Organometallics 1996, 14, 2253-2264
2253
Addition and Substitution Reactions and Structures of Heterobimetallic Phosphido-Bridged Fe-W Complexes-Adjacent Metal Assisted Substitution and Reaction Site Switching via Metal-Metal Bond Formation Shin-Guang Shyu," Pei-Jung Lin, Kuan-Jiuh Lin, Ming-Chi Chang, and Yuh-Shang Wen Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan, Republic of China Received October 6,1994@ The metal-metal bond in CpFe(CO)@-PPh2)@-CO)W(CO)4(1)was cleaved by Lewis bases L (L = PMe3, PPh2H, CH3CN) to produce CpFe(CO)z@-PPhz)W(C0)4L (31, in which L regioselectively and stereospecifically coordinates to W cis to the phosphido bridge. When L was PPh3 or P(OMe)3, both cis and trans isomers were obtained. When CpFe(CO)z@PPh2)W(C0)5(2) reacted with PMe3, one CO ligand on Fe was replaced by PMe3 to produce CpFe(CO)(PMe3)@-PPh2)W(C0)5(4). Structures of CpFe(C0)2@-PPhz)W(C0)4(PMe3)(3bcis), CpFe(CO)&-PPh2)W(CO)4(P(OMe)3)(3c-trans),and 4 were determined by single-crystal X-ray diffraction studies. Crystal data for 3b-cis: C26H#eO&W, space group P21/c, a = 9.832(4) b = 16.027(3) c = 18.264(4) A, p = 103.87(2)", V = 2794(1) Hi3, and 2 = 4. The structure was refined to R = 0.026 and R, = 0.031. Crystal data for 3c-trans: C26H24FeOsPzW, space group Pna21, a = 22.779(4) b = 11.669(2) c = 10.580(1) V = 2812.7(7) Hi3, and 2 = 4. The structure was refined to R = 0.023 and R, = 0.026. Crystal data for 4: C26&4FeO6P2W, space group P21/n, a = 15.768(2) b = 10.7111(2) C = 17.784(2) p = 114.10(1)', V = 2741.8(7) A3, and 2 = 4. The structure was refined to R = 0.021 and R, =
A,
A,
A,
A,
A,
A,
A,
A,
0.024. W irradiation of 3 removed one CO to form CpFe(CO)@-PPh2)W(CO)qL(5). The structure of CpFe(CO)(p-PPh2)W(C0)4(PPh3) (5e-trans)was determined by a single-crystal X-ray diffraction study. Crystal data for Be-trans: C ~ O H ~ O F ~ Ospace ~ P ~grou W , P21/c, a = 18.6696(8) b = 12.6178(6) c = 18.195(1) p = 118.220(5)', V = 3777.5(3) and 2 = 4. The structure was refined to R = 0.028 and R, = 0.030.
A,
A,
Introduction In bimetallic phosphido-bridgedcomplexes, one metal may exert an activating influence on the adjacent meta1.l We recently reported that the metal-metal bond in the heterobimetallic phosphido-bridged complex
-
CpW(C0)2@-PPh2)Mo(C0)5activated the Mo carbonyl ligand toward substitution by Lewis bases L (L= PMe3, PPhzH, P(OMe)3) at ambient temperatures via the opening of the metal-metal bond to produce CpW(CO)3@-PPhz)Mo(CO)rLwith the intramolecular transfer of one Mo carbonyl t o the adjacent W.la For the complex I
CpW(CO)&PPh2)W(C0)5, similar activation of the W carbonyl toward substitution by Lewis bases L by the adjacent metal through the metal-metal bond was also observed a t a higher reaction temperature t o produce
-
CpW(CO)&-PPha)W(C0)4L.lb Abstract published in Advance ACS Abstracts, April 15, 1995. (1)(a) Shyu, S.-G.; Hsu, J.-Y.; Lin, P.-J.; Wu, W.-J.; Peng, S. M.; Lee, G. H.; Wen, Y.-S. Organometallics 1994,13, 1699. (b) Shyu, S. G.; Wu, W.-J.; Peng, S. M.; Lee, G. H.; Wen, Y.-S. J . Organomet. Chem. 1996,489,113. (c) Regragui, R.; Dixneuf, P. H.; Taylor, N. J.; Carty, A. J. Organometallics 1986,5,1. (d) Mercer, W. C.; Whittle, R. R.; Burkhardt, E. W.; Geoffroy, G. L. Organometallics 1985,4, 68. (e) Powell, J.;Sawyer, J. F.; Stainer, M. V. R. Inorg. Chem. 1989,28,4461. (0 Powell, J.; Coutoure, C.; Gregg, M. R. J . Chem. Soc., Chem. Commun. 1988,1208. @
i3,
A,
Investigation on the influence of one metal on the chemistry of its adjacent metal in bimetallic complexes would be of importance for the understanding of the cooperativity effect in binuclear complexes and clusters. It would be of interest to evaluate the cooperativity effect by using different kinds of metal fragments and study their influence on a similar metal moiety. Since the intramolecular CO transfer from Mo to W during
-
the addition reaction of CpW(CO)z@-PPhz)Mo(C0)5is assisted by the adjacent W moiety,la selecting a metal fragment which has a stronger interaction with the adjacent metal carbonyl may facilitate the addition reaction such that the addition product can be obtained under relatively mild conditions. We recently synthesized the heterobimetallic phosphido-bridged complex CpFe(CO)@-CO)@-PPh2)W(C0)4 (l),which has a strong iron-tungsten carbonyl interaction, as revealed by its structure.2 Reactions between 1 and Lewis bases L (L= CH3CN, PPh3, PMe3, PPhzH, P(OMe)3) produced addition products with L regiospecificallycoordinated to W under very mild conditions. Interestingly, reaction between CpFe(CO)a@-PPhz)W(C0)5(2) and PMe3 produced CpFe(CO)(PMe3)(p-PPhdW(2) Shyu, S. G.; Lin, P.-J.; Dong, T.-Y.; Wen, Y.-S. J . Organomet. Chem. 1993,460,229.
Q276-7333l95l2314-2253$Q9.QQ/Q 0 1995 American Chemical Society
2254 Organometallics, Vol. 14, No. 5, 1995
Shyu et al.
