Derivatives Trans Research Articles

Iridium-containing cumulenes: how to prepare and how to use

This microreview summarizes the work on iridium-containing cumulenes of the general compositions trans-[IrX{C(C) n RR′}(P iPr 3) 2] with n=1, 2, 3 and 4, which recently has been carried out in our laboratory. It is shown that all the parent compounds with X=Cl and an IrCC, IrCCC, IrCCCC or IrCCCCC chain can be prepared using [IrH 2Cl(P iPr 3) 2] as the starting material. Independent on the length of the chain, the iridiacumulenes are highly reactive to both nucleophiles and electrophiles. For n=1 and 3, the corresponding chloro complexes can be converted to organometallic derivatives trans-[IrR″{=C(C) n RR′}(P iPr 3) 2], which in the presence of CO smoothly undergoe migratory insertion reactions. Upon treatment with CO, the azido compounds trans-[Ir(N 3){C(C) n RR′}(P iPr 3) 2] ( n=1, 2 and 3) react similarly. A remarkable feature is that the hydroxoiridium(I) derivatives trans-[Ir(OH)(CCRR′)(P iPr 3) 2] and trans-[Ir(OH)(CCCRR′)(P iPr 3) 2] behave as Broensted bases and react with HX (X=OPh, F, CCR) by elimination of water and the formation of new iridiacumulenes containing an IrX bond. While the reactions of the chloro complexes trans-[IrCl(CCCRR′)(P iPr 3) 2] and trans-[IrCl(CCCCRR′)(P iPr 3) 2] with HCl proceed by oxidative addition to afford neutral iridium(III) compounds, the iridium allenylidenes react with CF 3CO 2H in polar solvents to generate cationic iridium carbynes trans-[IrCl(CCHCRR′)(P iPr 3) 2]X, being the first representatives of this type.

Unusual pathways for metal-assisted C[bond]C and C[bond]P coupling reactions using allenylidenerhodium complexes as precursors.

The rhodium allenylidenes trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = Ph (1), p-Tol (2)] react with NaC(5)H(5) to give the half-sandwich type complexes [(eta(5)-C(5)H(5))Rh[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))] (3, 4). The reaction of 1 with the Grignard reagent CH(2)[double bond]CHMgBr affords the eta(3)-pentatrienyl compound [Rh(eta(3)-CH(2)CHC[double bond]C[double bond]CPh(2))(PiPr(3))(2)] (6), which in the presence of CO rearranges to the eta(1)-pentatrienyl derivative trans-[Rh[eta(1)-C(CH[double bond]CH(2))[double bond]C[double bond]CPh(2)](CO)(PiPr(3))(2)] (7). Treatment of 7 with acetic acid generates the vinylallene CH(2)[double bond]CH[bond]CH[double bond]=C=CPh(2) (8). Compounds 1 and 2 react with HCl to give the five-coordinate allenylrhodium(III) complexes [RhCl(2)[CH[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (10, 11). An unusual [C(3) + C(2) + P] coupling process takes place upon treatment of 1 with terminal alkynes HC[triple bond]CR', leading to the formation of the eta(3)-allylic compounds [RhCl[eta(3)-anti-CH(PiPr(3))C(R')C[double bond]C[double bond]CPh(2)](PiPr(3))] [R' = Ph (12), p-Tol (13), SiMe(3) (14)]. From 12 and RMgBr the corresponding phenyl and vinyl rhodium(I) derivatives 15 and 16 have been obtained. The previously unknown unsaturated ylide iPr(3)PCHC(Ph)[double bond]C[double bond]C[double bond]CPh(2) (17) was generated from 12 and CO. A [C(3) + P] coupling process occurs on treatment of the rhodium allenylidenes 1, 2, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(p-Anis)(2)](PiPr(3))(2)] (20) with either Cl(2) or PhICl(2), affording the ylide-rhodium(III) complexes [RhCl(3)[C(PiPr(3))C[double bond]C(R)R'](PiPr(3))] (21-23). The butatrienerhodium(I) compounds trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (28-31) were prepared from 1, 20, and trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = CF(3) (26), tBu (27)] and diazomethane; with the exception of 30 (R = CF(3), R' = Ph), they thermally rearrange to the isomers trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C[double bond]C(R)R'](PiPr(3))(2)] (32, 33, and syn/anti-34). The new 1,1-disubstituted butatriene H(2)C[double bond]C[double bond]C[double bond]C(tBu)Ph (35) was generated either from 31 or 34 and CO. The iodo derivatives trans-[RhI(eta(2)-H(2)C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] [R = Ph (38), p-Anis (39)] were obtained by an unusual route from 1 or 20 and CH(3)I in the presence of KI. While the hydrogenation of 1 and 26 leads to the allenerhodium(I) complexes trans-[RhCl[eta(2)-H(2)C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] (40, 41), the thermolysis of 1 and 20 produces the rhodium(I) hexapentaenes trans-[RhCl(eta(2)-R(2)C[double bond]C[double bond]C[double bond]C[double bond]C[double bond]CR(2))(PiPr(3))(2)] (44, 45) via C-C coupling. The molecular structures of 3, 7, 12, 21, and 28 have been determined by X-ray crystallography.

