Regioselective addition of chalcogenol to an η-propargyl/allenyl complex via formation of the carbon-chalcogen bond leading to new chalcogenoxyallyl species

Regioselective addition of chalcogenol to an ν³-propargyl complex Pt(PPh₃)₂(η³-C₃H₃)](BF₄) (2) via the formation of the C---O, C---S, or C---Se bond generates new cationic chalcogenoxyallyl species {Pt(PPh₃)₂[η³CH₂C(ER)CH₂]}(BF₄) (E = O, R = Me 4(a), Et (4b, ⁱPr (4c), ¹Bu (4d), Ph (4e); E=S, E=Et (5b), ^tBu (5d, Ph (5e); E=Se, R=Ph (6e )) respectively in good yields. Thiol and selenol react with complex 2 much faster than alcohol; and 2 reacts with p-(HO)C₆H₄(SH) to exclusively yield the thioxyallyl product {Pt(PPh₃)₂[η³-CH₂C(SC₆H₄OH)CH₂]}(BF₄) (5f). Among the alcoh and phenol, thereactivity follows the order MeOH > EtOH >, ⁱPrOH >, ^tBuOH > PhOH. A mechanism comprising a preceding coordination step is postulated. The X-ray structures of 4b, 4e, 5b, 5e and 6e are provided.     

New phosphabenzenes by [4 + 2] cycloaddition of stannoles to 1-phospha-1-alkynes — determination of signs of coupling constants [J(P, C), J(P, H), J(P, Si), J(Sn, P)]

Stannoles bearing dialkylboryl groups in 3-position react with 1-phospha-1-alkynes P≡C---^tBu (1) and P≡C---CH₂^tBu (2) by [4 + 2] cycloaddition and elimination of stannylene to give phosphabenzenes in high yield. The stannylenes oligomerise to give [R¹₂Sn]_n with n ≥ 7 (R --- Me, Et, -(CH₂)₅₋ or, in the case of R¹ = ^tBu, react with the stannole itself. All phosphabenzenes are characterized by their consistent sets of NMR data. The absolute signs of the coupling constants ⁿJ(³¹P, ¹H), ⁿJ(³¹P, ¹³C), ²J(³¹P, ²⁹Si) and ²J(¹¹⁹Sn, ³¹P) were determined by appropriate ID and 2D NMR experiments.     

Preparation, spectroscopic properties and thermal stabilities of organomercury compounds containing the bulky ligand (Me3Si)3C or (PhMe2Si)3C

Mercury compounds of the types HgR¹R (R¹ = C(SiMe₃)₃; R = Me, ⁱPr, Bu, ^tBu or Ph) and HgR²R(R² = C(SiMe₂Ph)₃; R = Me, Bu, CH₂Ph or Ph) have been prepared. Those containing R¹ were made by reactions of the bromides HgR¹Br with the Grignard reagents MgRX, and those containing R² by reaction of HgR²Cl with LiR or, for R = CH₂Ph, with Mg(CH₂Ph)Cl. Replacement of one R group in HgR₂ by the bulky R¹ or R² group leads to a large increase in thermal stability, a marked shift in the ¹⁹⁹Hg resonance to lower frequency and an increase in the coupling constant ¹J(¹³C---¹⁹⁹Hg) for the Hg---R bond. The compound HgR²Cl does not react further with LiR² in tetrahydrofuran, but with LiR¹ gives HgR¹R²; the arrangement of the SiMe₂Ph groups in the latter in solution in CH₂C12 at low temperature appears to be different from that in the solid.     

