分子光化学贮存太阳能 Ⅲ.双环[2,2,1]-2,5-庚二烯的光诱导电子转移敏化异构化反应

以N,N,N′,N′-四甲基联苯二胺、2,6-二甲氧基萘和2,7-二甲氧基萘为光敏剂,在正己烷溶液中实现了双环[2,2,1]-2,5-庚二烯到四环[2,2,1,0^2,6,0^3,5]庚烷的异构化。测定了反应的量子产率。讨论了反应机理。通过激发态的光敏剂与二烯之间的电子转移反应,形成单重态和三重态处于平衡状态的离子自由基对中间体。处于溶剂笼中的三重态离子自由基对经电子反传,产生激发三重态二烯。最后该激发态二烯经分子内[2+2]环合加成反应异构化为四环烷。     

Forward and backward pericyclic photochemical reactions have intermediates in common, yet cyclobutenes break the rules.

Photochemical pericyclic reactions are believed to proceed via a so-called pericyclic minimum on the lowest excited potential surface (S(1)), which is common to both the forward and backward reactions. Such a common intermediate has never been directly detected. The photointerconversion of 1,3-butadiene and cyclobutene is the prevailing prototype for such reactions, yet only diene ring closure proceeds with the stereospecificity that the Woodward-Hoffmann rules predict. This contrast seems to exclude a common intermediate. Using ultrafast spectroscopy, we show that the excited states of two cyclobutene/diene isomeric pairs are linked by not one, but by two common minima, p* and ct*. Starting from the diene side (cyclohepta-1,3-diene and cycloocta-1,3-diene), electrocyclic ring closure passes via the pericyclic minimum p*, whereas ct* is mainly responsible for cis-trans isomerization. Starting from the corresponding cyclobutenes (bicyclo[3.2.0]heptene-6 and bicyclo[4.2.0]octene-7), the forbidden isomer is formed from ct*. The path branches at the first (S(2)/S(1)) conical intersection towards p* and ct*. The fact that the energetically unfavorable ct* path can compete is ascribed to a dynamic effect: the momentum in C=C twist direction, acquired--such as in other olefins--in the Franck-Condon region of the cyclobutenes.     

Quantum-Chemical Analysis of Electronic Excitation and Reactivity of Olefins and Dienes

Results obtained in studying the structure of olefin and diene molecules, and complexes of these, in the ground and lower excited states by RHF, ROHF, GVB/DN, and 6-31G^* quantum-chemical methods are presented. Attention is paid to the identity of the main structural and electronic parameters of triplet T ₁ and singlet S ₁ states forming a reactive fourfold spin-degenerate diradical equilibrium excited state (S·T)₁ having the lowest energy. A new mechanism of cyclodimerization of ethylene and tetrafluoroethylene and anionic polymerization of dienes, involving the (S·T)₁ states, is suggested.     

The di-π-methane rearrangement of systems with simple vinyl moieties : Mechanistic and exploratory organic photochemistry

