Synthesis of Fischer type-carbene complexes containing a coordinated thioimidate structural motif

This paper describes a tandem strategy to synthesize a series of new Fischer carbene complexes [(CO)(4)M[double bond, length as m-dash]C[N-(CH(2))(4)-]CH[double bond, length as m-dash]C(NRR')(SR'); M = Cr, W; R = Ar, R' = Me, -(CH(2))(2)-] with a thioimide or thiazoline fragment, in which the sulfur or nitrogen atom is coordinated to a metal center, depending on the nature of alkylating groups included as R'. We have trapped by protonation the proposed intermediate as the thioamide 12 [(CO)(5)W[double bond, length as m-dash]C[N-(CH(2))(4)-]CH(2)C(S)NHPh], which reveals the pathway of this reaction.     

Sulfimidation of thioether groups--a versatile method for modifying and linking thia/oxa crowns

Reaction of the mixed thioether/ether crowns [9]aneO(2)S , [12]aneO(3)S and [18]aneO(4)S(2) with one mol. equivalent of the aminating agent MSH (o-mesitylsulfonylhydroxylamine) in Et(2)O results in the formation of the mono-sulfimidated systems {[9]aneO(2)(S[double bond, length as m-dash]NH(2))}(+), {[12]aneO(3)(S[double bond, length as m-dash]NH(2))}(+) and {[18]aneO(4)S(S[double bond, length as m-dash]NH(2))}(+), while using two mol. equivalents of MSH with gives the disulfimidium cation {[18]aneO(4)(S[double bond, length as m-dash]NH(2))(2)}(2+). All of these species have been isolated in good yields as the [mesSO(3)](-) (mes = 2,4,6-Me(3)C(6)H(2)) salts and can be readily converted to the [BPh(4)](-) salts by metathesis with Na[BPh(4)]. Treatment of or with lithium diisopropylamide (LDA) and N-bromosuccinimide (NBS) at -78 degrees C, followed by addition of a further equivalent of the parent thia/oxa crown, gives monocationic N-bridged sulfimide bicyclic compounds ( and respectively), in which the crowns are linked by the sulfimidic nitrogen. Reaction of with LDA and NBS leads to formation of the {([18]aneO(4)S(2))N}(+) cation which exhibits an intramolecular S-N-S bridge. Crystallographic studies on representative examples of each compound type are described, together with their spectroscopic properties.     

Novel ruthenium(ii) complexes containing the N-phosphorylated iminophosphorane-phosphine ligand Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2): a new coordination mode of its methanide anion

The reactivity of complex [Ru(eta(6)-p-cymene)(kappa(3)P,N,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) towards a variety of mono- and bidentate neutral ligands has been studied, allowing the high-yield synthesis of the novel half-sandwich Ru(ii) derivatives [Ru(eta(6)-p-cymene)(L)(kappa(2)P,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) (L = N[triple bond, length as m-dash]CMe , N[triple bond, length as m-dash]CEt , PMe(3), PMe(2)Ph , PMePh(2), PPh(3), P(OMe)(3), P(OEt)(3), P(OPh)(3), py , kappa(1)P-dppm , kappa(1)P-dppe ), as well as the octahedral species [Ru(Ninsertion markN)(2)(kappa(2)P,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) (Ninsertion markN = bipy , phen ). Deprotonation of complexes ,, upon treatment with an excess of NaOH in CH(2)Cl(2), generates the monocationic derivatives [Ru(Ninsertion markN)(2)(kappa(2)P,N-Ph(2)PC(H)[double bond, length as m-dash]P{NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][Cl] (Ninsertion markN = bipy , phen ) in which the methanide anion adopts an unprecedented kappa(2)P,N bidentate coordination mode. The structures of compounds , and have been determined by single-crystal X-ray diffraction methods.     

