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Medrano. J Am. Clrum. Soc. 1988. I I O , 1630: K. S. Chu, C. R. Negrete. J. P. Konopelsky. ihid. 1991, 1 / 3 , 5196; R. Rao, M. K. Gujar, B. R. Nallagandu, A Bhandari, TL.!rahedron LPI!. 1993. 34, 7085.

[S] J. Kobayashi, M. Sato, T. Murayama. M. Ishibashi. M. R. Wilchi. M Kanai. J. Shoji, Y. Ohizumi, J . CAefn. Soc. C h ~ m . Comfnim. 1991. 1050

161 N. Fusetani. T. Sugawara. S. Matsunaga. J. Am. C h i r Sot. 1991. / / 3 , 7811. 171 J. Kobayashi, F. Itagaki, H. Shigemori, M. Ishabashi. K. Takahashi. M. Ogura.

S. Nagasdwd, T Nakamura, H. Hirota, T. Ohta, S. Nozoe, J A m . C k m So(.. 1991, 113, 7812

[8] U. Schmidt, S. Weinbrenner, SJJ~I~CJ.T;.T 1996, 28. [9] U Schmidt, A. Kleefeldt, R. Mangold, J Cheni. Soc. Chern Commun. 1992.

[lo] Synthesis analogous to that of the methyl ester: J. S. Nowick, N. A Powell.

1111 H. Kunz, H. Waldmann, AII~FII. . Clrem. 1984, Y6. 49: Angtw Clienr. In! E d

[I21 We thank Prof. J. Kobayashi for providing a sample of the natural substance [I31 The measurements were kindly performed by Dr. K. Eckart at the Max-

1681.

T. M. Nguyen, G. Noronha. J. Org. Clreni 1992,57. 7364.

€ng/. 1984, 23, 71.

Planck-Institut fur experimentelle Medizin in Gottinpen.

This type of trinuclear complex possessing two highly polar metal-metal bonds is particularly rare; the only fully char- acterized and studied example is Casey's ZrRu, complex [Cp,Zr{Ru(CO),Cp),] (Cp = C5H5).[41 More recently, Palyi et al. have given a preliminary account of the generation of [Cp,Zr(Co(CO),),] by salt metathesis or alkane elimination.[51 Based on early work by Burger et we synthesized the difunctional amidozirconium complexes of the type [CH,(CH2NSiMe,),ZrC1,(D)2] (D = thf, pyridine),"] which have proved to be ideally suited for the synthesis of such trinu- clear complexes. Reaction of the complex [CH,(CH,NSiMe,),- ZrCl,(thf),] 1 with two molar equivalents of the carbonyl meta- lates K[CpM(CO),] (M = Fe, Ru) and Na[Co(CO),(PPh,)] yields the corresponding trinuclear ZrFe,, ZrRu,, and ZrCo, compounds 2-4 (Scheme 2). While both 2 and 3 are stable in

TH F

A Chelate-Amidozirconium Fragment as Building Block for Unsupported Trinuclear ZrM, Heterobimetallic Complexes (M = Fe, Ru, Co)"" Stefan Friedrich, Lutz H. Gade,* Ian J. Scowen, and Mary McPartlin

With the recent development of halide complexes with tripo- dal amido ligands, monofunctional building blocks for the gen- eration of directly metal - metal bonded M'- M heterobimetallic compounds (M' = Ti, Zr, Hf; M = late transition metal) of un- precedented stability have been made available[*, 'I and have enabled a systematic investigation into their chemical reactivi- t ~ . [ ~ ] We have now extended this strategy to the development of difunctional building blocks (Scheme I), which may be em- ployed in the synthesis of stable trinuclear complexes containing two equivalent Zr-M bonds, thus opening up the possibility of extending the cooperative reactivity of early -late hetero- bimetallic compounds to involve three complex fragments.

Scheme 1. Relationship between monofunctional and difunctional amidohalide complexes of the metals of the titanium triad used as building blocks for heteronu- clear compounds (*). Formal removal of an anionic "amido-arm" in a tridentate ligand.

