2,131 research outputs found
Synthesis of coordinatively unsaturated diolefin complexes of tungsten(II)
No full text[WBr2(CO)4] reacts with cycloocta-1,5-diene, cyclooctatetraene, and norbornadiene (LL) to give complexes [WBr2(CO)LL]2 (I) which react with Lewis bases (L') [L' = CNCMe3, PMe2Ph, (POMe)3] to give coordinatively unsatd. diene complexes [WBr2CO(LL)L] (II) and coordinatively satd. derivs. [WBr2(CO)(LL)L'2] (LL = norbornadiene) and [WBr2(CO)2L'3]. Two isomeric forms of II exist which have been sepd. in the case of [WBr2(CO)(NBD)(PMe2Ph)] (NBD = norbornadiene)
Coordinatively unsaturated diene complexes of tungsten(II) and their reactions with nucleophiles to give six- and seven-coordinate derivatives
No full text[WBr2(CO)4]2 reacts with dienes L1 [cycloocta-1,5-diene (L2), cyclooctatetraene (L3), norbornadiene (L4)] to give coordinatively unsatd. WBr2(CO)2L1 (I). I react with Lewis bases L [CNCMe3, PMe2Ph, P(OMe)3] in 1:1 molar ratio to give coordinatively unsatd. WBr2(CO)LL1 via intermediate adducts WBr2(CO)2LL1, isolated for L1 = L4. With a 3:1 molar ratio of ligand to metal, displacement of L2 or L3 occurs to give WBr2(CO)2L3 (II), whereas a 4:1 molar ratio (L = CNCMe3) gives WBr2(CO)L4. In contrast, I (L1 = L4) forms WBr2(CO)L2L4 [L = P(OMe)3, PMe2Ph; L2 = 2,2'-bipyridyl]. 1H and 31P NMR studies of II [L = P(OMe)3, PMe2Ph] reveal the presence of 2 isomers which exhibit dynamic stereochem. at ambient temp.; the static form of 1 isomer was detected at lower temps
Synthesis and nuclear magnetic resonance studies of coordinatively unsaturated alkyne complexes of tungsten(II)
No full text[WBr2(CO)4]2 reacts with RC≡CR1 (R = R1 = Me, Et, Ph; R = Me, R1 = Ph) to give [WBr2(CO)(RC≡CR1)2]2. These react with nucleophiles (L) to give WBr2(CO)L2(RC≡CR1) [L = CNCMe3, P(OMe)3, PPh3; R = R1 = Me, Ph; R = Me, R1 = Ph], which exist as cis and/or trans isomers and which exhibit alkyne propeller rotation, according to 1H and 31P NMR studies. The isolation of WBr2(CO)(CNCMe3)(MeC≡CMe)2 indicates that the reactions proceed via monomeric bis(alkyne) intermediates
Coordinatively unsaturated alkyne complexes: synthesis of mono and bisalkyne complexes of tungsten(II)
No full text[WBr2(CO)4]n reacts with alkynes to give complexes [WBr2CO(RC≡CR)2]2 (I, R = R' = Me, Et, Ph; R = Me, R' = Ph), which react with nucleophiles L [L = CNCMe3, PPh3, or P(OMe)3] to give monoalkyne derivs. [WBr2(CO)(RC≡CR')L2]. An intermediate bis-alkyne adduct [WBr2CO(MeC≡CMe)2(CNCMe3)] was isolated in the reaction of [WBr2(CO)(MeC≡CMe)2]2 with CNCMe3 illustrating that cleavage of the dimer I is the first stage in these reactions
Coordinatively unsaturated alkyne complexes of tungsten: synthesis and dynamic nuclear magnetic resonance studies of some but-2-yne derivatives