Siliciumverbindungen mit starken intramolekularen sterischen wechselwirkungen : XLIX. Disilane und ein disilen mit unsymmetrischer substitution an den siliciumatomen

Treatment of chlorobis(2,4,6-triisopropylphenyl)silane (Ar₂SiHCl) with lithium naphthalenide and subsequent addition of the chlorosilanes R₂SiHCl (R = ⁱPr, ^tBu, Mes) gives the unsymmetrical disilanes R₂HSiSiHAr₂ which are smoothly converted into the 1,2-dichlorodisilanes 8–10. The X-ray structure analysis of the 1,1-dimesityldisilane 10 reveals a staggered conformation with the chlorine atoms disposed in an anti orientation. Whilst the reductive chloride elimination from the 1,1-dialkyldichlorodisilanes 8 and 9 did not give the corresponding disilenes, the same reaction of 10 provided bright yellow crystals of 1,1-dimesityl-2,2-bis(2,4,6-triisopropylphenyl)disilene, the structure of which was confirmed by a complete NMR study.     

Synthesis and electrochemical behaviour of the cyanamide-isocyanide complexes of rhenium, trans-[ReL(CNR)(Ph2PCH2CH2PPh2)2] ( L = NCNH2 or NCNH)

Reaction of trans-[ReCl(CNR)(dppe)₂] (R = Me (Ia) or ^tBu (Ib); DPPE = Ph₂PCH₂CH₂PPh₂) in CH₂Cl₂ with cynamide in the presence of TlBF₄ forms the new cynamide-isocyanide complexes trans-[Re(CNR)(NCNH₂)(dppe)₂][BF₄] (R = Me (IIa) or ^tBu (IIb)), which upon treatment by ^tBuOK or Et₃N give trans-[Re(NCNH)(CNR)(dppe)₂] (R = Me (IIIa) or ^tBu (IIIb)). The electrochemical behaviour of these species was studied by cyclic voltammetry and controlled potential electrolysis at a Pt electrode in an aprotic solvent, and cathodic reduction of II results in the formation of III.     

New Half-sandwich Zirconium（IV） Complexes Containing Salicylaldimine Ligands： Synthesis,Characterizations and Catalytic Properties

Two new half-sandwich zirconium（IV） complexes bearing salicylaldimine ligands of the type Cp＊Zr[2-tBu-4-R-6-（CH=NiPr）C6H2O]C12[R=H（1）, tBu（2）] were prepared by the reaction of Cp＊ZrC13 with the corresponding lithium of salicylaldimine ligands 2-tBu-4-R-6-（CH=NiPr）C6H2OLi[R=H（LiLa）, tBu（LiLb）]. Com- plexes 1 and 2 were characterized by 1H NMR, BC NMR spectroscopy and elemental analysis. When activated with AliBu3 and Ph3CB（C6F5）4, both complexes 1 and 2 exhibited reasonable catalytic activities for ethylene polymeriza- tion, producing polyethylenes with moderate molecular weight. Complexes 1 and 2 also exhibited reasonable catalyt- ic activities for ethylene copolymerization with 1-hexene, producing poly（ethylene-co-l-hexene）s with moderate molecular weight and reasonable 1-hexene content.     

Preparation and characterization of M2(SeAr′)6 and mixed ligand M2(OR)2(SeAr′)4 species (M = Mo, W)