Carbene Iridium(I) and Iridium(III) Complexes Containing the Metal Center in Different Stereochemical Environments

The mixed-ligand complex [IrCl(C2H4)(SbiPr3)(PiPr3)] (2), prepared from [IrCl(C2H4)(PiPr3)]2 (1) and SbiPr3, reacts not only with CO, diphenylacetylene, and H2 by ligand substitution or oxidative addition but also with diaryldiazomethanes R2CN2 to give the four-coordinate iridium(I) carbenes [IrCl(CR2)(SbiPr3)(PiPr3)] (8−10) in 60−70% isolated yield. In contrast, treatment of 2 and of the related cyclooctene derivative trans-[IrCl(C8H14)(SbiPr3)2] (12) with C5Cl4N2 affords the diazoalkane complexes trans-[IrCl(N2C5Cl4)(SbiPr3)(EiPr3)] (11, E = P; 13, E = Sb) without elimination of N2. Displacement of the stibine ligand in 8−10 by PiPr3 leads to the corresponding bis(phosphine) compounds trans-[IrCl(CR2)(PiPr3)2] (14−16), while the reaction of 8 (R = C6H5) with NaC5H5 yields the half-sandwich-type complex [(η5-C5H5)Ir(CPh2)(PiPr3)] (17). Protonation of 17 with HCl occurs stepwise to give via the iridium(III) alkyl [(η5-C5H5)IrCl(CHPh2)(PiPr3)] (20) the ring-substituted isomer [(η5-C5H4CHPh2)IrHCl(PiPr3)] (21); however, if 17 is treated with HBF4, a cationic complex is formed which probably contains a η3-coordinated benzylic ligand. The square-planar iridium(I) carbenes 8 and 14 react with HBX4 (X = F, ArF) to afford the ionic products [IrHCl(CPh2)(PiPr3)(EiPr3)]BX4 (23, 24, E = P; 25, E = Sb) and with HCl to give the relatively labile octahedral species [IrHCl2(CPh2)(PiPr3)(EiPr3)] (26, E = P; 27, E = Sb). Treatment of 8 and 14 with ethene yields, besides [IrCl(C2H4)2(SbiPr3)2] (18) and/or trans-[IrCl(C2H4)(PiPr3)2] (28), a mixture of two isomeric olefinic products CH2CHCHPh2 (29) and CH3CHCPh2 (30), the ratio of which is independent of the ligand sphere of the iridium precursor. The molecular structures of 13, 14, 17, and 24 have been determined by X-ray crystallography.

Substitution and Migratory Insertion Reactions of Square-Planar Allenylidene Iridium Complexes

A series of (allenylidene)iridium(I) complexes of general composition trans-[IrX{CCC(Ph)R}(PiPr3)2] [X = Br (5), I (6), NCO (7, 8), NCS (9, 10), OH (11, 12), N3 (13, 14)] was prepared from the corresponding chloro derivatives trans-[IrCl{CCC(Ph)R}(PiPr3)2] (3, 4) by salt metathesis. An X-ray crystal structure analysis of 4 (R = Ph) confirmed the almost linear arrangement of the Ir−C−C−C chain. The azido compounds 13 (R = Ph) and 14 (R = tBu) react with CO by migratory insertion of the allenylidene ligand into the Ir−N3 bond. While the product trans-[Ir{C≡C−CR(Ph)N3}(CO)(PiPr3)2] with R = tBu (16) is thermally stable, the related complex with R = Ph (15) rearranges slowly in benzene to the metalated acrylonitrile derivative trans-[Ir{C(CN)CPh2}(CO)(PiPr3)2] (17) by elimination of N2. Treatment of the phenolato compound trans-[Ir(OPh){CCC(Ph)tBu}(PiPr3)2] (19), obtained from the analogous hydroxo derivative 12 and phenol, with CO also proceeds by migratory insertion and affords the functionalized (alkynyl)iridium(I) complex trans-[Ir{C⋮C−CtBu(Ph)OPh}(CO)(PiPr3)2] (20) in excellent yield. The Lewis basicity of the hydroxo compounds 11 and 12 was also illustrated by the reactions with CF3CO2H, NEt3·3HF, and [pyH]BF4, which gave the substitution products trans-[Ir(κ1-O2CCF3){CCC(Ph)tBu}(PiPr3)2] (21), trans-[IrF(CCCPh2)(PiPr3)2] (22), and trans-[Ir{CCC(Ph)tBu}(py)(PiPr3)2]BF4 (23), respectively. In methanol solution, both 11 and 12 react by complete fragmentation of 1 equiv of CH3OH to afford the octahedral (allenyl)dihydridoiridium(III) complexes [IrH2{CHCC(Ph)R}(CO)(PiPr3)2] (24, 25). An unprecedented type of insertion reaction occurs by treating the hydroxo derivatives 11 and 12 with an excess of 1-alkynes R‘C⋮CH (R‘ = Ph, CO2Me), which leads to the formation of the novel five-coordinate iridium(III) compounds [Ir(C⋮CR‘)2{η1-(E)-CHCR‘−CHCC(Ph)R}(PiPr3)2] (26−29). From 26, 27 (R‘ = Ph), and CO, the octahedral 1:1 adducts 30 and 31 are formed. The molecular structures of 22 and 26 have been determined by X-ray crystallography.

