Synthesis and disproportionation of mixed ligand ytterbium organomettalics involving cyclopentadienyl and β-diketonato chelate ligands

369

Journal of Organomtallic Chemistry, 326 (1987) 369-374 EWvier !kquoia S.A., Lausame - printed in The Netherlands

S-IS AND DISPROPORTIONATION OF MIXED LIGAND YTIXRMUM ORGANOMETALLICS INVOLVING CYCLOPENTADIENYL AND &DIKETONATO CHIZLATELIGANDS *

HUAIZHU

MA and ZHONGWEN

Luboratoty for Orgmic (Received

YE

Chemistry, Anhui Nomal

University Wuhu, Anhui Province (China)

September 16th, 1986; in revised form December 12th, 1986)

Twelve compounds either of type CpJb(diket) or CpYb(diket), (Cp = $-CsH,, d&et = &%ketonato) have been synthesized. Compounds of the former type are much more thermally stable than those of the latter. But, all twelve compounds tend to disproportionate into Cp,Yb and Yb(diket), at moderately high temperatures.

IlltKMhlCtiOIl

Up to now only two lanthanoid organometallics involving both Cp ($-C,H,) and d&et (&diketonato) chelate ligands have been prepared (by Bielang and Fischer) [l], namely, ChYb(acac) and ChYb(tmd) (where Hacac = acetylacetone, Htmd = 2,2,6,6-tetramethyl-3,5-heptanedione). They reported that both compounds did not sublime in vacua and that the mass spectra of both compounds displayed essentially the signals of the Yb(diket),+ (with n = l-3) fragments (and signals of fragments thereof), but not of fragments carrying a Cp-ligand. However, the vibrational spectra of both compounds are fairly indicative of residual r-bonded Cp-ligands. We presume that these two compounds are not stable to heat, and disproportionation owing to rearrangement of ligands would probably take place at a moderately high temperature.

Results and discussion For the purpose of studying the thermal stability of lanthanoid organometallics of this class, and adopting the very versatile method of liberating cyclopentadiene

* Part of this paper was presented at the 17th Rare Earth Research Conference as a poster, June, 1986, Hamilton, Canada.

0022-328X/87/$03.50

Q 1987 Elsevier Sequoia S.A.

370

from a Cp,,Yb moiety by the action of protonic acids stronger than C,H,, we have synthesized twelve compounds by the reaction of Cp,Yb with acetylacetone (H-acac), 2,2,6,6-tetramethyl-3,5-heptanedione (H-tmd), l,l,l-trifluoroacetylacetone (Htfacac), benzoylacetone (H-bzac), trifluoroacetoacetyl-al-thiophene (H-tfacth) and 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone (H-bmphpz). They are: 1: 1 ratio of reactants Cp,Yb(acac) CpJb(tmd) Cp,Yb(tfacac) CpJb(bzac) Cp,Yb(tfacth) CpJb(bmphpz)

1 : 2 ratio of reactants CpYb(acac),

(I) (III)

Cpm(tmd) z CpYb( tfacac) 2 CpYb(bzac) Z CpYb(tfacth),

;I) (IX) (XI)

Cpn(bmphpz),

(II) (IV) K’I, (X) (XII)

(I) and (III) are known compounds, but the others are new. All compounds were identified by elemental analysis, IR (Table 1) and MS (Table 2) spectroscopy. All twelve compounds exhibit four characteristic Cp absorption at about 780, 1010,1440, 3100 cm-’ and an absorption peak at about 250 cm-’ for Ln-C of the a-bonded Cp group [2]. All of them exhibit the characteristic C-O and C-C multiple absorption bands of 0-chelate complexes [3]. The twelve compounds can be classified into two types: CpYb(diket), and Cp,Yb(diket). The mass spectra of all the compounds were recorded at different temperatures of vaporization. Contrary to earlier observations [4], that no peak which can be assigned to diytterbium species is displayed in the mass spectra of Cp,Yb(acac)(I) (or any other compounds), our mass spectra of Cp*Yb(diket) displayed signals of Cp,Yb(diket)+ and of fragments thereof even when the temperature was raised to 180 o C. However, at much higher temperatures of 200-350 o C, signals of both Cp$b+ and Yb(diket)i appeared. In contrast, the mass spectra of CpYb(diket), at 50-180 o C displayed signals of Yb(diket),+ and Cp,Yb(diket)+ in addition to CpYb(diket),+. As the temperature was raised to between 200-300 o C, the mass spectra showed signals of CpJb+ in addition to CpYb(diket),+, Cp,Yb(diket)+ and Yb(diket)3+ . Heat can bring about the disproportionation of these two types of compounds, however, CpYb(diket), is thermally less stable than Cp,Yb(diket). In view of the MS data, the disproportionation presumably involves the following equilibria: 2CpYb(diket) 3Cp,Yb(diket)

z + Cp,Yb(diket)

