Organometallics 1994, 13, 21-23
21
Carbon Dioxide Insertion into the Fe-Zr and Ru-Zr Bonds of the Heterobimetallic Complexes Cp(CO)iM-Zr(Cl)Cpz: Direct Production of the p q l ( C):q2( O,O')-CO2 Compounds Cp(C0)2M-C02-Zr (Cl)Cp2 John R. Pinkes, Bryan D. Steffey, Jose C. Vites, and Alan R. Cutler' Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York 12180 Received October 14, 1 9 9 9 Summary: The Fe-Zr and Ru-Zr heterobimetallic compounds Cp(CO)N-Zr(Cl)Cp2incorporate carbon dioxide under mild conditions and give their respective F-ql(C): +(O,O') bimetallocarboxylates Cp(C0)2M-C02zr( Cl)Cp2. With Cp(CO)fle-Zr(Cl)Cp2,1 equivof C02or W O 2(99% labeled) quantitatively adds at above 0 "C in THF. The resulting C02 adduct, Cp(CO)&'e-CO&r(Cl)Cp2, was independently synthesized and fully characterized. Cp(CO)fle-'3C02Zr(C1)Cp2equilibrates with its isotoat room tempomer Cp('3CO)(CO)Fe-CO~Zr(Cl)Cp~ perature. Results of control experiments preclude ionization of Cp(CO)sFe-Zr(Cl)Cp2to Cp(CO)fle-/+(THflZr(CI)Cp2inorder to add C02. Operation of a C02insertion pathway that requires bifunctional activation of the C02 is discussed. Analogous Ru-Zr C02 insertion chemistry requires more forcing conditions: 3-5 atm of C 0 2 and 3 days.
The challenge of developing carbon dioxide fixation as a potential source of C1 organic feedstocks is that the limiting step often entails binding C02 a t a transitionmetal center.lI2 The electron-rich transition-metal complexes that ligate COZ irreversibly reduce it to carbon monoxide.3 These degradative processes can be circumvented by incorporating COZinto organotransition-metal systems via ligand reactions: typically "insertion" of exogenous C02 into metal-hydride and some metal-alkyl bonds to produce O-bound carboxylato compounds.6 We now report that the Fe-Zr and Ru-Zr bimetallic complexes Cp(CO)zM-Zr(Cl)Cpz (1and 2I6add C02 togive the stable Abstract published in Aduance ACS Abstracts, December 1, 1993. (1) Reviews on COa complexes: (a) Catalytic Activation of Carbon Dioxide; ACS Symposium Series 363; Ayers, W. M., Ed.; American Chemical Society: Washington, DC, 1988. (b) For recent tabulations of COa complexes, see: Tanaka, H.; Tzeng, B.-C.; Nagao, H.; Peng, S.-M.; Tanaka, K. Inorg. Chem. 1993,32,1508. Gibson, D. H.; Ong, T.-S.; Ye, M. Organometallics 1991, 10, 1811. (2) Reduction of COz by electrocatalysis or photoelectrocatalysis/ photochemical activation of COn may engender COSbinding and ligand reactions at transition-mete1 centers: (a) Hammouche, M.; Lexa, D.; Momentau, M.; S a v h t , J.-M. J. Am. Chem. Soc. 1991,113,8455. (b) Bruce, M. R. M.; Megehee, E.; Sullivan, B. P.; Thorp, H. H.; OToole, T. R.; Downard, A.; Pugh, J. R.; Meyer, T. J. Znorg. Chem. 1992,31,4864. (3) Recent examples include t h e following. (a) Reductive disproportionation: Alvarez,R.; Atwood, J. L.; Carmona, E.; PBrez, P. J.; Poveda, M. L.;Rogers, R. D. Inorg. Chem. 1991,30,1493. (b) Oxygen atom abstraction: Fu, P.; Khan, M. A.; Nicholas, K. M. Organometallics 1992,11,2607. Hall, K. A.; Mayer, J. M. J. Am. Chem. SOC. 1992,114, 10402. (4) Examples of homogeneoua catalytic hydrogenation*b and hydrosilationk of COS: (a) T&, J.-C.; Nicholas, K. M. J.Am. Chem. SOC. 1992, 114,5117. (b)Graf,E.;Leitner, W. J. Chem.Soc., Chem. Commun. 1992, 623. (c) Eiaenrrchmid, T. C.; Eisenberg, R. Organometallics 1989, 8, 1822. (5) Selectdexamplee: (a) Sullivan,B. P.; Meyer,T. J. Organometallics 1986,5,1600. (b) Darenebourg, D. J.; Wiegreffe, H. P.; Wiegreffe, P. H. J. Am. Chem. SOC. 1990,112,9252. (c) Darensbourg, D. J.; Hanckel, R.
