Organometallics 1995, 14, 2775-2780
2775
1,2-H Shift on Tetranuclear Ethynyl Complexes ~ ~ ~ - C ~ H ) ( Q ~ - C ~ R ~ )(M F~ =M Fe, CO Ru; ~ (n C=O10, ) ~11; R = H, Me)l Munetaka Akita,* Hideki Hirakawa, Kohsuke Sakaki, and Yoshihiko Moro-oka* Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226, Japan Received January 26, 1995@ The interaction of the trinuclear ethynyl complexes Coz(C0)6111-(q5-C5R5)Fe(C0)2C=CH1 (3: a, R = H; b, R = Me] with Fe2(CO)g and the addition reaction of (q5-C5R5)Fe(CO)2C=CH (la,b)to the trimetallic species R u C O ~ ( C Oafford ) ~ ~ the tetranuclear vinylidene intermediates
Co2M(C0)91113-C=C(H)Fe(q5-C5R5)(CO)~l (4, M = Fe; 6, M = Ru), respectively, which are thermally decarbonylated to produce the tetranuclear acetylide clusters @4-CzH)[(q5-C5R5)Fe]MCo2(CO)lo (5, M = Fe; 7, M = Ru) with the spiked triangular metal array. The skeletal rearrangement [ H C W F e ( 1 , 3 ) C=C(H)Fe (4,6) H C W F e (5, 711 can be explained in terms of a 1,2-H shift on the CZbridge of the plausible alkyne-cluster type intermediates ~3-(q5-C5R5)Fe(C0)~C~CHIMCo2(CO)g [M = Fe (9), Ru (lo)].
-
-
Introduction The 1,2-hydrogen shift of terminal alkynes within a coordination sphere of a transition metal (Scheme 1)has been recognized as an elementary step of organometallic chemistry.2 Although the uncatalyzed process a has proved to be highly unfavorable owing to the thermodynamic instability of the vinylidene species, coordination t o one or more transition metal centers results in inversion of the energetics to make the process feasible (processes b and c ) . ~In particular, the process b on mononuclear complexes serves as a versatile preparative method for vinylidene complexes2 and is involved as a key step of an increasing number of catalytic
I R'= Fe(q5-C5Rs)(CO), Y very facile 1,2-H shift
transformation^.^ We have been studying the synthesis, structure, and chemical properties of polymetallic C2H complexes derived from the ethynyliron complexes (q5-C5Rs)Fe(CO)zC=CH [R = H (la),Me (1b)15As a result, it has been revealed that the introduction of the iron groups as the 1-alkyne substituents [R = (q5-C5R5)Fe(C0)2in Scheme 11 induces remarkable labilization of the H atom on the C2 moiety. For example, the cationic diiron complex [ F P * ~ @ - C = C H ) ] B(process F ~ ~ ~ b where R = M = Fp*) and the trinuclear complexes Cp2M02(C0)4b-q2: q2-(q5-C5R5)Fe(C0)2C=CHI5g[process c where R = (q5CsR5)Fe(C0)2 and M = MoCp(C0)al exhibit dynamic behavior by way of the fast reversible 1,2-H shift on the C2 bridge as confirmed by W-NMR analyses. As an extension, we have examined the chemical properties Abstract published in Advance ACS Abstracts, May 1, 1995. (1)Abbreviations: Cp = q5-C5H5;Cp* = q5-C5Me5;Fp = CpFe(C0)z; Fp* = Cp*Fe(CO)z. Throughout this paper the carbon atoms of the C2H linkage are designated as Fe-C,-Cb or Fe-Cl-C2 irrespective of the structure. (2) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Bruce, M. I.; Swincer, A. G. Adv. Organomet. Chem. 1983,22, 60. (3) (a)Silvestre, J.; Hoffmann, R. Helv. Chem. Acta 1986,68, 1461. (b) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J . A m . Chem. SOC.1994, 116, 8105. (4) (a) Wakatsuki, Y.; Yamazaki, H.; Kumegawa, N.; Satoh, T.; Satoh, J. Y. J. A m . Chem. SOC.1991, 113, 9604. (b) Trost, B. M.; Kulawiec, R. J. J.A m . Chem. SOC.1992,114,5579. ( c ) References cited in ref 2a. @
of mixed metal tetranuclear C2H complexes [process d where R = (q5-C5R5)Fe(C0)21.The corresponding tautomerization of 1-alkyne on trinuclear cluster systems (process d where R = organic group) was already reported, and trinuclear vinylidene clusters have been prepared via this process.6 In a previous paper,5e we reported formation of a tetranuclear C2H complex (CpFe)(CpNi)zNi(CO)2@4(5) (a) Akita, M.; Terada, M.; Oyama, S.; Moro-oka, Y. Organometallics 1990, 9, 816. (b) Akita, M.; Terada, M.; Oyama, S.; Sugimoto, S.; Moro-oka, Y. Organometallics 1991, 10, 1561. (c) Akita, M.; Terada, M.; Moro-oka, Y. Organometallics 1991,10,2962. (d) Akita, M.; Terada, M.; Moro-oka, Y. Organometallics 1992,11,1825. (e)Akita, M.; Terada, M.; Moro-oka, Y. Organometallics 1992, 11, 3468. (0 Akita, M.; Sugimoto, S.; Tanaka, M.; Moro-oka, Y. J.Am. Chem. SOC.1992,114, 7581. ( g ) Akita, M.; Sugimoto, S.; Takabuchi, A,; Tanaka, M.; Morooka, Y. Organometallics 1993, 12, 2925. (h) Akita, M.; Ishii, N.; Takabuchi, A.; Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 258. (i) Akita, M.; Takabuchi, A,; Terada, M.; Ishii, N.; Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 2516-2520. (i) Akita, M.; Terada, M.; Ishii, N.; Hirakawa, H.; Moro-oka, Y. J.Organomet. Chem. 1994,473, 175. (k) Akita, M.; Moro-oka, Y. Bull. Chem. SOC.Jpn. 1996, 68, 420.
