Free-radical chain decomposition of ozone initiated by di(tert-butyl) trioxide

Di(tert-butyl) trioxide in a solution of CFCl₃ (Freon-11) at –23 °C exists in equilibrium with the tert-butoxyl and tert-butylperoxyl radicals virtually without irreversible decomposition. The above radicals decompose ozone to dioxygen with a high effective rate constant, which is proprotional to the square root of the Bu^tOOOBu^t concentration. The kinetic scheme describing the found relationships was proposed.     

Induced decomposition of di(tert-butyl)trioxide

Thermal decomposition of di(tert-butyl)trioxide (Bu^tOOOBu^t) in a wide range of concentrations was studied by visible and IR chemiluminescence. Induced decomposition of Bu^tOOOBu^t caused by its reaction with the peroxy radicals formed in the solvent (CH₂Cl₂) was found and investigated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 924–927, May, 1997.     

Manganese-Mediated Formic Acid Dehydrogenation

A robust and rapid manganese formic acid (FA) dehydrogenation catalyst is reported. The manganese is supported by the recently developed, hybrid backbone chelate ligand ^tBuPNNOP (^tBuPNNOP=2,6-(di-tert-butylphosphinito)(di-tert-butylphosphinamine)pyridine) ( 1 ) and the catalyst is readily prepared with MnBrCO₅ to form [(^tBuPNNOP)Mn(CO)₂][Br] ( 2 ). Dehydrohalogenation of 2 generated the neutral five coordinate complex (^tBuPNNOP)Mn(CO)₂ ( 3 ). Dehydrogenation of FA by 2 and 3 was found to be highly efficient, exhibiting turnover frequencies (TOFs) exceeding 8500 h⁻¹, rivaling many noble metal systems. The parent chelate, ^tBuPONOP (^tBuPONOP=2,6-bis(di-tert-butylphosphinito)pyridine) or ^tBuPNNNP (^tBuPNNNP=2,6-bis (di-tert-butylphosphinamine)pyridine), coordination complexes of Mn were synthesized, respectively affording [(^tBuPONOP)Mn(CO)₂][Br] ( 4 ) and [(^tBuPNNNP)Mn(CO)₂][Br] ( 5 ). FA dehydrogenation with the hybrid-ligand supported 2 exhibits superior catalysis to 4 and 5 .     

ESR study of the thermal decomposition of di-tert-butoxy-tert-butyl alumotrioxide formed in the reaction of tri-tert-butoxyaluminum with tert-butyl hydroperoxide

Tri-tert-butoxyaluminum reacts with tert-butyl hydroperoxide to produce di-tert-butoxy-tert-butyl alumotrioxide, which decomposes heterolytically to form singlet dioxygen and homolytically with the O—O bond cleavage. The Bu^tOO^·, (Bu^tO)₂AlOO^·, Bu^tO^·, and (Bu^tO)₂AlO^· radicals were identified by ESR using spin traps. These findings confirm the formation of aluminum-containing trioxide. The above radicals initiate alkylarene oxidation by the tri-tert-butoxyaluminum—tert-butyl hydroperoxide system. The carbon-centered and alkylperoxy radicals originated from the oxidized substrates were identified.     

Synthesis and structure of stable cis-dimethyl complex of oxotungsten(VI)

Oxotungsten(VI) complex cis-[WO(L^tBu)Me₂] (L^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) was prepared by the transmetallation reaction of [WO(L^tBu)Cl₂] (either cis or trans isomer) with methyl magnesium iodide. This unexpectedly stable dialkyl complex can be activated by Et₂AlCl to catalyze the ring-opening metathesis polymerization of norbornene.     

Interaction of the Negishi reagent Cp2ZrBun 2 with 1,4-bis(tert-butyl)butadiyne

The interaction of the Negishi reagent Cp₂ZrBuⁿ ₂ with 1,4-bis(tert-butyl)butadiyne Bu^tC≡C-C≡CBu^t leads to four products: a five-membered zirconacyclocumulene complex Cp₂Zr(η⁴-Bu^tC₄Bu^t) (2) synthesized earlier by another method, the previously unknown seven-membered zirconacyclocumulene Cp₂Zr[η⁴-Bu^tC₄(Bu^t)-C(C₂Bu^t)=CBu^t] (3) as well as small amounts of the zirconocene binuclear butatrienyl complex Cp₂(Buⁿ)Zr(Bu^tC₄Bu^t)Zr(Buⁿ)Cp₂ (4), and the dimeric acetylide [Cp₂ZrC≡CBu^t]₂ (5). The structure of complexes 2–5 was established by X-ray diffraction studies.     

