(71 M. M. Olmstead, P. P. Power, S. C. Shoner, J. Am. Chem. SOC. 113 (1991)

[8] K. Ruhlandt-Senge, P. P. Power, unpublished results. [9] P. P. Power, J . Organomet. Chem. 400 (1990) 49.

3379.

(101 W. H. Fink, J. J. Richards, J. Am. Chem. SOC. 113 (1991) 3393. [I 11 A. H. Cowley, R. A. Jones, M. A. Mardones, J. Ruiz, J. L. Atwood, S. G.

Bott, Angew. Chem. 102 (1990) 1169; Angew. Chem. fat. Ed. Engl. 29 (1990) 1150. This paper describes the structure of a four-membered Ga,P, ring compound [(2,6-(CH,NMe,),C,H,)Ga PS:Ph,], (2) with four-coor- dinate Ga and three-coordinate P centers.

(121 Crystal data for 1 at 120K (Cu,, radiation 1=1.54178 8): a=12.819(2),

90.57(1)". Z = 2 , triclinic, space group Pi, @,.,,d=1.294 g ~ m - ~ , V=4186.3(12) A3, 5251 unique observed data ( I r 2 00, R=0.091. Data were obtained on a Siemens P3R diffractometer with a locally modified LT-2 low-temperature apparatus and a rotating anode. The structure con- tains molecules of Et,O and toluene in its lattice. Further details of the crystal structure may be obtained from the Fachinformationszentrum fur Energie, Physik, Mathematik, GmbH, W-7514 Eggenstein-Leopolds- hafen 2 (FRG), on quoting the depository number CSD-55145, the names of the authors and the journal citation.

[13] Many references to the structures of the compounds of main groups 3 to 5 and their use as semiconductor precursors have been assembled in the review: A. H. Cowley, R. A. Jones, Angew. Chem. 101 (1989) 1235; Angew. Chem. In!. Ed. Engl. 28 (1989) 1028.

[I41 K . M. Waggoner, S. M. Parkin, D. C. Pestana, H. Hope, P. P. Power, J. Am. Chem. SOC. 113 (1991) 3597.

[15] M. M. Olmstead, P. P. Power, J. Organomef. Chem., in press.

b= 17.445(3). ~=20.107(3) A, a=101.10(1), 8=107.92(1), I=

One-Step Synthesis of Organolanthanide(i1) Complexes from the Metal** By Anja Recknagel and Frank T EdeImann*

The organometallic chemistry of the divalent lanthanides has developed into a fascinating research area in the past ten years."' The decamethylmetallocene derivatives of samari- um, europium, and ytterbium play a central role in this area. A prominent example is the unusually reactive THF adduct of decamethylsamarocene, [Cp*,Sm(thf),] .Iz1 This com- pound, first prepared by Evans et a]., reacts with a number of substrates to yield organosamarium(II1) complexes.[1c1 The range of novel reactions of [Cp*,Sm(thf),] stretches from the reductive CO trimeri~ation[~] through the dimeriza- tion of pho~phaalkynes[~l to the formation of the first com- plex of an f-block element containing an N, ligand.I51

Cyclopentadienyl complexes of the divalent lanthanides are usually obtained in two-step syntheses."] The reaction of lanthanide(I1) iodide with alkali cyclopentadienide has often proved its worth in the preparation of com- plexes such as [Cp*,Sm(thf),], [Cp*,Yb(Et,O)] and [{(Me,Si),C,H,},Sm(thf)] .I6] A further method is the reduc- tion of bis(cyclopentadienyl)lanthanide(III) halides with al- kali We report here on a new, direct synthesis of organolanthanide(I1) complexes from the metal, in which the organic ligand is formed in situ.

