J. Am. Chem. SOC.1992, 114, 160-165
160
over the two possible rotamers. Following isotropic refinement and pairwise constrained refinement of the sulfur and C12 populations, an absorption correction was applied using the DIFABS absorption correction program. Full least-squares anisotropic refinement (except for sulfur, which was isotropic) of the structure with hydrogens placed in idealized positions based upon a difference Fourier map converged with R, = 0.0363 and R2 = 0.0399.
(PMe3)(2-C,H2S-4-Me)Cl. 137038-74-5; Cp*Rh(PMe,)(2-C4H2S-4I Me)H, 136953-58-7; Cp*Rh(PMe,)(SCH=CMeCH=CH), 136953e
59-8; Cp*Rh(PMe3)(SCH=CHCMe=CH),136953-60-1; Cp*Rh(PMe3)(2-C4H2-5-Me)C1,136953-61-2; Cp*Rh(PMe3)(2-C4H2-5-Me)-
leading to this work. S.B.D. also thanks the Exxon Education Foundation for support.
Br, 136953-62-3; Cp*Rh(PMe,)(SCMe=CHCH=CH),131323-32-5; Cp*Rh(PMe3)(3-C4H3S)Br, 136953-63-4; Cp*Rh(PMe3)(3-C4H3S)H, 136953-64-5; Cp*Rh(PMe,)(2-C4H2DS)H, 136953-65-6; 2-ThLi, 2786-07-4; C4Me4S, 14503-5 1-6; thiophene, 110-02-1; 3-methylthiophene, 616-44-4; 2-methylthiophene, 554- 14-3; 3-bromothiophene, 5368-70-7; 2,5872-3 1-1; 3,4-bis(chloromethyl)-2,5-dimethylthiophene, dimethylthiophene, 638-02-8.
Registry No. 1, 81971-46-2; 2, 131323-30-3; 3, 136953-53-2; Cp*Rh(PMe3)H2,84624-03-3; Cp*Rh(PMe3)(2-C4H3S)Br,136953-543; Cp*Rh(PMe,)Br2, 88704-26-1; C P * R ~ ( P M ~ , ) ( ~ - C , H , S136953)~, 55-4; Cp*Rh(PMe3)(2-C,H,)(CI), 136953-56-5; Cp*Rh(PMe,)C12, 80298-79-9; Cp*Rh(PMe3)(2-C,H,S)(D), 136953-57-6; Cp*Rh-
Supplementary Material Available: Tables S-I-S-VI of bond distances and angles, coordinates of atoms, and anisotropic thermal parameters (7 pages); listing of calculated and observed structure factors (16 pages). Ordering information is given on any current masthead page.
Acknowledgment. Support by the National Science Foundation, Grant CHE-9102318, is gratefully acknowledged for the studies
Calorimetric Studies of the Heats of Protonation of the Metal in Fe( CO),( bidentate phosphine, arsine) Complexes: Effects of Chelate Ligands on Metal Basicity John R. Sowa, Jr., Valerio Zanotti, Giacomo Facchin, and Robert J. AngeIici* Contribution from the Department of Chemistry, Gilman Hall, Iowa State University, Ames, Iowa 5001 1 Received June 3, 1991 I
Abstract: Titration calorimetry has been used to determine the heats of protonation ( A H H M ) of F e ( C O ) 3 ( L x ) complexes ( L T = dppm, dppe, dppp, dppb, dppbz, cis-dppv, arphos, dmpm, dcpe, and diars) with CF3S03Hin 1,2-dichloroethane solution at 25.0 OC. Spectroscopic studies show that protonation occurs at the metal center to formfa~-[Fe(H)(C0)~(L?)]CF,S0~. For the series Fe(CO),[Ph2P(CH2),PPh2], n = 1-4, A H H M becomes less exothermic as the chelate size increases from n = 1 (-24.0 0.2 kcal mol-') to n = 4 (-20.1 0.2 kcal mol-'). Moreover, the chelate complexes are substantially more basic than the related nonchelate complex Fe(C0)3(PPh2Me)2(MHM = -17.6 0.4 kcal mol-'). Likewise, Fe(CO),(dmpm) is much more basic ( A H H M = -30.2 h 0.4 kcal mol-') than Fe(C0)3(PMe3)2(AHHM= -23.3 i 0.3 kcal mol-'). The higher basicities of complexes with small chelate ligands are ascribed to distortions imposed on the Fe(CO),(L>) complexes by the
*
*
chelate ligand. Basicities of several other F e ( C O ) , ( L x ) complexes are also discussed.
