7921
resemble those of the reduced anions, MozC193- and W2clg3-,and we assume that the oxidized anions retain the bioctahedral structure. A complete description of the magnetic and spectroscopic properties is planned for a subsequent publication. The M O ~ C I anion ~ ~ - seems to react with most donor solvents, precluding conductivity measurements. As an example, the anion is instantly reduced by C H X N to Mo2CIg3-. Rapid, quantitative reduction to Mo2CIg3- also occurs with tin metal and excess alkylammonium halide in CHZClZ. MoC16'- + Mo(C0)hCla- +Mo2Clg3- + 4CO (1) We believe that this work represents the only synMoClj + C1- +MoClsthesis of polynuclear halometalates which purports to (2) MoCls- + M o ( C O ) ~ C I ~+ M02C1g2- + 4CO have a rational basis. However, the success of the method does not prove the proposed mechanism alBoth reactions were conducted at the millimolar though it would seem to be the simplest explanation of level in CHzClzcontained in glass vessels connected to the results. Moreover, we do not claim that the rea vacuum line. Procedures have been previously deaction scheme is universally useful at present since a scribed.4 Reaction l proceeded with the liberation of similar (but not identical) reaction which was designed 87% of the available CO after 30 hr and the formation to yield W2Clg3-,uiz., WC16 W(CO)jCl2C1- + of orange [ ( H - C ~ H ~ ) ~ N ] ~ M(50 O ~%Cyield) I, in addition W2CIg 3-, gave instead Wc16'and W(CO),CIZ and/or to some Mo(CO)6 and an unknown carbonyl species. W(CO),C13-. It would appear that these products Complete evolution of CO occurred in reaction 2 after either from an outer sphere mechanism or an 24 hr and the yield of dark greenish brown [ ( H - C ~ H ~ ) ~ N ]resulted ~inner sphere mechanism followed by decomposition of Mo2CIg was virtually quantitative. Satisfactory elea bridged intermediate. mental analyses were obtained in both cases. The two compounds are also easily distinguished by their Acknowledgment. Financial aid from the National electronic absorption spectra and their magnetic Science Foundation (Grant No. GP-30544X) is grateproperties (Table I). The temperature dependence fully acknowledged. Since the average oxidation state of the product is dependent solely upon the oxidation state of the metal in MClsn-, this scheme indicatesthat it should be possible to prepare not only M2CIg3-from MC162- but also MzC192from MCls-. (The WZClg2- anion was previously obtained from the oxidation of WzClg3-with molecular halogens.zc) Indeed, we are now able to report the successful syntheses of MozC193- and the new anion, Mo2C19*--, according to this strategy and the following reactions
}
+
W. H. Delphin, R. A. D. \Ventworth* Cotitribution No. 2324 Department of Chemistry, bidiatia Uuioersity Bloomirigtori,Indiana 47401 Receired September 15, 1973
Table I. The Electronic Spectra and Magnetic Properties of the M o 2 C l ~ ~and - M02C192- Anions Compound
Y , cm-l ~
[ ( N ~ ~ H ~ ) ~ N I ~ M O-1Z C 3,200 ~ ~ (23). 14,920 (33) 18,950 (638) 23,300 (608) [ ( ~ z - C ~ H ~ ~ N I ~ M O Z10,250 C ~ ~ (163) 12,800 (171) 15,280 (265)
1 .29 (302") 0 . 8 4 (204") Diamagnetic (86") 2 . 0 6 (300") 1 . 8 7 (236") 1 . 6 5 (140") 1 . 6 1 (95")
*
Molar extinction coefficients appear in parentheses. Absolute temperatures appear in parentheses. c Some fine structure was noted. a
of the magnetic moment of Mo2CIg3- is in general accord with a thermal equilibrium between the manifold of antiferromagnetic spin states, S = 3, 2, 1, and 0, with S = 1 and 0 having only appreciable populations at room temperature. The magnetic moment at that temperature is considerably larger than the value of 0.6 BM found3b for CssMozC19, but a dependence on the nature of the cation has been previously noted.3d The magnetic moment of Mo2CIg2- is constant at about 1.6 BM at temperatures below IOO'K, indicating a ground state having one unpaired electron with g < 2. As the temperature is increased, the increased magnetic moment is attributed to the thermal population of a manifold of the antiferromagnetic spin with only the last two having states, S = ;Iz,3/e, and appreciable populations at room temperature. The infrared spectrum of MozCIg2- between 200 and 400 cm-1 resembles that of WzC1g2-. Both of these spectra (4) W. H.Delphin and R. A. D. Wentworth, Inorg. Chem., 12, 1914 (1973).
+
Preferential Mode for Nucleophilic Attack by Methoxide Ion on 0,s-Dimethyl Phenylphosphonothiolate. A Contrasting Behavior to Reactions on Analogous Phosphonium Salts
Sir: Recently, the mode for nucleophilic attack by hydroxide ion on menthoxy(methy1thio)methylphenylphosphonium hexachloroantimonate (1) has been shown1m2 to be exclusively axial on phosphorus in the face opposite the alkoxy ligand to form intermediate A (eq 1). Eventual loss of the methylthio group only
1
M~
M~
OMen
.. I
'P-SMe
/ I
Ph OH A
isom
+
-HShIe
OMen
.. /
___f
(1)
Ph
after an isomerization results in formation of the product with retention of configuration at phosphorus. In apparent contrast, the neutral ester analog of 1, 0-menthyl S-methyl phenylphosphonothiolate (2), suf(1) N. J. De'ath, I
