Equiv Of n-BuLi Research Articles

Deprotonation-substitution reactions of cyclic methylphenylphosphazenes: synthesis and structures of nongeminal P-ethyl, P-phenyl cyclotriphosphazenes.

The deprotonation-substitution reactions of both the cis and trans isomers of nongeminally substituted [(Me)(Ph)P=N](3) were investigated. Treatment of the trans isomer, 1, with 3 equiv of n-BuLi followed by 3 equiv of MeI gave only nongeminal trans-[(Et)(Ph)P=N](3), 3, while the same reaction sequence on cis-[(Me)(Ph)P=N](3), 2, gave a mixture of nongeminal di- and trisubstitution products, cis-Et(2)MePh(3)P(3)N(3), 4, and cis-Et(3)Ph(3)P(3)N(3), 5. These trimers were separated by column chromatography. No changes in the stereochemistry of the rings occurred during these reactions. Compound 4 was also prepared using 2 equiv of the reactants and was then converted to 5 by treatment with a single equivalent of BuLi and MeI. Thermal analysis of the new cyclic trimers indicates that ring-opening polymerization does not occur and that sublimation occurs at ca. 300 degrees C. The structures of 4 and 5, obtained by X-ray diffraction, illustrate the basketlike shape of these molecules with an aromatic bowl formed by the phenyl rings on the top rim, while the structure of 3 clearly shows the trans orientation of the substituents. Crystal data for trans-Et(3)Ph(3)P(3)N(3), 3, at 20 degrees C are as follows: C(24)H(30)N(3)P(3) monoclinic, a = 14.273(2) A, b = 9.370(2) A, c = 19.600(3) A, beta = 107.16(1) degrees, P2(1/n), Z = 4. Crystal data for cis-Et(2)MePh(3)P(3)N(3), 4, at 20 degrees C are as follows: C(23)H(28)N(3)P(3), triclinic, a = 10.276(2) A, b = 10.699(2) A, c = 11.925(2) A, alpha = 72.07(2) degrees, beta = 73.79(1) degrees, gamma = 85.87(1) degrees, P1, Z = 2. Crystal data for cis-Et(3)Ph(3)P(3)N(3), 5, at 20 degrees C are as follows: C(24)H(30)N(3)P(3) monoclinic, a = 29.488(2) A, b = 9.8391(1) A, c = 21.172(2) A, beta = 126.30(1) degrees, C2/c, Z = 8.

Facile preparation and synthetic applications of LiCH 2C(CF 3) 2OLi

Bromohydrin BrCH 2C(CF 3) 2OH readily reacts with two equivalents of n-BuLi at −78 °C to produce the corresponding dilithium derivative LiCH 2C(CF 3) 2OLi in high yield. This dilithiated derivative reacts selectively, acting as a C-nucleophile, with a variety of electrophiles such as R 2PCl, carbonyl compounds, and epoxides, to give electron-deficient phosphines R 2PCH 2C(CF 3) 2OH, 1,3- and 1,4-diols, correspondingly.

Ruthenium Complexes Containing Bis(diarylamido)/Thioether Ligands: Synthesis and Their Catalysis for the Hydrogenation of Benzonitrile

Treatment of the thioethers (RNH-o-C6H4)2S (H2[R2NSN]; R = Xy, Xyf; Xy = 3,5-Me2C6H3, Xyf = 3,5-(CF3)2C6H3) with 2 equiv of n-BuLi followed by addition of 0.5 equiv of [(η6-C6H6)RuCl2]2 in THF gave the bis(diarylamido)/thioether complexes [(η6-C6H6)Ru[R2NSN]] (R = Xy (1a), R = Xyf (1b)) in moderate yields. In the presence of 1a (1 mol %) and PCy3 (2 mol %; Cy = cyclohexyl), benzonitrile was catalytically hydrogenated to give benzylamine (72%) and benzylidenebenzylamine (27%) at 80 °C and 30 atm, while the hydrogenation with 1b as a catalyst precursor resulted in the formation of benzylamine (37%) and benzylidenebenzylamine (51%) under the same reaction conditions. The yield of benzylamine was improved up to 92% by using a catalyst mixture of 1a (1 mol %)/PCy3 (2 mol %)/t-BuONa (10 mol %). On the other hand, the reaction of 1a with excess PMe3 afforded the tris(trimethylphosphine) derivative [(PMe3)3Ru[Xy2NSN]] (2). Treatment of 2 with excess PhCN, MeCN, or N2H4·H2O resulted in the replacement of a PMe3 li...

