Showing papers on "Norbornadiene published in 2006"

Synthesis of fluoranthenes and indenocorannulenes: elucidation of chiral stereoisomers on the basis of static molecular bowls.

Abstract: Cycloaromatization of a peri diyne with an external alkyne provides a general route to indeno-fused polynuclear aromatics. Fluoranthenes 9 (or 13) are easily accessible in good to excellent yields (75-99%; 18 examples) from the reaction of symmetric (or asymmetric) diynes 4 and alkynes 5 (or norbornadiene) in the presence of Wilkinson's catalyst. This formal [(2+2)+2] cycloaddition can also be applied to generate various indenocorannulenes 28 from 2,3-diethynylcorannulene derivatives 27 and alkynes 5. The indenocorannulenes 28 exist in a static bowl form at room temperature with bowl-to-bowl inversion barriers higher than 24 kcal/mol. This barrier renders the rate of inversion slow enough at room temperature to establish a class of chiral, bowl-shaped stereoiomers containing no tetrahedrally ligated atoms. The crystal structure of 28g provides insight into the bowl-shaped geometry of these compounds. This new synthetic method occurs under neutral conditions and tolerates various functional groups (e.g., alkyl, aryl, alcohols, and esters).

Arylcyanation of Norbornene and Norbornadiene Catalyzed by Nickel

Abstract: Aryl cyanides add to norbornene and norbornadiene under nickel catalysis to give (2R*,3S*)-3-aryl-2-cyanobicyclo[2.2.1]heptanes and (2R*,3S*)-3-aryl-2-cyanobicyclo[2.2.1]hept-5-enes in good yields ...

A High-Spin and Helical Organic Polymer: Poly{[4-(dianisylaminium)phenyl]acetylene}

Abstract: A high-spin polyradical, poly{[4-(dianisylaminium)phenyl]acetylene} 1+, was synthesized as a π-conjugated polymer with an excess of the one-handed helical structure bearing stable aminium cation radicals. [4-(Dianisylamino)phenyl]acetylene (3) was synthesized and polymerized using [Rh(norbornadiene)Cl]2 in (R)-1-phenylethylamine, (S)-1-phenylethylamine, or triethylamine to produce the corresponding poly{[4-(dianisylamino)phenyl]acetylene} 1 (1(R)-PEA, 1(S)-PEA, and 1TEA). The positive and negative Cotton effects were observed at 270−450 nm for the polymers 1(R)-PEA and 1(S)-PEA, indicating that an excess of the one-handed helical polyacetylene backbone was induced by the polymerization using chiral solvents despite the achiral monomer. The oxidation of 1 with NOPF6 gave the corresponding aminium polyradicals 1+, and the circular dichroism (CD) spectrum was observed even after the oxidation of the helical polyradical 1(R)-PEA+. The SQUID and NMR shift measurements indicated a high-spin state of the polyrad...

SPANphos: trans-spanning diphosphines as cis chelating ligands!

Abstract: Several SPANphos ligands based on a spirobichroman backbone, introduced as a putative trans ligand, form compounds of the type [Rh(nbd)(SPANphos)]BF4 (1–6) in which both norbornadiene and SPANphos act as cis chelating ligands. The cyclooctadiene rhodium chloride derivatives form bimetallic complexes. Crystal structures for several of these compounds and free ligands are reported. Semiemperical AM1 and DFT calculations show that spirobichroman can assume several conformations, some of which are suitable for the formation of cis chelating SPANphos. All calculations on SPANphos complexes of PdCl2, PtCl2 and Rh(CO)Cl show that the trans complex is more stable by 4–10 kcal mol−1. The cis conformation in 1–6 is enforced by the cis chelating norbornadiene ligand.

Novel materials for large change in refractive index : Synthesis and photochemical reaction of the ladderlike poly(silsesquioxane) containing norbornadiene, azobenzene, and anthracene groups in the side chains

Abstract: We succeeded in the synthesis of certain poly(silsesquioxane)s (poly(SCC)) with excellent refractive indices properties, which have pendant norbornadiene (NBD), azobenzene (AZ), and anthracene (AT) moieties. The photochemical reactions of the obtained poly(SCC) derivatives were examined in the film state upon UV irradiation, and it was found that poly(SCC) derivatives with NBD groups, AZ groups, and AT groups had large change in values of the refractive index (ΔnD's) before and after photoirradiation which were in the range of 0.050−0.073, 0.007−0.009, and 0.094−0.116, respectively.

