Tert-butylethylene Research Articles

Dispersant and Protective Roles of Amphiphilic Poly(ethylene phosphate) Block Copolymers in Polyester/Bone Mineral Composites.

Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial β-tricalcium phosphate (βTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.

Low-Temperature Dehydrogenation of Cyclooctane by Using Pincer Iridium Complexes Bearing an N,N′-Diarylated PNCNP Ligand

PNCNP pincer iridium complexes possessing arylnitrene linkers (−N(Ar)−) catalyze transfer dehydrogenation of cyclooctane (COA) under low-temperature conditions, giving 200 turnovers at 125 °C using tert-butylethylene (TBE) and 60 turnovers at 50 °C using cyclohexene (CHE) as a sacrificial hydrogen acceptor. Despite prior reports dealing with the synthetic difficulty of pincer iridium complexes bearing di(isopropyl)phosphoramine sidearms, our design using chemically inert (3,5-disubstituted-aryl)nitrene linkers allowed for the successful complexation with iridium. The structural characterization and computational study revealed that steric congestion provided by arylnitrene linkers destabilizes the resting internal alkene adducts, thereby reducing the overall activation barrier of the rate-limiting C–H addition. The steric congestion also hinders undesirable disproportionation of CHE, allowing for its use as an effective hydrogen acceptor. With their straightforward synthesis coupled with fine tunability through the 3,5-substituents on the aryl groups, the N,N′-diarylated PNCNP ligands presented in this work will be a valuable addition to the highly successful PCP pincer framework.

The effect of alkylation on the micro-solvation of ethers revealed by highly localized water librational motion.

The specific far-infrared spectral signatures associated with highly localized large-amplitude out-of-plane librational motion of water molecules have recently been demonstrated to provide sensitive spectroscopic probes for the micro-solvation of organic molecules [Mihrin et al., Phys. Chem. Chem. Phys. 21(4), 1717 (2019)]. The present work employs this direct far-infrared spectroscopic approach to investigate the non-covalent intermolecular forces involved in the micro-solvation of a selection of seven ether molecules with systematically varied alkyl substituents: dimethyl ether, diethyl ether, diisopropyl ether, ethyl methyl ether, t-butyl methyl ether, and t-butyl ethyl ether. The ranking of the observed out-of-plane water librational band signatures for this selected series of ether-water complexes embedded in inert neon matrices at 4K reveals information about the interplay of directional intermolecular hydrogen bond motifs and non-directional and long-range dispersion interactions for the micro-solvated structures. These far-infrared observables differentiate minor subtle effects introduced by specific alkyl substituents and serve as rigorous experimental benchmarks for modern quantum chemical methodologies of various levels of scalability, which often fail to accurately predict the structural variations and corresponding vibrational signatures of the closely related systems. The accurate interaction energies of the series of ether-water complexes have been predicted by the domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations, followed by a local energy decomposition analysis of the energy components. In some cases, the secondary dispersion forces are in direct competition with the primary intermolecular hydrogen bonds as witnessed by the specific out-of-plane librational signatures.

Synthesis in aqueous media of poly(ethylene phosphoric acids) by mild thermolysis of homopolymers and block copolymers based on tert-butyl ethylene phosphate

Poly(ethylene phosphoric acid)s (PEPA)s of different compositions, namely homopolymers, and diblock and triblock copolymers containing poly(ethylene glycol) monomethyl ether, l-lactide, and ε-caprolactone blocks, can be quantitatively obtained by mild thermolysis of polymers based on tert-butyl ethylene phosphate in aqueous media at 80 °C. Thermolysis of poly(tert-butyl ethylene phosphate) in the presence of sodium acetate gave a PEPA with a narrow molecular weight distribution (Ð = 1.10). The salt-like reaction product can be concentrated without the formation of three-dimensional gels. All starting poly(tert-butyl ethylene phosphate) containing homopolymers and block copolymers were effectively prepared with phenolate–Mg catalysts, i.e., [(BHT)MgBu(THF)]2 and [(BHT)Mg(OBn)(THF)]2 (BHT = 2,6-di-tert-butyl-4-methylphenolate). In the synthesis of polyphosphate–polyester block copolymers, the polyphosphate macromonomer inhibits further polymerization of ε-caprolactone. We therefore failed to obtain a copolymer BnO(tBuOEP)n-b-(εCL)mH using a coordination Mg catalyst.

