Stabilization of platinum(II) hydrides by tri-t-butylarsine; facile syntheses of stable trans-PtH2[As(t-Bu)3]2 and trans-PtHX[As(t-Bu)3]2 complexes

trans-PtH₂[As(t-Bu)₃]₂ was prepared in very good yield by afacile reaction of K₂PtC1₄ with As(t-Bu)₃ in alkaline ethanol. Treatment of trans-PtH₂[As(t-Bu)₃]₂ with CF₃CO₂H or HCI afforded trans-PtH(O₂CCF₃)[As(t-Bu)₃]₂ or trans-PtHCl[As(t-Bu)₃]₂. respectively, in almost quantitative yield.     

Cleavage of the sulfur-sulfur bond in 2,4-dinitrophenyl 4-substituted phenyl disulfides by trans-[IrX(CO)(PPh3)2]

A series of 2,4-dinitrophenyl 4-Y-phenyl disulfides (Y=NO₂, Br, F, H, CH₃, or CH₃O) have been shown to react with trans-IrX(CO)(PPh₃)₂ (X=Cl, Br, or I) in refluxing benzene to form “oxidative-elimination” products of the type, [IrX(SC₆h₄Y)(SC₆H₃(NO₂)₂)(CO)(PPh₃)]₂. The physical properties of these complexes are discussed in relation to their structure in the solid state and in solution. In particular, available infrared spectral data indicate that these complexes contain 2,4-dinitrobenzenethiolato bridging groups and that the substituted arenethiolato ligand is trans to carbon monoxide.     

Structural changes resulting from doping Ti2O3 with Sc2O3 or Al2O3

The crystal structures of (Ti_1?xSc_x)₂O₃, x = 0.0038, 0.0109, and 0.0413, and of (Ti_0.99Al_0.01)₂O₃, have been determined from X-ray diffraction data collected from single crystals using an automated diffractometer, and have been refined to weighted residuals of 25–34. Cell constants have also been determined for x = 0.0005, 0.0019, and 0.0232. The compounds are rhombohedral, space group $\text{R}\text{3}\text{c}$, and are isomorphous with α-Al₂O₃. The hexagonal cell dimensions range from a = 5.1573(2)Å, c = 13.613(1)Å for (Ti_0.9995Sc_0.0005)₂O₃ to a = 5.1659(4)Å, c = 13.644(1)Å for (Ti_0.9587Sc_0.0413)₂O₃, and a = 5.1526(2)Å, c = 13.609(1)Å for (Ti_0.99Al_0.01)₂O₃. Sc and Al substitution cause similar increases in the short near-neighbor metal-metal distance across the shared octahedral face; for Sc doping the increase is from 2.578(1) Å in pure Ti₂O₃ to 2.597(1) Å in (Ti_0.9587Sc_0.0413)₂O₃. By contrast, changes in the metal-metal distance across the shared octahedral edge appear to be governed by ionic size effects. The distance increases from 2.994(1) Å in Ti₂O₃ to 3.000(1) Å in (Ti_0.9587Sc_0.0413)₂O₃ and decreases to 2.991(1) Å in (Ti_0.99Al_0.01)₂O₃.     

Dynamic 19F NMR studies The torsional barrier in pentafluorobenzaldehyde,its conjugate acid and protonated pentafluoroacetophenone

An upper limit of the barrier to internal rotation around the phenyl-carbonyl bond in pentalfluorobenzaldehyde dissolved in a freon mixture has been estimated from low temperature ₁₉F NMR study. Protonation of this compound increases drastically the free energy of activation ΔG≠. Complete lineshape analysis leads to ΔG≠ (273 K) = 60.4 kJ/mol, comparable to the value obtained for protonated benzaldehyde. This result, as well as those obtained by CNDO/2 calculations support the conclusions that protonated pentafluorobenzaldehyde is planar in the ground state. This is not the case for protonated pentafluoroacetophenone in which the lower barrier height when compared to protonated acetophenon has been related to the steric strain and dipole repulsion.     

Metalloidalmethyl substituent effects by 13C and 19F NMR : electron release in the neutral ground state.