Synthesis of a novel potential tridentate anthracene ligand, 1,8-bis(dimethylamino)-9-bromoanthracene, and its application as chelate ligand for synthesis of the corresponding boron and palladium compounds.

A novel potential tridentate ligand, 1,8-bis(dimethylamino)-9-bromoanthracene, was synthesized. The key steps are as follows: 1) dimethylamination of 1,8-dibromo-9-methoxyanthracene by a modified Buchwald's method to afford 1,8-bis(dimethylamino)-9-methoxyanthracene, and 2) reduction of the methoxy group by LDBB (lithium di-tert-butylbiphenylide) followed by treatment with BrCF2CF2Br. The corresponding 1,8-bis(dimethylamino)-9-lithioanthracene, which should be a useful versatile tridentate ligand, could be generated by treatment of the bromide with one equivalent of nBuLi. The lithioanthracene reacted with B-chloroborane derivatives to give three 9-boryl derivatives. Although we recently reported that the crystal structure of 1,8-dimethoxy-9-B-catecholateborylanthracene was a symmetrical compound with the almost identical two O-B distances (2.379(2) and 2.441(2) A), the newly prepared 1,8-bis(dimethylamino)-9-borylanthracene derivatives clearly have unsymmetrical structures with coordination of only one NMe2 group toward the central boron atom. However, the energy difference between the unsymmetrical and symmeterical structures was found to be very small based on 1H NMR measurements, in which symmetrical anthracene patterns in the aromatic region (two kinds of doublets and a triplet) and a sharp singlet signal of the two NMe2 groups were observed even at -80 degrees C. 1,8-Bis(dimethylamino)-9-bromoanthracene itself can be a versatile ligand for transition metal compounds. In fact, direct palladation of the bromide took place by the reaction with [Pd2(dba)3].CHCl3 in THF to give the 9-palladated product. X-ray crystallographic analysis of the Pd compound showed that the square planar palladium atom was coordinated in a symmetrical fashion by both NMe2 groups (Pd-N bonds are 2.138(5) and 2.146(5) A).

Generation of 1-azapentadienyl anion from N-(tert-butyldimethylsilyl)-3-buten-1-amine.

N-(tert-Butyldimethylsilyl)-3-buten-1-amine undergoes allylic deprotonation at the 2-position when exposed to 2 equiv of nBuLi in THF. This allylic anion undergoes lithium hydride elimination to generate a 1-azapentadienyl anion. The anion is generated cleanly and completely.

Synthesis, Structural Characterization, and Reactivity of Organolanthanide Complexes Derived from a New, Versatile Boron-Bridged Ligand, iPr2NB(C9H7)(C2B10H11)