A combined ab initio and photoionization mass spectrometric study of polyynes in fuel-rich flames

Polyynic structures in fuel-rich low-pressure flames are observed using VUV photoionization molecular-beam mass spectrometry. High-level ab initio calculations of ionization energies for C2nH2 (n=1-5) and partially hydrogenated CnH4 (n=7-8) polyynes are compared with photoionization efficiency measurements in flames fuelled by allene, propyne, and cyclopentene. C2nH2 (n=1-5) intermediates are unambiguously identified, while HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH=C=CH2, HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH=CH2 (vinyltriacetylene) and HC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C-CH[double bond, length as m-dash]CH-C[triple bond, length as m-dash]CH are likely to contribute to the C7H4 and C8H4 signals. Mole fraction profiles as a function of distance from the burner are presented. C7H4 and C8H4 isomers are likely to be formed by reactions of C2H and C4H radicals but other plausible formation pathways are also discussed. Heats of formation and ionization energies of several combustion intermediates have been determined for the first time.     

Nickel complexes supported by quinoline-based ligands: synthesis, characterization and catalysis in the cross-coupling of arylzinc reagents and aryl chlorides or aryltrimethylammonium salts

Lithium and nickel complexes bearing quinoline-based ligands have been synthesized and characterized. Reaction of 8-azidoquinoline with Ph(2)PNHR (R = p-MeC(6)H(4), Bu(t)) affords N-(8-quinolyl)iminophosphoranes RNHP(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N) (1a, R = p-MeC(6)H(4); 1b, R = Bu(t). C(9)H(6)N = quinolyl)). Reaction of 1a with (DME)NiCl(2) generates a nickel complex [NiCl(2){N(8-C(9)H(6)N)[double bond, length as m-dash]P(Ph(2))NH(p-MeC(6)H(4))}] (2a). Treatment of 1b with (DME)NiCl(2) and following with NaH produces [NiCl{(1,2-C(6)H(4))P(Ph)(NHBu(t))[double bond, length as m-dash]N(8-C(9)H(6)N)}] (4). Complex 4 was also obtained by reaction of (DME)NiCl(2) with [Li{(1,2-C(6)H(4))P(Ph)(NHBu(t))[double bond, length as m-dash]N(8-C(9)H(6)N)}] (5) prepared through lithiation of 1b. Reaction of 2-PyCH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N) (6, Py = pyridyl) and PhN[double bond, length as m-dash]C(Ph)CH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N) (8), respectively, with (DME)NiCl(2) yields two five-coordinate N,N,N-chelate nickel complexes, [NiCl(2){2-PyCH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N)}] (7) and [NiCl(2){PhN[double bond, length as m-dash]C(Ph)CH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N)}] (9). Similar reaction between Ph(2)PCH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N) (10) and (DME)NiCl(2) results in five-coordinate N,N,P-chelate nickel complex [NiCl(2){Ph(2)PCH(2)P(Ph(2))[double bond, length as m-dash]N(8-C(9)H(6)N)}] (11). Treatment of [(8-C(9)H(6)N)N[double bond, length as m-dash]P(Ph(2))](2)CH(2) (12) [prepared from (Ph(2)P)(2)CH(2) and 2 equiv. of 8-azidoquinoline] with LiBu(n) and (DME)NiCl(2) successively affords [NiCl{(8-C(9)H(6)N)NP(Ph(2))}(2)CH] (13). The new compounds were characterized by (1)H, (13)C and (31)P NMR spectroscopy (for the diamagnetic compounds), IR spectroscopy (for the nickel complexes) and elemental analysis. Complexes 2a, 4, 7, 9, 11 and 13 were also characterized by single-crystal X-ray diffraction techniques. The nickel complexes were evaluated for the catalysis in the cross-coupling reactions of arylzinc reagents with aryl chlorides and aryltrimethylammonium salts. Complex 7 exhibits the highest activity among the complexes in catalyzing the reactions of arylzinc reagents with either aryl chlorides or aryltrimethylammonium bromides.     

Polymeric materials based on main group elements: the recent development of ambient temperature and controlled routes to polyphosphazenes

This Perspective discusses the development of new routes to polyphosphazenes, [R(2)P[double bond, length as m-dash]N](n), that occur at ambient temperature and, in some cases, allow molecular weight control and access to narrow molecular weight distributions and block copolymers. For example, the room temperature silyl-carborane initiated ring-opening polymerisation of (NPCl(2))(3) is described together with chain growth condensation polymerisations of phosphoranimines Cl(3)P[double bond, length as m-dash]NSiMe(3) and BrMePhP[double bond, length as m-dash]NSiMe(3). Recent works on donor-stabilised cationic phosphoranimines are also discussed.     

