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Preparation and iminocarbonylation reactions of organoaluminium chelate compounds containing PvNMeAl bonds
.203 ‘. _
-..
:
Journal of Organomeiallic Chtimidy, 76 (1934) 203-&3 Q Else&r Sequoia S.A., Lausanne - Printed in The Netherlands
i’ : .~....
..
: . .:
PREPARATION AND IhNOCARBONYLATION REACTIONS OF ORGANOALUMCHELATE COMPOUNDS CONTAINING Pv-N&k-Al BONDS
KOkX3I
URATA,
KENJI ITOH and YOSHIO ISHII
Department of Synthetic Ckemistry, Faculty oy Engineering, Nagoya Univeisity. -ChikuSa. Nagoya, 464 (Japan) (ReceivedFebruary
ZOth, 1974)
:
New organoaluminium compounds containing Pv -NMe-Al bonds, diethylaluminium dialkyl N-methylphosphoramidate, (_R0)2P(0)NMeAlEt,, and tetraalkylphosphorodiamidic N-methylamide, ( R2N)z P(O)NMeAl& , were prepared. Cryoscopic -measurements showed these compounds to be dimeric by intermolecular coordination. The introduction of bulky substituents on the phosphorus atom decreased the degree of association. The coordination of oxygen atom of P=O bonds to organoaluminium moiety was indicated by spectroscopic evidence. In the reactions of (RO)zP(0)-NMe-AlEt2 with aromatic aldehydes or phenyl isocyanate, the corresponding irnino compounds were obtained by an addition-elimination process.
Introduction Some Group III organometallic chelate compounds of phosphinic acid derivatives have been studied [l-4]. In particular, organoaluminium, gallium and indium derivatives of alkyl (or aryl) phosphinic acids, RpP(0)--O-MR: , were shown to exhibit strong intermolecular interaction between R:M (M = Al, Ga and In) moieties and the oxygen atom of phosphinyl group. However, little was known about the structural or chemical behavior of organoaluminium chelates of phosphoramidates X2 P(0)-NMe-J.lE& . It is well known that the specific affinity of phosphorus to oxygen atom is the driving force of Wittig type reactions. In this context, the dialkyl N-alkylphosphoramidate anion was recently reported to act as an iminocarbonylating agent [5, S] _ In pseudo-Wittig type reactions of organoaluminium compounds, a facile formation of stable Al-O bonds is considered to be the key step. For example, thiocarbonylation reactions with (Et2 Al)* S [ 71 and iminocarbonyla.. tion with MezAl-NMe-&Me, [S] may be included in this category. Since both
:20x]
-..
&ganoalumlm ’ ‘um and organophosphorus groups show strong affinity to oxygen atoms, formation of a stable Al-O-? bond is expected in some-addition-&mi: . : n&ion reactio& Prom the above point of view, we describe here the preparation of diethyl.ahminhm derivatives of dialkyl N-methylphosphoramidates, (RO),P(O)-NMeALE& (Ib-Vb), and tetraalkylphosphorodiamidic N-methylamides (Rz N)Z .P(O)-NM+&& (VIb, VIIb), together with the iminocarbonylation by means of diethylaluminium dialkyl N-methylphosphoramidates. Results and dkussion Preparation of compounds X,P(O)-NMe-AlEt, (X = RO and R,N) (Ib-VIIb) Dialkyl N-methylphosphoramidate9 (Ia-Va), obtained by the reaction of dialkyl hydrogen phosphites with Ccl4 and MeNI& 19 1, reacted with triethylaluminium~to give the corresponding diethylalunki-um derivatives (Ib-Vb) in 6O-80% yield based on E&Al used (eqn. 1). benzene
(RO)zP(0)NHMe
(RO),P(O)NMeAlEt,
+ Et3Al -
80°C
(Ia-_Va)
+ C2Hs
(1)
W-Vb)
(I, R-s Me; II, Et; III, i-Pr; IV, i-Bu; V, i-Am) Tetraalkylphosphorodiamidic N-methylamide (Via, VIIa) gave the car-responding aluminium compounds (VIb, VIIb) according to eqn. 2. Yields, b.p.‘s and analyses of Ib-WIb are summarized in Table 1. (R,N),P(O)kHMe 07%
+ Et&l F
(R,N)AO)NMeAlEt, (VW
VBa)
+ CJG
(2)
wb)
(VI, R = Me; VII, Et) These compounds (especially Ib-Vb) were thermally stable (up to ca. 200”) and distillable under reduced pressure. Cryoscopic molecular weight determinations showed that these compounds were dimeric in benzene by intermolecular coordination in the case of less bulky substituents (RO = MeO, Et0 or Me?N). “\
7’
*-*‘\
x\P//
/Me
N
x’
I
I PiX
Me/“\
//‘X
AI-O ‘EC
(X =-
w 4
RO
‘ET and
_ R,N)
*
2
I Me
Me0
Et0
i-k0
i*BuO
i-Am0
MezN
Et2N
Ib
IIb
IIIb
IVb
Vb
VIb
VIIb
(0.01) (0.26) (0.13)
136-142 140-146 160-166 146-162 166-166 110-120 liquid
72
78
71
70
60
60
84
(0.3)
(0.6)
(0.28)
?&nnl,
Yield (%) 37.36 (37.67) 43.17 (43.03) 47.13 (47.31) 60.97 (60.80) 63.90 (63.72) 43.63 (43.37) 60.91 (61.13)
C
Com-
Et0 i-pro i.BuO i-Am0 Me2N Et2N
118, bb IIIa, IVa, b Va,b Via, b VIIa, b
‘In 2% benzene solution.
