Protonation at the Aromatic Ring vs. at the Carbonyl Group of

May 30, 1995 - the carbonyl group but also atthe aromatic ring, which leads to the formation of a new class of lanthanide aryloxide, mixed aryloxide/a...
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Organometallics 1995,14, 5382-5392

5382

Protonation at the Aromatic Ring us at the Carbonyl Group of Lanthanide-Diary1 Ketone Dianion Species by Aryl Alcohols. Formation, Structural Characterization, and Reactivity of Lanthanide Aryloxide, Mixed Aryloxide/Alkoxide,and AryloxideIEnolate Complexes Takashi Yoshimura, Zhaomin Hou,* and Yasuo Wakatsuki* The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako, Saitama 351 -01, Japan Received May 30, 1995@ Reaction of the ytterbium-benzophenone dianion complex T Y ~ ~ - T ~ , T ~ - O C P ~ Z ) ( H M P A ) ~ I ~ (l),which was formed by reaction of Yb metal with benzophenone in THFMMPA, with 2,6di-tert-butyl-4-methylphenol, yielded the ytterbium(I1) aryloxide complex Yb(OAr)2(HMPA)2 (2, Ar = C6H2-tBu2-2,6-Me-4)as a major product (80%)and the ytterbium(II1) enolate complex

-

Yb(OC(=CCH=CHCH&H=CH)Ph)z(OAr)(HMPA)2 (3,Ar = C&htBu2-2,6-Me-4) as a minor one (ea. 5% yield). In contrast, the similar reaction of samarium benzophenone dianion or C6H3-%u2-2,6) gave the samarium(II1) enolate species with ArOH (Ar = C&I~-~Buz-2,6-Me-4 complex Sm(OC(=CCH=CHCH2CH=CH)Ph)z(OAr)(HMPA)z (4a, Ar = C6H2-tBu~-2,6-Me-4, 56%) as a major product, while samarium(I1) aryloxide 60%; 4b, Ar = C~H3-~Bu2-2,6, analogous to 2 was not obtained. When ArOD (Ar= C6H~-~Bu~-2,6-Me-4) was used instead I

I

of ArOH, the deuterated enolate Sm(OC(=CCH=CHCHDCH=CH)Ph)z(OAr)(HMPA)2(4c, Ar = C6Hz-%u2-2,6-Me-4)was formed. In the reaction with 2,6-tBu~-4-Me-C6H~OH, a mixed aryloxide/alkoxide complex Sm(OCHPhz)(OAr)2(HMPA)z(5a,Ar = CsH~-~Bu2-2,6-Me-4) was also isolated in ca. 2% yield. When samarium fluorenone dianion species was allowed to react with 2 , 6 - t B u ~ - C & , 0 Hthe , fluorenoxy analogue of Sa, Sm(fluorenoxy)(OAr)2(HMPA)2 (6, Ar = C~H3-~Bu2-2,6, 64%), was obtained as the only isolable product. Upon heating at 180 “C in toluene, 4a,b isomerized into 7a,b Sm(OCHPh2)2(0ArXHMPA)2(7a, Ar = CsH2tBu2-2,6,-Me-4;7b,Ar = C,&-tBu~-2,6). Deuterium labeled experiments indicated that this isomerization was an intramolecular one step 1,5-hydrogen shift process. Reaction of 4a and 7a with 2,6-tBu2-C6H30Hyielded the aryloxy exchange products 4b and 7b,respectively, while the reaction of 7a with 2,6-Me&H30H gave the diphenylmethoxy substitution product Sm(OAr)(OAr”)2(HMPA)2(8, Ar = C6H.~-~Bu2-2,6,-Me-4; Ar” = csH3-Me2-2,6). The mechanisms of these reactions are discussed. X-ray crystallographic studies reveal that 3, 4a, and 7b are isostructural, and so are 5a and 6. The central metal ions in these complexes are all five-coordinated in a trigonal bipyramid form (highly distorted in the case of 5a and 6) with two HMPA ligands at the apical and three anionic oxygen ligands at the equatorial positions. Introduction The formation of ketone dianions via two electronreduction of diaryl ketones by alkali metals was first reported in 1911.l It is now known that other reducing metals such as low-valent titanium species2 and lanthanide metals3 are also able to reduce diaryl ketones into the corresponding dianions. Since these dianionic @Abstract published in Aduance ACS Abstracts, October 1, 1995. (1)For the formation of alkali metal-diary1 ketone dianions and their use in organic synthesis, see: (a) Schlenk, W.; Weichel, T. Ber. 1911,44,1182.(b) Schlubach, H. Ibid. 1915,48,12.( c ) Wooster, C. B. J . Am. Chem. SOC.1928,50, 1388.(d) Bachmann, W. E. Ibid. 1933, 55,1179.(e) Hamrick, P. J., Jr.; Hauser, C. R. Ibid. 1959,81,493.(0 Selman, S.;Easthan, J. F. J.Org. Chem. 1965,30,3804. (g) Anderson, E. L.; Casey, J. E., J r . Ibid. 1965,30,3959. (h) Murphy, W. S.; Buckley, D. J. Tetrahedron Lett. 1969,2975.(i) Huffman, J.W. in Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds; Pergamon: New York, 1991;Vol. 8,Chapter 1.4.(i) Robertson, G. M. Ibid. Trost, B. M., Fleming, I., Eds; Vol. 3,Chapter 2.6.

species are extremely sensitive to air and moisture, their isolation is difficult and they are usually used in-situ for next reactions. Their reactivities are therefore judged mainly based on the final hydrolysis products. Although the final products are dependent on the nature of the metals in some cases (e.g., in the case of titanium, deoxygenation reaction often occurs), the results presented so far in the literature have shown that all these ketone dianion species show a similar reactivity: when (2)(a)McMurry, J. E.; Krepiski, L. R. J. Org. Chem. 1976,41,3929. (b) McMurry, J. E.; Fleming, M. P.; Kees, K. L.; Krepiski, L. R. J.Org. Chem. 1978,43, 3255.( c ) Pons, J. M.; Santelli, M. Tetrahedron Lett. 1982,23,4937. (d) McMuny, J.E. Acc. Chem. Res. 1983,16,405.1974, 7,281.Chem. Reu. 1989,89, 1513. (3)(a) Hou, Z.;Takamine, K.; Fujiwara, Y.; Taniguchi, H. Chem. Lett. 1987,2061. (b) Hou, Z.;Takamine, K.; Aoki, 0.; Shiraishi, H.; Fujiwara, Y.; Taniguchi, H. J . Chem. SOC.,Chem. Commun. 1988,668. J . Org. Chem. 1988,53,6077.( c ) Olivier, H.; Chauvin, Y.; Saussine, L. Tetrahedron 1989,45, 165.

0276-733319512314-5382$09.00/0 0 1995 American Chemical Society

Protonation of Lanthanide-Diary1 Ketone Dianion Species

6

7

Figure 1. Phenyl part of the lH NMR spectrum of 1. they are mixed with electrophiles, reactions always take place a t the carbonyl carbon to give the corresponding cross-coupling products (eq l).1-3

E = Electrophiles

1 1

0-

I

Ar-C-

I

11)

E

21 H+

Ar

'

OH

I

Ar-C-E

I Ar

(1)

1

Our recent isolation of the ytterbium(I1)-benzophenone dianion complex TYbOl-y1,y2-OCPh2)(HMPA)~I~ (1) from the reaction of Yb metal with benzophenone in THF/HMPA provided the first structurally characterizable metal-ketone dianion complex (eq 2h4 A n X-ray analysis has revealed that the anionic carbonyl carbon atom in 1 is still in a sp2-hybrid state, which therefore allows a good conjugation of the negative charges with the phenyl rings. The lH NMR spectrum of 1 in THFdB shows that the signals for the phenyl protons are greatly upfield shifted to as high as 6 5.63-7.04 (Figure l), demonstrating that the negative charges of this ketone dianion are highly delocalized into the phenyl rings, especially t o the para-positions (65.63) (eq 3). 0I

0I

Organometallics, Vol. 14, No. 11, 1995 5383 ketone dianion species with 2,6-di-tert-butylphenols. We have found that these reactions take place not only a t the carbonyl group but also at the aromatic ring, which leads to the formation of a new class of lanthanide aryloxide, mixed aryloxide/alkoxide,and aryloxide/enolate complexes, with the selectivity being dependent on the nature of both metals and ketones. The structures and reactivities of these newly formed lanthanide complexes are also described. A portion of this work has been previously c ~ m m u n i c a t e d . ~ ~ > ~

