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B. RICE, R. J. GALIANO AND W. J. LEHMANN
development process. I n recent papers,ls they have discussed the effect of ionic charge on the adsorption process and have concluded cooperative adsorption processes may be important. This paper clearly shows that adsorption and desorption processes must be very important in the photographic development process. It also indicates that the zeta potential in most photographic emulsions must be considerably less than - 60 millivolts for it is indeed doubtful that the bromide ion completely displaces gelatin and sensitizing dyes (16) T. H. James and W. Vanselow, J. A m . Chem. Soc., 74, 2374 (1952); THIS JOURNAL, 67, 725 (1955); 68, 894 (1954).
Vol. 61
from the emulsion under normal processing conditions. The observation that the zeta potential a t the gelatin sheath-solvent interface increases with pAg because of (we believe) the adsorption of potassium ion also complicates the discussion of the effect of charge on the development process. This paper indicates that an investigation of the adsorption processes and their role in the development mechanism should be undertaken. Obviously the net zeta potential must be a function of the relative strength of adsorption of dye, gelatin, bromide ion, and other species present in the emulsion and the processing solution.
VIBRATIONAL SPECTRA AND FORCE CONSTANTS OF TRIMETHYLAMINE-BORANE AND TRIMETHYLAMINE-BORANE-& BYBERNARD RICE,ROBERTJ. GALIANO AND WALTER J. LEHMANN Department of Chemistry, St. Louis University, St. Louis, Mo. Received May 37, 1067
The Ranian and infrared spectra of trimethylamine-borane and trimethylamine-borane-& were measured and the fundamental frequencies of both molecules assigned. A force constant calculation was made based on a n!e3NBHk (eight part$:) model with the most important interartion terms included in the potential function. The trends in certain characteristic frequencies of some ether and amine-boranes were correlated with the electronic charge distributions and the stabilities of the complexes.
Introduction The interest in the field of addition compounds formed by Group I11 Lewis acidswith Groups IV, V and VI Lewis bases centers at present on the relative stabilities of these complexes. To a first approximation, the relative stabilities can be predicted from a consideration of (1) the position of the electron donor and acceptor atoms in the periodic system and (2) inductive, steric and resonance effects. Other aspects of modern valence theory have recently been invoked to account for the exceptions to the order predicted from the Above factors.' Vibrational spectroscopy can play an important role in this field. From a comparison of the vibrational spectrum of the complex with the spectra of the parent acid and base, detailed information can be obtained on the structural changes that accompany the formation of the addition compound. Furthermore, the force constant of the donoracceptor bond should be related to the stability of the complex. Unfortunately, because of the complicated nature of the molecules or the incompleteness of the spectra, the force constant calculations in most of the reported work are based on molecular models and potential functions too simple for such a relationship to be investigated. I n the present work we have obtained the Raman and infrared spectra and made an assignment of all the observed vibrational frequencies of trimethylamine-borane, (CHs)3NBH3, and its isotopjc analog trimethylamine-borane-&, (CH3)3NBDs. Our normal coordinate treatment, based on an MesNBHs model, enabled a more complete calculation of force constants than is common in (1) W. A. G. Graham and F. G . A. Stone, J . Inorg. NucE. Chsm., 8 , 164 (1958); D. L-I Mclhniel, Science, 126, 545 (1957).
this field. Furthermore, with the frequencies of the isotopic derivative available, the most important interaction terms could be retained in the valence force potential function. Experimental Apparatus.-The infrared spectra were obtained with a Perkin-Elmer Model 21 spectrometer by Dr. William Elliott of the Biochemistry Department, St. Louis University. The Raman apparatus has been previously described in the literature.2 Chemicals.-Diborane (obtained from the Rev. F. J. Koenig of the Chemistry Department) was purified by fractionation. Trimethylamine was dried and purified by reaction with lithium aluminum hydride.8 Diborane-dd was prepared by successive exchange of BzHa with deuterium gas. Other reagents were dried and purified by standard means before use. Two methods were used for the preparation of trimethylamineborane as a check against possible spurious lines in the spectra due to decomposition products. Direct combination of diborane and trimethylamine was first used. Later the compound was prepared by the reaction of trimethylammonium chloride with lithium borohydride in ether slurry.4 Spectra obtained on both preparations agreed in every detail. Trimethylamine-borane-& was prepared by direct addition of the amine and BzDeonly. Measurements .-The Raman and infrared measurements were made on solutions of the addition complexes. The spectrum of the pure complex was determined by subtracting the solvent spectrum. The Raman spectrum of trimethylamine-borane was obtained from solutions in three different solvents-tetrahydrofuran, carbon tetrachloride and diethyl ether. Since this complex is most soluble in tetrahydrofuran, the spectrum obtained from this solution was the most complete. However, four additional lines, obscured by tetrahydrofuran solvent lines, were discovered by the meaRurements on a carbon tetrachloride solution. The measure, ments on the diethyl ether solutions led to no further lines. (2) B. Rice and H. S. Uohida, THIS JOURNAL, 69, 650 (1956). (3) J. Roscoe, Ph.D. Thesis, St. Louis University, 1954. (4) G. W. Schaeffer and E. R. Anderson, J . Am. Chem. Soc. 71, 2145 (1949).
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SPECTRA OF TRIMETHYLAMINE-BORANE
Sept., 1957
The Raman spectrum of trimethylamine-borane-& was obtained from measurements on tetrahydrofuran and carbon tetrachloride solutions. The infrared work was done with tetrahvdrofuran solutions only, and covers the range 7502500