Introduction Bidentate phosphines and arsines are commonly used chelating ligands in transition-metal complex chemistry.' The effects of the chelates on the properties and reactivities of metal complexes have been the subject of several investigations.2 However, little (1) (a) McAuliffe, C. A. In Comprehensiue Coordination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon: New York, 1987; Vol. 2, pp 1012-1013. (b) Hayashi, T. Yuki Gosei Kaguku Kyokaishi 1983, 41, 239-250, and references therein. (c) McAuliffe, C. A.; Levason, W. Phosphine, Arsine, and Stibine Complexes of rhe Transifion Elements; Elsevier: New York, 1979; pp 212-214. (d) Alyea, E. C. In TransifionMetal Complexes of Phosphorus, Arsenic, and Antimony Ligands; McAuliffe, C. A., Ed.; Macmillan: London, 1973; Part 5. (e) Levason, W.; McAuliffe, C. A. Ado. Inorg. Chem. Radiochem. 1972, 14, 173-251. (2) (a) Minahan, D. M. A.; Hill, W. E.; McAuliffe, C. A. Coord. Chem. Rev. 1984, 55, 31-54. (b) Saburi, M.; Aoyagi, K.; Takahashi, T.; Uchida, Y. Chem. Left. 1990, 4, 601-604. (c) Kita, M.; Okuyama, A,; Kashiwabara, K.; Fujita, J. Bull. Chem. SOC.Jpn. 1990, 63, 1994-2001. (d) Camalli, M.; Caruso, F.; Chaloupka, S.; Leber, E. M.; Rimml, H.; Venanzi, L. M. Helu. Chim. Acta 1990, 73, 2263-2274. ( e ) Paviglianiti, A. J.; Minn, D. J.; Fultz, W. C.; Burmeister, J. L. Inorg. Chim. Acta 1989, 159, 65-82. (f) Kalck, P.; Randrianalimanana, C.; Ridmy, M.; Thorez, A,; tom Dieck, H.; Ehlers, J. New J . Chem. 1988, 12, 679-686. (g) Leising, R. A,; Grzybowski, J. J.; Takeuchi, K. J. Inorg. Chem. 1988, 27, 1020-1025, and references therein. (h) Mukerjee, S. L.; Nolan, S. P.; Hoff, C. D.; Lopez de la Vega, R. L. Inorg. Chem. 1988,27, 81-85. (i) Rehder, D.; K e p i , A. Inorg. Chim. Acta 1985, 103, 173-177. (j) Anderson, M. P.; Pignolet, L. H . Inorg. Chem. 1981, 20, 4101-4107. (k) Kohara, T.; Yamamoto, T.; Yamamoto, A. J . Organomef. Chem. 1980, 192, 265-274. (I) Brown, M. L.; Cramer, J. L.; Ferguson, J. A.; Meyer, T. J.; Winterton, N. J . Am. Chem. Soc. 1972,94,8707-8710. (m) Sacconi, L.; Gelsomini, J. Inorg. Chem. 1968, 7, 291-299. 0002-7863192115 14-160$03.00/0
is known of the effects of bidentate phosphine and arsine ligands on the basicities of such complexe~.~ In this paper, we examine how chelate size and basicity controls the basicities of Fe(CO),(L>) complexes, as measured by their heats of protonation (AHHM)with CF3S03Hin 1,2-dichloroethane ( D C E ) solvent at 25.0 OC (eq 1). Comparisons are made with L?&HM values of analogous monodentate phosphine complexes
c 0
1
6
J
where LnL Is P~~P(CHZ)P (dppm) P~~ PhZP(CHZhPPh2 (dppe) PhzP(CHz13PPh2 (dppp) P ~ z P ( C H Z I ~ ' P(dwb) ~Z
111
Ph2P(1.2-QHq)PPh2 (dppbJ &-Ph2P(CH=CH)PPh2 (cis-dppv) Ph2P(CH2)2AsPh2 (arphos) MCZP(CH~)PMCZ (dmpm) CmP(CH2)zPCyz (dcp) MezAS(l,Z-CkHqVIsMez (dl&
Fe(CO)3(L)2. In previous calorimetric studies of basicities were reported the heats of protonation of monophosphines (PR3),4a diphosphines," and a series of methylcyclopentadienyl complexes (3) (a) Jia, G.; Morris, R. H. Inorg. Chem. 1990.29, 581-582. (b) Chinn, M. S.; Heinekey, D. M. J . A m . Chem. SOC.1990, 112, 5166-5175. (c) Jia, G.; Morris, R. H. J . A m . Chem. SOC.1991, 113, 875-883. (4) (a) Bush, R. C.; Angelici, R. J. Inorg. Chem. 1988, 27,681-686. (b) Sowa, J . R., Jr.; Angelici, R. J. Inorg. Chem. 1991, 30, 3534.