Cis addition of dimethylamine to the coordinated nitriles of cis- and trans-[PtCl 2(NCMe) 2]. X-ray structure of the amidine complex cis-[PtCl 2{ E-N(H)C(NMe 2)Me} 2]·CH 2Cl 2

The reaction of cis-[PtCl 2(NCMe) 2] with a 5-fold excess of Me 2NH in CH 2Cl 2 at −10°C affords in high yield the bis-amidine complex cis-[PtCl 2{ E-N(H)C(NMe 2)Me} 2] ( E, E- 2), where both the amidine ligands assume the E configuration. E, E- 2 was characterized by X-ray structure analysis, NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS). The corresponding reactions of trans-[PtCl 2(NCMe) 2] with Me 2NH gave the bis-amidine complex trans-[PtCl 2{ E-N(H)C(NMe 2)Me} 2] ( E, E- 3) and the mono-amidine derivative trans-[PtCl 2{ E-N(H)C(NMe 2)Me}(NCMe)] ( E- 4).

PX3-induced migratory insertion reactions of half-sandwich-type carbenerhodium(I) complexes

The carbenerhodium(I) complexes trans-[RhCl(CPh2)(L)2] (L = PPri3, 1a; SbPri3, 1b) react with PF3 by cleavage of the rhodium–carbene bond to give the corresponding PF3 derivatives trans-[RhCl(PF3)(L)2] 5a,b, in good yield. In contrast, treatment of the half-sandwich-type compound [(η5-C5H5)Rh(CPh2)(PPri3)], 2a, with both PF3 and P(OPh)3 leads to the migratory insertion of the CPh2 unit into one of the cyclopentadienyl C–H bonds to form the ring-substituted products [{η5-C5H4(CHPh2)}Rh(PX3)(PPri3)] (X = F, 6a; OPh, 6b). The molecular structures of 6a and 6b have been determined by X-ray crystallography. The reaction of the stibine complex [(η5-C5H5)Rh(CPh2)(SbPri3)], 2b, with PF3 proceeds by ligand displacement to afford the new carbenerhodium(I) compound [(η5-C5H5)Rh(CPh2)(PF3)], 7. The mechanism of the migratory insertion reaction is discussed.

Synthesis and Migratory Insertion Reactions of (Vinylidene)iridium Complexes trans-[IrX(CCRR‘)(PiPr3)2] Containing Alkyl, Aryl, Alkynyl, and Azide Ligands,1

The (vinylidene)iridium(I) complexes trans-[IrCl(CCRR‘)(PiPr3)2] (1, 4) react with organolithium compounds R‘ ‘Li by chloride substitution to afford the organoiridium(I) derivatives trans-[IrR‘ ‘(CCRR‘)(PiPr3)2] (5−8) in excellent yields. In contrast, treatment of 1 (R = SiMe3, R‘ = Me) with Grignard reagents R‘ ‘MgX leads to halide metathesis and formation of the bromo- and iodoiridium(I) compounds trans-[IrX{CC(SiMe3)Me}(PiPr3)2] (X = Br, I), respectively. The alkynyl complexes trans-[Ir(C⋮CR)(CCHPh)(PiPr3)2] (R = Ph, CO2Me) are obtained by an acid−base reaction from trans-[Ir(OH)(CCHPh)(PiPr3)2] and the free alkyne. Treatment of compounds 5−8 and 12 with CO initiates a migratory insertion process which gives the η1-vinyl complexes trans-[Ir{η1-(Z)-C(R‘ ‘)CRR‘}(CO)(PiPr3)2] (13−17) in nearly quantitative yields. Acid-induced cleavage of the Ir−C σ-bond of 13, 14, and 17 with CH3CO2H or CF3CO2H affords trans-[Ir(η1-O2CR)(CO)(PiPr3)2] and the corresponding olefin. The preparation of the fluoroiridium(I) derivative trans-[IrF(CCHPh)(PiPr3)2] (26) has been achieved either from trans-[Ir(OH)(CCHPh)(PiPr3)2] and NEt3·3HF or from trans-[Ir(η1-O2CCF3)(CCHPh)(PiPr3)2] and [nBu4N]F. The azidoiridium(I) compounds trans-[IrN3(CCHR)(PiPr3)2] (R = Ph, CO2Me), which are obtained from the related chloro derivatives and excess NaN3, undergo in the presence of CO a migratory insertion reaction to give the cyano-substituted alkyl complexes trans-[Ir{CH(CN)R}(CO)(PiPr3)2] (32, 33) and N2. The molecular structure of trans-[Ir{η1-(Z)-C(Me)C(SiMe3)Me}(CO)(PiPr3)2] (13) has been determined by X-ray crystallography.

