Organometallics 1996, 14, 5013-5014
5013
The First Trifluorosilyl Hydrido Transition-Metal Compound: Metal Atom Synthesis and Structure of (g8-Toluene)bis(trifluorosilyl)ironDihydride Zhengui Yao and Kenneth J. Klabunde" Department of Chemistry, Kansas State University, Manhattan, Kansas 66506 Received July 6, 1 9 9 6 Summary: The compound ($-toluene)Fe(H)dSiFdz was synthesized from toluene-solvated iron atoms and tri fluorosilane and characterized by IH N M R spectroscopy. The crystal and molecular structures of (rf-toluene)Fe(H)z(SiFdz were determined by X-ray crystallography. There are very few well-characterized transitionmetal compounds in which the SiF3 ligand is bonded t o a transition metal. The first metal trifluorosilyl compound, F3SiCo(C0)4, was prepared by the reaction of HSiF3 with the dinuclear metal carbonyl Coz(C0)~.l Similar reactions a t 160 "C with Mnz(CO)lo,Rez(CO)lo, and [(~5-C5HdFe(CO)~1~ yielded F3SiMn(C0)5, FsSiRe(co)5,and (v~-C~H~)F~(S~F~)(CO)Z.~ A metal vapor/ plasma technique has been used to prepare some maingroup trinuorosilyl-substituted compounds, i.e., Te(SiF&, Bi(SiFd2, Sb(SiFd3, Cd(SiF&, Zn(SiF&, and Hg(siF3)~.~ Thus, metal vapors, generated by resistively heating a metal under a vacuum, were allowed to react with trifluorosilyl radicals, which were produced in a hexafluorodislane plasma, at liquid-nitrogentemperature. Most of the compounds were not stable a t room temperature, and additional stabilizing ligands were needed. In another example, a variety of methods were used to synthesize (q6-toluene)Ni(SiF3)z,and the extreme lability of the arene allowed the synthesis of some substitution derivative^.^ Recently we reported the syntheses and studies of several novel n-arene Fe(IV) compounds, by reacting "arene-solvated iron atomsn5with HSiC13.6 Herein, we extend our studies to HSiF3 and now report the synthesis and structure of the first trifluorosilyl hydrido transition-metal compound, (rlG-toluene)Fe(H)z(SiF3)z. Trifluorosilane was prepared from the reaction of HSiCl3 (10 mL, 0.1 mol), SbF3 (53.7 g, 0.3 mol), and Abstract published in Advance ACS Abstracts, November 1,1995. (1) (a) Hagen, A. P.; MacDiarmid, A. G. Inorg. Chem. 1967,6,686. (b) Hagen, A. P.; MacDiarmid, A. G. Inorg. Nucl. Chem. Lett. 1970,6, 345. (2)Schrieke, R. R.; West, B. 0. Inorg. Nucl. Chem. Lett. 1969, 5, 141. (3) (a) Bierschenk, T.R.; Guerra, M. A.; Juhlke, T. J.; Larson, S. B.; Lagow, R. J. J . Am. Chem. SOC.1987, 109, 4855. (b) Guerra, M. A.; Bierschenk, T. R.; Lagow, R. J. J . Am. Chem. Soc. 1986,108,4103. (c) Juhlke, T. J.; Braun, R. W.; Bierschenk, T. R.; Lagow, R. J. J. Am. Chem. Soc. 1979,101,3229. (d)Bierschenk,T.R.;Juhlke, T. J.; Lagow, R. J. J . Am. Chem. Soc. 1981,103,7340. (e) Guerra, M. A.; Bierschenk, T.R.; Lagow, R. J. J . Chem. SOC., Chem. Commun. 1985, 1550. (4) (a) Groshens, T.J.; Klabunde, K. J. J . Orgunomet. Chem. 1983, 259, 337. (b) Lin, S. T.;Groshens, T. J.; Klabunde, K. J. Inorg. Chem. 1984,23,1. (c) Lin, S. T.; Klabunde, K. J. Orgunomet. Synth. l983,3, 156. (d) Choe, S. B.; Schneider, J. J.; Klabunde, K. J.; Radonovich, L. J.; Ballintin, T. A. J . Orgunomet. Chem. 1989,376, 419. (5) (a) Klabunde, K. J.; Li, Y. X.; Tan, B. J. Chem. Mater. 1991, 3, 30. (b) Zenneck, U. Angew. Chem., Int. Ed. Engl. 1990,29, 126. (c) Andrews, M. P.; Ozin, G. A. Chem. Muter. 1989, I , 174. (d) Klabunde, K. J.; Efner, H.F.;Murdock, T. 0.;Ropple, R. J . Am. Chem. SOC.1976, 98, 1021. (6) (a)Yao, Z.; Klabunde, K. J.;Asirvatham,V. S. Inorg. Chem. 1995, 34,5289. (b)Asirvatham, V. S.;Yao, Z.; Klabunde, K. J. J . Am. Chem. SOC.1994, 116, 5493. @
SbC15 (5 mL, as catalyst) at room temperature for 3 h.4b,7 The resultant products were distilled through a dry ice/ acetone condenser into two traps. The first trap was at -93 "C with a toluene slush, while the second was a t -196 "C with liquid nitrogen. The second trap contained HSiF3, which was distilled onto "toluenesolvated iron atomsn5 formed by iron vapor (0.8 g) codeposited with excess toluene (90 g) at -196 "C. The matrix was warmed to -78 "C in a dry iceI2-propanol bath and held there for about 30 min followed by warming slowly to room temperature and stirring for 3 h. The reaction mixture was filtered through Celite under argon, volatiles were removed in vacuo, and the resultant yellow solid was recrystallized from a toluene/ pentane mixture t o yield light yellow crystals of ($toluene)Fe(H)~(SiF&(1%yield based on iron evaporated).