[Li(tmeda)2][cyclo-(P5But4)]: An unusual ion-separated lithium oligophosphanide

The reaction of lithium with Bu^tPCl₂ and PCl₃ in the ratio 12:4:1 in THF gave a product mixture comprising cyclo-(P₄Bu^t₄), Li₂(P₄Bu^t₄), and lithium tetra-tert-butylcyclopentaphosphanide Li[cyclo-(P₅Bu^t₄)] (1) among other phosphanides and phosphanes. Optimization of the reaction conditions and recrystallization from THF/TMEDA (TMEDA: Me₂NCH₂CH₂NMe₂) gave [Li(tmeda)₂][cyclo-(P₅Bu^t₄)] (1b) which was characterized by multinuclear NMR spectroscopy, mass spectrometry, IR spectroscopy, and elemental analysis. Single-crystal X-ray diffraction studies showed the presence of separated [Li(tmeda)₂]⁺ cations and [cyclo-(P₅Bu^t₄)]^? anions. 1b represents the first structure of a “naked” [cyclo-(P₅Bu^t₄)]^? anion.     

Reactions of tBu2P–PLi–PtBu2 with [(Et3P)2MCl2] (M = Ni,Pd, Pt). Synthesis and Properties of [(1,2‐η‐tBu2P=P–PtBu2)M(PEt3)Cl] (M=Ni,Pd)

^tBu₂P–PLi–P^tBu₂·2THF reacts with [cis‐(Et₃P)₂MCl₂] (M = Ni, Pd) yielding [(1,2‐η‐^tBu₂P=P–P^tBu₂)Ni(PEt₃)Cl] and [(1,2‐η‐^tBu₂P=P–P^tBu2)Pd(PEt₃)Cl], respectively. ^tBu₂P– PLi–P^tBu₂ undergoes an oxidation process and the ^tBu₂P–P–P^tBu₂ ligand adopts in the products the structure of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphino)diphosphenium cation with a short P–P bond. Surprisingly, the reaction of ^tBu₂P–PLi–P^tBu₂·2THF with [cis‐(Et₃P)₂PtCl₂] does not yield [(1,2‐η‐^tBu₂P=P–P^tBu₂)Pt(PEt₃)Cl].     

Optoelectronic and nonlinear optical properties of tBu4PcTiO/polymer composite materials

The optoelectronic and nonlinear optical (NLO) properties of a soluble 2,(3)-(tetra-tert-butylphthalocyaninato)titanium(IV) oxide (tBu₄PcTiO) in solutions and in the solid states have been described. The nonlinear response demonstrated that tBu₄PcTiO exhibited strong RSA at 532 nm for both solution and solid-state based experiments. The decrease in the effective intensity dependent nonlinear absorption coefficient with increasing input intensities possibly results from high order triple state transitions of the excited-state population. No evidence of film fatigue or degradation was observed in the PMMA/tBu₄PcTiO film, after numerous scans at varying laser intensity. The doping of tBu₄PcTiO into poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene-vinylene] (MEH-PPV) results in the apparent increases of the open circuit voltage (Voc) and the short circuit photocurrent density under illumination with 40 mW cm⁻² white-light. The light absorption of tBu₄PcTiO incorporated into polymer represents the dominant contribution to the enhancement of the photocurrent. The dependence of the short circuit photocurrent in an ITO/tBu₄PcTiO-doped MEH-PPV/Al cell on the incident light intensity (I_in) between 30 and 200 mW cm⁻² was also investigated.     