Organometallic complexes for nonlinear optics: Part 19. Syntheses and molecular quadratic hyperpolarizabilities of indoanilino–alkynyl–ruthenium complexes

The terminal alkyne 4-HCCC 6H 4N CCHC tBuC(O)C tBuC H ( 1) and ruthenium complex derivatives trans-[Ru(CC-4-C 6H 4N CCH=C tBuC(O)C tBuC H}Cl(dppm) 2] ( 2) and [Ru{CC-4-C 6H 4N CCHC tBuC(O)C tBuC H}(PPh 3) 2(η-C 5H 5)] ( 3) have been synthesized. An X-ray structural study of 3 reveals the expected equivalent CC bond lengths of the phenyl and alternating CC and CC bond lengths of the quinonal ring in the indoanilino–alkynyl ligand; there is a dihedral angle of 47.59° between the phenyl and quinonal rings, probably a result of ortho-hydrogen repulsion. Metal-centred oxidation potentials of 2 and 3 are similar to those of ‘extended chain’ 4-nitroaryl–alkynyl complex analogues. Irreversible quinonal ring-centred reductions occur at significantly more negative potentials than the quasi-reversible reductions in their nitro-containing analogues. Quadratic optical nonlinearities by hyper-Rayleigh scattering at 1064 nm for 2 (417×10 −30 esu) and 3 (658×10 −30 esu) are both large, but resonance enhanced. Two-level-corrected nonlinearities for these complexes (124×10 −30, 159×10 −30 esu, respectively) are also large, despite the presence of electron-donating tert-butyl groups reducing the efficiency of the (formally) electron-accepting quinonal ring in these donor-bridge-acceptor complexes.

Axial ligand substitution and photoisomerization reactions in ruthenium(II) trans mixed-chelate complexes containing the ligands 1,2-phenylenebis(dimethylarsine) and 2,2′-bipyridine or 1,10-phenanthroline

The nitrosyl complex in trans-[RuCl(pdma)(bpy)(NO)][PF 6] 2 (pdma=1,2-phenylenebis(dimethylarsine), bpy=2,2′-bipyridine) reacts at room temperature with stoichiometric NaN 3, followed by an excess of a neutral ligand L 1 in 2-butanone under reflux, to afford high yields of the mono-substituted derivatives trans-[RuCl(pdma)(bpy)L 1]PF 6 (L 1=pyridine (py) 1, triphenylphosphine (PPh 3) 2, N-methylimidazole (mim) 3, acetonitrile (MeCN) 4, dimethylsulfoxide (dmso) 5 or pyrazine (pyz) 6). The related compound trans-[RuCl(pdma)(phen)(NO)][PF 6] 2 (phen=1,10-phenanthroline) reacts similarly to yield trans-[RuCl(pdma)(phen)L 1]PF 6 (L 1=py 8, PPh 3 9, mim 10 or pyz 11). The pyrazine complexes in 6 and 11 react with MeI at room temperature in acetone to afford trans-[RuCl(pdma)(L–L)(mpyz +)][PF 6] 2 (mpyz += N-methylpyrazinium, L–L=bpy 7 or phen 12, respectively). 3 reacts with an excess of a neutral ligand L 2 in the presence of stoichiometric AgCF 3CO 2 in water/acetone under reflux to afford high yields of the di-substituted derivatives trans-[Ru(pdma)(bpy)mim(L 2)][PF 6] 2 (L 2=mim 13, py 14 or MeCN 15) and 2 reacts similarly with AgCF 3CO 2 in water/MeCN to give trans-[RuCl(pdma)(bpy)PPh 3(MeCN)][PF 6] 2 ( 16). The complexes in 1– 16 exhibit intense d π(Ru II)→π*(L–L) and d π(Ru II)→π*(L 1/L 2) (L 1/L 2=py, pyz or mpyz +) metal-to-ligand charge-transfer absorption bands in the near-UV–visible region and are mildly photosensitive in solution. Solar irradiation leads to isomerization; for example 3 is converted into cis-[RuCl(pdma)(bpy)mim]PF 6 ( 17) over a period of ca. 100 h exposure to diffuse sunlight in acetone. Single crystal X-ray structures have been determined for 1, 2·DMF, 3, 12·3MeCN, 14·DMF and 17.