0276-733319512314-2775$09.0010 0 1995 American Chemical Society
Akita et al.
2776 Organometallics, Vol. 14,No. 6, 1995 Scheme 2
ep
2
C2H) (2) by addition reaction of Ni(C0)4 to (CpNi)&v~:T,I~-F~C=CH) (Scheme 2). This result prompted us to examine structure expansion of its Co analogues Cor (C0)6~-172:172-(175-C5R5)Fe(cO)2C~CH] (3) [3a (R = HI, 3b (R = Of many attempts to expand the structure, we found that tetranuclear FezCo2 complexes were obtained by interaction with Fez(C0)g. In addition, the isoelectronic FeRuCo2 complexes were also prepared by the reaction of 1 with the reactive heterotrinuclear species R~Coz(C0)11.~,* Herein we disclose the details of the reaction and structural aspects of the resulting tetranuclear k4-C2H)FeMCo2 (M = Fe, Ru) complexes relevant to the 1,2-H shift. The corresponding organic counterparts derived from l-alkyne, i.e., trinuclear 013R'C2H)MCoz clusters (M = Fe,9 Rus), were studied by Vahrenkamp et al. 3
Results and Discussion
7
6
4"
32
035
Interaction of Figure 1. Molecular structure of the two independent C=CHl (3a,b) with Fe2(C0)9. When the trinuclear molecules of Sa: (a) molecule 1; (b) molecule 2. The ethynyl complex C O ~ ( C ~ ) ~ C U - ? ~ ~ : (3a)5c ~ ~ ~ -[the F ~ C = Cnumbers H ) without the atom names are for the CO ligands. was treated with Fez(C0)g at adduct of l a to Co~(C0)sl room temperature, two products 4a and Sa were isolated (Sb)]suggest that the C2H ligands are incorporated in as black crystals in 13% and 28% yields, respectively, a cluster environment. The major products 5a,b are after preparative TLC separation (eq 1). The thermally readily assigned to acetylide cluster compounds on the values of the Cp signals of the basis of the large ~Jc-H C2H bridge [5a, 6c 193.0 (s, Cd, 118.5 (d, VC-H= 203 Hz, Cp); 5b, dc 193.1 (s,Ca), 115.7 (d, 'Jc-H = 208 Hz, Cp)]. The rather sharp singlets around 193 ppm, the chemical shift and shape of which do not change significantly in the temperature range of room temperature to -80 O C , l 0 have been assigned to Ca. Then the 3e (R= H) molecular structure of 5a was determined by X-ray 3b (R= Me) 13 Yo (sa: R= H) crystallography. ORTEP views of the two independent not detected (4b: R= Me) molecules with essentially the same geometry are reproduced in Figure la,b, and the crystallographic data and the selected structural parameters are listed in Tables 1and 2. The four metal atoms are arranged in a spiked triangular array, with which the C2H ligand interacts as a p-y1(Fe1,3):y1(Fe2,4)-as well as p q 2 (C01,3):~~(Co2,4)-bridging ligand. As can be seen from
unstable, minor p r o u c t 4a contains only terminal CO ligands as indicated by IR, whereas the major product 5a contains the v@-CO) absorption at 1838 cm-l. In the case of the reaction of the Fp" derivative 3b, the adduct 5b with the v@-CO) absorption was obtained exclusively without formation of any detectable amount of 4b. The deshielded C f l signals PH-NMR) of the tetra~ (4a),8.65 (Sa),8.68 nuclear complexes 4 and 5 [ d 7.18
(6) (a) Sappa, E.; Tiripicchio, A.; Braunstein, P. Chem. Rev. 1983, 83, 203. (b) Silvestre, J.; Hoffmann, R. Langmuir 1985,1, 621. (c) Raithby, P. R.; Rosales, M. J. Adu. Inorg. Chem. Radiochem. 1985, 29, 169. (d) Nast, R. Coord. Chem. Rev. 1982,47,89. (e) Carty, A. J. Pure Appl. Chem. 1982,54,113. (7)(a) Roland, E.; Vahrenkamp, H. Chem. Ber. 1985,118,1133. (b) Varenkamp, H. Inorg. Synth. 1989,26,354. (8) (a) Roland, E.; Vahrenkamp, H. J.Mol. Catal. 1983,21,233. (b) Bernhardt, W.; Vahrenkamp, H. Angew. Chem., Int. Ed. Engl. 1984, 23, 141. (c) Roland, E.; Bernhardt, W.; Vahrenkamp, H. Chem. Ber. 1985,118,2858. (9)Albiez, T.; Bernhardt, W.; von Schnering, C.; Roland, E.; Bantel, H.; Vahrenkamp, H. Chem. Ber. 1990,123,141. (10)The shape of the CO signals appearing in the region of 190250 ppm depends on the temperature measured owing to the fluxionality of the CO ligands.