['I Dr. L. H. Gade, S . Friedrich Institut fur Anorganische Chemie der Universitlt Am Hubland, D-97074 Wiirzburg (Germany)

Dr. 1. J. Scowen, Prof. M. McPartlin School of Applied Chemistry, University of North London Holloway Road, London N7 8DB (UK)

['"I This work was supported by the Deutsche Forschungsgemeinschaft (L. H. G., S. F.), the Engineering and Physical Science Research Council (M. McP , I. J. S), the Deutscher Akademischer Austauschdienst, and the British Council (ARC grant). We thank Professor Werner for his support and Degussa AG for a gift of basic chemicals.

Fax: Int. code +(931)888-4605

2

3 Scheme 2. Synthesis of the ZrM, heterobimetallic complexes 2 4

solution, the ZrCo, complex 4 slowly decomposes generating [Co(CO),(PPh,)], and an intractable Zr-containing material. The existence of metal-metal bonds in 2-4 was initially de- duced from the IR spectra, in which the v(C0) bands are shifted to higher wavenumbers relative to those of the alkali metal salts of the anions (Table I ) . It is interesting to compare the position of the asymmetric l2CO stretching vibration of 3 with that of [ C ~ , Z ~ { R U ( C O ) , C ~ ) , ] . ~ ~ ~ For 3 AV(v(CO),,) was found to be 97 cm- ' relative to the free carbonyl metalate [V(v(CO,,)) = 1896,181 1 cm- '1, while the value for Casey's ZrRu, compound is only 71 crn-'.['l The greater Lewis acidity of the amidozirco- nium fragment in comparison to that of the Cp,Zr unit appar- ently induces a higher degree of charge redistribution from the late transition metal to the early transition metal through the metal-metal bond, which therefore assumes a more covalent character.

This difference in the IR spectroscopic data should be reflect- ed in the molecular structures of the compounds. To establish such a relationship, and in order to structurally characterize a ZrFe, species for the first time, single-crystal X-ray structure analyses of 2 and 3 were carried out (Fig. The compounds are isomorphous and their gross features are identical. In each, the central Zr atom adopts a distorted terahedral coordina- tion geometry (2: N(l)-Zr-N(2) = 97.5(3), Fe(l)-Zr-Fe(2) =

116.2(1)"; 3: N(1)-Zr-N(2) = 97.6(2), Ru(l)-Zr-Ru(2) = 115.84(2)") and links to iron or ruthenium complex frag- ments through direct unsupported metal-metal bonds.

1338 .f; VCH Vrr/ug,sgesellrchafi mhH, 0-69451 Wemhrinl, I Y Y 6 0570-OR3319613512-133~ $ I5 .W+ .?5/0 Angmr Cliem In! . E d €nnl. 1996, 35. No. 12

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Table 1 . Selected spectroscopic data [a]

2:'H N M R : b = 0.43(s, IXH,SI(CH,),). 1.31 (m.2H,CH2).3.32(m,4H.CH,N). 4.56 (s. 10H. Cp); "C NMR: 6 =1.6 (S1(CH3),), 33.0 (CH,). 43.4 (CH,N). 82.8 (Cp). 216.3 (CO); IR: i.(v)(CO)) = 2005 (s), 1941 (vs). 1888 (vs)cm-' 3: 'H NMR- d = 0.48(s, lXH,Si(CH,),), 1.34(m,2H.CH2), 3.17(m.4H. CH,N). 4.91 (5. 10H. Cp): "c' NMR. 6 = 1.8 (Si(CHd3). 35.5 (CH,). 45.6 (CH2N). 85.7

7.7 Hz. 3J(Ha,Hc~") = 2.8 Hz), 3.40 (ddd, 2H, Hb. CHHN. 'J(H'.HC.") = 8.0 Hz, 3J(Hb,Hc'c') = 2.7 Hz), 4.94 (s, 5H. Cp); "CNMR: 8 = 0.4 (S1(CH3),). 38 5 (CH,), 52.1 (CHIN). 84.8 (Cp), 204.9 (CO); IR: i'(v(C0)) = 2017 (m). 1968 (vs), 1908 (VS)cm-l