On treatment of a suspension of activated samarium or ytterbium powder in THF with two equivalents of 6,6- dimethylfulvene, the solution becomes intensely red (Yb) or violet (Sm) after an induction period of ca. 2-4 h. After further stirring for 24 h at room temperature, the metal has almost completely dissolved. The organolanthanide(I1) com-

[*I Dr. F. T. Edelmann, DipLChem. A. Recknagel Institut fur Anorganische Chemie der Universitat Tammannstrasse 4, W-3400 Gottingen (FRG)

['*I We thank Prof. Dr. H . c1! Roesky for his generous support of this work. F. T. E. thanks the Deutsche Forschungsgemeinschaft for a habilitation scholarship.

plexes 1 (Ln = Sm, 46 YO) and 2 (Ln = Yb, 75 YO yield) can be isolated from the filtered reaction solutions. Apparently the difunctional C,-bridged bis(cyclopentadieny1) ligand [Me,C,(C,H,),12@ is formed by reduction and subsequent dimerization of 6,6-dimethylfulvene during the reaction (Scheme 1). The compounds 1 (deep violet crystals) and 2

132 Scheme 1. 1: Ln = Sm, 2 : Ln = Yb.

(dark red crystals) are very air-sensitive and soluble in THF, but sparingly soluble in hexane. The EI mass spectra of the complexes exhibit a peak with high intensity for the molecu- lar ion of the unsolvated species [(Me,C,(C,H,),}Ln]. The chemical analyses and 'H NMR spectra also show that the complexes 1 and 2 contain no coordinated THE A compar- able reaction is known for the alkaline earth metals: a reaction of magnesium and 6,6-dimethylfulvene in THF/CCI, yields the bis-Grignard reagent [Me,C,(C,H,MgCI),] ' 4 THF, which in contrast to 1 and 2 is insoluble in THEt7] It is still not clear whether the heavier alkaline earth metals also react with fulvenes in a similar manner.

The new organolanthanide(I1) complexes 1 and 4 should be as reactive as their Cp* analogues. Compound 1, for example, is converted extremely easily with tert-butylchlo- ride into the organosamarium(II1) complex 3. This yellow,

1 3

thermally very stable compound was characterized by spec- troscopy and elemental analysis. The EI mass spectrum shows the molecular ion peak at m/z = 471, whose isotope pattern coincides with that calculated for C,,H,,CIOSm. The easy access to the lanthanide(I1) complexes 1 and 2 makes them attractive starting materials for organometallic synthesis. Only a small step is needed from compounds of type 3 to potentially catalytically active organolanthanide- (111) complexes.

Experimental Procedure Because of the extreme air-sensitivity of the compounds described bere, all reactions were performed under purified nitrogen in dry, oxygen-free solvents. 1 : To a suspension of Sm powder (2.00 g, 13.3 mmol) in THF (20 mL) was added HgCI, (ca. 100 mg), and the mixture was stirred for 2 h at 20 "C. Drop- wise addition of 6,6-dimethylfulvene[8] (1.41 g, 13.3 mmol) in THF (100 mL) and further stirring at room temperature for 24 h yielded a deep violet solution, which was filtered through a thin Celite layer. The filtrate was concentrated to 50 mL, and crystallization at - 25 "C afforded deep violet crystals (2.21 g. 46%). M.p. 158°C; correct elemental analysis (C,H); IR (Nujol): B[cm-'] = 1261 m, 1040s. 896111, 765s; EI-MS: mjr 364 (hi'*. 24%). 259 ([Me,C(C,H,)]Sm@, 18), 91 (MeC(C,HJe, 100); 'H NMR (80 MHz, [DJTHF): 6 = 15.5-15.0 (m, 8H, C,H,). 6.6 (s, br, vl,, = 30 Hz, 12H, Me). 2 : Analogously, a deep red crystalline solid (3.34 g, 46%) is obtained from Yb powder (2.00 g, 11.6 mmol) and 6,6-dimethylfulvene (1.22 g, 11.6 mmol). M.p. 142 "C; correct elemental analysis (C,H); IR (Nujol) Z[cm-'] = 1261 m. 1034 s, 880 m, 802 rn. 728 vs; EI-MS: m / z 386 (hi'@, 87%). 279 [Me,C(C,H,)]- Yb@, 72), 91 (MeC(C,H,)@, 100); 'H NMR (80 MHz, [D,]THF): 6 = 5.90-