New boron-bridged ligands incorporating both indenyl and carboranyl moieties have been prepared. Reaction of iPr2NB(C9H7)Cl with 1 equiv of Li2C2B10H10 gave, after treatment with 1 equiv of n-BuLi, the dilithium salt [iPr2NB(C9H6)(C2B10H10)]Li2(OEt2)2 (1), which was conveniently converted into its neutral counterpart iPr2NB(C9H7)(C2B10H11) (2) via reaction with excess C5H6. Mixing 1 and 2 in a 1:1 molar ratio quantitatively afforded the monolithium salt [iPr2NB(C9H6)(C2B10H11)]Li(THF)2 (3). Treatment of LnI2 with 1 equiv of 1 generated the trivalent organolanthanide complexes meso-[{η5:σ-iPr2NB(C9H6)(C2B10H10)}2Ln][Li(S)n] (Ln = Sm, Yb; S = THF, n = 4; S = DME, n = 3), which was also prepared in a much higher yield by reaction of LnI2 with 1 equiv of 1 followed by treatment with 1 equiv of 3. Both inter- and intramolecular electron-transfer pathways are proposed for these reactions. Reaction of LnCl3 with 1 or 2 equiv of 1 gave the same ionic complexes meso-[{η5:σ-iPr2NB(C9H6)(C2B10H10)}2Ln][Li(S)n] (Ln = Nd, Y, Yb; S = THF, n = 4; S = DME, n = 3). Silylamine elimination reactions of 2 and Ln[N(SiHMe2)2]3(THF)2 resulted in clear formation of [η5:σ-iPr2NB(C9H6)(C2B10H10)]LnN(SiHMe2)2(THF)2 (Ln = Nd (8), Er (9), Y (10)). Treatment of 8 with Me3NHCl or Me3SiCl led to the isolation of 2 and NdCl3(DME)2 (11), respectively. The new complexes were fully characterized by various spectroscopic data and element analyses. Some were further confirmed by single-crystal X-ray analyses. Complex 8 is an active catalyst for the polymerization of methyl methacrylate (MMA) in toluene, affording syn-rich poly(MMA)s.

In Situ Generation of 1-Propyne: A Useful Introduction of 1-Propyne on Unsaturated Halogenated Compounds through the Sonogashira Reaction

Reaction of (E/Z)-1-bromopropene with exactly 1.42 equivalents of nBuLi followed by addition of water produces in situ a THF solution of propyne. Addition of a vinylic or aromatic halogenated substrates, Pd(PPh 3 ) 2 Cl 2 , CuI and an amine to this solution give high yield of the corresponding coupling product bearing a propyne moiety. This practical procedure avoids the use of expensive and inflammable propyne gas which need a special apparatus for bubbling it into the reaction flask.

Structural and vibrational characterization of the mono and dilithiated species derived from phenylacetonitrile in THF by infrared and Raman spectroscopy and density functional theory calculations

The structures and spectra of mono and dianionic species derived from PhCH 2CN under the action of an organic base LHMDS or n-BuLi in THF solution have been investigated by vibrational spectroscopy and DFT calculations. The assignments previously proposed for the monoanion, the bridged, linear and dimeric monoanionic ion pairs compare well with the calculated ones. The addition of HMPA to a THF solution of PhCHCNLi leads to the formation of an HMPA solvated linear ion pair, distinguishable from the bridged ion pair by the wavenumber of the 8a ν(CC) phenyl ring mode. The calculated structure of the phenylacetonitrile anion in the (PhCHCNLi, CH 3Li) mixed dimer or ‘Quadac’ is very similar to that in the linear ion pair or in the dimer and to that observed by X-ray in (PhCHCNLi, [CH(CH 3) 2] 2NLi) ‘Quadac’. The structure of the anion is planar, indicating a charge delocalization from the benzene ring to the CHCN group. The calculated spectra of the free, mono and dilithiated dianionic species compare well with the experimental ones of the species formed under addition of more than one equivalent of n-BuLi. The structure of the CCCN 2− group is very close to that of an imine. The ν(CN) bands of the free, mono and dilithiated dianionic species are located at 1912, 1930 and 1890 cm −1, respectively. The large wavenumber shift observed between the free monoanion and dianion (∼176 cm −1), in good accordance with the calculated one (170 cm −1) allows differentiating mono and dianionic species. The shifts observed for the 8a and 19a ν(CC) phenyl ring modes, although much smaller, also allows discriminating the different species. These small shifts indicate a small variation of the electronic delocalization in the benzene ring in agreement with the calculations.

Alkynethiolato and alkyneselenolato ruthenium half-sandwich complexes: synthesis, structures, and reactions with (eta(5)-C(5)H(5))(2)Zr.