0 1992 American Chemical Society
Fe(CO)3(bidentatephosphine, arsine) Complexes Cp'Ir(1,S-COD) (Cp' = C5Me,Hs-,, x = 0, 1, 3-5), in which protonation occurs at the Ir.5
Experimental Section All preparative reactions and manipulations were carried out under an atmosphere of nitrogen using Schlenk techniques similar to those described by McNally et a1.6 Hexanes and CH2C12were refluxed over CaH, and then distilled.' Tetrahydrofuran (THF) and diethyl ether were distilled from sodium benzophenone. Deuteriochloroform was stored over molecular sieves in air or distilled from P20s under nitrogen. The phosphine and arsine ligands were purchased from commercial sources. The IH NMR spectra were recorded in CDCI, (except as stated otherwise) on a Nicolet-NT 300 MHz spectrometer using TMS (6 = 0.00 ppm) as the internal reference. The 3'P{1H)NMR spectra were recorded in IO-mm tubes on a Bruker WM 200 NMR spectrometer in CDC13 using 85% H3P04 (6 = 0.00 ppm) as the external standard. A Digilab ITS-7 FT-IR spectrophotometer was used for recording solution infrared spectra. Mass spectra were obtained on a Finnigan 4000 instrument, and the elemental microanalysis of IH+CF3S03-was performed by Galbraith Laboratories Inc., Knoxville, TN. Synthesis of Fe(CO)3(L%). Although complexes 1: 3,1° 5," 6,12 and 109e~f~13 have been prepared previously by other methods, all of the complexes in this study were synthesized from reactions of Fe(CO),(bda)'4a (bda = benzylideneacetone) with the appropriate phosphine. The purity and characterization of each compound were established by infrared and lH NMR spectroscopies. Samples for 'H and 31P{H) NMR spectra were prepared by dissolving 10 mg of each compound in 0.5 mL of CDCI, under N2. The solutions were filtered under a nitrogen flow through a short plug of Celite (-2 X 0.5 cm) directly into an NMR tube to remove paramagnetic impurities. An additional 0.5 mL of CDCI, for 'H NMR samples and 2 mL for 31P{H)NMR samples was then passed through the column to elute any remaining compound. Fe(CO),(dppbz) (5). A solution of Fe(CO),(bda)14" (0.49 g, 1.7 mmol) in T H F (35 mL) was treated with a slight excess of 1,2-bis(dipheny1phosphino)benzene (0.85 g, 1.9 mmol). The mixture was stirred for 24 h at room temperature. At this time the IR spectrum showed three new bands (v(C0) (cm-I) T H F 1986 s, 1916 m (sh), 1903 s) for 5 and no bands corresponding to the starting material. The mixture was filtered, and the solvent was removed under vacuum. The oily residue was dissolved in a minimum of CH2CI2and chromatographed on a column of neutral alumina (15 X 3 cm, -150 mesh) with a 1:3 mixture of CH2C12/hexanes. The first yellow-orange band was collected, and the solvent was evaporated under vacuum. Recrystallization by dissolving the residue in a minimum amount of CH2C12,layering with a IO-fold volume of hexanes, and then cooling to -20 OC for -24 h afforded orange crystals of 5 (0.63 g, 64%): 'H NMR 6 7.40-7.56 (m, C6H5, C6H4);IR (CH2CI2) v ( C 0 ) (cm-I) 1985 s, 1913 m (sh), 1897 s. Data for Compounds 1-4 and 6-10. Below are given yields, reaction times, and spectral data for the other Fe(CO),(L%) complexes prepared by the above method. 2,8"39
