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X-Ray diffraction studies have shown that molybdenum(r1) chloride derivatives contain the octachlorohexamolybdenum(11) group, (Mo,C1,)4+, which acts as a centre for octahedral complexes analogously to a single-atom ion.', Preparative work, cryoscopy, molecular conductivity, ultraviolet spectroscopy, and magnetic susceptibility support the octahedral co-ordination of this group. The existence of [(Mo6C18)XJ-(X = C1, Br, I, or OH) ions in solution have been demonstrated. These complexes are starting materials in the preparation of compounds (Mo,Cl,) X, which are considered to be polymeric. Evidence is given for the existence of octahedral complexes [(Mo,C18)C1,,2C,H,N], [(Mo6CI,)C1,,2NEt3], [(Mo,C1,) (OH),,2H20], and [(Mo,C1,)C13*OH,2H,0]. The stability, ultraviolet spectra, and diamagnetism of Mo,Cl, compounds, and the co-ordination number nine for each molybdenum atom,l* can be explained by regarding molybdenum as sexivalent in chloromolybdenum(I1).

Organosilicon compounds are playing an increasingly important role in synthetic organic chemistry, and the chemistry of their anions is the subject of a great deal of current interest.1 Organosilicon anion chemistry is potentially even richer than that of carbanion chemistry since silyl anions, -silyl carbanions, pentacoordinate silicon anions, and hexacoordinate silicon anions are useful synthetic reagents. In addition, pentacoordinate silicon anions play key roles as reaction intermediates Charles H. DePuy was born In Detroit, MI, and received his undergraduate education at Berkeley. His Ph.D. (1953), under the direction of William Doering, was begun at Columbia University and completed at Yale. After a year's postdoctoral work with Donald Cram at UCLA, he joined the faculty of Iowa State University and in 1963 moved to his present position at Colorado. After many years of studying organic reaction mechanisms In solution, he "entered the gas phase", and his present research is entirely devoted to this area of chemistry.Robert Damrauer was born In Toledo, OH, and received his undergraduate degree at the University of Michigan. Working under Dietmar Seyferth's tutelage, he received his Ph.D. at the Massachusetts Institute of Technology. After a year of postdoctoral work at Harvard with P. D. Bartlett, he joined the faculty at the University of Colorado at Denver, where he remains ensconced.John H. Bowie has the following degrees: M.Sc. (Melbourne, 1961), Ph.D. (Nottingham, 1964), D.Sc. (Adelaide, 1969. After an I.C.I. postdoctoral position at Cambridge (U.K.), he moved to the University of Adelaide (South Australia) where he is currently Professor of Organic Chemistry. His current research interests Include negative and positive Ion mass spectrometry and the study of ion-molecule reactions using Ion cyclotron resonance. John C. Sheldon received his B. Sc. and Ph.D. (1956) degrees from the University of Nottingham. After a Fulbright Award taken at the University of North Carolina, Chapel Hill, and an I.C.I. Fellowship at University College, London, he moved to the University of Adelaide where he Is currently Senior Lecturer in Physical and Inorganic Chemistry. His current interests lie In the application of computational chemistry to organic and organometalllc reactions.

Ab initio calculations indicate that the collisional induced losses of molecular hydrogen from the ethoxide negative ion and methane from the t- butoxide negative ion to be stepwise processes in which the key intermediates are [H-… MeCHO ] and [Me-…Me2CO] respectively. Deuterium kinetic isotope effects observed for these and other alkoxide negative ions are in accord with the operation of a stepwise reaction.

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