Alkynethiolato and alkyneselenolato complexes of ruthenium, CpRu(PPh(3))(2)(EC(triple bond)CR) (Cp = eta(5)-C(5)H(5); E = S, R = Ph (1a), SiMe(3) (1b), (t)Bu (1c); E = Se, R = Ph (2a), SiMe(3) (2b)), were synthesized by the reactions of CpRuCl(PPh(3))(2) with corresponding lithium alkynechalcogenolates in THF. An analogous reaction of Cp*RuCl(PEt(3))(2) (Cp* = eta(5)-C(5)Me(5)) with LiSC(triple bond)CPh produced Cp*Ru(PEt(3))(2)(SC(triple bond)CPh) (3). Complexes 1a and 2a were allowed to react in THF with "Cp(2)Zr", generated in situ from Cp(2)ZrCl(2) and 2 equiv of n-BuLi, from which the S-bridged Ru-Zr dinuclear complexes CpRu(PPh(3))(C(triple bond)CPh)(mu-S)ZrCp(2) (4a) and CpRu(PPh(3))(C(triple bond)CPh)(mu-Se)ZrCp(2) (4b) were isolated, respectively. In these complexes, C-S(Se) bond cleavage of the alkynechalcogenolate ligands was promoted by "Cp(2)Zr", and the Zr atom was oxidized from II to IV. Treatment of 4a and 4b in THF under 1 atm CO gave rise to CpRu(CO)(C(triple bond)CPh)(mu-E)ZrCp(2) (E = S (5a), Se (5b)), while addition of tert-butyl isocyanide to a THF solution of 4b afforded CpRu(CN(t)()Bu)(C(triple bond)CPh)(mu-Se)ZrCp(2) (6). The crystal structures of 1a, 1c, 2a, 2b, 3, 4a, 4b, and 5b were determined by X-ray diffraction analysis.

Enantioselective synthesis of beta-Amino acids. 12. experimental and theoretical study of the diastereoselectivity of alkylation of the dianion of N',N'-Bis(alpha-phenylethyl)-N -carbobenzyloxypropionamide

Achiral, inexpensive beta-alanine was converted into the title chiral amide 1 in 53% overall yield. C-Alkylation of (R,R)-1 required formation of its dianion derivative, (R,R)-1-Li2, which was best achieved by direct metallation with two equivalents of n-BuLi in THF solution and at -78°C. Treatment of (R,R)-1-Li2 with various alkyl halides afforded the monoalkylated products 3-6 in 24-85% yield and 65-86% diastereoselectivity. The effect of LiCl additive or HMPA co-solvent on the diastereoselectivity of the alkylation reaction was essentially negligible, although reaction yields generally improved. Chemical correlation of the major diastereomer from the methylation reaction with (S)-alpha-methyl-beta-alanine shows that addition of the electrophile takes place preferentially on the enolate's Si face. This conclusion is also supported by molecular modelling studies (ab initio HF/3-21G), which indicate that the conformation of lowest energy for (R,R)-1-Li2 presents a more sterically hindered Re face of the enolate. The theoretical studies also provided useful insight into the importance of hydrogen bonding and attractive <FONT FACE=Symbol>p-p</FONT> interactions in (R,R)-1. Furthermore, the calculations predict a determining role for N-Li-O chelation in (R,R)-1-Li, as well as an interesting ion triplet configuration for dilithium dianion (R,R)-1-Li2.

Aromatization of Highly Alkyl-substituted Dihydroanthracenes Using n-BuLi/TMEDA/MeI

Abstract Aromatization of highly alkyl-substituted dihydroanthracene was performed with the n-BuLi/TMEDA/MeI. Treatment of 1,2,3,4,5,6,7,8-octapropyl-9,10-dihydroanthracene with 2.2 equiv of n-BuLi, TMEDA at 50 °C in hexane for 3 h, followed by 1.1 equiv of MeI at room temperature for 1 h gave the corresponding anthracene in 98% yield.