Me0
X
Ie, b
pound
1216,118O 1216,1176 1216,118G 1216.1190 1190,1166 1200,1170
1220,119o
1260,1243 1264,1236 1260,1236 1240,123O 1260,1236, 1216,119O 1220,1206
uB(p=o) oi Ib-VIIb
uA(p=o) of In-VIIa
-39, -36, -26, -36, -26, -20,
-66 -6C -46 -46 -36 -36
-63
Au(P=0) =vB(p-C) uA(P=0) -40,
11.92 (12.10) 10,90 (10.74) 9.63 ( 9.67) 8,66 ( 8,79! 8.76 ( 8.06) 11.26 (10.84) 9.34 ( 8.84)
Al
870 896 890 886 846 860
880
uA(p-N) Ia-VIIa
of
AND X2P(0)NMeAlEt2(Ib-VIIb)
8.67 ( 8.68) 9,27 ( Z) ( 9:74) 9.92 (10.17) 10.33 (10.62) 10,Ol (10.11) 10.66 (10.89)
H
Analysts found (colcd,) (%)
DATA OF THE COMPOUNDS X2P(O)NMeAIEt2
DIFFERENCES IN u(pzC) AND V(p-NJ BETWEEN XZP(O)NHMe (Ia-VIIa)
TABLE 2
X
Compound
PHYSICAL AND ANALYTICAL
TABLE 1
o
920 933 940 940 906 396
940
vB(P-N) of Ib-VIIb
(cm”)
470 (306)
466 (336) 416 (336) 474 (249)
390 (307)
406 (279)
466 (223) 381 (223) 406 (261)
la64
1.39 1.24 1.91
1.27
1.46
2.06 1.71 1.62
3.13
2.87 1.66 3.61
2,96
2.76
3.70 2.68 2.76
Concentration (wt %)
3”: 60 66 60 46
60
Au P-N) =v$ (P-N) uA(P-N)
M.W.(cnlcd. De&! of m monomer) association
. . 207. The introduction of bulky groups (RO = i-Pro, i-BuO, i-Am0 or EtlN) on. the phosphorus atom decreased the degree’of association. The-&& effect of the substituent on phosphorus is~exphtinedin tern% of tbe~dissociatibe.equilibrium between the intermole&larly cciord~ated dimer and the irkramoleculkrly coordinated moncmer (eqn. 3). In this connection, the preparation of the di-tert-butyl N-methylphosphorami~ date derivative, (t-BuO),P(O)NMeAlEt, , failed. Evolution of excess ethane occurred (ca. 1.5 - 1.7 times the theoretical value). ._ IR and NMR spectra of Ib-VIIb As shown in Table 2, the stretching frequency of P-0 bond in Ib-VIIb, showed values lower than in the original dialkyl N-methylphosphoramidates Ia-Va or in the tetraaikylphosphorodiamidic N-methylamides (Via, VIIa) (Av(P=O) ca. -20 to -60 cm-’ ), which suggests the coordination of oxygen atom of P=O bonds to diethylaluminium group. The stretching frequency of the P-N bond (850 to 950 cm-’ ) [lo] shifted to higher values on introduction of the diethylaluminium moiety [AZ@?--N) ca. 40 to 60 cm-’ ] . These two shifts’ of P=O (lower) and P-N (higher) stretching frequencies can be explained in terms of structure B or D, in which (p-d)n bonding between phosphorus and. nitrogen atoms is involved. When electronegative groups (RO or RpN) are linked to the phosphorus atom, it is reported that the contraction of 3d .orbitals increases their availability to (p-d)~ bonding [ll].
\/
O-AI
\/
/pI AN\Al-0 /\
‘NH I
P'
//\
(A)
\//Ok/
/p\N,A’L (Cl
_
_
\p/o\A,/ ’
\\,r
’
(0)
The NMR spectroscopic results are summarized in Table 3. Changes of coupling constant, J(PNCH), by introduction of the diethylaluminium group, provide important information about the P-N bond. Dialkyl N-methylphosphoramidates or tetraalkylphosphorodiamidic N-methylamides X*P(O)NHMe (X = RO, R2N) (IaLVIIa) showed J(PNCH) values around 10 to 12 Hz. These values increased to 16 to 17 Hz for the organoaluminium homologs XiP(0)NMeAIEt, (Ib-VIIb) as shown in Table~3. The increase of J(PNCH) by diethylahuninium group reflects the contribution of Cp?i)n interaction between phosphorus and
T,@LE4
. ..
RE&TION
I.:
:-
PRODUCTS
ceriJoll;i ixx&Jd&&’ -_ ._ . .. -.
..,
.1:
OF Ib. IIb WITH-CARBONYL
Pi&& (% yield)
-_
,
Et212
::
PhCIi=O
Ph-N=C=O
Ph-N=C=N-Me Ph-NIXONH-Me (RO)2P(O)NMeCONHPh Ph2ONMe
=
Ph2C=p. a Demekllated
with dilute hydrochloric
70. 86
74
_;;
P-MeOCg&CH=NMe
gMeO&jH&H~O
;
-.
[(EtO)~P
C(MeO)~P(O)IiMe.AlEt212
.-
:
._
COMPOUNDS-
._
71 :z 9 55
:: 40 0
30
acid and yield wzs obtained
by NMR
analysis.
nitrogen atoms (cf. Pv=N-CH;J(PNCH) 20 to 30 Hz) C-12,133. The change in coupling constants is also consistent with the strong interaction of oxygen with the aluminium atom.
Iminocarbonylation and ketone
reactions of (R0)2P(0)NMeAiEt2
with aromatic aldehydes
.
When diethylaluminium dimethyl (and diethyl) N-methylphosphoramidate (Ib and Ilb), reacted with aromatic aldehydes, the corresponding N-arylidenemethylamines were obtained in 70 to 80% yield along with diethylaluminium dialkyl phosphate (80 to 90% yield) (eqn. 4) as summarized in Table 4. The reaction between IIb and benzophenone was extremely slow even at 80”, probably due to a steric effect.
R”\p/o\*,/” RO’‘N/ ‘Et I +
Me
R”\p/o\ i’ Ad&L
AC\tz-O / H
(R =
Me,
Et)
Reactions of X2P(0)NMeAlEt, phenyl isocyanate
I-
‘i”Et
RO'I
,,/pt/O AA
““\ //“\ iEt Ro/p\o/A’\Et
Elimin.