Synthesis, structures and properties of platinum(II) complexes of oligoacetylenic sulfides

A series of novel platinum(II) acetylide complexes incorporating sulfur-linked oligoalkynes have been prepared. The CuI-catalysed dehydrohalogenation reactions of the mono-protected dialkyne ligand HCCSCC(TIPS) (TIPS = Pri3Si) with trans-[Pt(PBu3)2Cl2], cis-[Pt(dppe)Cl2] or cis-[Pt(Me2bipy)Cl2] (Me2bipy = 4,4′-dimethyl-2,2′-bipyridine), in the presence of a base, readily produced trans-[Pt(PBu3)2{CCSCC(TIPS)}2] 1, cis-[Pt(dppe){CCSCC(TIPS)}2] 3 and cis-[Pt(Me2bipy){CCSCC(TIPS)}2] 7, respectively, in good yields. Similar synthetic procedures using a diacetylenic sulfide species HCCSCCCCSCC(TIPS) afforded trans-[Pt(PBu3)2{CCSCCCCSCC(TIPS)}2] 2 and cis-[Pt(dppe){CCSCCCCSCC(TIPS)}2] 4, both of which contain eight triple-bond units within the molecular entity. Two new metallo-end-capped derivatives trans-[Ph(Et3P)2Pt–CCSCC–Pt(PEt3)2Ph] 5 and trans-[Ph(Et3P)2Pt–CCSCCCCSCC–Pt(PEt3)2Ph] 6 were also synthesized in moderate yields by reactions of two equivalents of trans-[PtPh(Cl)(PEt3)2] and the diterminal acetylenic sulfides HCCSCCH and HCCSCCCCSCCH in a CuI/(Me3Si)2NH system. All of the compounds 1–7 have been characterized by IR, NMR (1H, 13C and 31P) and UV/VIS spectroscopies, luminescence measurements and mass spectrometry. The solid-state molecular structures of 5 and 7 have been established by X-ray crystallography.

MLCT and LMCT Transitions in Acetylide Complexes. Structural, Spectroscopic, and Redox Properties of Ruthenium(II) and -(III) Bis(σ-arylacetylide) Complexes Supported by a Tetradentate Macrocyclic Tertiary Amine Ligand

Ruthenium(II) complexes trans-[Ru(16-TMC)(C⋮CC6H4X-p)2] (X = OMe (1), Me (2), H (3), F (4), Cl (5); 16-TMC = 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane) are prepared by the reaction of [RuIII(16-TMC)Cl2]Cl with the corresponding alkyne and NaOMe in the presence of zinc amalgam. Low ν(C⋮C) stretching frequencies are observed for 1−5 and are attributed to the σ-donating nature of 16-TMC. The molecular structures of 1, 3, and 5 have been determined by X-ray crystal analyses, which reveal virtually identical Ru−C and C⋮C bond distances (mean 2.076 and 1.194 Å, respectively). The cyclic voltammograms of 1−5 show quasi-reversible RuIII/II and RuIV/III oxidation couples. Oxidative cleavage of the acetylide ligand in 3 by dioxygen affords [Ru(16-TMC)(C⋮CPh)(CO)]+ (6). Ruthenium(III) derivatives trans-[Ru(16-TMC)(C⋮CC6H4X-p)2]+ are generated in situ by electrochemical oxidation in dichloromethane or by chemical oxidation of 1−5 with Ce(IV). Their UV−visible absorption spectra show a vibronically structured absorption band with λmax at 716−768 nm. The vibrational progressions, which range from 1730 to 1830 cm-1, imply that the electronic transition involves distortion of the acetylide ligand in the excited state. An assignment of pπ(ArC⋮C) → dπ*(RuIII) charge transfer is proposed for this transition.

