the reaction mixture was brought to atmospheric pressure and the yellow solution was evaporated to a yellow oil. Recrystallization from THF/ toluene at -10 °C provided 0.3981 g (88%) of yellow crystalline 13: 'H NMR (THF-rfg) 7.55 (m, 35 H, PNP, Ph), 2.98, 2.80 (AB, 3/Hcch = 4.3 Hz, 1 , 1 H, HOC, HOC); IR (THF) r(CO) 2039 (w), 1895 (vs), 1864 (m), i-C(O) 1558 (w) cm"1.Acknowledgment. The financial support of this research by the National Science Foundation (Grant CHE 83-08281) is greatly appreciated. G. G. was the recipient of a DAAD/NATO Scholarship for which we are most grateful.

at 90 MHz were satisfactory. In all cases p-dimethoxybenzene was the internal standard. The quartets at 1.942 and 2.317 due to the H4 protons were used for 7a and 8a respectively. Doublets at 1.150 and at 1.087 due to the 5-CH3 group were used for 7b and 8b respectively. Quartets at 2.330 and at 1.966 (H4 protons) and singlets at 2.188 and 2.100 (CH3CO-) were used for 10, 9,11, and 8c, respectively. The multiplet at 5.49-5.10 (H; and H3) and the triplet at 2.56 (H4 protons) were used for 7d and 8d, respectively.Rate of Reaction of CAN with Carbonyl Compounds. The rate of disappearance of CAN in solutions containing the various carbonyl compounds were determined by iodometric analysis in the absence and in the presence of 1,3-butadiene. With acetone, the half-life time of CAN was 5 h in the presence and 17 h in the absence of 1,3-butadiene. Corresponding values for 2-butanone were 0.75 and 2.3 h. With ethyl acetoacetate the disappearance of CAN was almost instantaneous in the presence of 1,3-butadiene, whereas in the absence of diene only 58% of CAN was reduced after 30 min. With 3-methyl-2-butanone reduction of CAN was complete after 8 and 24 h, in the presence and in the absence of 1,3-butadiene, respectively.Acknowledgment. Thanks are due to the Italian National Council of Research (CNR) and the Ministero della Pubblica Istruzione for financial support.Registry No. 7a, 100431-93-4; 7b (isomer 1), 100431-95-6; 7b (isomer 2),

6736 J. A m . Chem. Soc.is electron-precise (1 2 electrons) while [Mo4S4(edta), I3-and [ M o~S~( N C S ) ,~]~-are species7J0 with 1 1-electron counts and [Mo4S4(Et2NCS2),] has 10 electrons.12 The 12-electron species has essentially Td symmetry, while [Mo&(edta),13-has Mo-Mo distances ranging from 2.755 to 2.880&1° and the 10-electron species has distances to 2.732 ( 5 ) (2X) and 2.861 (16) A (4X).We wish to report the preparation of the M o~S~~+ (~~) ion and a compound derived therefrom, (NH4)6[Mo4S4(NCS)12]~10H20, which are important in the context of the facts just summarized for two reasons. They are 10-electron species not constrained by any bridging ligands and the method of preparation differs from all those used previously to make Mo~S, containing compounds. In our recent report6 of the preparation of the M o~S~~+ (~~) ion by refluxing a mixture of Mo(CO)~ and Na,S in acetic anhydride, followed by aqueous workup employing a cation exchange resin, we noted that in addition to the dark green Mo3S;+(aq) ion there was a second, paler green ion (denoted 11) that adhered more firmly to the resin. From the eluate containing this second green ion we have been able to crystallize the compound (NH4)6-[ M o~S~( N C S ) ,~] .~O H~O and determine its s t r u~t u r e . '~ The structure of the tetranuclear anion is shown in Figure 1.The [Mo,S,(NCS),,]~-ion resides on a crystallographic site of 3m (C3J symmetry. Instead of the Td symmetry potentially possible for this cuboidal species, it has only C3u symmetry, as can be seen clearly in the Mo-Mo distances. The Mod unit is a triangular pyramid, with slant edges of length 2.791 (1) %, and basal edges of length 2.869 (1) A. Each face of the pyramid is capped by a sulfur atom and each molybdenum atom has three N-bonded thiocyanate ions attached to it.The green solution eluted from the cation exchange column with 2 M HC1 is believed to contain the Mo4S,6+(aq) ion, whose absorption spectrum is shown in Figure 2, along with the spectra of the Mo3S?+(aq) and [ M o , S~( N C S ) ,~]~-ions.The pronounced distortion of the M o~ cluster in the [MOqS4-(NCS),,Ib ion from Td to C3, symmetry requires an explanation. It seems unlikely to us that this is due to intermolecular (packing) forces. A molecular orbital calculation (Fenske-Hall method20) shows that the HOMO of a [ M o~S~( N C S ) ,~] * -ion (12e-) would be a fully occupied t2 orbital. For a C3c distortion of the type observed in the [ M O~S~( N C S ) ,~]~ ion (1Oe-), the t2 orbital is split into a lower, filled e orbital and an upper, empty a2 orbital. These results support (but do not prove) our view that the 10e-system undergoes a Jahn-Teller distortion along one coordinate of a T2 vibration, thus splitting the degeneracy of the t2 orbitals.21During our preparation we observed a most interesting chemical interconversion of the Mo,S, and the Mo4S4 cores. While the Mo3S4 species have previously been described as incomplete cubes, the topological similarity of the two species does not a priori necessitate a chemically tractab...

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A number of a-substituted hydroperoxides are discussed the decomposition of these substances under capable of olefin epoxidation ; unusual cis-trans selecacidic, basic, and pyrolytic conditions6 none has dwelt on

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Die Darstellung der Säurechloride (IIIb), (IIId) und (IIIt) wird angegeben.