K.; Bauch, C. G.; Pala, M.; Simmone, D.; White, J. N.J. Am. Chem. SOC. 1985,107,7463. (d) Darensbourg, D. J.; Pala, M. J.Am. Chem. SOC. 1985,
107, 5887.
bimetallocarboxylates Cp(C0)2M-C02-Zr(Cl)Cp2 (3 and 4) (eq l),which represent the first examples of inserting CO2 into transition-metal-transition-metalbonds.
oc
co
-
(1 5.5 atm.)
3, M -Fe: 4 , M I k
The carbon dioxide complexes3 and 4 typify an emerging theme that heterobimetallic complexes facilitate the Our recently binding of CO2 at transition-metal reported RuZr C02 complex Cp(C0)2Ru-CO2-Zr(Cl)Cp2 (4),'0 for example, is much more stable than its metallocarboxylate precursor, Cp(C0)2Ru-CQ2-K+. This stabilization is associated with an electronic "push-pull" that results from coupling electron-rich ruthenium and oxophilic zirconium moieties1' through the c(.q1(C):q2(0,0') carboxylate bridge. Continuing these studies on late-early bimetallic C02 complexes required reproducibly synthesizing and fully (6) (a) Casey, C. P.; Jordan, R. F.; Rheingold, A. L. J. Am. Chem. SOC. 1983, 105, 665; Organometallics 1984, 3, 504. (b) Casey, C. P. J. Organomet. Chem. 1990,400, 205. (7) Bifunctional activation of COz, L.M-COrM', was established for
ion pairing anionic metallocarboxylates L.MCO2- to alkali- or alkalineearth-metal counterions (M')+:lb$ (a) Gambarotta, S.;Arena, F.; Floriani, C.; Zanazzi, P. F. J. Am. Chem. SOC. 1982,104,5082. Floriani, C. Pure Appl. Chem. 1983,55, 1. (b) Bianchini, C.; Meli, A. J. Am. Chem. SOC. 1984,106,2698. (c) Schmidt, M. H.; Miskelly, G. M.; Lewis, N. 5.J. Am. Chem. SOC. 1990,112, 3420. (d) Group 1 and 2 counterione influence metal alkyl402 ineertionsbbandcatalytic electrochemicalCOz reduction by Fe(0) porphyrins." (8) Cutler, A. R.; Hanna, P. K.; Vites, J. C. Chem. Reu. 1988,88,1363. (9) Examples of bimetallic COz complexes retaining only organotransition-metal groups: (a) Gibson, D. H.; Ye, M.; Richardson, J. F. J. Am. Chem. SOC.1992, 114, 9716. (b) Pilato, R. S.;Housmekerides, C. E.; Jernakoff, P.; Rubin, D.; Geoffroy,G. L.; Rheingold,A. L. Organometallics 1990, 9, 2333. (c) Houemekerides, C. E.; Ramage, D. L.; Kretz, C. M.; Shontz, J. T.; Pilato, R.S.; Geoffroy, G. L.; Rheingold, A. L.; Haggerty, B. S. Znorg. Chem. 1992,31,4453. (d) Szalda, D. J.; Chou, M. H.; Fujita, E.; Creutz, C. Znorg. Chem. 1992,31, 4712 and references therein. (10) (a) Vites, J. C.; Steffey, B. D.; Giuseppetti-Dery, M. E.; Cutler, A. R. Organometallics 1991,10,2827. (b)Steffey, B. D.; Vites, J. C.; Cutler, A. R. Organometallics 1991, 10, 3432. (11) Recent examples of FeZr or RuZr hetarobimetallic complexeswith bridging ligands: (a) Berno, P.; Floriani, C.; Chiesi-Villa,A.;Guastini, C. Organometallics 1990,9,1995. (b)Lemke, F. R.; Szalda, D. J.; Bullock, R. M. J. Am. Chem. SOC. 1991,113,8466; Organometalhcs 1992,11,876. Lemke, F. R.; Bullock, R.M. Organometallics 1992,11,4261. (c) Reviews on heterobimetallic chemistry: Stephan, D. W. Coord. Chem. Reu. 1989, 95,41. Bullock, R. M.; Casey, C. P. Acc. Chem. Res. 1987,20,167.