Scheme 1
2
Ph
k0 THF
\
J Ph ~
Cp(C0)Fe Sb-trans, Sc-trans, Sd-trans, Se-trans,
I, = PMe3 L = P(OMe)3 L = PPh,H L = PPh3
Ph
3-trans
3a-cis, L = CH3CN 3b-cis, I, = PMe3 ~ c - c ~ sL, = P(OMe), Jd-cis, L = PPh2I.I 3e-cis, L = PPh3
Ph
-, . ,
4YbL
+
3b-trans, L = PMe3 3c-trans, L = P(OMe), 3e-trans, L = PPh3
Ph
Ph
Cp(C0)Fe
-
co co 5-trans
(co)~, (4)with PMe3 regioselectively coordinated t o Fe. For other Lewis bases, no reaction was observed when 2 was allowed t o react with them under similar conditions. These observations indicated three interesting features: First, the Fe moiety in 1 could enhance substitution of the adjacent tungsten carbonyl through the formation of the metal-metal bond. Second, the cooperativity effect in binuclear complexes could be tailored by carefully selecting the adjacent metal such that a stronger interaction between the metal carbonyl ligand and the adjacent metal facilitated the reaction. Third, reaction site switching was observed through the formation of the metal-metal bond in the system. Reported herein are the reactivity studies of complexes 1 and 2. Scheme 1 shows reactions that comprise the main focus of our work. The products of the addition reaction have been characterized spectroscopically,and the structures of complexes CpFe(C0)2@-PPh2)W(C0)4(PMe3) (3b-cis), CpFe(CO)z@-PPh2)W(C0)4(P(OMe)s)
-
(3c-truns),4,and CpFe(CO)@-PPh2)W(C0)4(PPh3)(5etrans)were also determined by complete single-crystal X-ray diffraction studies. Experimental Section Unless otherwise stated, all reactions and manipulations of air-sensitive compounds were carried out a t ambient temperatures under a n atmosphere of purified N2 with standard procedures. A 450-W Hanovia medium-pressure quartz mer-
CO
Sc-cis, Sd-cis, Se-cis,
L = P(OMe)3 I, = PPh2H L = PPh3
5-cis
cury-vapor lamp (Ace Glass) and a Pyrex Schlenk tube as a reaction vessel were used in the photoreactions. Infrared (IR) spectra were recorded on a Perkin-Elmer 882 infrared spectrophotometer. 'H, I3C, and 31PNMR spectra were measured by using Bruker AMX-500, MSL-200, AC-200, and AC-300 spectrometers. 31PNMR shifts are referenced to 85%H3P04. Except as noted, NMR spectra were collected at room temperature. Electron impact (E11 and fast-atom bombardment (FAB) mass spectra were recorded on a VG 70-250s or a JEOL JMS-HX 110 mass spectrometer. Microanalyses were performed by the Microanalytic Laboratory at National Cheng Kung University, Tainan, Taiwan. 31P{1H}and lH NMR and IR spectroscopic data for complexes 3-5 are summarized in Table 1. Materials. THF was distilled from potassium and benzophenone under a n atmosphere of N2 immediately before use. Other solvents were purified according t o established proced u r e ~ .The ~ metal carbonyls M(C0)6 (M = Mo, W) and PMe3, PPhZH, and PPh3 were obtained from Strem, P(OMe)3 was purchased from Merck, and I3CO (99 atom % I3C)was obtained from Isotec. Other reagents and solvents were obtained from various commercial sources and used as received. Complexes
Cpie(CO)@-CO)@-PPh2)W(C0)4 and CpFe(CO)z@-PPh2)W(COh were prepared by literature procedure^.^ Synthesis of CpFe(CO)z@-PPhz)W(CO)*(NCCHs) (3a). To a solution of 0.10 g (0.15 mmol) of 1 in 30 mL of THF was added 10 mL of NCCH3 under N2 a t ambient temperature. (3) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; Pergamon: Oxford, U.K., 1966. (4)Shuy, S.-G.; Lin, P.-J.; Wen, Y . 3 . J. Organomet. Chem. 1993, 443, 115.
Organometallics, Vol. 14, No. 5, 1995 2255
Phosphido-Bridged Fe- W Complexes
Table 1. Spectroscopic Data for'1-5" 31P{1H}NMR,b,' 6
complex
lH NMR,brd6
3a-cis
14.0 (sy
3b-cis
-41.4 (d, 2Jp-p 24.5, JP-w 206, PMed, 4.69 (d, 'Jp-p 24.5, J p - w 219, p-PPhd 9.63 (d, 2Jp-p 49.2, pu-PPhd,-34.69 (d, 'Jp-p 48.8, PMe3) 4.63 (d, 3 J p - ~1.5, 5H), 4.00 (d, 'Jp-p 31.3, J p - w 205.3, p-PPhd, 139.4 (d, 2Jp-p 31.2, J p - w 375.4, P(OMe13 3.37 (d, 3Jp-H 11.2, 9H) 4.63 (d, 3 J p - ~1.3, 5H), 6.8 (d, 'Jp-p 93.5, J p - w 237.2, Pu-PPhz), 3.57 (d, 3 J p - ~11.3, 9H) 147.5 (d, 2Jp-p 89.3, JP-w 444.9, P(0Me)d 326, PPhzH), 5.6 (d, 2 J p - p 19.0, Jp-w 226.0, JP-H 4.66 (d, 3 J p - ~1.4, 5H), 5.2 9.1 (d, 'Jp-p 19.0; Jp-w 199.3,p-PPhz) 336, 3JP-H 8.3,lH) (dd, ~JP-H 4.49 (d, 3 J ~ -1.2) ~ 20.01 (d, 'Jp-p 28.1, J p - w 2271, -3.03 (d, 2Jp-p = 27.5 Hz) 4.60 (d, 3 J p - ~1.6, 5H) 8.2 (d, 'Jp-p 56.0, J p - w 2441, 27.1 (d, 'Jp-p 56.0 Hz, J p - w 284) 4.38 (d, 3 J p - ~1.6, 5H), 1.25 -4.42 (d, 2 J p - ~33.0, Jp-w 195, p-PPhd, 21.5 (d, 'Jp-p 33.0, PMed (d, 3 J p - ~9.2, 9H) 4.31 (d, 3 J p - ~1.3, 5H), 1.81 -34.2 (d, 'JP-P 30.5, JP-w 248, PMed, 165.7 (d, 2 J p - p 33.6, J p - w 221, p-PPhzY (d, 3 J p - ~8.1, 9H) 4.41 (s, 5H), 3.63 (d, 3 J p - ~ 140.18 (d, 'Jp-p 35.8, J p - w 225.01, 130.92 11.2 Hz, 9H) (d, 'Jp-p 35.8, Jp-w 410.0) 4.35 (d, 3 J p - ~1.1Hz, 5H), 3.71 163.95 (d, 'Jp-p 61.0, J p - w 205.0), 137.76 (d, 3 J p - ~11.6 Hz, 9H) (d, 'Jp-p 61.0, J p - w 432.5) 161.23 (d, 'Jp-p 40.2, J p - w 234.9, pu-PPhd,-1.93 4.44 (s) (d, 2 J p - p 35.2, J p - w 243.0, JP-H 350.3, P P ~ I ~ H ) ~ 4.40 (s) 135.02 (d, 'Jp-P 29.3, J p - w 218.0, p-PPhz), -22.56 365.2, PPhzHP (d, 2 J p - p 27.1, J p - w 235.0, JP-H 4.47 (s) 128.04 (d, 'Jp-p 24.3, P-PPhZ), 16.96 (d, 'Jp-p 24.3, PPh3)" 4.33 (s, 5H) 162.52 (d, 'Jp-p 34.8, pc-PPhz),21.25 (d, 'Jp-p 35.7, PPh3P
3b-transh 3c-cis 3c-trans Sd-cis 3e-cish 3e-trans 4
5b-trans 5c-cish3i 5c-transh 5d-cishJ 5d-transh 5e-cishJ Be-trans
IR, v(C0): cm-I 2020 m, 2000 m, 1974 m, 1888 s, 1834 mf 2020 m, 2001 s, 1969 m, 1898 sh, 1882 s, 1852 m 2025 m, 2009 s, 1972 m, 1893 s, 1870 s 2026 m, 2010 m, 1969 m, 1945 vw, 1886 s 2023 m, 2007 s, 1971 m, 1902 s, 1860 s 2019 s, 1997 w, 1968 m, 1936 m, 1876 vs 2057 m, 1939 m, 1915 s, 1896 s 2010 m, 1932 s, 1884 s
2015 m, 1932 s, 1891 s
a At room temperature. J values in Hz. In THF solution unless otherwise indicated. In CDC13 solution unless otherwise indicated. Cp and Me groups only. Abbreviations: s, singlet; d, doublet. e In THF solution unless otherwise indicated. Abbreviations: vs, very strong; s, strong; m, medium; w, weak; br, broad; sh, shoulder. f In NCCH3. g In CDClflCCH3 (1O:l). In solution, Sa-cis is only stable in the presence of NCCH3. Not separated pure. Cis:trans = 1:5. j Cis:trans = 1:2. 233 K in CD2C12. Cis:trans = 1:7. In CDC13.
