Organometallics 1995, 14, 2156-2158
2156
Bifunctional Carriers of Polar Organometallics Using Transition-Metal-Schiff Base Complexes: A Very Easy Access to Manganese(I1)-Carbon Functionalities Emma Gallo,? Euro Solari,? Carlo Floriani,*?+ Angiola Chiesi-Villa,$and Corrado Rizzoli$ Institut de Chimie MinCrale et Analytique, BCH, UniversitC de Lausanne, CH-1015 Lausanne, Switzerland, and Dipartimento di Chimica, Universita di Parma, I-43100 Parma, Italy Received February 7,199P Summary: This report details a conceptual approach to the use of bifunctional complexes for carrying ion pair reagents, such as lithium alkyls or others. This study led to the first crystallographic characterization of organometallic [Mn(Schiff base)RLi(DME)l compounds (R = CH3,2; R = Ph, 3;R = Mes (=2,4,6-Me3C&l2), 3). The importance of these complexes lies in the electronic and steric modification of lithium alkyl chemistry. Preliminary studies with PhCHO and PhCN show how complexes 2-4 react i n a bifunctional fashion with organic substrates. The unique behavior of organocupratesl as key synthons in organic synthesis is built on, among others, two major characteristics: (i)they act as carriers of lithium organometallics; (ii)they exhibit a bifunctional nature, expressed by the intervention of both lithium and copper during the reactions. Such characteristics are rarely found in other organometallic reagenh2 We tried to mimic this conceptual approach and in the meantime apply it to a transition metal undergoing a real renaissance in coordination c h e m i ~ t r yc, a~t a l y ~ i sand , ~ organometallic applications,5 namely manganese. We exploited the binding properties of metal-Schiff base
complexes which allow them to act as ligands for alkalimetal cations6 and of Mn(I1) as a metal which cannot be easily reduced in this kind of ligand e n v i r ~ n m e n t . ~ Very recently, manganese-Schiff base complexes have been tuned by Jacobsen in an elegant stereochemical approach t o obtain extraordinarily selective oxidation catalysts.8 The model complex we have considered as a carrier for polar organometallic functionalities is [Mnz(acacen)2] (1;acacen = NJV '-ethylenebis(acetylacetiminat0)dianThis compound is easily accessible in high yield and is very soluble in aromatic hydrocarbons. The dimeric structure has been determined in the solid state by an X-ray analysis and has been confirmed in solution by a molecular weight determination in benzene. R
LiR DME
___)
2
* To whom correspondence should be addressed. +
Universit6 de Lausanne.
P Universitii di Parma. @
Abstract published in Advance ACS Abstracts, April 1, 1995.
(1)(a) Lipshutz, B. H.; Sengupta, S. In Organic Reactions;Paquette, L. A., Ed.; Wiley: New York, 1992; Vol. 41, Chapter 2. (b) Lipshutz, B. H. In Organometallics in Synthesis: A Manual; Schlosser, M., Ed.; Wiley: New York, 1994; Chapter 4. (2) (a) Reetz, M. T. In Organotitanium Reagents in Organic Synthesis; Springer: Berlin, Germany, 1986. (b) Reetz, M. T.; Steinbach, R.; Westermann, J.; Peter, R.; Wenderoth, B. Chem. Ber. 1985, 118, 1441. (c) Reetz, M. T.; Wenderoth, B. Tetrahedron Lett. 1982,23, 5259. (d) Morris, R. J.; Girolami, G. S. Organometallics 1991, 10, 792. (e) Quan, R. W.; Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.; Bercaw, J . E. J . Am. Chem. SOC.1994, 116, 4489. (3) (a)Wieghardt, K. Angeur. Chem., Int. Ed. Engl. 1989,28, 1153. (b) Pecoraro, V. L.; Baldwin, M. J.; Gelasco, A. Chem. Rev. 1994, 94, 807. (4) (a) Srinivasan, K.; Michaud, P.; Kochi, J . K. J . Am. Chem. SOC. 1986, 108, 2309. (b) Menage, S.; Collomb-Dunand Sauthier, M. N.; Lambeaux, C.; Fontecave, M. J . Chem. Soc., Chem. Commun. 1994, 1885. (c) Eilmes, J. Polyhedron 1992,11,581. (d) O'Connor, K. J.;Wey, S. J.; Burrows, C. J. Tetrahedron Lett. 1992, 33, 1001. (e) Evans, D.