New studies on the reactivity of allyl difluorophosphate palladium complexes: synthesis of the first difluorophosphate metallocene derivatives

The reaction of [Pd(η 3-2Me-C 3H 4)(μ-PO 2F 2)] 3 1, previously synthesized by us, with P- or S-donor ligands leads to the new derivatives [Pd(η 3-2Me-C 3H 4)(PO 2F 2)L] (L=PMePh 2; P(OR) 3, R=Me, Et, Ph; SPPh 3) and [Pd(η 3-2Me-C 3H 4)L 2]PO 2F 2 (L=SPPh 3). The neutral and ionic derivatives with L=tetrahydrothiophene, were detected by 1H-NMR. The fluxional behavior of SPPh 3 complexes has been analyzed and a dissociation of SPPh 3 ligand evidenced. When 1 is made to react with M(η 5-C 5R 5) 2Cl 2 (M=Ti, R=H, Me; M=Mo, R=H) the new metallocene derivatives M(η 5-C 5R 5) 2(PO 2F 2) 2 are obtained. Using M(PPh 3)PF 6 (M=Ag, Cu) the complex [Pd(η 3-2Me-C 3H 4)(PPh 3) 2]PF 6 and M(PO 2F 2) x (M=Ag, x=1; M=Cu; x=2) are formed. A similar reaction takes place between [Pd(η 3-2Me-C 3H 4)(PO 2F 2)(PPh 3)] and Ag(ClO 4)PPh 3. With AuPPh 3PF 6 and 1 no reaction is observed. The derivatives trans-[PdCl(μ-Cl)(PR 3)] 2 (R=Ph, Cy) and [Pd(η 3-2Me-C 3H 4)(PhCN) 2]PO 2F 2 are formed after the reaction of [Pd(η 3-2Me-C 3H 4)(PO 2F 2)(PR 3)] and PdCl 2(PhCN) 2. 1 or [Pd(η 3-2Me-C 3H 4)(PO 2F 2)(PPh 3)], 2, does not react with weak acids However, HCl gives rise to [Pd(η 3-2Me-C 3H 4)Cl(PPh 3)] after the reaction with 2. HBF 4 also reacts with 1 or 2 and by means of 19F-NMR studies at low temperatures BF 4 − coordination has been observed when a non-coordinating solvent is used.

Enantioselective synthesis of cyclopentane derivatives using zirconium-catalyzed asymmetric cyclization

Cyclization of diene 2a using ( S)-(EBTHI)ZrBINOL ( 1) (10 mol %) and BuMgCl in THF upon heating gave cyclopentane derivative trans- 3a with 99% ee and cis- 3a with 86% ee in 69% and 31 % yields, respectively. In a similar manner, diene 10 gave cyclopentane derivative cis- 11 with 94% ee in 81% yield as a sole product.

4 + 2] Dimerization and Cycloaddition Reactions of alpha,beta-Unsaturated Selenoaldehydes and Selenoketones.

The reactions of alpha,beta-unsaturated aldehydes and ketones with bis(dimethylaluminum) selenide, (Me(2)Al)(2)Se, yield the corresponding alpha,beta-unsaturated selenoaldehydes and selenoketones. They are too unstable to be isolated in the monomeric form, but they undergo regioselective [4 + 2] dimerization via a "head-to-head" oriented transition state to afford diselenin derivatives (trans and cis isomers). Theoretical calculations at the density functional theory level show that this selectivity occurs because the "head-to-head" dimerization is thermodynamically favored over the "head-to-tail" by about 14 kcal/mol. Both dimerization reactions have low energy barriers: 1.5 and 2.8 kcal/mol for the former and 0.9 and 1.3 kcal/mol for the latter. In the presence of norbornadiene, these compounds function as 4pi heterodienes (C=C-C=Se) to give the respective cycloadduct products. On the other hand, they act as 2pi dienophiles (C=Se) in the reactions with cyclopentadiene except for selenoacrolein which serves as a 4pi diene and only one C=C bond (2pi) in cyclopentadiene is involved in the reaction. Theoretical calculations have been carried out in order to better understand these observations.

ChemInform Abstract: Predictive Study by Molecular Modeling to Promote Specific Probes of Glutamate Receptors, Using Methylated Cyclic Glutamic Acid Derivatives (trans‐ and cis‐ACPD). Comparison with Specific Agonists.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ammonia ruthenium complexes for the access to new hydrido, carbonyl and isocyanide ruthenium-alkynyl derivatives

The potential in preparative chemistry of the precursors trans-[Ru(NH 3)(CCR 1)(Ph 2PCH 2CH 2PPh 2) 2]PF 6 ( 3) has been studied. They offer a convenient access, by NH 3 displacement, to new functional alkynyl-ruthenium derivatives. Complexes 3 react with alkynes HCCR 2 to give unsymmetrical trans-Ru(CCR 1)(CCR 2)(dppe) 2 compounds 4a-c, and with sodium methoxide in methanol they open the route to a variety of mixed hydride complexes 5a-c, trans-Ru(H)(CCR 1)(dppe) 2. In contrast, with carbon monoxide or isocyanides CNR 3 (R 3:CH 2Ph, C 6H 11, Me 3C) they allow the preparation of cationic derivatives trans-(Ru(CO)(CCR 1)(dppe) 2]PF 6 ( 6a-c) or trans-[Ru(CNR 3)(CCR 1)(dppe) 2]PF 6 ( 7a-d).