-
( 5 ) Sowa, J. R., Jr.; Angelici, R. J. J. A m . Chem. SOC. 1991, 113, 2537-2544. (6) McNally, J. P.; Leong, U. S . ; Cocper, N. J. In Experimental Organometallic Chemistry; Wayda, A. L., Darensbourg, M. Y., Eds.; ACS Symposium Series 357; American Chemical Society: Washington, D.C., 1987; pp 6-23. (7) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals, 2nd ed.; Pergamon: New York, 1980. (8) (a) Wegner, P. A,; Evans, L. F.; Haddock, J. Inorg. Chem. 1975, 14, 192-194. (b) Cotton, F. A,; Hardcastle, K. I.; Rusholme, G. A. J. Coord. Chem. 1973, 2, 217-223. (9) (a) Cullen, W. R.; Harbourne, D. A,; Liengme, B. V.; S a m , J. R. Inorg. Chem. 1969, 8, 1464-1470. (b) Ittel, S. D.; Tolman, C. A,; Krusic, P. J.; English, A. D.; Jesson, J. P. Inorg. Chem. 1978, 17, 3432-3438. (c) Battaglia, L. P.; Delledonne, D.; Nardelli, M.; Pelizzi, C.; Predieri, G.; Chiusoli, G. P. J. Organomet. Chem. 1987, 330, 101-113. (d) Manuel, T. A. Inorg. Chem. 1963, 2, 854-858. (e) Lewis, J.; Nyholm, R. S.; Sandu, S. S.; Stiddard, J. Chem. SOC.1964, 2825-2827. (0 Cullen, W. R.; Harbourne, D. A. Can. J. Chem. 1969, 47, 3371-3378. (10) (a) Langford, G. R.; Akhtar, M.; Ellis, P. D.; MacDiarmid, A. G.; Odom, J. D. Inorg. Chem. 1975, 14, 2937-2941. (b) Akhtar, M.; Ellis, P. D.; MacDiarmid, A. G.; Odom, J. D. Inorg. Chem. 1972, 1 1 , 2917-2921. ( 1 1 ) Lin, J. T.;Lin, Y. F.; Wang, S. Y.; Sun, J. S.; Yeh, S.K. Bull. Insr. Chem. Acad. Sin. 1989, 36, 63-7 1. (12) King, R. B.;,Eggers,C. A. Inorg. Chim. Acta 1968, 2, 33-36. ( 1 3) (a) Jablonslu, C. R. Inorg. Chem. 1981.20, 3940-3947, (b) Brown, D. S.; Bushnell, G. W. Acta Crystallogr. 1967, 22, 296-299. (14) (a) Brwkhart, M.; Nelson, G. 0. J. Organomet. Chem. 1979, 164, 193-202. (b) Domingos, A. J. P.; Howell, J. A. S.; Johnson, B. F. G.; Lewis, J. Inorg. Synth. 1990, 28, 52-55.
J . Am. Chem. SOC.,Vol. 114, No. 1. 1992 161 Fe(CO),(dppm) (1): reaction time, 16 h; yield, 81%; MS (70 eV) m/e 524 (M'), 496 (M+ - CO), 468 (M+ - 2CO), 440 (M+ - 3CO); 'H NMR 6 4.22 (t, 2 H, ' J ~ H = 10.8 Hz, CHJ, 7.37 (m, Ph), 7.55 (m, Ph); 'IP{H) NMR 6 14.87 (s); IR (CH,CI,) v ( C 0 ) (cm-I) 1984 s, 1911 m (sh), 1901 s. Fe(CO),(dppe) (2): reaction time, 16 h; yield, 52%; MS (70 eV) m / e 538 (M'), 510 (M+ - CO), 482 (M+ - 2CO), 454 (M+ - 3CO); 'H NMR9a 6 2.44 (m, 4 H), 7.39-7.57 (in,Ph); 3'P{H)NMR9a 6 96.08 (s); IR (CH,CI,) v ( C 0 ) (cm-I) 1982 s, 1913 m,1892 s. Fe(CO),(dppp) (3): reaction time, 16 h; yield, 52%; MS (70 eV)1° m/e 552 (M+), 524 (M' - CO), 496 (M+ - 2CO), 468 (M+ - 3CO); IH NMR 6 1.93 (m. 2 H, CH,), 2.43 (pseudoquintet, , J H H = ,JPH = 5.2 Hz, 4 H, P(CH,)), 7.31 (m, Ph), 7.45 (m,Ph); 3'P(H)NMR" 6 46.35 (s); IR (CH2C12) v ( C 0 ) (cm-I) 1982 s, 1909 m, 1881 s. Fe(CO),(dppb) (4): reaction time, 16 h; yield, 72%; MS (70 ev) m / e 566 (M+), 538 (M+ - CO), 510 (M+ - 2CO), 482 (M+ - 