¹³C and ¹⁹F chemical shift studies of a series of CH₂M(CH₃)₃ and CH₂M(C₆H₅)₃ (M  Si, Ge, Sn, Pb) - substituted aryl derivatives (phenyl; 1-naphthyl; 2-naphthyl) have established unambiguously that the order of hyperconjugative electron release in the neutral ground state is Pb>Sn>Ge>Si. This order is clearly at variance with the commonly accepted order(Pb>Sn>Ge>Si) based on studies of electron deficient substrates. The phenomenon is discussed in terms of current theories on σ-π interactions. In addition, substituent parameters (σ_I and σ_R^o) for the PB(CH₃)₃ group have been derived utilizing new data from the fluorophenyl tag. These new constants are compared with those previously reported.     

Coordination de la phosphine organo-fer [CpFeIIC6Me5CH2PPh2]+ au RhI et proprietes spectroscopiques,electrochimiques et catalytiques des complexes heterobinucleaires FeII-RhI

The reactions between the phosphine-organoiron [CpFe^II-η⁶-C₆Me₅CH₂PPh₂]⁺ PF₆^? (1) and [RhCl(η⁴-diolefin)(μ-Cl)]₂ in CH₂Cl₂ at reflux give the new heterobinuclear air-stable crystalline complexes [CpFe^II-η⁶-C₆Me₅CH₂)P(Ph)₂Rh(η⁴-diene)Cl]PF₆,(D'*-diene=cyclooctadiene (COD): 65%, 2; trimethylfluorobenzobicyclo[2.2.2]octadiene (Me₃TFB): 48%, 3). Complexes 2 and 3 have been studied by ¹H, ¹³C and ³¹P NMR spectroscopy and they are carbonylated (CO, 1 atm). Cyclic voltammetry experiments with addition of MeOH show electron transfer Fe^IRh^I → Fe^IIRh⁰, the presence of a catalytic wave Fe^I/Fe^II and the possible formation of Rh hydrides. Under normal conditions 2 is a catalyst for hydrogenation of cyclohexene, but it is less efficient than the known mononuclear Rh¹ analogues.     

The preparation of cis- and trans-[PtH(C6Cl5)(PEt3)2 and a study of the “hydride-donor capacity” of the complexes trans- [PtH(C6X5(PEt3)2] (X = F and Cl)

The preparations of cis- and trans-[PtH(C₆Cl₅)(PEt₃)₂] by thermal decomposition of cis- and trans-[Pt(OCHO)(C₆Cl₅)(PEt₃)₂], respectively, are reported. Also described are cis- and trans-[Pt(SnCl₃)(C₆Cl₅)(PEt₃)₂], obtained by treating SnCl₂ with cis- and trans-[PtCl(C₆,Cl₅)(PEt₃)₂], respectively. It is shown that while trans- [PtH(C₆Cl₅)(PEt₃)₂] does not form hydride-bridged complexes in the presence of trans-(PtH(MeOH)(PEt₃)₂]⁺, the corresponding complex trans-[PtH(C₆)(PEt₃)₂] reacts with the same solvento complex, in methanol, giving labile [(PEt₃)₂HPt(-μH)Pt(C₆F₅)(PEt₃)₂]⁺.     

Chemistry of mixed ligand complexes of platinum: crystal and molecular structure of trans-[PtCl(CH3)(PEt3)(AsPh3)]

The dimethyl platinum(II) complex containing mixed ligands, cis-[Pt(CH₃)₂(PEt₃)(AsPh₃)] reacted with one equivalent of hydrogen chloride yielding trans-[PtCl(CH₃)(PEt₃)(AsPh₃)]. The X-ray crystal structure of the molecule shows the trans orientation of the PEt₃ and AsPh₃ ligands.     

Structure and chemical behavior of an organoaluminum compound [Rb2AlOCR′NPh]2, a stereospecific catalyst for polymerization of acetaldehyde

A series of organoaluminum compounds [R₂AlOCR′NPh]₂, which are the reaction products between trialkylaluminum compounds and secondary acid amides and are excellent catalysts for stereospecific polymerizations of aldehydes, were isolated in the crystalline state. Chemical behavior of such compounds toward Lewis acids and bases were interpreted in terms of the structures of [Me₂AlOCPhNPh]₂ and its trimethylamine oxide complex Me₃NO·AlMe₂OCPhNPh which were determined by X-ray structure analyses. Reaction products of primary and tertiary acid amides with trialkylaluminum compounds were also studied.     

