MeO2CC CCO2Me Research Articles

Carbon–Carbon Bond Formation at a Neutral Terminal Carbido Ligand: Generation of Cyclopropenylidene and Vinylidene Complexes

Olefin metathesis is an important tool for organic and polymer synthesis. However, some key functional groups are not tolerated even by Ru-based catalysts. We recently showed that vinyl esters can deactivate [Ru(CHPh)(PCy3)2Cl2] (1) [3] by quantitative formation of [Ru(C)(PCy3)2Cl2] (2) [4,5] A rare neutral terminal carbido complex, 2 is surprisingly stable and has few reported reactions. However, protonation of 2 by strong acid yields catalysts that rapidly initiate olefin metathesis. Thus, 2 is both a precursor to and a decomposition product of olefin metathesis catalysts. We see 2 as a potential source of a C1 fragment. Accordingly, we describe herein the first C C bond-forming reaction of this unusual compound. The terminal carbido ligand in 2 is a poor nucleophile, as shown by its failure to react with MeI, MeCOCl, and PhCH2Br. Although 2 does not react with a variety of alkenes and alkynes (see the Supporting Information), it reacts cleanly with MeO2CC CCO2Me (dimethyl acetylenedicarboxylate, DMAD) over 4 h in C6H6. A new blue-purple complex, 3, is formed as the carbido signal for 2 (C NMR: d= 471.8 ppm) is replaced by a new signal at d= 195.7 ppm. The H NMR spectrum evinces formation of a 1:1 adduct of 2 with DMAD. Formation of the cyclopropenylidene complex [Ru{=CC2(CO2Me)2}(PCy3)2Cl2] (Scheme 1) accounts for these observations. Several cyclopropenylidene complexes exist. Unlike 3, however, the cyclopropenylidene units in these complexes are substituted by phenyl or electrondonating groups. [Ru(C)(H2IMes)(PCy3)Cl2] (4 ; H2IMes= 4,5-dihydro-1,3-bis(mesityl)imidazol-2-ylidene) reacts similarly with DMAD, but the reaction is not clean since the product reacts further with DMAD before all of 4 has been consumed. However, 4 reacts more cleanly with HC CCO2Me (see the Supporting Information). Single-crystal X-ray diffraction confirmed the structure of 3. Figure 1 depicts a thermal ellipsoid plot of one of the two chemically equivalent but crystallographically independent molecules of 3 in the crystal. The data establish the expected connectivity in 3, but the large uncertainty associated with the Ru=C bond length of 1.846(10) A precludes comparison with those in related alkylidene complexes. The cyclopropenylidene ring lies in the Cl-Ru-Cl plane. The structure shows significant bond localization in the cyclopropenylidene fragment. These distances closely resemble those observed in free Scheme 1. Formation of 3 and ring-opening reactions. HBpin=pinacolborane, Ar=3,5-Me2C6H3.

Iridium-catalyzed addition of methanol to internal alkynes

The 18-crown-6 (18C6) ether adduct of sodium hexachloroiridate [Na(18C6)] 2[IrCl 6]· xH 2O ( 1) was found to catalyze an addition of methanol to a wide variety of internal alkynes RC CR′ (R/R′ = Et/Et, Me/Et, Me/ nPr, Me/ nBu, Me/ tBu, Me/Ph, Et/ nPr, Et/Ph) yielding the corresponding ketals and, due to the presence of water traces, their hydrolysis products (ketones). The regioselectivity of the addition of methanol to unsymmetrically disubstituted internal alkynes is governed by steric and electronic factors, being the highest in the case of pent-2-yne, hex-2-yne and hept-2-yne (80–85%). In the case of MeC CCO 2Me, an alkyne having an electron-withdrawing substituent, the addition was found to be 100% regioselective, with two methoxy groups going to the side away from an ester group. Furthermore, in the analogous addition of methanol to MeO 2CC CCO 2Me, besides the vinyl ethers ( E)/( Z)-MeO 2CC(OMe) CHCO 2Me, a cyclotrimerization product (C 6(CO 2Me) 6) was also observed. A comparison of the catalytic potential of other iridium compounds in the addition of methanol to hex-3-yne revealed that all examined ionic hexachloroiridates ([Na(18C6)] 2[IrCl 6]· xH 2O, Na 2[IrCl 6]·6H 2O, H 2[IrCl 6]·6H 2O, Na 3[IrCl 6]· xH 2O) were catalytically active, whereas [IrCl(CO)(PPh 3) 2] and [(IrCl 2Cp*) 2] were found to be almost inactive (degree of conversion <10%). However, the best results were obtained for the crown ether adduct 1. Moreover, in the addition of CD 3OD to hex-3-yne, [Na(18C6)] 2[IrCl 6]· xH 2O ( 1) was also found to catalyze a H/D exchange of protons in the neighborhood of a keto group or a quaternary carbon of a ketal with a degree of deuteration >97%.