The X-ray structure shows the expected piano-stool structure for (y6-toluene)Fe(H)z(SiF3)z(Figure 118 The two SiF3 groups are trans t o each other, but no hydride was located. The bond distance between Fe and the arene C atoms range from 1.95(2)to 2.11(2) A, with the distance from the Fe to the ring (center) equal t o 1.45 A, significantly shorter than those in the Sic13 analogs (1.61 To our knowledge, this is the shortest distance between a transition metal and a coordinated arene. The toluene ligand is planar, with a maximum deviation of 0.017 8, and an average deviation of 0.011 A, similar to the Sic13 analogs, but different from predictions by extended Hiickel calculation^.^ The Si-F distances are between 1.56(1) and 1.64(1)A, similar to those in (PMe3)3Ni(SiF3)~ (1.580(8) and 1.596(9)A).3a The Fe-Si distances in (116-toluene)Fe(H)~(SiF3)~ are between 2.251(5) and 2.261(5) A, slightly longer than (7) (a) Emelbus, H.J.; Maddock, A. G. J . Chem. SOC.1944,293. (b) Booth, H. S.; Stillwell, W. D. J . Am. Chem. SOC.1934, 56, 1531. (8) (a) Crystal data: single crystals of (Vs-toluene)Fe(H)Z(SiF3)2at -160 "C are orthorhombic, space group h a 2 1 (No. 33) with u = 13.839(4)A, b = 7.582(2)A, c = 10.610(4)A, V = 1113(1)A 3 , and Z = 4 (d&d = 1.898 g/cm3, ~ ( C U Ka) = 136.27 cm-'). A total of 886 reflections (28,- = 112.7") were collected using 28/w scans with graphite-monochromateedCu Ka radiation. The structure parameters have been refined to convergence;R = 0.055, R, = 0.073 (based on F) for reflections with I > 3dI). (b) Anal. Calcd for C7H10FeF6Si2: C, 26.16,; H, 3.15; Fe, 17.44; Si, 17.55. Found: C, 24.79; H,2.94; Fe, 19.83; Si, 16.39. (9) Radonovich, L. J.; Koch, F. J.;Albright, T. A. Inorg. Chem. 1980, 19, 3373.
0276-7333/95f2314-5013$09.~0fO 0 1995 American Chemical Society
Communications
5014 Organometallics, Vol. 14, No. 11, 1995 methyl H (bound)
C(7)
C,H, (free)
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Figure 1. ORTEP drawing of (y6-toluene)Fe(H)2(SiF3)z with the atom-labeling scheme. No hydride was located. Selected bond distances (A)and angles (deg): Fe-Si(l), 2.251(5); Fe-Si(2), 2.2616); Fe-C(l), 2.11(2); Fe-C(2), 2.03(2);Fe-C(3), 1.99(2);Fe-C(4), 1.95(2);Fe-C(5), 1.97(2);Fe-C(6), 2.08(2);Si(1)-F(l), 1.56(1);Si(l)-F(2), 1.59(1);Si(l)-F(3), 1.60(1); Si(2)-F(4), 1.61(1); Si(Z)-F(5), 1.64(1);Si(2)-F(6), 1.62(1);Si(l)-Fe-Si(a), 98.2(2).
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Figure 2. 'H NMR spectrum of (y6-toluene)Fe(H)z(SiF3)2 in C,.& at room temperature, with an insert of the hydride region.