3CO); ' H NMR 6 1.73 (br s, 4 H, CHI), 2.40 (br s, 4 H, P(CH2)), 7.35 (m. Ph), 7.49 (m, Ph); 3'P(H]NMR 6 57.12 (s); IR (CH,CI,) v ( C 0 ) (cm-') 1981 s, 1908 m, 1879 s. Fe(CO),(cis-dppv) (6): reaction time, 26 h; yield, 67%; lH NMR'I 6 7.38-7.50 (m,Ph), =CH not identified; IR (CH,CI,) v ( C 0 ) (cm-I) 1988 s, 1918 m (sh), 1897 s. Fe(CO),(arpbos) (7): reaction time, 16 h; yield, 55%; IH NMR 6 2.19 (dt, ,JpH = 23.9 Hz, ,JHH= 7.0 Hz, 2 H, P(CH,)), 2.47 (q, 2 J ~=H,JPH = 7.0 Hz, 2 H, As(CH,)), 7.34-7.56 (m,Ph); IR (CH2CI2)v(C0) (cm-I) 1982 s, 1910 m,I890 s. Fe(CO)3(dmpm) (8): reaction time, 16 h; yield, 53%; 'H NMR (CD2CI2,decomposes in CDCI,) 6 1.63 (t, ,JPH= 5.1 Hz, 12 H, CH3), 3.23 (t, JPH= 11.0 Hz, 2 H, CHZ); IR (CH2CI2) v ( C 0 ) (cm-I) 1978 S, 1901 m (sh), 1884 s. Fe(CO),(dcpe) ( 9 ) : reaction time, 16 h; yield, 20%; IH NMR 6 1.24-1.93 (m, Cy and CHI); IR (CH,CI,) v ( C 0 ) (cm-l) 1968 s, 1890 s (sh), 1871 s. Fe(CO),(diars) (10): reaction time, 20 h; yield, 38%; 'H NMR (CD2CI2,decomposes in CDCI,)" 6 1.67 (s, 12 H, Me), 7.67 (m,4 H, C6H4);IR (CH,CI,) v ( C 0 ) (cm-I) 1979 s, 1904 m (sh), 1885 s. Protonation Reactions. Compounds 1-10 were protonated by dissolving approximately 30 mg of each compound in 3 mL of CH2CI2under N,. To the solution was added 1 equiv of CF3S03Hby microliter syringe. Immediately the color of the solution was bleached from the yellow or orange color of the neutral complex to pale yellow or pale orange, respectively. The IR spectrum showed the complete disappearance of the bands corresponding to the starting material and appearance of new bands at higher frequency for the [Fe(H)(CO),(LI)]+ products. Solutions of the protonated complexes are fairly stable as long as they are kept under N2, but when exposed to air they readily decompose. Upon adding 1 equiv of 1,3-diphenylguanidine base in CH2CI2solvent the original color immediately reappeared as did the IR bands corresponding to the unprotonated starting material. Samples for IH NMR spectra of lH+-IOH+ were prepared by adding 1 equiv of CF3S03Hto solutions of the neutral complexes in CDC1, which were prepared as described above. Isolation of [Fe(H)(CO),(dppm)lCF3S03 (lH+CF,SOF). To a stirred solution of 1 (0.18 g, 0.34 mmol) in CH2CI2(4.0 mL) was added 1 equiv of CF3S03H. The solution was then layered with E t 2 0 (15 mL) and cooled slowly to -78 OC. It was stored at that temperature for 3 days giving pale yellow air-sensitive crystals of 1H+CF3SO< (0.18 g, 79%): ' H NMR 6 4.31 (dt, I J H ~=, 16.8 Hz, ,JpH, = 13.2 Hz, 1 H, Hc), 5.57 (m,9 lines, ,JPH, = 10.5 Hz,I5 1 H, Hb), 7.59 (m,Ph), 7.80 (m,Ph), 3.9 Hz, 1 H, Fe-H, Ha); IR (CH2C12) -6.53 (td, 'JPH= 42.6 Hz, 4 J ~ ,=~ b v ( C 0 ) (cm-') 2090 s, 2039 s. Anal. Calcd for C29H23F3Fe06P2S: C, 51.65; H, 3.44. Found: C, 51.44; H , 3.85. [Fe(H)(C0),(dppe))CF3SO3 (2H+CF3SOc): 'H NMR 6 2.68 (m, 2 H, CH,), 3.46 (m,2 H, CHI), 7.5-8.0 (m,Ph), -8.97 (t, 'JpH = 43.9 Hz, 1 H, Fe-H); IR (CH,CI,) v ( C 0 ) (cm-') 2094 s, 2042 s. [Fe(H)(CO),(dppp)rF3S03 (3H+CF3SO