Study on the reactivity of the alkyne component in ruthenium-catalyzed [2 + 2] cycloadditions between an alkene and an alkyne.

Abstract: The ruthenium-catalyzed [2 + 2] cycloadditions of norbornadiene with a variety of alkynes have been investigated. Electronic effect of the alkyne component has shown to play an important role on the rate of the cycloaddition, and the reactivity of the alkyne component increases dramatically as the alkyne becomes more electron deficient. Increase in the steric bulk of the alkyne component decreases the reactivity of the alkyne component. It was also found that chelation effect of propargylic alcohols greatly enhanced the reactivity of the alkyne component in the ruthenium-catalyzed [2 + 2] cycloadditions.

Hepta-coordinate halocarbonyl molybdenum(II) and tungsten(II) complexes as heterogeneous polymerization catalysts

Abstract: [MX 2 (CO) 3 (DAB)] (M = Mo, W; X = I, Br) ( 5 – 8 ) complexes bearing the 1,4-diazobutadiene (DAB) ligand RN C(Ph) C(Ph) NR [R = (CH 2 ) 3 Si(OEt) 3 ] were immobilized in MCM-41 mesoporous silica. The tethering, stepwise procedure started with treatment of the MCM-41 mesoporous material with a toluene solution of the 1,4-diazobutadiene ligand, under reflux. The molybdenum and tungsten organometallic cores were subsequently introduced into the ligand-silicas by pore volume impregnation of a solution of the complexes [MX 2 (CO) 3 (NCMe) 2 ] (M = Mo, W; X = Br, I). The modified materials were extensively characterized by several techniques, such as FTIR, solid-state MAS and CP MAS NMR ( 13 C, 29 Si), powder XRD, and nitrogen adsorption–desorption measurements. These new materials (containing 2.6–2.9 wt.% Mo or 0.4–0.6 wt.% W) catalyze the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene at 328 K, in contrast with the very low activity exhibited by the precursor complexes and with their behavior at lower temperature. Addition of AlCl 3 as a co-catalyst enhanced the catalytic performance of the material MCM-DAB-MoBr 2 ( 12 ) in the ROMP of NBE.

Synthesis of Isoxazolino Norbornene Derivatives Containing Sugar Residues by 1,3-Dipolar Cycloaddition and Their Application to the Synthesis of Neoglycopolymers by Living Ring-Opening Metathesis Polymerization

Abstract: The in situ generation and subsequent cycloaddition of glycosyl nitrile oxides to norbornadiene (NBD) afforded monomeric isoxazolino norbomenes bearing xylose, glucose, and mannose residues in high yields. Ring-opening metathesis polymerization (ROMP) of the norbomene derivatives containing acetyl-protected sugar residues initiated by Ru(CHPh)(Cl) 2 (PCy 3 ) 2 (1) and Mo(CHCMe2Ph)(N-2,6-'Pr2C6H3)(O t Bu)2 (3) proceeded in a living manner with quantitative initiation, affording polymers with narrow molecular weight distributions (M w / M n = 1.11-1.35). The living nature of this polymerization by 1 was further demonstrated by the preparation of diblock copolymers in a precise manner by the sequential polymerization of norbomene and its carbohydrate derivatives. Polymers bearing multiple sugar units bearing free sugars were prepared by the deacetylation of the glycopolymers under basic conditions, and olefinic double bonds in these ROMP polymers were hydrogenated exclusively by p-toluenesulfonhydrazide in chlorobenzene without cleavage of the sugar functionality.

Conversion of intramolecular singlet electron transfer at room temperature into triplet energy transfer at 77 K: photoisomerization in norbornadiene- and carbazole-labeled poly(aryl ether) dendrimers.

