COMMUNICATIONS TO THE EDITOR
Oct. 5 , 1964
gen exchange occurred a t random between any of the deuterium atoms of chlorophyll and water, i t must have been confined t o less than 5% of the hydrogen atoms a t any location. Hydrogen exchange confined to only a few special chlorophyll molecules (constituting less than 57c of the chlorophyll) in a large photosynthetic unitg probably would not be revealed b y our procedure. In these organisms and under the conditions employed in our experiments, then, the bulk of the chlorophyll exists in a form t h a t precludes hydrogen exchange especially a t the 6 , 7, and 8 positions, either by photosynthesis or b y subsequent hydrogen transport. (9) I?. K . C l a y t o n in "Photophysiology," A. C . Giese, E d , Academic Press N e w York, N Y , 1964, p 159 e l seg. CHEMfSTRY
DIVISION
XRCONNESATIONAL LABORATORY ARGONSE, ILLISOIS
4221
The product I11 was insoluble in most aliphatic and aromatic hydrocarbons and only very slightly soluble in anhydrous tetrahydrofuran or N-methylpyrrolidine. Traces of moisture rapidly cleaved I11 to regenerate I. Ultraviolet spectra of I11 in the latter two solvents displayed only end absorption in the region >325 mp.
C6H5 I1
c%
JOSEPH J . KATZ RALPHC. DOUCHERTY WALTERA. SVEC HAROLD H. STRAIN
RECEIVED JULY 9, 1964
Novel Six-M embered Aluminum-Nitrogen Heterocycles via Metalative Cyclization
Although the foregoing reaction product I11 is clearly a highly associated substance ( x > 1)) i t was desirable to demonstrate that benzene evolution had arisen from metalative cyclization leading to the 9methyl-lO-phenyl-l0,9-aluminazarophenanthrene monomer (111), and not from metalation ortho or para to the methylamino group ((2-3or C-5 in IT). Therefore, 111 was treated successively with a benzene solution of iodine and with water to yield, as oils, iodobenzene and ca. 80% of an iodo-2-(methylamino)biphenyl ( IV)6 (picrate,6 m.p. 178-180' ; p-toluenesulfonamide,6 m.p. 153-154'). Proof t h a t IV is 2'-iodo-2-(methylamino)biphenyl was obtained by heating IV with copper bronze in dimethylformamide to produce N-methylcarbazole (m.p. 87-88' ; mixture melting point undepressed). Consequently, the structure proof of the molecular unit in 111 can be summarized in the following manner.
Sir : Current interest in novel heterocycles isoelectronic with aromatic hydrocarbons has inspired the synthesis of many unsaturated organoboron ring systems. T h e physical and chemical properties of borazines' and borepins2 have been studied with particular attention since 7r-bonding involving boron might be expected to confer aromatic character upon such heterocyclic nuclei. Dewar's comprehensive studies of boron-nitrogen analogs of aromatic nuclei, such as IO,!+borazarophenanthrene, have adduced convincing evidence for such cyclic conjugation. Our recent discovery of a novel metalative cyclization pathway to the hitherto unknown aluminole ring system4 awakened the hope t h a t aluminum-nitrogen heterocycles, such as the 10,9aluminazarophenanthrene system,3 might result from suitably conceived intramolecular metalations. Since the problem of Ir-bonding between aluminum and adjacent electron-rich centers is still uncertain,j the study of such heterocycles might prove significant in evaluating possible 7r-electronic interactions. In light of the foregoing, we are pleased to describe the synthesis and properties of the novel, six-membered, aluminum-nitrogen heterocycle formally isoelectronic (cf. infra) with the phenanthrene nucleus. Thus, the heating of an equimolar melt of 2-(methylamino)biphenyl (I)6and triphenylaluminum a t 160' led t o the evolution of 1 equiv. of benzene; further heating a t 240' produced ca. 1 more equiv. of benzene (total T h e properties of 9-methyl-10-phenyl-10,S-alumibenzene (2 equiv.) : $E-10070). T h e resulting pale amber-colored 9-methyl-lO-phenyl-10,9-aluminazaro- nazarophenanthrene (111) form a sharp contrast to those of the corresponding boron ~ y s t e m . ~ 9-Methyl-10phenanthrene (111) did not melt under 500' ; however, phenyl-l0,9-borazarophenanthrene (V) is reported to decomposition commenced a t temperatures over 350'. be monomeric (m.p. 123'), soluble without decomposi( 1 ) Cf.,inler alra, M . J . S. D e w a r , el al., J . C h e m . Soc., 3073. 3076 ( 1 9 5 8 ) . tion in 95% ethanol, and quite stable to hydrolytic ibid., 2728 (1959). J . A m . C h e m . S o c . , 84,2648 ( 1 9 6 2 ) . ( 2 ) E.: E v a n T a m e l e n . G Brieger, a n d K . G. U n t c h , TplvahPiiron I . e t k r s , cleavage. Moreover, it exhibits a prominent ultraNo.8, 14 (1Y60). violet maximum a t 332 mp, ascribable to boron( 3 ) Chemical Abslracls f a v o r s t h e naming of six-membered boron-nitrogen heterocycles a s azaborines a n d t h i s pseudophenanthrene member a s 5,6nitrogen conjugation. T h e latter contention is supdihydr7 4 6 I 4