7: 1~ NMR: 6 = 0.07 (s, 18H. Si(CH,),), 1.43 (m. 1 H. H'). 2.31 (m. 1 H. H"), 3.38 (Cp), 205.1 ( C O ) : IR. i'(v(C0)) =1968 (s). 1908 (s)cm" 4 : ' H NMR-i i = 0.371s. 18H,Si(CH,),),1.22(m.2H,CH,),3 39(m,4H,CH2N), 6.91-7.02.7.52-7.69(m.30H.PPh,); "C NMR: 6 = 0.9(Si(CH,),),30.2(CH2). 43.3 (CH,N). 128.9 (d. C'. 3J(P.C) ~ 1 0 . 2 Hz), 130.0 (C4), 133.5 (d. C2, 2J(P,C) = 11.6 Hz). 135 7 (d. C', 'J(P.C) = 41.4 Hz). 206.6 (br.. CO): 'lP NMR: d = 60.0; IR: I'(v(C0)) = 3042 (vw), 1962 (s). 1925 (vs), 1915 (vs)cm-' 5: * H NMR: 8 = 0.37 (s. 1XH. Si(CH,),). 1.40 (m. 1 H. H'. CHH). 2.05 (m. 1 H.

(ddd. 2H. H". 'J(H',Hh) = 14 2 Hz. 'J(H',HC ") = 5.1 Hz. 3J(Ha.H'ic') = 3.0 Hz), 3.64 (ddd, 2H. H', JJ(Hb.H"") =10.8Hz. - 'J(Hh,HC') ~ 1 . 9 Hz). 3.95 (S. 3H. NCH3),4.50(s,5H,CpFeZr),4.54(s,5H,CpFeC);"CNMR.d = OS(SI(CH,),). 41.2 (CH,), 47 0 (NCH,), 50.4 (CH,N). 80.9 (CpFeZr), 90.2 (CpFeC), 215.0 ((CO),FeC). 220.1 ((CO)?FeZr), 283.2 (C=N); IR: t(v(C0)) = 2005 (s), 1951 (s). 1924 (s). 1862 (s)cm-'

8: I H N M R : 6 = 0.04 ( s . 18H, Si(CH,),), 1 4 7 (m, 1 H. H'. CHH), 2.39 (m. H". C H H / , 3.23 (ddd. 2H. H". C m N . 2J(Hr.Hh) ~ 1 3 . 7 H z . 'J(Ha,HC") =

7.0 HZ. 'J(H".H' ) = 7.9 Hz). 3.44 (ddd. 2H. Hb, C H m . 'J(Hb.H"") = 8.8 Hz. I H , H C , CHH,, 3.34 (ddd, 2 ~ . Ha, C ~ N , 2J(H".Hh) =14,0 H ~ , 3J(H",H',C') = 5.7 H ~ , ~J(HA,H'c')= 2.9 H ~ ) . 3.64 (ddd, 2H, Hh, C H ~ , 3J(Hh,Hc,C') =

'J(Hh.H" ) = 2.5 Hr) . 4.47 (s, 5H. Cp); "C NMR: 6 = 0.4 (WCH,),). 38.4 10.4 H ~ . ~ J ( H ~ . H ' ~ ' ) = 2.0 H ~ ) . 3.89 (s, 3H. NCH,), 4.99 (s. 5H. CpRuZr), (CH,). 51 8 tCH,N). 81.8 (Cp). 215.7 (CO); IR: a(v(CO)) = 2007 (w). 1947 ( s ) . 5.01 ( s , 5H, CpRuC), I3C NMR: 6 = 0.4 (Si(CH3)3), 40.8 (CHI). 48.9 1895 ( s ) c m - ' (NCH,). 50.0 (CH,N). 84.1 (CpRuZr), 93.3 (CpRuC). 200.0 ((CO),RuC). 6: 'H NMR- 6 = 0 39 (s. 18H. Si(CH,),), 1.52 (m, 1H. H', CHH), 2.07 (m, 1H. 208.4((CO),RuZr),271.6(C=N);IR: G(v(C0)) = 2015(s). 1955(s), 1942(s). 1876 H' . CHH) , 3.21 (ddd. 2H. HA. CHHN. 'J(H".Hh) = 13.0 Hz. 3J(H",H'.'') = (s) cm- '