The chemical shifts of the phenyl protons are 5.14 (t), those in (y6-toluene)Fe(H)z(SiC13)2(2.222(2) and 2.2185.04 (d), and 4.73 (t)ppm, which are slightly upfield (2) A). It is well-established that n back-bonding to compared to those in (y6-toluene)Fe(H)z(SiC13)zbut phosphine and other third-row ligands involves hyperdownfield relative to those in (y6-toluene)Fe(H)z(SiF3)~. conjugative interactions between the transition metal The methyl protons are a t 1.46 (9) ppm, the same as and PR3 8 orbitals.lOJ1Fluoride is an excellent n-donor those in (~6-toluene)Fe(H)2(SiC13)z. A sextuplet for the and thus would be able to compete with iron to donate hydride was observed a t -18.71 ppm with 3 J ~ =9.6~ electrons t o the silicon. Also, the Si-F 8 orbitals are Hz, which lies between those in (y6-toluene)Fe(H)zmuch higher in energy than Si-C1 a* orbitals and (SiCl& and ($-toluene)Fe(H)~(SiF3)~. should be less accessible for n back-bonding. For these The mild fluorinating agent AgBF4 was successfully reasons, SiF3 should be a poorer n-acceptor than Sick. used to generate (q6-toluene)Ni(SiF3)2from ($-toluene)The Ni-Si distances in four-coordinate NiII-SiCla Ni(SiC13)2.4cgdWhen a toluene solution of ($-toluene)complexes are quite short as well, 2.171(3) A in Fe(H)2(SiCl& was treated with AgBF4, only a black l2 and 2.202( 1)A in cis-(co1lidine)zNi[Ni(SiC13)~C1~1~precipitate was formed; presumably Ag+ was reduced presumably due to strong n back-bonding. by the hydride. However, the Ni-Si distance of 2.182(4) A in (PMehThe stability of this type of x-arene Fe(IV) compound N i ( s i F 3 ) is ~ ~significantly ~ shorter than that in a similar apparently relies on the closed-shell 18-electron configSic13 trigonal-bipyramidal compound, (C0)3Ni(SiCl& uration, and probably the synergistic push-pull of (2.286(3) A).13 This might be due to the presence of electron density by the electron-rich arene and the three strong n-acceptor CO groups, which would comelectron-demanding a-bound ligands. When the SiF3 pete with Sic13 for d electrons from Ni. group substitutes SiC13, the hydride peak moves close The lH NMR spectrum of (y6-to1uene)Fe(H)z(SiF3)zin to 2 ppm upfield, and the chemical shifts of the phenyl C6D6 is shown in Figure 2. There are three sets of protons also move upfield, due to further loss of arosignals for the phenyl protons, a triplet at 4.93 ppm, a maticity. This indicates that more electron density is doublet a t 4.87 ppm, and a triplet at 4.49 ppm. The shifting from toluene to iron, consistent with the very peak for the methyl protons is a singlet a t 1.40 ppm. short distance between Fe and the arene (1.45 vs 1.61 ~ The hydride peak is a septet a t -19.00 ppm, with 3 J ~ - A). = 9.2 Hz, nearly 2 ppm upfield relative t o that in (y6toluene)Fe(H)z(SiC13)2. The IR spectrum showed Y F ~ - H Acknowledgment. Financial support from the Naat 1962 cm-l. tional Science Foundation is acknowledged with gratiA small amount of (y6-toluene)Fe(H)2(SiF3)(SiF2C1) tude. We thank Dr. Fusao Takusagawa for obtaining was also observed in the IH NMR in some preparations. the crystal structure. We appreciate insightful suggestions from one of the reviewers. (lO)Wheeler, R. A,; Hoffmann, R.; Strahle, J. J. Am. Chem. Soc. 1986,108,5381. (11)(a) Orpen, A. G.; Connelly, N. G. J.Chem. Sm., Chem. Commun. 1986,1310. (b) Marynick, D.S. J.Am. Chem. SOC. 1984,106, 4064. (c) Xiao, S.-X.; Trogler, W. C.; Ellis, D. E.; Berkovitch-Yellin, Z. J. Am. Chem. SOC.1983,105, 7033. (12) Brezinski, M. M.; Schneider, J . J.; Radonovich, L. J.;Klabunde, K. J. Inorg. Chem. 1989,28,2414. (13)Janikowski, S. IC;Radonovich, L. J.;Groshens, T. J.; Klabunde, K. J. Organometallics 1985,4 , 396.
Supporting Information Available: Tables of data col-
lection information, atom coordinates, bond lengths, bond angles, and anisotropic thermal parameters for ($-toluene)Fe(H)2(SiF&(4 pages). Ordering informationis given on any current masthead page. OM950518P