Toluene solutions of M₂(NMe₂)₆ (M = Mo, W) react with mesitylene selenol (Ar′SeH) to give M₂(SeAr′) ₆ complexes. MO₂(OR)₆ (R = ^tBu, CH₂^tBu) react with excess> 6 fold) Ar′SeH to give Mo₂ (SeAr′)₆, whilst W₂(OR)₆(py)₂ (R = ⁱPr, CH₂^tBu) react with excess (> 6 fold) Ar′SeH to give W₂(OR)₂(SeAr′)₄. Reaction of MO₂(OPrⁱ)₆ with Ar′SeH produces Mo₂(OPrⁱ)₂ (SeAr′)₄ which crystallizes in two different space groups. These areneselenato complexes are air-stable and insoluble in common organic solvents. X-ray crystallographic studies revealed that the Mo₂(SeAr′)₆ and W₂(SeAr′)₆ compounds are isostructural in the solid state and adopt ethane-like staggered configurations with the following important structural parameters, M---M (W---W/Mo---Mo) 2.3000(11)/2.2175(13) Å, M---Se 2.430 (av.)/2.440 (av.) Å, M---M---SE 97.0° (av.)°. In the solid state W₂(OⁱPr)₂(SeAr′)₄ adopts the anti-configuration with crystallographically imposed C_i symmetry and W---W 2.3077(7) Å, W---Se 2.435 (av.) Å, W---O 1.858(6) Å; W---W---SE 100.27(3)°, 93.8(3)° and W---W---O 108.41(17)°. Mo₂(OPrⁱ)₂(SeAr′) ₄ crystallizes in both P and A2/a space groups in which the molecules are isostructural with each other and the tungsten analogue. Important bond lengths and angles are Mo---Mo 2.180(24) Å, Mo---Se 2.432(av.) Å, Mo---O 1.872(9) Å, Mo---Mo---Se 99.39(9)°, 94.71(8)°, Mo---Mo---O 107.55(28)°.     

Alkoxy derivatives of trithiazyltrichloride

Reaction of trithiazyltrichloride, (NSCl)₃, with NaOR in ROH (R = Me, Et, ⁱPr, ⁿPr, ^nBu, ^tBu, pentyl, amyl, cyclohexyl, benzyl) gives (NSOR)₃. The compounds have been characterized by IR and mass spectroscopy and in the case of R = methyl, (2a) and benzyl, (2e) by X-ray crystallography. In the structures of both (2a) and (2e) the S₃N₃ ring adopts a flattened chair cyclohexane con7mation with the substituents being axial.     

Oxidative alkylation of (η-C5Me5)2TiR (R = Cl, Me, Et, CH=CH2, Ph, OMe, N=C(H)Bu) to (η-C5Me5)2Ti(Me)R by group 12 organometallic compounds MMe2

Oxidative alkylation of Cp^*₂TiX (Cp^*: η⁵-C₅Me₅; X = OMe, Cl, N=C(H)^tBu) and Cp^*₂TiMe by CdMe₂ or ZnMe₂ gives diamagnetic Cp^*₂Ti(Me)X and Cp^*₂TiMe₂ respectively, and cadmium or zinc. The reactions of Cp^*₂TiR (R = Et, CH=CH₂, Ph) with MMe₂ (M = Cd, Zn) give statistical mixtures of Cp^*₂Ti(Me)R, Cp^*₂TiMe₂ and Cp^*₂TiR₂. Dimethylmercury does not react with Cp^*₂TiX.     

Half-way coordination state of a butadienyl group on ruthenium. η-Allylic bonding with η-character or vice versa

The butadienyl complexes formed by the reaction of trans-(R¹)CH=CHCCR² (R¹, R² = SiMe₃, ^tBu, Me, Et) with RuCl(CO)H(PPh₃)₃ exhibit unique structures: instead of taking the 18-electron configuration of the metal by conventional η³-coordination of the butadienyl ligand, they shift significantly to the 16-electron η¹-coordination state.     

The chemistry of 1,3,5-triazacyclohexane complexes 5: cationic zinc(II) alkyl complexes of N-alkylated 1,3,5-triazacyclohexanes and 13-benzyl-1,5,9-triazatricyclo[7.3.1.0]-tridecane