Tetranuclear Ethynyl Complexes
Organometallics, Vol. 14, No. 6, 1995 2777 Table 1. CrystallographicData for 5a, 6a, and 7b Sa
6a
7b
C17H601oFezCoz 599.79 P2 lln 9.213(3) 19.731(6) 22.486(6)
Cl~H6OllFeRuCoz 673.02 Pca21 12.892(2) 13.024(4) 13.164(9)
C2zH16010FeRuCo2 7L5.15
compds formula fw
:Y blA CIA ddeg Pldeg
90.96(2)
$2:
4 087(2 )
z
8 1.949 30.38 5-50 7904 4326 559 0.063 0.044
dea~edlffCm-~ plcm-1 28ldeg no. of data collcd no. of unique data with I > 3 d I ) no. of variables
Ra RWb
Table 2. Selected Structural Parameters for Saa C1-C2 c1-Col c1-co2 C1-Fel C1-Fe2 c2-Col c2-co2 Col-co2 Col-Fe2 Co2-Fe2 Fel-Fe2
Bond Lengths 1.34(1) c21-c22 2.30(1) c21-c03 2.12(1) C21-c04 1.96(1) C21-Fe3 1.93(1) C2 1-Fe4 1.94(1) C22-C03 2.07(1) C22-c04 2.471(2) c03-CO4 2.617(2) Co3-Fe4 2.573(2) Co4-Fe4 2.557(2) Fe3-Fe4
1.34(1) 2.30(1) 2.14(1) 1.96(1) 1.90(1) 1.99(1) 2.05(1) 2.467(2) 2.608(2) 2.584(2) 2.589(2)
Bond Angles 67.8(3) C O ~ - C ~ ~ - C O 67.4(3) ~ 57.3(6) C03-C21-C22 59.5(6) 78.7(3) Co4-C21-Fe4 79.3(4) 69.1(6) C04-C21-C22 67.6(6) 82.2(5) Fe3-C21-Fe4 84.1(5) 147.2(9) Fe3-C21-C22 144.0(9) 131.8(8) 130.1(9) Fe4-C21-C22 76.1(3) C03-c22-C04 75.4(4) 84.9(7) 87.1(8) C03-C22-C21 73.5(6) C04-C22-C21 75.1(6) 60.67(6) Co4-Co3-Fe4 61.15(6) 62.11(6) 62.47(6) Co3-Co4-Fe4 104.01(7) Co3-Fe4-Fe3 104.27(8) 93.35(7) 93.70(7) Co4-Fe4-Fe3 56.87(6) Co3-Fe4-Co4 56.75(6)
Col -c 1- c 0 2 Col-Cl-C2 Co2-Cl-Fe2 C02-Cl-C2 Fel-C1-Fe2 Fel-Cl-C2 Fe2-C1 -C2 Col-C2-C02 Col-C2-C1 co2-c2-c1 Co2-Col -Fe2 Col-Co2-Fe2 Col -Fe2-Fel Co2- Fe2 -Fe 1 Col- Fe2 -Co2
Bond lengths in angstroms and bond angles in degrees.