Intramolecular [2+3]-addition of an azide to a CC double bond as a novel approach to piperazines

An intramolecular [2+3]-cycloaddition of an azide to a CC double bond was carried out to obtain hexahydro[1,2,3]triazolo[1,5-a]pyrazines. These compounds were used as intermediates to prepare 2-(halogenomethyl)piperazines that could serve as precursors for various condensed derivatives.     

Nickel alkynyl and allenylidene complexes: Synthesis and properties

Copper-catalyzed reaction of [Cp(PPh₃)NiCl] with the terminal alkynes H-CC-C(O)R (R = O-Menthyl, NMe₂, Ph) yields the alkynyl complexes [Cp(PPh₃)Ni-CC-C(O)R]. Subsequent O-methylation with either [Me₃O]BF₄ or MeSO₃CF₃ affords cationic allenylidene complexes, [Cp(PPh₃)NiCCC(OMe)R]⁺X¯ (X = BF₄, SO₃CF₃). N-Alkylation of Cp(PPh₃)Ni-pyridylethynyl complexes likewise gives cationic allenylidene complexes. [Cp(PPh₃)Ni-CC-C(CH)₄N] adds BF₃ at nitrogen. Modification of the ligand sphere in these nickel allenylidene complexes is possible by replacing PPh₃ by PMe₃ in the alkynyl complex precursors. The first allenylidene(carbene)nickel cation, [Cp(SIMes)NCCC(OMe)NMe₂]⁺, is accessible by successive reaction of [Cp(SIMes)NiCl] with H-CC-C(O)NMe₂ and [Me₃O]BF₄. By the analogous sequence an allenylidene complex containing the chelating (diphenylphosphanyl)ethylcyclopentadienyl ligand can be prepared. DFT Calculations were carried out on the allenylidene complex cation [Cp(PPh₃)NiCCC(OMe)NMe₂]⁺ and on its precursor, the alkynyl complex [Cp(PPh₃)Ni-CC-C(O)NMe₂]. Based on the spectroscopic data and a X-ray structure analysis the bonding in the new nickel allenylidene complexes is best represented by several resonance forms, an alkynyl resonance form considerably contributing to the overall bond.     

Doubly bonded systems between heavier Group 15 elements

There has been much interest in the synthesis and properties of doubly bonded systems between heavier Group 15 elements, i. e. heavier analogues of azo-compounds (dipnictenes), from the viewpoints of fundamental and material chemistry. Although such double-bond compounds between heavier main group elements are known to be highly reactive, too much so to be isolated as stable compounds, a number of reports on the synthesis of kinetically stabilized diphosphenes (RP[double bond, length as m-dash]PR), diarsenes (RAs[double bond, length as m-dash]AsR), and phosphaarsenes (RP[double bond, length as m-dash]AsR) bearing bulky substituent have been published since 1980. We have also succeeded in the synthesis of the first stable distibene (RSb[double bond, length as m-dash]SbR) and dibismuthene (RBi[double bond, length as m-dash]BiR) by taking advantage of efficient steric protection groups, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt), and revealed their structures and properties systematically. Thus, the doubly bonded compounds between heavier Group 15 elements are no longer imaginary species but are those with real existence which are stable, even in the case of the heaviest non-radioactive element bismuth, when they are appropriately protected by bulky substituents. This Perspective describes our research on the chemistry of kinetically stabilized double-bond compounds between heavier Group 15 elements.     

Metal catalyzed C(sp(3))-H bond amination of 2-alkyl azaarenes with diethyl azodicarboxylate

Metal-catalyzed direct C(sp(3))-H bond amination of 2-alkyl azaarenes with N[double bond, length as m-dash]N double bonds has been developed, which expands the scope of C(sp(3))-H bond activation reactions and provides a new access to medicinally important azaarene derivatives.     