On the reactivity of [IrCl(N 2)(PPh 3) 2] with alkynylsilanes – A new route to vinylidene iridium(I) complexes

The iridium dinitrogen complex [IrCl(N 2)(PPh 3) 2] ( 1) was found to react with alkynylsilanes RC CSiR 3 ′ to form the vinylidene iridium(I) complexes trans- [ IrCl { C CR ( SiR 3 ′ ) } ( PPh 3 ) 2 ] (R/R′ = Ph/Me, 2; Me/Me, 3; Bn/Me, 4; SiMe 3/Me, 5; SiEt 3/Et, 6; i Pr/Me, 7) and with Me 3SiC CC(O)R to yield the iridium η 2-alkyne complexes trans-[IrCl{η 2-Me 3SiC CC(O)R}(PPh 3) 2] (R = OEt, 9; Me, 11). Complex 9 was found to isomerize upon heating or upon UV irradiation yielding the vinylidene complex trans-[IrCl{ C C(SiMe 3)CO 2Et}(PPh 3) 2] ( 10). The reaction of 1 with Me 3SiC C C CSiMe 3 yielded the complex trans-[IrCl{ C C(SiMe 3)C CSiMe 3}(PPh 3) 2] ( 8), whereas with MeO 2CC CCO 2Me the iridacyclopentadiene complex [Ir{C 4(CO 2Me) 4}Cl(PPh 3) 2] ( 13) was formed. The complexes were characterized by means of 1H, 13C and 31P NMR spectroscopy as well as by IR spectroscopy and microanalysis.

Chemistry of Fischer-type rhenacyclobutadiene complexes. II. Reactions with alkynes and sulfonium ylides, and rearrangements induced by nitriles and pyridine

Further investigations into the chemistry of the rhenacyclobutadiene complexes (CO) 4Re(η 2-C(R)C(CO 2Me)C(X)) ( 1: R=Me, X=OEt ( 1a), O(CH 2) 3CCH ( 1b), NEt 2 ( 1c); R=CHEt 2, X=OEt ( 1d); R=Ph, X=OEt ( 1e)) are reported. Reactions of 1 with alkynes at reflux temperature of toluene and at ambient temperature either under photochemical conditions or in the presence of PdO yield ring-substituted η 5-cyclopentadienylrhenium tricarbonyl complexes, 2. The symmetrical alkynes R ′CCR ′ (R ′=Ph, Me, CO 2Me) afford the pentasubstituted complexes (η 5-C 5(Me)(CO 2Me)(OEt)(Ph)(Ph))Re(CO) 3 ( 2d), (η 5-C 5(Me)(CO 2Me)(OEt)(Me)(Me))Re(CO) 3 ( 2e), (η 5-C 5(Me)(CO 2Me)(OEt)(CO 2Me)(CO 2Me))Re(CO) 3 ( 2f), and (η 5-C 5(Me)(CO 2Me)(NEt 2)(CO 2Me)(CO 2Me))Re(CO) 3 ( 2i) on reaction with the appropriate 1, whereas the unsymmetrical alkynes R ′CCR″ (R ′=Ph; R″=H, Me) give either only one, (η 5-C 5(Me)(CO 2Me)(OEt)(Ph)H)Re(CO) 3 ( 2a)), or both, (η 5-C 5(Me)(CO 2Me) (OEt)(Ph)(Me))Re(CO) 3 ( 2b) and (η 5-C 5(Me)(CO 2Me)(OEt)(Me)(Ph))Re(CO) 3 ( 2c), (η 5-C 5(Ph)(CO 2Me)(OEt)(Ph)H)Re(CO) 3 ( 2g) and (η 5-C 5(Ph)(CO 2Me)(OEt)(H)(Ph))Re(CO) 3 ( 2h), of the possible products of [3 + 2] cycloaddition of alkyne to η 2-C(R)C(CO 2Me)C(X). Thermolysis of (CO) 4Re(η 2-C(Me)C(CO 2Me)C(O(CH 2) 3CCH)) ( 1b) containing a pendant alkynyl group proceeds to (η 5-C 5(Me)(CO 2Me)(O(CH 2) 3)H)Re(CO) 3 ( 2j), a η 5-cyclopentadienyl-dihydropyran fused-ring product. Competition experiments showed that each of PhCCH and MeO 2CCCCO 2Me reacts faster than PhCCPh with 1a. The results with unsymmetrical alkynes are rationalized by steric properties of substituents at the CC and ReC bonds and by a preference of ReC(Me) over ReC(OEt) to undergo alkyne insertion. A mechanism is proposed that involves substitution of a trans CO by alkyne in 1, insertion of alkyne into ReC bond to give a rhenabenzene intermediate, and collapse of the latter to 2. Complexes 1a and 1d undergo rearrangement in MeCN at reflux temperature to give rhenafuran-like products, (CO) 4Re(κ 2-OC(OMe)C(CHCR 2)C(OEt)) (R=H ( 3a) or Et ( 3b)). The reaction of 1d also proceeds in EtCN, PhCN, and t-BuCN at comparable temperature, but is slower (especially in t-BuCN) than in MeCN. In pyridine at reflux temperature, 1a undergoes a similar rearrangement, with CO substitution, to give (CO) 3(py)Re(κ 2-OC(OMe)C(CHCEt 2)C(OEt)) ( 4). A mechanism is proposed for these reactions. The sulfonium ylides Me 2SCHC(O)Ph and Me 2SC(CN) 2 (Me 2SCRR ′) react with 1a in acetonitrile at reflux temperature by nucleophilic addition of the ylide to the ReC(Me) carbon, loss of Me 2S, and rearrangement to a rhenafuran-type structure to yield (CO) 4Re(κ 2-OC(OMe)C(C(Me)CRR ′)C(OEt)) (R=H, R ′=C(O)Ph ( 5a); R=R ′CN ( 5b)). All new compounds were characterized by a combination of elemental analysis, mass spectrometry, and IR and NMR spectroscopy.