Diethylzinc reacts with hydroperchlorates of N-alkylated 1,3,5-triazacyclohexanes (R₃TAC; R = methyl (Me), benzyl (Bz), isopropyl (ⁱPr)) and with the hydrotetrafluoroborate of 1,3,5-tris-(para-fluorobenzyl)-1,3,5-triazacyclohexane (FBz₃TAC) to give the corresponding cationic zinc ethyl complexes [(R₃TAC)Zn(Et)][X] (X = ClO₄⁻, BF₄⁻). Similar complexes were obtained from diethylzinc treated with [HNMe₂Ph][BF₄] or [HNMe₂Ph][B(C₆F₅)₄](Et₂O) in the presence of R₃TAC (R = Bz, FBz, s-1-phenylethyl (s-PhMeCH)). A product of decomposition of [(Bz₃TAC)Zn(Et)][ClO₄] was analyzed by X-ray diffraction. The structures of [({s-PhMeCH}₃TAC)Zn(Et)][BF₄] an [(FBz₃TAC)Zn(Et)][BF₄] were estimated using nuclear Overhauser enhancement spectroscopy. Protonolysis of diethylzinc with [HNMe₂Ph][BF₄] in the presence of 13-benzyl-1,5,9-triazatricyclo[7.3.1.0^5,13]-tridecane (BzTATC) yielded the complex [(BzTATC)Zn(Et)][BF₄].     

Solid-state static Cu and P CP/MAS NMR, and liquid-state EXAFS studies on copper(I) O,O′-dialkyldithiophosphate cluster compounds: Formation of the copper(I) O,O′-di-iso-amyldithiophosphate cluster compound on the surface of synthetic chalcocite

Polycrystalline octa-nuclear copper(I) O,O′-di-i-propyl- and O,O′-di-i-amyldithiophosphate cluster compounds, {Cu₈[S₂P(OR)₂]₆(μ₈-S)} where R = ⁱPr and ⁱAm, were synthesized and characterized by ³¹P CP/MAS NMR at 8.46 T and static ⁶⁵Cu NMR at multiple magnetic field strengths (7.05, 9.4 and 14.1 T). The symmetries of the electronic environments around the P sites were estimated from the ³¹P chemical shift anisotropy (CSA) parameters, δ_aniso and η. Analyses of the ⁶⁵Cu chemical shift and quadrupolar splitting parameters for these compounds are presented with the data being compared to those for the analogous octa-nuclear cluster compounds with R = ⁿBu and ⁱBu. The ⁶⁵Cu transverse relaxation for the copper sites in {Cu₈[S₂P(OⁱPr)₂]₆(μ₈-S)} and {Cu₈[S₂P(OⁱAm)₂]₆(μ₈-S)} was found to be very different, with a relaxation time, T₂, of 590 μs (Gaussian) and 90 μs (exponential), respectively. The structures of {Cu₄[S₂P(OⁱPr)₂]₄} and {Cu₈[S₂P(OⁱPr)₂]₆(μ₈-S)} cluster compounds in the liquid- and the solid-state were studied by Cu K-edge EXAFS. The disulfide, [S₂P(OⁱAm)₂]₂, was obtained and characterized by ³¹P{¹H} NMR. The interactions of the disulfide and of the potassium O,O′-di-i-amyldithiophosphate salt with the surfaces of synthetic chalcocite (Cu₂S) were probed using solid-state ³¹P NMR spectroscopy and only the presence of copper(I) dithiophosphate species with the {Cu₈[S₂P(OⁱAm)₂]₆(μ₈-S)} structure was observed.     

Standard molar enthalpies of formation of lithium alkoxides

The standard (p⁰ = 0.1 MPa) molar enthalpies of formation of several crystalline lithium alkoxides, ΔH_f⁰(LiOR, cr), have been determined by reaction-solution calorimetry at 298.15 K. A linear correlation has been found between ΔH_f⁰(LiOR, cr) and ΔH_f⁰(ROH, 1) for R = n-alkyl, enabling the prediction of data for other lithium alkoxides. The deviations from the linear correlation observed for R =ⁱPr and ^tBu were tentatively explained in terms of the electronegativities of the OR groups. The experimental data were also used to derive the lattice energies and the thermochemical radii of the anions OR⁻. The results were compared with those derived from the enthalpies of formation of the analogous sodium alkoxides, reported in a previous publication.     