The 13C NMR spectra and structure of ferrocenylcarbenium ions

The ¹³C NMR spectra ofthe series of α,α’ -dideuterated ferrocenylcarbenium ions and their precursors, ferrocenylcarbinols as well as other ferrocene derivatives have been measured. The structures of ferrocenylcarbenium ions is discussed.     

31P and 195Pt NMR spectra of [Pt(PPh32(μ-η2-C2H4−nXn)] (n = 0 … 4; X = CN,COOMe)

³¹P and ¹⁹⁵Pt NMR measurements on compounds of the type [Pt(PPh₃)₂ (μ-η²-C₂H_4?nX_n)] (n = 0…4; X = CN, COOMe) are reported and discussed.     

Reaction of some tertiary phosphines and phosphites with [Co(η5-C5H5)(S2C2{CN}2)]

Reaction of the 16 electron monomer [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η⁵-C₅H₅)(S₂C₂{CN}₂)L] which for L = P(OR)₃ have J($\text{P}$C₅$\text{H}$₅) ca. 6 Hz but J($\text{P}$C₅$\text{H}$₅) = 0 for L = PR₃.     

Alternativ-Liganden VII1: Chelatkomplexe des typs (Me = CH3; X = CH3, Cl)

Chelate complexes of the type (CO)₄M$\text{nPMe}{}_2\text{CH}{}_2\text{Ch}{}_2\text{S}$iX₂ (X = Me, Cl) have been prepared from Na[Mn(CO)₅] and HMn (CO)₅, respectively, by two-step reactions with the ligands Me₂PCH₂CH₂SiX₂R′ using alkali salt, amine or HCl elimination. (CO)₄M$\text{nPMe}{}_2\text{Ch}{}_2\text{CH}{}_2\text{S}$iCl₂ is also obtained by cleavage of Mn₂(CO)₁₀ with Me₂PCH₂CH₂SiCl₃. IN the case of HMn (CO)₅ the intermediates (CO)₄Mn (H) L [L = Me₂PSiMe₃, Me₂PCH₂CH₂SiMe₂ (NMe₂), Me₂PCH₂CH₂SiCl₂ (NMe₂] can be isolated. The new compounds were identified by analytical and spectroscopic (IR, PMR, MS) methods.     

Reaction of trans-[Co(en)2(SO3)(H2O)]+ with imidazole and containing ligands

trans-[Co(en)₂(SO₃)(H₂O)]⁺ reacts with imidazole (ImH) and imidazole containing ligands (L) to form trans-[Co(en)₂(SO₃)L]⁺ in the pH range 6.0–9.0. The complex seems to react both in the hydroxy and in the aquo form. The rate constant for the reaction of imidazole with the aquo form is 6.0±0.7 and 4±1M^?1s^?1 for the reaction with the hydroxy form at 25°C. The apparent equilibrium constant for formation of the imidazole complex at pH 7 is consistent with the value of 3 x 10² measured previously. Appreciable amounts of complex form only in the pH 6–9 range. Above pH 9 NMR spectra show that even the immediate products are different. In aged solutions at all pHs other products form.     

Enthalpies of reaction of bis(triphenylphosphine)(trans-stilbene)platinum(0) with diphenylcyclopropenone and benzocyclobutenedione

Enthalpies, ΔH(1) ?94.8 ± 6.0 and ΔH(6) ?57.1 ± 5.1 kJ mol^?1, of the following reactions have been measured calorimetrically [Pt(trans-stilbene)(PPh₃)₂](s) + dpcp(g) → (PPh₃)₂Pt(dpcb)(s) + trans-stilbene(g) (1) [Pt(trans-stilbene)(PPh₃)₂](s) + bcbd(g) → (PPh₃)₂Pt(bcpd)(s) + trans-stilbene (g) (6) where dpcp is diphenylcyclopropenone, (PPh₃)₂Pt(dpcb) is (1,1-bistriphenylphosphine)platinadiphenylcyclobutenone, (PPh₃)₂$\text{PtC(Ph)C(Ph)C}$O, bcbd is benzocyclobutene-1,2-dione and (PPh₃)₂Pt(bcpd) is (1,1-bistriphenylphosphine)platinabenzocyclopentanedione,

. It is concluded that the five-membered platinacyclo ring system in (PPh₃)₂Pt(dpcb) is not heavily strained.     