The crystal structure of [Mo(NCS)(CO) 2(η 3-C 3H 5)(NCMe) 2]·MeCN and the reactions of {Mo(CO) 2(η 3-C 3H 5) +} containing species with symmetric alkynes

In the solid-state [Mo(NCS)(CO) 2(η 3-C 3H 5)(NCMe) 2] · MeCN ( 1) contains a pseudo-octahedral arrangement of ligands about molybdenum, with carbonyls and nitriles in the equatorial plane and an N-bonded thiocyanate group trans to the allyl ligand. In refluxing methanol or acetonitrile both 1, and the analogous chloro-complex [MoCl(CO) 2(η 3-C 3H 5)(NCMe) 2] ( 2) catalytically convert PhCCPh to a mixture of hexaphenylbenzene and E, E-1,2,3,4-tetraphenylbutadiene. By contrast MeO 2CCCCO 2Me is not oligomerised. In methanol, complex 2 dimerises 1,4-diphenylbutadiyne to Z, E-1,4,5,8-tetraphenyl-1,7-octa-3,5-diene-1,7-diyne, whereas in the presence of base both the complex and the diyne, react preferentially with the solvent to generate the [Mo 2(CO) 4(η 3-C 3H 5) 2(OMe) 3] − anion and Z-1,4-diphenyl-3-methoxy-but-3-ene-1-yne, respectively.

Reactions of binuclear ruthenium–platinum μ-allenyl complexes with nucleophilic and electrophilic reagents. The characterization of two 1:1 adducts of L(PPh 3)Pt(μ-η 1:η 2α,β-C(Ph)CCH 2)Ru(CO)Cp (L=PPh 3, t-BuNC) and p-toluenesulfonyl isocyanate