3,3-Dimethyl-1,1-diphenyl-1,4-pentadiene and two 5-substituted derivatives were synthesized and studied. The regioselectivity, stereochemistry, quantum efficiency, multiplicity, and excited state reaction rates were studied in each case. The parent hydrocarbon, 5-MeO-derivative, and 5-cyano-diene—all rearranged on direct irradiation to give vinylcyclopropanes. The first compound led to 3,3-dimethyl-2,2-diphenyl-1-vinylcyclopropane. The second afforded 3,3-dimethyl-2,2-diphenyl-1-(2'-methoxyvinyl)cyclopropane. The last gave 1-cyano-3,3-dimethyl-2-(2',2'-diphenylvinyl)cyclopropane. Thus, the vinyl and methoxyvinyl groups survive in the products intact, while the cyanovinyl group is incorporated in the three-ring. In the two substituted dienes, cis-reactant gave cis-product and trans-reactant gave trans-product, both where the substituent was on the vinyl group of the product and where it became a ring substituent. The substituted di-π-methane systems underwent only cis-trans isomerization on sensitization, while the parent, unsubstituted diene led to di-π-methane product on sensitized as well as direct photolysis. While the quantum yields for the hydrocarbon diene were the same at room temperature for the direct and sensitized runs, only the sensitized runs showed a temperature dependence of efficiency with a dramatic, 5-fold increase on a 46° temperature increase. Thus, evidence was obtained for a singlet rearrangement in all cases and a triplet process only in the case of the unsubstituted diene. A sizable activation energy was seen for the triplet but not for the singlet. The room temperature quantum yields in the direct irradiations were: φ(parent diene)=0.011, φ(trans-methoxydiene)=0.051, φ(cis-methoxy-diene)= 0.050, φ(trans-cyanodiene)=0.36, and φ(cis-cyano-diene) = 0.20. A competing side reaction was cis-trans isomerization but these quantum yields were lower. Single photon counting was employed to obtain excited singlet reaction and decay rates at low temperature (i.e. 77°K) and the method of magic multipliers was used to obtain room temperature rates. These were: k_r(parent diene) = 4.7 × 10⁸ sec^?1, k_r(trans-cyano-diene)= 1.5 ×10¹⁰ sec^?1, k_r(cis-cyano-diene)= 8.0 × 10⁹sec^?1, and k_r(trans-methoxy-diene) = 1.9 × 10⁹ sec^?1. The results are discussed in terms of excited state molecular structure.An SCF-CI molecular orbital treatment of the reaction was developed. This used a cyclopropyldicarbinyl diradical species, with Walsh cyclopropane basis orbitals, as representing the half-reacted species. The energy of formation of this species from vertical excited state reactant was calculated for all three dienes and an excellent correlation with observed excited singlet rates was obtained. Similarly, dissection of the excited diradical energy into bond components led to a correlation between regioselectivity and weakness of the three-ring bond broken in the regioselectivity-determining step. Evidence was adduced for localization of the excitation energy in S₁ of reactant in the diphenylvinyl chromophore with migration of electronic excitation into the cyclopropyldicarbinyl diradical moiety during the vinyl-vinyl bridging process. A general method for quantitatively partitioning excitation energy was developed and applied to the case in hand. Finally, there was predicted a greater probability of di-π-methane three-ring fission in the excited state compared to the diradical ground state where Grob fragmentation proved energetically more favorable.     

Triplet acetylenes as synthetic equivalents of 1,2-bicarbenes: phantom n,pi state controls reactivity in triplet photocycloaddition

Diaryl acetylenes, in which one of the aryl groups is either a pyridine or a pyrazine, undergo efficient triplet state photocycloaddition to 1,4-cyclohexadiene with formation of 1,5-diaryl substituted tetracyclo[3.3.0.0(2,8).0(4,6)]octanes (homoquadricyclanes). In the case of pyrazinyl acetylenes, the primary homoquadricyclane products undergo a secondary photochemical rearangement leading to diaryl substituted tricyclo[3.2.1.0(4,6)]oct-2-enes. Mechanistic and photophysical studies suggest that photocycloaddition proceeds through an electrophilic triplet excited state whereas the subsequent rearrangement to the tricyclooctenes proceeds through a singlet excited state. Chemical and quantum yields for the cycloaddition, in general, correlate with the electron acceptor character of aryl substituents but are attenuated by photophysical factors, such as the competition between the conversion of acetylene singlet excited state into the reactive triplet excited states (intersystem crossing: ISC) and/or to the radical-anion (photoelectron transfer from the diene to the excited acetylene: PET). Dramatically enhanced ISC between pi-pi S(1) state and "phantom" n,pi triplet excited state is likely to be important in directing reactivity to the triplet pathway. The role of PET can be minimized by the judicious choice of reaction conditions (solvent, concentration, etc.). From a practical perspective, such reactions are interesting because "capping" of the triple bond with the polycyclic framework orients the terminal aryl (4-pyridyl, 4-tetrafluoropyridyl, phenyl, etc.) groups in an almost perfect 60 degrees angle and renders such molecules promising supramolecular building blocks, especially in the design of metal coordination polymers.     

Synthesis of 2,4-disubstituted 3-chlorofurans and the effect of the chlorine substituent in furan Diels-Alder reactions

2,4-Disubstituted 3-chlorofurans were synthesized in 42-69% overall yields by CuCl/bpy-catalyzed halogen atom transfer radical cyclization of 1-substituted 2,2,2-trichloroethyl allyl ethers to 2-substituted 3,3-dichloro-4-(1-chloroalkyl)tetrahydrofurans followed by base promoted dehydrochlorination. Diels-Alder reactions of 4-substituted 2-(2-furyl)-, 2-styryl-, and 2-crotyl-3-chlorofurans with dimethyl acetylenedicarboxylate occurred exclusively on the chlorofurano diene moieties and not on the non-chlorinated furano diene or the chlorinated exocyclic diene alternatives, demonstrating the predominance of the halogen effect in the furan Diels-Alder reaction.     

