crown‐6)][L^tBuNi(SN?NO)], which features the first example of a thiohyponitrite (κ²‐[SN?NO]^2?) ligand.     

Diversification of ortho‐Fused Cycloocta‐2,5‐dien‐1‐one Cores and Eight‐ to Six‐Ring Conversion by σ Bond C−C Cleavage

Sequential treatment of 2‐C₆H₄Br(CHO) with LiC≡CR¹ (R¹=SiMe₃, tBu), nBuLi, CuBr?SMe₂ and HC≡CCHClR² [R²=Ph, 4‐CF₃Ph, 3‐CNPh, 4‐(MeO₂C)Ph] at ?50 °C leads to formation of an intermediate carbanion (Z)‐1,2‐C₆H₄{C_A(=O)C≡C_BR¹}{CH=CH(CH^?)R²} ( 4 ). Low temperatures (?50 °C) favour attack at C_B leading to kinetic formation of 6,8‐bicycles containing non‐classical C‐carbanion enolates ( 5 ). Higher temperatures (?10 °C to ambient) and electron‐deficient R² favour retro σ‐bond C?C cleavage regenerating 4 , which subsequently closes on C_A providing 6,6‐bicyclic alkoxides ( 6 ). Computational modelling (CBS‐QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H⁺ gave 1,2‐dihydronaphthalen‐1‐ols, or under dehydrating conditions, 2‐aryl‐1‐alkynylnaphthlenes. Enolates 5 react in situ with: H₂O, D₂O, I₂, allylbromide, S₂Me₂, CO₂ and lead to the expected C ‐E derivatives (E=H, D, I, allyl, SMe, CO₂H) in 49–64 % yield directly from intermediate 5 . The parents (E=H; R¹=SiMe₃, tBu; R²=Ph) are versatile starting materials for NaBH₄ and Grignard C=O additions, desilylation (when R¹=SiMe) and oxime formation. The latter allows formation of 6,9‐bicyclics via Beckmann rearrangement. The 6,8‐ring iodides are suitable Suzuki precursors for Pd‐catalysed C?C coupling (81–87 %), whereas the carboxylic acids readily form amides under T3P® conditions (71–95 %).     

Transition-metal complexes of phenoxy-imine ligands modified with pendant imidazolium salts: Synthesis, characterisation and testing as ethylene polymerisation catalysts

Reaction between 3-((1R,2R)-2-{[1-(3,5-di-tert-butyl-2-hydroxy-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1a) or the derivative 3-((1R,2R)-2-{[1-(2-hydroxy-5-nitro-phenyl)-meth-(E)-ylidene]-amino}-cyclohexyl)-1-isopropyl-4-phenyl-3H-imidazol-1-ium bromide (1b) and metal halides MCl_x.yTHF (M = Zr, x = 4, y = 2; M = V, x = y = 3; M = Cr, x = y = 3), in THF, at −78 °C gives the metal complexes of general formula [MCl_x(κ²-N,O-OC₆H₂R¹R²C(H)N-C₆H₁₀-Im)₂][Br]₂ (where M = Zr, x = 2, R¹ = R² = ^tBu, 2; M = Zr, x = 2, R¹ = H, R² = NO₂, 3; M = V, x = 1, R¹ = R² = ^tBu, 4; M = Cr, x = 1, R¹ = R² = ^tBu, 5; M = Fe, x = 0, R¹ = R² = ^tBu, 6; Im = 1-isopropyl-4-phenyl-3H-imidazol-1-ium-3-yl). ¹H and ¹³C NMR spectroscopy of 2 and 3 indicate κ²-N,O-ligand coordination via the phenoxy-imine moiety with pendant imidazolium salt that is corroborated by a single crystal structure of 6. Compounds 2, 3, 4 and 5 were tested as precatalysts for ethylene polymerisation in the presence of methylaluminoxane (MAO) cocatalyst, showing low activity. Selected polymer samples were characterised by GPC showing multimodal molecular weight distributions.     

Self-assembly of 1D Coordination Polymers Containing Copper(I) <Emphasis Type="Italic">tert</Emphasis>-butylthiolato Clusters: Structural Characterization and Properties

