Alcoholysis of phosphorus(III) isocyanate

Notes RF~ULTS AND DISCUSSION It is apparent from the results presented in the experimental section that different complexes of AgO) were recovered depending on the reaction conditions and the counter ion for silver. The silver(I) nitrate complex with ppyz, (AgNO3)3(ppyzh, exhibited a conductance in water of 368 cm~ mho at a concentration of 1.01 x 10-3 M. By comparison, salts dissociating to yield 3 to 4 ions in aqueous solution (10-3) have AM values, respectively of 225-270 and 380--432[6]. Therefore it appears that the Ag(I) complex behaves similar to salts to give 4 ions: [Ag3(ppyzh] (NO,h. The IR spectrum exhibits bands characteristic of coordinated ligand and, of greater interest, bands assignable to the nitrate moiety. A very strong nitrate absorption for the complex occurs at 1360cm -~ compared to that for AgNO3 at 1358cm -I. In addition a single weak band was observed at 1740cm -1 using 5X scale expansion. Many papers have appeared which suggest appropriate correlations between the coordination mode and observed absorption bands[7,8]. The combination band region, 1700-1800 cm-', has been shown to be particularly helpful in differentiating between bands; ionic nitrate exhibits one band while two bands are observed for either bidentate or monodentate coordination[8]. Silver(I) nitrate exhibits two bands at 1754 and 1774cm -~, indicative of asymmetric nitrate[8,9], while the (AgNO3)3(ppyz)2 complex shows a single absorption at 1742 cm-k Therefore it appears from both the conductance and IR data that only ionic nitrates are present in both solution and the solid state. The visible spectrum of (AgNO3h(ppyzh in aqueous solution contained no absorption bands while in the ultraviolet region maxima occur at 315, 307, 302 and 258nm. The intraligand transitions in free ppyz are observed at the same energies. Concentrated solutions of the complex appear pale yellow in color apparently as a consequence of a tail of a UV maximum extending into the visible region. It is interesting to contrast the stoichiometry of the nitrate complex with those obtained when the counter ion is CIO,- or PF6-. The solubility of the 1:1 complex obtained from the reaction of excess AgC104 with ppyz is evidence for a non

1455

polymeric species. IR and conductivity data establish the presence of ionic perchlorate. Equal molar ratios of AgC10, and ppyz yield (AgClO,)2(ppyzh. An analogous salt, (AgPFt)2(ppyzh is obtained from the reaction of 3 mole of NH,PF6 with (AgNO3h(ppyz)2. Unlike pyrazine and 1,5-napy, in no case was evidence for a 1 : 1 polymer of ppyz with Ag(I) found. For the complex cation (AgC10,h(ppyzh it is easy to envision silver(I) in a 2 coordinate linear geometry created by N-I, N-5 (or N-I, N-4) coordination to the ppyz ligands. Most unusual, however, is that the Ag(I) in [Ag3(ppyzh] ÷ species would be unable to assume its expected geometry. In this complex, ppyz may be behaving similarly to that of 1,8-napy in the Ag(1,8-napy) ÷.

Clippinger Laboratories Department of Chemistry Ohio University Athens, OH 45701 U.S.A.

ROBERT J. STANIEWICZ DAVID G. HENDRICKER

REFERENCES 1. G. G. Vranka and E. L. Aroma, lnorg. Chem. 5, 1020 (1%6). 2. R. W. Stotz, J. A. Wamsley and F. Warnsley, Inorg. Chem. 8, 807 (1%9). 3. H. J. Stoklosa, J. R. Wasson, E. V. Brown, H. W. Richardson and W. E. Hattield, Inorg. Chem. 14, 2378 (1975). 4. A. Emad, Ph.D. Dissertation, Montana State University, Bozeman Montana (1971). 5. C. L. Leese and H. N. Rydan, J. Chem. Soc. 303 (1955). 6. M. M. Jones, Elementary Coordination Chemistry, Prentice Hall, New Jersey (1964). 7. C. C. Addison and D. Sutton, In Progress in Inorganic Chemistry (Edited by F. A. Cotton), Vol. 8, Interscience, New York (1%7). 8. A. B. P. Lever, E. Mantovani and B. S. Ramaswamy, Can. J. Chem., 49, 1957 (1971). 9. P. F. Lindley and P. Woodward, J. Chem. Soc. (A), 123 (1%6).

z inorg,nucl.Chem.,1977,Vol.39, pp. 1455-1456. PergamonPress. Printedin GreatBritain