+ Yb(diket),

+ 2Cp,Yb + Yb(diket)3

We attempted to verify the above disproportionation reactions spectrophotometrically. Only one product, of composition Cp,Yb, was confirmed, but the mixtures of disproportionation products could not be fully characterized. Each of the twelve compounds was heated at 250-300” C in a capillary tube filled with argon for 4 hours, then cooled down, and dissolved in THF. Several peaks of the absorption spectrum of this THF solution appeared at the same wavelengths as those of the THF solution of pure Cp,Yb [5]. But, no characteristic peaks of Cp,Yb(diket), CpYb(diket), or Yb(diket), in THF solution were found in the UV/VIS spectrum. (continued on p. 374)

CWsH,,(XII)

60

2W)

163,5(d)

50

S2

Wd)

129-130

60 60

101.5

58

I-XII

gray yellow

yellow

yeIIow

yellow

yeIIow

orauge

orange

pale yellow

yeknv

orange

orahge

C&lU

58.37 (59.09)

22.99

(55.86)

(29.82)

(21.84)

56.62

29.94

(3.94)

3.71

(3.99)

3.93

1.74 (1.92)

36.65 (37.08)

26.04 (25.52)

2.69 (2.69)

40.84 (41.23)

(4.99) 4.16 (4.11)

(4.36) 6.00 (5.97) 6.66 (7.12) 2.88 (3.07) 2.37 (2.39) 4.29

4.01 (4.23) 4.03

H

33.52

44.15 (44.78) 40.79 (41.28) 51.1s (51.85) 53.3s (53.64) 39.01 (39.47) 32.48 (33.99) 50.94 (51.72) 53.54 (53.57)

C

(33.01)

43.36 (43.03) 39.95 (39.68) 35.82 (35.60) 28.91 (28.64) 38.39 (37.94) 31.78 (31.80) 37.65 (37.28) 31.64 (30.89)

Yb

Analysis ’ (Found (caIcd.)(%))

(6.76)

6.64

(4.82)

4.67

N

cm-t

1512.1571,1593

1529,1573,1585

1518,1538,1592

1510,1537,1595

1511,1567,1597

1513,1566,1598

lSS1,1581,1594

lS47,1581,1S95

IR(cm-‘) 1500-1600

E IR were recorded on a Perkia-Ehuer 983(G) (CsI crystal plate, Nujol and P’htorolube mulls) instrument. b Melting points were determiued in sealed argon-f&d cap&ties and were uncorrected. ’ Elemental analysis results were obtained on a Yanaco MT-2 anaIyr.er. The elementaf analysis data for Yb were obtained by a published method [2].

n-2

diket -~(c,H,)~~(CH,)FCaH~,

n-1 (XI)

(X)

diket =~H~CH~COCHCOCFs,

n=2

(IX)

185(d)

68

109.5 88-90

66

(IV)

87

134

60-62

M.P.(OC)’ (d = decomp.)

35

68

(III)

diket = ~H~~CH~~OCHC~F~,

diket -9 CHsCGCHCOCHs, (II) n-1 diket = (CH,),CCOCHCOC(CHs)s, n-2 diket = (CHs)&COCHCOC(CHs)s, 1 Get = CHsCGCHCOCFs, (V) n=2 d&et = CHsCGCHCOCF, (VI) n=l diket = CsHsCGCHCOCHs, (VII) n-2 diket = CsHsCGCHCGCHs, (VIII) n==l

57

40

diket = CHsCGCHCOCH,,

(I)

(%)

n-2

Yield

(CsHs)JWdiItet)a-,

AND PART bF IR DATA a FOR THE COMPOUNDS

cottlpotmds

ANALYTICAL

TABLE 1

3

(VI)

0

(IV)

(III)

(II)

(I)

(Cp = C,H,)

210,260,320

392(M-d&et);

327(M-Cp-d&et); 17W). 633( M’); 545(M); 457( M “’ ); 48O(M - Cp); 392(M - d&et); 369(M”); 327( M - Cp - diket); 174(Yb).