Azines possessing strong push-pull donors/acceptors

Azines (R(2)C[double bond, length as m-dash]N-N[double bond, length as m-dash]CR(2)) are 2,3-diaza analogues of 1,3-butadiene. In this report we show that strong polarisation of the azine imparts structural features consistent with delocalization within the azine fragment; NLO properties for the azines are also reported.     

Transition metal vinylidene complexes as supramolecular building blocks: nucleobase-mediated self-assembly of crystals with hexagonal symmetry

Reaction of the ruthenium half sandwich compound RuCl(eta(5)-C(5)H(5))(PPh(3))(2) with the uracil (Ur) substituted alkyne HC[triple bond, length as m-dash]CUr in the presence of halide scavengers NH(4)X (X = PF(6), BF(4), OTf) results in the formation of the vinylidene complexes [Ru([double bond, length as m-dash]C[double bond, length as m-dash]CHUr)(eta(5)-C(5)H(5))(PPh(3))(2)][X] which crystallize in the hexagonal space group P6(3)/m. The hexagonal symmetry inherent to the system is due to the formation of a hydrogen bonded array mediated by the two sets of donor-acceptor units on the uracil, resulting in the formation of a cyclic "rosette" containing six ruthenium cations. In solution the (1)H and (31)P{(1)H} NMR spectra of the vinylidene complexes are both concentration and temperature dependent, in accord with the presence of monomer-dimer equilibria in which the rate of rotation of the vinylidene group is fast on the NMR timescale in the monomeric species, but slow in the dimers. The isoelectronic molybdenum-containing vinylidene complex [Mo(eta(7)-C(7)H(7))(dppe)([double bond, length as m-dash]C[double bond, length as m-dash]CHUr)][BF(4)] (dppe = 1,2-bis(diphenylphosphino)ethane) has also been prepared, but forms symmetric dimers in the solid state.     

Synthesis of a stable 1,2-bis(ferrocenyl)diphosphene

The synthesis and characterization of a stable 1,2-bis(ferrocenyl)diphosphene, wherein a P[double bond, length as m-dash]P π-bond connects two ferrocenyl units will be reported. This represents an unprecedented example for a d-π electron system containing a heavier pnictogen π-spacer group. Stabilization of the highly reactive P[double bond, length as m-dash]P π-bond was achieved by steric protection using two bulky ferrocenyl moieties.     

A microwave spectroscopic and quantum chemical study of propa-1,2-dienyl selenocyanate (H(2)==C==CHSeC[triple bond]N) and cyclopropyl selenocyanate (C(3)H(5)SeC[triple bond]N)

The microwave spectra of propa-1,2-dienyl selenocyanate, H(2)C==C==CHSeC[triple bond]N, and cyclopropyl selenocyanate, C(3)H(5)SeC[triple bond]N, are reported. The spectra of the ground and two vibrationally excited states of the (80)Se isotopologue and the spectrum of the ground state of the (78)Se isotopologue were assigned for one rotameric form of H(2)C==C[double bond, length as m-dash]CHSeC[triple bond]N. This conformer is characterized by a C-C-Se-C dihedral angle of 129(5) degrees from synperiplanar (0 degrees ) and is shown to be the global minimum of H(2)C[double bond, length as m-dash]C[double bond, length as m-dash]CHSeC[triple bond]N. The spectra of the ground and of three vibrationally excited states of the (80)Se isotopologue, as well as of the ground state of the (78)Se isotopologue of one rotamer of C(3)H(5)SeC[triple bond]N were assigned. This conformer has a H-C-Se-C dihedral angle of 80(4) degrees from synperiplanar and is at least 3 kJ mol(-1) more stable than any other form of the molecule. The microwave study has been augmented by quantum chemical calculations at the B3LYP/6-311+ +G(3df,3pd) and MP2/6-311+ +G(3df,3pd) levels of theory.     