Strahlungschemie von Kohlenwasserstoffen. 15. Mitteilung. Energieübertragung im System Benzol–3-Phenylcyclohexadien-(1,4)

3-Phenylcyclohexa-1,4-diene, which is a reaction product in the benzene radiolysis, is decomposed when its solutions in benzene are irradiated by γ-rays. The main products are biphenyl (20%) and dihydrobenzene (10%). They show that hydrogen from phenylcyclohexadiene is transferred to benzene. The high G-value for the disappearance is explained by energy-transfer from a high-lying state of benzene, formed with g(B*) ≥ 2, to the diene. From the concentration dependence in the range 0.015–0.25 Mol/1 can be concluded that τ · k_tA is 21 1/Mole for phenylcyclohexadiene and 4 1/mole for cyclohexene, where τ is the lifetime of the excited state of benzene involved in the reaction and k_tA is the rate constant for energy-transfer from this excited state to the acceptor. This rate constant is in the same order of magnitude for biphenyl, naphthalene and cyclohexa-1,4-diene as accepted for phenylcyclohexadiene. The nature of the energy transfer from benzene to phenylcyclohexadiene is discussed. The possibilities of charge transfer or the lowest singlet- or tripletstate as excited states are ruled out.     

从轨道对称守恒原理看Diels-Alder反应区域选择性

根据轨道对称守恒原理(PCOS),推断出决定Diels-Alder反应的区域选择性的轨道相互作用是双烯体与亲双烯体各自最稳定的价轨道之间的相互作用,这种相互作用形成的是反应产物的两根新σ键中能量更低的σ键,即σ1键。在过渡态中具有更稳定的σ1键的那个区域异构体将是反应的优势产物,本文将这个规则称为σ1规则。本文的量子化学计算结果既证实了σ1规则预测Diels-Alder反应区域选择性主产物的正确性,也证实了σ1键的确来自于双烯体与亲双烯体各自最稳定的价轨道之间的相互作用。     

Stereochemistry of the formation of π-allylpalladium complexes from dialkylcyclohexa-1,3-dienes

1,4-Dimethyl-, 1-isopropyl-4-methyl- and 1-t-butyl-4-methylcyclohexa-1,3-diene reacted with a palladium salt to form, in each case, a single isomer of the corresponding π-allylpalladium chloride complexes, while 2-isopropyl-5-methylcyclohexa-1,3-diene gave two stereoisomeric complexes. An excess of diene (diene/Pd = 2.5–3.0) was required to produce a high yield of the complex. The hydrogen atom, which is incorporated onto the terminal carbon of the diene system, is shown (i) to come from the excess diene, which in turn is converted to an aromatic compound, and (ii) to attack the diene, stereo- and regio-selectively, from the same side as the palladium chloride portion.     

Excited state properties of alpha,omega-diphenylpolyenes: photophysical and photochemical studies of donor-acceptor diarylbutadienes

alpha,omega-Diphenylpolyenes have attracted a great deal of attention as models of retinyl polyenes that are related to natural photoreceptors involved in energy and sensory phototransductions. Of particular interest have been the topics of their excited state electronic structure and spectroscopic properties. However, the exact nature of the lowest excited state in terms of their structure and energetics is not clearly known. Examination of the photophysics and photochemistry of donor-acceptor diphenylpolyenes can aid in understanding the excited states and photoprocesses of linear polyenes. In this paper are described the absorption, fluorescence and photoisomerization studies of donor-acceptor diarylbutadienes, namely: p-(N,N-dimethylamino)-p'-cyano-1,4-diphenylbuta-1E,3E-diene (1), p-(N,N-dimethylamino)-p'-nitro-1,4-diphenylbuta-1E,3E-diene (2), p-(N,N-dimethylamino)-m'-nitro-1,4-diphenylbuta-1E,3E-diene (3), p-(N,N-dimethylamino)-o'-nitro-1,4-diphenylbuta-1E,3E-diene (4). Absorption properties are affected as expected due to mesomeric stabilization by the substituent; however, solvent polarity does not significantly affect the absorption properties of these dienes. In contrast, a pronounced solvatochromic fluorescence behavior of these dienes in organic solvents is observed. Time-resolved fluorescence is characterized by a single exponential fluorescence decay with generally increasing lifetime in polar solvents. The fluorescence quantum yields are very low, particularly in polar solvents, but do not show any clear trend. Irradiation of 1E,3E- 1-4 in organic solvents yields the corresponding 1E,3Z-isomer due to one-photon-one-bond isomerization of the C=C double bond lying closer to the acceptor group. The photoisomerization also depended on the solvent polarity and on the concentration of diene. The photoisomerization efficiency of dienes 1 and 2 under direct irradiation condition is greater than dienes 3 and 4. In comparison to the efficiency of photoisomerization under direct irradiation condition, the photosensitized isomerization efficiency is much less, particularly for dienes 1 and 2. The results are discussed in terms of the involvement of excited-state intramolecular charge transfer and conformationally relaxed polar excited states in the photoprocesses of linear polyenes.     

