CONCLUSIONS

I. The reactions of ethyldichlorophosphite and diethylchlorophosphite with benzylidene- methylamine proceed with the formation of 2-chloro-2-oxo~1,4-dimethyl-3,5-diphenyl-1,4,2- diazaphospholane and 2-ethoxy-2-oxo-1,4-dimethyl-3,5-diphenyl-1,4,2-diazaphospholane, respec- tively. The reaction of a mixture of diethylchlorophosphite and triethylphosphite with ben- zylidenemethylamine leads to diethyl-(N-methyl-N-a-diethylphosphonebenzyl)amidophosphite, while ethylenechlorophosphite reacts with benzylidenemethylamine to form a 2:2 addition prod- uct, namely, 1,4-dimethyl-2,5-dioxo-2,5-bis(B-chloroethoxy)-3,6-diphenyl-1,4-diaza-2,5-di- phosphane.

2. Evidence is given to indicate that the reaction of the P(III) acid chlorides with benzylidenemethylamine begin with the nucleophilic reaction of the imine nitrogen atom and chloride phosphorus atom.

LITERATURE CITED

I. A.M. Kibardin, T. Kh. Gazizov, and A. N. Pudovik, Izv. Akad. Nauk SSSR, Ser. Khim., 1452 (1980).

2. A . M . K iba rd in , T. Kh. Gazizov, and A. N. Pudovik, I zv . Akad. Nauk SSSR, Ser. Khim., 2186 (1980).

3. A.M. Kibard in , T. Kh. Gazizov, and A. N. Pudovik, Izv . Akad. Nauk SSSR, Ser. Khim., 1908 (1981).

4. 4" Kirby and S. Warren, Organic Chemistry of Phosphorus, Elsevier [1967). 5. E.E. Nifant'ev, The Chemistry of Organophosphorus Compounds [in Russian], Mosk. Gos.

Univ., Moscow (1971).

A PMR STUDY OF THE REACTION OF TRINUCLEAR OSMIUM

CLUSTERS HOs3(X)(CO)L0 WITH ORGANIC ACIDS

E. D. Korniets, V. A. Maksakov, L. K. Kedrova, N. I. Shakot'ko, and S. P. Gubin

UDC 543.422.25:542.91:541.49:546.94:547.29

Tricarbonyl osmium carbonyl clusters are usually protonated at the metal atom to form cluster cations which contain a bridging hydride [I, 2]. The replacement of the carbonyl groups by phosphine ligands enhances the basicity of the metal atom such that in some cases, two protons are added by the action of H2SO~ on phosphine derivatives of Os3(C0) 12 and bi- nuclear cluster cations are formed [3, 4]. The presence of bridging SR groups (R = C2H5, C~H5) in the cluster bonded to two metal atoms does not lead to a change in the direction of protonation [3].

In the present work, we studied the reactivity of clusters (I) relative to CF2CQH. The presence of a free electron pair on the tricoordinated uncharged oxygen atom in clusters (Ic) and (Id)

\ X = H(Ia), /

.Os(CO)4

(CO) o ~ H ~ o s ( C O )

NHC6Hs(I b), N'OC6Hs(Ic), ~OH(Id) / /

Institute of Chemistry and Chemical Engineering, Siberian Branch, Academy of Sciences of the USSR, Krasnoyarsk. Institute of Inorganic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 435-439, February, 1983. Original article submitted March 11, 1982.

0568-5230/83/3202-0393507.50 �9 1983 Plenum Publishing Corporation 393

and the capacity of the oxygen atom to exist in a tetracoordinated state as in [(CH3)3PtOH]4 [5] does not exclude the transfer of the reaction site from the metal to the ligand upon protonation of (Ic) and (Id) by organic acids.

RESULTS AND DISCUSSION

Clusters (Ia), (Ib), and (Ic) readily react with CF3COzH upon dissolution to form cations [H2Os3(X)(CO):0] + (Table I). The PMR signals of both hydrides are somewhat broadened, indi- cating intramolecular exchange. The salts formed are stable upon prolonged standing in CF3CO2H solution and readily deprotonate to form the starting compounds upon removal of the acid. Cluster (Id), in contrast to (Ia-c), reacts with CFBCOzH by reaction (I) to form (II) which contains a bridging trifluoroacetate group. The reaction proceeds quantitatively with dissolution of (Id) in the acid. The presence of only the signal for (II) in the PMR spec- trum of solutions of (Id) in CF3CO2H and the absence of a second hydride signal (see Table I) may be attributed either to the low basicity of the metal atoms in (II) for protonation by trifluoroacetic acid or rapid exchange of the hydride by the acid proton relative to the PMR time scale.

/Os(CO)4 Os(CO)4

.