[a] NMR spectra recorded at 200.13 MHz (I H). 50.32 MHz ("C), and 81.03 MHz ("P) in C,D,. IR spectra were recorded in toluene. Correct eiemental analyses obtained for all compounds.

Fig 1. Crystal structures of the nearly isostructural complexes [CH,(CH,NSiMe,),Zr(M(CO),Cpj ,]. a) 2 (M = Fe). Selected bond lengths [A]: Zr-Fe(l) 2.665(2). Zr-Fe(2) 2.664(2). Zr-N(l) 2.036(7), Zr-N(2) 2.040(7). Fe(l) -C(10) 1.720( 1 1 ) , Fe( 1 ) - C(11) 1.720( 1 1 ), Fe( 1)- Cp 2.0951 10)-2.111( 1 1 ). Fe(2) --C(20) 1.733 12). Fe(2)-C(21) 1.712( 12). Fe(2)- Cp 2.086(9) - 2.121 (1 1). b) 3 (M = Ru). Selected bond lengths [A]: Zr-Ru(1) 2.7372(7). Zr-Ru(2) 2.7452(7), Zr -N( l ) 2.042(5). Zr-N(2) 2.025(5), Ru(1)-C(1O) 3.851(8). Ru(I)-C(ll)

1.846(7). Ru(2) Cp 2.255(7)-2.305(7). 1.857(9). Ruf l ) -Cp 2.258(7)-2.296(8), R~(2)-C(20) 1.841(8). Ru(2)-C(21)

The Zr-Fe distances in 2 of d[Zr-Fe(l)] = 2.665(2) and d[Zr-Fe(2)] = 2.664(2) A lie in the range between those found in [MeSi{ SiMe2N(4-CH,C,H,))Zr -Fe(CO),Cp]r31 and [CH,(CH,NSiMe ),(Cp)Zr- Fe(CO),Cp]['] [d(Fe -Zr) = 2.605(2) and 2.745(1) A, respectively]. The Zr-Ru bonds in 3 (d[Zr-Ru(l)] = 2.7372(7), d[Zr-Ru(2)] = 2.7452(7) A) are by far the shortest found in unsupported Zr-Ru complexes. The corresponding bonds in [Cp,Zr(Ru(CO),Cp),] (d[Zr -Ru(l)] 2.938(1), d[Zr-Ru(2)] = 2.948(1) and [Cp,Zr(OtBu)- Zr-Ru(CO),Cp] (d(Zr-Ru) = 2.910(1) A)r101 are significantly longer. In a theoretical study on the metal-metal bonding in Zr-M complexes Wolczanski et al. have pointed out that the Zr-M bond length critically determines the degree of metal- metal n-bonding and thus the degree of charge relocalization between the two metal centers." ' I The different positions of the 3(CO) IR bands in the amido complexes and the Cp,Zr deriva- tives is thus manifested in their structural data. The compara- tively "open" coordination of the Zr centers in 2 and 3 and, consequently, the reduced steric interaction between the fCpM(CO),) fragments in both compounds is particularly re- markable and is reflected in the rapid internal rotation around the Zr-M bonds, which is not frozen out even upon cooling NMR samples to 180 K.['']

Upon reaction of 2 and 3 with 1 in a molar ratio of 1 : 1, a quantitative complex fragment redistribution is observed that generates the dinuclear compounds 5 and 6, respe~tively."~~

2, M = Fe 1 5, M = Fe

3, M = Ru 6, M = R u

Attempts to generate a ZrFeRu heterotrimetallic complex by reacting 5 with [CpRu(CO),]- or 6 with [CpFe(CO),]- led to product mixtures in which the target compound could not be unambiguously identified. The facility of the Zr-bonded {CpM(CO),) fragment to be displaced by a nucleophile, thus

