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Inorg. Chem. 1987, 26, 2638-2643 Contribution from the Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
Preparation and Properties of Metal Carbonyl Teflates, Including the Structure and Reactivity of Mn(C0)5(0TeF,) Kent D. Abney, Kim M. Long, Oren P. Anderson, and Steven H. S t r a w * Received January 9, 1987 A number of metal carbonyl complexes of the teflate anion (OTeF,-) have been prepared and isolated or generated in solution, including Mn(CO),(OTeF,), Re(C0),(OTeF5), C P F ~ ( C O ) ~ ( O T ~[N(n-Bu),+] F~), [Mo(CO),(OTeF,)-1, and [N(n-Bu),+][W(CO)5(OTeF5)-]. Infrared and ''F NMR spectroscopic data provide information about the stability of the molecules, the nature of the metal-oxygen bonds, and the donor strength of teflate as compared with the halides, triflate (CF,SO,-), and perchlorate. The compound Mn(CO),(OTeF,) was studied in detail. It crystallized from dichloromethane in the orthorhombic system, space group Pna2,. Unit cell parameters are a = 12.462 (3) A, b = 7.612 (2) A, c = 12.539 (2) A, and 2 = 4. The Mn-O bond distance of 2.04 (1) 8, is indicative of a reasonably strong Mn-0 single bond. However, other structural and spectroscopic data indicate that this bond possesses a large degree of ionic character. The reactions of Mn(CO),(OTeF,) and the corresponding triflate and perchlorate complexes with tetrahydrofuran (THF) were studied. In all three cases the first-formed products were Mn(CO),(THF),(X) (X = OTeF5-, CF,S03-, C104-), formed by rate-determining CO dissociation from the parent complexes. Rate constants for CO dissociation are measurably different for the three complexes, but only vary by a factor of 10. Although teflate is a measurably stronger ligand than triflate or perchlorate, the stability and reactivity of Mn(CO),(OTeFS)are not qualitatively different from those of Mn(CO),(CF3S03) and Mn(CO),(C104). Thus, in the role as a terminal, monodentate ligand in coordinatively saturated complexes, teflate is not unique relative to other weakly basic oxyanions. Introduction In 1981 we began studying the chemistry of the pentafluoroorthotellurate anion (OTeF5-, hereafter 'referred to as teflate), especially with regard to its use as a ligand for low-valent organometallic and coordination compounds.'+' Electronically, the teflate oxygen atom was expected to be a hard, electronegative ligand. Structurally, the oxygen atom is somewhat hindered in this bulky anion, and a reduced tendency to bridge two metals plus an inability to form extended lattices was envisioned. Our goal has been to explore these unique properties of teflate in order to induce new types of reactivity of low-valent metal complexes. Other groups have studied high-valent transition-metal and main-group compounds of the OTeFS substituent and have noted a strong electronic similarity between OTeF, and fluorine.1° One impressive fact is that OTeF, forms stable compounds such as I(OTeF,),," Xe(OTeF5)6," and U(OTeF5)6,'3which have few (if any) analogues outside the corresponding fluorine derivatives. On the other hand, we have recently shown that a parallel analogy between the teflate anion and fluoride is not necessarily a good one; while a strong hydrogen bond holds the oxygen atoms together in the H(OTeF&- ion, the O--O distance is much longer than the F-F distance in the bifluoride ion, HF;, even after accounting for the different radii of oxygen and f l ~ o r i n e .The ~ teflate/fluoride comparison is important with respect to our chemistry because bonds between teflate (hard) and low-valent metals (soft) are expected to possess a large degree of ionic character. If teflate is not a pseudo-fluoride, neither is it identical with perchlorate or triflate (CF,SO,-) with respect to coordinating (1) Strauss, S. H.; Abney, K. D. Inorg. Chem. 1984, 23, 515. (2) Strauss, S. H.; Abney, K. D.; Long, K. M.; Anderson, 0. P. Inorg. Chem. 1984, 23, 1994. (3) Strauss, S. H.; Noirot, M. D.; Anderson, 0. P. Inorg. Chem. 1985, 24, 4307. (4) Strauss, S . H.; Noirot, M. D.; Anderson, 0. P. Inorg. Chem. 1986, 25, 3850. ( 5 ) Strauss, S . H.; Abney, K. D.; Anderson, 0. P. Inorg. Chem. 1986.25, 2806. (6) Miller, P. K.; Abney, K. D.; Rapp6, A. K.; Swanson, B. I.; Anderson, (7)
(8) (9)
(IO) (11) (12) (13)
0. P.; Strauss, S. H., submitted for publication in Inorg. Chem. Miller, P . K.; Pawlik, M. J.; Taylor, L. F.; Thompson, R. G.; Levstik, M. A.; Anderson, 0. P.; Straws, S.H., submitted for publication in Inorg. Chem. Colsman, M. R.; Manning, M. C.; Anderson, 0. P.; Strauss, S. H., submitted for publication in Inorg. Chem. Strauss, S . H.; Miller, P. K., unpublished data, 1985. (a) Seppelt, K. Angew. Chem., Int. Ed. Engl. 1982, 21, 877. (b) Engelbrecht, A.; Sladky, F. Ado. Inorg. Chem. Radiochem. 1981, 24, 189. (c) Seppelt, K. Acr. Chem. Res. 1979, 22, 211. Seppelt, K.; Lentz, D. Z . Anorg. Allg. Chem. 1980, 460, 5. Lentz, D.; Seppelt, K. Angew. Chem., Int. Ed. Engl. 1979, 18, 66. (a) Seppelt, K. Chem. Ber. 1976, 109, 1046. (b) Templeton, L. K.; Templeton, D. H.; Bartlett, N.; Seppelt, K. Inorg. Chem. 1976, 15, 2720.
0020-1669/87/1326-2638$01.50/0
properties. A comparison of the structures of [Ag(OTeF,)(tol),], (to1 = toluene) and [Ag(C104)(o-xyl),], (0-xyl = o-xylene), both of which contain centrosymmetric Ag2O2cores, showed that the Ag-O(OTeF5) bonds were substantially shorter (and hence stronger) than the Ag-O(C10,) bonds., Furthermore, the inability of teflate to form extended lattices leads to surprisingly high solubilities of binary metal teflates in organic solvents. For example, solutions of AgOTeF, in dichloromethane exceeding 1 M stand in contrast to the low solubility of AgC10, in this solvent, 0.6 mM.3 The compounds T10TeF54and Fe(OTeFJ2 are quite soluble in toluene and dichloromethane, respectively, whereas T1C1044and Fe(CF3S03)314are completely insoluble in these solvents. In this paper we report the preparation and the spectral and chemical properties of a variety of metal carbonyl teflates. The compound Mn(CO),(OTeF,) was studied in detail. A comparison of the coordinating properties of teflate with those of other anionic ligands is now possible for this particular class of compounds because many spectral, structural, and theoretical papers about Mn(CO),X complexes (X- = halides, carboxylates, ClO,-, CF3S03-, FS03-) have been published. The compatibility of teflate with metals in low oxidation states (0,I, 11) is now firmly established. A preliminary report of some of these findings has been publishedG2 Experimental Section General Procedures. In the following preparations and physical measurements, all operations were carried out with rigorous exclusion of dioxygen and water. Schlenk, glovebox, and high-vacuum techniques were employed, with purified dinitrogen used when an inert atmosphere was required. Reagents and Solvents. The following solvents were dried by distillation form the indicated drying agent: hexane (Na), dichloromethane (P205),dichloromethane-d2(P205),tetrahydrofuran (Na), acetonitrile (P2OJ), chloroform (PZO,). The compounds HOTeF5,s [N(n-Bu),+]Mn(C0)s(CF3S03),1S [OTeFC] AgOTeF5.CH2C12,)[AgOTeF5(tol)2]2,3
,,