Results and Discussion Reaction of the Ytterbium(I1)-Benzophenone Dianion Complex CYb(lr-11,12-OCPh2)(HMPA)21~ (1) with 2,6-Di-tert-butyl-4-methylphenol. Our investigation on the reaction of complex 1 with an alcohol was initially promoted by both the novel structural features of 1 and our interests in low-valent lanthanide alkoxide (aryloxide) complexes.6 Since both an Yb-C bond and an Yb-0 ionic bond are present for each Yb(11)ion in complex 1,we thought that if the Yb-C bond could be selectively protonated during alcoholysis, formation of an ytterbium(I1) complex bearing mixed alkoxide ligands might be possible. The reaction of 1 with 2 equiv of tertiary butyl alcohol was attempted first, but no isolable product was obtained. However, the use of a bulky aryl alcohol such as 2,6-di-tert-butyl4-methylphenol (ArOH) enabled us to isolate a crystalline product. Addition of 2 equiv of ArOH in THF to a purple solution of 1 generated gradually a light brown solution in a few hours. Evaporation of THF and addition of diethyl ether precipitated fine orange crystals which after recrystallization from THF yielded orange-red blocks of 2 (eq 4). Contrary to our expecta-

1 ?Ar

2

80%

3 5%

Ar = CsH2-'B~2-2,6-Me-4

These data indicate that a new type of reaction, i.e., the reaction a t the aromatic ring, might also be achievable. In this paper we report a detailed study on the protonation reactions of samarium- and ytterbium-diary1 (4) (a) Hou, Z.; Yamazaki, H.; Kobayashi, K.; Fujiwara, Y.;Tanigu-

chi, H. J . Chem. Soc., Chem. Commun. 1992, 722. (b) Hou, Z.; Yamazaki, H.; Fujiwara, Y.; Taniguchi, H. Organometallics 1992,11, 2711.

tion, lH NMR spectroscopic study suggested that 2 was the ytterbium(I1)aryloxide Yb(OAr)dHMPA)z,a product resulted from the alcoholysis of both the Yb-C bond and the Yb-0 bond of 1. This compound could be isolated (5) Hou, 2.; Yoshimura, T.; Wakatsuki, Y. J . Am. Chem. SOC.1994, 116, 11169. (6)(a) Hou, Z.; Miyano, T.; Yamazaki, H.; Wakatsuki, Y. J . Am. Chem. SOC.1995,117, 4421. (b) Hou, Z.;Wakatsuki, Y. Yuki &sei Kagaku Kyokaishi 1996,53,No.10,in press.

Yoshimura et al.

5384 Organometallics, Vol. 14,No. 11, 1995 9 4

Pic11

1

Figure Table 1. Selected Bond Lengths (A) and Angles (den) of 2 2.179(8) 1.480(7) 1.46(1) 1.41(2) 1.40(2) 1.53(2) 1.52(2) 1.55(2) 1.57(2) 1.50(3) 122.1(3) 103.0(3) 97.0(3) 171.3(6)

2.299(7) 1.30(2) 1.46(2) 1.52(2) 1.392) 1.37(2) 1.54(3) 1.56(2) 1.55(2) 110.3(3) 103.0(3) 122.1(5) 163.9(7)

in 80% yield when 4 equiv of ArOH was used. Reflecting the diamagnetic property of the divalent ytterbium species, the 'H NMR spectrum of 2 in CsDs showed wellresolved signals a t 6 7.33 (8,C6H2), 2.53 (8, Me), and 1.85 (s, tBu) for the ArO parts and 6 2.15 (d, JP-H= 9.3 Hz) for the HMPA ligands. A n X-ray analysis reveals that the central Yb atom in 2 is sitting on a two-fold axis and is bonded by two ArO and two HMPA ligands in a distorted tetrahedral form (Figure 2 and Table 1). The Yb-O(HMPA) bond distance (2.298(7) 8)in 2 is comparable with those found in 1 (av 2.28(2)A)4 and is also comparable with those found in the six-coordinated Yb(I1)complexes lYb(HMPA)dTHF)2112(av 2.357(6) Ai)7 and cis-YbOl,q1-OCMo(C0)2Cp)2(HMPA)4 (av 2.33(1)A),* when the influence of coordination number is taken into account.9 The Yb-OAr bonds (2.179(9) A) in 2 are slightly longer than those found in another fourcoordinated ytterbium(I1) aryloxide complex (ArOhYb(av 2.137(10) &,lo (THFl2 (Ar = CsH~-~Bu2-2,6-Me-4) probably due to the electronic and steric influence of the HMPA l i g a n d ~ . ~ J l During the isolation of 2, a few yellow needle-like crystals of 3 precipitated from the diethyl ether mother (7) Hou, Z.; Wakatsuki, Y.

J. Chem. SOC., Chem. Commun. 1994,

1205. (8)Hou, Z.;Aida, K.; Takagi, Y.; Wakatsuki, Y. J. Organomet. Chem. 1994,473, 101. (9) Shannon, R. D. Acta Crystallogr., Sect. 32A 1976,751. (10)Deacon, G.B.; Hitchcock, P. B.; Holmes, S. A.; Lappert, M. F.; Mackinnon. P.; Newnham, R. H. J. Chem. Soc., Chem. Commun. 1989, 935. (11)Hou, Z.; Kobayashi, K.; Yamazaki, H. Chem. Lett. 1991,265.

C%

Figure 3. X-ray structure of 3. liquor after a few weeks (eq 4). Its 'H NMR spectrum in C6D6 showed unassignable complicated signals a t the region of 6 -8.0 to 18.0, suggesting that this compound was a paramagnetic species. A single crystal suitable for diffraction studies was then selected for crystallographic study which revealed that 3 was a trivalent

-

ytterbium complex, Yb(OC(=CCH=CHCHzCH=CH)Ph)2(0Ar)(HMPA)2,in which the central Yb atom was five-coordinated by one ArO,two benzophenone-originated units, and two HMPA ligands in a trigonal bipyramid form (Figure 3 and Table 2). Consistent with the trivalent feature of the central ytterbium the Yb-OAr bond (2.094(8)A) and the Yb-O(HMPA) bonds (av 2.223(9) A) in 3 are, respectively, 0.085 and 0.075 8, shorter than those found in the four-coordinated Yb(I1) complex 2. The bond distances between the Yb ion and the oxygen atoms of the benzophenone units (Yb-O(l): 2.091(11), Yb-0(2): 2.090(11) A) are almost the same as that of the Yb-OAr bond (2.094(8)A), and both are com arable with the Yb(II1)-O(naphthoxy) bond (2.06(1) found in Cp2Yb(naphthoxy)(THF).12 The sum of the bond angles around the carbonyl carbon atom in each benzophenone unit is 360(1)" for C(1) and 359(2)O for C(2), showing that the C(1) and C(2) atoms are still in a sp2-hybrid state. The bond distances for the benzophenone units indicate that one of the two phenyl groups in each benzophenone unit possesses two different types of C-C bonds, which is significantly deviated from a normal phenyl ring. As shown in Table 2 and Figure 3, the C(l)-C(ll), C(12)-C(13) and C(15)-C(16) bonds (av 1.37(2)A) are significantly shorter than the C(ll)-C(l2), C(ll)-C(l6), C(13)-C(14), and C(14)C(15) bonds (av 1.48(3)A). Similarly, the C(2)-C(21), C(22)-C(23), and C(25)-C(26) bonds (av 1.35(3)A) are shorter than the C(21)-C(22), C(21)-C(26) C(23)C(24), and C(24)-C(25) bonds (av 1.47(3) Both demonstrate a characteristic of a cyclohexadienylidene structure. Based on all these structural data and elemental analysis, complex 3 could be best described as an ytterbium(II1) aryloxide/enolate complex, which

8;

A).

(12) Zhou, X.-GWu, Z.-Z; Jin, Z . 3 . J.Organomet. Chem. 1992,431, 289.