Hydroperoxide Formation and Thermal Stability of Ethyl t-Butyl Ether Oxidation

A customer-designed mini closed pressure vessel test (MCPVT) consisting of a pressure sensor and a temperature sensor connected to recorder was applied to evaluate the isothermal stability along with the formation of hydroperoxide in the ethyl t-butyl ether (ETBE) oxidation process at low temperatures. A new type of hydroperoxide, named 1-tert-butoxy-ethyl hydroperoxide (TBEHP), was separated from ETBE oxidation products via column chromatography, which was further characterized by mass spectrometry (MS), 1H and 13C nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR). The thermal characteristics of TBEHP were assessed via differential scanning calorimetry (DSC). Results showed that the exothermic onset temperature (T0) and thermal decomposition heat (QDSC) of TBEHP were 99.12 °C and 1523.89 J·g–1, respectively. Moreover, a jet-stirred reactor (vessel volume: 500 mL) was used to evaluate the explosive risk of ETBE oxidation. The corresponding result indicated that detonatio...

High yields of piperylene in the transfer dehydrogenation of pentane catalyzed by pincer-ligated iridium complexes

Conjugated dienes are desirable reagents for several important applications. We report that sterically uncrowded PCP-pincer iridium complexes, including precursors of (iPr4PCP)Ir and (Me2tBu2PCP)Ir, catalyze the transfer dehydrogenation of pentane, using high concentrations of t‐butylethylene (TBE) as hydrogen acceptor, to give high yields of 1,3-pentadiene (piperylene). Piperylene yields are ca. 100-fold greater than those obtained with the more widely used di(t‐butyl)phosphino substituted pincer iridium catalysts. This represents, to our knowledge, the first reported high-yield synthesis of dienes via the dehydrogenation of n-alkane using molecular catalysts. To our knowledge, this is the first reported high-yield synthesis of dienes achieved via the dehydrogenation of n-alkane using molecular catalysts.

High-Turnover Aromatic C-H Borylation Catalyzed by POCOP-Type Pincer Complexes of Iridium.

The catalytic C-H borylation of arenes with HBpin (pin = pinacolate) using POCOP-type pincer complexes of Ir has been demonstrated, with turnover numbers exceeding 10 000 in some cases. The selectivity of C-H activation was based on steric preferences and largely mirrored that found in other Ir borylation catalysts. Catalysis in the (POCOP)Ir system depends on the presence of stoichiometric quantities of sacrificial olefin, which is hydrogenated to consume the H2 equivalents generated in the borylation of C-H bonds with HBpin. Smaller olefins such as ethylene or 1-hexene were more advantageous to catalysis than sterically encumbered tert-butylethylene (TBE). Olefin hydroboration is a competing side reaction. The synthesis and isolation of multiple complexes potentially relevant to catalysis permitted examination of several key elementary reactions. These experiments indicate that the C-H activation step in catalysis ostensibly involves oxidative addition of an aromatic C-H bond to the three-coordinate (POCOP)Ir species. The olefin is mechanistically critical to gain access to this 14-electron, monovalent Ir intermediate. C-H activation at Ir(I) here is in contrast to the olefin-free catalysis with state-of-the-art Ir complexes supported by neutral bidentate ligands, where the C-H activating step is understood to involve trivalent Ir-boryl intermediates.