Reactions of (PPh 3) 2Pt(μ-η 1:η 2 α,β-C(R)CCH 2)Ru(CO)Cp (R=H ( 1), Ph ( 2)) with Ph 2PCH 2CH 2CH 2PPh 2, PEt 3 and t-BuNC in THF at −78°C to room temperature afforded the substitution products L 2Pt(μ-η 1:η 2 α,β-C(R)CCH 2)Ru(CO)Cp (R=H, L 2=Ph 2PCH 2CH 2CH 2PPh 2 ( 3), R=Ph, L 2=Ph 2PCH 2CH 2CH 2PPh 2 ( 4), R=H, L 2=2PEt 3 ( 5), R=Ph, L 2=PPh 3 and t-BuNC ( 6)). No reaction was observed for 1 with Et 2NH or C 6H 11NH 2 and 2 with p-TolS(O) 2NH 2 in THF at reflux temperature. Complex 2 reacted with p-TolS(O) 2NCO (TSI) in toluene at −78°C to room temperature to yield two 1:1 addition products of the reactants: the γ-carbon substituted μ-allenyl (PPh 3) 2Pt(μ-η 1:η 2 α,β-C(Ph)CCHC(O)NHS(O) 2Tol- p) ( 7) and the [3+2] cycloadduct (PPh 3) 2Pt(μ-η 1:η 2-CC(Ph)N(S(O) 2Tol- p)C(O)CH 2)Ru(CO)Cp ( 8). Complexes 4 and 6 afforded with TSI, under essentially similar conditions, only [3+2] cycloadducts, L 2Pt(μ-η 1:η 2-CC(Ph)N(S(O) 2Tol- p)C(O)CH 2)Ru(CO)Cp (L 2=Ph 2PCH 2CH 2CH 2PPh 2 ( 9), PPh 3 and t-BuNC ( 10)). All products were characterized by a combination of IR and NMR ( 1H, 13C{ 1H} and 31P{ 1H}) spectroscopy, FAB MS and elemental analysis. The structures of 7 (as 7·C 3H 6O) and 10 were determined by single-crystal X-ray diffraction analysis. Reactions of 2 with trans-NCCHCHCN (L) and of 1 with the alkynes MeO 2CCCCO 2Me, MeO 2CCCMe, PhCCH and PhCCPh (L) resulted in the formation of the mononuclear metal complexes Cp(CO) 2RuC(R)CCH 2 (R=H, Ph) and (PPh 3) 2PtL. The reverse of this fragmentation reaction occurred when Cp(CO) 2RuCHCCH 2 was treated with (PPh 3) 2Pt(PhCCPh). No reaction was observed between 2 and each (CN) 2CCPh 2 and MeS(O) 2NSO in benzene or toluene on heating. The η 1-allenyl Cp(CO) 2RuC(Ph)CCH 2, obtained in this study, is a new compound.

A series of triisopropylstibine ruthenium and osmium complexes including the X-ray crystal structure of [RuCl 2(CO)(Sb iPr 3) 3] and [RuCl 2(CCCPh 2)(CO)(Sb iPr 3) 2

With [( p-cym)RuCl 2] 2 ( 1) as the starting material, the halfsandwich-type complexes [( p-cym)RuCl 2(Sb iPr 3)] ( 2) and [( p-cym)RuCl(Sb iPr 3) 2]PF 6 ( 3) were prepared. Treatment of RuCl 3·3H 2O in ethanol gave, after addition of Sb iPr 3, the monocarbonyl compound [RuCl 2(CO)(Sb iPr 3) 3] ( 4), which reacted with CO by ligand exchange to yield [RuCl 2(CO) 2(Sb iPr 3) 2] ( 5). The reaction of RuCl 3·3H 2O in ethanol, in the presence of Na 2CO 3, afforded the chloro(hydrido) derivative [RuHCl(CO)(Sb iPr 3) 3] ( 6). Analogously, using OsCl 3·3H 2O as the starting material, the chloro(hydrido)osmium complex [OsHCl(CO)(Sb iPr 3) 3] ( 8) was prepared. The reactions of 8 with C 2H 4, C 2(CO 2Me) 2 and NaBH 4 led to the formation of compounds 9, 10 and 11, which all contain the Os(Sb iPr 3) 2 unit as a building block. While treatment of 6 with C 2(CO 2Me) 2 yielded the substitution product [RuHCl(CO)(MeO 2CCCCO 2Me)(Sb iPr 3) 2] ( 14), the corresponding reaction of 6 with HCCPh and HCCCPh 2OH afforded the alkynyl and allenylidene ruthenium(II) complexes [RuCl(CCPh)(CO)(Sb iPr 3) 3] ( 16) and [RuCl 2(CCCPh 2)(CO)(Sb iPr 3) 2] ( 17), respectively. Compounds 4 and 17 were characterized by X-ray crystal structure analysis.