Liquid-phase oxidation of sulfides by an aluminum (and titanium) <Emphasis Type="Italic">tert</Emphasis>-butoxide—<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide system

A system aluminum (and titanium) tert-butoxide—tert-butyl hydroperoxide (1 : 2) under mild conditions (20 °C, 1 h) oxidizes aliphatic and alkylaromatic sulfides and diphenyl sulfide to the corresponding sulfones in yields close to 100%. The oxidation is induced by electron-excited dioxygen formed upon thermal decomposition of intermediate metal-containing peroxy trioxides (ozonides). The latter are formed as a result of the reversible reaction of aluminum or titanium tert-butoxides with tert-butyl hydroperoxide followed by the interaction of di-tert-butoxy-tert-butylperoxyaluminum and tri-tert-butoxy-tert-butylperoxytitanium that formed with another Bu^tOOH molecule. Aluminum-containing peroxide (Bu^tO)₂AlOOBu^t oxidizes sulfides to sulfoxides.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1663–1668, August, 2004.     

Identification of phenylmethylene as an active intermediate of the acid-catalyzed styrene epoxide oxidation in polar solvents

After the acid-catalyzed conversion of styrene epoxide under the action of p-toluenesulfonic acid (acetonitrile, Bu ^t OH (90%) + chlorobenzene (10%) (v/v), 343 K) in the presence of pyridine, a spectrum of iminium ylide was obtained (λ_max = 450 nm), coinciding with the spectrum of the ylide product formed upon the reaction of pyridine with phenylmethylene (published data) during generation of carbenes from diazo compounds by flash photolysis. In an oxygen atmosphere, no ylide absorption band is recorded. This result confirms the previous assumption according to which in epoxide–acid systems, carbene species are formed, react with O₂ in an oxygen atmosphere, and destroy the added hydroperoxides in the absence of O₂.     

Beiträge zur Chemie des Phosphors. 87. 1,2-Di-tert-butyl-3-iso-propyl-cyclotriphosphan,ein stabiles gemischt-substituiertes Cyclotriphosphan

Contributions to the Chemistry of Phosphorus. 87. 1,2-Di-tert-butyl-3-iso-propyl-cylclotriphosphane, a Stable Mixed-substituted Cyclotriphosphane The first kinetically stable mixed-substituted cyclotriphosphane, 1,2-di-tert-butyl-3-iso-propyl-cyclotriphosphane, (PBu^t)₂(PPrⁱ) ( 1 ), was synthesized by [2+1]-cyclocondensation of K(Bu^t)P–P(Bu^t)K with PrⁱPCl₂ in n-pentane. Mainly (PBu^t)₄ as well as mixed-substituted cyclotetra- and cyclopentaphosphanes are formed as by-products. 1 could be isolated in a pure state by high vacuum distillation and was thoroughly characterized. It forms two diastereomers, the more stable of which with a cis-standing tert-butyl and iso-propyl group can be stored without decomposition under inert conditions at room temperature for several days. Through thermolysis of 1 beside other alkylcyclophosphanes the mixed-substituted cyclotetraphosphanes (PBu^t)₂(PPrⁱ)₂ ( 2 ) and (PBu^t)₃(PPrⁱ) ( 3 ) are formed and their ³¹P NMR parameters are reported.     

Das chlorsilylsubstituierte Silanimin Bu2SiNSiClBu2

In the thermolysis of the silaterazolines silatetrazoline ^tBu₂SiNSiCl^tBu₂ · ^tBu₃SiN₃ the silanimine ^tBu₂SiNSiCl^tBu₂ and the silyl azide ^tBu₃SiN₃ are formed quantitatively. The silanimine ^tBu₂SiNSiCl^tBu₂ has been trapped with Et₃NHF, Me₃NHCl, water, 1-butene, 2,3-dimethyl-1,3-butadiene, isobutene, methylvinyl ether, and ^tBu₂SiClN₃. The structure of the disiloxane (^tBu₂SiCl-NH-Si^tBu₂)₂O and of the bis(di-tert-butylchlorsilyl)-substituted silatetrazoline ^tBu₂SiNSiCl^tBu₂ · ^tBu₂SiClN₃ has been determined by X-ray structure analysis.     