5a
7b
Figure 2. Top views of the core s t r u c t u r e s of 5a and 7b. the top view of the core structure (Figure 2a), the C1C2 (C21-C22) part lies almost perpendicular to the ColC02 (co3-co4) vector. Although the chiral environment caused by the Fe1,3 part slightly distorts the structure from a symmetrical one, the C1 ((321) and C2 (C22) atoms are located nearly equidistant from the n-coordinated co1,3 and co2,4 atoms. Although the tetra-
2210(2) 4 2.022 28.45 5-60 3590 2347 297 0.036 0.026
P1 9.390(4) 15.882(4) 9.243(6) 97.43(4) 108.93(4) 99.07(3) 1263(1) 2 1.880 24.78 5-60 4824 3241 325 0.032 0.028
nuclear structure of 5 appears to be formed by a capping reaction of the FeCo2 triangular face in 3 by an “Fe(CO)2”fragment, the formation of 5 follows a couple of processes as described below. The other product 4a, which could not be fully characterized owing t o its thermal instability, was assigned to the vinylidene cluster CozFe(CO)d&-C=C(H)Fpl by comparison of the spectroscopic features with those of the structurally characterized Ru analogue 6a (see below), in particular (1)the olefinic nature of the CH moiety of the C2H part as suggested by the NMR ~ 6c 123.7 (d, ~Jc-H= 151 Hz, =C(H)Fp)l data [ d 7.18; and (2) the absence of v@-CO) absorption. Unfortunately, the characteristic, highly deshielded C=C(H)Fp signal could not be located despite several attempts. In accord with the composition, the molecular weight (mlz = 628) determined by FDMS is larger than that of 5a (mlz = 600) by 28 (CO), and upon being heated in refluxing benzene, the vinylidene cluster 4a was converted to the acetylide cluster 5a in a quantitative yield (lH-NMR) through a combination of thermal decarbonylation and H-migration. On the other hand, the Cp* complex 4b could not be detected at all even by a lHNMR experiment, and the more stable acetylide cluster 5b was formed directly as mentioned above. Thus the reaction of 3 with Fez(C0)g gives the vinylidene cluster 4 via addition of an “Fe(C0)2”fragment followed by 1,2-H shift. Upon thermal decarbonylation of 4, backward H-shift coupled with the FeCo bond formation produces the acetylide cluster 5. These results indicate that the C2H atom migrates between the two carbon atoms. Interaction of (q5-C5R5)Fe(C0)2C=CH(1) with RuCoz(CO)11. In order to examine the generality of the 1,2-H shift on tetranuclear C2H complexes, preparation of Ru analogues of 4 and 5 was attempted. When the core composition of the tetranuclear clusters 4 and 5 is compared with that of the starting mononuclear ethynyl complex 1, formal addition of “FeCo2(COX” fragments (x = 8, 9) to 1 leads to the composition of 4 and 5. Then we examined the addition reaction of 1 t o the reactive trinuclear cluster RuCo2(COh reported by Vahrenkamp et al.73s
Akita et al.
2778 Organometallics, Vol. 14, No. 6, 1995
Table 3. Selected Structural Parameters for RUCO~(CO)~C~&=C(H)RI CR = Fp (6a) and t-Bul" R Fp (6a) C1-C2 C1-Fe C1-Ru c2-Col c2-co2 C2-RU Ru-Col Ru-CO~ Col-co2 Ru-C1-Fe Ru- C1 -C2 Fe-Cl-C2 Ru-C2- Col R u - C ~-C02 R u - C ~-C 1 Col-C2-C02 COl-C2-C1 co2-c2-c1 Col-Ru-Co2 Col-Ru-C2 Co2-Ru-C2 Ru-Col -C02 Ru- Col -C2 C02-Col-C2 Ru-Co2-Col Ru-Co2-C2 Col-C02-C2
Figure 3. Molecular structure of 6a drawn at the 30% probability level. The numbers without the atom names are for the CO ligands. Treatment of l a with RuCoz(CO)11in benzene at room temperature readily gave the dark red adduct 6a (eq 2). The 13C-NMR parameters for the C2H part, in
(co)2 H h5-c5~5)~e~d
- 1-/&% -
RuCO~(CO)II (q5-C5R5)Fe-C=C-H ( W 2
l a (R= H)
Ru
C6H6
(co)~ \co/
A
(cob
(cob
1b (R= Me)
Bond Lengths 1.350(9) 2.014(7) 2.445(7) 1.925(7) 1.895(7) 2.106(7) 2.629(1) 2.629(1) 2.489(2) Bond Angles 126.3(3) 59.3(4) 133.8(5) 81.3(2) 82.0(3) 87.2(4) 81.3(3) 132.8(5) 142.1(5) 56.53(3) 46.4(2) 45.5(2) 61.74(4) 52.3(2) 48.8(2) 61.73(4) 52.5(2) 49.9(2)
t-BUb 1.37(1) 1.53(1)c 2.405(8) 1.901(7) 1.983(7) 2.099(8) 2.618( 1) 2.628(1) 2.489(1)
d d 131(1)' d d d d d d 56.7(1) d d 61.9(1) d d 61.5(1) d d
Bond lengths in angstroms and bond angles in degrees. Reference 9. The -C-C(quaternary carbon of the t-Bu group) length. Not reported. e The C=C-C(quaternary carbon of the t-Bu group) angle. b