(4)
[X = Me0 (Ib), Et0 (IIb) and Me2N (VIb) with
Phenyl isocyanate showed remarkable differences in reactivity which depended upon the degree of association’of the starting duminium compound. The reaction of dimeric compounds (R0)2P(0)NMeAlEt2 (Ib, Ilb) (R = Me, Et); with phenyl ispcyanate did.not proceed at room temperature; .On heating up to 800., a subsequent,elimination reaction occurred immediately. In the case of.Hb,- three products were present: methylphenylcarbodiimide (36%; elimina-
211 determined cryoscopically. Infrared spectra were recorded with a Japan Spectroscopic Co. Model IR-S and NMR.spectra were recorded with a Japan Electron Optics Co. Model C-6OHL using TMS as an internal standard. Elemental analyses of organoel uminium compounds were carried out by Alfred Bemhardt Microanal. Lab. in West Germany.
Preparation of diethyialuminium diaikyl N-methylphosphoramidates (Ib-Vb) and tetraalkylphqsphorodiaqzidic N-methylamides (Vlb, VIIb) The preparation of diethylal uminium dimethyl N-methylphosphoramidate (Ib) is described as an example; IIb-VIIb were prepared analogously. Dimethyl N-methylphosphoramidate (Ia )(2.44 g, 17.5 mmol) in 20 ml of benzene was added dropwise to EtjAl (1.99 g, 17.5 mmol) in 20ml benzene at room temperature. During the addition of Ia evolution of gas was observed. The reaction mixture was heated up to 8@ and refluxed for 1 h. After the gas evolution had ceased completely, the solvent was removed, and the product was distilled under reduced pressure to give liquid Ib, b.p. 135-142” /0.28 mm. Yield 2.81 g (72%) based on Etg Al used. See Tables 1-3 for data.
Reaction of Ib with aldehydes Benzaldehyde. Benzaldehyde (0.416 g, 3.92 mmol) in 10 ml of benzene was added dropwise to Ib (0.871 g, 3.92 mmol) in 10 ml of benzene at room temperature. After 15 h both absorption bands at 1700 cm-’ [v(C=O)] and 940 cm-’ [v(P-N)] had not vanished. The reaction mixture was heated to reflux. The two above-mentioned absorption bands completely disappeared, and the appearance of new band at 1650 cm-’ [v(C=N)] was noted. Removal of the solvent and distillation under reduced pressure gave N-benzylidenemethylamine, b-p. 75-80”/20 mm (lit. b.p. 600/8 mm) [15], 0.35 g (yield 74%) and a residue, 0.81 g (yield 98%) of diethylaluminium dimethyl phosphate [ (MeO)2P(0)-O--AlEt, 1. N-benzylidenemethylam-he showed the same infrared and NMR spectra as the authentic compound [I63 . p-Anisaldehyde. In an analogous manner, reaction of lb, (0.645 g, 2.90 mmol) in 10 ml benzene and p-anisaldehyde (0.395 g, 2.90 mmol) in 10 ml of benzene gave by distillation under reduced pressure N-p-methoxybenzylidenemethylamine, b.p. 63-65°/0.08 mm, 0.30 g (yield 70%). Spectroscopic and physical data of the isolated product were identical with those of an authentic sample. A residue, 0.538 g (yield 88% as diethylaluminium dimethyl phosphate), was also obtained.
Reaction
of Ib with phenyl
isocyanate
Phenyl isocyanate (0.338 g, 2.83 mmol) in 10 ml of benzene was .added drop--=t--wise to ib, (OhL9 g, 2.83 mmoij k 10 mi of benzene at room temperahqe. After 16 h, both absorption bands at 2260 cm-’ [Y(NCO)] and 940 cm-’ [v(PN)] remained. The reaction mixture was heated to 80” and refluxed for 6 h. Both of the above two absorption bands disappeared completely and new bands at 2130 cm-’ [v(NCN)] , ch~acteristic of N-methyl-N’-phenylcazbodiimide, 1695 and 1650 cm-’ appeared. After hydrolysis of the mi&ure with dilute hydrochloric acid the product was extmcted with benzene. The benzene solution was dried with anhydrous NaZSO4 ; removal of the solvent gave 0.511-g. of an oil. NMR analysis of this oil showed the presence of N-methyl-N’-phenylcarbodiimide (60%) and
-212
PhNHCONHMe (40%). The authentic sample of carbodiimide was prepared according to ref. 17. Reaction of IIb with aldehydes and ketones Benzaldehyde; When a mixture of benzaldehyde (0.250 g, 2.32 mmol) and IIb, (0.584 g, 2.32 mmol) in 20 ml of benzene was kept at room temperature for 24 h and heated at reflux for 12 h, absorption bands at 1700 cm-’ [Y(C=O)] and 920 cm-’ [v(PN) J disappeared, and a new absorption band at 1650 cm-’ [v(C=N)] appeared. The products were PhCH=NMe (0.19 g, 70%) and (EtO)* P(Oj-o-AIEt2 (0.51 g, 92%). p-Anisaldehyde. In an analogous manner a mixture of IIb, (d.871 g, 3.50 mmolj and p-anisaldehyde (0.476 g, 3.50 mmol) in 20 ml of benzene was kept at room temperature for 17 h and then refiuxed for 4 h. The products werepMeOC,H,CH=NMe (0.34 g, 71%) and (EtO),P(O)-O-AiEt, (0.54 g, 76%). Benzophenone. A mixture of IIb, (0.664 