April 5, 1955
COMMUNICATIONS TO THE EDITOR
2029
cis to the hydrogens a t C-15 and C-20. I n addi-
Raman spectra of Na(NH&I were obtained by standard methods.s The absence of characteristic NH3 deformation frequencies and the observation of a new set of frequencies indicates that this compound has a distinct set of bond properties. The NH3 deformation frequencies a t 950 and 1627 cm.-' have shifted in Na(NH3)41to 1105 and 1525 cm.-' and are surprisingly close to the corresponding CH3 deformation frequencies of tetramethyl compounds which occur near 1148 and 1448 cm.-' in Pb(CH3)4. In the Raman spectrum the NaNHs skeletal stretching and deformation frequencies are readily assigned to 435 and 103 cm.-' bands. These frequencies are close to the corresponding frequencies of Zn(NH3)4++and Pb(CHJ4 indicating the existence of rather strong Na-NH3 bond^.^.^ The calculated value of the Na-NH3 stretching force constant compares favorably with those calculated for Zn(NH3)4++ and Pb(CH3)4: ( k N a ( N H , + + ) , VI VI1 = 1.9 X 106 dynes/cm., k Z n ( N H , + + ) , = 1.85 X lo6 We have no conclusive evidence a t present con- dynes/cm. and kpb(CH8), = 1.87 X lo5 dynes/cm.). An assignment3 of frequencies may be made on cerning the stereochemistry of the C-17 methoxyl group although, assuming a trans elimination in the basis of a Na(NH3)4+ ion and in a manner the formation of methyl anhydroreserpate, the 17- analogous to that for Pb(CH3)4, if one assumes that in the Raman spectrum the close doublets have not methoxyl would appear to be cis oriented. It now seems possible to assign absolute con- been resolved and that the weakest bands present figurations t o the above mentioned asymmetric in Pb(CH3)4 have not been observed in Na(NH3)4+. centers since Klyne has shown6 that Hudson's The NH3 rocking frequency which is not present in lactone rule may also be applied to molecular the infrared spectrum of ammonia and observed rotations of polycyclic compounds. The change a t 765 cm.-' in Pb(CH3)4 appears near 500 cm.-' in molecular rotation from reserpic acid, [MID in Na(NH3)4+. The distribution of the NH fre-692' (pyridine) to reserpic acid lactone, [MID quencies in Zn(NH3)4++ and Na(NH3)4+ ions is +300° (pyridine), is +992", therefore the hydroxyl nearly the same. The Raman lines observed for the Na(NH3)4+ a t C-18 is related to D-glyceraldehyde and the absolute configuration of reserpine should be repre- ion were much broader than the corresponding lines observed for Zn(NH3)4++ and Cd(NHa)p++ sented by structure VI and not VII. ions,4 and the presence of other ionic species such as (6) W. Klyne, Chemistry Q n d I n d u s f r y ,1198 (1954). Na(NH3)a+ and Na(NH3)2+ cannot be completely THESQUIBBINSTITUTE FOR PATRICK A. DIASSI MEDICAL RESEARCH FRANKL. WEISENBORN eliminated. The observation of a distinct ultraviolet spectrum NEWBRUNSWICK, NEWJERSEY CHRISTIANE M. DYLION OSKARWINTERSTEINERalong with the evidence for a distinct set of bond RECEIVED MARCH10, 1955 properties from the vibrational spectrum indicates that the stability of this compound is due to the presence of charge transfer forces involving resoTHE TETRAMMINESODIUM ION nance best illustrated in terms of no-bondand bonded Sir: + Compounds of alkali halides and ammonia have structures such as [Na-NHs] and [Na-NH3].6 been known for some time'J but little information However the presence of broad bands in the Raman has been available as to the nature of the bonding spectrum and the observation of a low NH, rocking involved or of their structures. We wish to frequency suggests that ion-dipole forces are more present a preliminary report of studies made on important in Na(NH3)4+ than in ammonia comliquid tetramminesodium iodide, Na(NH3)41, which plexes of the transition metals. verify the existence of a tetramminesodium ion, DEPARTMENT OF CHEMISTRY GUYWILLIAMLEONARD, JR.~ Na(NH3)4+,of remarkable stability. KANSASSTATECOLLEGE ELLISR. LIPPINCOTT4 KANSAS RICHARD D . NELSON The sample was prepared by reaction of an- MANHATTAN, DOUGLAS E. SELLERS hydrous ammonia with anhydrous NaI and was a RECEIVED FEBRUARY 18, 1955 thermally stable liquid a t 25' with a melting point of 3' and P N H ~= 420 mm. a t 25'. The ultraviolet (3) E. R. Lippincott and M. C. Tobin, THISJ O U R N A L , 75, 4141 spectrum has X m i n . 309 and A,,,. 330 and isd istinct (1953). (4) J. L.Silver, Ph.D. Thesis, University of Connecticut, 1953. from both NaI and ammonia. Infrared and (5) R. S. Mulliken, THISJOURNAL, 64, 811 (1952); J. P h y s . Chcm., tion, the carbomethoxy group a t C-16 is cis to the C-18 function since reserpic acid readily forms a y-lactone without inversion. Thus the known stereochemical relationships of reserpine can be expressed by structure VI.
(1) W. Biltz and W. Hansen, 2. anorg. oilgem. Chem., 127, 1-33 (1922). (2) M . Picon, Compl. rend., 168, 825 (1919).
16,801 (1952). (6) Supported in part by a grant from the Kansas State College Faculty Research Fund.
