323 Journal of Organometallic Chemistry, 304 (1986) 323-329 Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands ANALYSIS OF TEN NOVEL RHENIUM COMPLEXES BY DESORPTION CHEMICAL IONIZATION MASS SPECTROMETRY * W.A. KORFMACHER*, J.P. FREEM A N , R.K. MITCHUM ** Department of Health and Human Services, Food and Drug Administration, National Center for Toxicological Research, Jefferson, Arkansas 72079 (U.S. A.) N.T. ALLISON, W. YONGSKULROTE, and R. FEREDE Department of Chemistry and Biochemistry University of Arkansas at Fayetteville, Fayetteville, Arkansas 72701 (U.S.A.) (Received June 14th 1985; in revised form November 14th, 1985) Summary The desorption chemical ionization (DCI) mass spectrometry of ten rhenium compounds is compared to the desorption electron impact (DEI) mass spectrometry of the same compounds. Using 10% ammonia in nitrogen as the reagent gas, the DC1 mass spectrometric (MS) technique provided [M + H]+ ions for each rhenium compound. In most cases, the DEIMS method provided only fragment ions. Introduction While electron impact (EI) mass spectrometry (MS) has proven to be a useful method for the study of organometallic compounds [l-4], conventional EIMS techniques often fail to provide molecular weight information [l]. Field desorption (FD) MS has more recently been shown to be a valuable technique for providing molecular weight information for organometallic complexes [1,5,6]. Indeed, FDMS analysis of rhenium complexes has been reported [5]. Following the introduction of fast atom bombardment (FA B) ionization, mass spectrometry has become a major analytical tool for the study of organometallic compounds [6-91. Because many mass spectrometric laboratories do not have FAB or FD capability, the ability to analyze thermally sensitive organometallic compounds by conventional mass spectrometry is still of considerable interest. Therefore, we have investigated the combined use of the * Presented in part at the 1985 Pittsburgh Conference, New Orleans, LA, February 1985. ** Current address is: Quality Assurance Division, U.S.E.P.A., P.O. Box 15027, Las Vegas, Nevada (U.S.A.). 0022-328X/86/$03.50 Q 1986 Elsevier Sequoia S.A.