g, 2.64 mmol) and benzophenone (0.482 g, 2.64 mmol) in 20 ml of benzene was heated at reflux for 5 days. During the heating, the intensity of Y(C=O) (1680 cm-’ ) band of the ketone decreased slightly and that the 1640 cm-’ [Y(C=N)] b and increased gradually. However, the reaction did not go to completion. The corresponding imino compound, (CsHS )2C=NMe, was obtained in 30% yield on the basis of NMR. NMR (CC14): r 6.93 .s (NCH3), 2.38-3.23 ppm (m, phenyl). Preparation of authentic diethylaluminium diethyl phosphate Diethyl phosphate 1181 (1.60 g, 10.3 mmol) in 20 ml of benzene was added to EtJAi (1.17 g, 10.3 mmol) in 20 ml of benzene. During the addition of the phosphate, evolution of gas was observed. The reaction mixture was heated to 80”. After gas evolution ceased completely, removal of the solvent and distihation under reduced pressure gave diethyldluminium diethyl phosphate, 1.95 g (yield 80% based on Et3 Al used), b-p. 108-114”/0.35 mm. (Found: AI, 10.15; active ethyl groups 1.84. CSH2,,04 Pal calcd.: AI, 11.32%; active ethyl groups 2.00 per mol.) NMR (benzene): T 9.75 q @KHZ, 4H, J 7.5 Hz), 9.03 t (P-OCH2-C&, 6H, J 6.8 Hz), 8.51 t (AICH,CII, ,6H, J 7.5 Hz), 6.17 dq ppm (P-O-C&-CH3, 4H, J(POCH) 7.8 Hz, J (HCCH) 6.8 Hz). IR (benzene: v(P=O) 1280 s and 1262 s, v(P-0-C) 1020-1045 vs cm-‘. Reaction of 1.b with phenyl isocyanate An equimolar mixture of IIb, (0.578 g, 2.30 mmol) and phenyl isocyanate, (0.275 g, 2.30 mmol) in 20 ml of benzene was kept at room temperature for 1 day. However, no reaction occurred. The mixture was heated to 80” and refiuxed for 6 h. Both absorption bands at 2260 cm-’ [Y(NCO)] and 920 cm-’ [v(P-Nj] disappeared completely, while new bands at 2130 cm-’ [v(N=C=N)] , 1690 cm-’ and 1650 cm-’ appeared. Hydrolysis of the mixture gave an oil, 0.455 g, which contained three components, A?-methyl-N’-phenylcarbodiimide (36%), PhNHCONHMe (9%) and the l/l insertion product. (EtO),P(O)NMeCONHPh (55%). (EtO)zP(0)NMeCONHPh; NMR (CCL ): r 8.65 t (P-O-CH2 CH, , J 6.8 Hz), 7.05 d (P-N--CH3, J(PNCH) 6.8 Hz); 5.88 dq (P-O--C&CH3 , J(POCH) 7.5, J(HCCH) 6.8 Hz), 2.38-3.32 (phenyl), -0.10 s ppm (P-m-Mej. IR (CC&): 3230 m [v(NH)] , 1700 s [Y(C=O)~ ,1276 s [z’(P=O)l ,1024 s [v(m)];873 m cm-’ [v(P-N)] .
213
Reaction of Vlb with phenyt isocyanate An equimolar mixture of VI%, (1.21 g, 4.85 mmol) and phenyl isocyanate
(0.578 g, 4.85 mmol) in 20 ml of benzene was kept at room temperature for 60 h. No reaction OCCLUT~~. Heating at reflux for 17 h caused the disappeabnce of v(NCO) (2260 cm-’ ) and appearance of bands at 1630 cm-’ and 1660 cm-’ . Hydrolysis of the mixture as before gave an oil, N-tetramethylphosphorodiamidicN-methyl-IV’-phenylurea, (MeZN),P(0)NMeCONHPh, in 73% yield. IR (benzene): 3160 m [z$NH)], 1690 vs [v(C=O)], 1260 vs [y(P=O)J and 985 vs, 970 vs cm-’ [v(P-O-C)] . NMR (CCI,): T 7.38 d [P-N(CHB)z , 12H, J(PNCH) 9.8 Hz), 7.21 d (P-N-CH3, J(PNCH) 7.5 Hz, 3H), 2.45-3.32 m(pheny1, 5H) and -0.62 s (CONIJPh, IH). (F ound: C, 50.56; H, 6.68; N, 19.75. C12HZ1N402P calcd.: C, 50.70; H, 7.45; N, 19.71%) References 1 2 3 4 5 6 7 8 9 10 11 12 13 14
G.E. Coat-es and R.N. Mukbeiee. J_ Chem. Sot_. (1964) 1295. B. Scbaible and J. Weidlein, J. Organometal. Chem., 35 (1972) Cf. H. Olapinski.
B. Scbaible
and J. Weidlein.
J. Organometal.
Chem..
43 (1972) 107. 176. W.S. Wadsworth. Jr. and W.D. Rmmons. J. Amer. Chem. Sot-. 84 (1962) 1316. W.S. Wadsworth. Jr- and W-D- Bmmons. J. Org. Chem.. 29 (1964) 2816. H. Imaeda. T. Hirabayashi. K. Itoh and Y- I&ii. Organometal. Chem. Synth.. 1 (1970/1971) 115. T. Sakakibara. T. Hirabayashi and Y. Ishii. J. Organometal. Chem., 46 (1972) 231. F. Artbertons. H. Opensbaw and A.R. Todd. J. Chem. Sot., (1945) 660. G. Sigh and H. Zimmer. Organometal. Chem. Rev.. 2 (1967) 279. H.R. Allcock. Cbem. Rev.. 72 (1972) 315. O.J. Scherer and G. Scheider. Chem. Ber.. 101 (1968) 4184. O.J. Scherer and P. Kbxsmann, 2. Anorg. Al&em. Chem.. 370 (1969) 171. K. Sasse, in Houben-Weyl. Methoden dex Organischen Chemie, Bd. 1212. Georg Tbieme Verlag, Stuttsart, 1964. R. Appd and J. Kohnke. Cbem. Ber.. 104 (1971) 3875. H- Steller and J. Premen. Chem. Ber., 106 (1973) 2523. N. Bortnick, L.S. Luskin, M.D. Hurwitz and A.W. Ryf,i.na_ J. Amer. Chem. Sot.. 78 (1956) 4358. T. Mukaiyama end T. Fujisawa. Bull. Chem. Sot. Japan. 34 (1961) 812.
J. Weidlein and B. Schaible, Z. Anorg. Al&em. Cbem., 386 (1971)
15 16 17 18 19 H.McCombie. B. Saunders end G. Stacey. J- Chem- Sot.. (1945) 921. 20 R.L. Arceneaux. J-G. @kick. Jr.. E.K. Leonard and J.D. Reid, J. Ors Chem.,
24 (1959)
1419.
