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Lnm- NWN-Mln Hunter, A Organometallics 1991, 10, 2141-2152 2141 iterations, X:wA2[w = ~/U(F~)~,A = (IFo( - (FC()3was minimized. Note Added in Proof. After submission of this paper, Bond lengths and angles are listed in Table I. Tables I1 and I11 extended Huckel calculations on a series of binuclear represent the atomic coordinates. Further details of data collection complexes of Zr(II1) exhibiting Zr-Zr distances ranging and refinement are represented in Table 1V.- from 3.05 to 4.25 A were carried out. These calculations Acknowledgment. We thank the Alexander von suggest the existence of "a substantial amount of Humboldt Foundation for a research grant (B.M.) and the through-space metal-metal interaction at distances larger Deutsche Forschungsgemeinschaft for financial support than 3.5 A". This conclusion strongly supports ours, (Leibniz program, W.A.H.). thereby reinforcing it.% Supplementary Material Available: For 3 and 4, lists of bond lengths and angles, least-squares planes, atomic fractional (63) Kiprof, P.; Herdtweck, E.; Schmidt, R. E.; Birkhahn, M.; Maaaa, coordinates, and thermal parameters and ORTEP stereo plots (35 W. STRUX-11. A System of Computer Programs To Handle X-ray Dif- fraction Data, Technieche UniversitAt Mihchen, 1987, and Universitit pages); listings of observed and calculated structure factors (42 Marburg, 1978. pages). Ordering information is given on any current masthead (64) Frenz, B. A. ENRAF-NONIUSSDP-Plus Structure Determina- page. tion Package, version 4.0; Enraf-Nonius: Delft, Holland, 1988. (65) Keller, E. SCHAKAL. A Plot Program for Crystal Structure Illus- trations. University of Freiburg, 1988. (66) Rohmer, M.-M.; BBnard, M. Organometallics 1991, 10, 157. Novel Organometallic Complexes Containing Aromatic Azines: Synthesis and X-ray Crystal Structure of 4,6-Bis[ (q5-cyclopentadienyl)dicar bonyliron] 24Methy1thio)pyrimidine' Roxton Chukwu, Allen D. Hunter," and Bernard D. Santarsiero Department of Chemistty, University of Alberta, Edmonton, Alberta, Canada T6G 262 Received November 28, 7990 The syntheses of 13 monometallic and 4 bimetallic complexes in which (.rl5-C5H5)Fe(C0),,Fp, groups are bound to substituted pyridine, pyrazine, pyridazine, and pyrimidine rings is described. These species are prepared by metathesis reactions between the appropriate number of equivalents of NaFp and the chloro- or fluoro-substituted azine precursors in 2595% yields and structural factors affecting these yields are discussed. These new materials have been fully characterized by conventional spectroscopic techniques and are shown to contain Fe-C u-bonds. The X-ray crystal structure of the title complex (C19H,,Fe2N204; a = 11.119 (2) A, b = 11.553 (3) A, c = 15.769 (2) A, p = 104.49 (l)', V = 1960 A3; monoclinic; P2,/n; 2 = 4) confirms that it has the expected structure about the p rimidine ring. It also reveals that, contrary to expectations from frontier molecular orbital theory, the ($-C,H,)Fe(CO), group shows a preference for orientations in which its mirror plane is perpendicular to that of the pyrimidine ring. The spectroscopic data provide no evidence for the existence of any electronic interaction between the metal centers of the new bimetallic azine bridged complexes having meta substitution geometries. Introduction Work in our laboratories has recently been directed toward the investigation of the nature and degree of the long-range indirect metal-metal interaction in complexes in which two or more metal centers are bridged by arene In these species, both metals are directly u- (where ML, = (q5-C5H5)Fe(CO),,MII(CO)~, etc.). Other bonded to the arene carbon, generally in either a 1,3 or 1,4 workers have reported related studies in which the phe- fashion, e.g. nylene bridges in these complexes are formally replaced by heterocyclic ring(s) (e.g. pyrazine, 4,4'-bipyridine, etc.) (1) (a) OrganometallicComplexes with Electronic Bridges. 6. For part and where either both metals are bonded to the ring ni- 5 see ref 2e. (b) Taken in part from: Chukwu, R. MSc. Thesis, The trogen atoms by formal nitrogen to metal dative bonds, University of Alberta, 1990. Parts of this work have been presented e.g.4 orally: (c) Chukwu, R.; Hunter, A. D. 72nd Canadian Chemical Confer- ence, Victoria, BC, June 1989; Abstract 348. (d) Chukwu, R.; Hunter, A. D. 73rd Canadian Chemical Conference, Halifax, NS, July 1990,Abstract A 623IN-F14. (2) (a) Richter-Addo, G. B.; Hunter, A. D. Inorg. Chem. 1989, 28, 4063-4065. (b) Hunter, A. D. Organometallics 1989,8, 1118-1120. (c) LnM- NWN-MLn Hunter, A. D.; Szigety, A. B. Organometallics 1989,8, 267G2679. (d) Hunter, A. D.; McLemon, J. L. Organometallics 1989,8,2679-2688. (e) (where ML, = a large variety of 16-electron metal centers) Richter-Addo, G. B.; Hunter, A. D.; Wichrowska, N. Can. J. Chem. 1990, or where the metal centers are bonded by both metal- 68,41-48. (3) (a) Hunter, A. D.; Chukwu, R.; Mozol, V.; Ristic-Petrovic, D. 200th National Meeting of the American Chemical Society, Washington, DC, (4) See for example: (a) Woitellier, s.;Launay, J. P.; Spangler, C. W. Aug 1990; INOR 121. (b) Hunter, A. D.; Mozol, V. Santarsiero, B. D. 73rd Inorg. Chem. 1989,28, 758-762. (b) Gross, R.; Kaim, W. Inorg. Chem. Canadian Chemical Conference, Halifax, NS, July 1990; Abstract 614 1986,25,498-506. (c) Zulu, M. M.; Lees, A. J. Organometallics 1989,8, IN-F14. 