Alcoholysis of phosphorus(III) isocyanate (Received 24 June 1976) Addition of alcohols to organo- and halophosphorus isocyanates has been shown to yield two types of products depending upon the nature of the substituents and the oxidation state of the phosphorus. Alkyl and arylphosphoryl isocyanates (I) and their halo, alknxy or aryloxy analogues (II) have yielded

halophosphine isocyanates (III) with alcohols, while alkoxy or aryloxy derivatives (IV) undergo substitution to yield the alkyl or aryl phosphites and alkyl carbamates[2]: 0

U

ROP(NCO)2 + 4R'OH ~ ROP(OR')2 + 2R'OC--NH2. (2) O

LI

To date, however, no reports have been published as to the nature of the products formed upon allowing alcohols to react with the parent compound, phosphorus(III) isocyanate.

R.P(NCO)3_. I. R = alkyl, aryl II. R = alkoxy, aryloxy, fluoro, chloro

EXPEP.D4ENTAL Reagents. Phosphorus(III) isocyanate was prepared by reaction

R~ P(NCO)3_~ IlL R = alkyl, aryl, chloro IV. R = alkoxy, aryloxy carbamates [1, 2]: 0

II

0

IL

0

II

R~P(NCOh_. + R'OH ~ R.P(NHC--OR')3_..

(1)

Similar addition occurs upon reaction o f t h e alkyl, aryl or

of silver cyanate with phosphnrus(III) chloride[3]. Purity was monitored periodically via its IR spectrum. Methanol and ethanol were absolute reagents, freshly distilled from magnesium. n-Butanol was freshly distilled from calcium oxide. All reagents were stored under nitrogen. Analytical and spectral data. Elemental analyses were performed by Alfred Bernhardt, West Germany. IR spectra were recorded on a Perkin-Elmer 621 Spectrophotometer. Solid derivatives were scanned as Nujol mulls while the oils were observed as neat liquids. Proton magnetic resonance spectra were recorded on a Varian 56/60 using deuterochloroform as solvent and tetramethylsilane as the internal standard. 3T spectra were

1456

Notes

recorded on a Varian XL-100-FT using neat reaction fiquids and 85% phosphoric acid as an external standard. Methanolysis. In a 25 ml flask, equipped with a magnetic stirrer, reflux condenser, equilibrating dropping funnel and nitrogen inlet was placed 1.62g (10.3 mmole) of phosphorus(III) isocyanate. Methanol (1.32 g, 41.2 mmole) was allowed to flow in from the dropping funnel over a period of ten minutes. The ensuing exothermic reaction was accompanied by formation of a white precipitate. After stirring for an additional twenty minutes, 20 ml of an equal volume mature of methanol-diethyl ether was added and the mixture stirred for a final twenty minute period at room temperature. Vacuum filtration of the mixture through a frit yielded 0.48 g of methyl allophonate, HeNC(O)NHC(O)OCH3 (26% yield based upon P(NCO)3), m.p. 208-210 ° (lit. value 208-210°[4]). Anal Calcd for C3HtN203: C, 30.51; H, 5.12; N, 23.72. Found: C, 30.65; H, 5.20; N, 23.57. Identity of the compound was further confirmed by mixed m.p. with an authentic sample of methyl allophonate [4]. Evaporation of the filtrate yielded 2.19 g of a colorless oil which decomposed upon attempts at vacuum distillation. This viscous oil exhibited IR absorptions at 3345 and 3200 (N-H), 3000 and 2960 (C-H), 2400 (P-H), 1705 and 1675 (carbamate C=O), 1355 (ester C-O), 1241 (P=O), 1192 and 1036 (P-O) and 981 (P-H) cm-L Assignments were derived from [5]. The proton magnetic resonance spectrum of the oil shows a broad hump at 8 6.1 ppm (N-H), an intense singlet at 8 3.78 (carbamate methyl) and a complex series of doublets at 8 3.5--4.12 (P-OCH3). The 3~P spectrum indicates the presence of roughly equal concentrations of dimethylphosphonous acid (doublet of septets at A - 11.7ppm, ~Jpn = 710 c.p.s, 3Jvoc~ = 12.2 c.p.s; lit. value[6], A-ll.4ppm), methyl N-(dimethoxyphosphinyl) carbamate (doublet of septets at A-34.6 ppm, 2JpN~ = 17.6 c.p.s, 3Jpocn = 11.3 c.p.s) and a trace of trimethyl phosphite (A-140ppm; lit. value, A-141ppm). Absolute concentrations were not determined because of variation with time. Solvolysis in ethanol and n-butanoL The procedure described above was repeated with ethanol and n-butanol. The principal modification in each case was the use of diethyl ether as the precipitating agent for ethyl allophonate and an equal volume mixture of diethyl ether-petroleum ether for precipitation of the n-butyl derivative. Ethyl allophonate, m.p. 188-190° (lit. value 188--191°[4]) was obtained in 29% yield. The n-butyl allophonate, m.p. 146-149o (lit. value 149-151°[4]) was obtained in 32% yield based upon P(NCO)3. No attempt was made to characterize the oils isolated from the respective filtrates other than to confirm the similarity of the IR spectra with that of the oil obtained in the methanolysis reaction. R~ULTS AND DISCUSSION The alcoholysis of phosphorus(II1) isocyanate appears to involve a complicated series of competing reactions. First, the alkyl alcohol either adds to the isocyanate moiety to yield a carbamate ester, equation 3, or functions as a weak acid, cleaving the phosphorus-nitrogen bond to yield isocyanic acid and an alkoxy-phosphine, eqn (4). Full substitution would ultimately

