Organometal-Substituted Phosphines having a Cage-Like Structure[**]

By H. Schumunn and H . Bendu [ * I

Di- and trifunctional organometal halides react with phos- phine, alkali-metal phosphides, or alkali-metal organophos- phides to give not only polymeric but also oligomeric organo- metallophosphines having a cage-like structure. Thus we recently reported on the synthesis of cho-tetrakis(pheny1- stannylphosphine) [ X J .

If a benzene solution of phenyltrichlorosilane or phenyltri- chlorogermane and a suspension of dipotassium phenyl- phosphide in monoglyme/ether are simultaneously added under argon to a 2 : 1 mixture of diethyl ether,'monogIyme, a cu. 60 % yield of colorless doso-tetrakis(phenylsily1)hexa- kis(pheny1phosphine) ( I ) or pale-yellow rho-tetrakis- (phenylgermyl)hexakis(phenylphosphine) (2) is obtained alongside potassiumIchloride and small amounts of insoluble polymers.

R

( I ) , It = C6H5, M = Si (2). I? = C,H5, M = Ge

The crystals of ( I ) and (2) are soluble in benzene, sensitive to oxygen, and decompose, without melting, above 125°C with blistering; their homogeneity was established by thin- layer chromatography [21. Complete elemental analyses, the cryoscopically determined molecular weight, and the IR spectra [ ( I ) : vSi-P at 406, 348, and 326 cm-1; (2): vGe-P at 390, 334, and 309cm-11 confirm the adamantane-type structure, which has also been found for the corresponding organosilyl[31, organogermyl[41, and organostannyl[51 sul- fides. By contrast, the reaction of butyl- or phenyl-trichloro- stannane with phenylphosphine in the presence of triethyl- amine affords a cu. 25 % yield of benzene-soluble closo-bis- (butylstannyl)tris(phenylphosphine) (3) or cbso-bis(pheny1- stannyl)tris(phenylphosphine) ( 4 ) , together with polymeric products.

P

The colorless compounds (3) and (4) are sensitive to air and melt at 89-91 OC (decomp.) and 133-135 "C, respectively. The trigonal-bipyramidal structure is in accord with the cryoscopically determined molecular weights, the results of elemental analyses, the 31P-NMR spectra[61 [(3) shows a singlet at +5.2 ppm], as well as the I R spectraC71 [vSn-P at 375, 328, 305 ((3)), and 362, 320, 296 cm-1 ( (4 ) ) ] .

Procedure:

(1 ) and (2): Phenyltrichlorosilane (4.2 g, 0.02 mole) or phenyltrichlorogermane (5.1 g, 0.02 mole) is dissolved in

benzene; one third of the solution is transferred, together with ether (60 ml) and monoglyme (30 ml), to a three-necked flask that has been flushed out with dry argon. The remaining two thirds of the solution is then added dropwise and simul- taneously with a suspension of dipotassium phenylphosphide (0.03 mole) in monoglyme (50 ml), over a period of 4h with stirring. After six hours' stirring, half of the solvent is remov- ed under reduced pressure, the solution is filtered, and the filtrate is concentrated until it becomes oily. Repeated ex- traction with petroleum ether and methylcyclohexane, dissolu- tion in benzene, and fractional precipitation with pentane/ methylcyclohexane affords almost pure crystals, which can be recrystallized from toluene/methylcyclohexane.

(3) and (4 ) : Solutions of butyltrichlorostannane (5.7 g, 0.02 mole) or phenyltrichlorostannane (6.0 g, 0.02 mole), phenylphosphine (3.3 g, 0.03 mole), and triethylamine (6.1 g, 0.06 mole) in benzene are simultaneously added dropwise at the same rate to benzene (150 ml) under dry argon. The re- sulting precipitate is removed after six hours' stirring. On frac- tional precipitation with pentane/methylcycloliexane, the clear concentrated benzene solution yields a product that proves pure on thin-layer chromatography.