Catalytic alkane transfer-dehydrogenation by PSCOP iridium pincer complexes

A series of new (tBu2PSCOPR2)IrHCl iridium complexes with ‘hybrid’ phosphinothious-phosphinite PSCOP ligands ([tBu2PSCOPR2=1-(SPtBu2)-3-(OPR2)-C6H4], R=tBu, 4a, R=Cy, 4b, R=iPr, 4c, and R=Et, 4d) have been synthesized and characterized. Treatment of complexes 4a–d with sodium tert-butoxide generates the active species for catalytic transfer-dehydrogenation of cyclooctane (COA) or n-octane using tert-butylethylene (TBE) as hydrogen acceptor to form cyclooctene (COE) or octenes, respectively. The catalytic activity of these complexes and the product selectivity in alkane dehydrogenation is greatly influenced by the steric properties of the pincer ligand. In general, the less sterically bulky complex exhibits higher catalytic activity than the more hindered complex. Among the new (PSCOP)Ir-type complexes, the least crowded complex (tBu2PSCOPEt2)IrHCl 4d is most active for n-octane/TBE transfer-dehydrogenation. The relatively crowded, less active, complexes (tBu2PSCOPtBu2)IrHCl (4a) and (tBu2PSCOPCy2)IrHCl (4b) exhibit high regioselectivity for α-olefin formation at the early stages of the reaction.

7-6-7 Ring-based transition-metal catalysts for the transfer dehydrogenation of isopropanol

A family of 7-6-7 ring-based PCP pincer iridium/rhodium complexes has been applied to the transfer dehydrogenation of isopropanol to give acetone using tert-butylethylene (TBE) as the hydrogen acceptor. For the iridium complexes, high initial activity was achieved with the turnover number (TON) being as high as 6000 after 2 h at 200 °C, even when TBE was present in high concentration (6000 equivalents). The inhibition effect of TBE was found to be somewhat weaker than in the case of alkane dehydrogenation using the same catalysts. Whereas the corresponding rhodium complex was inactive in alkane dehydrogenation, it was unexpectedly found to have a catalytic activity of 2000 TONs (3000/1 TBE/catalyst ratio) after 2 h at 200 °C in the same transfer dehydrogenation. The bonding properties of the reactive complexes were investigated through natural bond orbital (NBO) analysis and compared.

Physicochemical Properties and Catalytic Performance of Sulphonic Resins of Various Morphological Types in Ethyl t-Butyl Ether Synthesis

Physicochemical and catalytic properties of sulphonic resins of various morphological types in ethyl t-butyl ether synthesis were studied. We have found that the turnover frequency (TOF) of sulphonated cation-exchange resins reflects the effect of morphology expressed in terms of fractal geometry. The correlation between the catalytic activity of various types of sulphonated resins and their fractal dimension was established. Difference in observed TOF of sulphonic resins of various morphological types is caused by various accessibilities of acid sites. Catalysts of more ordered structure (characterized by smaller fractal dimension) provide the best conditions for the adsorption–desorption of reactants and products resulting in large values of TOF.

Atmospheric oxidation of methyl and ethyl tert-butyl ethers initiated by hydroxyl radicals. A quantum chemistry study

Abstract In this work, a systematic investigation on the reactions of methyl t-butyl ether (MTBE) and ethyl t-butyl ether (ETBE) with OH radicals in the gas phase has been performed, within the Density Functional (DFT) framework. The potential energy surfaces were obtained at the M06-2X/6-311++G(d,p) level. Specific emphasis was given to obtain kinetic data for MTBE and ETBE oxidative degradation and to identify and quantify the intermediate products formed. The values of the calculated rate constants reproduce remarkably well the available experimental data. The calculated total rate constants for the MTBE + OH and ETBE + OH reactions, in the gas phase at 298.15 K, are 2.79 × 10−12 and 7.38 × 10−12 cm3 molecules−1 s−1. Thus, ETBE reacts more than 2 times faster with OH radicals than MTBE. In both molecules, the hydrogen atoms that are most easily abstracted are the ones occupying an α position with respect to the ether oxygen atom. The contribution of the reaction channels involving H-abstraction from the tert-butyl group amounts to about 24–27% of the total rate coefficient. The results obtained in this work may improve the reliability and precision of the OH radical kinetic data required to predict the lifetime of aliphatic ethers and their contribution to urban and regional pollution.