Structural studies on osmium carbonyl hydrides: XXXI. Crystal and molecular structure of CpWOs3(CO)9(μ-H)(μ-O)(μ-CHCH2C6H4Me), a hydrido-alkylidene produced by hydrogenation of a μ3-alkylidyne

The complex CpWOs₃(CO)₉(μ-H)(μ-O)(μ-CHCH₂C₆H₄Me), previously prepared by hydrogenation of CpWOs₃(CO)₉(μ-O)(μ₃-CCH₂C₆H₄Me), has been subjected to a single-crystal X-ray diffraction study. The complex crystallizes in the non-centrosymmetric monoclinic space group Cc(C_s⁴; No. 9) with a 14.1510(27), b 13.9257(22), c 13.3179(19) Å, β 92.023(13)°, V 2622.8(7) ų and D(calcd) 3.06 g cm^?3 for Z = 4 and mol. wt. 1206.8. Single-crystal X-ray diffraction data were collected with a Syntex P2₁ automated four-circle diffractometer and the structure was refined to R 3.5% for all 2476 independent observations (Mo-K_α radiation, 2θ = 4.5–40.0°) and R 3.4% for those 2430 data with | F₀| > 3.0σ(| F₀|). The molecule contains a tetrahedral WOs₃ core associated with 60 valence electrons. Each osmium atom is associated with three terminal carbonyl ligands and the tungsten atom is linked to an η⁵-C₅H₅ ligand. In addition, the μ-oxo ligand is involved in a WO: → Os bridge (in which WO(B) 1.737(17), Os(3)← :O(B) 2.167(16) Å and WO(B)Os(3) 96.0(7)°), the μ-hydride ligand spans the Os(1)Os(3) linkage and the μ-CHCH₂C₆H₄Me ligand bridges the WOs(2) linkage (WC(1) 2.068(26) and Os(2)C(1) 2.281(26) Å).     

NMR (195Pt and 13C) contribution to the study of some Pt(II), Pt(IV) and mixed-valence thioamido complexes

The ¹⁹⁵Pt and ¹³C chemical shifts (δ_Pt and δ_c) are reported for platinum(II), platinum(IV) and class II mixed-valence complexes, with general formula [PtL₄]X₂, cis- and trans-PtL₂X₂, PtL₂X₄ and Pt₂L₄X₆ (where L may be thiourea, 2-imidazolidine-thione, tetrahydro 2-pyrimidinethione, thiocaprolactam, pyridine-2-thione and tetramethylthiourea, and X may be Cl or Br). The ¹⁹⁵Pt chemical shifts can be understood in view of ¹³C data in terms of variations of electronegativities and σ-donor abilities of ligands attached to platinum.     

Photoinitiated reactions of (η-C5H5)2MH3 (M  Nb,Ta) with Mn2(CO)10: structure of (η-C5H5)2(CO)Ta(μ-H)Mn2(CO)9

The photoreaction of (η-C₅H₅)₂TaH₃ with Mn₂(CO)₁₀ gives, inter alia, (η-C₅H₅)₂(CO)Ta(μ-H)Mn₂(CO)₉, whose crystal structure reveals an open, bent trimetallic framework. Preliminary mechanistic studies show that this and the analogous niobium reaction proceed via a complex sequence of thermal steps following photoinitiation.     

Synthesis, 119Sn, 13C and 195Pt NMR studies of five-coordinate rhodium(I), iridium(I) and platinum(II) complexes containing three trichlorostannate ligands

The synthesis and ¹¹⁹Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of Rh^I, Ir^I and Pt^II are reported. The Rh^I and Ir^I complexes are complex dianions of the form (PPN)₂[M(SnCl₃)₃L₂] where L can be CO, CN (cyclohexyl) or L₂, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl₃)₃L₂] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl₃)L₄] including [Ir(SnCl₃)(NBD)(1,5-COD)] have been prepared and characterized. Their δ(¹¹⁹Sn), δ(¹³C), δ(¹⁹⁵Pt) as well as ¹J(¹⁰³Rh, ¹¹⁹Sn), ¹J(¹⁹⁵Pt, ¹¹⁹Sn), ²J(¹¹⁹Sn, ¹¹⁷Sn) and ²J(¹¹⁹Sn, ¹³C) data are given. A trans influence series, based on ¹J(¹⁹⁵Pt, ¹¹⁹Sn), reveals the following sequence: H^? > PR₃ > AsR₃ > SnCl₃^? > olefin > Cl^?.