Protonation of Lanthanide-Diary1 Ketone Dianion Species

Organometallics, Vol. 14, No. 11, 1995 5385

Table 2. Selected Bond Lengths (A) and Angles (deg) of 3 2.091(11) 2.093(8) 2.213(9) 1.490(10) 1.31(2) 1.35(2) 1.46(2) 1.36(2) 1.50(3) 1.46(2) 1.41(3) 1.34(3) 1.40(3) 1.43(3) 1.27(3) 1.44(3) 1.34(3) 1.38(3) 1.38(4) 1.44(2) 1.39(2) 1.42(3) 1.56(2) 1.55(2) 1.59(3) 1.56(3) 1.57(3)

2.090(11) 2.233(9) 1.495(10) 1.34(2) 1.34(1) 1.50(2) 1.46(2) 1.49(3) 1.39(3) 1.40(2) 1.42(3) 1.45(2) 1.50(2) 1.45(3) 1.56(3) 1.37(3) 1.48(3) 1.26(3) 1.49(3) 1.42(2) 1.57(2) 1.40(3) 1.38(2) 1.58(3) 1.55(3) 1.55(3)

C13

c15

C23A

Figure 4. X-ray structure of 4a.

features of the enolate parts in 4a were more clear. The C-C double bonds (av 1.35(3) A) of the enolate parts are obviously shorter than the C-C single ones (av 1.48121.0(5) 114.3(4) (3) A). Both hydrogen atoms in each CHz group can be 89.8(4) 91.1(4) easily located at the difference Fourier map and the 90.1(4) 124.7(5) C-C-C angles around the CHz units (C(14): 113(2)", 90.3(4) 89.1(4) C(24): 114(2)")are significantly deviated from 120".The 178.9(4) 89.8(4) 170(1) 169(1) average bond distance of Sm-O(HMPA) (2.333(10)A) 173(1) 178(1) in 4a is about 0.17 8, shorter than that found in the O(l)-C(l)-C(ll) 123(1) 173(1) divalent samarium complex Sm(HMPA)& (2.500(6)A),7 C(ll)-C(l)-C(l7) 123(1) 114(1) and the Sm-OAr bond (2.187(8)A) is about 0.12-0.15 0(2)-C(2)-C(27) 116(2) 121(2) C(2l)-C(2)-C(27) 122(2) A shorter than those of the Sm(I1)-OAr bonds found in (ArO)zSm(THF)3(av 2.304(8) A)SaJ3and [KSm(OAr)3is formally formed via the protonation a t the para(THF)], (av 2.339(9)A).14 These data suggest that the position of the phenyl ring in 1 by ArOH (vide infra). central samarium ion in 4a is in a trivalent state.g The Reaction of Samarium-Benzophenone Dianion bond distances of Sm-O(eno1ate) (av 2.180(12) A) is Species with 2,6-Di-tert-butylphenols.Samariumcomparable with that of the Sm-OAr bond, and both benzophenone dianion species was generated by the are close to but slightly longer than the terminal 5m-0 reaction of Sm metal with benzophenone in THF/HMPA. bonds found in other samarium(II1) aryloxides such as Its reaction with ArOH (Ar = C~Hz-~Bu2-2,6-Me-4), Smz(OC&Me2-2,6)6 (2.101(6)A)15and (v5-C5Me5)zSmI (OC&Me4-2,3,5,6)(2.13(1)A),16 Such bond lengthening however, yielded the enolate complex Sm(OC(=CCH= was also previously observed in other HMPA-coordinatI CHCHzCH=CH)Ph)Z(OAr)(HMPA)z(4a),which was the ed lanthanide c o m p l e ~ e and s ~ ~probably ~ resulted from samarium analode of 3, as a major product (60% yield the unusually strong electron donating ability of the based on benzophenone, 30% based on Sm) (eq 51, while HMPA ligands. Sm(I1) aryloxide analogous to 2 was not obtained. An The 'H NMR spectrum of 4a in CGDG was consistent with its X-ray structure. Well-resolved signals for the THFiHMPA ArOH ArO(67.75,2.67, 1.35),HMPA(62.11),andPh(67.90, Sm t Ph-C-Ph 7.28, 7.21) groups could be easily assigned. The broad OAr OAr peaks for the enolate units a t 6 6.94-5.28 (CH-CH) I I and 6 2.97 (CH2) were further confirmed by the DEPT HMPA- smHMPA (5) . \ and H,C-COSY experiments. Ard 0, H, In order to confirm the source of the hydrogen atoms C ph' 'Ph in the CH2 units of the enolates 3 and 4a, the reaction of the samarium-benzophenone dianion species with 4a,b sa ArOD (Ar = C~Hz-~Bu2-2,6-Me-4) was carried out. A 56.60% 2%

B

--

a: Ar = C6H2-'Eu2-2,6- M e 4 b: Ar = C&-'Eu2-2,6

X-ray analysis revealed that complex 4a was isostructural with 3 (Figure 4 and Table 3). The quality of the diffraction data for 4a seemed t o be higher than those obtained in the case of 3 and the cyclohexadienylidene

(13)Qi, G.-Z.; Shen, Q.; Lin, Y.-H. Acta Crystallogr., Sect. C 1994, 50C, 1456. (14)Evans, W. J.;Anwander, R.; Ansari, M. A.; Ziller, J. W. Inorg. Chem. 1995,34,5. (15)Barnhart, D. M.; Clark, D. L.; Gordon, J. C.; Huffman, J. C., Vincent, R. L.; Watkin, J. G.; Zwick, B. D. Inorg. Chem. 1994,33,3487. (16)Evans, W. J.; Hanusa, T. P.; Levan, K. R. Inorg. Chzm. Acta 1985,110, 191.

5386 Organometallics, Vol. 14, No. 11, 1995

Yoshimura et al.

Table 3. Selected Bond Lengths (A)and Angles (deg) of 4a Sm-O(l) Sm-0(3) Sm-0(5) P(2)-0(5) 0(2)-C(2) C(l)-C(ll) C(ll)-C(12) C(12)-C(13) C(14)-C(15) C(17)-C(18) C(18)-C(19) C(110)-C(111) C(2)-C(21) C(21)-C(22) C(22)-C(23) C(24)-C(25) C(27)-C(28) C(28)-C(29) C(21O)-C(211) C(31)-C(32) C(32)-C(33) C(33)-C(34) C(34)-C(311) C(36)-C(312) C(37)-C(39) C(312)-C(313) C(312)-C(315) 0(1)-Sm-0(2) 0(1)-Sm-0(4) 0(2)-Sm-0(3) 0(2)-Sm-0(5) 0(3)-Sm-0(5) Sm( 1)-O(1)-C(1) Sm(l)-0(3)-C(31) Sm(l)-0(5)-P(2) O(l)-C(l)-C(l7) c(l)-c(ll)-c(l2) C(l2)-C(ll)-C(l6) C(12)-C(l3)-C(14)

2.189(13) 2.187(8) 2.335(10) 1.480(11) 1.34(2) 1.36(2)1 1.46(3) 1.31(3) 1.45(4) 1.41(3) 1.40(3) 1.41(4) 1.36(2) 1.47(2) 1.38(3) 1.51(3) 1.45(2) 1.42(2) 1.39(3) 1.43(3) 1.39(2) 1.40(3) 1.54(2) 1.56(3) 1.54(3) 1.59(3) 1.56(3) 111.5(4) 89.5(4) 122.5(4) 90.0(4) 89.4(4) 168(1) 179(1) 171(1) 116(2) 120(2) 117(2) 120(2) 124(2) 118(2) 122(2) 120(2) 120(2) 125(1) 123(1) 123(1) 118(2) 113(2) 122(2) 118(1) 119(2) 121(2) 118(2) 120(2) 117(2) 121(2) 120(1) 121(2) 120(1) 118(1) 110(2) 114(2) 107(2) 113(1) 105(2) 106(2)

2.170(11) 2.331(10) 1.499(11) 1.32(2) 1.33(1) 1.49(2) 1.47(3) 1.57(4) 1.36(3) 1.43(3) 1.33(4) 1.41(3) 1.49(2) 1.44(2) 1.46(3) 1.34(3) 1.37(3) 1.37(3) 1.46(3) 1.43(2) 1.57(3) 1.37(3) 1.41(2) 1.55(3) 1.57(3) 1.59(3) 126.1(5) 89.4(4) 91.4(4) 90.5(4) 178.4(4) 170(1) 172(1) 121(2) 123(2) 123(2) 124(2) 114(2) 120(2) 120(2) 119(2) 123(2) 116(2) 112(1) 118(1) 118(1) 125(2) 122(2) 122(1) 121(1) 121(2) 121(2) 120(2) 120(1) 122(1) 123(2) 120(2) 121(2) 122(1) 106(1) 112(1) 108(2) llO(2) 111(2) 112(2)

similar treatment yielded the deuterated enolate Sm-

(OC(=CCH=CHCHDCH=CH)Ph),(OAr)(HMPA)2(4c) (eq 61, as identified by comparing its lH NMR spectrum with that O f 4a. This result suggests that the formation of 3 and 4a is via the direct protonation by ArOH. The similar reaction of the samarium-benzophenone dianion species with 2,6-di-tert-butylphenol afforded the