Receiyed: October 15, 1969 [Z 113 IEI German version: Angew. Chem. 81, 1049 (1969)

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[*I Doz. Dr. H. Schumann and Dr. H. Benda Institut fur Anorganische Chernie der Universitat 87 Wurzburg, Rontgenring 11 (Germany)

[**I This work was supported by the Deutsche Forschungsge- meinschaft and the Fonds der Chernischen Industrie. We are grateful to Dr. G. Engelhardt, Berlin-Adlershof, for recording the 31P-NMR spectra. [l] H . Schumann and H. Bendu, Angew. Chem. 80, 846 (1968); Angew. Chem. internat. Edit. 7, 813 (1968). [2] MN-Polygram Cel 300/UV 254, Macherey-Nagel and Co.; methylcyclohexane/dioxane as mobile phase. [3] J. A. Forsfner and E . L. Muetterties, Inorg. Chem. 5, 552 (1 966). [4] K. Moedritzer, Inorg. Chem. 6, 1248 (1967). [51 M . Komura and R . Okawaru, Inorg. nuclear Chem. Letters 2, 93 (1966); C. Dorfelt, A . Juneck, D . Kobelt, E . F. Puulus, and H. Scherer, J. organometallic Chem. 14, P 22 (1968). [6] 10% solution in benzene, 85;" H3P04 as external reference. [ 7 ] Nujol mull, capillary.

Rotational Isomerism of N2-Met hyl-N2-phenylthiof ormohydrazide 11 1

By W . Wulter and H. Weiss"*l

A number of Nz,N2-dialkylthioformohydrazides exhibit be- taine-thioacyl tautomerism 12931. In the case of N2,Nz-diethyl- thioformohydrazide it was assumed 131 that an additional rotational isomerism (E-Z isomerism) occurs in solutions of thioacyl tautomers, as is generally observed in thioamides [I]. We report here on N2-methyLN2-phenylthioforrnohydrazide ( I ) , which does not form a betaine and permits direct ob- servation of the rotational isomerism. The compound crys- tallizes in two forms having different melting points and ex- hibiting different IR- and UV spectra.

In carbon tetrachloride an equilibrium is rapidly set up be- tween ( l a ) and (Ib) [about 10% ( l a ) : 90% ( I b ) ] . Never- theless, the bands could be assigned to the two isomers by comparison with those of the rotational isomers of thio- amides [41.

Since rapid isomerization occurs in solution the signals of both forms, i.e. of ( I u ) and ( l b ) , appears in the 1H-NMR spectrum. In CDC13 the formyl proton of the E form ( I b ) couples with the N-H proton to give an AB system. The coupling constant is of the same order of magnitude as in N2,N2-diethylthioformohydrazide [31 and in thioamides [51,

Angew. Chem. internat. Edit. 1 Vol. 8 (1969) / N o . I 2 989

and thus confirms the assignment given. A coupling with the formyl proton of ( l a ) was not observed. Deuteration elimin- ated the coupling in ( Ib) . The ratio of isomers is also about 9 : 1 under NMR conditions. The lower value of the NH stretching vibration of (Ib) in KBr indicates the presence of a cyclic dimer, which can be formed from ( I b ) but not from ( l a ) ~ 5 1 .

IT H H N \ /

J-N\ S H

M.p. IR (KBr) (v-NH)

UV (CHCI,) imaX Emax

In CCI, i 10-3 M (v-NH)

IH-NMR ~ N H ' I D - N - C H =cH I I CDC'3

114- 115 'C 3270 cm-1 3322 cm-1 252 nm

8.2 Y 107 T = 1.09

- = . 0.62

7 = 0.65

86-87 "C 3120cm-* 3300 cm-1

215 nm 3.6 Y 10, AB JAB = 12 Hz,

AB JAB = 12H2,

7 0.60

TA = 1.10

TB = 0.57

The isomerization can be followed by I R spectroscopy. The rate constants for equilibrium and the free activation enthal- pies of ( I b ) for equilibrium starting from ( I b ) of 4.9 x 10-3 s-1 ( A G # = 21.0 6 0.2 kcaljmole) and from ( l a ) of4.9 x 10-4 s-1 (AG' = 22.4 k 0.2 kca1;mole) were determined on the basis of a first order reaction. The values for secondary thio- formamides 151 are of the same oder of magnitude, but some- what higher.

N 2-A4ethyl-N2-phenylthioforrnohydrazide (I)

A solution of N-methyl-N-phenylhydrazine (0.05 mole) in triethylamine (30 ml) is added dropwise and slowly with vigorous stirring to a solution of 0-ethyl thioformate (0.5 mole) in triethylamine (15 ml); the reactants are kept ice cold during the addition and the reaction mixture is stirred for a further hour. The solvent is then removed by means of a rotatory evaporator and the residual oil is treated with petroleum ether. A crude crystalline product precipitates (yield 91 %). Recrystallization from nitromethane yields ( l a ) as broad yellow crystals (m.p. 11Gl15 "C). ( l a ) is dissolved in an excess of chloroform and allowed to stand at room temperature for five hours. After removal of solvent in a rotatory evaporator, the crude product is recrystallized from nitromethane. Compound ( l b ) is obtained as colorless needles, m.p. 86-87 "C. The melt crystallizes at 90-95 "C and melts once again at 113--114"C, i.e. when (16) has once again rearranged to ( l a ) .