result in formation of the respective trialkyl phosphite.

I

H O

I I II

--P--NCO + R--OH --* - - P - - N - - C - - O R

(3)

--I~--NCO + R--OH "* --I~--O--R + HNCO

(4)

R = CH3, C2H5,n-C,sH9 Secondly, the isocyanic acid formed can either react with the excess alcohol to yield an alkyl allophonate, eqn (5), or cleave the phosphorus-oxygen bond in the trialkyl phosphite to produce a dialkylphosphonous acid, eqn (6). O H O

H I II

2HNCO + R--OH --* H2N--C--N--C--OR

(5)

O

II

HNCO + P(OR)3 - , RNCO + H--P(OR)2.

(6)

Both of these steps have been observed previously. Addition of isocyanic acid has been utilized as a preparative route to alkyl allophonates[4]. Trialkyl phosphites have been reported to react with hydrogen chloride to yield dialkylphosphonous acids and alkyl chloride[7]. Attack by isocyanic acid would appear to be analogous and an expected manifestation of the pseudohalogen character of the cyanate group.

Acknowledgements--This work was partially supported by the Research Corporation. The assistance of Prof. John H. Richards in obtaining the ~'P spectra is gratefully acknowledged. Joint Science Department R.J. DIMAND Claremont Men's, Pitzer and Scripps Colleges R. P. PINNELL Claremont, CA 91711 U.S.A.

REFERENCES 1. For a review of the preparation and properties of the phosphorus isocyap.ates see G. I. Derkach, Angew. Chem. Internat. Edit. 8, 421 (1969). 2. P. R. Steyermark, Z Org. Chem. 20, 3570 (1963). 3. R. E. Zobel and R. P. Pinnell, lnorg. Synth. 13, 20 (1972). 4. H. W. Blohm and E. I. Becker, Chem. Rev. 51, 471 0952). 5. N. B. Colthup, L. H. Daly and S. E. Wiberley, Introduction to Infrared and Raman Spectroscopy. Academic Press, New York (1964). 6. V. Mark, C. H. Dungan, M. M. Crutchfield and J. R. Van Wazer, Topics in Phosphorus Chemistry (Edited by M. Grayson and E. J. Gri~th), Chap. 4. Vol. 5. Interscience, new York (1967). 7. M. DeMarcq and J. Slezima, Bull. Soc. Chim. 7, 1, 1605 (1975).

L inorg,nucl.Chem.,1977,VoI.39, pp. 1456-1457. PergamonPress. Printedin GreatBritain

Thermal studies on lead(II) salts.--V. Enthalpies of formation of lead(H) oxide carbonates by scanning calorimetry (Received 10 November 1976) In recent studies of the thermal decomposition of lead(II) carbonate[l] and lead(II) hydroxide carbonate[2] (white lead), the following reaction stoichiometries were deduced: (a) for the decomposition of lead carbonate: 6PbCO~ = 3(PbCO3.PbO) + 3CO2

(1)

3(PbCO3.PbO) = 2(PbCO3.2PbO) + C02

(2)

2(PbCO3"2PbO) = 6PbO + 2{202

(3)

(b) for white lead: 2(PbCO3.Pb(OH)2) = 2(2PbCO3.PbO) + H20 2(2PbCO3.PbO) = 3(PbCO3-PbO) + CO2 3(PbCO3.PbO) = 2(PbCO3.2PbO) + CO2

(4) (5) (2)