Abstract  The solvothermal reactions of copper(I) tert-butylthiolate (CuS ^t Bu) with 1/3 equiv. of dppe [dppe = bis(diphenylphosphino)ethane] or bix [bix = 1,4-bis(imidalzole-1-ylmethyl)benzene] in CH₃CN led to the formation of two cluster-based coordination polymers [(CuS ^t Bu)₄(dppe)] _n (1) and [(CuS ^t Bu)₆(bix)] _n (2). Single-crystal X-ray diffraction studies reveal that 1 and 2 feature 1D zigzag polymeric chains which contain rare (CuS ^t Bu)₄ or (CuS ^t Bu)₆ clusters as connecting junctions and dppe or bix as linkers. The title compounds show optical transitions with band gaps of ∼3.18 eV for 1 and ∼2.81 eV for 2. Compounds 1 and 2 exhibit strong photoluminescence with the peaks maximum at 603 and 629 nm respectively. Graphical Abstract  Two 1D zigzag polymers [(CuS ^t Bu)₄(dppe)] _n (1) and [(CuS ^t Bu)₆(bix)] _n (2) [dppe = bis(diphenylphosphino) ethane] or bix [bix = 1,4-bis(imidalzole-1-ylmethyl)benzene] have been synthesized by solvothermal reactions using copper(I) tert-butylthiolate CuS ^t Bu as the starting material. Compounds 1 and 2 contain rare (CuS ^t Bu)₄ and (CuS ^t Bu)₆ clusters as connecting nodes and dppe or bix as bridging ligands. The title compounds show optical transitions with band gaps of ∼3.18 eV for 1 and ∼2.81 eV for 2. Both 1 and 2 exhibit strong photoluminescence with the peak maximums at 603 and 629 nm, respectively. The 1D zigzag polymer of [(CuS ^t Bu)₆(bix)] _n (2).     

From bis(silylamino)tin dichlorides via di(1-alkynyl)-bis(silylamino)tin to new heterocycles by 1,1-organoboration

Bis(silylamino)tin dichlorides 1 [X₂SnCl₂ with X=N(Me₃Si)₂ (a), N(9-BBN)SiMe₃ (b), N(^tBu)SiMe₃ (c), and N(SiMe₂CH₂)₂ (d)] were prepared from the reaction of two equivalents of the respective lithium amides (Li-a-d) with tin tetrachloride, SnCl₄, or from the 1:1 reaction of the respective bis(amino)stannylene with SnCl₄. The compounds 1 react with two equivalents of lithium alkynides LiCCR¹ to give the di(1-alkynyl)-bis(silylamino)tin compounds X₂Sn(CCR¹)₂, 2 (R¹=Me), 3 (R¹=^tBu), and 4 (R¹=SiMe₃). Problems were encountered, mainly with LiCC^tBu as well as with 1b, since side reactions also led to the formation of 1-alkynyl-bis(silylamino)tin chlorides 5-7 and tri(1-alkynyl)(silylamino)tin compounds 8 and 9. 1,1-Ethylboration of compounds 2-4 led to stannoles 10, 11, and in the case of propynides, also to 1,4-stannabora-2,5-cyclohexadiene derivatives 12. The molecular structure of the stannole 11b (R¹=SiMe₃) was determined by X-ray analysis. The reaction of 2a and d with triallylborane afforded novel heterocycles, the 1,3-stannabora-2-ethylidene-4-cyclopentenes 14. These reactions proceed via intermolecular 1,1-allylboration, followed by an intramolecular 1,2-allylboration to give 14, and a second intramolecular 1,2-allylboration leads to the bicyclic compounds 15.     

Simplified Approach to the Regiospecific Synthesis of Trichloromethylpyrazolines Using Microwave Irradiation

Twelve novel 3-alkyl[aryl]-1-carboxamides-5-trichloromethyl-5-hydroxy-4,5-dihydro-lH-pyrazole have been synthesized in good yields (72–90%) using environmentally benign microwave-induced techniques. The compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alkyl[aryl]-2-ones [Cl₃CC(O)C(R²) = C(R¹)OR, where R = Me, Et; R¹ = H, Me, Et, Pr, i-Pr, i-Bu, t-Bu, Ph, Ph-4-NO₂, Ph-4-F, Ph-4-Cl, Ph-4-Br; and R² = H, Me] with semicarbazide hydrochloride in the presence of pyridine and using methanol/water (3:1 v/v) as the solvent. The advantages of using microwave irradiation, rather than a conventional method, were demonstrated.     

Zur Reaktion von tert-Butyl-phosphaalkin mit Molybdänkomplexen

Reaction of tert -Butyl-phosphaalkyne with Molybdenum Complexes The reaction of tBuC≡P with [(CH₃CN)₃Mo(CO)₃] leads to the complex [Mo(CO)₄〈Mo(CO)₂(η⁴-P₃CtBu){η⁴-P₂(CtBu)₂}〉] 1 as well as to the alkyne complexes [Mo(CO)₄〈{P₃(CtBu)₂}{Mo(CO)₂(CtBu)}{η³-P₂(CtBu)₂}〉] 2 and [Mo(CtBu){η⁴-P₂(CtBu)₂(CO)}{η⁵-P₃(CtBu)₂}] 3 . All compounds are characterized by X-ray structural analysis, by NMR- and IR spectroscopy and by mass spectrometry. In complex 1 a 1,3-diphosphacyclobutadiene and a 1,2,4-triphosphacyclobutadiene are connected by two molybdenum carbonyl centres. In 2 a 1,3-diphosphacyclobutadiene is π- and a novel 1,2,4-triphospholyl ligand is σ-bonded at two Mo centres. A characteristic feature of 3 besides a π co-ordinated 1,2,4-triphospholyl ligand is a 3,4-diphosphacyclopentadienone as ligand, formed via CO insertion during the cyclodimerisation of two phosphaalkynes.     