51 % (6a: RE H) detected by 'H-NMR (6b: R= Me)
67 % (7a: R=H) 42 Yo (7b: R= Me)
particular, the quaternary carbon signal observed in low field [Qc 277.5 (s, C2), 107.1 (d, 'Jc-H= 151 Hz, Cl)l, clearly indicate that 6a contains a vinylidene-type C=C(H) moiety, and the vinylidene structure has been confirmed by X-ray crystallography. The molecular structure is shown in Figure 3, and the selected structural parameters are summarized in Table 3. The C=C(H)Fp moiety interacts with the RuCo2 cluster part as a vinylidene ligand. The C2 atom bridges the two Co atoms, and the Cl-C2 part is n-bonded to the Ru center. The Cl-C2 length [1.34(1)A] falls in the typical range of the C=C lengths of trinuclear vinylidene cluster compounds.2 The Fp part has no interaction with the RuCo2 cluster part and acts merely as a vinylidene substituent. In accord with this description, the geometry of the cluster part is close t o that of the organic counterparts, RUCO~(CO)&~-C=C(H)R] (R = t-Bu, Ph),9as compared with the typical t-Bu derivative (Table 2). On the basis of the similar spectroscopic features of 4a and 6a 1(1) C2H chemical shifts; (2) absence of v@-CO)absorption; (3) thermal transformation to the acetylide clusters Sa and 7a1, 4a has been assigned t o the Fe analogue of 6a as discussed above.
The reaction of the Cp* derivative l b with RuCoz(C0)ll followed a similar process to give the orange adduct 6b. Although an analytically pure sample was not obtained owing to facile thermal decarbonylation (see below), 6b was assigned to the vinylidene structure on the basis of the C f l resonance (lH-NMR). Thermolysis of the vinylidene clusters 6a,b in refluxing benzene resulted in the formation of the deep green complexes 7a,b, respectively, which showed spectroscopic features quite similar to those of 5a,b. For example, 7 contains a v@-CO)absorption and the C2H moiety may behave as an acetylide ligand as suggested by the large VC-Hvalues [7a, QH 8.07 (SI, 6c 198.6 (9, C,J, 106.2 (d, 'Jc-H = 196 Hz, Cp); 7b, QH 7.98 (s), dc 198.9 (s, Ca), 106.7 (d, VC-H= 193 Hz, Cp)]. However, the structure of the Ru-containing tetranuclear cluster 7b has proved to be considerably different from that of the above-mentioned Fe derivative 5a as revealed by X-ray crystallography (Figure 4 and Table 4). While the four metal atoms are arranged in a spiked triangular array in a manner similar to those in 4a, the spiked (v5-CsRs)Fepart is not bonded to the group 8 metal (Ru) as in the case of Sa but to Col. Namely, the Ru atom does not occupy the hinge position of the basal RuCo2 triangle. Furthermore 7b contains one more bridging CO(17) in addition of CO(l1) and the Cl-C2 part is coordinated to the Ru and Col atoms in an unsymmetrical manner. The C2H ligand is formally a-bonded to Fe, Ru, and Col and n-bonded to C02, whereas that in 5a is n-bonded to Col and C02. As a result, the C1C2 bond lies almost parallel to the Col-Ru vector. Therefore the core part in 7b, which is essentially the same as that of the Ph analogue of 7b, (CpFeI-
Tetranuclear Ethynyl Complexes
Organometallics, Vol. 14,No. 6, 1995 2779 Scheme 3
C26
n
5
Figure 4. Molecular structure of 7b drawn at the 30% probability level. The numbers without the atom names are for the CO ligands. 7
Table 4. Selected Structural Parameters for 7ba Cl-C2 C1-Ru c1-Col
c1-co2 C1-Fe C2-RU
Bond Lengths 1.340(6) c2-Col 2.701(5) c2-co2 1.923(5) Ru-Col 2.120(5) Ru-CO~ 1.917(5) Col-co2 2.139(5) Col-Fe
2.849(5) 2.066(5) 2.731(1) 2.587(1) 2.532(1) 2.565(1)
Bond Angles C O ~ - C ~ - C O ~ 77.4(2) RuCol-Co2 58.73(4) C o l -Cl-Fe 83.8(2) RuCol-Fe 114.23(4) Col-Cl-C2 120.6(4) RuCol-Cl 68.4(2) COS-C1-Fe 128.7(2) Co2-Col-Fe 91.16(4) C02-Cl-C2 69.1(3) Co2-C0l-C1 54.8(1) Fe-Cl-C2 154.4(4) Fe-Col-C1 48.0(2) Ru-C2-C02 75.9(2) Cl-Co2-C2 37.3(2) Ru-C2-C1 99.3(3) Ru-Co2-Col 64.48(3) co2-c2-c1 73.6(3) Ru-Co2-Cl 69.2(1) Col-Ru-Co2 56.78(2) Ru-Co2-C2 53.3(1) Col-Ru-C2 70.4(1) C O ~ - C O ~ - C ~ 47.8(1) Co2-Ru-C2 50.8(1) C O ~ - C O ~ - C ~ 75.8(1) Col-Fe-C1 48.2(1)
Bond lengths in angstroms and bond angles in degrees.