A

\ q

C3llh

Figure 6. X-ray structure of 5a. corresponding enolate Sm(OC(=CCH=CHCH,CH=CH)Ph)2(0Ar)(HMPA)z(4b,Ar = C6H3-tBuz-2,6,56% yield based on benzophenone) (eq 5). Sm

+

f

Ph-C-Ph

-THFIHMPA

ArOD 60%

OAr

u 4c Ar = C6H2-(Bu2-2,6-Me-4

In the course of the synthesis of 4a, when leaving the diethyl ether mother liquor to stand a t room temperature for a few months, several pale blocks of Sm(0CHPhz)(0Ar)2(HMPA)z(Sa,Ar = C6H~-~Buz-2,6-Me-4) precipitated (eq 5). These crystals rapidly lost their crystallinity upon removal of the mother liquor. Although a single crystal that was qualified for X-ray analysis was eventually sealed in a capillary, rapid decay occurred during the data collection and only the data with 28 range of 4-35' were successfully collected. Luckily, however, these data were good enough for us to solve the structure after a decay correction. As shown in Figure 5 and Table 4, this complex 5a possesses a highly distorted trigonal bipyramid structure with one benzophenone unit and two A r O s at the equatorial, and two HMPA ligands at the apical vertices. In contrast to the enolates 3 and 4a, the benzophenone unit in Sa was proved to be a diphenylmethoxy (OCHPhz)group rather than an enolate one. The carbonyl carbon atom C(1) was clearly of a typical tetrahedral configuration (Table 4), and the hydrogen atom attached to it was easily found in the difference Fourier map. Since there are two bulky ArO groups in Sa in contrast with only one in 3 or 4a, the apical HMPA ligands in 5a are more bent toward each other, forming an O(HMPA)-Sm-O(HMPA) angle of 163.3(4)",which is much smaller than the O(HMPA)-Yb-O(HMPA) angle in 3 (178.9(4)") and

Organometallics, Vol. 14, No. 11, 1995 5387

Protonation of Lanthanide-Diary1 Ketone Dianion Species

Table 4. Selected Bond Lengths (deg) of Sa

(A>and Angles

Sm-O(1) Sm-0(3) Sm-0(5) O(l)-C(l) 0(3)-C(31) C(l)-C(17) C(ll)-C(16) C(13)-C(14) C(15)-C(16) C(17)-C(112) C(19)-C(110) C(lll)-C(112)

2.15(1) 2.22(1) 2.37(1) 1.41(2) 1.36(2) 1.53(3) 1.46(3) 1.46(3) 1.41(4) 1.42(3) 1.44(3) 1.41(3)

Sm-0(2) Sm-0(4) P(1)-0(4) 0(2)-C(21) C(l)-C(ll) C(ll)-C(12) C(12)-C(13) C(14)-C(15) C(17)-C(18) C(18)-C(19) C(llO)-C(lll)

2.21(1) 2.34(1) 1.51(1) 1.36(2) 1.51(3) 1.37(3) 1.45(3) 1.34(3) 1.38(3) 1.43(3) 1.35(3)

0(1)-Sm-0(2) 0(1)-Sm-0(4) 0(2)-Sm-0(3) 0(2)-Sm-0(5) 0(3)-Sm-0(5) Sm-O(l)-C(l) Sm-O(3)-C(31) Sm-O(5)-P(2) O(l)-C(l)-C(l7)

107.8(4) 104.5(4) 144.4(4) 90.1(4) 89.3(3) 161(1) 170(1) 165.9(7) 111(2)

0(1)-Sm-0(3) 0(1)-Sm-0(5) 0(2)-Sm-0(4) 0(3)-Sm-0(4) 0(4)-Sm-0(5) Sm-O(2)-C(21) Sm-O(4)-P(l) O(l)-C(l)-C(ll) C(ll)-C(l)-C(l7)

107.9(4) 92.2(4) 83.8(4) 86.7(4) 163.3(4) 170(1) 177.8(7) 112(1) 109(2)

that in 4a (178.4(4)"). Possibly reflecting this steric influence, the IH NMR signals for the tBu (6 1.45),HMPA (6 1.86), and diphenylmethoxy (6 7.70-6.90) groups in Sa were rather broad, while those for the Me (6 2.69) and the C6H2 (6 7.75) groups were relatively sharp. Reaction of Samarium-Fluorenone Dianion Species with 2,6-Di-tert-butylphenols.Samarium-fluorenone dianion species was generated as in the case of benzophenone. A similar reaction with 2,6-di-tert-butyl4-methylphenol did not give any isolable solid product. However, colorless crystals of 6 were isolated from the reaction with 2,6-di-tert-butylphenol (eq 7). lH NMR, X-ray crystallography, and elemental analysis confirmed that 6 was the fluorenoxy analogue of Sa, Sm(fluorenoxy)yield). "he (OAr)2(HMPA)2(6, Ar = CsH~-~Bu2-2,6,64% overall structure of 6 is identical to that Of 5a (Figure 6 and Table 5). The bond angles of O(ary1oxy)-SmO(ary1oxy) (148.1(2)") and O(HMPA)-Sm-O(HMPA) (158.9(2)")in 6 parallel well those found in Sa (144.4(4) and 163.3(4)",respectively). Reflecting the difference between an alkoxide and an aryloxide, the Sm-O(fluorenoxy) bond (2.1116) A) in 6 is shorter than the SmOAr bonds (av 2.236(6)A), which is also similar to what was seen in 5a (Sm-O(di henylmethoxy): 2.154(11)A , Sm-OAr: av 2.217(10) ). Such difference in Sm-0 bond distances between an alkoxide and an aryloxide was also observed in other Sm(II1) complexes such as (q5-CsMes)2Sm[O(CH2)4(CsMes)3(THF)(2.08(1) and (q5-C5Me&Sm(OCsHMe4-2,3,5,6) (2.13(1)A)ls and was apparently due to the conjugation of the aryloxy anion with its aromatic ring.

fl

3l-I

+

w \

I \

/

THFlHMPA

0

ArOH

-

64%

6 Ar = CsH3-'Bu2-2,6

n

4

C

yell

c10

Figure 6. X-ray structure of 6. Table 5. Selected Bond Lengths (ded of 6 2.11l(5) 2.243(5) 2.399(4) 1.404(8) 1.33(1) 1.51(1) 103.9(2) 106.7(2) 148.1(2) 87.9(2) 88.8(2) 174.0(5) 172.4(4) 163.6(3) 113.8(5)

(A) and Angles 2.229(6) 2.383(4) 1.497(5) 1.34(1) 1.53(1) 108.0(2) 94.3(2) 84.9(2) 86.9(2) 158.9(2) 173.7(4) 178.4(4) 115.6(6) 101.3(7)

Similar t o those of Sa, the lH NMR signals of 6 for the C6H3 parts (6 7.90 (d), 7.31 (t))of the ArO groups were well-resolved,while those for the tBu units (6 1.561, the fluorenyl(6 7.51, 7.21, 7.04, 5.621, and the HMPAs (6 1.86) were quite broad. Thermolysis of the Samarium Enolates 4a-c. In the course of measuring the melting point of the enolate 4a under nitrogen, a color change from yellow to blue and finally to colorless was observed at the temperature range of 150-180 "C. Thermolysis of 4a was then carried out overnight in toluene at 180 "C in a flamesealed ampoule. Evaporation of the solvent left a colorless crystalline product which after recrystallization from toluenehexane yielded Sm(OCHPh2)dOAr)(HMPA)2 (7a,Ar = C6Hz-tBu2-2,6-Me-4,80% yield) (eq 8), a product which is formally derived from the 1,5hydrogen shift at the enolate groups Of 4a. The 'H NMR spectrum of 7a in was much clearer than that of its parent enolate 4a and could be assigned very easily. Signals for the aromatic protons of the diphenylmethoxy groups appeared a t 6 8.08 (d, ortho), 7.33 (t,metal, and 7.20 (t,para), while that for the CH appeared at 6 7.61 as a slightly broad singlet. The ArO unit showed sharp singlets a t 6 7.77 (C6H2), 2.71 (Me) and 2.01 (tBu). HMPAs gave a doublet a t 6 1.62. (17)Evans, W. J.;Ulibarri, T. A,; Chamberlain, L. R.; Ziller, J. W.; Alvarez, D.; Jr. Organometallics 1990,9, 2124.