After it was stirred for 10 min, the solution changed from dark brown to red. The 31PNMR of the solution indicated t h a t 3a was the only product. After the solvent was removed, a red solid of 3a was obtained. Anal. Calcd for C25H1806NPFeW: C, 42.95; H, 2.58; N, 2.00. Found: C, 42.49; H, 2.67; N, 1.56. l3C('H} NMR (CDCl&H&N): 6 214.4 (d, 2Jp-c = 15 Hz, 2CO), 210.3 (s,Jw-c = 115.0 Hz, lCO), 208.5 (d, 2Jp-c = 30.2 Hz, Jw-c = 129.8 Hz, lCO), 203.4 (d, 'JP-c = 5.9 Hz; Jw-c = 130.4 Hz, 2CO), 144.53 (d, J p - c = 9.9 Hz, ips0-C PPh'), 133.37 (d, 2 J p - ~= 9.6 Hz, 0-C, PPhZ), 127.4 (m, m-C,p-C, PPhz), 88.1 (s, C5H5), 2.79 (s, NCCH3). Synthesis of C~F~(CO)Z@-PP~Z)W(CO)~(PM~~) (3b). To a solution of 1(0.26 g, 0.40 mmol) in 30 mL of THF was added 122 yL (1.2 mmol) of PMe3 under N2 a t ambient temperature in the dark. After 1h, the solution changed from dark brown to red. Solvent was then removed and the residue was chromatographed on silica gel. Elution with CHzCldhexane (1:4) afforded two fractions. The first band, which was yellow, was trace in amount and was not identified. The second band was red. The tail of the second band contains mostly 3b-cis and a small amount of impurities a s indicated by the 31PNMR and was not collected. After the solvent was removed from the second band, pure 3b-cis was obtained a s a red solid. Yield: 0.16 g (54%). Anal. Calcd for C26H&&FeW: C, 42.54; H, 3.30. Found: C, 42.40; H, 3.12. MS (FAB): M CO+ mlz 707. Synthesis of CpFe(CO)z@-PPhz)W(C0)4(P(OMe)3)(3c). To a solution of 1 (0.32 g, 0.50 mmol) in 30 mL of THF was added 150 yL (1.2 mmol) of P(OMe)3 under Nz a t ambient temperature in the dark. After 2 h, the solution changed from dark brown to red. Solvent was then removed, and the residue was chromatographed on silica gel. Elution with CHZCld hexane (1:4) afforded two fractions. The first band, which was yellowish orange, was a mixture of 1 and 2. The second band was red. After the solvent was removed, pure 3c-cis was obtained a s a red solid. Yield: 0.25 g (65%). Anal. Calcd for
C26H2409PzFeW C, 39.93; H, 3.09. Found: C, 39.88; H, 3.02. l3C(lH} NMR (CDC13): 6 214.6 (d, 'Jp-c = 14.7 Hz, 2CO), 207.6 (dd, 2Jp-c = 3.7 Hz, 'Jp-c = 45.3 Hz, lCO), 206.3 (dd, 'Jp-c = 20.9 Hz, 'Jp-c = 9.4 Hz, lCO), 203.2 (dd, 'Jp-c = 6.1 Hz, 2Jp-c = 11.0 Hz, J p - w = 137.4 Hz, 2CO), 146.51 (d, Jp-c = 12.0 Hz, ipso-C, PPhz), 133.47 (d, 'JP-c = 9.86 Hz, 04, PPhd, 127.5 (s, p-C, PPhZ), 127.0 (d, 2Jp-c = 8.0 Hz, m-C, PPhZ), 88.2 (s, C5H5), 51.4 (d, 'Jp-c = 4.0 Hz, P(OMe)3). MS (FAB): M+ mlz 782. After the solvent was removed from the tail of the second band, 0.07 g of red solid which was identified as a mixture of 3c-cis and 3c-trans by 31PNMR and 13C NMR was obtained. In order to obtain pure 3c-trans, 3.5 g of 1 was allowed to react with 1equiv of P(OMe)3by following the above procedure. In the purification procedure by chromatography, the tail of the second band was collected. After the solvent was removed, pure 3c-trans was obtained as a red solid. Yield: 0.34 g (8%). Anal. Calcd for Czd32409PzFeW C, 39.93; H, 3.09. Found: C, 40.10; H, 3.08. l3C(lH} NMR (CDC13): 6 214.8 (d, 'Jp-c = 15.5 Hz, 2CO), 202.9 (dd, 2 J ~ - = c 8.3 Hz, 'Jp-c = 6.1 Hz, Jw-c = 129.3 Hz, 4CO), 147.6 (d, J p - c = 14.4 Hz, ~ ~ s o - PPhZ), C, 132.7 (d, 'Jp-c = 9.8 Hz, 0-C, PPhZ), 127.53 (8, p-C, PPhZ), 127.44 (d, 'Jp-c = 8.8 Hz, m-C, PPhz), 88.3 (s), 51.6 (s). MS (FAB): M - CO+ mlz 754.
Synthesis of CpFe(CO)&-PPhz)W(C0)4(PPh2H) (3d). To a solution of 1 (0.37 g, 0.58 mmol) in 30 mL of THF was added 122 pL (0.70 mmol) of PPhzH under Nz a t ambient temperature in the dark. After 1h, the solution changed from dark brown to red. Solvent was then removed, and the residue was chromatographed on silica gel. Elution with CH2Cld hexane (1:4) afforded two fractions. The first band, which was yellow, was a mixture of 1 and 2. The third band was red. The 31PNMR indicated t h a t it was a mixture of 3d-cis and 5d. The second band was red. After the solvent was removed, pure Sd-cis was obtained a s a solid. Yield 0.31 g (64%).Anal. Calcd for C35Hz&&FeW: C, 49.80; H, 3.10. Found: C, 49.40; H, 3.05. 13C(lH} NMR (CDC13): 6 214.7 (d, 'Jp-c = 14.7 Hz,
2256 Organometallics, Vol. 14, No. 5, 1995
Shyu et al.