CH,Mn(C0),,I6 CH3Re(C0)5,'6 C P F ~ ( C O ) ~ ( C H , ) and , ' ~ CpFe(CO)2Br17were prepared by published procedures. The compounds Mo(CO),, W(CO), (Strem), and CF3S03H(Aldrich) were used as re-
ceived. Physical Measurements. Samples for NMR spectroscopy were dichloromethane-d2solutions with 1% CFCI, and/or 1% Me,Si added. Chemical shifts (6 scale) are relative to these internal standards for I9F and IH NMR spectra. All spectra were recorded on a Bruker SY-200 (14) Haynes, J. S.; Sams, J. R.; Thompson, R. C. Can. J . Chem. 1981, 59, 669. (15) Nitschke, J.; Schmidt, S. P.; Trogler, W. C. lnorg. Cbem. 1985, 24, 1972. (16) King, R. B. Acc. Chem. Res. 1970, 3, 417. (17) Sloan, T. E.; Wojicki, A. Inorg. Chem. 1968, 7, 1268. (18) Wimmer, F. L.; Snow, M . R. A u s f . J . Cbem. 1978, 31, 267
0 1987 American Chemical Society
Metal Carbonyl Teflates Table I. Details of the X-ray Diffraction Study for Mn(C0),(0TeF5) mol formula C5F,MnO6Te mol wt 433.58 space group Pnatl 12.462 (3); 7.612 (2); 12.539 (2) unit cell: a , A; b, A; c, A unit cell vol, A3 1189.5 z 4 calcd density, g cm-3 2.42 cryst dimens, mm 0.4 X 0.3 X 0.5 data collcn temp, "C 25 Mo KCY(0.71073) radiation (A, A) monochromator graphite abs coeff, cm-l 36.35 28 range, deg 3.5-60 reflcns h, k , I 2 0 1905 no. of reflcns with I > 241) 2876 total no. of reflcns measd scan type 8-26 5-30; variable scan speed, deg min-' data/param ratio 11.7 R 0.0482 Rw 0.0527 GOF 1.342 g 1.0 x 10-3 slope of normal probability plot 1.243 spectrometer at the indicated frequencies: I9F, 188.31 MHz; 'H, 200.13 MHz. All I9F N M R spectra were AB4X patterns upfield of CFCI3 (X = '25Te,7.0% NA, I = I / & . Samples for IR spectroscopy were mulls (Nujol or Fluorolube, KBr windows) or dichloromethane or T H F solutions (0.2 mm path length Irtran-2 cells). Spectra were recorded on a Perkin-Elmer 983 spectrometer calibrated with polystyrene. Band positions are f l cm-l. Samples for ultraviolet/visible spectroscopy were dichloromethane solutions. Spectra were recorded on a Perkin-Elmer X3B spectrophotometer. Preparation of Compounds. Mn(CO)5(OTeF5). The compounds CH,Mn(CO), (0.583 g, 2.77 mmol) and HOTeF, (0.650 g, 2.71 mmol) were mixed in dichloromethane (25 mL). After 8 h all volatiles were removed from the reaction mixture, leaving an orange solid. This was recrystallized from chloroform to yield 0.790 g (67% based on HOTeFJ. 19FN M R (dichloromethane): 8, -30.8, bB -44.7, JAB = 181 Hz, JBX = 3646 Hz. The mass spectrum of this compound showed a parent ion at m / e 434. Re(CO)5(OTeF5). This compound was prepared in a fashion similar to that for Mn(CO)5(OTeF,), except that the reaction between CH3Re(CO), and HOTeF, was complete within a few minutes. Typical yields of this white compound were -75%. I9F N M R (dichloromethane): 6, -32.6, 8 B -48.7, JAB = 181 Hz, JAx = 3137 Hz, J B X = 3650 Hz. CpFe(CO)2(OTeF5). This compound was prepared in a fashion similar to that for Mn(CO)5(OTeF5), except that the reaction between CpFe(C0)2(CH3)and HOTeF5 was complete within 30 min. Typical yields of this red compound were -85%. I9F N M R (dichloromethane): 8A -29.7, 8~ -45.4, J A B = 178 Hz, JBX = 3768 Hz. IR: u(CO) 2069, 2024 c d . [N(II-BU)~+][M(CO)~(OT~F~)-] (M = Mo, W). Tetrahydrofuran (THF) solutions of M(CO), were photolyzed for 30 min with a 450-W Hg vapor lamp. An IR spectrum of the solution showed the complete disappearance of the hexacarbnyl and the formation of M(CO),(THF). Excess [N(n-Bu),+] [OTeFC] was added, resulting in a color change from yellow to brown. These complexes were unstable and could not be isolated in pure form. [N(~-BU)~*XCF~SO