RuCO~(CO)~O(LQ-C~P~) (8),llacan be viewed as a trimetalated ethylene n-coordinated to the fourth metal center (Figure 2b). The structure of the tetranuclear p~acetylidecluster compounds (the I-structure like 4a vs the //-structure like 7b) has been a subject of d i s c u s ~ i o n . ~Several ~J~ factors of the metal centers such as atomic radii, electron-donating ability, and electronic configuration have been assumed to be causes of the different structure. However, a definite conclusion has not been obtained so far, and a theoretical study is needed for the clear-cut description of the structure. Furthermore, as to the reason that the Fe and Ru atoms in the isoelectronic complexes 5 and 7 occupy different sites of the spiked-triangular metal array, we have no explanation at present. Thus the interaction of the ethynyl complex la,b with RuCoz(CO)11follows a reaction pathway similar to eq 1 to give the vinylidene cluster 6 at first, and then thermal decarbonylation leads to the formation of the acetylide cluster 7 with a structure considerably different from that of the Fe derivative 4. (11)(a)Bernhardt, W.; Vahrenkamp, H. J . Orgunomet. Chem. 1988, 355, 427. (b) Roland, E.; Bernhardt, W.; Vahrenkamp, H. Chem. Ber. 1986,119, 2566. (12) (a) Ewing, P.; Farrugia, L. J. Orgunmetullics 1989,8,1246. (b) Deeming, A. J.; Senior, A. M. J. Orgunomet. Chem. 1992, 439, 177.
1,2-H Shift on Tetranuclear CBHCluster Compounds. The results described above show that the reactions 1and 2 produce the vinylidene clusters MCo2(CO)gCU3-C=C(H)Fe(r5-C5R5)(C0)21 4 (M = Fe) and 6 (M = Ru) (paths a and c), which, upon thermal decarbonylation, are transformed to the acetylide clusters (r5C ~ R S ) F ~ M C O ~ ( C O ) ~5O(M ~ ~=-Fe) C ~and H ) 7 (M = Ru) (paths b and d),respectively, as summarized in Scheme 3. The transformations can be explained in terms of 1,2-H shift on the r2-alkynecluster intermediates MCo2( C O ) ~ ~ U ~ - ~ ~ : ~ ~ : ~ ~ - ( ~ ~ - C ~9 R(M ~ )=F Fe) ~(CO)~C’C and 10 (M = Ru). Addition of an “Fe(C0)2” fragment to the Co-Co bond in 3 (path e ) and the displacement of CO ligands in RuCoz(CO)11by (r5-C5R5)Fe(C0)2CsCH (path i) should form the intermediates 9 and 10, detection of which has been unsuccessful despite several attempts. However, the corresponding 1-alkyne clusters containing an organic group in place of the (v5-C5R5)Fe(C0)2 moiety in 9 and 10 were isolated and structurally c h a r a c t e r i ~ e d . ~The , ~ , subsequent, ~ very fast 1,2-H shift may give rise to the vinylidene clusters 4 (path f , and 6 (pathj). The intermediates 9 and 10 are also viable ones for the formation of the acetylide clusters 5 and 7 (paths b and d). The backward 1,2-H shift (paths g and k) may regenerate the intermediates 9 and 10, which, upon thermal decarbonylation, should be transformed irreversibly to the acetylide clusters 5 and 7 via metalmetal bond formation. These results show that the 1,2-H shift on the tetranuclear C2H complexes 4-7 (paths f-g and j-k) proceeds as fast as that on the diand trinuclear derivatives (Scheme 1). Although the forward 1,2-H shift giving the vinylidene structure on cluster compounds has been reported already,2 the backward process is confirmed by the present study for the first time. Experimental Section All manipulations were carried out under an argon atmosphere by using standard Schlenk tube techniques. Ether, THF, hexanes, and benzene (Na-K alloy) and CHzClz (PzOS) were treated with appropriate drying agents, distilled, and
Akita et al.