Yoshimura et al.

5388 Organometallics, Vol. 14,No. 11, 1995 OAr I

4a,b

toluene or toluene-d8 180 "C 78-80°/o

OAr HMPA-

H,

,d

C

The similar thermolysis of a toluene solution of 4b at 180 "C resulted in the formation of Sm(OCHPhz)z(OAr)(HMPAk (7b,Ar = C~H3-~Bu2-2,6,78% yield) (eq 8). A n X-ray analysis of 7b shows that the geometry around the central Sm atom is very similar to that in 4a (Figure 7). Reflecting the characteristic of an alkoxide, however, the average bond distance of the Sm-O(dipheny1methoxy) bond (2.143(5) A) in 7b is shorter than that of the Sm-O(eno1ate) bond (2.18(1)A) in 4a, while the Sm-OAr (2.202(4) A and Sm-O(HMPA) (2.364(4) A) bonds are comparable with those (2.187(8) and 2.333(10) A , respectively) found in 4a. To understand the mechanism of the hydrogen shift process' in the formation of 7a,b, deuterium labeled experiments were performed. It was found that no deuterium was incorporated into the product 7a when 4a was thermolyzed in toluene-&. Furthermore, thermolysis of the deuterated enolate 4c in toluene afforded selectively 7c (eq 91,as identified by comparing its lH NMR spectrum with that of 7a. Scrambling of deuterium at the phenyl ring was not observed. These results suggest that the formation of 7a-c from 4a-c is an intramolecular one-step 1,5-hydrogen shift process. It is also noteworthy that although the complexes of type of 5a and 6 are isolable, disproportionation (ligand redistribution) in either the starting aryloxide/enolate complexes 4a-c or the aryloxidelalkoxide products 7a-c was not observed under the present thermolysis conditions.

Figure 7. X-ray structure of 7b. Table 6. Selected Bond Lengths (A)and Angles (deg) of 7b Sm-O(l) Sm-0(3) Sm-0(5) O(1)-C(1) 0(3)-C(31) C(l)-C(17) C(ll)-C(16) C(13)-C(14) C(15)-C(16) C(17)-C(112) C(19)-C(110) C(lll)-C(112) C(2)-C(27) C(21)-C(26) C(24)-C(23) C(25)-C(26) C(27)-C(212) C(29)-C(210) C(211)-C(212) O(1)-Sm-0(2) 0(1)-Sm-0(4) O(2)- Sm- 03 0(2)-Sm-0(5) 0(3)-Sm-0(5) Sm-O(l)-C(l) Sm-O(3)-C(31) Sm-O(5)-P(2) O(l)-C(l)-C(l7) 0(2)-C(2)-C(21) C(21)-C(2)-C(27)

2.1456) 2.202(4) 2.368(5) 1.388(8)

1.335(7) 1.53(1) 1.39(1) 1.35(2) 1.40(2) 1.387(9) 1.36(1) 1.41(1) 1.546(9) 1.382(9) 1.37(1) 1.39(1) 1.37(1) 1.37(1) 1.41(1) 117.7(2) 90.6(2) 120.7(2) 9 1.4(2) 88.5(2) 171.2(4) 179.1(4) 165.6(3) 112.3(5) 112.1(5) 111.0(5)

Sm-0(2) Sm-0(4) P(1)-0(4) 0(2)-C(2) C(1)-C( 11) C(ll)-C(12) C(12)-C(13) C(14)-C(15) C(17)-C(18) C(18)-C(19) C(110)-C(111) C(2)-C(21) C(21)-C(22) C(22)-C(23) C(24)-C(25) C(27)-C(28) C(28)-C(29) C(21O)-C(211)

2.141(5) 2.359(4) 1.477(5) 1.386(9) 1.52(1) 1.39(1) 1.39(1) 1.37(2) 1.41(1) 1.40(1) 1.38(1) 1.522(9) 1.40(1) 1.39(1) 1.39(1) 1.39(1) 1.40(1) 1.38(1) 121.6(2) 90.2(2) 90.4(2) 89.0(2) 177.4(2) 166.3(4) 169.6(3) 110.3(6) 112.6(6) 111.4(5)

OAr

I

HMPA-sm-HMPA

4c OAr toluene

I

HMPA-Sm-HMPA

7c

Reactions of Complexes 2,4a, and 7a with Aryl Alcohols. In the reactions of the lanthanide ketone dianion species with 2,6-di-tert-4-methylphenols, it seemed that the use of a further excess amount of the alcohols gave little influence on the distribution of the products. In order to gain more information on the stability of the products in the presence of an aryl alcohol and to have a better understanding about their formation, reactions of 2,4a, and 7a with aryl alcohols were investigated. In the reaction of 2 with ArOH (Ar = C~Hz-~Buz-2,6-Me-4), no change was observed as monitored overnight in C6D6 by lH NMR spectroscopy, although oxidation of divalent ytterbium species by a proton was seen previously.8 The reaction of 4a with Ar'OH (Ar'= C6H3-tBuz-2,6)in benzene yielded quan-

Protonation of Lanthanide-Diary1 Ketone Dianion Species

Organometallics, Vol. 14,No. 11, 1995 5389

Scheme 1

titatively the aryloxy exchange product 4b (eq 10). No OAr

I

HMPA-sm-HMPA

Ar‘OH - ArOH

OAr‘

I

HMPA-Sm-HMPA

bo-

4b

Ar = C8H2-‘Bu2-2,6-Me-4 Ar‘ = C6H3-tBU2-2,6

protonation occurred at either the carbon or oxygen atoms of the enolate parts, even when 2 equiv of Ar’OH was added. The similar reaction of 7a with Ar’OH (Ar’ = C&WBu2-2,6) also afforded the corresponding aryloxy exchange product 7b (Scheme l), while the expected protonation at the more basic diphenylmethoxy anion to release benzhydrol was not observed. In contrast, however, when less bulky 2,6-dimethylphenol (Ar”0H) was allowed t o react with 7a, the diphenylmethoxy substitution product Sm(OAr)(OAr”)z(HMPA)2(8, Ar” = CsH3-Me2-2,6,70% yield) was isolated (Scheme 1).It is apparent from these results that steric influence plays an important role in the 2,6-di-tert-butylphenol-involved reactions. Electronically, attack of a proton on a more basic alkoxy anion should be favored over on a less basic aryloxy one. In the reaction of 7a with Ar’OH, however, steric repulsion between the two bulky 2,6-di-tertbutylphenoxy groups probably forced the more bulky ArO group, rather than the diphenylmethoxy group, to leave the metal center by taking the proton from the incoming Ar‘OH (Scheme 1). In the reaction of 7a with the less bulky Ar”OH, the electronic factor (basic-

ity) became dominant, and the more basic diphenylmethoxy anions were protonated.18 Concluding Remarks. The overall reactions of lanthanide ketone dianion species with aryl alcohols are summarized in Scheme 2.19 These reactions can be classified into the following three types: (a) simultaneous protonation at both the carbon and the oxygen atoms of the carbonyl group, (b) protonation only at the carbonyl carbon, and (c) protonation at the para-position of the phenyl ring. The selectivity among these three types of reactions seems to be dependent on both the metals and the ketones. In the case of benzophenone (R = Ph), when the metal is ytterbium, “path a” to yield 2 dominates the reaction, while when the metal is samarium, protonation at the phenyl ring (“path c”) to give the enolates 4a,b occurs selectively. This metaldependent selectivity probably originates from the difference between the Sm(I1) and Yb(I1) ions. Since Sm(I1) ion is bigger in radius and softer than Yb(II), the negative charges in the Sm(I1)-benzophenone dianion species must be more delocalized into its phenyl rings, which probably causes the protonation to occur more easily at the aromatic ring. Ketone dependence of the reactivity is also observed. The reaction of samarium fluorenone dianion species (R,R = biphenyl2,2’-diyl) proceeds exclusively via “path b” t o give 6, while in the case of samarium benzophenone dianion this path leading to 5a is a minor process. This reactivity difference between benzophenone and fluorenone suggests that the “localization” of the electron density at the para-position of the fluorenone dianion is not as high as in the case of benzophenone, which is probably caused by the planarity of the fluorenyl ring. Reaction paths a and b, which proceed via protonation at the carbonyl group, are not difficult to understand, while path c to yield the dienolate complexes 3 and 4a,b is not very clear. This process is probably mediated by (18)The reaction of 4a with 2,6-dimethylphenol was similar to its reaction with 2,6-di-tert-butylphenol and gave the aryloxy exchange product as monitored by ‘HNMR spectroscopy, which implies that the enolate anions in 4a are less basic than the aryloxy one. (19)Although the structure of the fluorenone dianion species is not yet known, for simplicity we choose the structure of the Yb(I1)benzophenone dianion (1) to represent all the lanthanide ketone dianion species in Scheme 2.