The reaction of ( μ3-CCO 2R)Co 2M(CO) 8L (M = Co, Mo, W; L = CO, MeCp; R = Me, Et) with Na 2[Fe(CO) 4]. X-ray crystal structure analysis of (EtO 2CCCCO 2Et)Co 4(CO) 10 and (MeO 2CCCCO 2Me)FeCo 2(CO) 9

The reactions of clusters [(μ 3- CCO 2 Et) Co 2 M( CO) 8( MeCp)][ M = Mo ( 2 a ), W ( 2 b )] , derived from the reactions of ( μ 3-CCO 2Et)Co 3(CO) 9 with Na[M(CO) 3(MeCp)], with Na 2[Fe(CO) 4] in THF at reflux not only gave the expected metal fragment exchange products [(μ 3- CCO 2 Et) FeCoM(CO) 8( MeCp) H][ M = Mo ( 3 a ), W ( 3 b )] , but also gave the unexpected compounds [(μ 3- CCO) FeCoM(CO) 8( MeCp)][ M = Mo ( 4 a ), W ( 4 b ) . It is suggested that the formation of two kinds of compounds resulted from two competitive reactions of the intermediates [( μ 3-CCO 2Et)FeCoM(CO) 8(MeCp)] − with acidic treatment: the one is the protonic reaction of the intermediate giving the clusters 3a and 3b; the other is the intermolecular nucleophilic substitution reaction of the intermediate by the catalysis of H +, giving the clusters 4a and 4b. Under the different reaction temperature and molar ratio of the starting materials, the reactions of (μ 3- CCO 2 R) Co 3( CO) 9[ R = Me ( 1 1 ), Et ( 1 b )] [ R = Me ( 6 a ) , Et ( 6b)] abd (RO 2CCCCO 2R)FeCo 2(CO) 9[R = Me ( 7a), Et ( 7b)] besides the expected exchange products (μ 3- CCO 2 R) FeCo 2( CO) 9 H[ R = Me ( 5 a ), Et ( 5 b )] . This is the first example that the reaction of 6a and 6b with Na 2[Fe(CO) 4] could produce the clusters 7a and 7b. The clusters (EtO 2CCCCO 2Et)Co 4(CO) 10 and (RO 2CCCCO 2R)FeCo 2(CO) 9 were determined structurally by X-ray diffraction.

The chemistry of compounds of the type Ru(η 5C 5Me 4Et)(CO) 2X (XCl, Br or I)

The title compounds react with unidentate ligands, L, containing either phosphorus or arsenic donor atoms to yield the corresponding compounds of the type Ru(η 5C 5Me 4Et)(CO)LX; with didentate phosphorus donor ligands the major species formed is the bridged complex {Ru(η 5C 5Me 4Et)(CO)X} 2{Ph 2P(CH 2) n PPh 2} n = 1, X = Br; n = 2, X = Cl). In contrast, unidentate ligands containing nitrogen donor atoms such as pyridine did not react with Ru(η 5C 5Me 4Et)(CO) 2Cl although reaction with 1,10-phenanthroline or diethylenetriamine yielded the ionic products [Ru(η 5C 5Me 4Et)(CO)L] +Cl − (L = phen or (NH 2CH 2CH 2) 2NH). Reaction of Ru(η 5C 5Me 4Et)(CO) 2Br with AgOAc yielded the corresponding acetato complex Ru(η 5C 5Me 4Et)(CO) 20Ac. Ru(η 5 C 5Me 4Et)(CO) 2X reacts with AgY (Y = BF 4 or PF 6) in either acetone or dichloromethane to give the useful solvent intermediates [Ru(η 5C 5Me 4Et)(CO) 2(solvent)] +Y −, which readily react with ligands L to yield ionic derivatives of the type [Ru(η 5C 5Me 4Et)(CO) 2L] +Y − (where L = CO, NCMe, py, C 2H 4 or MeO 2CCCCO 2Me).

Bis(di-t-butylphosphino)methane complexes of rhodium: homogeneous alkyne hydrosilylation by catalyst-dependent alkyne insertion into RhSi or RhH bonds. Molecular structures of the dimer [(dtbpm)RhCl] 2 and of the silyl complex (dtbpm) Rh[Si(OEt) 3](PMe 3)