Intriguing roles of reactive intermediates in dissociation chemistry of N-phenylcinnamides

In mass spectrometry of protonated N-phenylcinnamides, the carbonyl oxygen is the thermodynamically most favorable protonation site and the added proton is initially localized on it. Upon collisional activation, the proton transfers from the carbonyl oxygen to the dissociative protonation site at the amide nitrogen atom or the α-carbon atom, leading to the formation of important reactive intermediates. When the amide nitrogen atom is protonated, the amide bond is facile to rupture to form ion/neutral complex 1, [RC(6)H(4)CH[double bond, length as m-dash]CHCO(+)/aniline]. Besides the dissociation of the complex, proton transfer reaction from the α-carbon atom to the nitrogen atom within the complex takes place, leading to the formation of protonated aniline. The presence of electron-withdrawing groups favored the proton transfer reaction, whereas electron-donating groups strongly favored the dissociation (aniline loss). When the proton transfers from the carbonyl oxygen to the α-carbon atom, the cleavage of the C(α)-CONHPh bond results in another ion/neutral complex 2, [PhNHCO(+)/RC(6)H(4)CH[double bond, length as m-dash]CH(2)]. However, in this case, electron-donating groups expedited the proton transfer reaction from the charged to the neutral partner to eliminate phenyl isocyanate. Besides the cleavage of the C(α)-CONHPh bond, intramolecular nucleophilic substitution (a nucleophilic attack of the nitrogen atom at the β-carbon) and stepwise proton transfer reactions (two 1,2-H shifts) also take place when the α-carbon atom is protonated, resulting in the loss of ketene and RC(6)H(5), respectively. In addition, the H/D exchanges between the external deuterium and the amide hydrogen, vinyl hydrogens and the hydrogens of the phenyl rings were discovered by D-labeling experiments. Density functional theory-based (DFT) calculations were performed to shed light on the mechanisms for these reactions.     

Novel functionalised P-ligands: advances and application

Novel endo- and exocyclic phosphine ligands possessing different functionalities obtained by reduction of the PO precursors with desired stereochemistry are discussed. The diastereoselective deoxygenation including the catalytic reduction processes, the factors defining the reactivity and the role of the substituents on the stability of phosphorus atom configuration in a series of 3-aryl-3-phosphabicyclo[3.1.0]hexanes are reported. The complexation features of the ligands with Rh(III) and Pd(II) were examined and Rh(III) complexes were tested in styrene hydroformylation showing the structure-activity dependence.     

The d4/d3 redox pairs [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']z (z=0 and 1): structural consequences of electron transfer and implications for the inverse halide order

The d4 halide complexes [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp'] {X=F, Cl, Br or I; R=Me or Ph; M=Mo or W; Tp'=hydrotris(3,5-dimethylpyrazolyl)borate} undergo one-electron oxidation to the d3 monocations [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+, isolable for M=W, R=Me. X-Ray structural studies on the redox pairs [WX(CO)(eta-MeC[triple bond, length as m-dash]CMe)Tp']z (X=Cl and Br, z=0 and 1), the ESR spectra of the cations [WX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+ (X=F, Cl, Br or I; R=Me or Ph), and DFT calculations on [WX(CO)(eta-MeC[triple bond, length as m-dash]CMe)Tp']z (X=F, Cl, Br and I; z=0 and 1) are consistent with electron removal from a HOMO (of the d4 complexes) which is pi-antibonding with respect to the W-X bond, pi-bonding with respect to the W-C(O) bond, and delta-bonding with respect to the W-Calkyne bonds. The dependence of both oxidation potential and nu(CO) for [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp'] shows an inverse halide order which is consistent with an ionic component to the M-X bond; the small size of fluorine and its closeness to the metal centre leads to the highest energy HOMO and the lowest oxidation potential. In the cations [MX(CO)(eta-RC[triple bond, length as m-dash]CR)Tp']+ electronegativity effects become more important, leading to a conventional order for Cl, Br and I. However, high M-F pi-donation is still facilitated by the short M-F distance.     