Unprecedented Reactivity of 1-Alkynes with 2-Chloroethanol Promoted by Cationic Solvento(trifluoromethyl)platinum(II) Complexes. Synthesis of β-Alkoxyalkenyl Derivatives and X-ray Structure of trans-[Pt{C(H)C(Ph)OCH2CH2Cl}(CO)(PPh3)2][BF4]·Et2O

Reactions at ambient temperature of the solvento cationic trifluoromethyl complex trans-[Pt(CF3)(PPh3)2(solv)][BF4] with 1.5 equiv of 1-alkynes RC⋮CH (R = Ph, p-tolyl) and 2-chloroethanol afford in high yield the β-alkoxyalkenyl complexes trans-[Pt{C(H)C(R)OCH2CH2Cl}(CO)(PPh3)2][BF4] (R = Ph (1), p-tolyl (2)). In these reactions the CF3 group is also converted to a CO ligand. Complexes 1 and 2 were characterized by spectroscopic techniques and 1 also by an X-ray diffraction analysis. Reaction of the alkynyl complex trans-[Pt(CF3)(C⋮C-p-tolyl)(PPh3)2] with 2-chloroethanol and 1 equiv of HBF4 gives the acetylide-carbonyl derivative trans-[Pt(C⋮C-p-tolyl)(CO)(PPh3)2][BF4] (3), which was also formed by reaction of trans-[Pt(CF3)(C⋮C-p-tolyl)(PPh3)2] with aqueous HBF4. Possible mechanisms of these reactions are discussed.

Synthesis and properties of new tris(cyanoethyl)phosphine complexes of platinum (0,II), palladium (0,II), iridium (I) and rhodium (I).: Conformational analysis of tris(cyanoethyl)phosphine ligands

The tris(cyanoethyl)phosphine (tcep) complexes trans-[PtCl 2(tcep) 2], cis-[PtMe 2(tcep) 2], and trans-[PtMeCl(tcep) 2] are prepared by treatment of the corresponding [PtXY(cod)] (cod=1,5-cyclooctadiene) with tcep. Reduction of trans-[PtCl 2(tcep) 2] with NaBH 4 gives trans-[PtHCl(tcep) 2] which, in the presence of tcep and NEt 3, gives the coordinatively unsaturated platinum(0) complex [Pt(tcep) 3]. This coordinatively unsaturated species is also formed when [Pt(norbornene) 3] reacts with tcep. [Pt(tcep) 3] is very unreactive compared to its PEt 3 analogue: it is air-stable and does not react with further tcep to form an 18-electron species. It is protonated by HBF 4·OEt 2 to form [PtH(tcep) 3]BF 4. The complex trans-[PdCl 2(tcep) 2] is made from [PdCl 2(NCPh) 2] and tcep and the derivatives trans-[PdX 2(tcep) 2] (X=Br or I) are made by metathesis of the dichloro complex. Reduction of trans-[PdCl 2(tcep) 2] with LiOMe in the presence of tcep gave the palladium(0) complex [Pd(tcep) 3] which, like its platinum(0) analogue, undergoes exchange with free tcep on the NMR timescale. The palladium complex reacts with dibenzylideneacetone (dba) to form [Pd( η 2-dba)(tcep) 2]; the same product is formed in the reaction of [Pd( η 2-dba) 2] and tcep. Reaction of [Pd 2Cl 2( η 3-C 3H 3) 2] and tcep gives [PdCl(tcep)( η 3-C 3H 3)] or [Pd(tcep) 2( η 3-C 3H 3)]Cl depending on stoichiometry. The rhodium(I) and iridium(I) complexes trans-[MCl(CO)(tcep) 2], [MCl(tcep)(cod)] and [MCl(tcep) 3] are all readily made from tcep and an appropriate precursor. All new compounds have been fully characterised by a combination of elemental analysis, IR, 31P, 13C, 1H and 195Pt NMR spectroscopy. The crystal structure of [IrCl(tcep) 3] as a MeCN solvate shows a distorted square planar coordination geometry ( trans angles at Ir(I) ca. 164°, cis P–Ir–P av. 96°, cis P–Ir–Cl av. 85°). Analysis of the conformations of tcep ligands in this and other published tcep complexes shows there is a preference for conformations in which aaa, aag or g +g − (a=anti, g=gauche) arrangements of the three M–P–C–C chains are avoided.