Anger. Clicwi. I I I I . Ed. En,ql. 1996, 35. No 12 c) VCH Verlugsgrsellschufi m h H , 0-69451 Welt~heini, 1994 0570-0833196;3512-1339 $ lS.iIU+ .25.:0 1339

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competing with C1-, is the underlying reason for this observa- tion. That this is indeed a kinetic phenomenon and not a conse- quence of a redistribution equilibrium of the trinuclear com- plexes is inferred from the unsuccessful attempts to generate a trimetallic species through conproportionation of 2 and 3 even upon heating such mixtures.

The stability of 2 and 3 enables the systematic investigation of the reactivity of systems containing two symmetry-related Zr-M bonds. In view of our previous studies on insertion reac- tions of polar unsaturated molecules into the Zr-M bonds of dinuclear systemsr3J it was of particular interest to assess how the transformation at one Zr-M bond would affect the other. Since in contrast to [ C ~ , Z ~ { R U ( C O ) , C ~ ) , ] , [ ~ I both 2 and 3 proved to be completely inert to CO (1 atm), we chose methyl isocyanide as substrate. Compounds 2 and 3 react with one molar equivalent of CH,NC to yield the mono-insertion prod- ucts 7 and 8, respectively, which proved to be inert towards a further equivalent of the substrate or even a large excess of it.

2, M = Fe 3, M = Ru

7, M = Fe 8, M = R u

The IR spectra of 7 and 8 display a significant shift of the v(C0) bands in comparison to those of the starting materials (Table 1): the C-bonded {CpM(CO),) fragments are shifted to higher wavenumbers and the Zr-bound (CpM(CO),) unit is shifted to significantly lower wavenumbers. The latter is partic- ularly interesting since it indicates that insertion into one Zr-M bond influences the second Zr-M bond. The charge redistribu- tion between the directly metal- metal bonded donor and accep- tor complex fragments in 7 and 8 appears to be significantly reduced and thus the residual electron density a t the (CpM(CO),) fragment greater, as reflected in the IR data.

In order to obtain detailed information of the structural con- sequences of the isocyanide insertion a crystal structure analysis of 8 was carried out (Fig. 2).[l4] Similar to the structures of 2 and 3 the central zirconium atom in 8 adopts a distorted tetrahe- dral coordination with the q2-"metallaiminoacyl ligand" occu- pying one coordination site. The most remarkable feature is the increased length of the remaining Zr-Ru bond (d[Zr- Ru(2)] = 2.8639(6) A) compared to those in the starting materi- al. The resulting reduction of the x-donor-acceptor interaction between the two metal centers is probably responsible for the higher remaining electron density a t Ru(l) , as manifested in the position of the v(C0) bands in the I R spectrum. An increase in the metal-metal bond length should imply an enhanced reactiv- ity towards a second equivalent of the substrate, a notion which apparently contradicts the observed reactive behavior. Since 7 and 8 are sterically less crowded than 2 and 3 this situation must be due to changes in the electronic structure of the compounds, an aspect we are currently investigating.

Experimental Procedure 2-4: Toamixtureofsohd [CH,(CH,NSiMe,),ZrC1,(thf),l(1)(550 mg. 1.05 mmol) and solid alkali metal carbonylate I151 toluene (20 mL) and THF (2 mL) were added at ambient temperature. After the mixture had been stirred for 1 h, Na powder (20 mg) was added to the reaction mixture. The mixture was stirred for another 2 h,

Fig. 2. Crystal structure of 8, the isocyanide insertion product of [CH,(CH,NSiMe,)2Zr{Ru(CO),Cp}z1. Selected bond lengths [A]: Zr-Ru(1) 2.8639(6), Zr-N(l) 2.066(4). Zr-N(2) 2.025(4). Zr-N(30) 2.185(4). Zr-C(30) 2.237(4), Ru(l)-C(lO) 1.858(6). Ru(1)-C(I1) 1.835(6), Ru(1)-Cp 2.274(5)- 2.309( 5 ) , Ru(2) -C(20) 1.866(6), Ru(2) - C(21) 1.865(6), Ru(2) -Cp 2.264( 14) - 2.303(8), Ru(2)-C(30) 2.040(4).