Table 2. Crystal and Intensity Collection Data for 3b-cis, Sc-trans, 4, and 5c-trans 4 5e-trans 3b-cis 3c-trans mol formula mol wt space group
a (A)
b c
(A) (A)
a (de@
P (deg)
;g4)
p(ca1cd)(Mg m-3)
z
cryst dimens (mm) abs coeff p (Mo Ka)(mm-l) temp radiation I(Mo Ka)(A) 28 range (deg) scan type w scan speed (deg) no. of unique rflns no. of obsd rflns Rint'
no. of variables R R,
CzfiH24FeOfiPzW _. -. . . 734.12 P21k (NO.14) 9.8320 16.027(3) 18.264(4) 90 103.87(2) 90 2793(1) 1.745 4 0.51 x 0.44 x 0.38 4.87 room temp 0.710 73 45 W-28 1.04-8.24 3645 2982 (>2.0~((1)) 0.013 325 0.026 0.031 1.61 2.50(1)) 0.014 351 0.023b 0.026 1.29 X0.470
Cz6Hz4FeO6PzW 734.11 P 2 h (alt P21/c. No. 14) 15.?68(2) 10.7111(2) 17.784(2) 90 114.10(1) 90 2741.8(7) 1.778 4 0.45 x 0.44 x 0.38 4.98 room temp 0.710 73 45 0-28 1.50-8.24 3574 3005 (>2.Ou(Z)) 0.011 325 0.021 0.024 1.34 for Sb-cis atom
W Fe P1 P2 01 02 03
04 05 06
C1 C2 C3
C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C21 C22 C23 C24 C25 C26 C31 C32 C33 C34 C35 C36 a
Bise
Y
X
z
0.19540(3) 0.10079(2) 0.11788(1) 0.07628(10) 0.29442(7) 0.24274(6) 0.13995(17) 0.25800(10) 0.13238(9) 0.45866(19) 0.11327(12) 0.13865111) 0.2433(6) 0.0566(4) 0.2917(3) 0.0497(4) -0.1185(5) 0.0978(3) 0.2374(7) -0.0870(3) 0.0860(3) 0.1349(4) 0.1803(7) -0.0543(3) 0.1436(7) 0.4700(4) 0.2327(4) 0.3427(6) 0.2467(5) 0.3421(3) 0.2283(7) 0.0748(4) 0.2289(4) 0.0708(4) 0.1032(4) -0.0037(8) -0.0182(4) 0.2240(8) 0.0981(4) 0.1794(8) 0.0062(4) 0.1228(4) 0.1216(8) 0.3999(6) 0.2365(5) 0.2649(5) 0.2403(9) 0.3020(4) -0.1119(8) 0.2297(7) 0.1990(5) -0.0468(8) 0.2642(5) 0.1938(6) -0.0320(10) 0.2525(8) 0.3223(5) 0.3255(8) -0.0902(11) 0.2906(8) -0.1394(8) 0.2122(6) 0.3136(8) 0.5319(8) 0.0746(5) 0.1742(5) 0.5576(8) 0.2299(5) 0.1493(6) 0.5409(9) 0.1316(6) 0.0128(5) -0.0061(6) 0.0582(4) 0.3018(4) -0.0270(8) 0.0530(5) 0.3872(4) -0.1416(10) 0.4215(5) 0.0019(5) 0.3693(5) -0.0437(4) -0.2379(8) -0.0395(4) -0.2172(8) 0.2861(5) -0.1020(7) 0.2521(4) 0.0109(4) 0.1166(4) 0.2826(6) 0.3256(4) 0.17446) 0.3867(8) 0.3580(5) 0.4039(5) 0.1582(6) 0.4979(8) 0.5032(9) 0.4191(5) 0.0859(7) 0.3873(5) 0.0283(6) 0.4022(10) 0.0430(4) 0.2918(7) 0.3414(4)
Bison
3.20(1) 4.54(5) 3.30(7) 4.47(9) 7.4(3) 6.7(3) 7.1(3) 7.8(4) 8.4(4) 8.0(4) 4.3(3) 4.8(4) 4.7(4) 4.5(4) 6.1(4) 534) 6.2(5) 5.8(5) 7.4(6) 8.9(7) 7.4(6) 6.2(4) 7.5(5) 8.3(6) 3.6(3) 5.3(4) 6.3(5) 5.6(4) 5.1(4) 4.0(3) 3.8(3) 5.4(4) 7.0(5) 7.3(6) 6.5(5) 4.7(4)
= 8/~n2&LJ,jaiaJai*aJ*.
of yellow oil was obtained from the first fraction, and it was not identified. After the solvent was removed from the second band, a brown solid was obtained. It was identified by 31P NMR as a mixture of cis and trans isomers of 5d. Yield: 0.56 g (73%). Anal. Calcd for C34H260~P2FeW:C, 50.03;H, 3.21. Found: C, 50.40;H, 3.14. MS (FAEJ): Mf mlz 817.
-
Synthesis of CpFe(CO)@-PPhdW(CO)4(PPhs)(Be). A red solution of 3e (0.116g) in 10 mL of THF was irradiated with UV light for 30 min. The solution changed to yellowish brown. The 31PNMR of the solution indicated that there were two isomers (Be-cisand Be-trans)in the solution. Separation of the isomers by chromatography on grade I11 A1203 failed. After the solvent was removed, the mixture was obtained as a yellowish brown solid. Yield: 0.097g (86%). The trans isomer was crystallized as single crystals by slow diffusion of hexane into the saturated solution of the mixture in CHzC12. Anal. Calcd for C40H3005P2FeW: C, 53.84;H, 3.39. Found: C, 53.71;H, 3.37. l3C(lH} NMR (CDC13): 6 215.4(d, 2Jp-c = 15.4Hz), 199 (vb) 83.9(s, CsHs). MS (FAB): M+ mlz 893. Structure Determination of CpFe(CO)z@-PPhz)W-
-
Table 4. Atomic Coordinates and Isotropic Thermal Parameters (A2> for SC-trans
(CO)r(PMes) (3b-cis), CpFe(CO)(PMeS)@-PPhdW(CO)E (4), CpFe(CO)&-PPhz)W(C0)4(P(OMe)s) (3c-trans),and
CpFe(CO)@-PPhz)W(CO)4(PPhs)(Be-trans). Crystals of complexes 3b-cis, 4, and Sc-trans were grown by slow diffusion of hexanes into the saturated CHzCl2 solution of the relevant complex a t -15 "C in the air. Crystals of Be-trans were obtained by slow diffusion of hexanes into the saturated CH2C12 solution of the mixture Be-trans and Be-cis. Diffraction measurements were made using a n Enraf-Nonius CAD4 diffractometer and M o Ka radiation. All data reduction and refinements were carried out on a MicroVax 3600 computer using NRCVAX programs. Intensities were collected and corrected for decay, absorption (empirical, p s c a n ) , and Lp
W Fe P1 P2
0.13568(1) 0.52344(3) 0.10412(6) 0.89906(12) 0.07612(9) 0.72694(19) 0.18519(10) 0.32548(20) 01 0.2482(4) 0.6475(8) 02 0.1987(4) 0.5574(8) 03 0.0321(3) 0.3812(7) 04 0.4790(9) 0.0871(4) 05 0.0466(3) 1.0746(7) 06 0.2206(2) 0.9100(6) 012 0.2537(2) 0.3296(5) 0.1836(3) 0.2538(6) 013 0.1618(3) 014 0.2048(6) c1 0.2064(5) 0.6043(10) c2 0.1745(4) 0.5493(9) c3 0.0691(4) 0.4338(9) c4 0.1023(4) 0.4955(9) c5 0.0708(4) 1.0036(7) C6 0.1738(4) 0.9028(8) c7 0.0900(6) 1.0175(11) C8 0.1424(5) 0.9516(13) c9 0.1270(7) 0.8215(16) c10 0.0671(7) 0.8111(12) c11 0.0452(5) 0.9311(13) c12 0.2869(4) 0.2133(9) C13 0.2104(5) 0.3116(12) C14 0.1596(7) 0.2108(12) c21 0.0729(4) 0.7721(9) c22 0.1135(5) 0.8503(13) C23 0.1120(6) 0.8810(12) C24 0.0689(6) 0.8291(11) 0.7476(11) C25 0.0287(5) C26 0.0312(5) 0.7201(9) C31 -0.0043(3) 0.7088(8) C32 -0.0430(4) 0.8032(8) 0.7899(8) c33 -0.1023(4) c34 -0.1241(4) 0.6800(12) c35 -0.0858(4) 0.5861(10) C36 -0.0264(4) 0.6022(10) a Biso= 8/3x21i jUljaiajal*aJ*.