Abstract: A series of Frechet-type poly(aryl ether) dendrimers (CZ-Gn-NBD, n = 1-3) with carbazole (CZ) chromophores and a norbornadiene (NBD) group attached to the periphery and the core, respectively, were synthesized, and their photophysical and photochemical properties were investigated. Selective excitation of the carbazole units in CZ-Gn-NBD resulted in a singlet electron transfer from CZ to NBD at room temperature, and an intersystem crossing followed a triplet-triplet energy transfer from CZ to NBD in glassy 2-methyltetrahydrofuran at 77 K. Both singlet electron transfer and triplet energy transfer processes lead to the isomerization of the norbornadiene group into the quadricyclane (CZ-Gn-QC). The efficiencies and the rate constants for singlet electron transfer are approximately 88, 80, and 74% and 1.8 x 10(9), 6.1 x 10(8), and 4.0 x 10(8) s(-1) for generations 1-3, respectively. The quantum yields of the intramolecular photosensitized isomerization are measured to be approximately 0.013, 0.012, and 0.011, and the efficiencies of triplet norbornadiene formation via singlet electron transfer are approximately 0.070, 0.065, and 0.059 for generations 1-3, respectively. The light-harvesting ability of CZ-Gn-NBD increases with the generation due to an increase of the number of peripheral chromophores. In glassy 2-methyltetrahydrofuran at 77 K, the triplet-triplet energy transfer proceeds with efficiencies of approximately 0.86, 0.64, and 0.36 and rate constants of 0.96, 0.25, and 0.08 s(-1) for generations 1-3, respectively. The intramolecular singlet electron transfer and triplet energy transfer in CZ-Gn-NBD proceed mainly via a through-space mechanism involving the proximate donor (folding back conformation) and acceptor groups.

Synthesis of pyridazinyl ligands for multimetallic complexes

Abstract: A family of ligands based upon the linking of two or three bis-(2-pyridyl)pyridazine (dppz) moieties via the 4- or 4,5-positions of the pyridazine rings has been synthesised using an inverse electron demand Diels–Alder pathway Thus, reaction of 3,6-di(2-pyridyl)-1,2,4,5-tetrazine (dptz) with a series of dienes (1,4-divinylbenzene, 1,5-cyclooctadiene, norbornadiene, 1,5-hexadiene or 1,4-cyclohexadiene), diketones (1,4-diacetylbenzene), or trienes (trans,trans,cis-1,5,9-cyclododecatriene or trans,trans,trans-1,5,9-cyclododecatriene) has been studied and seven ligands isolated, namely 4,4′-(1,4-phenylene)bis(3,6-dipyridin-2-ylpyridazine) (L1), 5,6,11,12-tetrahydro-1,4,7,10-tetrapyridin-2-ylcycloocta[1,2-d:5,6-d′]dipyridazine (L2), 5,10-methano-1,4,6,9-tetrapyridin-2-ylpyridazino[4,5-g]phthalazine (L3), 4,4′-ethane-1,2-diylbis(3,6-dipyridin-2-ylpyridazine) (L4), 1,4,6,9-tetrapyridin-2-ylpyridazino[4,5-g]phthalazine (L5), cyclododeca[1,2-d:5,6-d′]dipyridazine-(11Z)-5,6,11,12,15,16-hexahydro-1,4,7,10-tetrapyridin-2-yl (L6) and 5,6,11,12,17,18-hexahydro-1,4,7,10,13,16-hexapyridin-2-ylcyclododeca[1,2-d:5,6-d′:9,10-d″]tripyridazine (L7) Compounds L1, L2 and L4 have been characterised by single crystal X-ray diffraction revealing the formation of molecular stacking in the solid-state via π–π interactions between dppz moieties The potential of these ligands to form multimetallic complexes has been demonstrated by the successful synthesis and structural characterisation of {[Cu4(L1)(NO3)6(MeO)2(MeOH)2]}, {[Cu4(L1)(NO3)6(MeO)2(EtOH)2]}, {[Cd(NO3)(EtOH)3][Cd(NO3)3(L2)]} and {[Cd(NO3)2]2(L5)3}

Metallomacrocycles that incorporate cofacially aligned diimide units.

Abstract: Pyromellitic diimide and naphthalene diimide moieties were incorporated into hemilabile phosphanylalkyl thioether ligands. These ligands reacted with [Cu(CH3CN)4]PF6 and [Rh(NBD)Cl]2 (NBD = norbornadiene) by the weak-link approach to form condensed intermediates. Upon reaction of each diimide ligand with these transition-metal precursors, the two diimide units became cofacially aligned within a supramolecular macrocyclic architecture. The introduction of ancillary ligands to each of these condensed intermediates caused the weak thioether-metal bonds to break, thus generating a large macrocycle in which the distance between diimide units is significantly larger than for the condensed intermediates. The two Rh(I) cationic condensed intermediates were characterized by single-crystal X-ray diffraction studies, and the electrochemical activity of these macrocycles was demonstrated with the naphthalene diimide-Cu(I) macrocycles.