-..
:
Journal of Organomeiallic Chtimidy, 76 (1934) 203-&3 Q Else&r Sequoia S.A., Lausanne - Printed in The Netherlands
i’ : .~....
..
: . .:
PREPARATION AND IhNOCARBONYLATION REACTIONS OF ORGANOALUMCHELATE COMPOUNDS CONTAINING Pv-N&k-Al BONDS
KOkX3I
URATA,
KENJI ITOH and YOSHIO ISHII
Department of Synthetic Ckemistry, Faculty oy Engineering, Nagoya Univeisity. -ChikuSa. Nagoya, 464 (Japan) (ReceivedFebruary
ZOth, 1974)
:
New organoaluminium compounds containing Pv -NMe-Al bonds, diethylaluminium dialkyl N-methylphosphoramidate, (_R0)2P(0)NMeAlEt,, and tetraalkylphosphorodiamidic N-methylamide, ( R2N)z P(O)NMeAl& , were prepared. Cryoscopic -measurements showed these compounds to be dimeric by intermolecular coordination. The introduction of bulky substituents on the phosphorus atom decreased the degree of association. The coordination of oxygen atom of P=O bonds to organoaluminium moiety was indicated by spectroscopic evidence. In the reactions of (RO)zP(0)-NMe-AlEt2 with aromatic aldehydes or phenyl isocyanate, the corresponding irnino compounds were obtained by an addition-elimination process.
Introduction Some Group III organometallic chelate compounds of phosphinic acid derivatives have been studied [l-4]. In particular, organoaluminium, gallium and indium derivatives of alkyl (or aryl) phosphinic acids, RpP(0)--O-MR: , were shown to exhibit strong intermolecular interaction between R:M (M = Al, Ga and In) moieties and the oxygen atom of phosphinyl group. However, little was known about the structural or chemical behavior of organoaluminium chelates of phosphoramidates X2 P(0)-NMe-J.lE& . It is well known that the specific affinity of phosphorus to oxygen atom is the driving force of Wittig type reactions. In this context, the dialkyl N-alkylphosphoramidate anion was recently reported to act as an iminocarbonylating agent [5, S] _ In pseudo-Wittig type reactions of organoaluminium compounds, a facile formation of stable Al-O bonds is considered to be the key step. For example, thiocarbonylation reactions with (Et2 Al)* S [ 71 and iminocarbonyla.. tion with MezAl-NMe-&Me, [S] may be included in this category. Since both
:20x]
-..
&ganoalumlm ’ ‘um and organophosphorus groups show strong affinity to oxygen atoms, formation of a stable Al-O-? bond is expected in some-addition-&mi: . : n&ion reactio& Prom the above point of view, we describe here the preparation of diethyl.ahminhm derivatives of dialkyl N-methylphosphoramidates, (RO),P(O)-NMeALE& (Ib-Vb), and tetraalkylphosphorodiamidic N-methylamides (Rz N)Z .P(O)-NM+&& (VIb, VIIb), together with the iminocarbonylation by means of diethylaluminium dialkyl N-methylphosphoramidates. Results and dkussion Preparation of compounds X,P(O)-NMe-AlEt, (X = RO and R,N) (Ib-VIIb) Dialkyl N-methylphosphoramidate9 (Ia-Va), obtained by the reaction of dialkyl hydrogen phosphites with Ccl4 and MeNI& 19 1, reacted with triethylaluminium~to give the corresponding diethylalunki-um derivatives (Ib-Vb) in 6O-80% yield based on E&Al used (eqn. 1). benzene
(RO)zP(0)NHMe
(RO),P(O)NMeAlEt,
+ Et3Al -
80°C
(Ia-_Va)
+ C2Hs
(1)
W-Vb)
(I, R-s Me; II, Et; III, i-Pr; IV, i-Bu; V, i-Am) Tetraalkylphosphorodiamidic N-methylamide (Via, VIIa) gave the car-responding aluminium compounds (VIb, VIIb) according to eqn. 2. Yields, b.p.‘s and analyses of Ib-WIb are summarized in Table 1. (R,N),P(O)kHMe 07%
+ Et&l F
(R,N)AO)NMeAlEt, (VW
VBa)
+ CJG
(2)
wb)
(VI, R = Me; VII, Et) These compounds (especially Ib-Vb) were thermally stable (up to ca. 200”) and distillable under reduced pressure. Cryoscopic molecular weight determinations showed that these compounds were dimeric in benzene by intermolecular coordination in the case of less bulky substituents (RO = MeO, Et0 or Me?N). “\
7’
*-*‘\
x\P//
/Me
N
x’
I
I PiX
Me/“\
//‘X
AI-O ‘EC
(X =-
w 4
RO
‘ET and
_ R,N)
*
2
I Me
Me0
Et0
i-k0
i*BuO
i-Am0
MezN
Et2N
Ib
IIb
IIIb
IVb
Vb
VIb
VIIb
(0.01) (0.26) (0.13)
136-142 140-146 160-166 146-162 166-166 110-120 liquid
72
78
71
70
60
60
84
(0.3)
(0.6)
(0.28)
?&nnl,
Yield (%) 37.36 (37.67) 43.17 (43.03) 47.13 (47.31) 60.97 (60.80) 63.90 (63.72) 43.63 (43.37) 60.91 (61.13)
C
Com-
Et0 i-pro i.BuO i-Am0 Me2N Et2N
118, bb IIIa, IVa, b Va,b Via, b VIIa, b
‘In 2% benzene solution.