the solvent was then removed in vacuo. and the residue extracted with pentane (25 mL). After filtration, the solvent of the filtrate was again removed in vacuo, and the residue recrystallized from diethyl ether (4mL) at -78°C. Compounds 2-4 were obtained as yellow crystalline solids in yields of 37,65, and 31 %, respectively. 5. 6: Solid 2 or 3 (0.5 mmol) and 1 (260 mg. 0.5 mmol) was dissolved in C,H, (10 mL) and stirred for 24 h after which the conversion to 5 and 6, respectively, was complete. The solid products were isolated in almost quantitative yields after re- moval of the solvent in vacuo and washing of the residue with cold pentane. 7, 8 : To a solution of [CHz(CH2NSiMe,)2Zr{M(CO)2Cp)2] (M = Fe: 2. Ru. 3; 0.29 mmol) in toluene ( 5 mL) was added CH,NC (16.5 pL, 0.29 mmol). After the mixture had been stirred at room temperature for 5 min. the solvent was removed in vacuo and the solid residue extracted with diethyl ether ( 5 mL). Upon filtration the solution was concentrated to 3 mL and stored at -60°C. Compounds 7 and 8 were obtained as yellow crystalline solids in yields of 62 and 67%. respectively. The same materials were isolated in the presence of an excess of CH,NC.

Received: January 24, 1996 fZ8748IEl German version: Angew. Chem. 1996,108. 1440-1443

Keywords: heterobimetallic complexes - zirconium compounds

111 S Friedrich, H. Memmler, L. H. Gade, W.3. Li, M. McPartlin. Angew. Chem. 1994, 106,705; Angen. Chem. Inr. Ed. Engl. 1994,33,676.

121 a) M. Herberhold. G.-X. Jin. Angen. Chem. 1994,i06,1016; Angew. Chem. Int. Ed. Engl. 1994.33.964; b) D. W. Stephan. Coord. Chem. Rev. 1989, 95,41.

[3] B. Findeis, M. Schubart, C. Platzek. L. H. Gade, I. J. Scowen, M. McPartlin, Chem. Commun. 1996, 219.

[4] C. P. Casey, R. F. Jordan, A. L. Rheingold. Orgunometullics 1984, 3, 504. See also C. P. Casey. J Orgunomrr. Chem. 1990, 400, 205.

(51 T. Bdrtik, H. Windisch, A. Sorkau, K.-H Thiele, C. Kriebel, A. Herfurth, M. Tschoerner. G. Zucchi. G. Palyi, Inorg. Chim. A r i a 1994, 227, 201.

[6] a) H Burger. D Beiersdorf. 2. Anorg. Allg. Chem. 1979, 459, 111; b) K. Wiegel, H Burger, ihirl. 1976,426,301; c) D. J. Brauer, H. Burger, E. Essig, W. Gschwandtner. J Orgonomer. Chem. 1980, 190, 343; d) H. Burger, W. Gschwandtner. G. R. Liewald, ihrd. 1983. 259, 145.

[7] S. Friedrich, L H. Gade. I. J. Scowen, M. McPartlin, Organometulh 1995, 14, 5344.

[8] Fischer has pointed out that the shift of the asymmetric ' 2C0 stretching fre- quency may be viewed as a measure of the acceptor strength of the Lewis acidic metal fragment relative to the base [CpM(CO),)-: R. A. Fischer. T. Priermeier. Orgunomerallirs 1994. 13. 4306 and references therein.