Photo retro-Diels-Alder reactions

Photo-retro-Diels-Alder (PrDA) reactions of a variety of Diels-Alder (DA) adducts were studied. Experimental results showed that the photoreactivity (quantum yield) depends on the electron-donating ability of the diene component and the electron-withdrawing ability of the dienophile component. The mechanism was studied by trapping the reaction intermediate, O(2) quenching, time-resolved absorption, and fluorescence spectroscopy. All the results support a mechanism that involves a charge-separated intermediate generated from a singlet excited state. The PrDA reaction may find applications in photoresponsive materials, photolithography, drug delivery, and mechanistic research.     

Anharmonic thermochemistry of cyclopentadiene derivatives

This paper focuses on the thermochemistry of some derivatives of cyclopenta‐1,3‐diene, namely, 5‐methylcyclopenta‐1,3‐diene, 5‐ethylcyclopenta‐1,3‐diene, 5‐formylcyclopenta‐1,3‐diene, 5‐methylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐ethylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐carbonylcyclopenta‐1,3‐diene radical, 1‐formylcyclopenta‐2,4‐diene‐1‐yl radical, 5‐methylenecyclopenta‐1,3‐diene radical, 5‐ethylidenecyclopenta‐1,3‐diene radical, and 3,6‐dimethylenecyclohexa‐1,4‐diene. Several different chemistries of these compounds are of interest in combustion modeling. Here, we present gas‐phase thermochemical properties for the above cited species, which are, except for 3,6‐dimethylenecyclohexa‐1,4‐diene, previously unknown. These were obtained from corrected (using bond additivity corrections) high‐level ab initio quantum chemistry calculations validated with well‐known compounds including cyclopentane, cyclopentene, cyclopenta‐1,3‐diene, and cyclopentadienyl radical. Heat capacities and entropies have been corrected for anharmonic molecular motions, in particular for internal rotations. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 453–463, 2003     

Combined NMR and quantum chemical studies on the interaction between trehalose and dienes relevant to the antioxidant function of trehalose

In a previous study (Oku, K.; Watanabe, H.; Kubota, M.; Fukuda, S.; Kurimoto, M.; Tujisaka, Y.; Komori, M.; Inoue, Y.; Sakurai, M. J. Am. Chem. Soc. 2003, 125, 12739), we investigated the mechanism of the antioxidant function of trehalose against unsaturated fatty acids (UFAs) and revealed that the key factor relevant to the function is the formation of OH...pi and CH...O hydrogen bonds between trehalose and the cis double bonds of the UFA. Here, we investigate whether such intriguing interactions also occur between this sugar and cis double bonds in other unsaturated compounds. For this purpose, we selected various diene compounds (1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, and 2,5-heptadiene) as interaction partners. All NMR experiments performed, including 1H-1H NOESY measurements, indicated that trehalose selectively interacts with the cis-olefin proton pair in the above diene with a 1:1 stoichiometry, and the C-3 (C-3') and C-6' (C-6) sites of the sugar are responsible for the interaction. Similar interactions were not observed for the mixtures of the diene and other saccharides (neotrehalose, kojibiose, nigerose, maltose, isomaltose, sucrose, maltitol, and sorbitol). Quantum chemical calculations revealed that the OH-3 and OH-6 groups bind to the olefin double bonds of the diene through OH...pi and CH...O types of hydrogen bonds, respectively, and the stabilization energy of the resulting complex is 5-6 kcal mol(-1). These results strongly support the above NMR results. Finally, the activation energies were calculated for the hydrogen abstraction reactions from the activated methylene group of heptadiene. In particular, when the reaction was initiated by a methyl radical, the activation energy was only 10 kcal mol(-1) for the free heptadiene, but on complexation with trehalose it drastically increased to ca. 40 kcal mol(-1). This indicates that trehalose has a significant depression effect on the oxidation of the diene compounds. These results strongly support the antioxidant mechanism deduced in the previous study and indicate that the formation of unique multiple hydrogen bonds between trehalose and cis-olefin bonds is rather a general event not confined to the case of UFA.     