Poly[(para‐halogenated)phenylacetylene]s Prepared with a [Rh(norbornadiene)Cl]2 Catalyst: Syntheses and Structure Elucidation

Abstract: pXPAs were stereospecifically polymerized using [Rh(nbd)Cl] 2 as catalyst in the presence of a mixed solvent, i.e., ethanol and triethylamine, at 20 °C. The resulting PpXPAs were characterized in detail in order to predict geometrical structures concerning cis and trans configurations in the main-chain C=C bonds using 1 H NMR, laser Raman, XRD, and ESR methods. The data showed that the PpXPAs have an extremely high content of the cis-transoid form. Immobile unpaired electrons, ca. 1.2-3.1 x 10 17 spins · g -1 , called the cis radicals, were found to be stabilized even in the pristine cis PpXPAs. The observed g values of the pristine PpXPAs could be correlated with the spin-orbit coupling constant ξ of the halogen atom at the para position of the phenyl ring.

Molecular ordering and structure of quasi-spherical solutes by liquid crystal NMR and Monte Carlo simulations: the case of norbornadiene.

Abstract: Norbornadiene (a C2v symmetry bicyclic rigid hydrocarbon) dissolved in three different nematic mesophases has been studied by liquid crystal NMR, to contribute to a better understanding of the influence of solvents on the solute's ordering and structure. The main results achieved by this work can be summarized as follows: (i) the order parameters obtained by the analysis of the 1H NMR spectra (at different temperatures) were successfully reproduced by a recently proposed model of solute/liquid crystal interactions, by using Monte Carlo numerical simulations; (ii) the theoretical (B3LYP/6-31++G**) "equilibrium" geometry of norbornadiene, vibrationally corrected by using the force field calculated at the same level, is compatible (within, at most, a 5% error) with experimental LXNMR data. This leads to the conclusion that the structure is not significantly distorted by the tested solvents.

Photophysical and photochemical studies on bis(Dendron) poly(aryl ether) dendrimers: Intramolecular triplet energy transfer in poly(aryl ether) dendrimers via a folded conformation

Abstract: A series of Frechet-type bis(dendron) poly(aryl ether) dendrimers ([BP-Gn]2-NBD, n = 1–3) with the benzophenone (BP) chromophores and the norbornadiene (NBD) group attached to the periphery and the core, respectively, were synthesized, and their photophysical and photochemical properties were investigated by using steady-state and time-resolved techniques. Intramolecular triplet energy transfer from the peripheral BP chromophores to the core NBD group in [BP-Gn]2-NBD occurs with the efficiency of ca. 84%, 56% and 48%, and with the rate constant of 1.9 × 107, 1.2 × 107, 1.1 × 107 s−1 at room temperature for generations 1–3, respectively. Selective excitation of the BP groups resulted in the isomerization of NBD to the quadricyclane (QC). The quantum yields of the intramolecular photosensitized isomerization for [BP-Gn]2-NBD are measured to be ca. 0.147, 0.098 and 0.087 for generations 1–3, respectively. The light-harvesting ability of these molecules increases with increasing the number of peripheral chromophores. The rate constant of the triplet–triplet energy transfer decreases inconspicuously with increasing generation, which validates that the intramolecular triplet energy transfer mainly takes place via a through space mechanism involving the closest donor and the acceptor groups by folding of the dendrimer structure, and the bis(dendron) system takes more congested conformation than the corresponding monodendron system.

Triplet photosensitization of myrcene and some dienes within zeolite Y through heavy atom effect

Abstract: Myrecene undergoes successful triplet photosensitization within zeolite Y microreactor exchanged with K+, Cs+ and Tl+ heavy cations. Norbornadiene, 5,5-diphenyl-1,3-cyclohexadiene and dicyclopentadiene under the same conditions afford the corresponding triplet products with higher yields and improved diastereoselectivity.