Yoshimura et al.

5390 Organometallics, Vol. 14, No. 11, 1995

Scheme 2

I

2: Ln = Yb, major OAr

R

“path b”

R\J

5a: Ln = Sm, R = Ph, minor 6: Ln = Sm, R,R = biphenyl-2,2-diyl, major

-

R Ph; R,R = biphenyC2,2’diyl ArOH = 2,6-di-fe~-t-butylphenols

H

1 I

OAr

I

ArOH

3: Ln = Yb, minor; 4a,b: Ln = Sm, major

a Ln(I1) enolate intermediate like I which is formed by direct protonation a t the para-position of the phenyl ring (Scheme 2). Further reaction of I with ArOH produces the monomeric Ln(II1) enolates 3 and 4a,b. The possible byproduct (Ar0)zLnH or (ArO)3Ln,however, is yet to be identified. The selective formation of trivalent rather than divalent samarium complexes in the present reactions probably reflects the strong reducing power of HMPA-coordinated samarium(I1) specie^.^,^^ The formation of the enolates 3 and 4a,b in the present reactions is closely related t o the well-known Birch reductions of aromatic compounds bearing electronwithdrawing groups, in which metal enolate intermediates are believed to be formed via monoprotonation of dianionic species but have never been well characteri ~ e d As . ~far~ as ~ we ~ are aware, complexes 3 and 4a represent the first examples of structurally characterized metal enolate compounds which model the enolate intermediates formed in the Birch reductions. The alcohol substitution reactions of the aryloxide/ enolate 4a and the aryloxidelalkoxide 7a demonstrate that both electronic and steric factors play an important (20)Oxidation of a divalent ytterbium species by a proton was reported.8 (21) For reviews on Birch reductions, see: (a) Birch, A. J. Q. Rev., Chem. SOC.1950,4,69. (b) Birch, A. J.; Smith, H. ibid. 1958,12, 17. (c) Smith, H. Organic Reactions in Liquid Ammonia; Wiley: New York, 1963; Vol. 1,Part 2. (d) Harvey, R. G. Synthesis 1970,161. (e) House, H. 0. in Modern Synthetic Reactions, 2nd ed.; W. A. Benjamin: Menlo Park, CA, 1972; Chapter 3. (0 Hook, J. M.; Mander, L. N. Nut. Prod. Rep. 1986, 3, 35. (g) Mander, L. N. in Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds; Pergamon: New York, 1991; Vol. 8, Chapter 3.4.

role in determining the composition of the products. These reactions, combined with the thermolysis of the enolate complexes, could constitute a useful method for the synthesis of a variety of samarium complexes with mixed aryloxide/alkoxideligands, a class of compounds which is difficult to access by conventional methods.6,22

Experimental Section General Methods. All manipulations were carried out under dry and oxygen-freeargon atmosphere by using Schlenk techniques or under nitrogen atmosphere in an Mbraun glove box. The argon was purified by passing through a DRYCLEAN column (4A molecular sieves, Nikka Seiko Co.) and a GASCLEAN GC-RX column (Nikka Seiko Co.). The nitrogen in the glove box was constantly circulated through a copper/ molecular sieves (4A) catalyst unit. The oxygen and moisture concentrations in the glove box atmosphere were monitored by an Oz/HzO COMBI-ANALYZER (Mbraun) to assure both were always below 1 ppm. Samples for NMR spectroscopic studies were prepared in the glove box. J. Young valve NMR tubes (Wilmad 528-JY) were used to maintain the inert atmosphere all the time during the measurements. Thermolysis study in toluene-ds was conducted in an NMR tube sealed under vacuum. lH NMR spectra were recorded on a JNMGSX 500 (FT, 500 MHz) or a JNM-EX 270 (FT, 270 MHz) spectrometer and are reported in ppm downfield from tetramethylsilane. Elemental analyses were performed by the chemical analysis laboratory of The Institute of Physical and (22) For recent reviews on lanthanide alkoxides or aryloxides, see: (a) Mehrotra, R. C.; Singh, A.; Tripathi, U. M. Chem. Rev. 1991,91, 1287. (b) Schaverien, C. J. In Advances in Oganometallic Chemistry; Stone, F. G. A., West, R., Eds.; Academic Press: San Diego, 1994; Vol. 36, p 283.

Protonation of Lanthanide-Diary1 Ketone Dianion Species Chemical Research (RIKEN). Tetrahydrofuran (THF), diethyl ether, toluene, benzene, and hexane were distilled from sodiumhenzophenone ketyl, degassed by the freeze-thaw method (three times), and dried over fresh Na chips in the glove box. Hexamethylphosphoramide (HMPA) was distilled from Na under reduced pressure, degassed by the freeze-thaw method (three times), and dried over molecular sieves (4A). THF-ds, toluene-&, and C6D6 were commercial grade and were degassed by the freeze-thaw method (three times) and dried over fresh Na chips in the glove box. Diary1 ketones and aryl alcohols (Tokyo Kasei Co.) were the highest commercial grade and used as received. ArOD was prepared by deuteration of ArONa, which was generated by reaction of ArOH with Na, with CH30D. Lanthanide metals (40 mesh) were obtained from Rare Metallic Co. and Aldrich.

Generation of Lanthanide Ketone Dianion Species. The methods for generation of samarium and ytterbium ketone dianion species were similar and only a typical procedure is given below. The metal was first activated by stirring with 2% of ICHzCHzI in THF a t room temperature for about 1 h. HMPA was then introduced. Addition of 1 equiv of a diary1 ketone in THF yielded the corresponding metal ketone dianion species in 30-60 min. Dramatic color changes were always observed, and the color of the metal ketone dianion species was dependent on both metals and ketones: Ybhenzophenone, purple; Yblfluorenone, dark-green; Smhenzophenone, redbrown; Smlfluorenone, dark-brown. TYbe-t11,t12-OCPh2)(HMPA)212 (1). Complex 1 was isolated similarly as previously d e ~ c r i b e d A . ~minor modification was made. Evaporation of the reaction mixture of Yb metal and benzophenone followed by addition of diethyl ether precipitated 1 as needlelike purple-black crystals in 65% yield. This reaction could be done on a 10 mmol scale. Y~(A~O)Z(HMPA)Z (Ar = CJ-I2-'Bu2-2,6-Me-4) (2). To a purple THF (5 mL) solution of 1 (714 mg, 0.5 mmol) was added a THF (5 mL) solution of ArOH (Ar= C&€~-~Bu2-2,6-Me-4) (440 mg, 2 mmol). The resulting light brown solution was then stirred at room temperature for 3 h. Evaporation of THF and addition of diethyl ether precipitated an orange crystalline product which was separated by filtration. Recrystallization of the crystalline product from THF yielded (ArO)2Yb(HMPA)2 (2)as orange-red blocks (775 mg, 80%yield). One-pot reaction of the Ybhenzophenone mixture with ArOH gave a similar result. The reaction of the Yb-fluorenone dianion species with ArOH also afforded 2 in 65% yield. 'H NMR (C&6,22 "C): 6 7.33 (s, 4 H, CeHz), 2.53 (s, 6 H, Me), 2.15 (d, J p - n = 9.3 Hz, 36 H, NMe), 1.85 (s, 36 H, tBu); (THF-de, 22 "C) 6 6.64 (s, 4 H, C,&), 2.61 (d, J p - H = 9.3 Hz, 36 H, NMe), 2.07 (s, 6 H, Me), 1.44 (s,36 H, tBu). Anal. Calcd for C42Hs2N604P2Yb: C, 52.00; H, 8.52; N, 8.66. Found: C, 51.85; H, 8.62; N, 8.46.