48O(M-Cp);

80,140,170

457(M”‘);

545(M);

17W). 633(M’);

100,130,180 210,270,320

50,100,170 200,240,310

605(M); 54O(M - Cp); 487(M “’ ); 422(M -d&et); 357(M -Cp-d&et). 605(M); 54O(M - Cp); 487( M “’ ); 422( M - d&et); 369(M”); Cp -d&et); 174cyb). 392(M -Cp); 327(M -2Cp); 239(M -Cp-diket); 174(Yb). 457(M); 392( M - Cp); 369(M”); 327( M - 2Cp); 239( M - Cp - diket);

487(M); 422 (M - Cp); 357( M - 2Cp); 239(M - Cp - diket). 723(M’); 487(M); 422(M -Cp); 369(M”); 357(M -2Cp); 239(M -Q-d&et);

174(Yb).

17W). 723(M’); 723( M’); 357( M 457(M); 633(M’);

200,250,320

50,90,180

403(M “‘ ); 174(Yb). 403(M “’ ); 369(M”);

17W). 471(M’); 471(M’);

50,100,170 200,280,320

437(M); 437(M);

403(M); 338(M - Cp); 273(M - 2Cp); 239(M - Cp - d&et); 174(Yb). 471(M’); 403(M); 369(M”); 338(M -Cp); 273(M -2Cp); 239(M -Cp-diket);

50,100,170 200,250,280

b

OF VAPORIZATION

Mainpeaks, m/e

TEMPERATURES

Temp. of vaporization ( ‘C)

AT DIFFERENT

n = 2, diket = CH,COCHCOCH,. M = Cp,Yb@iket), M’ = Yb(diket),, M” = cpyb. n = 1, diket = CHJOCHCOCH,. M= CpYb(diket)2, M’ =Yb@iket),, M” = Cp,Yb, M “’ = Cp,Yb(diket). n = 2, d&et = (CH,)pCCDCHCOC(CH,),. M = Cp,Yb(diket), M’ =Yb(diket),, M” = cp,Yb. n =l, diket = (CH,)$COCHCOCJCH,),, M = CpYb(diket)t, M’ =Yb(diket),, M” = Cp,Yb, M “’ - C&Yb(diket). n = 2, diket = CHJOCHCOCF,. M = C&Yb(diket), M’ = Yb(diket) 3r M” = Cp,Yb. n = 1, diket = CHJDCHCDCF,. M = CpYb(diket)2, M’ = Yb(diket),, M” = Cp,Yb, M “’ = CpzYb(diket).

Compounds CpJb@iket)p_, and mol. species

MS DATA“ FOR COMPOUNDS I-XII

TABLE 2

M-cpYb(diket), M’[email protected])3, M”- Q&b, M w‘ = Cp$b(diket).

M = Cp$b(diket), M’ = Yb(diket),, Au”-Cpgb n = 1, d&et - N(CsH,)N : c(CH,)cCo
100,150,180

200,280,350

100,150,180

214280,330

395(M-Cp-diket);

100~M’);79~N);728(M-Cp);663(M-2Cp);581(~”’);451(~-~p-ditret); 369(W).

1005(M’); 581(M); 516(N -Cp); 45l(M-2Cp); 369(M “’ ): 239(M-Cp-diket); 1740. 1005(M’); 793(M); 728( N - Cp); 663(M - 2Cp); 581( M “’ ); 451( A4- Cp - diket); 1740%

369( M”); 174(Yb). 837(M’); 681(M); 616(M -Cp); 525(&f “’ ); 46O(N -d&et); 395(&f-Cp-diket); 369(M”); 174(Yb. S81(M); 516(N - Cp); 451( M - 2Cp); 239(M - Cp - d&et); 174(I%).

525(M”‘); 46O(N-diket);

837(M’); 681(M); 616(M-Cp);

120,180

174(Yb).