Tris(tert-butyl)phosphine selenide,the missing link in tris(tert-butyl)­phosphine chalcogenide structures tBu3P=X (X = O,S, Se,Te)

In tris(tert-butyl)­phosphine selenide, C₁₂H₂₇PSe, all the methyl ligands are disordered over two sites in the ratio 70/30. The mol­ecule displays crystallographic C₃ symmetry. The bond angles at the P atom are distorted tetrahedral [C—P—C 110.02 (5)° and Se=P—C 108.91 (5)°]. The P—C and P=Se bond lengths are 1.908 (1) and 2.1326 (6) Å, respectively. A comparison of the structural data of the complete series of tris(tert-butyl)­phosphine chalcogenides (^tBu₃PO, ^tBu₃PS, ^tBu₃PSe and ^tBu₃PTe) with the corresponding data of other phosphine chalcogenides substituted by smaller organic groups shows the great influence of the bulky tert-butyl ligands.     

Synthesis and some properties of lanthanum, neodymium, and samariumtert-butoxycuprates [(ButO)5Cu2Ln]2

Lanthanum, neodymium, and samariumtert-butoxycuprates [(Bu^tO)₅Cu₂Ln]₂ were synthesized in high yields by reactions of Bu^tOCu with lanthanide metals, the halides Sml₂ and LnX₃ (Ln=La, Nd: X=Cl, 1) and by the reaction of Bu^tOLi with a mixture of LnCl₃ and CuCl. X-Ray diffraction analysis showed that the structure of [(Bu^tO)₅Cu₂Sm]₂ is based on octahedra formed by four copper atoms in equatorial positions and two samarium atoms in axoal positions; the copper and samarium atoms are linked by μ₃-bridging Bu^tO groups. The reactions of lanthanumtert-butoxycuprate with H₂O, HCl, CpH, PhC≡CH, and CO₂ were studied.     

Reactions of 2-arsa- and 2-stiba-1,3-dionato lithium complexes with group 4-7 metal halides

The reactions of a range of 2-arsa- and 2-stiba-1,3-dionato lithium complexes with group 4-7 metals have been investigated. These have given rise to several complexes in which an arsadionate acts as a chelating ligand; [V{η²-O,O-OC(Bu^t)AsC(Bu^t)O}₃], [M{η²-O,O-OC(Bu^t)AsC(Bu^t)O}₂(DME)], M=Cr or Mn; or as an η¹-As-diacylarsenide, [MnBr(CO)₄{As[C(O)Bu^t]₂Li(DME)}]₂. In addition, reactions of lithium arsadionates with TaCl₅ have led to metal mediated arsadionate decomposition reactions and arsadionate oxidative coupling reactions to give the known arsaalkyne tetramer, As₄C₄Bu^t₄, and the new tetraacyldiarsane, [{As[C(O)Mes]₂}₂] Mes=mesityl, respectively. The treatment of several lithium arsadionates with [MoBr₂(CO)₂(PPh₃)₂] has also initiated arsadionate decomposition reactions and the formation of the metal carboxylate complexes, [MoBr(CO)₂{η²-O₂C(R)}(PPh₃)₂] R=Bu^t, Ph, Mes. The X-ray crystal structures of six of the prepared complexes are discussed.     

Das erste Oxatetraphospholan, (PBut)4O

Contributions to the Chemistry of Phosphorus. 244. The First Oxatetraphospholane, (PBu^t)₄O Under suitable conditions, the reaction ot tri‐tertbutylcyclotriphosphane, (PBu^t)₃, with di‐tert‐butylperoxide gives rise to a mixture of 2,3,4,5‐tetra‐tert‐butyl‐1,2,3,4,5‐oxatetraphospholane, (PBu^t)₄O ( 1 ), and 1,2‐di‐tert‐butyl‐1,2‐di‐tert‐butoxidiphosphane, [Bu^t(Bu^tO)P]₂ ( 2 ). Both compounds have been isolated in the pure state. The oxatetraphospholane 1 is a constitutional isomer of 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, which has been reported recently [1]. The corresponding reaction of tetra‐tert‐butylcyclotetraphosphane furnishes only small amounts of 1 because of the kinetic stability of (PBu^t)₄. The diphosphane 2 is presumably a secondary product of primarily formed oxocyclotetraphosphanes (PBu^t)₄O_1–4. The NMR parameters of 1 and 2 are reported and discussed.     