Synthesis, Characterization, and Dehydrogenation Activity of an Iridium Arsenic Based Pincer Catalyst

A new arsenic-based pincer (AsOCOAs) dehydrogenation catalyst has been synthesized, IrHCl{2,6-C6H3-(O-AsBut2)} (3). Treatment with an equivalent of base (NaO-tert-butoxide) under an atmosphere of hydrogen gas affords the dihydride catalyst IrH2{2,6-C6H3-(O-AsBut2)} (4). The activity of 3 was explored under transfer dehydrogenation conditions with cyclooctane and tert-butyl ethylene, giving a maximum turnover number of 960 at 175 °C in 24 h. Acceptorless dehydrogenations were also explored with pyrrolidine-based molecules, ethylperhydrocarbazole (5), methylperhydroindole (6), and butylpyrrolidine (7), in which all results indicate 3 is roughly half as active as the analogous phosphine-based pincer catalyst 2. Akin to the phosphine pincer catalysts the activity was seen to steadily improve with increasing temperature, peaking at 175 °C, upon which thermal decomposition sets in.

Health assessment of gasoline and fuel oxygenate vapors: Subchronic inhalation toxicity

Sprague Dawley rats were exposed via inhalation to vapor condensates of either gasoline or gasoline combined with various fuel oxygenates to assess whether their use in gasoline influences the hazard of evaporative emissions. Test substances included vapor condensates prepared from an EPA described “baseline gasoline” (BGVC), or gasoline combined with methyl tertiary butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA). Target concentrations were 0, 2000, 10,000 or 20,000mg/m3 and exposures were for 6h/day, 5days/week for 13weeks. A portion of the animals were maintained for a four week recovery period to determine the reversibility of potential adverse effects. Increased kidney weight and light hydrocarbon nephropathy (LHN) were observed in treated male rats in all studies which were reversible or nearly reversible after 4weeks recovery. LHN is unique to male rats and is not relevant to human toxicity. The no observed effect level (NOAEL) in all studies was 10,000mg/m3, except for G/MTBE (<2000) and G/TBA (2000). The results provide evidence that use of the studied oxygenates are unlikely to increase the hazard of evaporative emissions during refueling, compared to those from gasoline alone.

Health assessment of gasoline and fuel oxygenate vapors: Neurotoxicity evaluation

Sprague–Dawley rats were exposed via inhalation to vapor condensates of either gasoline or gasoline combined with various fuel oxygenates to assess potential neurotoxicity of evaporative emissions. Test articles included vapor condensates prepared from “baseline gasoline” (BGVC), or gasoline combined with methyl tertiary butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA). Target concentrations were 0, 2000, 10,000 or 20,000mg/mg3 and exposures were for 6h/day, 5days/week for 13weeks. The functional observation battery (FOB) with the addition of motor activity (MA) testing, hematoxylin and eosin staining of brain tissue sections, and brain regional analysis of glial fibrillary acidic protein (GFAP) were used to assess behavioral changes, traditional neuropathology and astrogliosis, respectively. FOB and MA data for all agents, except G/TBA, were negative. G/TBA behavioral effects resolved during recovery. Neuropathology was negative for all groups. Analyses of GFAP revealed increases in multiplebrain regions largely limited to males of the G/EtOH group, findings indicative of minor gliosis, most significantly in the cerebellum. Small changes (both increases and decreases) in GFAP were observed for other test agents but effects were not consistent across sex, brain region or exposure concentration.