Stable catalyst for intermolecular Pauson–Khand reaction

Abstract: The catalytic activity of previously formed Co 2 (CO) 6 [P(Ph) 3 ] 2 ( 1 ) was compared with Co 2 (CO) 8 and the system formed by Co 2 (CO) 8 plus PPh 3 in the intermolecular Pauson–Khand (PK) reaction between norbornadiene and phenylacetylene. The effects of pressure, catalyst concentration and temperature were also studied. Additionally, the catalytic activity of complex 1 was compared with Co 2 (CO) 6 [P(OPh) 3 ] 2 ( 2 ) in the intermolecular PK reaction between strained alkenes and terminal and non-terminal alkynes. Both catalysts are very stable, quite efficient and interestingly complex 2 leads to double PK reaction. The results indicate that these complexes are attractive alternatives to Co 2 (CO) 8 as catalyst and in addition, complex 2 is an alternative catalyst for double cyclocarbonylation reaction.

Isomerization pathways from the norbornadiene to the cycloheptatriene radical cation by opening a bridgehead-methylene bond: a theoretical investigation.

Abstract: Three skeletal rearrangement channels for the norbornadiene (N˙+) to the 1,3,5-cycloheptatriene (CHT˙+) radical cation conversion, initialized by opening a bridgehead-methylene bond in N˙+, are investigated using the quantum chemical B3LYP, MP2 and CCSD(T) methods in conjunction with the 6–311+G(d,p) basis set. Two of the isomerizations proceed through the norcaradiene radical cation (NCD˙+), either through a concerted path (N˙+ – NCD˙+), or by a stepwise mechanism via a stable intermediate (N˙+ – I1 – NCD˙+). At the CCSD(T)/6–311+G(d,p)//B3LYP/6–311+G(d,p) level, the lowest activation energy, 28.9 kcal mol−1, is found for the concerted path whereas the stepwise path is found to be 2.3 kcal mol−1 higher. On both pathways, NCD˙+ rearranges further to CHT˙+ with significantly less activation energy. The third channel proceeds from N˙+ through I1 and then directly to CHT˙+, with an activation energy of 37.1 kcal mol−1. The multi-step channel reported earlier by our group, which proceeds from N˙+ to CHT˙+via the quadricyclane and the bicyclo[2.2.1]hepta-2-ene-5-yl-7-ylium radical cations, is 4.6 kcal mol−1 lower than the most favorable path of the present study. If the methylene group is substituted with C(CH3)2, however, the concerted path is estimated to be 5.6 kcal mol−1 lower than the corresponding substituted multi-step path at the B3LYP/6–311+(d,p) level. This shows that substitution of particular positions can have dramatic effects on altering reaction barriers in the studied rearrangements. We also note that identical energies are computed for CHT˙+ and NCD˙+ whereas, in earlier theoretical investigations, the former was reported to be 6–17 kcal mol−1 more stable than the latter. Finally, a bent geometry is obtained for CHT˙+ with MP2/6–311+G(d,p) in contradiction with the planar conformation reported for this cation in earlier computational studies.

Intramolecular triplet energy transfer in donor-acceptor molecules linked by a crown ether bridge.

Abstract: Bichromophoric compounds BP-C-NP and BP-C-NBD were synthe- sized with benzophenone chromophore (BP) as the donor, and 2-naphthyl (NP) and norbornadiene group (NBD) as the acceptor, respectively. Their in- tramolecular triplet energy transfer was examined. The bridges linking the donor and acceptors in these molecules involve a crown ether moiety complex- ing a sodium ion. Phosphorescence quenching, flash photolysis and photo- sensitized isomerization experiments indicate that intramolecular triplet energy transfer occurs with rate con- stants of about 3.3 = 10 5 and 4.8 = 10 5 s � 1 and efficiencies of about 33 and 42 % for BP-C-NP and BP-C-NBD, respec- tively. Theoretical calculations indicate that these molecules adopt conforma- tions below room temperature which allow their two-end chromophores con- ducive to through-space energy trans- fer.