Redox-induced umpolung of transition metal carbenes

Metal carbene complexes have been at the forefront of organic and organometallic synthesis and are instrumental in guiding future sustainable chemistry efforts. While classical Fischer and Schrock type carbenes have been intensely studied, compounds that do not fall within one of these categories have attracted attention only recently. In addition, applications of carbene complexes rarely take advantage of redox processes, which could open up a new dimension for their use in practical processes. Herein, we report an umpolung of a nucleophilic palladium carbene complex, [{PC(sp²)P}^tBuPd(PMe₃)] ({PC(sp²)P}^tBu = bis[2-(di-iso-propylphosphino)-4-tert-butylphenyl]methylene), realized by successive one-electron oxidations that generated a cationic carbene complex, [{PC(sp²)P}^tBuPdI]⁺, via a carbene radical, [{PC˙(sp²)P}^tBuPdI]. An EPR spectroscopic study of [{PC˙(sp²)P}^tBuPdI] indicated the presence of a ligand-centered radical, also supported by the results of reactions with 9,10-dihydroanthracene and PhSSPh. The cationic carbene complex shows electrophilic behavior toward nucleophiles such as NaH, ^pTolNHLi, PhONa, and PMe₃, resulting from an inversion of the electronic character of the Pd–C_carbene bond in [{PC(sp²)P}^tBuPd(PMe₃)]. The redox induced umpolung is reversible and unprecedented.     

Der thermische Zerfall des tBu2P?PP(Me)tBu2

The Thermal Decomposition of ^tBu₂P? P?P(Me)^tBu₂ The thermal decomposition of ^tBu₂P? P?P(Me)^tBu₂ 2 in C₆H₆ at 20°C is detectable after 10 h; ^tBu₂PMe, (^tBu₂P)₂PH and small amounts of the cyclotetraphosphanes P₄(P^tBu₂)₄ and P₄(P^tBu₂)₂ are formed. At 70°C (14 h) 83% of 2 are decomposed, and even 96% after 74 h. The main products are ^tBu₂PMe (68%) and P₄(P^tBu₂)₄ (20%). With 2,3-dimethyl-1,3-butadiene as a trapping reagent ^tBu₂PMe (62%) is still the main product, however, P₄(P^tBu₂)₄ is no longer found, but 1,2-bis(di-tert-butylphosphino)-4,5-dimethyl-1,2-diphosphacyclohexene-4 (22%) is formed instead. Also with cyclohexene ^tBu₂PMe (78%) remains the major product besides P₄(P^tBu₂)₄ (9%) and small amounts of the trapping product 7-di-tert-butylphosphino-7-phosphabicyclo[4.1.0]heptane. Thus, the thermal decomposition of 2 at 70°C proceeds very similar to that of ^tBu₂P? P?P(Br)^tBu₂ at ?30°C and starts yielding and the phosphinophosphinidene ^tBu₂P? P. In CH₂Cl₂ the decomposition of 2 includes the chlorination of the ylidic molecule.     

Complex formation reactions of two sterically hindered platinum(II) complexes with some N-bonding ligands

The kinetics of the complex formation reactions of two [(TL ^tBu)PtCl]⁺ and [Pt(tpdm)Cl]⁺ complexes (TL ^tBu = 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine and tpdm = terpyridinedimethane) with N-donor ligands, l-histidine (L-His), inosine (Ino), inosine-5′-monophosphate (5′-IMP) and guanosine-5′-monophosphate (5′-GMP), were studied. All reactions were studied under pseudo-first-order conditions as a function of nucleophile concentration and temperature in aqueous 0.1 M NaClO₄ solution in the presence of 10 mM NaCl using variable-temperature Uv–Vis spectrophotometry. The order of reactivity of the studied ligands is L-His > Ino > 5′-GMP > 5′-IMP. This order of reactivity is in relation to their electronic properties and structures. The mechanism of the substitution reactions is associative in nature as supported by the negative entropy of activation.