Binuclear manganese and rhenium carbonyls M2(CO)n (n = 10, 9, 8, 7): comparison of first row and third row transition metal carbonyl structures

The equilibrium geometries, thermochemistry, and vibrational frequencies of the homoleptic binuclear rhenium carbonyls Re2(CO)n (n = 10, 9, 8, 7) were determined using the MPW1PW91 and BP86 methods from density functional theory (DFT) with the effective core potential basis sets LANL2DZ and SDD. In all cases triplet structures for Re2(CO)n were found to be unfavorable energetically relative to singlet structures, in contrast to corresponding Mn2(CO)n derivatives, apparently owing to the larger ligand field splitting of rhenium. For M2(CO)10 (M = Mn, Re) the unbridged structures (OC)5M-M(CO)5 are preferred energetically over structures with bridging CO groups. For M2(CO)9 (M = Mn, Re) the two low energy structures are (OC)4M(micro-CO)M(CO)4 with an M-M single bond and a four-electron donor bridging CO group and (OC)4M[double bond, length as m-dash]M(CO)5 with no bridging CO groups and an M[double bond, length as m-dash]M distance suggesting a double bond. The lowest energy structures for Re2(CO)8 have Re[triple bond, length as m-dash]Re distances in the range 2.6-2.7 A suggesting the triple bonds required to give the Re atoms the favored 18-electron configuration. Low energy structures for Re2(CO)7 are either of the type (OC)(4)M[triple bond, length as m-dash]M(CO)3 with short metal-metal distances suggesting triple bonds or have a single four-electron donor bridging CO group and longer M-M distances consistent with single or double bonds. The 18-electron rule thus appears to be violated in these highly unsaturated Re2(CO)7 structures.     

C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- and trimerization of terminal alkynes

The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C[triple bond, length as m-dash]CR)(=C=CHR)(PiPr3)2] 2, 5, 6 react with CO by migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{eta1-(Z)-C(=CHR)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-7-9, of which (Z)-7 (R=Ph) and (Z)-8 (R=tBu) rearrange upon heating or UV irradiation to the (E) isomers. Similarly, trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CPh}(CO)(PiPr3)2] 12 and trans-[Rh{eta1-(Z)-C(=CHCO2Me)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding "non-substituted" derivative trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl isomer trans-[Rh(eta1-CH=]C=C=CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex trans-[Rh(C[triple bond, length as m-dash]CCH=CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R'CO2H (R'=CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC[triple bond, length as m-dash]CCH=CHR or a mixture of the butenyne and the isomeric butatriene, the ratio of which depends on both R and R'. Treatment of 2 (R=Ph) with HCl at -40 degrees C affords five-coordinate [RhCl(C[triple bond, length as m-dash]CPh){(Z)-CH=CHPh}(PiPr3)2] 23, which at room temperature reacts by C-C coupling to give trans-[RhCl{eta2-(Z)-PhC[triple bond, length as m-dash]CCH=CHPh}(PiPr3)2](Z)-21. The related compound trans-[RhCl(eta2-HC[triple bond, length as m-dash]CCH=CH2)(PiPr3)2] 27, prepared from trans-[Rh(C[triple bond, length as m-dash]CH)(=C=CH2)(PiPr3)2] 17 and HCl, rearranges to the vinylvinylidene isomer trans-[RhCl(=C=CHCH=CH2)(PiPr3)2] 28. While stepwise reaction of 2with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes trans-[Rh(kappa1-O2CCF3)(eta2-PhC[triple bond, length as m-dash]CCH=CHPh)(PiPr3)2](Z)-30 and (E)-30, from 2 and CH3CO2H the acetato derivative [Rh(kappa2-O2CCH3)(PiPr3)2] 33 and (Z)-PhC[triple bond, length as m-dash]CCH=]CHPh are obtained. From 6 (R=CO2Me) and HCl or HC[triple bond, length as m-dash]CCO2Me the chelate complexes [RhX(C[triple bond, length as m-dash]CCO2Me){kappa2(C,O)-CH=CHC(OMe)=O}(PiPr3)2] 34 (X=Cl) and 35 (X=C[triple bond, length as m-dash]CCO2Me) have been prepared. In contrast to the reactions of [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE)(CH=CHE)(PiPr3)2] 37(E=CO2Me) with chloride sources which give, via intramolecular C-C coupling, four-coordinate trans-[RhCl{eta2-(E)-EC[triple bond, length as m-dash]CCH=CHE}(PiPr3)2](E)-36, treatment of 37with HC[triple bond, length as m-dash]CE affords, via insertion of the alkyne into the rhodium-vinyl bond, six-coordinate [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE){eta1-(E,E)-C(=CHE)CH=CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{eta2-(E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne (E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE 40.