Organometallics, Vol. 14, No. 11, 1995 5391 I

CHCH2CH=CH)Ph)2(0Ar)(HMPA)2 (4a)as yellow needlelike crystals (3.28 g, 60% yield based on benzophenone). The reaction with 1equiv of ArOH also gave 4a as the only isolable product. IH NMR (C&, 22 "C; assignment was confirmed by DEPT and H,C-COSY experiments): 6 7.90 (d, J = 7.3 Hz, 4 H, Ph), 7.75 (9, 2 H, CsHz), 7.28 (t, J = 7.3 Hz, 4 H, Ph), 7.21 (t,J =7 . 3 H z , 2 H , P h ) , 6 . 9 4 ( b r d ,J = 8 . 9 H z , 2 H , C H ) , 6 . 7 6 (br d, J = 8.9 Hz, 2 H, CH), 5.55-5.65 (br m, 2 H, CHI, 5.285.40 (br m, 2H, CH), 2.97 (br s, 4 H, CH2), 2.67 (s, 3 H, Me), 2.11 (d, J = 9.6 Hz, 36 H, NMe), 1.35 (s, 18 H, tBu). Anal. Calcd for Ca3HelN,@6P2Sm: c, 58.16; H, 7.46; N, 7.68. Found: C, 59.45; H, 7.62; N, 7.86. S~(OC(=~CH=-CHCH~CH~H)P~)Z(OA~)(HMPA)~ (Ar = C&~-~Bu2-2,6) (4b). Complex 4b was synthesized in 56% yield similarly as 4a by the reaction of samarium benzophenone dianion species with 2,6-'Buz-c&oH. I t could also be obtained quantitatively by reaction of 4a with 2 equiv of 2,6tBu2-C6H30H in benzene. 'H NMR (C&, 22 "c). 6 7.956.90 7.85 (m, 6 H, Ph, CJ-I3), 7.35-7.10 (m, 7 H, Ph, (br d, J = 10.6 Hz, 2 H, CH), 6.77 (br d, J = 10.2 Hz, 2 H, CH), 5.55-5.65 (br m, 2 H, CHI, 5.30-5.40 (br m, 2H, CH), 2.96(brs,4H,CH2),2.10(d,J=9.3Hz,36H,NMe),1.33(~, 18 H, tBu). Anal. Calcd for C62H&@5P2Sm: C, 57.80; H, 7.37; N, 7.78. Found: C, 57.20; H, 7.46; N, 7.74.

Sm(OC(=CCH=CHCHDCH-CH)Ph)Z(OAr)(HMPA)z (Ar= CJ&-'Bu2-2,6-Me-4) (44. Complex 4c was synthesized similarly as 4a by the reaction of samarium benzophenone dianion species with ArOD (Ar = CJ&A3~2-2,6-Me-4). IH NMR (CsDs, 22 "C): 6 7.90 (d, J = 7.3 Hz, 4 H, Ph), 7.75 (s, 2 H, CsHz), 7.28 (t, J = 7.3 Hz, 4 H, Ph), 7.21 (t, J = 7.3 Hz, 2 H, Ph), 6.94 (br d, J = 8.9 Hz, 2 H, CHI, 6.76 (br d, J = 8.9 Hz, 2 H, CHI, 5.55-5.65 (br m, 2 H, CHI, 5.28-5.40 (br m, 2H, CH), 2.97 (br s, 2 H, CHD), 2.67 (s, 3 H, Me), 2.11 (d, J = 9.6 Hz, 36 H, NMe), 1.35 (s, 18 H, tBu).

Sm(OCHPh2)(OAr)&IMPA)z (Ar= CeH2-tBu2-2,6-Me4) (5a). During the isolation of 4a,when leaving the diethyl ether filtrate, from which 4a had been separated, to stand at room temperature for a few months, a few pale blocks of Sm(OCHPh2)(0Ar)2(HMPA)z(Sa)precipitated (ca. 2% yield). IH NMR (C6D6,22 "c). 6 7.75 (S,4 H, C&), 7.70-6.90 (br m, 11

H, CH, Ph), 2.69 (s, 6 H, Me), 1.86 (br s, 36 H, NMe), 1.45 (br s, 36 H, tBu). Anal. Calcd for C56H&@5P2Sm: C, 58.42; H, 8.29; N, 7.43. Found: C, 58.95; H, 8.47; N, 7.54. Sm(fluorenoxy)(OAr)2(HMPA)2(Ar= C&-'Bu2-2,6) (6). To a dark brown reaction mixture of Sm (151 mg, 1 mmol) and fluorenone (180 mg, 1 mmol) in THF (5 mL) and HMPA (1mL) was added a THF (5 mL) solution of ArOH (Ar = C6H3tBu2-2,6)(413 mg, 2 mmol). The resulting light brown solution was then stirred a t room temperature for 3 h. Evaporation of Yb(OC(=CCH=CHCH2CH=CH)Ph)z(OAr)(HMPA)2(Ar THF and addition of ether precipitated a yellow crystalline = C,$&-'Bu2-2,6-Me-4) (3). During the isolation of 2 (see product which after recrystallization from THF/ether gave Smabove), when leaving the diethyl ether filtrate, from which 2 (fluorenoxy)(ArO),(HMPA)Z(6,Ar = C6H3-tBu2-2,6)as colorless had been separated, to stand at room temperature for a few crystals (708 mg, 64% yield). Using 1 equiv of ArOH in this reaction also afforded 6 as the only isolated product. 'H NMR weeks, yellow needlelike crystals of Yb(OC(--dCH-CHCHz7.51 (br m, 4 ( c a s , 22 "C). 6 7.90 (d, J = 7.6 Hz, 4 H, CH=CH)Ph)2(0Ar)(HMPA)2 (3)precipitated (ca. 30 mg, 5% H, C ~ ~ H B 7.31 ) , (t, J = 7.6 Hz, 2 H, C&), 7.21 (br m, 2 H, yield based on benzophenone). Anal. Calcd for C S ~ H ~ ~ N ~ O ~ PC12H*), Z - 7.04 (br m, 2 H, C ~ ~ H 5.62 B ) , (9, 1H, CH), 1.86 (d, J = Yb: C, 56.98; H, 7.31; N, 7.52. Found: C, 56.35; H, 7.62; N, 8.9 Hz, 36 H, NMe), 1.56 (br s, 36 H, tBu). Anal. Calcd for 7.46. C53H&$&P2Sm: C, 57.84; H, 7.97; N, 7.64. Found: C, 58.40; H, 8.08; N, 7.80. Sm(OC(==CCH==CHCH2CH=CH)Ph)2(OAr)(HMPA)2 (Ar Sm(OCHPhz)z(OAr)(HMPA)2(Ar = C&2Buz-2,6-Me= C,~Hz-~Buz-2,6-Me-4) (4a). To a red-brown reaction mixture 4)(?a). In the glove box 4a (415 mg, 0.38 mmol) was dissolved of Sm (1.503g, 10 mmol) and benzophenone (1.8228,lO mmol) into 20 mL of toluene in a ampoule which was then connected in THF (20 mL) and HMPA (8 mL) was added ArOH (Ar = to a vacuum line, cooled down to -196 "C and flame-sealed C6H2-tBu2-2,6-Me-4)(4.408 g, 20 mmol) in THF (15 mL). The under vacuum. After being thawed a t room temperature, the resulting light brown solution was then stirred at room light yellow solution was heated at 180 "C overnight in an temperature for 3 h. Evaporation of THF and addition of oven. The resultant colorless solution was cooled down to room diethyl ether precipitated a yellow crystalline product which temperature and then taken into the glove box where the was further separated by filtration. Recrystallization of the reaction mixture was transferred into a Schlenk flask. EvapoI ration of the solvent yielded colorless fine crystals which after crystalline compound from THF yielded Sm(OC(=CCH=

5392 Organometallics, Vol. 14,No. 11, 1995

Yoshimura et al.