Recent studies on metal and metalloid bis(trimethylsilyl)methyls and the transformation of the bis(trimethylsilyl)methyl into the azaallyl and β-diketinimato ligands

Recent results (post-1990) on the synthesis and structures of bis(trimethylsilyl)methyls M(CHR₂)_m (R = SiMe₃) of metals and metalloids M are described, including those of the crystalline lipophilic [Na(μ-CHR₂)]_∞, [Rb(μ-CHR₂)(PMDETA)]₂, K₄(CHR₂)₄(PMDETA)₂, [Mg(CHR₂)(μ-CHR₂)]_∞, P(CHR₂)₂ (gaseous) and P₂(CHR₂)₄, [Yb(CHR₂)₂(OEt₂)₂] and [{Yb(CR₃)(μ-OEt)(OEt₂)}₂]; earlier information on other M(CHR₂)_m complexes and some of their adducts is tabulated. Treatment of M(CHR₂) (M = Li or K) with four different nitriles gave the X-ray-characterized azaallyls or β-diketinimates , and (LL′ = N(R)C(^tBu)CHR, L′L′ = N(R)C(Ph)C(H)C(Ph)NR, LL″ = N(R)C(Ph)NC(H)C(Ph)CHR, R = SiMe₃ and Ar = C₆H₃Me₂-2,5). The two lithium reagents were convenient sources of other metal azaallyls or β-diketinimates, including those of K, Co(II), Zr(IV), Sn(IV), Yb(II), Hf(IV) and U(VI)/U(III). Complexes having one or more of the bulky ligands [LL′]⁻, [L′L′]⁻, [LL]⁻, [LL″]⁻, [L″L]⁻, [LL]⁻ and [{N(R)C(^tBu)CH}₂C₆H₄-2]²⁻ are described and characterized (LL = N(H)C(Ph)C(H)C(Ph)NH, L″L = N(R)C(^tBu)C(H)C(Ph)NR, LL = N(R)C(^tBu)CHPh). Among the features of interest are (i) the contrasting tetrahedral or square-planar geometry for and , respectively, and (ii) olefin-polymerization catalytic activity of some of the zirconium(IV) chlorides.     

Formation and structure of [Co{Ph2PN(Bu)PPh2-P,P′}2(CO)][Co)(CO)4] - a cage molecule-pair or an ion-pair complex?

The strong π-acid ligand Ph₂PN(ⁱBu)PPh₂ reacts with Co₂(CO)_S (1:1) to give Co₂[μ-Ph₂PN(ⁱBu)PPh₂] (μ-CO)₂(CO)₄ (1); however, when the ratio is 2:1 a novel species [Co{Ph₂PN(ⁱBu)PPh₂-P,P′}₂(CO)][Co(CO)₄] (2) has been obtained. Crystal data for 2: M_r = 1140.83; triclinic, space group P , a = 12.330(2), b = 13.340(2), c = 18.122(3) Å, = 86.63(1), β = 80.75(1), γ = 84.24(1)°, V = 2924 ų, Z = 2; R = 0.060 for 3711 reflections having I 3σ(I). The results of X-ray diffraction, ESR, variable-temperature magnetic susceptibility, conductivity, and XPS analysis support that the species 2 is a d⁹-d⁹ cage molecule-pair. The mechanism for the formation of the species 2 has been investigated initially by ³¹P NMR.     