I 0_-. -0

I It

R = CFs(II), CH3(III), CD2(IV), H(V)

( I )

Product (II) is readily formed from (Id) in a medium with much lower acidity. Upon the dissolution of (Id) in CC14 containing 0.06 mole/liter CFBCOzH, reaction (I) also proceeds upon dissolution of the cluster and the PMR spectrum of the solution obtained contains only the signal for the hydride ligand of (If). The reaction of (Id) with CH3COs and CD3CO2D at ~20~ proceeds at very low rates, which permitted determination of some kinetic parameters of reaction (I). In the case of a considerable excess of acid [solutions of 0.05 mole/liter (Id) in CH~CO2H and CD3COzD] , the reaction proceeds with first-order kinetics relative to the cluster. The kH/kD kinetic isotope effect is 2. The period for 50% conversion of (Id) to (III) is about 46 days. We should also note that the hydride is not replaced by D in the reaction of (Id) with CDsCO2D (within the sensitivity of the PMR method), i.e., reaction (I) may be seen formally as the replacement of the bridging OH group by an acetate group.

The reaction of (Id) with HCO2Halso leads to substitution of the OH bridging group and formation of (V).

The PMR spectrum of a solution of (Id) in CH3CO2H does not show the signal for the OH group of (Id) as a result of rapid proton exchange betweeen CH3CO2H and (Id). This exchange may be observed on the NMR time scale upon the addition of small amounts of acetic acid into a solution of (Id) in CC14. The rate of exchange increases with increasing acid concentra- tion, which corresponds to a decrease in the mean effective lifetime (T) in each of the pos- sible states (Table 2). Low concentrations of (Id) and acetic acid as well as large line- widths due to exchange lead to a low signal-to-noise ratio. Hence, the error for T in this case is 20-30%, which does not permit us to make any conclusions concerning the kinetics of the exchange reaction, l~ne values for ~ found indicate high lability of the proton of the OH bridging group of (Id) in exchange reactions with acids.

One of the possible mechanisms for reactions (I), namely, scheme (2),

" O,s(CO)4 " os(c~ ]q-41 Os(CO) 4

H H Ii ' (C0)30 ~ --Os(CO)s ~ (CO)aO s(eO)a "4- 1t20 (2) (co)so~? o~(co)s. + ::cooH--~ ~o/~ ~.:~_~ o

11 I. (v.:) R

394

TABLE I. Chemical Shifts of the Hydrogen Atoms in the PME Spectra of (la-d) in CF3CO2H (C ~< 0.05 mole/liter)

~, * (relative ~2 * (relative Compound intensity), ] intensity),

ppm [ ppm

(l~) (Ic) (id)

-12,2 (2) - t4,3 (1) -t4,5 (1) -ls,0(~) - t3,4 (t) -16,4 (i) -t0,2 ?

*All signals are somewhat broadened. ~Signal for compound (II).

TABLE 2. Dependence Of T~ on the CH3CO2H Concentration in a Solution of 0.023 mole/ liter (Id) in CC14 at 23~

C H3COzH con- I I centradon 0,0t~ 0,077 o,ii3 0,227 mole / liter

'~'J-0 ~, sec 9,3 8,2 [ 7,5 ! 7.0

~T is the mean effective lifetime for the exchange reaction: CH3COOH* + HOs3(OH)- (CO) j0 ~- CH3COOH + HOs3(OH*)(CO)i0.

entails protonation of the metal atom and subsequent loss of a water molecule and addition of a bridging acetate ligand.

Trinuclear osmium clusters containing a bridging hydride ligand replace one-half the starting hydrogen atoms by deuterium in reactions with D2S04 as a result of intramolecular exchange between nonequivalent hydrides in cation (VI) [3]. Such a replacement of hydride H by D in the reaction of (Id) with CH3CO2D was not observed. This failure is evidence against the formation of cation (VI) as an intermediate. This hypothesis is also indicated by the finding that reaction (I) proceeds in media with low acidity such as CH3CO2H and 0.06 M CF3CO2H in CCI~, in which protonation of the metal atom is unknown. Indirect evidence against scheme (2) for reaction (I) lies in the kinetic isotope effect found (kH/k D = 2) since it is in the range from 7 to 17 for the protonation of cluster compounds [6]. In particular, kH/ kD = 11 for 0s3(CO) 12.