191 Crystal data for 2: C,,H,,Fe,N,O,Si,Zr, M = 661.67. monoclinic. space group P2Jn. u =11.333(3). h =13.001(3). c =19.364(4) A. B = 96.58(3)". V = 2834.30 A'. 2 = 4, pFnlcd =1.551 g ~ m - ~ , F(OO0) =1352, ~ ( M O ~ . ) = 1.42 mm- ' . Yellow block-shaped crystal (0.37 x 0.32 x 0.32 mm3) in Linde-

1340 0 VCH Verlugsgesellschafi mhH, 0-69451 Weinheim. 1996 0570-0833/96/3St2-t340 3 I5 O O i ,2510 Angew. Chen?. Inr. Ed. End. 1996. 35. N o . 12

mann tube under Ar. The structure was determined by heavy atom method and refined on Ffor 2725 absorption-corrected data with I / u ( / ) > 3 from a total of 5394 reflections (O,,, 25 ) scanned on a Philips PWllOO four-circle diffrac- tometer at 295 K . Anisotropic displacement parameters applied to all non-hy- drogen atoms apart from the twofold disordered methylene group at C(9) (60:40): hydrogen atoms on Cp rings were located in difference-Fourier maps and remaining hydrogen atoms were included in idealized positions and as- signed common l',,, = 0.1 1 and 0.08 A', respectively. At final convergence R = 0 0559. R, = 0.0554 for 308 parameters. Programs: ref. [16a-c]. Crystal data for 3: (',,H,,N,O,Ru,Si,Zr. M =752.06. monoclinic. space group P2, 11. 0 = 1 1 3944(9). h=13.196(2). c=19.5280(14),& /7=96.191(5);, V=29l9 .1(6)A3. 2 = 4 . pc.,,cd=l.711 gem-', F(000)=1496, p(Cu,,)= 12.IXI mm- ' Yellow block-shaped crystal (0.48 x 0.40 x 0.40 mm') in Linde- mann tube under Ar. The structure was determined by direct methods and relined on F' for 3907 independent, absorption-corrected reflections from a total of 41 38 collected (R,,, = 0.0610, T,,, 0.386. T,,, 0.125) using a Siemens P4 diffractometer (O,,,, 56.74 ) at 293 K . Anisotropic displacement parameters were assigned for all non-hydrogen atoms apart from the twofold disordered methylene group 'it C(9) (60:40); hydrogen atoms of methylene and methyl carbon atoms were included in idealized positions and assigned U,,, = 1.2 and 1.5 times U,, of the parent carbon. respectively. At final convergence R , = 0.0379, 11 R, = 0.0961 [ / / u ( l ) > 2 ] and R , = 0.0432. II'R, = 0.2808 (all data), goodness-of-fit on F' 1.113 for 316 parameters. Programs: ref. [16d]. See also ref 114bJ.

1101 C P. Casey. R. F. Jordan. A. L. Rheingold, J Am. C/7em. Sor. 1983. 105. 665. [ l l ] G . S . Ferguson. P T. Wolczanski. L. Parkanyi. M. Zonnevylle, Orgunometul-

[l?] This i s in contrast to Casey's observations for [Cp,Zr{Ru(CO),Cpj,] in which the internal rotations around the Zr-Ru bonds could be frozen out at 180 K 141.

[I 31 The dinuclear compounds 5 and 6 may also be synthesized by reaction of 1 with one molar equivalent of K[CpM(CO),].

[14] Crystal data lor 8: C,,H,,N,O,Ru,Si,Zr. M =793.12. monoclinic. space group PZ,.L. 0=10.8252(9), h=13.0511(9),r=23089(2)A,/~ =95.720(6), V = 3245 8(4) A'. 2 = 4. pcnlcd = 1.623 gcm-'. F(O00) =1584, p(MoKJ =