Health assessment of gasoline and fuel oxygenate vapors: Developmental toxicity in rats

Gasoline-vapor condensate (BGVC) or condensed vapors from gasoline blended with methyl t-butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME) diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA) were evaluated for developmental toxicity in Sprague–Dawley rats exposed via inhalation on gestation days (GD) 5–20 for 6h/day at levels of 0 (control filtered air), 2000, 10,000, and 20,000mg/m3. These exposure durations and levels substantially exceed typical consumer exposure during refueling (<1–7mg/m3, 5min). Dose responsive maternal effects were reduced maternal body weight and/or weight change, and/or reduced food consumption. No significant malformations were seen in any study. Developmental effects occurred at 20,000mg/m3 of G/TAME (reduced fetal body weight, increased incidence of stunted fetuses), G/TBA (reduced fetal body weight, increased skeletal variants) and G/DIPE (reduced fetal weight) resulting in developmental NOAEL of 10,000mg/m3 for these materials. Developmental NOAELs for other materials were 20,000mg/m3 as no developmental toxicity was induced in those studies. Developmental NOAELs were equal to or greater than the concurrent maternal NOAELs which ranged from 2000 to 20,000mg/m3. There were no clear cut differences in developmental toxicity between vapors of gasoline and gasoline blended with the ether or alcohol oxygenates.

Health assessment of gasoline and fuel oxygenate vapors: Reproductive toxicity assessment

Vapor condensates of baseline gasoline (BGVC), or gasoline-blended with methyl tertiary butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA) were evaluated for reproductive toxicity in rats at target concentrations of 2000, 10,000, or 20,000mg/m3, 6h/day, 7days/week. BGVC and G/MTBE were assessed over two generations, the others for one generation. BGVC and G/MTBE F1 offspring were evaluated for neuropathology and changes in regional brain glial fibrillary acidic protein content. No neurotoxicity was observed. Male kidney weight was increased consistent with light hydrocarbon nephropathy. In adult rats, decreased body weight gain and increased liver weight were seen. Spleen weight decreased in adults and pups exposed to G/TBA. No pathological changes to reproductive organs occurred in any study. Decreased food consumption was seen in G/TAME lactating females. Transient decreases in G/TAME offspring weights were observed during lactation. Except for a minor increase in time to mating in G/TBA which did not affect other reproductive parameters, there were no adverse reproductive findings. The NOAEL for reproductive and offspring parameters was 20,000mg/m3 for all vapor condensates except for lower offspring NOAELs of 10,000mg/m3 for G/TBA and 2000mg/m3 for G/TAME.

Health assessment of gasoline and fuel oxygenate vapors: Immunotoxicity evaluation

Female Sprague Dawley rats were exposed via inhalation to vapor condensates of either gasoline or gasoline combined with various fuel oxygenates to assess potential immunotoxicity of evaporative emissions. Test articles included vapor condensates prepared from “baseline gasoline” (BGVC), or gasoline combined with methyl tertiary butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA). Target concentrations were 0, 2000, 10,000 or 20,000mg/mg3 administered for 6h/day, 5days/week for 4weeks. The antibody-forming cell (AFC) response to the T-dependent antigen, sheep erythrocyte (sRBC), was used to determine the effects of the gasoline vapor condensates on the humoral components of the immune system. Exposure to BGVC, G/MTBE, G/TAME, and G/TBA did not result in significant changes in the IgM AFC response to sRBC, when evaluated as either specific activity (AFC/106 spleen cells) or as total spleen activity (AFC/spleen). Exposure to G/EtOH and G/DIPE resulted in a dose-dependent decrease in the AFC response, reaching the level of statistical significance only at the high 20,000mg/m3 level. Exposure to G/ETBE resulted in a statistically significant decrease in the AFC response at the middle (10,000mg/m3) and high (20,000mg/m3) exposure concentrations.

An Efficient Large-Scale Synthesis of a Naphthylacetic Acid CRTH2 Receptor Antagonist

An efficient and practical synthesis of a naphthylacetic acid CRTH2 receptor antagonist is reported. Michael addition of ethyl t-butyl malonate to an allenoate afforded a triester, which was selectively hydrolyzed and decarboxylated to give a benzylidenepentanedioic acid monoester. Treatment of this compound with potassium acetate and acetic anhydride produced the naphthylacetate core. The triflate of the key building block was coupled with a zinc reagent of the side chain under improved Negishi coupling conditions to afford the target product. The process was successfully scaled up to produce over 2 kg of the API.