Preparation and characterization of mixed alkyl amido complexes of gallium

A series of primary amido gallium alkyl complexes that includes a base free dimer, [^tBu₂Ga(μ-N(H)^tBu)]₂ (1), Lewis base stabilized monomeric complexes, ⁿBu₂Ga(N(H)^tBu)(THF) (2) and ⁿBu₂Ga[NH(2,6-Me₂C₆H₃)]py (3) and an anionic complex, ⁿBu₂Ga[NH(2,6-Me₂C₆H₃)]₂[Li(Et₂O)] (4) is reported. Complex 1 crystallizes in the triclinic space group P-1 (a = 10.265(5) Å, B = 15.752(6) Å, C = 8.932(4) Å, = 90.32(3)°, β = 105.61(3)°, γ = 88.24(4)°) with two molecules, each residing on an inversion center, in the asymmetric unit. Structural analysis revealed a planar Ga₂N₂ core with both the bridging N and the Ga centers in distorted tetrahedral environments (Ga---C distances 2.052(3)-2.065(3) Å and Ga---N distances 2.060(3)-2.069(3) Å). The use of excess amido ligand allowed the isolation and crystallization of 4. Complex 4 crystallized in the monoclinic space group P21/n (a = 8.666(2) Å, B = 22.305(3) Å, C = 15.570(3) Å, β = 103.47(2)) with Z = 4. The pseudotetrahedral gallium center has a coordination sphere composed of two amido ligands (Ga---N1 = 2.011(8) Å, Ga---N2 = 2.006(7) Å), and two ⁿBu ligands (Ga---C17 = 2.002(9) Å Ga---C21 = 1.985(12) Å). A bridging interaction of the lithium cation with the lone pair of electrons on each of amido nitrogen atoms generates a molecular core which is made up of a planar Ga---N1---Li---N2 distorted square (N1---Gal---N2 94.4°, Gal---N2---Lil 86.2°, N1---Li1---N2 92.2°, Gal---N1---Li1 87.1°).     

Dibenzo[b, e]-7,7,8,8-tetraneopentyl- and dibenzo[b, e]-7,7,8,8-tetraisopropyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes: interaction with tetracyanoethylene and transition metal chlorides

Dibenzo[b,e]-7,7,8,8-tetraalkyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes (1: R = ^tBuCH₂; 2: R = ⁱPr) were prepared by the reaction of ClR₂SiSiR₂Cl with lithium anthracenide in 1,2-dimethoxyethane (DME) at room temperature. The structure of 1 was determined by X-ray crystallography. Crystal data for 1: monoclinic, rC2/c, A = 12.941(2), B = 14.601(1), C = 35.109(6) Å, β = 94.957(7)°, V = 6609(2) ų, Z= 8, R = 0.048, R_w = 0.053 for 4037 reflections. Compounds 1 and 2 show the bathochromic shift of ¹L_a and ¹L_b bands in UV spectra and exhibit considerably low oxidation potentials due to effective σ-π conjugation. Compounds 1 and 2 form charge-transfer complexes with tetracyanoethylene (TCNE). In the case of 1, the charge-transfer complex (1: TCNE = 2: 1) could be isolated as crystals and the structure was determined by X-ray crystallography. Crystal data for the 1-TCNE complex: monoclinic, C2/c, A= 10.267(2), b = 36.077(4), C = 20.022(4) Å, β = 100.680(8)°, V = 7288(2) ų, Z = 4, R = 0.045, R_w = 0.077 for 4120 reflections. The action of transition metal chlorides on 2 resulted in [4+2] cycloreversion to form ClⁱPr₂SiSiⁱPr₂Cl and anthracene.     

La-NMR-spektroskopie an allyllanthan(III)-komplexen

¹³⁹La-NMR chemical shifts were measured for several anionic complexes of formulae Li(C₄H₈O₂)_3/2 [La(ν³-C₃H₅)₄], [Li(C₄H₈O₂)₂][Cp′_nLa(ν³-C₃]H₅)_4−n] (Cp′ = Cp(ν⁵-C₅H₅); n = 1, 2 and Cp′ = Cp * (ν⁵-C₅Me₅); N = 1) and Li[R_nLa(ν³-C₃H₄)₄−n] (R = N(SiMe₃)₂; n = 1, 2 and R = CCsIMe₃; n = 4), as well as for neutral compounds for formulae La(ν³-C₃H₅)₃L_n (L = (C₄H₈O₂)_1.5, (HMPT)₂, TMED), Cp′_nLa(ν³-C₃H₅)_3−n (Cp′= Cp(ν⁵-Cp₅H₅), Cp *(ν⁵-C₅Me₅); n = 1, 2) and La(ν³-C₃H₂)₂X(THF)₂ X = Cl, Br, I). Typical ranges of the ¹³⁹La-NMR chemical shifts were found for the different types of complex independent of number and kind of organyl groups directly bonded to lanthanum.