A.; Faul, M. M.; Bilodeau, M. T.; Anderson, B. A.; Bames, D. M. J . Am. Chem. SOC.1993, 115, 5328. (0 Reddy, D. R.; Thomton, E. R. J . Chem. SOC.,Chem. Commun. 1992, 172. (5)(a) Normant, J . F.; Cahiez, G. In Modern Synthetic Methods; Scheffold, R., Ed.; Wiley: Chichester, U.K., 1983, Vol. 3, p 173. (b) Cahiez, G.; Alami, M. Tetrahedron 1989, 45, 4163. (c) Cahiez, G.; Marquais, S. Synlett 1993, 45. (d) Cahiez, G.; Figadere, B.; Clery, P. Tetrahedron Lett. 1994, 35, 3065. (e) Cahiez, G.; Chau, K.; Clery, P. Tetrahedron Lett. 1994, 35, 3069. (0 Corey, E. J.; Posner, G. H. Tetrahedron Lett. 1970,315. (g) Reetz, M. T.; Haning, H. Tetrahedron Lett. 1993, 34, 7395. (h) Reetz, M. T.; Haning, H.; Stanchev, S. Tetrahedron Lett. 1992, 33, 6963. (i) Reetz, M. T.; RBlfing, K.; Griebenow, N. Tetrahedron Lett. 1994,35, 1969.
[Mnz(acacenh], 1
[Mn(acacen)(R){Li(DME)}J R = Me, 2 R = Ph, 3 R = Mes = 2,4,6-Me$sH2, 4
Complex 1 can be the source of the monomeric bifunctional unit [Mn(acacen)l in the presence of appropriate ion pairs. (6)(a) Floriani, C.; Calderazzo, F.; Randaccio, L. J. Chem. Soc., Chem. Commun. 1973, 384. (b) Bresciani-Pahor, N.; Calligaris, M.; Delise, P.; Nardin, G.; Randaccio, L.; Zotti, E.; Fachinetti, G.; Floriani, C. J . Chem. Soc., Dalton Trans. 1976,2310. (c)Arena, F.; Floriani, C.; Zanazzi, P. J . Chem. Soc., Chem. Commun. 1987, 183 and references therein. (7) Gallo, E.; Solari, E.; De Angelis, S.; Floriani, C.; Re, N.; ChiesiVilla, A.; Rizzoli, C. J. Am. Chem. SOC.1993, 115, 9850. (8) (a) Zhang, W.; Jacobsen, E. N. J . Org. Chem. 1991,56,2296. (b) Jacobsen, E. N.; Zhang, W.; Muci, A. R.; Ecker, J. R.; Deng, L. J. Am. Chem. SOC.1991,113,7063. (c) Larrow, J . F.; Jacobsen, E. N. J. Org. Chem. 1994,59,1939. (d) Brandes, B. D.; Jacobsen, E. N. J . Org. Chem. 1994, 59, 4378. (9) Procedure for 1: MnCly1.5THF (39.3 g, 168 mmol) was added to a THF (1000 mL) suspension of acacenNaz (45 g, 168 mmol) at room temperature. The orange suspension was refluxed for 12 h, the solvent
was evaporated to dryness, and the orange residue was recrystallized from toluene to remove NaCl and to obtain a crystalline solid (65%). Anal. Calcd for C24H36MnzN404: C, 51.99; H, 6.54; N, 10.10. Found: ~ ~295 K. C, 51.81; H, 6.62; N, 9 . 8 5 . ~= 5 . 7 8 at
0276-733319512314-2156$09.00/0 0 1995 American Chemical Society
Communications
Organometallics, Vol. 14, No. 5, 1995 2157
c34
Q c33
derivatives.12 The Mn-C bond distance is not affected by lithium coordination and is close to those of other Mn-Mes fragments.13 The binding of the lithium cation does, however, strongly reduce the 0 .O bite angle from 109.7(2)' (complex 1) to 77.9(1)'. The tetrahedral coordination around lithium is completed by DME. The short Li-01 and Li-02 distances support the premise of highly basic ligand oxygens.14 The structure of 2 is similar and also shows how the LiR reagents may be carried by a bifunctional complex. Mn(I1) does not undergo any reduction in the reaction with LiR, as it does in the corresponding Mn(II1) c0mp1ex.l~Reaction 1 represents an easily accessible route to rare organometallic derivatives of Mn(I1) which can be useful in organic synthesis. The bifunctional reactivity of 2 can be exemplified in its reaction with benzaldehyde, leading t o 5.16