Ruthenium Complexes of Thiocinnamaldehydes: Synthesis, Structure, and [4+2]‐Cycloaddition Reactions

Abstract: Ruthenium hydrogensulfido complexes [CpRu(P-P)(SH)] ((P-P)= Ph 2 PCH 2 PPh 2 (dppm), Ph 2 PC 2 H 4 PPh 2 (dppe)) were obtained from the corresponding chloro complexes by Cl/SH exchange. Condensation with a range of cinnamaldehydes gave thiocinnamaldehyde complexes [CpRu(P-P)(S= CH-CR 2 =CHR 1 )]PF 6 (R 1 = C 6 H 4 X, R 2 =H, Me, X=H, OMe, NMe 2 , Cl, NO 2 ) as highly-colored crystalline compounds. The thiocinnamaldehyde complexes undergo [4+2]-cycloaddition reactions with vinyl ethers CH 2 =CHOR 3 (R 3 =Et, Bu) and styrenes H 2 C= CHC 6 H 4 Y (Y=H, Me, OMe, Cl, Br, NO;) to give complexes of 2,4,5-trisubstituted 3,4-dihydro-2H-thiopyrans as mixtures of two diastereoisomers. The rate of addition of para-substituted styrenes H 2 C=CHC 6 H 4 Y to [CpRu-(dppm)(S=CH-CH=CHPh)]PF 6 increases in the series Y=NO 2 , Br, Cl, H, Me, OMe, indicating that the cycloaddition is dominated by the HOMO-(dienophile)-LUMO(diene) interaction. The strained dienophiles norbornadiene and norbornene also add, giving ruthenium complexes of 3-thia-tricyclo[6.2.1.0 2,7 ]undeca-4,9-dienes and 3-thia-tricyclo[6.2.1.0 2,7 ]undec-4-enes, respectively. Addition reactions with acrolein, methacrolein, methyl vinyl ketone, acrylic ester, or ethyl propiolate finally yielded ruthenium complexes of 3,4-disubstituted 3,4-dihydro-2H-thiopyrans and 4H-thiopyrans, respectively.

Catalytic syntheses of polycyclic compounds based on norbornadiene in the presence of nickel complexes: V. Codimerization of norbornadiene and methyl vinyl ketone on heterogenized nickel catalysts

Abstract: A new heterogenized nickel catalyst was developed for the codimerization of norbornadiene and methyl vinyl ketone. This catalyst considerably improved the performance characteristics of the process (selectivity, specific activity, and operating time), as compared with available analogs. A thermogravimetric study of the formation of the active component of the catalyst was performed. Factors affecting the selectivity and productivity of the process were determined.

Energetics of photoconversion of norbornadiene to quadricyclane : Effects of directly attached substituents via ab initio and DFT

Abstract: An attempt is made to maximize the photochemical and/or solar energy storage in norbornadiene ( 1 )/quadricyclane ( 2 ) system, through direct attachment of substituents at C 1 , C 2 or C 7 atoms of 1 and 2 . Assessments of the corresponding energies are made at B3LYP/6-311++G* level of theory. Electron donating substituents, D (D=–NMe 2 , –NH 2 , –OMe, –OH, and Me), directly attached at C 2 , increase the energy gap between 1 and 2 , inducing higher storage of energy in the system. Electron withdrawing subsituents, W (W=–NO 2 , –F, –Cl, –Br, –CF 3 and –COOH), directly attached at C 1 , moderately induce the energy storage. Attachment of either D or W groups at C 7 show no significant difference in the photochemical and/or solar energy storages. A Hammet ρ value of −3.69 is encountered for substituents directly attached at C 2 atoms of 1 and 2 . This is in clear contrast to the Hammet ρ value of −0.81 that we recently reported for the subsituents indirectly placed at the C 2 of 1 and/or 2 (through attachment via the para carbon of phenyl rings).

Product Diversity in the Reaction of [(norbornadiene){CpP(iPr)2}Rh] with Alkyl Iodides

Abstract: The reagents [(CpPR2)Li] [R = iPr (2b), cyclohexyl (2c)] react with [(nbd)RhCl] (nbd = norbornadiene) dimer [(1a)2] to yield the respective mononuclear complexes [(nbd)Rh(CpPR2)] (3b,c). Subsequent treatment of 3b with a large excess of MeI led to the formation of the stable organometallic phosphonium salt [(nbd)Rh{CpP(iPr)2Me}]I (4b). The analogous reaction of 3b with the slightly more bulky EtI or nPrI resulted in the formation of the dinuclear [μ-CpP(iPr)2]-bridged dirhodium complex [(nbd)Rh{CpP(iPr)2}Rh(nbd)I] (5b) and the corresponding ylides C5H4P(iPr)2R1 [R1 = Et (6b), nPr (6c)]. The rhodium complexes 3b, 4a and 5b were characterised by X-ray crystal-structure analyses. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)