Alkoxylation and Amination of Ring-Methyl Group in Pentamethylcyclopentadienyliridium Complexes

Reactions of a unidentate bis(diphenylphosphino)methane (dppm) complex Cp*IrCl2(η1-dppm) (1) with 2 equiv of NaOR (R = Et, Me, or iPr) give ring-methyl-alkoxylated complexes (C5Me4CH2OR)Ir(η2-dppm) [R = Et (5a); R = Me (5b); R = iPr (5c)], respectively. Cationic complexes [Cp*IrCl(η2-dppm)]OTf (2), [Cp*IrCl{P(OPh)3}2]OTf (3), and [Cp*IrCl(PPh3)2]OTf (4) react with 2 equiv of NaOEt to give (C5Me4CH2OEt)IrL2 [L2 = dppm (5a); L = P(OPh)3 (6a); L = PPh3 (7a)], respectively. The complex 3 reacts with 2 equiv of NaOtBu in ethanol, methanol, 2-propanol, allyl alcohol, or propargyl alcohol to give (C5Me4CH2OR)Ir{P(OPh)3}2 [R = Et (6a); R = Me (6b); R = iPr (6c); R = allyl (6d); R = propargyl (6e)], respectively. Furthermore, treatment of 3 with 2 equiv of nBuLi and excess diethylamine, propylamine, N-methylaniline, or aniline in triethylamine as solvent gives ring-methyl aminated complexes (C5Me4CH2NR1R2)Ir{P(OPh)3}2 [R1 = R2 = Et (8a); R1 = nPr, R2 = H (8b); R1 = Ph, R2 = Me (8c); R1 = Ph, R2 = H (8d)], respectively. The structure of 8a has been confirmed by X-ray analysis.

Synthesis of the Bifunctional Phosphinidene Cluster, Fe3(CO)9(μ3-PH)2, and a Systematic Study of the Reactivity of the Cluster-Bound P−H Functional Group

The synthesis and systematic study of the reaction chemistry of a bifunctional phosphinidene cluster, Fe3(CO)9(μ3-PH)2 (3) is reported. Reaction chemistry at one P−H functional site is effectively communicated through the Fe3(CO)9 core, and impacts on the reactivity of the second P−H site. Deprotonation of the acidic protons in 3 allows access to a lone electron pair on phosphorus. The first proton is readily removed with NEt3/[PPN]Cl ([PPN]+ = (Ph3P)2N+) to produce the [PPN]+ salt of [Fe3(CO)9(μ3-PH)(μ3-P)]- ([4]-). Removal of both phosphorus-bound hydrogen atoms in 3 requires the use of 2 equiv of n-BuLi, to produce Li2[Fe3(CO)9(μ3-P)2] (Li2[5]). Quenching of Li2[5] with MeOH-d4 generates [Fe3(CO)9(μ3-PD)(μ3-P)]-. The lone electron pairs on the cluster-bound phosphorus atoms undergo analogous reaction chemistry to organophosphines. Alkylation at the phosphorus site is carried out by reaction of [Et3NH][4] with MeOSO2CF3 generating the monosubstituted cluster, Fe3(CO)9(μ3-PMe)(μ3-PH) (6) as the primary p...

Carbon versus Silicon Bridges. Synthesis of a New Versatile Ligand and Its Applications in Organolanthanide Chemistry