0.81599 0.72502(18) 0.83525(32) 0.79843(31) 0.7069(10) 1.0555(8) 0.9431(8) 0.5653(8) 0.8804(7) 0.8292(11) 0.8293(10) 0.6772(7) 0.8678(6) 0.7450(11) 0.9685(10) 0.8965(9) 0.6557(10) 0.8160(16) 0.7896(8) 0.5859(11) 0.5679(12) 0.5652(11) 0.5804(10) 0.5930(10) 0.8272(16) 0.5781(10) 0.9891(11) 0.9905(9) 1.0369(9) 1.1525(11) 1.2205(9) 1.1746(10) 1.0605(9) 0.8069(11) 0.8392(11) 0.8199(14) 0.7693(10) 0.7384(10) 0.7576(9)
2.37(2) 2.91(6) 2.48(9) 2.73(11) 7.0(5) 5.7(4) 5.1(4) 6.0(4) 4.6(3) 4.7(4) 3.9(3) 3.6(3) 3.9(3) 4.5(5) 3.2(4) 3.2(4) 3.4(4) 3.1(5) 2.8(4) 5.3(6) 5.4(6) 5.2(7) 5.1(7) 4.6(6) 4.7(6) 5.2(6) 5.3(7) 2.9(4) 3.8(6) 5.2(6) 4.8(6) 4.3(5) 3.9(5) 2.5(4) 3.5(5) 4.2(5) 4.4(5) 4.1(5) 3.4(4)
effects. Structures were solved by direct methods and refined on F by using full-matrix least-squares techniques. An E map from the starting set with the highest combined figure of merit revealed coordinates for W and Fe atoms. The remaining non-H atoms were located from successive difference Fourier maps and were refined anisotropically. The atomic parameters for all H atoms were excluded in the least-squares refinements, the hydrogen positions were displaced along the C-H vector to make the C-H distance of 1.08A. Crystal data and details of data collection and structure analysis are summarized in Table 2. The final positional parameters for all atoms are listed in Tables 3 (3b-cis),4(3ctrans),5 (41, and 6 (Bc-trans).Selected interatomic distances and bond angles are given in Tables 7 (3b-cis and 4) and 8 (3c-transand Be-trans). The thermal parameters for these complexes are provided in the supplementary material.
Results and Discussion Reactions of 2 with Phosphines and Molecular Structure of 4. The complex 2 remained intact after stirring with L (L = PPh3, PPhZH, P(OMe)3)in THF at ambient temperature in the dark overnight. However, it reacted with PMe3 to form 4 in THF at ambient temperatures within several hours. The upfield position of the phosphido bridge signal and the absence of the J p - w satellites of the PMe3 signal in the 31P NMR indicates the absence of a metal-metal bond and the coordination of PMe3 to the Fe atom in the ~ o m p l e x . ~
2258 Organometallics, Vol. 14, No. 5, 1995
Shyu et al.
Table 5. Atomic Coordinates and Isotropic Thermal Parameters (Az)for 4 atom W Fe P1 P2 01 02 03 04 05 06
c1
c2 c3 c4 c5 C6 C8 c9 c10
c11
c12 C13 C14 C15 c21 c22 C23 C24 C25 C26 C3 1 C32 c33 c34 c35 C36
X
0.59218(1) 0.66027(5) 0.70733(8) 0.76722(11) 0.7675(3) 0.5729(3) 0.4233(3) 0.5840(3) 0.4567(3) 0.5322(3) 0.7047(4) 0.5829(4) 0.4840(4) 0.5894(4) 0.5068(4) 0.5859(4) 0.5592(6) 0.6409(8) 0.7078(6) 0.6691(7) 0.5777(7) 0.8732(5) 0.8131(4) 0.7258(6) 0.7402(3) 0.8090(4) 0.8288(4) 0.7804(4) 0.7104(4) 0.6908(3) 0.8204(3) 0.9028(4) 0.9869(4) 0.9892(4) 0.9087(5) 0.8249(4)
Y
z
Bima
0.51543(2) 0.89366(6) 0.68543(11) 0.97647(13) 0.3479(4) 0.3841(4) 0.6921(4)
0.84810( 1) 0.92594(4) 0.94218(7) 1.03786(9) 0.8741(3) 1.0003(3) 0.8307(2) 0.6753(2) 0.7488(2) 1.0024(3) 0.8652(3) 0.9491(3) 0.8374(3) 0.7397(3) 0.7848(3) 0.9741(4) 0.8037(5) 0.8025(4) 0.8399(5) 0.8664(4) 0.8469(5) 1.0318(4) 1.1356(3) 1.0689(4) 1.0456(3) 1.0752(3) 1.1485(3) 1.1946(3) 1.1667(3) 1.0928(3) 0.9335(3) 0.9998(3) 0.9916(4) 0.9171(4) 0.8504(4) 0.8584(3)
2.93(1) 3.52(4) 2.65(6) 4.49(8) 7.1(3) 6.4(3) 5.1(2) 7.2(3) 5.7(2) 7.0(3) 4.4(3) 3.9(3) 3.6(3) 4.4(3) 4.0(3) 4.4(3) 8.0(5) 7.9(6) 7.2(5) 7.1(5)
0.6010(5)
0.3032(4) 0.8682(4) 0.4097(5) 0.4360(5) 0.6292(5) 0.5742(5) 0.3820(5) 0.8748(5) 0.9155(9) 0.8788(7) 0.9630(9) 1.0589(6) 1.0325(8) 1.0292(6) 0.8965(5) 1.1171(6) 0.6159(4) 0.5250(5) 0.4657(5) 0.4921(6) 0.5786(6) 0.6387(5) 0.6823(4) 0.7074(5) 0.7080(6) 0.6883(6) 0.6651(6) 0.6604(5)
8.0(5)
7.4(4) 5.1(3) 9.2(5) 2.7(2) 3.7(3) 4.8(3) 5.3(3) 5.0(3) 3.9(3) 3.0(2) 4.2(3) 5.0(3) 5.4(4) 5.8(4) 4.5(3)
The structure of 4 was further characterized by a singlecrystal X-ray diffraction study (Figure 1). The long distance between Fe and W (4.2741(10)A) in 4 indicates the absence of a metal-metal bond (Table 7). The replacement of the Fe carbonyl in 2 with PMe3 does not increase the repulsion between the Fe and the W moieties in 4, as shown by the observation that the distance between W and Fe and the Fe-P-W angle (118.75(5)")in 4 are almost the same as the distance between Fe and W (4.2110(9)A) and the Fe-P-W angle (118.42(6)")in 2.2 That only PMe3 can substitute the Fe carbonyl ligand is explained by the small cone angle and the high basicity of the phosphine ligand.6 For the other phosphines, greater steric factors or poor basicity may inhibit the substitution. Addition Reactions of 1 with Phosphines and CO. Reactions of 1 with Lewis bases L (L = PMe3, PPh2H, P(OMe13) at room temperature yielded CpFe(CO)&-PPhz)W(CO)*L (3) with L regiospecifically coordinating to w. When L was CHsCN, PMe3, or PPh2H, only the cis isomer (3-cis)was obtained. For PPh3 and P(OMe)3, both cis and trans (3-trans) isomers were produced (Scheme 1). (5)(a)Carty, A. J.; Maclaughlin, S. A.; Nucciarone, D. In Phosphorw31 NMR Spectroscopy in Stereochemical Analysis: Organic Compounds and Metal Complexes; Verkade, J . G., Quin, L. P.,Eds.; VCH: New
York, 1987; Chapter 16, and references cited therein. (b)Carty, A. J. Adu.Chem. Ser. 1982,No. 196,163. (c) Garrou, P. E. Chem. Rev. 1981, 81, 229. (6)Tolman,C. A. Chem. Rev. 1977,77, 313.