1.340 m m - ' . Yellow block-shaped crystal ( 0 . 5 0 ~ 0.40 x 0.38 mm') in Linde- mann tube under Ar. The structure was determined by direct methods and refined on F' for 5665 independent, absorption corrected reflections from a total of 7245 collected (R,,, = 0.0212. Tmax 0.300, T,,, 0.233) using a Siemens P4 diffractometer (O,,, 25") a t 293 K. Anisotropic displacement parameters were assigned for all non-hydrogen atoms apart from carbon atoms of the twofold disordered Cp ring (70:30) attached to Ru(2); hydrogen atoms of methylene and methyl carbon atoms were included in idealized positions and assigned L',,, = 1.2 and I .5 limes U,, of the parent carbon. respectively. At final conver- gence R, = 0.0335. 1% R, = 0.0765 [ I / u ( I ) > 2 ] and R, = 0.0531, wR, = 0.0882 (all data). goodness-of-tit on F' 1.050 for 328 parameters. Programs. ref. [16d] b) Crystallographic data (excluding structure factors) for the structure(s) re- ported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-179-36. Copies of the data can be obtained free ofcharge on application to The Director, CCDC. 12 Union Road. Cambridge CB2 1EZ. UK (fax: int code +(1223) 336-033: e-mail: techedw chemcrys.cam.ac.uk).

1151 a ) M. Brookhart. W. B. Studabaker. R Husk, 0rgunometullir.s 1987.6, 1141; b) K . Noak. H d i , . Chin?. Acto 1964, 47, 1555; c) A. R. Manning. 1 C/zem. Sor. A 1968. I1 35, d ) D. Seyferth, M. D. Millar. J Organornet. Ciiem. 1972.38.373.

[I61 a) SHELX76: G. M. Sheldrick. University of Cambridge, 1976; b) SHELX86: G . M. Sheldrick. University of Gottingen, 1986; c) DIFABS, N. Walker, D. Stuart. A d o C',-l.trollogr. Sect. A 1983,3Y. 158; d) SHELXTL. Siemens Analyt- ical X-Ray Instruments Inc.. Madison. WI. USA, 1994.

/ir.\ 1988. 7. 1961.

COMMUNICATIONS

A Flavo-Thiazolio-Cyclophane as a Functional Model for Pyruvate Oxidase"" Patrizio Mattei and Franqois Diederich*

Pyruvate oxidase is a flavin adenine dinucleotide (FAD) and thiamine diphosphate (ThDP) dependent enzyme found in lac- tobacteria,"' whose X-ray crystal structure has recently been determined.[3] The enzyme catalyzes the reaction from pyruvate to acetyl phosphate (Scheme 1, pathway I ) . ThDP-mediated de-

CH3-CO-COOH ( I ) or ~ ~ 4 ~ 0 (11)

(R3 = CH3) (11) reaction pathway

systems

CH30H (11) Pt anode (11)

Scheme I . Catalytic cycles in the conversion of pyruvate to acetyl phosphate cata- lyzed by pyruvate oxidase (pathway I) and in the oxidation of a carboxaldehyde to a methyl ester in model systems (pathway 11).

carboxylation of pyruvate generates an active aldehyde, which is oxidized by FAD. The resulting reduced flavin (FADH,) is reoxidized by dioxygen under formation of H,O,. Finally, the 2-acetylthiazolium intermediate produced by oxidation of the active aldehyde reacts with inorganic phosphate producing the energy storage metabolite acetyl phosphate and regenerating the thiazolium ylide.

In a similar reaction sequence, aldehydes are oxidized in wa- ter or alcohols to carboxylic acids and esters, respectively (Scheme 1, pathway 11). These conversions have been catalyzed by simple thiazolium ions,141 thiazolium m i ~ e l l e s , ~ ~ ] and thiazo- lio-cyclodextrins[6~ in the presence of oxidizing agents such as n i t r o b e n ~ e n e , [ ~ ~ - ~ I ferricyanide,16] and fl avins.14'. sJ We recently reported the catalytic use of thiazolio-cyclophane 1 , which con-

[*] Prof E Diederich, DipLChem. P. Mattei Laboratorium fur Organische Chemie ETH-Zentrum Universititstrasse 16. CH-8092, Zurich (Switzerland) Fax: Int. code +(1)632-1109

[**I Catalytic Cyclophanes, Part 10. This work was supported by the Stipendien- fonds der Basler Chemischen Industrie and Hoffmann-La Roche. We thank E. Martinborough and B. Brandenberg for help with the NMR studies. Part 9: Ill.