A new carbon-bridged versatile ligand Me2C(C9H7)(C2B10H11) (1) has been designed and successfully prepared by treatment of Li2C2B10H10 with 1 equiv of 6,6-dimethylbenzofulvene followed by hydrolysis with a saturated NH4Cl aqueous solution. 1 can be conveniently converted into the monoanion [Me2C(C9H6)(C2B10H11)]Li (2) and the dianion [Me2C(C9H6)(C2B10H10)]Li2 (3) by treatment with 1 or 2 equiv of n-BuLi, respectively. Both NaNH2 and NaH can only convert 1 into the monoanion, but cannot deprotonate the CH proton of the carborane cage in 1. These results differ significantly from those of a closely related analogue, Me2Si(C9H7)(C2B10H11). Treatment of SmI2 with 1 equiv of 3, followed by reaction with 1 equiv of 2, gave the redox product rac-[Li(DME)2][{η5:σ-Me2C(C9H6)(C2B10H10)}2Sm] (4). 4 can also be prepared by reaction of SmI2 with 1 equiv of 3 in a relatively lower yield. These two reactions may undergo different pathways, an intramolecular electron-transfer pathway for the former and an intermolecular electron-transfer pathway for the latter. The latter reaction can be accelerated by addition of CS2 or PhC⋮CPh, which led to the isolation of rac-[Li(THF)4][{η5:σ-Me2C(C9H6)(C2B10H10)}2Sm] (5). Unlike the SmI2 case, an equimolar reaction between 3 and YbI2 afforded the Yb(II) compound [η5:σ-Me2C(C9H6)(C2B10H10)]Yb(DME)2 (6). 6 can react with 1 equiv of 2 to generate a C−H bond reduction product, rac-[Li(DME)3][{η5:σ-Me2C(C9H6)(C2B10H10)}2Yb]·C6H5CH3 (7). Reaction of LnCl3 with 1 or 2 equiv of 2 yielded organolanthanide dichloride and monochloride compounds, respectively, [η5-Me2C(C9H6)(C2B10H11)]GdCl2(THF)2 (15) and [η5-Me2C(C9H6)(C2B10H11)]2LnCl(THF)(OEt2) (Ln = Y (8), Yb (9)). Treatment of 9 with 1 or 2 equiv of MeLi gave deprotonation products rac-[{η5:σ-Me2C(C9H6)(C2B10H10)}{η5-Me2C(C9H6)(C2B10H11)}]Yb(μ-Cl)Li(DME)2 (10) and rac-[Li(DME)2][{η5:σ-Me2C(C9H6)(C2B10H10)}2Yb] (11), respectively. Reaction of LnCl3 with 2 equiv of 3 also afforded ionic compounds rac-[Li(DME)2][{η5:σ-Me2C(C9H6)(C2B10H10)}2Ln] (Ln = Yb (11), Nd (12), Er (13)). Recrystallization of 7 from a mixed solvent of toluene/DME (10:1) gave meso-[Li(DME)3][{η5:σ-Me2C(C9H6)(C2B10H10)}2Yb]·2C6H5CH3 (14). All of these compounds were fully characterized by various spectroscopic and elemental analyses. The molecular structures of 4−7, 11, 12, and 14 have been confirmed by single-crystal X-ray analyses. The structural analyses reveal that the anions in 7 (or 11) and 14 are one pair of diastereomers.

Catalytic Dehydropolymerization of PhSiH3 to Polyphenylsilane with Substituted Group IV Metallocenes

Phenylsilane can be converted catalytically to polyphenylsilane using substituted achiral group IV metallocene dichloride precatalysts (CpR)2MCl2 (M = Ti, Zr; CpR = C5H4C(Me)2CH(Me)2) and Cp(CpR)MCl2 (M = Ti, Zr; Cp = C5H5) in combination with 2 equiv of n-BuLi. The performance of each precatalyst is described in terms of polymer molecular weight, polydispersity, and polymer microstructure. The polysilanes from each catalyst system were obtained as a mixture of oligocyclic and linear materials with Mw values ranging from 1100 to 4000. Characterization of the crude polymers by 1H and 29Si{1H} DEPT 135° NMR spectroscopy indicated a mostly atactic microstructure with a small syndiotactic bias. A Bernoullian statistical analysis of a typical 29Si{1H} polymer spectrum indicated a syndioselective probability (1-Pm) of 0.55 during propagation of the pseudochiral chain. The degree of polymerization was found to be dependent on the metal and the degree of Cp-ring substitution of the metallocene precatalyst.

Monocyclopentadienyl-Titanium Aryloxide Sulfide Complexes.