The reaction site in the reaction of (Id) with organic acids is probably shifted from the metal atom to the iigand as a result of the capacity of the bridging OH group to display both basic properties (due to a free electron pair) and acid properties, which are evident in the facile exchange reactions with acids. The replacement of the bridging OH group in reactions with organic acids is possible either by scheme (3) or (4)

9s(CO)4 o.s(co) 4 o s(co) 4 .

ooo - o l . ~ o / ~ <co)ao s(Co)~ > (co)~o ~(c.o)~ I / \

o.s(co) 4 os(co) 4

(vn)

,(coh

(hObO s(c/o) 3

O~ -O

I

(3)

(4)

If the reaction proceeds by scheme (3), then an analogous replacement of the bridging ligand should be seen in the reactions of (Ic) and HOs3(SR)(CO)I0 (R = C2H5, C6H5). However, in accord with our results and the findings of Deeming et al. [3], the osmium atom is pro- tonated in these cases. Thus, the free electron pair on the ligand heteroatom is not the only cause for the replacement of the OH group by an acid residue. The difference in the OH and SR ligands in trinuclear osmium clusters from the OH bridging group lies in the display of acid properties by the OH group. Hence, reaction (I) is more probable not by scheme (3) but through the formation of the associated species (VII) formed between an acid molecule and the cluster with subsequent conversion by scheme (4). Associated species (VII) may also be an intermediate in the proton exchange reactions of (Id) with acids. The possibility of form- ing associated species such as (VII) is lacking for (Ia-c). This failure, in particular, re- sults in the absence of exchange of the NH group protons with acid protons on the i~R time scale upon the dissolution of (Ib) in CHgCO2H.

395

Thus, the transfer of the reaction site from osmium to the ligand in the reaction of (Id) with organic acids found in this work is a consequence of the acid-base properties of the OH group bound to two metal atoms. We should also note that reaction (I) may be used to intro- duce organic ligands into the cluster which contain a carboxyl group.

EXPERIMENTAL

The PMR spectra were taken on a Tesla BS-467 spectrometer at 60 MHz at ~20~ The error for the chemical shifts was • ppm. The internal standard was cyclohexane. The IR spec- tra were obtained on a Specord IR-75 spectrometer. The mean effective lifetime T (see Table 2) was found by comparison of the experimental line shape with the theoretical shape for two- center exchange according to Binsch [7]. The starting compounds (Is-d) were synthesized ac- cording to published procedures [8-11].

The protonation of (Ia-c) was carried out by dissolution of the corresponding compound in CF~CO2H. The NMR spectra were recorded and then the acid was removed from the solution by evaporation in vacuum. Washing of the residue with acetone gave the starting compounds.

Reaction of HOss(OH)(CO)z0 (Id) with CH3CO2H and CD3CO2D. Samples of 22 mg (Id) were dissolved in 0.5 ml CH3CO2H and CD3CO2D, respectively, containing a weighed amount of cyclo- hexane. The solutions were transfered to NMR tubes and sealed in an argon atmosphere. The reaction was followed by the ratio of the signals of the hydride ligands of (Id) and of the reaction product. The presence of deuterium in the metal ring was determined by the ratio of the hydride signal integrals for (Id) and the reaction product to the cyclohexane signal integral. The observed pseudo-first-order rate constants were found graphically by the method of least squares as the slope of the lines for plots of In ([Id]0/ lid] t) vs time, where [Id]0 and [Id] t are the initial and current concentrations of (Id) (moles/liter). The current con- centration of (Id) was determined from the integral intensities of the hydride signals of the reaction product and of (Id). The reaction PrOducts HOs~(CH3C02)(CO)2 (III) and HOs3(CD3CO2)- (CO) z0 (IV) were isolated chromatographically on silica gel 100/160 using 3:1 hexane--benzene eluent. The yield of (III) and (IV) was quantitative for reacted (Id). For (III): IR spec- trum (in cyclohexane, ~, cm-l): 2117 m, 2080 s, 2067 s, 2032 s, 2019 s, 1992 sh, 1988 m, 1562 m. PMR spectrum (in CC14, ~, ppm): 1.9 s (3H, CH3), --10.5 s (IH, Os--H). For (IV): IR spec- trum (~, cm-l): 2108 m, 2070 s, 2061 s, 2023 s, 2010 s, 1982 m, 1545 m. PMR spectrum (in CC14, 6, ppm): --10.5 (Os--H).

Reaction of HOs3(OH)(CO)10 (Id) with CF3CO2H. A sample of 3 mg (Id) was dissolved in 0.5 ml CF3CO2H at %20~ After complete dissolution, the acid was removed by evaporation in vacuum and the residue was separated on a silica gel 100/160 column with 3:1 hexane--benzene eluent to yield 32 mg (97%) HOs3(CF3C02)(CO)I0 (II). IR spectrum (~, cm-l): 2119 w, 2081 s, 2068 s, 2033 s, 2019 s, 1994 sh, 1991 m, 1647 m. PMR spectrum (in CC14, 6, ppm): --10.4 s (Os-H).