The homogeneous, Rh-catalysed hydrosilylation of but-2-yne with triethoxysilane has been studied. All rhodium complexes employed as catalyst precursors contain tBu 2PCH 2P tBu 2 (“dtbpm”) as a chelating ligand. The crystal and molecular structure of the dimer [(dtbpm)RhCl] 2 ( 10) has been determined by X-ray diffraction. Complex 10 is shown to be a sluggish catalyst in hydrosilylation reactions of hex-1-ene, whereas but-2-yne is hydrosilylated more rapidly. A much more efficient and highly selective catalyst is 10 with added PPh 3, equivalent to the use of monomeric (dtbpm)RhCl(PPh 3). ( E)-2-Triethoxysilylbut-2-ene is formed exclusively and with high turnover numbers in this case. For both 10 and its PPh 3 derivative, the 14-electron fragment [(dtbpm)RhCl], formed by dissociation processes, is the most likely active intermediate in a Harrod-Chalk-type catalytic cycle. The PPh 3 dissociation equilibrium has been studied in detail for (dtbpm)RhCl(PPh 3) and its thermodynamic parameters have been determined. With rhodium alkyl complexes as catalyst precursors, a different type of alkyne hydrosilylation catalysis, involving direct alkyne insertion into the RhSi bond of an intermediate rhodium silyl complex, (dtbpm)Rh[Si(OEt) 3](PMe 3) ( 14), has been found. Complex 14 was synthesized independently from (dtbpm)RhMe(PMe 3) and characterized by X-ray diffraction. It is an equally active catalyst itself, yielding ( E)-2-triethoxysilylbut-2-ene as the major product (90%) from but-2-yne and HSi(OEt) 3 (turnover number 1000 per 30 min). The insertion step of the alkyne into the RhSi bond of 14 and the formation of two stereoisomeric rhodium vinyl complexes were established independently for MeO 2CCCCO 2Me as a more reactive alkyne substrate. A catalytic cycle is proposed for this unprecedented hydrosilylation reaction. The synthesis of the ν 3-benzyl complex (dtbpm)Rh( η 3-CH 2C 6H 5) ( 23) is described. This compound allows an alternative, more efficient access to the new silyl complex (dtbpm)Rh[Si(OEt) 3](PMe 3).

A high-yield synthesis of 3-carboethoxy-4-trifluoromethylfuran and some Diels-Alder reactions of this furoate with acetylenic dienophiles

The reaction of furan with ethyl 4,4,4-trifluorobut-2-ynoate ( 1) (1.2:1 molar ratio) in vacuo at 40 °C gives the 1:1 adduct oxanorbornadiene ( 3) (70%) and the 2:1 adduct ( 5) as the endo,exo ( 5a) (16%) and exo,exo ( 5b) (10%) isomers; at 20 °C, using an excess of ester 1, the yield of 1:1 adduct 3 is increased to 93%. Catalytic hydrogenation ( Pd C/Me 2CO ) of1:1 adduct 3 with control of the hydrogen uptake affords either the oxanorbornane 9 (89%) or the oxanorbornene 10 (90%), and flow pyrolysis of compound 10 at 400 °C in nitrogen gives 3-carboethoxy-4-trifluoromethylfuran ( 2) (89%). Diels-Alder cycloaddition reactions of furan 2 with the alkynes CF 3CCCF 3 (100 °C), 1 (100 °C) and MeO 2CCCCO 2Me (120 °C) in solvent CH 2Cl 2 afford the 1:1 adducts 13 (95%), 14 (47%) plus 15 (45%), and 16 (92%), respectively, but reaction with ethyl propynoate does not take place at or below 120 °C and at 150 °C a complex product mixture is obtained. The 1:1 adduct 3 undergoes reaction with triflic acid in solvent CH 2Cl 2 heated under reflux to give 2-carboethoxy-3-trifluoromethylphenol ( 23) (31%) and 3-carboethoxy-2-trifluoromethylphenol ( 24) (48%) and with concentrated sulfuric acid under the same conditions to afford phenols 23 (21%) and 24 (32%), but the oxanorbornadiene 13 does not undergo reaction with triflic acid at temperatures up to 80 °C.