On the Mechanism of the Dehydroaromatization of Hexane to Benzene by an Iridium Pincer Catalyst

The developments in the area of transition-metal pincer complexes have opened up new avenues for conversion of saturated hydrocarbons to more useful aromatic compounds under homogeneous reaction conditions. In the backdrop of an interesting series of conversions of unbranched alkanes to benzene, toluene, and xylene (known as the BTX family aromatics) reported by Goldman and co-workers (Nature Chem. 2011, 3, 167), we herein present a comprehensive mechanistic picture obtained by using density functional computations. The reaction involves an iridium-PCP-pincer-catalyzed dehydroaromatization of hexane to benzene (in which PCP=η(3) -C6 H3 (iPrP)2 -1,3) by using tert-butylethylene (TBE) as a sacrificial acceptor. The most energetically preferred pathway for a sequence of dehydrogenations is identified to begin with a terminal CH bond activation of n-hexane leading to the formation of hex-1-ene. Although the initial dehydrogenation of n-hexane was found to be endergonic, the accompanying exoergic hydrogenation of TBE to tert-butylethane (TBA) compensates the energetics to keep the catalytic cycle efficient. Subsequent dehydrogenations provide a hexa-1,3-diene and then a hexa-1,3,5-triene. The pincer bound triene is identified to undergo cyclization to furnish cyclohexadiene. Eventually, dehydrogenation of cyclohexa-1,3-diene offers benzene. In the most preferred pathway, the Gibbs free energy barrier for cyclization leading to the formation of cyclohexa-1,3-diene is found to exhibit the highest barrier (21.7 kcal mol(-1) ).

The Role of Group 14 Element Hydrides in the Activation of C–H Bonds in Cyclic Olefins

Formally, triple-bonded dimetallynes ArEEAr [E = Ge (1), Sn (2); Ar = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)] have been previously shown to activate aliphatic, allylic C-H bonds in cyclic olefins, cyclopentadiene (CpH), cyclopentene (c-C(5)H(8)) and 1,4-cyclohexadiene, with intriguing selectivity. In the case of the five-membered carbocycles, cyclopentadienyl species ArECp [E = Ge (3), Sn (4)] are formed. In this study, we examine the mechanisms for activation of CpH and c-C(5)H(8) using experimental methods and describe a new product found from the reaction between 1 and c-C(5)H(8), an asymmetrically substituted digermene ArGe(H)Ge(c-C(5)H(9))Ar (5), crystallized in 46% yield. This compound contains a hydrogenated cyclopentyl moiety and is found to be produced in a 3:2 ratio with 3, explaining the fate of the liberated H atoms following triple C-H activation. We show that when these C-H activation reactions are carried out in the presence of tert-butyl ethylene (excess), compounds {ArE(CH(2)CH(2)tBu)}(2) [E = Ge(8), Sn(9)] are obtained in addition to ArECp; in the case of CpH, the neohexyl complexes replace the production of H(2) gas, and for c-C(5)H(8) they displace cyclopentyl product 5 and account for all the hydrogen removed in the dehydroaromatization reactions. To confirm the source of 8 and 9, it was demonstrated that these molecules are formed cleanly between the reaction of (ArEH)(2) [E = Ge(6), Sn(7)] and tert-butyl ethylene, new examples of noncatalyzed hydro-germylation and -stannylation. Therefore, the presence of transient hydrides of the type 6 and 7 can be surmised to be reactive intermediates in the production of 3 and 4, along with H(2), from 1 and 2 and CpH (respectively), or the formation of 3 and 5 from 1. The reaction of 6 or 7 with CpH gave 3 or 4, respectively, with concomitant H(2) evolution, demonstrating the basic nature of these low-valent group 14 element hydrides and their key role in the 'cascade' of C-H activation steps. Additionally, during the course of these studies a new polycyclic compound (ArGe)(2)(C(7)H(12)) (10) was obtained in 60% yield from the reaction of 1,6-heptadiene and 1 via double [2 + 2] cycloaddition and gives evidence for a nonradical mechanism for these types of reactions.