Angew. Chem. In!. Ed. Engl. 30 (1991) No. 6 0 VCH Verlagsgesellsehafi mbH, W-6940 Weinheim. 1991 0570-0833/91/0606-0693 8 3.50f .25/0 693

4.42 (m, 8H, C,H,), 1.17 (s, br, v,,* = 6 Hz, 12H, Me). 3: A THF solution of 1 is prepared from Sm powder (2.00 g, 13.3 mmol) and 6.6-dimethylfulvene (1.41 g, 13.3 mmol) and treated with lBuCl (1.18 g, 12.8 mmol) directly after filtration. The mixture was stirred at room temperature for 12 h before the orange solution was evaporated to dryness. Recrystallization of the residue from toluene (ca. 30 mL) affords a yellow crystalline powder (2.50 g, 40%). which decomposes at 260 "C. Correct elemental analysis (C,H); IR (Nujol): i[cm-'] = 1258 s, 1045 s. 853 m. 785 m, 609 m; El-MS: m/z 471 (Ma, 12%), 364 ([Me,C,(C,H,),]Sme, 27), 259 ([Me,C(C,H,)]Sme, 100); 'H NMR (SOMHz, C,D,): d = 15.9 (m, 4H, THF), 8.7 (m, 4H, THF), 7.1 (m, 8H, C,H,), 1.2 (s, br, 12H, Me).

Received: January 24, 1991 [Z4400 IE] German version: Angew. Chem. 103 (1991) 720

CAS Registry numbers: 1,133165-05-6; 2,133165-06-7; 3,133165-07-8; Sm, 7440-19-9; Yb, 7440-64-4; 6,6-dimethylfulvene, 2175-91-9.

[l] Reviews: a) H. Schumann, Angew. Chem. 96 (1984) 475; Angew. Chem. Int. Ed. Engl. 23 (1984) 474; b) W J. Evans, Adv. Organomet. Chem. 24 (1985) 131; c) W. J. Evans, Polyhedron 6 (1987) 803; d) I. P. Beletskaya, G. Z. Suleimanov, MelaNoorg. Khim. 1 (1988) 3.

[2] a) W. J. Evans, I. Bloom, W. E. Hunter, J. L. Atwood, Organometulks 4 (1985) 112; b) W J. Evans, J. W. Grate, 1. Bloom, W. E. Hunter, J. L. At- wood, J: Am. Chem. SOC. 107 (1985) 3728.

[3] W. J. Evans, J. W. Grate, L. A. Hughes, H. Zhang, J. L. Atwood, J. Am. Chem. Soc. 107 (1985) 941.

[4] A. Recknagel, D. Stalke, H. W. Roesky, F. T. Edelmann, Angew. Chem. IOf (1989) 496; Angew. Chem. Int. Ed. Engl. 28 (1989) 445.

[5] W. J. Evans. T. A. Ulibarri, J. W. Ziller, J. Am. Chem. Sor. f 10 (1988) 6877. [6] W. J. Evans, R. A. Keyer, J. W. Ziller, J. Organomet. Chem. 394 (1990) 87. (71 H. Schwemmlein, H. H. Brintzinger, L Orgunomet. Chem. 254 (1983) 69. [8] W. Freiesleben, Angew. Chem. 75 (1963) 576; Angew. Chem. Inr. Ed. Engl.

2 (1963) 396.