Received: October 6, 1969 [ Z 108 IE1 German version: Angew. Chem. 81, 1050 (1969)

[*I Prof. Dr. W. Walter and H. Weiss Institut fur Organische Chemie und Biochemie der Universitat 2 Hamburg 13, Papendamm 6 (Germany)

[l] On the Structure of Thioamides and Their Derivatives, Part 10. - Part 9: W. Walter, H . P. Kubersky, and D. Ahlquist, Liebigs Ann. Chem., in press. [2] a) W . Walter and K:J. Reubke, Angew. Chem. 79, 381 (1967); Angew. Chem. internat. Edit. 6, 368 (1967); Tetrahedron Letters 1968, 5973; b) U. Anthoni, P . Jakobsen, Ch. Larsen, and P . H. Nielsen, Acta chem. scand. 23, 1820 (1969). [3] W. Walter and K.-J. Reubke, Chem. Ber. 102, 2117 (1969). [4] J . Suzuki, M . Tsuboi, T. Shimanouchi, and S . Mizushima, Spectrochim. Acta 16, 471 (1960). [5] E. Schaumann, Diplomarbeit, Universitat Hamburg 1968.

X-Ray Structure Analysis and Absolute Configuration of

(+)-1-m-Bromobenzoyl-4-methylazetidin-2-one

By E. F. Paulus, D . Kobelt, and H . Jensen[*l

The enantiomers of optically active p-lactams can be obtained by separation from their racemic mixtures [I]. Thus, roc-4- methylazetidin-2-one, m.p. -1 2.4 "C, yields enantiomers having m.p. +26.7"C and [a]: = + or --8.22" (melt). On hydrolysis the levorotatory form is converted into (S)-(+)-@- aminobutyric acid [zl; the (S)-configuration can therefore be ascribed to the (-)-4-methylazetidinone (31. While carrying out an X-ray determination of the steric features of the p-lactam ring we attempted a confirmation of the absolute configura- tion at the same time. In order to do this it was necessary to introduce an anomal- ously scattering atom (for M O K ~ rays) into the molecule. This was achieved by acylation of (-)-4-methylazetidinone with m-bromobenzoyl chloride in ethyldiisopropylamine. (+)-1 -tn-Bromobenzoyl-4-methylazetidin-2-one, m.p. 88 "C, [a];* = +255.0 (c = 3 gjl00 ml; methanol), crystallizes in the space group P212121 with a = 11.86+ 0.01, b = 9.41 i-

cm3 (suspension method). The intensities of the X-ray reflections were measured with a single-crystal diffractometer 171. Of the 1834 reflections re- corded, 643 had a statistical error of measurement of <YO%, 505 an error of between 10 and 50%; these 1148 reflections were used in the structural analysis. The heavy atom method was used for the determination of the phases for a Fourier synthesis of the electron density. A complication encountered was that the x-coordinate of the bromine atom was about 0.5. In the first Fourier synthesis, therefore, both molecular configurations appeared a t the same time. The atomic parameters of both configurations were refined by the method of least squares (full matrix). The R-factor (R = [(Cw( 1 Fo I - I F, 1)2) / (Cw 1 Fo I2)I1/z for the ( S ) - configuration is 6.05 % and for the (R)-configuration 7.49 %. According to Hamilton [4J, the probability for the @)-config- uration is greater than 99.9 %. The difference between the R- factors of both configurations is therefore unusually great [ 4 3 .

Thus the (S)-configuration is proved by X-ray analysis. The figure shows a projection of the molecule on the "best" plane of the p-lactam ring. The nitrogen of the four-membered ring is only 0.08 A above the C(7)-C(8)-C(lO) plane, thus indicating that the N-C(7) bond is turned about 7.7 out of the N-C(8)-C(l0) plane. The planes N-C(9)-C(lO) and N-C(8)-C(9) are at an angie of 2.1 ". This siight deviation of the four-membered ring from planarity is near the limit of significance (average standard deviation of bond angles: 0.8 ").

0.01, c = 9.80 ?z 0.01 A; Z = 4; dx-ray = 1.63, dexp = 1.61 g/

0-2 * 0 "8 c-10

c-3

Angew. Chem. internat. Edit. Vol. 8 (1969) J No. 12