Table 7. Summary of Crystal Data 4a C4zHszN604Pzn C~i3HsiNs05Pzn C53HslN605PzSm monoclinic monoclinic hexagonal P2dn (No. 14) P6122 (NO.178) P21/n (No. 14) 10.663(8) 10.631(5) 11.672(1) 33.827(4) 33.666(3) 11.672(1) 16.205(2) 16.022(1) 65.664(10) 2

formula cryst syst space group a (A) b (A) c

(A)

3

no. ofvariables R (%I R w (%I

C6zH7gN605PzSm t~clinic P1 (No. 2) 10.637(2) 15.721(2) 17.102(3) 89.88(1) 101.72(2) 95.40(2) 2787.5

96.61(2)

95.08(2)

7747.3 6 1.248 Cu Ka,1.54184 +h, f k , +1 4

5694.0 4 1.303 Mo Ka,0.71073 f h , +k, +I 4

5805.7 4 1.250 Mo Ka,0.71073 f h , +k, +1 4

6064.0 4 1.239 Mo Ka,0.71073 hh, +k, +I 16

4-136 19.045 2736 2161 ( x

4-55 17.378 8560 6923 ( x = 4)

4-55 11.132 9685 5679 (x = 5)

4-35 10.678 4065 3420 (x = 3)

4-55 11.345 12593 11344 (x = 5)

4-55 11.589 12154 10355 ( x = 5)

605 7.14 8.75

621 7.81 8.92

627 6.60 7.43

665 5.67 7.26

696 4.68

y (deg)

(lF"l'Xa(lF"I))

7b

96.80(1)

/3 (deg)

v (A31

6

C53H87N605P2Sm triclinic P1 (No. 2) 12.546(2) 19.836(4) 12.411(2) 100.76(1) 105.32(1) 74.60(1) 2849.3 2 1.283 Mo Ka,0.71073 fh,f k , +I 8

a (deg)

Z Dealcd (g ~ m - ~ ) radiation, 1 (A) data collcd scan speed (deg/min) 28 range (deg) p (mm-') no. of reflns colld no. of reflns with

5a C66H93N605PzSm monoclinic P21/n (No. 14) 15.496(3) 20.686(3) 18.992(4)

249 5.12 6.14

= 4)

recrystallization from toluenehexane gave 7a as colorless plates (332 mg, 80% yield). If the thermolysis was done a t temperatures below 150 "C, a mixture of 4a and 7a was obtained. 'H NMR (C6D6, 22 " c ) 6 8.08 (d, J = 7.3 Hz, 8 H, 7.61 (br s, 2 H, CHI, 7.33 (t,J = 7.3 Ph), 7.77 (s, 2 H, Hz, 8 H, Ph), 7.20 (t, J = 7.3 Hz, 4 H, Ph), 2.71 (s, 3 H, Me), 2.01 (s, 18 H, tBu), 1.62 (d, J = 9.6 Hz, 36 H, W e ) . Anal. Calcd for C53H81N605P~Sm: c, 58.16; H, 7.46; N, 7.68. Found: C, 58.19; H, 7.46; N, 7.61. Sm(OCHPh2)2(OAr)(HMPAh(Ar= CJ4~-~Bu2-2,6) (7b). Colorless 7b was obtained in 78% yield similarly as 7a by thermolysis of 4b. 'H NMR (C6D6, 22 " c ) 6 8.07 (d, J = 7.3 Hz, 8 H, Ph), 7.93 (d, J = 7.9 Hz, 2 H, C6H3), 7.59 (br s, 2 H, CH), 7.36-7.15 (m, 13 H, Ph, 1.99 (s, 18 H, tBu), 1.61 (d, J = 9.6 Hz, 36 H, NMe). Anal. Calcd for C52H79N605P~Sm: C, 57.80; H, 7.37; N, 7.78. Found: C, 57.73; H, 7.39; N, 7.70. Sm(OClsHloD)2(0Ar)(HPA)2(Ar= CsH~-~Bu2-2,6-Me4) (7c). Colorless 7c was obtained in 80% yield similarly as 7a by thermolysis of 4c. 'H NMR (C&, 22 " c ) 6 8.08 (d, J = 7.3 Hz, 8 H, 0-Ph), 7.77 (s, 2 H, C6H2), 7.61 (br s, ca. 1H, CH(D)), 7.33 (t, J = 7.3 Hz, 8 H, m-Ph), 7.20 (t,J = 7.3 Hz, ca. 3 H, p-Ph), 2.71 (s, 3 H, Me), 2.01 (6, 18 H, tBu), 1.62 (d, J = 9.6 Hz, 36 H, NMe). Sm(OAr)(OAr")2(HMPA)2 (Ar= CsHzJBuz-2,6-Me-4,Ar" = CaH~-Me2-2,6) (8). To a THF solution (4 mL) of 7a (58 mg, 0.053 mmol) was added 2,6-dimethylphenol(l3mg, 0.11 mmol) in THF (4 mL). After being stirred a t room temperature overnight, the solvent was evaporated. The residue was washed with hexane and recrystallized from EtzOhexane to give 8 as colorless fine crystals (36 mg, 70% yield). 'H NMR (C6D6, 22 " c ) 6 7.88 (5, 2 H, CsHz), 7.28 (d, J = 7.4 Hz, 4 H, C&), 6.92 (t, J = 7.4 Hz, 2 H, C6H3), 2.75 (s, 3 H, Me), 2.70 (s, 12 H, Me), 1.89 (d, J = 9.6 Hz, 36 H, NMe), 1.55 (s, 18 H, tBu). Anal. Calcd for C43H7&05P2Sm: C, 53.22; H, 8.00; N, 8.66. Found: C, 53.33; H, 7.85; N, 8.70. X-ray Crystallographic Studies. Crystals of X-ray quality were obtained as described in the preparations. The crystals were manipulated in the glove box under a microscope (Wild M3Z, Leica) mounted on the glove box window and were sealed in thin-walled glass capillaries. Data collections were performed at 20 "C on an Enraf-Nonius CAD4 diffractometer with a rotating anode (Cu Ka radiation, I = 1.54184 A , graphite monochromator, w-scan) for 2 and an Enraf-Nonius CAD4 diffractometer with Mo Ka radiation ( I = 0.71069 A , graphite monochromator, w-scan) for 3, 4a, Sa, 6, and 7b. Lattice constants and orientation matrices were obtained by

n

2

1.287 Mo Ka,0.71073 f h , i k , +1 8

5.80

least-squares refinement of 25 reflections with 30" 5 0 5 35" for 2 and 10" 5 f3 5 13" for 3, 4a, Sa, 6, and 7b. Three reflections were monitored periodically as a check for crystal decomposition or movement. In the case of Sa, a rapid decay was observed and only the data with 20 range of 4-35" were successfully collected. All data were corrected for X-ray absorption effects and in the case of 5a a decay correction was also made. The observed systematic absences were consistent with the space groups given in Table 7. In the case of 2, anomalous dispersion effects were further used to distinguish P6'22 from P6522. The structures were solved by MULTANZ3 to locate the metal atoms, and the remaining non-hydrogen atoms were found from subsequent difference Fourier syntheses. Important hydrogen atoms were also located from the difference Fourier maps, but attempts to find other hydrogen atoms were not made. Refinements were performed anisotropically for non-hydrogen atoms and isotropically for hydrogen atoms by the full-matrix least squares method for 2 and block-diagonal least squares method for 3,4a, 5a, 6, and 7b.24 The function minimized in the least-squares refinements was UIF,I - lFc1)2.Neutral atomic scattering factors were taken from the Znternational Tables for X-Ray Crystall~graphy.~~ The residual electron densities were of no chemical significance. Crystal data, data collection, and processing parameters are given in Table 7 .

Acknowledgment. This work was partly supported by The Special Grant for Promotion of Research from The Institute of Physical and Chemical Research (RIKEN) and by grants from the Ministry of Education, Science and Culture of Japan. Supporting Information Available: Listings of atomic coordinates, thermal parameters, and bond distances and angles for 2, 3,4a, 5a, 6, and 7b (40 pages). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, and can be ordered from the ACS; see any current masthead page for ordering information. OM9503961 (23)Main, P.;Hull, S. E.; Lessinger, L.; Germain, G.;Decherq, J.P.; Woolfson, M. M. MULTAN 78, University of York, York, 1978. (24)Sakurai, T.;Kobayashi, K. Rikagaku kenkyusho Hokoku 1979, 55, 69. (25)Cromer, D. T.; Waber, J. T. In International Tables for X-Ray Crystallography; Kynoch: Birmingham, England, 1974; Vol. IV.