Dec. 5 , 1964
COMMUNICATIONS TO
initial [11],yields decreased with decreasing initial [11] at 0.01 -If 11. to a value of The initial-rate method was employed and reactions were followed to approximately 3y0completion. A series of rate determinations carried out at constant I1 concentration and varying I11 concentrations proved this reaction to be first order in 111. ,4 plot of pseudofirst-order rate constant vs. initial I1 concentration indicated t h a t the reaction became essentially zero order in I1 a t high 11 concentrations. T h e addition of dimethyl sulfide ( I P ) depressed the reaction rate a t all concentrations of I1 and 111. Three series of kinetic runs were carried out a t different [IV], in which [11] was varied within each series and [111]was held constant. Plots of [III]/(d[BloHlo-2]/dt)vs. [IIIp1for each [IV] were linear and gave a common intercept of 2.1 X l o p 4 sec. a t [III-’ = 0. The slopes (2) of each of these plots were plotted vs. [IV] present in each series of rate runs and a straight line described by the equation, z = 3.45 X 104[Me2S] 140 sec. mole 1.-’ was obtained. The intercept of the latter line was identical with the slope obtained in the first series of plots with no added IV. This intercept requires the operation of a process ( k 4 ) which removes the BlaHlz(1igand) intermediate from the system without producing BloHlo-2 or regenerating 111. The results obtained with I and I11 are consistent with the following rationale6 in which the kl process
+
__ k -1
BloH12(ligand)~
THE
EDITOR
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Acknowledgment.-The authors wish to thank the Advanced Research Projects Agency through the Army Research Office (Durham) for generous support of this work. DEPARTMEKT OF CHEMISTRY M FREDERICK HAV’THORSE’ THEUXIVERSITY OF CALIFORNIA RICHARD L PILLING RIVERSIDE, CALIFORNIA RUSSELL S GRIMES RECEIVED SEPTEMBER 30, 1964
A Crystalline Alkoxydiarylalkylidenephosphorane from the Reaction of Ethyl Diphenylphosphinite with an a-@-Unsaturated Ketone’ Sir : Harvey and Jensen? ascribed the cyclic dialkoxydzarylalkylphosphorane structure3 I to the adduct, “m.p. 116-118°,” which is formed from ethyl diphenylphosphinite and trans-dibenzoylethylene in an ether solution.4 IVe should like to report t h a t this substance is actually the alkoxydiarylalkylzdenephosphorane3 11, a moderately stable phosphinitemethylene.
+ ligand
B1,H12(ligand)
ki
ka
BloHls(ligand) f SEt;
+ H 5 E t ; + ligand BioHio-2 + H G E t i
--+BloH11-
very fast
+ XEt; ka BloH12(ligand) + KEt; --+
BlaH11-
BloH12(SMe2)(XEtr)
kr
BlnHlz(1igand) +unidentified products
may become rate determining a t high I1 concentrations. It seems probable t h a t the kz process involves proton abstraction by I1 with or without the concerted ejection of the second ligand molecule. The proposed BloH1?(ligand)intermediate formally resembles BI0Hl3-. T h a t the BloH12(SMe2)(V) reported by Knoth and Muettertie? is not the intermediate involved in BloHlo-2 formation was shown by the fact t h a t authentic V formed BloHlo-2 more than 103 times slower than I11 under the same conditions. As suggested by Lipscomb,8 two reasonable structures exist for B10H13- and two tautomeric BloHlz(ligand) structures may well exist. The formation of BloHlo-2 from V may involve the slow conversion of V to the reactive isomer. Conversely, the k4 process may involve the moderately rapid conversion of the reactive intermediate to V. Further work is in progress and will be reported a t a later date. 16) Where L = ligand and d[BieHnL]ldt = 0 , d[BioHio-2]/dl = ki. [ B I O H I Z I ~ ~ ~ {‘((fir ~ ? [ E ~ka)[EtaSl ~SI k-~[Ll k r ) ) or /BlaHi!L!l/ k,)’klkr} (kr ka)/kiki. I n the (d[B~oHlo-’l dl) = ( l I [ E t a S I ) ( k - i [ L l first series of plots, t h e slopes ( k - i[L1 k r ) / k i k r sec. mole IV-1, and t h e intercepts = (kz kS),’klkl sec. I n t h e second plot, t h e slope k- I ’kiki sec.. and the intercept - ks k:kr sec mole I.-’. Elimination of the kikz term 2 b s ) ‘k- 1 = 0.44 =k 0.02 and (rate of kr process)/(rate of k- I process) - ; [ L ] ) = 2.5 + 0 5 x l o - P / [ L l . (7) W . H . K n o t h and E. I, Muetterties, J . i n o r g . S u c l . C h e m . , 2 0 , 66 (1961). (8) W. S Lipscomb, A d s a n . I n o r g . C h e m . Radiochem , 1, 117 (1959) ($1) Alfred P. Sloan Research Fellow-.
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11,m.p. 123 O, bp 31 = -54.2 p.p.m.
Equimolar amounts of ethyl diphenylphosphinitej and trans-dibenzoylethylene were allowed to react a t 20’ in anhydrous 1,2-dimethoxyethane (ca. 1.6 M). The infrared spectrum of the resulting clear, red solution after 3 hr. showed t h a t the reaction was nearly complete. The 1 : l adduct crystallized and was filtered after 2 days; yield, 427,; m . p . llS-120° (crude). Recrystallization from benzene-hexane gave 11, m.p. 122-123’. Spectral characteristics are: infrared bands, (CHXC12, F ) : 3.97 (strong C=O) and 6.63 (broad and strong “enolate” C=06); APll = -54.2 p.p.m.’ (CH2ClJ; H1 n.m.r. (CDC13; p.p.m. in the 7-scale): multiplet a t 2.65 (aromatic), 2H1 (1) This investigation was supported by t h e National Science Foundation ( G 19509) and by Public Health Service Research Grant No. CA-04769-05 from t h e National Cancer Institute. ( 2 ) R . G. Harvey and E. V Jensen, Tetrahedron Letters, No. 26, 1801 (1963). (3) Structure I : 2 - e t h o x y - 2 , 2 - d i p h e n y l - 3 - h e n z o y l - 5 - p h e n y l - ~ ~ - ~ ~ a p h o s . pholene, structure 11: ethoxyldiphenyl- (benzoyl-, phenacyl-) methylenephosphorane. (4) For other reactions of a - p u n s a t u r a t e d carbonyl compounds with trivalent phosphorus compounds: (a) V . A. Kukhtin and K . M Orekhova. J . G e n . C h e m . C S S R . , SO, 1539 (19601, (b) G. Kamai and 4 . V , Kukhtin. ;bid., 31, 1621 (1961), and earlier papers; (c) V . A . Ginshurg and .4 Ya Yakuhovich, J . Gen. C h e m . C S S R . 3 0 , 3944 (1960), ( d ) E. I