Metallacycle formation through the linking of an alkyne with phosphido and acetyl groups at an iron centre: X-ray structure of [Cp [formula omitted]}] (Cp =η 5-C 5H 5)

The diphenylphosphine ligand of [CpFe(CO)(PPh 2H)(COMe)] (Cp  η 5-C 5H 5) can be deprotonated with DBU (DBU = 1, 8-diazabicyclo[5.4.0]undec-7-ene) or n-butyllithium; subsequent alkylation with RI (R  Me, Et) gives the complexes [CpFe(CO)(PPh 2R)COMe)]. Reaction of the anionic phosphido complex with the electrophilic alkyne methyl propiolate (HOCCO 2Me) followed by reprotonation with CH 3COOH gives the vinylphosphine complex [CpFe(CO)(PPh 2CHCHCO 2Me) (COMe)], whereas a similar reaction sequence with dimethyl acetylenedicarboxylate (DMAD, MeO 2CCCCO 2Me) produces two isomers of the complex [Cp Fe(CO){Ph 2PCH(CO 2Me)C(CO 2Me)C(Me)O }], in which linking of the alkyne with both the phosphido and acetyl ligands has occurred to form a six-membered metallacycle. The structure of one of the two isomers has been determined by X-ray diffraction and shows that the metallacyclic ring is bound to the iron atom through the phosphorus and the carbonyl oxygen of the acetyl group, and adopts a boat conformation in the solid state.

Structural aspects of the osmium and ruthenium clusters [M 3(CO) 10(alkyne)] and related substituted compounds

The synthesis and single-crystal structure determination of the cluster [Os 3(CO) 10(μ 3-MeO 2CC 2CO 2Me)], derived from the bis-acetonitrile complex [Os 3(CO) 10(MeCN) 2] and the alkyne MeO 2CCCCO 2Me, are described. The alkyne CC bond is approximately parallel to an OsOs edge and one CO ligand is bridging. Distinct distortions from an idealized structure with C s symmetry are apparent, as previously noted for this class of compound, and a comparison with nine other reported structures of related osmium and ruthenium clusters is presented. Essentially all situations are encountered between two extremes: a structure close to C s symmetry with a symmetrical μ-CO and a parallel alkyne and another with only terminal CO and a rather more distorted alkyne coordination. There is a clear correlation between the geometry of the bridging CO, metal-metal distances, and the arrangement of the μ 3-alkyne. IR spectra indicate that there are different structures in solution in some cases.

Reactivity of the metallophosphines [CpM(CO) 3PPh 2] (Cp  η-C 5H 5, M  Mo, W) towards alkynes. X-ray crystal structure of [CpMo(CO) 2 {Ph 2PCH(Ph)CO}

The mononuclear phosphido complexes [CpM(CO) 3PPh 2] (Cp  η-C 5H 5; M  Mo, W) react with the electron dificient alkynes methyl propiolate (HCCCO 2Me) and dimethyl acetylenedicarboxylate (DMAD, MeO 2CCCCO 2Me) to give the metallacyclic complexes [CpM(CO) 2{Ph 2PCR 1C(R 2)CO}] (R 1  H, CO 2Me; R 2 CO 2Me), which contain a five-membered chelate ring formed by the linking of the phosphido group, the alkyne, and one CO ligand. The molybdenum phosphido complex, though not the tungsten, also reacts with phenylacetylene to give the corresponding metallacycle [CpMo(CO) 2-{Ph 2PCHC(Ph)CO}], which has been characterised by a single crystal X-ray structure determination. This complex can also be produced by the action of PPh 2Cl on the dinuclear η-acetylide Li[Cp 2Mo 2(η-CCPh)(CO) 4].

Reaction of (Ph 3P) 2PtS 4 with MeO 2CCCCO 2Me: synthesis and structure of (dimethyldimercaptomaleato(2−)- S, S′)bis(triphenylphosphine)platinum(II)

Addition of excess dimethyl acetylene dicarboxylate to (PPh 3) 2PtS 4 gave a black-dark-red solution. Purple crystals obtained from this solution were shown by single crystal X-ray crystallography to be the title compound; the sulfur has added to the acetylene to give dimethyldimercaptomaleate coordinated to Pt. The purple is attributed to an intensely colored impurity. Space group P 1 ; a=11.713(5); b=14.733(5); c=15.774(6) Å, α=129.35(2); β=106.40(3); λ=93.44(3)°; V=1912(1) Å 3; Z=2; R=0.0339 and R w=0.0326 for 6177 reflections with F o⩾3σ(F o) and 388 parameters.