In this report we extend titanium-sulfide chemistry, describing the syntheses, structures, and chemistry of monocyclopentadienyl-titanium aryloxide sulfide complexes. Reduction of Cp'Ti(OC(6)H(3)-2,6-i-Pr(2))Cl(2) (Cp' = Cp (1), Cp (3)) with n-BuLi affords the Ti(III) compounds [CpTi(OC(6)H(3)-2,6-i-Pr(2))(&mgr;-Cl)](2) (2) and [CpTi(OC(6)H(3)-2,6-i-Pr(2))(&mgr;-Cl)](2) (4). Compound 2 is oxidized by moisture, giving [CpTi(OC(6)H(3)-2,6-i-Pr(2))Cl](2)(&mgr;-O) (5). Oxidation of 4 by sulfur led to a mixture of uncharacterized products; however, reaction of 3 with 2 equiv of n-BuLi followed by subsequent addition of sulfur afforded a new diamagnetic species, CpTi(OC(6)H(3)-2,6-i-Pr(2))S(5) (6). Oxidation of 2 by S(8) yields [CpTi(OC(6)H(3)-2,6-i-Pr(2))](2)(&mgr;-S)(&mgr;-S(2)) (7). Reaction of the known sulfide-bridged dimer [CpTi(OC(6)H(3)-2,6-i-Pr(2))(&mgr;-S)](2) (8) with sulfur provides an alternative route to 7. The conversion of 7 to 8 is reversible as reaction of 7 with PPh(3) yields SPPh(3) and 8 quantitatively. Reaction of 1 with Li(2)S proceeds cleanly to give 8. Reduction of CpTi(OC(6)H(3)-2,6-i-Pr(2))(SPh)Cl (9) with n-BuLi affords the diamagnetic product [CpTi(OC(6)H(3)-2,6-i-Pr(2))(&mgr;-SPh)](2) (10), which reacts with phenylpyridine to generate the paramagnetic species CpTi(OC(6)H(3)-2,6-i-Pr(2))(SPh)(NC(5)H(4)Ph) (11). Attempts to isolate a monosulfide-bridged complex are described. Isolation of a monosulfide-bridged species, [CpTi(OC(6)H(3)-2,6-i-Pr(2))(2)](2)(&mgr;-S) (14), is achieved via reaction of [CpTi(OC(6)H(3)-2,6-i-Pr(2))(2)Cl (13) with Li(2)S. Structural data for 2, 4-7, 10, and 14 are reported. Comparisons are made with the related titanocene-sulfide systems, and the implications are considered.

Crystal and molecular structure of [L 3( μ2-OAr) 3] (OAr = 2,6-diphenyl-3,5-di-tert-butylphenoxide); a cluster containing short LiO distances

Reaction of 2,6-diphenyl-3,5-di- tert-butylphenol (HOAr) with one equivalent of n-BuLi in toluene generates the hydrocarbon soluble cluster [Li 3(μ 2-OAr) 3] 1. The molecular structure of 1 consists of a six-membered ring (crystallographically imposed C 3 axis) of Li and O(aryloxide) atoms with alternating LiO distances of 1.78(a) and 1.840(7) Å.

Polynuclear Complexes with Propynylidene C3-Bridges: General Synthetic Route to Bis-, Tris-, and Tetrakis(ethynylcarbene) Complexes

The sequential reaction of two equivalents of the dimethylamino(ethynyl)carbene complexes [(CO)5M=C(NMe2)C≡CH] [M = W (1a), Cr (1b)] with two equivalents of nBuLi and one equivalent of a transition metal dichloride, [Cl2M′(Ln)], affords trinuclear biscarbene complexes of the type [(CO)5M=C(NMe2)C≡C−M′(Ln)−C≡CC(NMe)2=M(CO)5] [M′(Ln) = Ni(PEt3)2 (2a, b), Pd(PEt3)2 (3a, b), Pt(PEt3)2 (4a, b), Fe(dmpe)2 (6a), Hg (8a), Ti(η5-C5H5)2 (9a, b)] [dmpe = 1,2-bis(dimethylphosphino)ethane]. Treatment of 1a with equimolar amounts of first nBuLi and then [Cl2M′(Ln)] results in the formation of the monosubstitution products [(CO)5W=C(NMe2)C≡CM′(Ln)] [M′(Ln) = trans-Pd(PEt3)2Cl (5a), trans-Fe(dmpe)2Cl (7a)]. Additionally, the synthesis of the heterobimetallicethynylcarbene complex [(CO)5W=C(NMe2)C≡CPd(PEt3)2C≡CH] (10a), starting from 1a and [ClPd(PEt3)2C≡CH], is described. When three equivalents of 1a are treated, first with three equivalents of nBuLi and then with one equivalent of the trihalides PCl3 or BBr3, the novel tris(ethynylcarbene) complexes [{(CO)5W=C(NMe2)C≡C}3E] [E = B (11a), P (12a)] are obtained. The reaction of four equivalents of 1a,b with four equivalents of nBuLi, followed by addition of one equivalent of a group 14 tetrachloride [M′Cl4], yields the novel tetrakis(ethynylcarbene) complexes [{(CO)5M=C(NMe2)C≡C}4M′] [M′ = Si (13a, b), Ge (14a), Sn (15a, b)]. The complexes 8a, 9a, 12a, and 15a were characterized by X-ray structural analyses. All spectroscopic and structural data suggest that the carbene fragments and the central transition metal or heteroatom in these new bis-, tris-, and tetrakis(ethynylcarbene) complexes interact only weakly.