Me0
X
Ie, b
pound
1216,118O 1216,1176 1216,118G 1216.1190 1190,1166 1200,1170
1220,119o
1260,1243 1264,1236 1260,1236 1240,123O 1260,1236, 1216,119O 1220,1206
uB(p=o) oi Ib-VIIb
uA(p=o) of In-VIIa
-39, -36, -26, -36, -26, -20,
-66 -6C -46 -46 -36 -36
-63
Au(P=0) =vB(p-C) uA(P=0) -40,
11.92 (12.10) 10,90 (10.74) 9.63 ( 9.67) 8,66 ( 8,79! 8.76 ( 8.06) 11.26 (10.84) 9.34 ( 8.84)
Al
870 896 890 886 846 860
880
uA(p-N) Ia-VIIa
of
AND X2P(0)NMeAlEt2(Ib-VIIb)
8.67 ( 8.68) 9,27 ( Z) ( 9:74) 9.92 (10.17) 10.33 (10.62) 10,Ol (10.11) 10.66 (10.89)
H
Analysts found (colcd,) (%)
DATA OF THE COMPOUNDS X2P(O)NMeAIEt2
DIFFERENCES IN u(pzC) AND V(p-NJ BETWEEN XZP(O)NHMe (Ia-VIIa)
TABLE 2
X
Compound
PHYSICAL AND ANALYTICAL
TABLE 1
o
920 933 940 940 906 396
940
vB(P-N) of Ib-VIIb
(cm”)
470 (306)
466 (336) 416 (336) 474 (249)
390 (307)
406 (279)
466 (223) 381 (223) 406 (261)
la64
1.39 1.24 1.91
1.27
1.46
2.06 1.71 1.62
3.13
2.87 1.66 3.61
2,96
2.76
3.70 2.68 2.76
Concentration (wt %)
3”: 60 66 60 46
60
Au P-N) =v$ (P-N) uA(P-N)
M.W.(cnlcd. De&! of m monomer) association
. . 207. The introduction of bulky groups (RO = i-Pro, i-BuO, i-Am0 or EtlN) on. the phosphorus atom decreased the degree’of association. The-&& effect of the substituent on phosphorus is~exphtinedin tern% of tbe~dissociatibe.equilibrium between the intermole&larly cciord~ated dimer and the irkramoleculkrly coordinated moncmer (eqn. 3). In this connection, the preparation of the di-tert-butyl N-methylphosphorami~ date derivative, (t-BuO),P(O)NMeAlEt, , failed. Evolution of excess ethane occurred (ca. 1.5 - 1.7 times the theoretical value). ._ IR and NMR spectra of Ib-VIIb As shown in Table 2, the stretching frequency of P-0 bond in Ib-VIIb, showed values lower than in the original dialkyl N-methylphosphoramidates Ia-Va or in the tetraaikylphosphorodiamidic N-methylamides (Via, VIIa) (Av(P=O) ca. -20 to -60 cm-’ ), which suggests the coordination of oxygen atom of P=O bonds to diethylaluminium group. The stretching frequency of the P-N bond (850 to 950 cm-’ ) [lo] shifted to higher values on introduction of the diethylaluminium moiety [AZ@?--N) ca. 40 to 60 cm-’ ] . These two shifts’ of P=O (lower) and P-N (higher) stretching frequencies can be explained in terms of structure B or D, in which (p-d)n bonding between phosphorus and. nitrogen atoms is involved. When electronegative groups (RO or RpN) are linked to the phosphorus atom, it is reported that the contraction of 3d .orbitals increases their availability to (p-d)~ bonding [ll].
\/
O-AI
\/
/pI AN\Al-0 /\
‘NH I
P'
//\
(A)
\//Ok/
/p\N,A’L (Cl
_
_
\p/o\A,/ ’
\\,r
’
(0)
The NMR spectroscopic results are summarized in Table 3. Changes of coupling constant, J(PNCH), by introduction of the diethylaluminium group, provide important information about the P-N bond. Dialkyl N-methylphosphoramidates or tetraalkylphosphorodiamidic N-methylamides X*P(O)NHMe (X = RO, R2N) (IaLVIIa) showed J(PNCH) values around 10 to 12 Hz. These values increased to 16 to 17 Hz for the organoaluminium homologs XiP(0)NMeAIEt, (Ib-VIIb) as shown in Table~3. The increase of J(PNCH) by diethylahuninium group reflects the contribution of Cp?i)n interaction between phosphorus and
T,@LE4
. ..
RE&TION
I.:
:-
PRODUCTS
ceriJoll;i ixx&Jd&&’ -_ ._ . .. -.
..,
.1:
OF Ib. IIb WITH-CARBONYL
Pi&& (% yield)
-_
,
Et212
::
PhCIi=O
Ph-N=C=O
Ph-N=C=N-Me Ph-NIXONH-Me (RO)2P(O)NMeCONHPh Ph2ONMe
=
Ph2C=p. a Demekllated
with dilute hydrochloric
70. 86
74
_;;
P-MeOCg&CH=NMe
gMeO&jH&H~O
;
-.
[(EtO)~P
C(MeO)~P(O)IiMe.AlEt212
.-
:
._
COMPOUNDS-
._
71 :z 9 55
:: 40 0
30
acid and yield wzs obtained
by NMR
analysis.
nitrogen atoms (cf. Pv=N-CH;J(PNCH) 20 to 30 Hz) C-12,133. The change in coupling constants is also consistent with the strong interaction of oxygen with the aluminium atom.
Iminocarbonylation and ketone
reactions of (R0)2P(0)NMeAiEt2
with aromatic aldehydes
.
When diethylaluminium dimethyl (and diethyl) N-methylphosphoramidate (Ib and Ilb), reacted with aromatic aldehydes, the corresponding N-arylidenemethylamines were obtained in 70 to 80% yield along with diethylaluminium dialkyl phosphate (80 to 90% yield) (eqn. 4) as summarized in Table 4. The reaction between IIb and benzophenone was extremely slow even at 80”, probably due to a steric effect.
R”\p/o\*,/” RO’‘N/ ‘Et I +
Me
R”\p/o\ i’ Ad&L
AC\tz-O / H
(R =
Me,
Et)
Reactions of X2P(0)NMeAlEt, phenyl isocyanate
I-
‘i”Et
RO'I
,,/pt/O AA
““\ //“\ iEt Ro/p\o/A’\Et
Elimin.