Die Koordinationschemie CS-funktioneller Verbindungen: VIII.Addition aktivierter Alkine an Wolfram-CS 2-Komplexe und Aufbau tetraedrischer Methylidindicobaitwolfram-Cluster

Compounds of the type [W(CO) 3(diphosphine)(CS 2)] add activated alkynes (MeO 2CCCCO 2Me, CF 3CCCF 3, HCCCO 2Me) to give complexes of 1,3-di-thiole-2-ylidenes. The unstable intermediate [W(CO) 3(PMe 3) 2(CS 2)] can be trapped by a similar reaction. The cyclic dithiocarbene complexes thus formed undergo ring opening with Co 2(CO) 8 to give tetrahedral methylidyne dusters, one of which has been characterized by X-ray structure analysis. [Co 2W(dmpe)(CO) 7( 3-CSC(CF 3)C(CF 3)μ 2-S)] crystallizes orthorhombic (a 1058.9(3), b 1584.1(5), c 3380.2(8) pm) with 8 molecules in the unit cell, ϱ 2.08 mg/mm 3.

Insertion reactions of carbonylbis(η-cyclopentaidenyl)-hydridoniobium with activated acetylenes

Carbonylbis(η-cyclopentadienyl)hydridoniobium (I) Cp 2NbH(CO) reacts with MeO 2CCCCO 2Me at −80°C to give predominantly the ( Z)-alkenyl complex Cp 2Nb(CO)[η 1-( Z)-C(CO 2Me)CH(CO 2R)] (II), together with the E isomer (III) in a 3 1 ratio. Slow isomerization at ambient temperature produces a 1 5 equilibrium mixture. The structure of II was determined by X-ray diffraction methods. Activated terminal acetylenes HCCR undergo α-insertion to yield the alkenyl complexes Cp 2Nb(CO)[η 1-(CRCH 2)] (IV, R = CO 2, Me; V, R = C(O)Me).

Photochemical reactivity of Os 3(CO) 12 and thermal activation of diosmacyclobutanes towards alkynes

Long wavelength photolysis of Os 3(CO) 12 and MeO 2CCCCO 2Me (DMAD) in benzene gives, as isolable products, Os 2(CO) 8(μ-η 1,η 1-DMAD) ( 4a) and Os 2(CO) 6(DMAD) 4 ( 5). Structural work confirms the diosmacyclobutene arrangement in 4a and reveals a unique coupling of alkynes in 5. The potentially more general thermal reaction between preformed diosmacyclobutane and alkynes gives improved yields of 4a and allows the isolation, albeit in low yield, of Os 2(CO) 8(μ-η 1,η 1-CF 3CCCF 3) ( 4b).

Transition metal complexes with bidentate ligands spanning trans‐positions. Part XIV. Some complexes of 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene with platinum (0) and their reactivities

AbstractThe ligand 2,11‐bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L  C2H4, CH2CHCO2Me, PhCCPh, MeCCMe, MeO2CCCCO2Me, (i‐Pr)O2CCCCO2(i‐Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans‐[PtX(R)(1)] by oxidative addition of RX (RX  PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.

Metallorganische Diazoalkane XVII. 1,3-dipolare cycloadditionen von heterometalldiazoalkenen: untersuchungen zur metallotropie in organometall-iso-pyrazolen und die kristallstruktur eines N-(trimethylstannyl)dimethylarsen[bis-carboxymethoxy]pyrazols

Heterometal-diazoalkanes Me 3Si(L nM)C N2 and Me 2As(L nM)CN 2 (L nM = Me 3Sn, Me 3Pb) react in a 1,3-dipolar cycloaddition (Huisgenreaction) with MeO 2CCCCO 2Me forming organometallic substituted isopyrazols which isomerize spontaneously to the more stable pyrazoles by metallotropic rearrangements of methylmetal groups from carbon to nitrogen atoms: ( 1H, 13C, 29Si, 119Sn, 207Pb) NMR and 119Sn-Mössbauer data support the concept of carbon-to-nitrogen group migration. The structure of N-(trimethylstannlyl)dimethylarsino-bis(carbomethoxy)pyrazol (III) was determined by single-crystal X-ray diffraction methods: III crystallizes in the triclinic space group P 1 with Z = 2, calc. density 1.732 g/cm 3; a 1002 pm, b 1204 pm, c 765 pro, α 103.2°, β 94.1°, γ 81.8°. Refining the structure with anisotropic temperature factors for all non-hydrogen atoms yield a conventional R = 0.055. Characteristic features of the structure are (i) the ideal planarity of the pyrazol ring system, (ii) the indirect evidence of a steric requirement of the “lone pairs” at the arsenic atoms and (iii) an intermolecular interaction of tin and carbonyl-oxygen atoms, rendering the tin atoms a fivefold coordination sphere; this is in full agreement with typical 119Sn-Mössbauer results.