Polynuclear Complexes with Propynylidene C3-Bridges: General Synthetic Route to Bis-, Tris-, and Tetrakis(ethynylcarbene) Complexes

The sequential reaction of two equivalents of the dimethylamino(ethynyl)carbene complexes [(CO)5M=C(NMe2)C≡CH] [M = W (1a), Cr (1b)] with two equivalents of nBuLi and one equivalent of a transition metal dichloride, [Cl2M′(Ln)], affords trinuclear biscarbene complexes of the type [(CO)5M=C(NMe2)C≡C−M′(Ln)−C≡CC(NMe)2=M(CO)5] [M′(Ln) = Ni(PEt3)2 (2a, b), Pd(PEt3)2 (3a, b), Pt(PEt3)2 (4a, b), Fe(dmpe)2 (6a), Hg (8a), Ti(η5-C5H5)2 (9a, b)] [dmpe = 1,2-bis(dimethylphosphino)ethane]. Treatment of 1a with equimolar amounts of first nBuLi and then [Cl2M′(Ln)] results in the formation of the monosubstitution products [(CO)5W=C(NMe2)C≡CM′(Ln)] [M′(Ln) = trans-Pd(PEt3)2Cl (5a), trans-Fe(dmpe)2Cl (7a)]. Additionally, the synthesis of the heterobimetallicethynylcarbene complex [(CO)5W=C(NMe2)C≡CPd(PEt3)2C≡CH] (10a), starting from 1a and [ClPd(PEt3)2C≡CH], is described. When three equivalents of 1a are treated, first with three equivalents of nBuLi and then with one equivalent of the trihalides PCl3 or BBr3, the novel tris(ethynylcarbene) complexes [{(CO)5W=C(NMe2)C≡C}3E] [E = B (11a), P (12a)] are obtained. The reaction of four equivalents of 1a,b with four equivalents of nBuLi, followed by addition of one equivalent of a group 14 tetrachloride [M′Cl4], yields the novel tetrakis(ethynylcarbene) complexes [{(CO)5M=C(NMe2)C≡C}4M′] [M′ = Si (13a, b), Ge (14a), Sn (15a, b)]. The complexes 8a, 9a, 12a, and 15a were characterized by X-ray structural analyses. All spectroscopic and structural data suggest that the carbene fragments and the central transition metal or heteroatom in these new bis-, tris-, and tetrakis(ethynylcarbene) complexes interact only weakly.

Preparation and structures of [formula omitted] and [formula omitted], containing the novel anions [formula omitted] and [formula omitted

The reaction of tert-butyl carbodiimide with one equivalent of LiNH tBu in tetrahydrofuran at −78 °C produces {Li[C(N tBu) 2(HN tBu)]} 2·(THF) ( 1), which is an eight-membered Li 2C 2N 4 ring; the deprotonation of 1 with two equivalents of n-BuLi in tetrahydrofuran at −78 °C and recrystallization of the product from n-pentane yielded the unsolvated dimer {Li 2[C(N tBu) 3]} 2 ( 2), which has a distorted cyclic ladder structure.