Zusammenfassung

¹³⁹La-NMR-Spektroskopie wurde an einer Reihe anionischer Allyllanthanat(III)-Komplexe der Zusammensetzung ]- [La)ν³-C₃H₅)₄, [Li(C₄H₈)₂][Cp′_nLa(ν³-C₃H₅)_4−n(Cp′ = Cp(ν⁵-C₅H₅); n = 1, 2 und Cp′ = Cp * (ν⁵-C₅Me₅); N = 1) und Li[R_nLa(ν³-C₃H₅)_4−n (R = B(SiMe₃)₂; n = 1, 2 und R = CCSiMe₃; n = 4 sowie neutraler Allyllanthan(III)-Komplexe der Zusammensetzung La(ν³-C₃H₅)₃L_n (L_n = (C₄H₈O₂)_1.5, (HMPT)₂, TMED), Cp′_n, La(ν³-C₃H₅)_3−n (Cp′ = Cp(ν⁵-C₅H₅), Cp * (ν⁵- Cp₅Me₅); n = 1, 2) und La(ν³-Cp₃H₅)₂X(THF)₂ (X = Cl, Br, I) durchgefürt. In Abhängikeit von der Anzahl und der Art der am Lanthan gebundenen Gruppen wurden für die verschieden Komplextypen charakteristische Resonanzbereiche ermittelt.     

Steric and electronic effects of the R in IndTiCl2(OR) catalysts on the syndiospecific polymerization of styrene

Four alkoxyl ligand substituted indenyl titanium dichloride complexes, IndTiCl₂(OR) (R=Me (2), Et (3), ⁱPr (4), cyclohexyl (5)) were prepared, and evaluated as catalysts for the syndiospecific polymerization of styrene when activated with methylaluminoxane (MAO). Alkoxyl ligand substituted complexes showed higher catalytic activities than IndTiCl₃ (1) except for complex 5. When R=Et, the catalyst 3 showed the highest activity. A study of the steric and electronic effects of alkoxyl ligand revealed that the more electron-donating and less steric bulky R group was more suitable for the improvement of the catalytic activity. When the polymerization was carried in solution at high molar ratio of Al/Ti=4000, the s-PS% of obtained polymer were in the range of 99.0–99.6%. The highest melting point of 276.9°C was obtained by using 2 as catalyst. The influence of polymerization temperature was also investigated. The maximum polymerization activities were found at 50°C for all of the above complexes, but the percentages of s-PS were insensitive to the polymerization temperature.     

Photochemical reactions of alkynyl iron (II) complexes with carbon disulfide. Insertion of CS2 into an iron-C(sp) bond

The novel alkynyldithiocarboxylate complexes [Fe(η⁵-C₅H₅)(S₂CCCR) (dppm-P)] (3a,b) and [Fe(η₅-C₅H₅)(S₂CCCR)(PPh₃)] (4a,b) were obtained through the insertion of CS₂ into the iron-akynyl bond in the complexes [Fe(η₅-C₅H₅)(CCR)(L)(L′] L, L′ = dppm R = Ph (1a), ^tBu(1b); L = (CO), L′ = (PPh₃) R = Ph (2a), ^tBu (2b). Variable-temperature ³¹P{¹H} NMR studies indicate the presence of two different isomers, [Fe(η⁵-C₅H₅)(η³-S,C,S′---S₂CCCR)(L)(L′)] and [Fe(η⁵-C₅H₅(η²-S,S′-S₂CCCR)(L)(L′)], which rapidly interconvert at room temperature. The synthesis of the precursor complex [Fe(η⁵-C₅H₅)(CC^tBu)(CO)(PPh₃)] is also described.