Enantiospecific synthesis of the proposed structure of the antitubercular marine diterpenoid pseudopteroxazole: revision of stereochemistry.

An enantiospecific synthesis of structure 1, previously assigned to the antitubercular marine natural product pseudopteroxazole, has been accomplished as outlined in Scheme 1. Coupling of diene acid 3 and amino phenol 4 produced the amide 5, which was subjected to a novel oxidative intramolecular Diels-Alder reaction to generate the tricyclic lactam 6a stereoselectively. This product was transformed via intermediates 7-11 into the diene 13. Cationic cyclization of 13 afforded two diastereomeric tricyclic amphilectanes which were separated and transformed by parallel four-step sequences into 1 and 2, respectively. Neither 1 nor 2 were identical with pseudopteroxazole, indicating a need for revision of the structure, probably to 16.     

Biaxial ordering of terminal diene groups in lipid membranes: an infrared linear dichroism study

The molecular order within the hydrophobic core of membranes of the diene lipid di-tetradecadienoylphosphatidylcholine was studied by means of infrared spectroscopy on multibilayer assemblies which orient macroscopically on the surface of an attenuated total reflection crystal. The relative humidity and temperature were used as variable parameters to demonstrate that there were profound differences in the melting transition of lipids possessing predominantly cis and trans diene groups. The cis isomer undergoes the phase transition at a vapor pressure which is increased by 0.15 GPa when compared with that of the trans isomer. The methylene wagging band progression gives no indication of differences between the acyl chain conformation of the cis and trans forms in the gel state. The frequencies of a number of absorption bands of the diene groups reveal that these moieties are predominantly in the s-trans conformation to accommodate a favorable packing within the bilayer. The linear dichroism of selected in-plane and out-of-plane vibrations of the diene groups gives indications of the biaxial ordering of these moieties. We present the basic equations for the quantitative analysis of IR dichroism data of lamellar structures in terms of transverse and longitudinal molecular order parameters. It turns out that the planes of the rigid diene groups orient preferentially in a perpendicular direction with respect to the bilayer surface and parallel to each other forming in this way a layer of well-aligned diene groups in the bilayer center. This finding is confirmed by the results of X-ray measurements. We suggest that the partial interdigitation of the diene groups of the sn-1 acyl chains promotes the formation of the inverse H_II phase and/or enables the formation of covalent bonds between both the monolayers upon polymerization of diene lipids.     

Hexabromocyclopentadiene V. The Diels-Alder reaction of hexabromocyclopentadiene

The reactivity of hexabromocyclopentadiene (1) as a diene in the Diels-Alder reaction has been determined with a number of dienophiles. The results of the present study show that 1 behaves as an electron-poor diene in that cyclopentadiene is a more reactive dienophile than maleic anhydride. Qualitatively, 1 has been found to be a less reactive diene than hexachlorocyclopentadiene. Several new Diels-Alder adducts of 5,5-dibromo-1,2,3,4-tetrachlorocyclopentadiene are also reported.     