C32
2 + PhCHOC3 1
&A>N,
9
Figure 1. ORTEP view of complex 4 (30% probability ellipsoids). Selected bond distances (A)and angles (deg): Mnl-Ol,2.151(2); Mnl-02,2.173(2); Mnl-N1,2.188(3); Mnl-N2,2.223(3); Mnl-C21,2.181(4); Lil-Ol,1.887(6); Lil-02,1.894(6); Lil-03,2.003(8); Lil-04,1.957(7); N1Mnl-N2, 75.8(1); 02-Mnl-N2, 83.5(1); 01-Mnl-N1, 82.5(1);01-Mnl-02, 77.9(1);01-Lil-02, 91.9(3);03Lil-04, 83.5(3); Mnl-01-Lil, 93.1(2); Mnl-02-Lil, 92.2(2). 5
-
The reaction of 1 with LiR in DME (dimethoxyethane) at -60 "C and then at room temperature gave a red solution from which the alkylated product (2-4)1° crystallized upon addition of Et2O. The proposed structures have been confirmed by X-ray analysis. Details are given only for 4.11 The structure is shown in Figure 1 with a selection of structural parameters. The [Mn(acacenll fragment has an umbrella conformation with the dihedral angles between the 0-Mn-N planes being 69.0(1)". The distance of Mn from the N202 plane (0.919(1) A) is remarkably longer than those in other five-coordinate d1-d2 [M1I1(acacen)R1organometallic
An analogous pathway can be proposed for the reaction of 2 with PhCN to give [Mn(acacen)Li(N=C(Ph)(Me)}lz (6). Complexes 5 and 6 have been hydrolyzed to the corresponding alcohol (Ph(Me)CHOH)17and ketone (Ph(Me)CO). The pathway of reaction 2 and the structure of 5 are supported by the following: (i) the reaction is slowed in the presence of 12-crown-4,which competes with the Schiff base in binding the lithium
(10) Procedure for 2: To a n orange DME (250 mL) suspension of 1 (10.01 g, 36.1 mmol) was added MeLi (20.7 mL, 36.1 mmol) in a dropwise manner at -40 "C. A red solution was obtained, which was stirred a t room temperature for 12 h. The solvent was evaporated to dryness and the orange residue treated with Et20 (150 mL). The Et20 suspension was chilled to -25 "C, yielding an orange product (76%). Crystals suitable for X-ray analysis were grown in DMEEt20. Anal. Calcd for C17H31LiMnN~04:C, 52.45; H, 8.03; N, 7.20. Found C, 52.52; H, 8.15; N, 7.27. p = 5.80 p~ at 295 K. Procedure for 3 and 4 Complexes 3 (60%yield) and 4 (70%yield) were prepared in a manner similar to complex 2. The analytical data for 3 and 4 were satisfactory. (11) Crystal data for 4: C26H39LiMnN204, triclinic, space group , pi, a = 11.004(5)A, b = 13.286(4) A, c = 9.883(2) A, a = 103.50(2)", B = 95.08(3)",y 770.36(2)",v = 1323.2(8)A3, = 2, @ealed = 1.239 g ~ m - Cu ~ ,K a radiation (1= 1.54178 A), p(Cu Ka)= 43.08 cm-', crystal dimensions 0.18 x 0.31 x 0.40 mm. The structure was solved by the heavy-atom method and anisotropically refined for all non-hydrogen atoms. The hydrogen atoms were located from a difference map and introduced as fured contributors in the last stage of refinement (Uis,,= 0.06 k). For 3278 unique observed reflections ( I > 2 d n ) collected at T = 143 K (6 < 20 < 140") and corrected for absorption the final R value was 0.045 (R, = 0.053). All calculations were carried out with use of SHELX-76 on a n Encore E91 computer. See the supplementary material for more details.