Preparation, molecular structure and reactivity of mono- and di-nuclear sulfonato rhodium(I) complexes

The reaction of [Rh(η3-C3H5)(PPri3)2] 1 or [Rh(η3-CH2Ph)(PPri3)2] 2 with an equimolar amount of RSO3H (R = Me, p-tolyl, CF3, F, Camph) led to the formation of the monomeric sulfonatorhodium(I) complexes [Rh{η2-O2S(O)R}(PPri3)2] 3–7 in excellent yield. An alternative route for the preparation of 4 (R = p-tolyl) and 5 (R = CF3) is based on the reaction of PPri3 with the dinuclear compounds [{Rh(C8H14)2[µ-O2S(O)R]}2], which were obtained either from [{Rh(C8H14)2(µ-Cl)}2] 8 or [{Rh(C8H14)2(µ-OH)}2] 9 as starting materials. Compounds 3–7 react smoothly with hydrogen by oxidative addition to give the dihydridorhodium(III) complexes [RhH2{η2-O2S(O)R}(PPri3)2]. Moreover, on treatment of 3–6 with CO and C2H4 the chelating bond of the sulfonate ligand is partially opened and the carbonyl and ethene complexes trans-[Rh{η1-OS(O)2R}(L)(PPri3)2] (L = CO or C2H4) are formed. The bis(stibine)rhodium(I) derivative trans-[Rh{η1-OS(O)2CF3}(C2H4)(SbPri3)2] was obtained from [{Rh(C2H4)2[µ-O2S(O)CF3]}2] and SbPri3. Reaction of the compounds [Rh{η2-O2S(O)CF3}(olefin)(PPri3)] (olefin = C8H14 or C2H4) with benzene led to the displacement of the sulfonate ligand and to the formation of the half-sandwich-type complexes [Rh{η6-C6H6)(olefin)(PPri3)][CF3SO3] containing a rather labile benzene–rhodium bond. The preparation of the vinylidene complex trans-[Rh{η1-OS(O)C6H4Me-p}(CCHPh)(PPri3)2] is also described and the crystal and molecular structures of three compounds have been determined. The four-co-ordinate sulfonato complexes 3–6 are active catalysts in the C–C coupling reaction of ethene and diphenyldiazomethane. Besides the three isomeric 1∶1 adducts of C2H4 and CPh2, quite unexpectedly also the 2∶1 adduct 3,3-diphenylpent-1-ene is formed.

A Series of Carbonyl‐, Olefin‐, Alkyne‐, Hydrido‐, and Vinyliridium Complexes Containing Bulky Bifunctional Phosphanes iPr2PCH2X as Ligands

AbstractEtheneiridium(I) complexes of the general composition trans‐[IrCl(C2H4)L2] [L = iPr2PCH2CO2Me (2a), iPr2PCH2CO2Et (2b), iPr2P(CH2)3NMe2 (2c)] have been prepared either from [IrClL2] (3) or [IrCl(C2H4)2]2 (7) as starting materials. The corresponding carbonyl derivatives trans‐[IrCl(CO)L2] (6, 10, 11) are obtained along similar routes. Photolysis of trans‐[IrCl(C2H4)L2] (L = 2a, 2b) leads, by intramolecular C–H activation, to the formation of the octahedral hydrido(vinyl)iridium(III) compounds [IrHCl(CHCH2)(k‐L)(k2‐L)] (16, 17), which are highly fluctional in solution. Carbonyl(hydrido)(vinyl) complexes are accessible either from 16 or 17 and CO, or from trans‐[IrCl(C2H4)L2] (L = 2a) and the propargylic alcohol HCCCH(Ph)OH, respectively. Treatment of 3 or the corresponding dihydrido compound [IrH2ClL2] (4) with methyl vinyl ketone or methyl acrylate also yields hydrido(vinyl)iridium(III) complexes [IrHCl(CHCHX)L2] [X = C(=O)Me (18), C(=O)OMe (19)], in which instead of the CO function of the phosphanyl ester the carbonyl group of the vinylic moiety is coordinated to the metal. The reaction of 16 (L = 2a) with terminal alkynes HCCR (R = Ph, CO2Me) affords the structurally related alkynyl(hydrido)iridium(III) compounds [IrHCl(CCR)(k‐L)(k2‐L)] (28, 29), while from 16 and internal alkynes RCCR) the iridium(I) complexes trans‐[IrCl1(RCCR)L2] (30, 31) are obtained, Stepwise treatment of trans‐[IrCl(RCCR)L2] (6: L = 2a) with NaN(SiMe3)2, (ii) H2O, and (iii) HCl leads, in the coordination sphere of the metal center, to a conversion of iPr2PCH2CO2Me to iPr2PCH2CO2H via the isolated phosphanylenolate and phosphanylacetate complexes 32 and 33 as intermediates.