(4)
[X = Me0 (Ib), Et0 (IIb) and Me2N (VIb) with
Phenyl isocyanate showed remarkable differences in reactivity which depended upon the degree of association’of the starting duminium compound. The reaction of dimeric compounds (R0)2P(0)NMeAlEt2 (Ib, Ilb) (R = Me, Et); with phenyl ispcyanate did.not proceed at room temperature; .On heating up to 800., a subsequent,elimination reaction occurred immediately. In the case of.Hb,- three products were present: methylphenylcarbodiimide (36%; elimina-
211 determined cryoscopically. Infrared spectra were recorded with a Japan Spectroscopic Co. Model IR-S and NMR.spectra were recorded with a Japan Electron Optics Co. Model C-6OHL using TMS as an internal standard. Elemental analyses of organoel uminium compounds were carried out by Alfred Bemhardt Microanal. Lab. in West Germany.
Preparation of diethyialuminium diaikyl N-methylphosphoramidates (Ib-Vb) and tetraalkylphqsphorodiaqzidic N-methylamides (Vlb, VIIb) The preparation of diethylal uminium dimethyl N-methylphosphoramidate (Ib) is described as an example; IIb-VIIb were prepared analogously. Dimethyl N-methylphosphoramidate (Ia )(2.44 g, 17.5 mmol) in 20 ml of benzene was added dropwise to EtjAl (1.99 g, 17.5 mmol) in 20ml benzene at room temperature. During the addition of Ia evolution of gas was observed. The reaction mixture was heated up to 8@ and refluxed for 1 h. After the gas evolution had ceased completely, the solvent was removed, and the product was distilled under reduced pressure to give liquid Ib, b.p. 135-142” /0.28 mm. Yield 2.81 g (72%) based on Etg Al used. See Tables 1-3 for data.
Reaction of Ib with aldehydes Benzaldehyde. Benzaldehyde (0.416 g, 3.92 mmol) in 10 ml of benzene was added dropwise to Ib (0.871 g, 3.92 mmol) in 10 ml of benzene at room temperature. After 15 h both absorption bands at 1700 cm-’ [v(C=O)] and 940 cm-’ [v(P-N)] had not vanished. The reaction mixture was heated to reflux. The two above-mentioned absorption bands completely disappeared, and the appearance of new band at 1650 cm-’ [v(C=N)] was noted. Removal of the solvent and distillation under reduced pressure gave N-benzylidenemethylamine, b-p. 75-80”/20 mm (lit. b.p. 600/8 mm) [15], 0.35 g (yield 74%) and a residue, 0.81 g (yield 98%) of diethylaluminium dimethyl phosphate [ (MeO)2P(0)-O--AlEt, 1. N-benzylidenemethylam-he showed the same infrared and NMR spectra as the authentic compound [I63 . p-Anisaldehyde. In an analogous manner, reaction of lb, (0.645 g, 2.90 mmol) in 10 ml benzene and p-anisaldehyde (0.395 g, 2.90 mmol) in 10 ml of benzene gave by distillation under reduced pressure N-p-methoxybenzylidenemethylamine, b.p. 63-65°/0.08 mm, 0.30 g (yield 70%). Spectroscopic and physical data of the isolated product were identical with those of an authentic sample. A residue, 0.538 g (yield 88% as diethylaluminium dimethyl phosphate), was also obtained.
Reaction
of Ib with phenyl
isocyanate
Phenyl isocyanate (0.338 g, 2.83 mmol) in 10 ml of benzene was .added drop--=t--wise to ib, (OhL9 g, 2.83 mmoij k 10 mi of benzene at room temperahqe. After 16 h, both absorption bands at 2260 cm-’ [Y(NCO)] and 940 cm-’ [v(PN)] remained. The reaction mixture was heated to 80” and refluxed for 6 h. Both of the above two absorption bands disappeared completely and new bands at 2130 cm-’ [v(NCN)] , ch~acteristic of N-methyl-N’-phenylcazbodiimide, 1695 and 1650 cm-’ appeared. After hydrolysis of the mi&ure with dilute hydrochloric acid the product was extmcted with benzene. The benzene solution was dried with anhydrous NaZSO4 ; removal of the solvent gave 0.511-g. of an oil. NMR analysis of this oil showed the presence of N-methyl-N’-phenylcarbodiimide (60%) and
-212
PhNHCONHMe (40%). The authentic sample of carbodiimide was prepared according to ref. 17. Reaction of IIb with aldehydes and ketones Benzaldehyde; When a mixture of benzaldehyde (0.250 g, 2.32 mmol) and IIb, (0.584 g, 2.32 mmol) in 20 ml of benzene was kept at room temperature for 24 h and heated at reflux for 12 h, absorption bands at 1700 cm-’ [Y(C=O)] and 920 cm-’ [v(PN) J disappeared, and a new absorption band at 1650 cm-’ [v(C=N)] appeared. The products were PhCH=NMe (0.19 g, 70%) and (EtO)* P(Oj-o-AIEt2 (0.51 g, 92%). p-Anisaldehyde. In an analogous manner a mixture of IIb, (d.871 g, 3.50 mmolj and p-anisaldehyde (0.476 g, 3.50 mmol) in 20 ml of benzene was kept at room temperature for 17 h and then refiuxed for 4 h. The products werepMeOC,H,CH=NMe (0.34 g, 71%) and (EtO),P(O)-O-AiEt, (0.54 g, 76%). Benzophenone. A mixture of IIb, (0.664 