Radical Cyclization of Fluorinated 1,3‐Dicarbonyl Compounds with Dienes Using Manganese(III) Acetate and Synthesis of Fluoroacylated 4,5‐Dihydrofurans

Radical cyclizations of fluorinated 1,3‐dicarbonyl compounds with dienes mediated by Mn(OAc)₃ afforded 4,5‐dihydrofurans containing difluoroacetyl, trifluoroacetyl, or heptafluorobutanoyl groups in good‐to‐excellent yields. Additionally, 2‐(difluoromethyl)‐4,5‐dihydrofurans and a 4,7‐dihydrooxepin derivative were obtained as unexpected products in the reaction of 4,4‐difluoro‐1‐phenylbutane‐1,3‐dione with 1,3‐diphenylbuta‐1,3‐diene. The radical cyclization of symmetrical dienes such as 2,3‐dimethylbuta‐1,3‐diene and 1,4‐diphenylbuta‐1,3‐diene with 1,3‐diketones furnished the corresponding products in low yields. However, treatment of 1‐phenylbuta‐1,3‐diene with 1,3‐dicarbonyl compounds afforded 4,5‐dihydrofurans containing fluoroacyl groups. The radical cyclizations with 3‐methyl‐1‐phenylbuta‐1,3‐diene and 1,3‐diphenylbuta‐1,3‐diene led to 4,5‐dihydrofurans in good yields, since Me and Ph groups at C(3) of these dienes increase the stability of the radical intermediate.     

Synthesis and polymerization studies of 1,2-dimethyleneoctafluorocyclohexane

1,2-Dimethyleneoctafluorocyclohexane has been prepared by the pyrolysis of 2-chloro-methyl-1-methyloctafluorocyclohexane. Free radicals initiate the polymerization of the diene in both bulk and emulsion systems to give a highly crystalline (mp 214–218°C) polymer that has an all-cis 1,4-structure. The polymer is insoluble in common laboratory solvents, but will dissolve in perfluorokerosene above 175°C and in 2,5-dichlorobenzo-trifluoride above 150°C. This diene is not polymerized by cationic, anionic, or Ziegler-Natta catalysts. The diene is readily copolymerized with many common monomers to give soluble, high molecular weight polymers. Relative reactivity ratios have been measured with styrene by the Fineman and Ross method and Q–e parameters for the diene have been calculated.     

Theoretical Investigations on the Mechanism of Hetero‐Diels–Alder Reactions of Brassard’s Diene and 1, 3‐Butadiene Catalyzed by a Tridentate Schiff Base Titanium(IV) Complex

The mechanism of the hetero‐Diels–Alder reactions of Brassard’s diene and 1,3‐butadiene catalyzed by a titanium(IV) complex of a tridentate Schiff base was investigated by DFT and ONIOM methods. The calculations indicate that the mechanism of the reaction is closely related to the nucleophilicity–electrophilicity between diene and carbonyl substrates. A stepwise pathway is adopted for Brassard’s diene, and the step corresponding to the formation of the C? C bond is predicted to be the rate‐determining step with a free‐energy barrier of 8.4 kcal mol^?1. For 1,3‐butadiene, the reaction takes place along a one‐step, two‐stage pathway with a free‐energy barrier of 14.9 kcal mol^?1. For Brassard’s diene as substrate, the OCH₃ and OSi(CH₃)₃ substituents may play a key role in the formation of the transition state and zwitterionic intermediate by participating in charge transfer from Brassard’s diene to formaldehyde. The combination of the phenyl groups at the amino alcohol moiety and the ortho‐tert‐butyl group of the salicylaldehyde moiety in the chiral tridentate Schiff base ligand plays an important role in the control of the stereoselectivity, which is in agreement with experimental observations.     

Synthesis and characterization of [(diene)Rh[mu-OSi(OtBu)3]]2, a precursor to silica-bound rhodium

Reaction of [(diene)RhCl]2 with 2 equiv of KOSi(OtBu)3 afforded [(diene)Rh[mu-OSi(OtBu)3]]2, where diene=cod (1) and nbd (2). Multinuclear NMR studies reveal that 1 and 2 have a dimeric structure with bridging tris(tert-butoxy)siloxy ligands. These dimers are folded along the O...O axis. Complexes and reacted with PR3(R=Me, Ph) to give monomeric products, the formulae of which depend on the amount of PR3 added ((diene)Rh[OSi(OtBu)3](PR3) and Rh[OSi(OtBu)3](PMe3)3). The behavior of 1 towards water and methanol is discussed. Thermogravimetric analyses (TGAs) of 1 and 2 reveal rather sharp conversions to rhodium-containing materials. Thermolysis of 1 in toluene at 180 degrees C resulted in formation of a black precipitate, which contained rhodium nanoparticles with an average diameter of 22 nm, as determined by powder X-ray diffraction (PXRD), after calcination at 300 degrees C for 1 h.