Reaction of HOs3(OH)(CO)z0 (Id) with HCO2H. A sample of 63 mg (Id) was dissolved in 5 ml anhydrous HCO2H and maintained for 5 h at 40~ The acid was then removed by evaporation in vacuum and the residue was separated on a silica gel 100/160 column with benzene eluent to yield 44 mg (68%) HOs3(HCO2)(CO)z0 (V). IR spectrum (~, cm-l): 2112 w, 2074 s, 2065 s, 2027 s, 2013 s, 1990 sh, 1985 m, 1579 m. PMR spectrum (in CC14, ~, ppm): 7.45 s (IH, H-~30, --10.6 s (IH, Os--H).

The IR and PMR data for clusters (II), (III) and (V) correspond to the spectral param- eters found for these compounds [9].

CONCLUSIONS

I. Compounds HOs3(X)(CO)10 (X = H,~ NHC~Hs, and~/OC6Hs) react with CF3CO2H by the /

addition of H + to the metal atom and formation of a cluster cation [H2Os3(X)(CO)z0] +

2. HOs3(OH)(CO)z0 reacts with RCO2H (R = CF3, CH~, CD3, and H) with replacement of the bridging OH group by the RCO2 group.

3. These results indicate the transfer of the reaction site from the metal atom to the ligand for the reaction of HOs3(OH)(CO)10 with organic acids and a likely mechanism for this reaction is proposed.

396

1 �9

2.

.

10.

11.

LITERATURE CITED

H. D. Kaesz and R. B. Saillant, Chem. Rev., 72, 231 (1972). A. A. Koridze, O. A. Kizas, N. M. Astakhova, P. V. Petrovskii, and Yu. K. Grishin, J. Chem. Soc., Chem. Commun., 853 (1981). A. F. Deeming, B. F. G. Johnson, and J. Lewis, J. Chem. Soc., A, 2517 (1970). A. J. Deeming, B. F. G. Johnson, and J. Lewis, J. Chem. Soc., A, 2967 (1970). G. L. Morgan, R. D. Rennick, and Chia Chu Soong, Inorg. Chem., 5, 372 (1966). J. Knight and M. J. Mays, J. Chem. Soc., A, 711 (1970). G. Binsch, Top. Stereochem., 3, 97 (1968). S. A. R. Knox, Y. W. Koepke, M. A. Andrew, and H. D. Kaesz, J. Am. Chem. Soc., 97, 3942 (1975). E. G. Bryan. B. F. G. Johnson, and J. Lewis, J. Chem. Soc., Salton Trans., 1328 (1977). K. A. Azam, A. J. Deeming, R. E. Kimber, and O. R. Shukla, J. Chem. Soc., Dalton Trans., 1853 (1976). V. A. Maksakov, L. K. Kedrova, E. D. Korniets, and S. P. Gubin, Abstracts of the Four- teenth All-Union Chugaev Conference on the Chemistry of Complexes [in Russian], Part I, Ivanovo (1981), p. 71.

THE EFFECT OF SUBSTITUENTS AT THE SULFUR ATOM ON THE GLYCOSYLATING

ACTIVITY OF D-GLUCOSE THIOORTHOESTERS

Yu. E. Tsvetkov, L. V. Bakinovskii, UDC 541.124:542.91:547.455 and N. K. Kochetkov

In our previous work [I-3], we showed that the 1,2-thioorthoesters of sugars are effi- cient and stereospecific glycoslyating agents in the synthesis of 1,2-trans-glycosides

+ rsR

The glycosylation by 1,2-thioorthoesters is accompanied by a side reaction involving the isomerization of the starting thioorthoesters to thioglycosides. This side reaction hinders the glycosylation of trityl ethers which have low activity [2] and the preparation of high- molecular-mass polysaccharides from sugar 1,2-thioorthoester monomers [4].

In our earlier work [27, we proposed a mechanism for glycosylation by thioorthoesters an and showed that the major contribution to the formation of thioglycosides is made by reaction (3), i.e., the reaction of sulfonium and/or acyloxonium ions with the starting thioorthoestero

This mechanism implies that the ratio of O- and S-glycosides formed in the reaction de- pends on the relative rates of reactions (2) and (3) [or of reactions (2) and (4)] (see top of next page). In addition to our previous procedure [2] which permits us to reduce the rel- ative rate of reaction (3) and thereby increase the yield of the desired O-glycoside, the effect of the nature of the substituent at the sulfur atom should affect the ratio of the rates of reactions (2) and (3). A decrease in the nucleophilicity of the sulfur atom is required to reduce the rate of reaction (3). This may be achieved by the introduction of an electron-withdrawing substituent. The rate of reaction (3) may also be reduced by in- creasing the steric hindrance by the introduction of bulky substituents. The reaction of a series of D-glucose thioorthoesters (I)-(IX) with trityl ether (X) was studied in order to follow the effect of both factors on the glycosylating activity of thioorthoesters. Ether

N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 439-443, Feb- ruary, 1983. Original article submitted May 11, 1982.

0568-5230/83/3202-0397507.50 �9 1983 Plenum Publishing Corporation 397