Table 6. Atomic Coordinates and Isotropic Thermal Parameters (Az> for 5e-tmns atom W
Fe P2
P1 01 02 03 04 05 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C21 C22 C23 C24 C25 C26 C31 C32 C33 C34 C35 C36 C41 C42 C43 C44 C45 C46 C51 C52 C53 C54 C55 C56 C60 CL1 CL2
X
Y
z
0.236431(17) 0.16202(6) 0.21491(11) 0.25782(11) 0.3329(4) 0.4024(3) 0.1251(4) 0.0789(3) 0.0282(3) 0.2988(5) 0.3418(5) 0.1660(5) 0.1340(5) 0.0824(5) 0.0967(6) 0.1698(6) 0.2328(5) 0.1991(6) 0.1139(7) 0.2336(4) 0.2689(5) 0.2497(7) 0.1981(7) 0.1633(6) 0.1813(5) 0.3542(4) 0.4137(5) 0.4854(5) 0.4997(6) 0.4419(6) 0.3683(5) 0.1226(4) 0.0519(4) -0.0173(4) -0.0177(5) 0.0513(5) 0.1207(5) 0.2078(4) 0.1365(5) 0.1342(6) 0.2017(7) 0.2736(6) 0.2759(5) 0.2927(4) 0.3222(5) 0.3795(6) 0.4056(6) 0.3763(6) 0.3203(5) 0.4669(12) 0.4835(6) 0.4989(17)
-0.183485(23) -0.33176(9) 0.00249(15) -0.37227(15) -0.1088(5) -0.2048(5) -0.2578(5) -0.1131(4) -0.3899(5) -0.1361(6) -0.1937(6) -0.2311(6) -0.1554(6) -0.3648(6) -0.3137(10) -0.2612(8) -0.3336(8) -0.4347(7) -0.4226(9) -0.4661(6) -0.4550(7) -0.5250(8) -0.6075(8) -0.6209(7) -0.5506(6) -0.4261(6) -0.3598(7) -0.4007(9) -0.5053(10) -0.5743(8) -0.5347(7) 0.0271(6) -0.0300(6) -0.0125(7) 0.0615(7) 0.1196(7) 0.1013(6) 0.0985(5) 0.1513(6) 0.2241(8) 0.2438(7) 0.1907(7) 0.1196(6) 0.0591(6) 0.1617(7) 0.2011(8) 0.1414(11) 0.0389(9) -0.0012(7) -0.4112(17) -0.5627(9) -0.471(3)
0.061107(18) 0.12257(6) 0.00705(12) 0.09110(12) 0.2489(4) 0.0548(5) -0.1251(4) 0.0745(4) -0.0375(4) 0.1802(5) 0.0550(5)
-0.0583(5) 0.0739(5) 0.0255(5) 0.1897(6) 0.2326(5) 0.2533(5) 0.2242(6) 0.1838(6) 0.0051(4) -0.0464(5) -0.1123(6) -0.1234(6) -0.0736(6) -0.0077(5) 0.1720(5) 0.2271(6) 0.2904(6) 0.2984(7) 0.2441(7) 0.1803(6) -0.0924(4) -0.1128(5) -0.1887(5) -0.2435(5) -0.2239(5) -0.1486(5) 0.0786(4) 0.0609(5) 0.1169(6) 0.1903(7) 0.2101(5) 0.1547(5) -0.0158(4) 0.0061(5) -0.0158(7) -0.0600( 7) -0.0834(6) -0.0605(5) 0.9603(15) 0.9228(7) 0.9359(18)
&ma
2.433(15) 3.19(5) 2.79(9) 2.93(10) 6.5(4) 6.8(5)
5.7(4) 4.9(4) 5.6(4) 4.0(5) 4.1(5) 3.3(4) 3.4(4) 3.7(4) 5.7(6) 5.0(6)
4.7(5) 5.3(6) 6.4(7) 3.2(4) 4.8(5) 6.1(7) 5.9(7) 5.5(6) 4.0(5) 3.7(4) 5.2(5) 6.6(6)
6.6(7) 6.7(7) 5.4(5) 2.9(4) 4.0(4) 4.5(5) 4.1(5) 4.4(5) 3.7(4) 2.9(4) 4.1(4) 5.8(6) 5.7(7) 5.4(6) 4.0(5) 3.2(4) 435) 6.7(7) 7.0(8) 6.3(7) 4.8(5) 18.8(8)
24.9(4) 16.0(8)
The regiospecific assignment is revealed by the observation of the Jp-w satellites for the signal of L in the 31PNMR of 3. An upfield shift of the phosphido bridge phosphorus signal in the 31PNMR indicates the cleavage of the metal-metal bond.5 For the assignment of the stereoisomers, a large J p - p value in the W complex usually indicates the phosphine ligands are trans to each other.7 However, this method of assignment can be used only when L is a phosphine and both isomers are obtained. When L is not a phosphine or only one isomer is produced, the 13CNMR spectrum can be used to support the cis and the trans assignment. For Sacis, the 13CN M R spectrum showed four terminal carbonyl signals (a-d) with an intensity ratio of 2:1:1:2 (Figure 2A). Signal a (214.4 ppm, JP-c (7) Ogilvie, F. B.; Jenkins, J. M.; Verkade, J. G. J . Am. Chem. SOC. 1970,92,1916.
Phosphido-Bridged Fe- W Complexes
Organometallics, Vol. 14, No. 5, 1995 2259
Table 7. Selected Bond Lengths (A) and Bond Angles (deg) in 3b-cis and 4 3b-cis Fe- * *W w-P1 w-P2
w-c1
w-c2 w-c3 w-c4 Fe-P1 Fe-C5 Fe-C6 c1-01 c2-02 C3-03 C4-04 C5-05 C6-06 Fe-P1-W Pl-W-P2
P1-w-c1 Pl-W-C2 Pl-W-C3 Pl-W-C4 Pl-Fe-C5 P1-Fe-C6
w-c1-01 w-c2-02 W-C3-03 W-C4-04 Fe-C5-05 Fe-C6-06
4
Bond Lengths 4.1812(11) Fe.**W 2.6047(17) W-P1 2.5322(20) W-C1 2.019(8) w-c2 1.970(8) w-c3 1.974(7) w-c4 2.038(8) w-c5 2.323809) Fe-P1 1.758(9) Fe-P2 1.778(9) Fe-C6 1.157(9) c1-01 1.159(9) c2-02 1.139(9) C3-03 1.125(9) C4-04 1.151(11) C5-05 1.131(11) C6-06 Bond Angles 115.96(7) Fe-P1-W P1-w-c1 98.03(6) 94.86(19) P1-w-c2 P1-w-c3 91.39(21) 174.75(21) Pl-W-C4 88.06(18) P1-w-c5 93.4(3) P1-Fe-C6 93.89(24) Pl-Fe-P2 w-c1-01 176.8(6) 176.0(6) w-c2-02 178.5(7) W-C3-03 175.2(7) W-C4-04 176.0(7) W-(35-05 177.4(7) Fe-C6-06
4.2741(10) 2.6327(12) 2.021(6) 2.045(6) 2.041(6) 2.011(6) 1.970(5) 2.3309(14) 2.2026(16) 1.724(6) 1.146(7) 1.132(7) 1.136(7) 1.151(7) 1.156(6) 1.151(8) 118.75(5) 87.50(15) 90.44(14) 88.83(13) 97.58(15) 175.96(16) 94.20(17) 100.71(5) 178.7(5) 173.8(4) 179.3(4) 175.3(5) 179.0(5) 175.2(5)
Table 8. Selected Bond Lengths (A)and Bond Angles (deg) in 3c-trans and Fie-trans 3c-trans Fe-W w-P1 w-P2
w-c1
w-c2 w-c3 w-c4 Fe-P1 Fe-C5 Fe-C6 c1-01 c2-02 C3-03 C4-04 C5-05 C6-06 Fe-P1-W P1- w -P2
P1-w-c1 P1-w-c2 Pl-W-C3 Pl-W-C4 Pl-Fe-C5 P1-Fe-C6
w-c1-01
w-c2-02 W-C3-03 W-C4-04 Fe- C5-05 Fe-C6-06
5e-trans
Bond Lengths 4.1757(15) Fe-W 2.5547(22) W-P1 2.3877(23) W-P2 w-c1 2.003(14) 2.006( 11) w-c2 2.021(10) w-c3 2.040(12) w-c4 2.319(3) Fe-P1 1.715(16) Fe-C5 1.758(10) c1-01 1.146(16) 1.158(14) c2-02 1.146(12) C3-03 1.125(15) C4-04 1.193(18) C5-05 1.164(13) Bond Angles 117.83(12) Fe-P1-W 176.09(8) P1-w-P2 95.9(3) P1-w-c1 92.4(3) Pl-W-C2 87.5(3) Pl-W-C3 90.3(3) Pl-W-C4 92.3(4) Pl-Fe-C5 91.6(3) w-c1-01 177.4(11) 175.9(9) w-c2-02 178.6(9) W-C3-03 176.0(9) W-C4-04 178.5(8) Fe-C5-05 176.8(8)
= 15.0 Hz)is assigned to the two
2.8548(11) 2.4343(20) 2.5023(19) 2.007(8) 2.027(8) 2.027(8) 2.063(8) 2.1809(21) 1.738(8) 1.154(10) 1.142(10) 1.139(10) 1.164(10) 1.158(10)
76.20(7) 169.94(6) 95.70(23) 83.64(23) 85.53(22) 101.84(21) 95.2(3) 178.3(7) 175.7(7) 178.6(6) 161.9(6) 177.1(7)
co ligands on Fe on
the basis of its position compared with that of the CO ligands on Fe in 2 (214.0 ppmh4 Signal c (208.5 ppm) is assigned to the CO ligands trans to the phosphido