2780 Organometallics, Vol.14,No. 6,1995 stored under Ar. Organometallic compounds la,13lb,5a3a,5c 3b,5cFe2(C0)9,14and RuCo~(C0)11~ were prepared according to the literature procedures. Column chromatography and preparative TLC were performed on alumina [column, activity 11-IV (Merck Art.1097);PTLC, aluminum oxide 60 PF254 (Typ E) (Merck Art. 1103)l. 'H- and 13C-NMRspectra were recorded on JEOL EX-90 ('H, 90 MHz) and JEOL GX-270 spectrometers ('H, 270 MHz; 13C, 67.9 MHz). Solvents for NMR measurements containing 1% TMS were dried over molecular sieves and distilled under reduced pressure. IR and FDMS spectra were obtained on a JASCO FTAR 5300 spectrometer and a Hitachi M-80 mass spectrometer, respectively. Reaction of 3a with Fez(CO)s. A mixture of 3a (400 mg, 0.820 mmol) and Fez(C0)g (401 mg, 1.10 mmol) dissolved in benzene (20 mL) was stirred for 30 h at room temperature. After removal of the volatiles, the residue was subjected to PTLC separation (CHzClz/hexanes = 1:6). The tetranuclear adducts 4a (69 mg, 0.109 mmol, 13%yield) and Sa (138 mg, 0.230 mmol, 28% yield) were obtained from the brown (Rf = 0.8) and dark brown bands (Rf= 0.61, and 3a (139 mg, 0.285 mmol, 35% recovered) was recovered from the greenish yellow band ( R f =0.9). 5a: 'H-NMR (CDC13) 6 5.06 (5 H, s, Cp), 8.60 ( l H , S, C2H); 13C-NMR(CDC13)6 87.2 (d, 'JCH = 181Hz, Cp), 118.5 (d, 'JCH= 203 Hz, CsCH), 193.0 (s, CECH), 200-204 (br, Co-CO), 211.0, 214.0 (s x 2, Fe-CO), 245.9 @-CO); IR (CH2C12) v(C=O) 2078, 2036, 2027, 2010, 1973, 1838 cm-'; FDMS mlz 600 (M+). Anal. Calcd for C17H~010Fe~C02: C, 34.38; H, 0.93. Found: C, 34.04; H, 1.01. 4a: 'H-NMR (CDC13) 6 4.98 (5 H, S, Cp), 7.18 (lH, S, CzH); 13C-NMR(CDC13) 6 86.9 (d, 'JCH= 181Hz, Cp), 123.7 (d, 'JCH = 151 Hz, C=CH), 205.5, 209.6 (s x 2, FezCo-CO), 213.4 (9, Fp-CO); IR (CH2Cl2) v ( C ~ 02087,2041,2033 ) cm-'; FDMS mlz 628 (M+). An analytically pure sample was not obtained due to partial thermal decomposition. Reaction of 3b with Fez(C0)O. A mixture of 3b (156 mg, 0.279 mmol) and Fez(C0)~(407 mg, 1.12 mmol) dissolved in benzene (10 mL) was stirred for 7.5 h at room temperature. After removal of the volatiles, the residue was extracted with ether and filtered through a n alumina pad. Recrystallization from ether-hexanes gave 5b (108 mg, 0.161 mmol, 58% yield) as black crystals. 5b: lH-NMR (CDC13) 6 1.83 (15 H, s, Cp*), = 122 Hz, 8.68 ( l H , S, CzH). 13C-NMR(CDC13) 6 9.5 (4, 'JCH C a e s ) , 97.8 (s, C5Me5),115.7 (d, ~ J C =H 208 Hz, CECH), 206 (br, CO), 209-212 (br, Co-CO), 217.5 (s, Fe-CO), 247.3 @CO); IR (CH2C12) v(CG0) 2072,2027,2020,2004,1988,1963, 1827 cm-'; FDMS mlz 670 (M+). Anal. Calcd for 39.44; C ~ ~ H I ~ O I D FC, ~~ C O ~H,: 2.41. Found: C, 39.53; H, 2.36. Reaction of l a with RuCoz(CO)11. A benzene solution (15mL) of l a (118mg, 0.586 mmol) and RuCo~(C0)11(309 mg, 587 mmol) was stirred for 2 h at room temperature. After removal of the volatiles, the residue was extracted with ether and filtered through an alumina pad. Recrystallization from ether-hexanes gave 6a (198 mg, 0.294 mmol, 50% yield) as red brown crystals. 6a: 'H-NMR (CDC13)6 4.98 (5 H, s, Cp), = 180 Hz, 6.66 (lH, S, C2H); 13C-NMR(CDC13)6 86.8 (d, 'JCH Cp), 107.1 (d, 'JCH= 151 Hz, C=CH), 199.5 (s, RuCoz-CO), 214.0 (s, Fp-CO), 277.5 (9, C=CH); IR (CH2C12) v(CE0) 2087, 2046,2037,2015 cm-'. Anal. Calcd for Cl&&OtlFeRuCo2: C, 32.12; H, 0.90. Found: C, 32.33; H, 0.97. Thermal Decarbonylation of 6a Leading to 7a. A benzene solution (20 mL) of 6a (198 mg, 0.294 mmol) was refluxed for 2 h. After removal of the volatiles, the residue was extracted with ether and filtered through an alumina pad. Recrystallization from ether-hexanes gave 7a (128 mg, 0.197 mmol, 67% yield) as deep green crystals. 7a: 'H-NMR (CDCl3) 6 4.98 (5 H, S, Cp), 8.07 ( l H , S, C2H); 13C-NMR(CDC13)6 86.8 (d, 'JCH= 179 Hz, Cp), 106.2 (d, 'JCH= 196 Hz, CECH), 190194 (br, CO), 198.6 (s, CzCH), 201-208 (br, CO). IR (CH2(13) Kim, P.;Masai, H.; Sonogashira, K.; Hagihara, N. J. Inorg. Nucl. Chen. Lett. 1970, 6,181. (14)King, R. B. Organometallic Synthesis; Academic Press: New York, 1965; Vol. 1, p 93.