955-960. 0276-7333/91/2310-2141$02.50/0 0 1991 American Chemical Society 2142 Organometallics, Vol. 10, No. 7, 1991 Chukwu et al. carbon and metal-nitrogen bonds, e.g.5a ration of such linkages. Given the synthetic utility2t3and well-developed chemistry of the (o5-C5H5)Fe(C0),,Fp, fragment, and considering the remarkable stability of earlier reported Fp-arene and Fp-azine complexes, we began the model studies by investigating the syntheses of W-RhCl (CO)2 a series of mono- and disubstituted azine derivatives of Fp. We considered three routes, A-C, for the syntheses of our complexes, i.e. Indeed, with the exception of substituted pyridyl com- THF ple~es,~remarkably few complexes in which a metal Route A AzX + NaFp AzFp + NaX (1) fragment is a-bonded to the ring carbon atom of a heter- ocyclic ligand have been reported! Still fewer bimetallic THF complexes with the above bonding mode, e.g. Route B (i) AzCOCl + NaFp AzCOFp + NaCl (2) ,ML" A or hv (ii) AzCOFp -AzFp + CO (3) -78 'C Route C AzLi + FpI -AzFp + LiI (4) (where Az = azine and X = F, C1, Br). We are also in- terested in these low molecular weight complexes as models (where X = C1, F and ML, = (o5-C5H5)Fe(C0),,MII(CO)~, for studying the effects of the nature of the bridging lig- etc.) have been rep~rted.~~?~ ands (e.g. their electron richness and substitution geom- We, and others, are interested in such low molecular etry) on the magnitudes of electronic interactions between weight complexes because they serve as models for target the metal centers in any polymers having such linkages. organometallic polymers containing such bridging linkages In this paper, the complete results of our synthetic and and because they are often more readily prepared and spectroscopic studies of various iron-based model com- characterized by conventional means than are the related pounds and an X-ray crystallographic study of a repre- higher molecular weight materials. Organic polymers sentative example are reported. containing heterocyclic rings have been widely studied because of their potential applications in the field of ma- Experimental Section terials sciences8 We expect that introducing organo- Unless otherwise noted, all reactions were carried out under metallic centers into the backbones of such species (e.g. anaerobic and anhydrous conditions using prepurified Ar or N2 alternating metal centers with the heterocyclic rings) will and conventional Schlenk techniquedo using the general methods substantially modify their properties and could potentially reported previously.* Reagents were purchased from commercial produce a new and interesting class of materials. More- suppliers or prepared according to standard procedures. Where over, the heteroatoms in these new polymers should be able required, chemicals used were purified before use.11 Solvents to act as further coordination sites for additional metal were dried and deaerated by standard procedures and stored under centers which would further vary the properties of the N2 or Ar.'OJ1 Thus, CHzC12and Bu20were distilled from P20s po1ymers.O and CaH2,respectively, while THF, EhO,toluene, and hexanes As an adjunct to our work with the arene-bridged sys- were distilled from sodium benzophenone ketal under an inert tems, we are particularly interested in azine-bridged model atmosphere.I2 Infrared spectra were recorded on a Pye Unicam PU9522 in- complexes and polymers having only metal-carbon u- frared spectrometer and were calibrated with the 1601-cm-l band bonds between the metal and azine fragments. As noted of polystyrene. Nuclear magnetic resonance spectra were recorded above, such complexes have been only sporadically studied on a Bruker WH-200, -300, or -400 spectrometer with reference previously and we therefore decided to begin our work in to the deuterium signal of the solvent ((CD,)aO) employed. The this area by studying systematic methods for the prepa- 'H and 13C chemical shifts are reported in parts per million (ppm) downfield from external Me,%; 19F chemical shifts are reported in parts per million (ppm) downfield from external CFCIS. (5) (a) Farizzi, F.; Sunley, C. J.; Wheeler, J. A.; Adams, H.; Bailey, N. Low-resolution mass spectra were recorded at 16 or 70 eV on an A.; Montlis, P. M. Organometallics 1990,9,131-136. (b) Booth, B. L.; AEI MS50 spectrometer at probe temperatures of 150-280 "C, Haszeldine, R. N.; Taylor, M. B. J. Chem. SOC.A 1970, 1974-1978.
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