g, 2.64 mmol) and benzophenone (0.482 g, 2.64 mmol) in 20 ml of benzene was heated at reflux for 5 days. During the heating, the intensity of Y(C=O) (1680 cm-’ ) band of the ketone decreased slightly and that the 1640 cm-’ [Y(C=N)] b and increased gradually. However, the reaction did not go to completion. The corresponding imino compound, (CsHS )2C=NMe, was obtained in 30% yield on the basis of NMR. NMR (CC14): r 6.93 .s (NCH3), 2.38-3.23 ppm (m, phenyl). Preparation of authentic diethylaluminium diethyl phosphate Diethyl phosphate 1181 (1.60 g, 10.3 mmol) in 20 ml of benzene was added to EtJAi (1.17 g, 10.3 mmol) in 20 ml of benzene. During the addition of the phosphate, evolution of gas was observed. The reaction mixture was heated to 80”. After gas evolution ceased completely, removal of the solvent and distihation under reduced pressure gave diethyldluminium diethyl phosphate, 1.95 g (yield 80% based on Et3 Al used), b-p. 108-114”/0.35 mm. (Found: AI, 10.15; active ethyl groups 1.84. CSH2,,04 Pal calcd.: AI, 11.32%; active ethyl groups 2.00 per mol.) NMR (benzene): T 9.75 q @KHZ, 4H, J 7.5 Hz), 9.03 t (P-OCH2-C&, 6H, J 6.8 Hz), 8.51 t (AICH,CII, ,6H, J 7.5 Hz), 6.17 dq ppm (P-O-C&-CH3, 4H, J(POCH) 7.8 Hz, J (HCCH) 6.8 Hz). IR (benzene: v(P=O) 1280 s and 1262 s, v(P-0-C) 1020-1045 vs cm-‘. Reaction of 1.b with phenyl isocyanate An equimolar mixture of IIb, (0.578 g, 2.30 mmol) and phenyl isocyanate, (0.275 g, 2.30 mmol) in 20 ml of benzene was kept at room temperature for 1 day. However, no reaction occurred. The mixture was heated to 80” and refiuxed for 6 h. Both absorption bands at 2260 cm-’ [Y(NCO)] and 920 cm-’ [v(P-Nj] disappeared completely, while new bands at 2130 cm-’ [v(N=C=N)] , 1690 cm-’ and 1650 cm-’ appeared. Hydrolysis of the mixture gave an oil, 0.455 g, which contained three components, A?-methyl-N’-phenylcarbodiimide (36%), PhNHCONHMe (9%) and the l/l insertion product. (EtO),P(O)NMeCONHPh (55%). (EtO)zP(0)NMeCONHPh; NMR (CCL ): r 8.65 t (P-O-CH2 CH, , J 6.8 Hz), 7.05 d (P-N--CH3, J(PNCH) 6.8 Hz); 5.88 dq (P-O--C&CH3 , J(POCH) 7.5, J(HCCH) 6.8 Hz), 2.38-3.32 (phenyl), -0.10 s ppm (P-m-Mej. IR (CC&): 3230 m [v(NH)] , 1700 s [Y(C=O)~ ,1276 s [z’(P=O)l ,1024 s [v(m)];873 m cm-’ [v(P-N)] .
213
Reaction of Vlb with phenyt isocyanate An equimolar mixture of VI%, (1.21 g, 4.85 mmol) and phenyl isocyanate
(0.578 g, 4.85 mmol) in 20 ml of benzene was kept at room temperature for 60 h. No reaction OCCLUT~~. Heating at reflux for 17 h caused the disappeabnce of v(NCO) (2260 cm-’ ) and appearance of bands at 1630 cm-’ and 1660 cm-’ . Hydrolysis of the mixture as before gave an oil, N-tetramethylphosphorodiamidicN-methyl-IV’-phenylurea, (MeZN),P(0)NMeCONHPh, in 73% yield. IR (benzene): 3160 m [z$NH)], 1690 vs [v(C=O)], 1260 vs [y(P=O)J and 985 vs, 970 vs cm-’ [v(P-O-C)] . NMR (CCI,): T 7.38 d [P-N(CHB)z , 12H, J(PNCH) 9.8 Hz), 7.21 d (P-N-CH3, J(PNCH) 7.5 Hz, 3H), 2.45-3.32 m(pheny1, 5H) and -0.62 s (CONIJPh, IH). (F ound: C, 50.56; H, 6.68; N, 19.75. C12HZ1N402P calcd.: C, 50.70; H, 7.45; N, 19.71%) References 1 2 3 4 5 6 7 8 9 10 11 12 13 14
G.E. Coat-es and R.N. Mukbeiee. J_ Chem. Sot_. (1964) 1295. B. Scbaible and J. Weidlein, J. Organometal. Chem., 35 (1972) Cf. H. Olapinski.
B. Scbaible
and J. Weidlein.
J. Organometal.
Chem..
43 (1972) 107. 176. W.S. Wadsworth. Jr. and W.D. Rmmons. J. Amer. Chem. Sot-. 84 (1962) 1316. W.S. Wadsworth. Jr- and W-D- Bmmons. J. Org. Chem.. 29 (1964) 2816. H. Imaeda. T. Hirabayashi. K. Itoh and Y- I&ii. Organometal. Chem. Synth.. 1 (1970/1971) 115. T. Sakakibara. T. Hirabayashi and Y. Ishii. J. Organometal. Chem., 46 (1972) 231. F. Artbertons. H. Opensbaw and A.R. Todd. J. Chem. Sot., (1945) 660. G. Sigh and H. Zimmer. Organometal. Chem. Rev.. 2 (1967) 279. H.R. Allcock. Cbem. Rev.. 72 (1972) 315. O.J. Scherer and G. Scheider. Chem. Ber.. 101 (1968) 4184. O.J. Scherer and P. Kbxsmann, 2. Anorg. Al&em. Chem.. 370 (1969) 171. K. Sasse, in Houben-Weyl. Methoden dex Organischen Chemie, Bd. 1212. Georg Tbieme Verlag, Stuttsart, 1964. R. Appd and J. Kohnke. Cbem. Ber.. 104 (1971) 3875. H- Steller and J. Premen. Chem. Ber., 106 (1973) 2523. N. Bortnick, L.S. Luskin, M.D. Hurwitz and A.W. Ryf,i.na_ J. Amer. Chem. Sot.. 78 (1956) 4358. T. Mukaiyama end T. Fujisawa. Bull. Chem. Sot. Japan. 34 (1961) 812.
J. Weidlein and B. Schaible, Z. Anorg. Al&em. Cbem., 386 (1971)
15 16 17 18 19 H.McCombie. B. Saunders end G. Stacey. J- Chem- Sot.. (1945) 921. 20 R.L. Arceneaux. J-G. @kick. Jr.. E.K. Leonard and J.D. Reid, J. Ors Chem.,
24 (1959)
1419.