Y 01
Aside from the elemental analyses obtained, each carborane described in the table exhibited the parent peaks in its mass spectrum which coincided with the assigned empirical formulas containing a random distribution of 1°B and * l B isotopes in their natural abundance. The infrared spectrum of the parent B9C2Hllcontained a B-H stretching band a t 3.88 p and a C-H stretching band a t 3.27 p. Slthough the l l B n.1n.r. spectra of ByC2Hll and its alkyl and aryl derivatives have not been unequivocally interpreted. the spectra (8) A. W. L a u h e n g a y e r , K . W a d e , a n d G. Lengnick, Inoug. Ckem., 1, obtained a t 60 Mc., set.' are consistent with an eleven632 (1962). (9) C/ J . I. Jones a n d U'. S. M c D o n a l d , Proc. Chein. S O L .366 , (1962). particle icosahedral fragment related to BYC2H12 - ,fi BllH11-,8 and BllH132-.8 Degradation of the C-phenyl DEPARTMENT OF CHEMISTRY J O H N J . EISCH THECATHOLIC UNIVERSITY O F AMERICA and C,C'-dimethyl derivatives with a palladium cataWASHINGTON, D. C. 20017 S R . MARYESTHER HEALY, lyst and propionic acid a t the reflux temperature was P.\..B.M. quite vigorous and afforded toluene (77; yield) and RECEIVED AUGUST24, 1964 ethane (67y0 yield), respectively. The similar degradation of the C-phenyl derivative of o-BloCaHlz produced only ethylbenzene (21%; yield). Thus, the A New Carborane, BgC2Hll,and Its Derivatives chemical evidence available suggests that the carbon Sir : atoms in B9C2Hll are not near neighbors arid that In recent months a great deal of interest has decarborane formation is accompanied by rearrangement veloped with regard to the carboranes o - ,m-,2 ~ and p - j of the carbon atoms.g B1&2H12, B ~ C ~ HB&H*,j T,~ B4C2Hfi,4hsC and B ~ C Z H ~ . ~ ' Additional evidence suggests that the gross strucWe have recently prepared a new carborane. BYCZHl1, tural features present in BgC2Hl2-are retained in BYCaand representative C-alkyl, C-aryl, and C,C'-dialkyl H1l. Treatment of the ByC2Hllcarboranes described derivatives. These carboranes were obtained in modabove with a variety of ligands produced monoadducts erate to high yields by pyrolysis of the corresponding of the general formula ByCzHll(ligand)which are isoB9C2HI3derivativesfia t 110-150° in a suitable organic electronic with B9CzHla-. Representative ligands insolvent. The BgC2H13intermediates were generated in clude triphenylphosphine (m.p. for the C-phenyl derivasitu by treating the cesium or potassium salts of the tive, 255' dec. .4nal. Calcd. for ByC2bHaoP: C , proper B9C2H12-ion6 with polyphosphoric acid in the 66.32; H , 6.42; B. 20.68. Found: C, 65.7s; H . presence of solvent. At temperatures above 100°, 6.79; B, 22.62) and triethylamine (m.p. for the Chydrogen is briskly evolved and the resulting carborane phenyl derivative, 157-159" dec. dlna/.Calcd. for is separated by distillation in vacuo. Table I presents BgCI4H3"N: C. 54.28; H , 9.77; B, 31.14. Found: representative yield and characterization data. The C, 52.57; H , 9.69; B, 32.24). Titration of B G H l o BgCzHll carboranes survive brief exposure to moist (CsH,) with methoxide ion in methanol was typical air. for a strong acid and 1 equiv. of base was consumed ( I ) ( a ) C. C . C l a r k , U . S. P a t e n t 3,062,756 (SOP. 6, 1 9 6 2 ) ; ( h ) T . 1,. (equiv. wt., 206.8 ; theory, 208.6). H e y i n g , J , W . Ager, J r . , S. L C l a r k , D J Mangold, H L Goldstein, .M. Further studies are in progress and will be reported H i l l m a n , R J . P o l a k , a n d J . W. S z y m a n s k i , I > i o i g . Ckein , 2 , 1089 ( 1 9 6 3 ) , at a later date. (c) H Schroeder, T I,. Heying, a n d J . I < , Reiner, i b i d , 2 , 1092 ( 1 9 6 3 ) ; ( d ) T I-. H e y i n g , J W Ager, J r . , S. I,. C l a r k , I