$-Alkyl and $-Alkyl-a-Hydroxy Carbox ylic Acid Derivatives from Radical or Ionic 1,4 Addition of Dialkylaluminum Chlorides to a,$-Unsaturated N-Acyl Urethanes** By Karola Ruck and Horst Kunz*

Dedicated to Professor Leopold Horner

Chiral P-branching carboxylic acids are interesting build- ing blocks for syntheses of natural products. The same is true of P-alkyl a-hydroxy carboxylic acid derivatives, which have, in comparison with the products of aldol reactions on eno- lates, the opposite a- and P-substituent pattern. Recently we reported a new access to chiral P-alkyl carboxylic acids by 1,4 addition of dialkylaluminum halides to a$-unsaturated N-acyl urethanes.['] A particular feature of this reaction is the smooth transfer of the alkyl group to the acceptor by diethylaluminum chloride but not by dimethylaluminum chloride under the same conditions. Dimethylaluminum chloride will catalyze the 1,4 addition of higher alkyl homo- logues. In contrast to our results,"] Evans et al.rza] observed that during Diels-Alder reactions, 1,4 additions of organo- aluminum compounds do occur, but as side reactions and not only with Et,AlCl but also with Me,AlCl.

We therefore studied more closely the new reaction of the chiral oxazolidinones used by Evans on a,P-unsaturated acyl derivatives (1). Compounds 1 react with Et,AICl (2) under 1,4 addition, as do the oxazinone derivatives of xylo-

[*] Prof. Dr. H. Kunz, DipLChem. K. Ruck Institut fur Organische Chemie der Universitiit Johann-Joachim-Becber-Weg 18 -20, W-6500 Mainz (FRG)

[**I This work was supported by the Fonds der Chemischen Industrie. K. R . is grateful for a study grant from the Fonds der Chemischen Industrie and for a grant from the Adolf-Todt-Stiftung.

furanoset'] (Scheme 1). Treatment with 4 equivalents of 2 in a tolueneln-hexane solution with exclusion of oxygen at -78 "C yields the ethyl-substituted derivative 3 in high yield and with a high diastereomeric ratio in favor of the S configurated product (93 :7). Under the same conditions Me,AlCl (4) did not react, despite raised temperatures (- 20°C). In the presence of air, however, a slow reaction was observed. A useful preparative reaction is the 1,4 addi- tion of 4 to acceptors (1) on photochemical induction (A,,, = 254 nm), which yields branched P-(methyl acyl) ox- azolidinones.

f-

1 b

"*"KO Et 0 0

3 R=Ph, 98%; (S):(R)=93:1

E " * " Y O Me 0 0

5 46-63%

6 0-18%

Scheme 1. a) Et,AICI (2, 4 equiv, 1 M) in n-hexane/toluene at -78 "C under argon. b) Me,AICI (4,4 equiv) in n-hexaneltoluene, 5 h irradiation. Total reac- tion time 30-48 h.

This indicates that the methyl transfer takes place by a radical mechanism, and indeed, can be completely inhibited by 5 mol % gal~inoxyl.[~] The formation of 6 on addition of benzyl radicals also confirms the radical nature of the pro- cess. Radical reactions of the strong Lewis acid 4 with polar compounds such as 1 were till now The stereo- selectivity of the radical methyl transfer lies between 4:l and 12:l (Table 1). The separation of the diastereomeric ethyl compounds 3,15] as well as for the aromatic compounds 5 b

Table 1. Diastereoselective radical 1,4 addition of Me,AICI (4) to the acceptor 1 on irradiation for 5 h.

R (1) Tlt [a1 Prod. Yield [b] ( S ) : ( R ) [c] 6 [d]

nPr - 45/31 5a 61 19:81 Cc3, - 20148 5 b 63 88:12 10 C6H5 - 40130 5b 56 92:8 15 p-C,H,CI - 45/35 5c 46 90: 10 18 [el

[a] T = Reaction temperature [ "C], t = reaction time [h]; [b] yield [ %] after flash chromatography; [c] diasteromeric ratio determined by HPLC on RP-18 in MeOH/H,O mixtures and 'H NMR spectroscopy (400 MHz, CDCI,); [d] yield of the minor product 6 [%I; [el according to the 'H NMR spectrum (400 MHz) of the crude product 6c, the diasteromeric ratio is 82:18.

694 0 VCH Verlagsgesel~schuf~ mbH, W-6940 Weinheim, I991 0570-0833/91/0606-0694 $3.50+ ,2510 Angen'. Chem. Int. Ed. Engl. 30 (1991) No. 6