0276-7333/94/2313-0021$04.50/ 0 0 1994 American Chemical Society
Communications
22 Organometallics, Vol. 13, No. 1, 1994
characterizing the Fe-Zr bimetallocarboxylates Cp(CO)nFe-COrZr(Cl)Cpz (3) and Cp(C0)2Fe-WOrZr(Cl)Cp2 (38) (eq 2). The Fe-Zr C02 adduct 3 had been
-
e Fe
C%
-Na'
/\
oc co
43 ? , Fe- Ckf/\
: co
Na'
O
reportedlO" as an impure material; it now was obtained analytically pure after a prompt workup involving removal of the THF.12 Although stable as a solid, THF solutions of 3 at room temperature degraded to [CpFe(CO)zlzand [Cp2(Cl)ZrIzOwith a half-life ( T 1 p ) of 4.0 h. IR spectral carboxylate u(C02) assignments for 3, which define a chelating q2(0,0')metallocarboxylate structure,lO were confirmed by comparison with those for 3a. In addition to ita solution degradation, 3a more rapidly (71p = 1.5 h) exchanges the l3C label between the carboxylate and terminal carbonyl sites (eq 3).13 The resulting isotopomer Cp(lSCO)(CO)Fe-CO~-Zr(C1)Cp~ (3b)14 is presumably derived from equilibrium concentrations of the metalloanhydride species depicted in eq 3.
-
3.
eFe
13 CO
(3)
Incorporating carbon dioxide into the Fe-Zr bond of Casey's heterobimetallic compound Cp(CO)zFe-Zr(Cl)Cp2 (1) proved to be surprisingly straightforward.16 Treatment of a THF solution of 1above 0 "C with 1equiv of C02 quantitatively converted it to Cp(C0)2Fe-C02Zr(C1)Cpz (3) (eq 1). Also evident in these reaction (12) A THF solution containing Cp(CO)zFeCOz-K+(1.00 mmol) was generated using 1.0 equiv of C02 (-196 to -78 "C) on a high-vacuum line1&and wan treated with CplZrClz(-78 "C). Rapid workup involving evaporation of THF and reprecipitation from benzene-hexane afforded Cp(C0)2FeCO&r(Cl)Cpl (3) (80% yield) ae a stable, pale yellowish 1363,v,(COz) white solid. IR (THF): v(C0) 2032,1977cm-1; v,(COZ) 1283 cm-l. lH NMR (C&: 6 6.09 (8, CplZr), 4.15 (8, CpFe). lBC(lH) N M R (CDCla): 6 229.2 (F&0),212.6 @-C02),114.0 (CplZr),85.9 (CpFe). Anal. Calcd for C10H1~04CWeZr.C, 45.26; H, 3.16. Found C, 45.40; H, 3.05. Reeulta using 99% '=-labeled COZ: Cp(CO)&-WOrZr(Cl)Cpz (So). IR (THF): v(C0) 2031,1977 m-1;u,(COI) 1330, v,(COz) 1258 cm-1. Once removed from THF, 3 is stable an a solid or even in benzene solution;