(12) Rosset, J. M.; Floriani, C.; Mazzanti, M.; Chiesi-Villa, A.; Guastini, C. Inorg. Chem. 1990,29, 3991. (13) (a) Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Chem. SOC., Chem. Commun. 1983, 1128. (b) Bartlett, R. A.; Olmstead, M. M.; Power, P. P.; Shoner, S. C. Organometallics 1988, 7, 1801. (c) Morris, R. J.; Girolami, G. S. Organometallics 1991, 10, 799. (14) Fachinetti, G.; Floriani, C.; Zanazzi, P. F.; Zanzari, A. R. Inorg. Chem. 1979,18,3469. (15) The reaction of the [Mn1Yacacen)C11 complex with a lithium alkyl afforded a crvstallomaphicallv characterized reduced product. (16) A toluene sdlution ?lo6 mL) i f 1 (1.58g, 4.06 mmol) was cooled to -70 "C, and a toluene solution (50 mL) of PhCHO (0.41 mL, 4.06 mmol) was added in a dropwise manner. The yellow solution was warmed to room temperature and stirred for 12 h. The solvent was removed and the remaining residue was treated with hexane. The yellow solid which precipitated was collected and dried in vacuo (79%). Anal. Calcd. for C40H~4Li2Mn2N406: C, 59.27; H, 6.71; N, 6.91. Found: C, 58.65; H, 6.91; N, 7.18. p = 5.78 p~ at 295 K and p = 1.75 pug a t 2 K. Complex 6 (65%yield) was prepared in a manner similar to that for complex 6. The analytical data were satisfactory. (17) The organic products from the hydrolysis of compounds 6 and 6 were obtained by quenching with HCl/H20, purified by flash chromatography, and identified by NMR and GC-MS.
S = solvent or an oxygen from an intermolecular interaction: AAA
0 N N
Oa
acacen
2158 Organometallics, Vol. 14,No. 5, 1995 cation; (ii) the dimeric compounds 5 and 6 have a reduced magnetic moment for Mn(II), as expected for an antiferromagnetically coupled dimer;18 (iii) dimers such as 5 or 6 have been structurally characterized in the reaction of [Fez(acacen)zl,isostructural with 1,with alkali-metal a1k0xides.l~ The bifunctional approach reported here for carrying polar organometallics implies the potential application of coordination compounds as catalysts in reactions involving ion pairs, such as lithium alkyls or alkali(18)Mabad, B.; Cassoux, P.;Tuchagues, J. P.; Hendrickson, D. N. Inorg. Chem. 1986,25, 1420. (19) Floriani, C.; Solari, E.; Corazza, F.; Chiesi-Villa, A,; Guastini, C. Angew. Chem., Int. Ed. Engl. 1989,28, 64.
Communications metal enolates. Our approach is now being extended to properly sterically designed Schiff base complexes of Mn(III8and to other fundamental ion pair moieties, such as the alkali-metal enolates.
Acknowledgment. We thank the Fonds National Suisse de la Recherche Scientifique (Grant No. 2033420-92) for financial support. SupplementaryMaterial Available: Tables giving crystal data and details of the structure determination, fractional atomic coordinates, thermal parameters, bond lengths, and bond angles for complex 4 (Tables 1-5) (7 pages). Ordering information is given on any current masthead page.
OM950096J