No full textReaction of [{W(μ-Br)Br(CO)(MeC≡CMe)2}2] (I) with one molar equiv of Na(S2CNMe2), Na(S2PMe2), or Tl(acac) (acac = acetylacetonate) gives mononuclear derivs. [WBr(L2)(CO)(MeC≡CMe)2] (L2 = S2CNMe2, S2PMe2, acac). The 1H and 13C NMR spectra of the acac complex are temp. independent whereas dynamic 1H NMR studies of the S2CNMe2 and S2PMe2 derivs. have been interpreted in terms of a mol. rearrangement involving dechelation of the bidentate ligand which exchanges the alkyne environments and the ends of the dithiolate ligand. The reaction of I with two molar equiv of Na(S2PMe2) gives the bis-alkyne complex [W(S2PMe2)2(MeC≡CMe)2] (II) whereas Na[S2P(OMe)2] and Tl(acac) give mono-alkyne derivs. [W(L2)2(CO)(MeC≡CMe)] [III; L2 = S2P(OMe)2 or acac]. 1H NMR studies of II suggest fluxional behavior involving dechelation of S2PMe2 which exchanges both the S2PMe2 methyls and the alkyne methyls without necessarily requiring alkyne propeller rotation. In contrast, fluxional behavior in III [L2 = S2P(OMe)2] clearly involves alkyne propeller rotation in addn. to two other processes, one of which exchanges the Me groups of one S2P(OMe)2 group. However, the only dynamic process obsd. with III (L2 = acac) appears to involve alkyne propeller rotation
Letter from Jesse L. Boyce to Jack
No full textLetter from Jesse L. Boyce to Jack in which he refers to W. W. Crosby as a "damn carpetbagger" and his frustration at Crosby making him out to be a "liar"
Alkene metathesis catalyzed by [WBr2(CO)2(diene)]/AlCl2Et
No full text[WBr2(CO)2(diene)]/AlCl2Et mixts. promote metathesis of cis-2-pentene to give 2-butene and 3-hexene. For diene = norbornadiene, the reaction is catalytic, and is accompanied by cis to trans isomerization of the 2-pentene, whereas for diene = 1,5-cyclooctadiene or cyclooctatetraene, the metathesis is essentially stoichiometric. The same complexes catalyze the metathesis of trans-2-pentene to give 2-butene and 3-hexene, but at approx. twice the rate obsd. for the cis-alkene. [WBr2(CO)2(diene)]/AlCl2Et mixts. also catalyze the metathesis of 1,7-octadiene to give cyclohexene and ethene. The intermediacy of metal carbene derivs. in such reactions is supported by the reactions of [WBr2(CO)2(norbornadiene)] with alkylating agents SiMe4 and MeMgBr which give methane, whereas [WBr2(CO)2(norbornadiene)] and AlCl2Et in the absence of alkenes gave virtually stoichiometric amts. of ethane
Stabilization of vinylic intermediates in the addition, cyclization, and oligomerization reactions of alkynes by coordination of molybdenum and tungsten. The crystal and molecular structure of [W(SC6H4Me-p)[η2-C(CF3)C(CF3)PEt3] (η2-CF3C≡CCF3)(η-C5H5)] and [WCl[η2-C(CF3)C(CF3)CN](η2-CF3C≡CCF3)(η-C5H5)]
No full textNucleophilic attack of phosphines, phosphites or Me3CNC on the η2-CF3C≡CCF3 (L) complexes L2WBr2(CO) and L2MX(Cp) (Cp = η5-cyclopentadienyl; M = Mo, W, X = Cl, SC6F5; M = W, X = SC6H4Me-p) occurs at an acetylenic C atom to give 1:1 adducts. The products, I [X = SC6H4Me-p, L1 = PEt3 (II); X = Cl, L1 = Me3CNC (III)] were shown by x-ray diffraction to contain a metal-stabilized 1-3 dipolar vinyl ligand L+C(CF3)C-(CF3) η2-coordinated to the W center. The structures of II and III were refined to R 0.038, 0.040, for 2924, 6900 independent reflections, resp
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Letter from Jes Boyce to Jack
No full textLetter from Jesse L. Boyce to Jack regarding the storage of dynamite in Shoski Canyon
- …
