NH3+-group of the intercalated a-alanine complex undergoes less intermolecular and environmental in- teractions in clays during its stretching modes than in crystals.

In the lower region of the infrared spectra, the band ~1600 cm -1 and the medium band at 1424 cm -1 observed for Cu-clay-a-alanine complexes prepared at pH values less than 6 can be assigned to the asym- metric and symmetric CO stretching modes of free carboxylate groups. ~,~° However, a band due to the NH2 bending mode also occurs at ~1600 cm-L For the Cu-clay complex prepared at a pH 6.6, two bands are noted at 1391 and 1373 cm -1 along with a shoulder at 1630 cm-L Increasing the preparat ion pH to 8.2 for the complex caused the lat ter peak to intensify at 1633 cm -~. Also, the bands at 1391 and 1373 cm -~ remain in the spectrum while the other bands in this region disappear. The bands at 1633 and 1391 cm -~ are assigned to the asymmetric and symmetric stretch- ing modes of carboxyl groups coordinated to Cu 2+ ions. Consistent with the assignments made by Segnini et al. 6 for the chelated complex in crystals, a weak band at 1595 cm -~ may be assigned to the NH2 scis- sorting mode. Also, band assignments are made for the other observed bands in Table I using Segnini's interpretat ion. The spectral features of the H-mont- morillonite-o~-alanine complex in the 1800-1600 cm -~ region are very similar to those observed for the cationic form of a-alanine in crystals. 4,5 Their band assignments are listed in Table I.

Analysis of the experimental da ta leads to the following interpreta t ion: Cu-clay complexes with a- alanine prepared at a pH .~ 6.0 contain two different adsorbed species, the monodenta te complex (A) and the bidendate complex (B) :

/ C u \ CH~ J

H~O OH2 J (A)

-H~O NH2-CH-CH3" + \ /

Cu / \

H20 O--C %

O (B)

The monodentate complex is the predominant species when the preparation pH is less than 6, and the bidendate complex is the main species present when the preparation pH is greater than 6. A small amount of the alanine cation CH3CH(NH3+)COOH, also is noted when the preparation pH value is less than 3. The major species adsorbed on H-montmorillonite is the ~-alaninium cation. The possible presence of NH3 + groups which possess a degenerate deformation mode at ~ 1610 cm -~ may explain why the band that we assigned to the CO0- asymmetric stretching mode

has shifted to a higher wavenumber for the sample prepared at the lower pH.

Rober t A. Condrate, St., would like to thank the College Center of the Finger Lakes for a grant-in-aid supporting this study.

1. M. L. Hair, Infrared Spectroscopy in Surface Chemistry (Marcel Dekkcr, New York, 1967), p. 191.

2. L. H. Little, Infrared Spectra of Absorbed Species (Academic, New York, 1966).

3. P. Cloos, J. J. Fripiat, B. Calicis and K. Makay, Proc. Int. Clay Conf. (Israel) 1,223 (1966).

4. K. Fukushima, T. Onishi, and T. Shimanouchi, Spectro- chim. Acta 15, 236 (1959).

5. J. F. Jackovitz, J. A. Durkin, and J. L. Walter, Spectrochim. Acta 28A, 67 (1967).

6. D. Segnini, C. Curran, and J. V. QuagHano, Spectrochim. Acta 16, 540 (1960).

7. S. D. Jang, Ph.D. thesis, State University of New York at Al~fred University, Alfred, New York, 1971.

8. M. M. Mortland, J. J. Fripiat, J. Chaussidon, and J. Uytter- hoeven, J. Phys. Chem. 67, 248 (1963).

9. M. M. Mortland, Clay Minerals 6, 143, (1966). 10. K. Nakamoto, Y. Morimoto, and A. E. Martell, J. Amer.

Chem. Soc. 83, 4528, (1961).

E x c h a n g e React ions in the Ion Source of a

M a s s S p e c t r o m e t e r *

Roger S. Cichorz

Mass Spectrometry Laboratory, The Dow Chemical Company, Rocky Flats Division, Golden, Colorado 80401

(Received I June 1971; revision received 25 June 1971)

INDEX HEADINGS : Mass spectroscopy--general; Exchange reactions; Uranium compounds.

Exchange reactions occurred in the ion source of a mass spectrometer during direct solid probe analyses of samples of te t ra(cyclopentadienyl)uranium(IV) [UCp4, where Cp=CsHs , the cyclopentadieny llig- and]. Tr is(cyclopentadienyl)uranium(IV) fluoride, UCp3F, was formed according to the reaction UCp4 + M F - - * U C p 3 F + M C p . This mass spectrometer ex- change phenomenon is the first reported for an actinide organometallic compound, al though mass spectrom- eter ion-source exchange reactions between lanthanide chelates and alkali metal chelates have been observed previously. '

This exchange reaction enabled the author to obtain the mass spectrum of tr is(cyclopentadienyl)- uranium(IV) fluoride. This compound was reported initially by Ammon and co-workers2; however, no preparat ion or synthesis was given, and, to date, no

* Work pedormed under U. S. Atomic Energy Commission Contract AT (29-1)-1106.