Titanium complexes bearing amine bis(phenolate) ligands: Synthesis,structure and catalysis in ring‐opening polymerization of lactide

Monomeric bis(isopropoxy) titanium complexes LTi(Oⁱ Pr)₂ (L =  ─ OC₆H₂–4‐R¹–6‐R²–2‐CH₂N[(CH₂)₂N(R³)₂]CH₂–4‐R⁴–6‐R⁵‐C₆H₂O ─ , R¹ = R² = ^t Bu, R³ = Et, R⁴ = R⁵ = Cl, (L¹)Ti(Oⁱ Pr)₂; R¹ = R² = Me, R³ = Et, R⁴ = R⁵ = Me, (L²)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Et, R⁴ = OMe, R⁵ = ^t Bu, (L³)Ti(Oⁱ Pr)₂; R¹ = R⁴ = OMe, R³ = Et, R² = R⁵ = ^t Bu, (L⁴)Ti(Oⁱ Pr)₂; R¹ = R² = ^t Bu, R³ = Me, R⁴ = OMe, R⁵ = ^t Bu, (L⁵)Ti(Oⁱ Pr)₂) supported by amine bis(phenolate) ligands were synthesized and characterized using NMR spectroscopy and elemental analysis. The solid‐state structure of (L³)Ti(Oⁱ Pr)₂ was determined using single‐crystal X‐ray diffraction. (L^1–5)Ti(Oⁱ Pr)₂ were all found to initiate the ring‐opening polymerization of l ‐lactide and rac ‐lactide in a controlled manner at 110–160°C. As shown by kinetic studies, (L¹)Ti(Oⁱ Pr)₂ polymerized l ‐lactide faster than did (L^2–5)Ti(Oⁱ Pr)₂. In addition, good number‐average molecular weight and narrow polydispersity index (1.00–1.71) of polymers were also obtained. The microstructure of the polymers and a possible mechanism of coordination–insertion of polymerization were evidenced by MALDI‐TOF and ¹H NMR spectra of the polylactides.     

Formation and Dissociation of Tetrahedral Nickel(II) and Cobalt(II) Complexes of ‘Dithioimidodiphosphato’ Ligands,Measurement of Kinetically Determined Stability Constants,and Kinetic Investigations of the Rapid Formation of Tetrahedral Bis(ligand)copper(II) Complexes and Their Rates of Reduction to Trinuclear Copper(I) Species

The stopped‐flow technique was used to measure the rates of formation and dissociation of tetrahedral [ML₂] complexes (M²⁺=Ni²⁺ or Co²⁺) of four bidentate S₂‐donor ‘dithioimidodiphosphato’ ligands L^? (HL=[R¹R²P(?S)]NH[P(?S)R³R⁴], R¹ to R⁴=alkyl) at 25.0° in MeOH/H₂O 95 : 5 (v/v) solution and in the presence of either MOPS (=3‐(morpholin‐4‐yl)propane‐1‐sulfonic acid) or 2,6‐lutidine (=2,6‐dimethylpyridine) buffers. The kinetically determined equilibrium formation constants for [ML]⁺ ions (M=Ni or Co) are 10^?5 K=0.50±0.01 or 1.64±0.07 l mol^?1 for L=L³ (R¹=R²=Me(CH₂)₂CH(Me), R³=R⁴=Me₂CH), 1.27±0.02 or 7.93±0.09 l mol^?1 for L=L⁷ (R¹ to R⁴=Me₂CHCH₂), 0.88±0.04 or 3.84±0.13 l mol^?1 for L=L⁸ (R¹ to R⁴=Me₂CH), and in case of Ni²⁺ 1.88±0.04 l mol^?1 for L=L⁶ (R¹=R³=Bu, R²=R⁴=^tBu) (see Table 3; for L³ and L⁶–L⁸, see Table 1). Whereas the tetrahedral Ni²⁺ complexes dissociate more slowly than the analogous Co²⁺ species, in all cases, the Co²⁺ complexes are more stable than those of Ni²⁺ due to their larger formation rate constants (Table 3). Reactions of Cu²⁺ with eight ligands HL (R¹ to R⁴=alkyl, alkoxy, aryl, and aryloxy) show that formation of intensely colored tetrahedral [Cu^IIL₂] species is too fast be measured with the available stopped‐flow apparatus (t_1/2<2 ms), but the subsequent rates of reduction of [Cu^IIL₂] to give trinuclear products [Cu^I₃L₃] are measurable. An X‐ray analysis establishes the structure of one of the [Cu₃L₃] complexes, where R¹=R²=Me₂CHO and R³=R⁴=2‐(tert‐butyl)phenyl (L=L⁵), and a multiwavelength stopped‐flow kinetic experiment establishes the spectrum of a tetrahedral [Cu^IIL₂] species prior to the reduction reactions. The redox reactions proceed at 25.0° with first‐order rate constants in the range 0.285 s^?1 (R¹ to R⁴=PhO; L=L¹¹) to 2.58?10^?4 s^?1 (R¹ to R⁴=Me₂CHCH₂; L=L⁷) (Table 4).