837fM’); 525(M); 369(&f”); 304(M -d&et); 239(A4 -Cp-diket);

200,285,320

214280,320 120,170

120,180

465(M); 400 (M - Cp); 304(M - diket); 239(M - Cp - d&et); 174(Yb). 657(M’);465(M);400(M-Cp);369(~“);335(~-2Cp);239(~-~p-diket); 174w). 657(M’), 561(M); 496(M -Cp); 465(M “’ ); 4OO(M-d&et); 335(M -Cp-d&et); 174Qw 657(M’); 561(M); 465(M “‘); 4OO(M-diket); 369(M”); 174(Yb). 525(M); 46O(M-Cp); 304(M-diket); 239(M-Cp-diket); 174(Yb).

145,180 220,2lQ,320

g MS spectra were recorded on a Fhigan MAT-312 mass spectrometer. b MS data are given for the isotopes 174Yb, “S and 14N, the peak patterns correspond to theoretical valuea based on the natural abundance of isotopes.

o(H)

o(I)

M = CpYb(dike&, M’ = Yb(diket),. M” = CpJb, M “’ = Cp$b(diket). n - 2, diltet = I;r(~H,~;C(CH,)CCOC&Hs

n = 2, diket = C,H,COCHCOCHB. M = CpzYb@iket), M ’ = Yb@iket) 3, M” = cp,Yb. (VIII) n = 1, diket = ~HJOCHCOCH,. M = Cpyb(diket)2, M’ = Yb(d.iket),, M” = Cp,Yb, M “’ = CfiYb(diket). (IX) n = 2, diket = C,H=CHCH~COCHCOCFs. S M = ~Yb(diket), M’ = Yb(diket), N“ = cpgb n = 1, diket = CH==CHCH=CCOCHCOCF, (X) L---s-

(VII)

Y w

374

Bagnall [6] pointed out that the @bketonato ligand in actinoid complexes and that the $-Cp ligand in both lanthanoid and actmoid complexes are quite labile. So, it may be assumed that the lability of ligands is the cause of the disproportionation reactions. It is also possible that the disproportionation reaction takes place via an intermediate bimolecular complex in which the Cp groups are bonded in an n5-fashion to one molecule, and in an # fashion to the second molecule of the complex. The transfer of one Cp ligand from one molecule to another is probably more facile than the transfer of two ligands at the same time. So, this may be the reason why CpYb(diket), is thermally less stable than Cp,Yb(diket). Experimental All operations were performed under prepurified argon using Schlenk techniques or in a glovebox. All solvents were refhtxed and distilled over LiAlH, or sodium benzophenone under argon immediately before use. The liquid &diketones were dried over anhydrous Na,SO, and distilled under argon. The solid &diketones were dried in vacua for 4 h. Cp,Yb [7] was prepared by a published procedure.

General method of the synthesis of CpJb(diket) or CpYb(diket), To a suspension of Cp,Yb (1 equiv.) in n-hexane was added the &diketone (1 or 2 equiv.). The reaction suspension gradually turned from green to yellow under stirring at room temperature. After stirring for 20 h, the n-hexane was removed in vacua and the resulting solid was recrystalhzed from THF/n-hexane (twice) to afford Cp,Yb(diket) or CpYb(diket),. Yields, analyses and physical properties of all 12 compounds are listed in Table 1. Acknowledgement

Projects are supported by the Science Fund of the Chinese Academy of Sciences. We thank Mr. Yongfei Yu, and Mr. Baohui Du for assistance. We also thank Prof. Changtao Qian for helpful information. References G. Bielang and RD. Fischer, Inorg. Chem. Acta, 36 (1979) 1389. C. Qian, C. Ye, H. Lu, Y. Li, 3. Zhou and Y. Ge, J. Organomet. Chem., 247 (1983) 161. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, a WiIey-Interscience, 3rd. ed., 1977, p. 249-258. G.B. Deacon, G.D. FaUon, P.I. Mackkon, RH. Newnham, G.N. Pain, T.D. Tuong and D.L. Wilkinson, J. Organomet. Chem., 277 (1984) C21. F. Calderazzo, R Pappalardo and S. I_.&, J. Iuorg. Nucl. Chem., 28 (1966) 987. K.W. BagnaIl, in T.J. Marks and R.D. Fischer, (&Is.), Organometallics of the f-Elements, Reidel Publishing Co., Dordrecht, 1979, p. 221-248. J.M. Birmingham and G. Win, J. Am. Chem. Sot., 76 (1954) 6210.