Cl2) v(C=O) 2086, 2045, 2025, 1997, 1833 cm-l. Anal. Calcd for C17H6OloFeRuCo2: C, 31.66; H, 0.94. Found: C, 31.67; H, 0.86.
Reaction of l b with RUCOZ(CO)~I. A benzene solution (15 mL) of l b (298 mg, 1.09 mmol) and RuCoz(CO)11(574mg, 1.09 mmol) was stirred for 1 h at room temperature. The formation of 6b was detected as a red orange spot by TLC. Then the mixture was heated for 17 h at 50 "C. After removal of the volatiles, the residue was extracted with CHzClz and filtered through an alumina pad. Recrystallization from CH2Clz-hexanes gave 7b (408 mg, 0.549 mmol, 55% yield) as red brown crystals. 6b: 'H-NMR (CDC13) 6 1.83 (15 H, s, Cp*), 6.59 (lH, S, C2H). 7b: 'H-NMR (CDC13)6 1.83 (15 H, S, Cp*), 7.98 (lH, S, CzH); 13C-NMR(CDC13) 6 9.3 (q, 'JCH= 122 Hz, Cae5), 98.2 (s, CsMes), 106.7 (d, 'JCH= 193 Hz, CECH), 198.9 (s, C=CH), 205-208 (br, Co-CO), 237, (s, Fe-CO), 254 @-CO); IR (KBr) v ( C ~ 0 2088, ) 2032, 2004, 1988, 1971, 1956, 1933, 1890, 1815 cm-'. Anal. Calcd for Cz2H16010FeRuCoz: C, 36.95; H, 2.26. Found: C, 36.70; H, 2.13. X-ray Crystallography of Sa, 6a, and 7b. The tetranuclear cluster compounds 5a and 6a were recrystallized from ether-hexanes, and 7b was recrystallized from CH2C12hexanes. Suitable crystals were mounted on glass fibers. Diffraction measurements were made on a Rigaku AFC-5R automated four-circle diffractometer by using graphite-monochromated Mo Ka radiation (1 = 0.710 68 A). The unit cell was determined and refined by a least-squares method using 20-24 independent reflections. Data were collected with an w-20 scan technique. If dF)/F was more than 0.1, a scan was repeated up to three times and the results were added to the first scan. Three standard reflections were monitored at every 150 measurements. The data processing was performed on a micro vax I1 computer (data collection) and an IRIS Indigo computer (structure analysis) by using the teXsan structure solving program system obtained from the Rigaku Corp., Tokyo, Japan. Neutral scattering factors were obtained from the standard source.15 In the reduction of data, Lorentz, polarization, and empirical absorption corrections (Y scans) were made. The structures were solved by a combination of the direct methods and Fourier syntheses (SAP191 and DIRDIF). The unit cell of 5a contained two independent molecules. All the non-hydrogen atoms were refined anisotropically. The C2H atoms were located by examination of the Fourier maps and were not refined. The hydrogen atoms of the Cp and Cp* ligands were fixed at the calculated positions (C-H = 0.95 A) and were not refined. The crystallographic data and selected structural parameters are summarized in Tables 1-4.
Acknowledgment. The financial support from the Ministry of Education, Science, and Culture of t h e J a p a n e s e Government is gratefully acknowledged (Grants-in-Aid for Scientific Research on Priority Area Nos. 04241105 a n d 05236103). Supplementary Material Available: Tables of positional and thermal parameters and bond lengths and angles for Sa, 6a, and 7b (16 pages). Ordering information is given on any current masthead page. OM950071K (15) International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, U.K., 1975; Vol. 4.