bridge on the basis of its larger J p - c value (30.19 Hzh8 Signal d (203.4 ppm, J p - c = 5.9 Hz) is assigned to the two CO ligands trans t o each other and cis to the CHsCN. Finallv, simal b is assigned to the CO ligand trans t o the CH3Cbf For 3c-tra-ns, only two carbonyl signals were observed in its spectrum. The signal at 214.8 ppm is assigned t o the Fe CO’s on the basis of the favorable comparison with the reported resonances at 214.0 ppm for the Fe CO’s in the 13C NMR of 2.4 The signal at 202.9 ppm is assigned to the four fluxional cis W CO’s on the basis of the observed JP-w satellites (Jp-w = 129.3 Hz) (Figure 2B). The absence of the trans W CO signal indicates the phosphine ligand occupies the trans position. The structures of 3b-cis and 3ctrans were further characterized by single-crystalX-ray diffraction studies. Their structures are shown in Figures 3 and 4. The long distances between Fe and W in 3bcis (4.1812(11)A) and in 3c-trans (4.1756(15)A) indicate that there is no metal-metal bond in either complex. In 3c-tran8, the P(OMe)3 ligand is coordinated t o the W trans t o the phosphido bridge. In Sb-cis, the PMe3 ligand is cis to the phosphido bridge. One can consider the metallophosphine CpFe(C0)zPPhz to be a ligand similar to PR3. Thus, four COS, CpFe(CO)zPPhz, and the PR3 group (R = Me, OMe) coordinate to the W atom to form a distorted octahedron. The replacement of a CO in 2 with PMe3 does not increase the repulsion between the Fe and the W moieties in 3b-cis,as shown by the observations that the distance between W and Fe (4.1812(11)A) and the Fe-P-W angle (115.96(7)”) in 3b-cis are almost the same as the digtance between Fe and W (4.2110(9) A) and the Fe-P-W angle (118.42(6)”)in 2.2 The addition reaction was stereospecific, with L cis to the phosphido bridge. The observed 3-trans was formed from the kinetic product 3cis. This was demonstrated by the variablekemperature 31PNMR experiments on 3c-cis in THF. At 280 K, no 3c-trans was observed. At 300 K, a trace amount of 3c-trans was observed in the spectrum. As the temperature went up, the amount of 3c-trans increased. Also, after the complex was heated to reflux temperature in THF overnight, the signal intensity ratio of cis to trans isomers was increased t o 1:l. A similar phenomenon was also observed when 3b-cis was heated to reflux temperature in THF overnight. Interestingly, no 3dtrans was observed after heating 3d-cis in THF a t reflux temperature overnight. Heating the complex at higher temperature (refluxing in toluene) only resulted in the formation of the metal-metal-bonded complex 5d. The regiospecific addition on W may be due to a steric effect because of the bulky Cp, the p-PPhz ligand, and the incoming phosphine. Compared with the l3C(lH} NMR spectrum of 2 which had been stirred under I3CO overnight, the 13C{lH} NMR spectrum of 13CO-enriched 2 which was prepared by stirring 1 under 13C0showed addition of CO to 1 was predominantly on W and was stereospecifically cis to the phosphido bridge (Figure (8) (a) Braterman, P. S.; Milne, D. W.; Randall, E. W.; Rosenberg, E. J . Chem. SOC.,Dalton Trans. 1973, 1027. (b) Bonder, G . M. Inorg. Chem. 1976,14, 2694. ( c ) Todd, L. J.; Wilkinson, J. R. J . Organomet. Chem. 1974, 77, 1. (Q),TheNOE effect was avoided by using the inverse gate decouple
technique.
2260 Organometallics, Vol. 14, No. 5, 1995
Shyu et al.
Figure 1. ORTEP
A small amount of 13C0was coordinated to the Fe site, as shown by the spectrum which indicates that the addition reaction was not totally dominated by the electronic factor. The phosphine may initially coordinate to Fe to form the kinetic product and further migration of the phosDhine t o the adiacent W t o form 3, as in the case of
(C0)4FeOl-AsMez)Co(CO)zLz(L = PMe3, P(OMe)3).1° This possibility is eliminated because of the following observations. First, complex 3b was not observed in the reaction between 2 and PMe3 and only complex 4 was isolated a t room temperature. Second, after the THF solution of 4 was heated at reflux temperature overnight, only 5b and unreacted 4 were observed according to the 31PNMR spectrum of the product solution. One may suspect that 3b was formed as an intermediate which converted immediately to 5b under the reaction conditions so that 3b was not detected. However, heating 3b-cis in THF at reflux temperature only resulted in a mixture of 3b-cis and 3b-trans according t o the 31PNMR spectrum of the product solution. This excludes the possibility that 3b was an intermediate in the formation of 5b from 4 (Scheme 2). The formation of 3 from 1 requires the loss of one CO from W and the addition of one CO t o Fe. There are two possible sources for this added Fe CO ligand. One possibility is that a carbon monoxide on W may first be substituted by the phosphine ligand to form the metalmetal-bonded complex 5d. Free CO from the environment may react with 5d to form 3 (Scheme 3). The other possibility is the intramolecular migration of the semibridging CO on W to the adjacent Fe during the reaction. A reaction between 1 and PPhzH under 13C0 was carried out t o produce 3c. Both the mass spectrum and 13C NMR of the product indicated that no 13C0was (10)Langenbach, H.-J.; Vahrenkamp, H. Chem. Ber. 1979,112, 3390.
introduced into the product. These observations exclude the intermolecular CO addition to the W atom in the reaction. Substitution Enhancement and Switching of the Reaction Site-Role of the Metal-Metal Bond. One can consider the Fe-W bonding as a dative bond (donor-acceptor bond from Wo to FeT9which acts as a ligand to replace the Fe carbonyl ligand in 2 to form 1 after photolysis, since the semibridging carbonyl ligand in 1 is primarily bonded to the W atom.lCJ1The addition reaction usually occurs with the incoming ligand occupying the coordination side where the dative metalmetal bond was originally coordinated, as demonstrated by the addition of a Lewis base t o heterobimetallic phosphido-bridgedlcJ2and arsino-bridged ~omp1exes.l~ Nevertheless, the addition of L to 1 did not occur at Fe as expected but proceeded regiospecifically at the W atom. Therefore, we suggest that the metal-metal dative bond in the addition reaction of L to 1 behaves as more than just a built-in intramolecular leaving group. In addition, it also has two important impacts on the reactivity of the complex. First, the metal-metal bond enhances the substitution reaction of the carbonyl ligands on W. If we consider Cp(C0)zFePPhz in complexes 2 and 3 as a ligand, complex 3 can be considered as a disubstituted W(C0kLL' complex with L' = Cp(C0)2FePPhz and L = PPh3, PPhzH, PMe3, P(OMe)3. The substitution of the W carbonyl ligand usually requires high temperature.14 The metallophosphine ligand Cp(C0)zFePPhz did not activate the W(C0)s moiety for further substitution, (11)Roberts, D. A,; Steinmetz, G. R.; Breen, M. J.; Shulman, P. M.; Morrison, E. D.; Duttera, M. R.; DeBrosse, C. W.; Whittle, R. R.; Geoffroy, G. L. Organometallics 1983,2,846. (12)(a) Jenkins, H. A,; Loeb, S. J.; Stephan, D. W. Inorg. Chem. 1989,28, 1998. (b) Baker, R. T.; Calabrese, J . C.; Krusic, P. J.;Thenen, M. J.; Trogler, W. C. J. A m . Chem. SOC.1988,110, 8392. (13)Langenbach, H.-J.; Vahrenkamp, H. Chem. Ber. 1979, 112, 3773. (14)Keiter, R. L.; Keiter, E. A,; Mittelberg, K. N.; Martin, J. S.; Meyers, V. M.; Wang, J. G. Organometallics 1989,8,1399.