104 Volume 26, Number 1, 1972

Table I. Mass spectrum of tris(cyclopentadienyl)uranium(IY) fluoride at varying source temperatures.

Relative abundances m/e Fragment b (190°C) (200°C) (210°C) (290°C)

453 i 6.98 5.88 5.95 9.45 452 UCp3F + 43.0 33.5 31.0 57.4 388 i 12.8 12.4 11.9 10.9 387 UCp~F + 100. 100. 100. 100. 323 i 3.49 3.62 4.37 2.36 322 UCpF + 51.2 59.0 52.8 35.3 296 U(C3H~)F + 5.81 7.23 4.37 3.29 257 UF + 6.98 7.92 5.95 8.21 % total ionization of 43.4 43.6 46.2 44.1

m/e 387~

a Percent to ta l ion current contribution by UCP2F +, the most abundant ion in the spectrum of UCpsF.

b i represents the isotopic contributions of 2H and 13C,

mass spectrometry data on UCp~F have appeared in the literature.

Samples of UCp4 in glass capillaries were introduced into a CEC 21-110B mass spectrometer via a solids insertion probe. The samples sublimed over a tem- perature range of 190 ° to 290°C and a source pressure range of 10-7-10 -6 Torr. UCp4 samples were pre- pared by reacting uranium(IV) chloride with cyclo- pentadienyl sodium in te t rahydrofuran and vacuum drying the resultant precipitate.

The exchange originated in the mass spectrometer, since nuclear magnetic resonance analyses indicated the samples were UCp4, and not UCp4-UCp3F mix- tures. The observed exchange phenomenon occurred

several days after perfluorotriheptyltriazine, a mass marker, was introduced into the mass spectrometer. The fluorine species involved in the exchange reactions probably are compounds chemisorbed on the interior walls of the mass spectrometer. The chemisorbed nature of these fluorine species is suggested by the lack of volatile fluorine-containing materials detected in blank runs over a temperature range of 50°-350°C.

In the author 's initial investigations, the absence of UCp,F+(n=I-3) fragments in the mass spectra of UCp3C1 samples indicated the exchange UCp3C1 + M F - - ~ UCp3F+MC1 did not occur. However, in more recent scans of UCp3CI samples, taken only one day after introduction of another mass marker, perfluoroeyclooctyl ether, into the mass spectrometer, the above reaction did occur2 Again, blank runs over a wide temperature range were void of any volatile fluorine-containing species.

The major ion in the mass fragmentat ion pat tern of UCp3F is UCp2F +, not the molecular ion UCp3F +. This trend also is apparent in the mass spectra of UCp4 and UCp3C1, where the most abundant ions are UCp3 + and UCp2C1 +, respectively. As anticipated, the mass spectrum of UCp3F at 10 -G Torr is slightly dependent on the temperature of vacuum sublimation (see Table I).

1. J. R. Majer and R. Perry, J. Chem. Soc. D, Chem. Commun. 9, 454 (1969).

2. R. v. Ammon et al., Inorg. Nucl. Chem. Lett. 5, 315 (1969). 3. K. J. Grossaint, The Dow Chemical Company, Rocky Flats

Division (private communication, April, 1971).

Arc Spectral Lines of Selenium and Tel lurium

J. W. Mellichamp and G. C. Vezzoli

Institute for Exploratory Research, U. S. Army Electronics Command,

Fort Monmouth, New Jersey 07703

(Received 4 June 1971; revision received 26 July 1971)

INDEX HEADINGS: Spectral lines of Se and Te; Arc excita- tions ; Wavelength tables.

Several factors limit the detection of selenium by excitation in the dc arc. One, the most persistent lines (1960.9, 2039.9, and 2062.8 A) are in the spectral region that requires a photographic emulsion sensitive to short-wave radiation. Also, plane-grating spectro- graphs in common use have gratings blazed for maxi- mum speed around 3000 A to take advantage of the sensitive lines of elements in that region, thus lines at shorter wavelengths, below 2500 A, are greatly at- tenuated. Arc lines of tellurium are more plentiful and favorably located than those of Se, however, the two most persistent lines (2383.3 and 2385.8 A) are

weakened by the blaze angle. In prior analysis of Se 1 and Te by the dc arc it was noted that spectral lines occur that can be utilized for the detection of these elements in various materials by conventional dc-arc excitation. In the present study, differences found are compared with published tables? -6

Table I gives the apparatus and excitation condi-

Table I. Apparatus and exposure conditions for excitation of selenium and tellurium.

Spectrograph :

Excitation source :

Excitation : Analytical gap : Electrodes :

Filter: Sample weights : Exposure time : Photographic emulsion :

Apparatus Bausch & Lomb dual grating, one

grating 4 ~ mm in first order, other 4 X mm in second order, both blazed for maximum speed around 3300

Jarrell-Ash Varisource

Exposure Conditions

10 A de arc, constant current 5 mm Anode-Ultra Carbon 101-L Cathode--Ultra Carbon 1509 Neutral split filter at entrance slit 1, 10, 100, and 200 mg Total consumption of sample Eastman SA III

APPLIED SPECTROSCOPY 105