Organometallics, Vol. 14,No. 5, 1995 2261
Phosphido-Bridged Fe- W Complexes a
A
21 5
210
205
PPM
B
lk
I :!In 2lti 214 Cli! 210 DFll 2511 204 PO2
Figure 2. 13C{lH}NMR spectra of (A) Sa-cis in CH3CN/CDC13 and (B)3c-trans in CDCl3. Only carbonyl regions are shown in both spectra. from the electron-rich iron atom to the n* orbital of the since no 3 was observed when 2 was allowed to react adjacent tungsten CO to form a semibridging carbonyl with L in THF overnight. However, addition reactions ligand. l5 between 1 and phosphine ligands t o form 3 proceeded at ambient temperatures within several hours. Second, Formation of the metal-metal dative bond in 1 thus the reaction site for substitution is switched by the can be considered as a switch, which not only triggers metal-metal bond. In 2, an Fe CO ligand was substithe substitution of the W carbonyl by the activation of tuted by PMe3 to form 4 at room temperature. However, one of the W carbonyls through the adjacent Fe atom L substituted the W CO in complex 1 t o form 3 under but also switches the reaction site from the Fe metal to similar conditions. the adjacent tungsten. These two effects which origiThe metal-metal bond can influence the reactivity nated from the influence of one metal to the adjacent of the bimetallic complex in two ways. One way is metal through the metal-metal bond can be considered electron donation from the filled tzg orbital of the W as cooperativity effects of the adjacent metal in heteroatom to the iron atom through the metal-metal bond. bimetallic complexes. Powell suggested that the net result of this interaction Synthesis, Spectroscopic Characterization, and will be a decrease in d,,(WF+Jt*(CO) bonding t o the Molecular Structure of CpFe(CO)(lc-PPhdW(CO)& equatorial CO’s.lf This may result in the weakening of (5; L = P P b , PPhZH, PMes, P(0Me)s). One of the the W-CO bond in 1. The second way is that the carbonyl ligands in 3 can be removed by W irradiation metal-metal bond can bring the two metals together such that the adjacent iron is able to activate one of the (15) Cotton, F.A. Prog. Inorg. Chem. 1976,21, 1. W carbonyl ligands through the donation of the electron
-
Shyu et al.
2262 Organometallics, Vol. 14,No. 5, 1995
Figure 3. ORTEP drawing of 3b-cis. Hydrogen atoms are omitted.
Figure 4. ORTEP drawing of Sc-trans. Hydrogen atoms are omitted.
to re-form the metal-metal bond to produce 5. Actually, during the preparation of 3 , a small amount of 5 was always observed in 3 if laboratory fluorescent light was not avoided during chromatography. The downfield resonance in the 31PNMR of the phosphido phosphorus indicates the presence of a metal-metal bond in 5. The
phosphine ligand remains coordinated to the W because satellites were observed. Both cis and trans isomers of 5 were observed, and only 5 b - t r a n s and 5 e - t r a n s were separated pure through recrystallization. The assignments of the cis and trans isomers were based on the magnitude of the
Jp-w
Organometallics, Vol. 14, No. 5, 1995 2263
Phosphido-Bridged Fe- W Complexes
W-CO cis
Fe-CO
zis
~
.
zis
'
zi4
'
ziz
'
zio'k
'
zk
264
'
,--
202
'
zoo
IS
1%
'
144
'
142
PPM
Figure 6. 13C11H)NMR spectrum of 13CO-enriched2. Only the carbonyl region is shown. Scheme 2 Ph P ''
Ph
/ \
I
I I
\,
co
-
A
THF
T
3b-d~
3b-trans
Sb-trans
value, since the trans isomer usually has a large value in W c~mplexes.~ The structure of Be-trans was further characterized by a single-crystal X-ray diffraction study (Figure 6). The distance between W and Fe (2.8507(20) A) indicates a metal-metal bond. The W(4)-C(4)-0(4)
Jp-p
Jp-p
angle (161.0(13)") indicates a semibridging carbonyl with CO(4) primarily coordinated to the W atom. The trans PPh3 does not increase the repulsion between the W and the Fe moieties in the complex, as shown by the W-P-Fe angle (76.12(12)") and the W-Fe distance (2.8548(10)A) in Be-trans. They are almost the same
2264 Organometallics, Vol. 14, No. 5, 1995
Shyu et al.
Scheme 3
3
1
Phq
CO
3
5
as the W-P-Fe angle (75.06(22)") and the distance between W and Fe (2.851(3) A) in L2 The four W CO ligands cis to the phosphido bridge in Be-trans are fluxional. Only one doublet of the Fe carbonyl signal a t 215.4 ppm ( 2 J p - ~= 15.4 Hz)and a very broad hump for the W carbonyl signal at 199.0 ppm were observed in the I3CONMR spectrum. The assignment was based on their favorable comparison with the Fe CO signal a t 212.6 ppm C2Jp-c = 12.6 Hz)and the W carbonyl signal a t 192.0 ppm (broad hump) of l.4No trans W CO signal was observed. This kind of fluxional behavior has been observed for several monophosphidobridged complexes with a metal-metal bond, and the trans CO ligand was usually not involved in the fluxional behavior. Thus, the absence of the trans CO signal is consistent with the molecular structure where the phosphine ligand occupies the trans position. The structure of 5b-trans, the only product obtained from the reaction between 1 and PMe3, was determined by the only observation of the Fe CO resonance in its 13C NMR spectrum.
Conclusions Reactions of Cp$e(CO)(u-PPhz)(u-CO)W(CO)d (1)and Lewis bases L (L = CH3CN, PMe3, PPhzH, P(OMe13, PPh3) at ambient temperatures resulted in the addition
W
W
Figure 6. ORTEP drawing of Se-tram. Hydrogen atoms are omitted. products CpFe(CO)z@-PPhz)W(C0)4L(3) with L regiospecifically on W. W irradiation of 3 resulted in the formation of 5. Structures of 3b-cis, 3c-trans,and 5etrans were determined by single-crystal X-ray studies. No reaction was observed when CpFe(COl&-PPhz)W(COk (2) was stirred with L under similar conditions. However, reaction of 2 with PMe3 produced 4 with PMe3 coordinating t o Fe. The adjacent metal was believed to assist the addition reaction and switched the reaction site from Fe to W through the metal-metal bond.
Acknowledgment. We thank the National Science Council, Republic of China, and Academia Sinica for financial support of this work. Supplementary Material Available: Listings of crystal data and refinement details, atomic coordinates, anisotropic thermal parameters, and bond distances and angles and figures giving additional views of 3b-cis,3c-truns,4, and Setrans (43 pages). Ordering information is given on any current masthead page.
OM940775E
