2605
Organometallics 1996,14, 2605-2608
Photochemistry of Indenyliron Dicarbonyl Disilanes, (q5-CgH7)Fe(C0)2Size~Ph3, Involving Isomerization, e.g.
(q5-CgH7)Fe(CO)2SiMePhSiMePh2, Prior to Silylene (q6-CgH7)Fe(CO)2SiMe2SiPh3 Elimination Ziying Zhang, Ruth Sanchez, and Keith H. Pannell" Department of Chemistry, University of Texas at El Paso, El Paso, Texas 79968 Received January 19, 1995@
Summary: A series of triphenyl(dimethy1)disilane isomers substituted with indenyliron dicarbonyl, (r5C&7)Fe(CO)~Si.&feZph,have been synthesized and characterized. Photochemical treatment of the complexes in inert hydrocarbon solvents ultimately resulted in the formation of the appropriate monosilyl complexes, (r5C&,)Fe(Co)~siMe,Ph3-, (n = 0-2) via the elimination of silylene fragments. However, contrary to the results previously obtained with the cyclopentadienyl analogs, (r5-CgH5)Fe(C0)2Si2Mergh5-,, isomerization of the disilanes was observed prior to silylene elimination. The chemistry, which takes place via equilibrating intermediate silyl(sily1ene)iron complexes, e.g. (q5-CsH,)Fe(CO)(=SiMedSiPh~, indicates that silylene elimination, a photochemical event, is extremely sensitive to the nature of the ligands bonded to the transition metal. 1,3-Alkyl(aryl) shifts coupled with the recombination of the silicon-silicon bond that lead to isomerization occur more rapidly than the silylene elimination in the indenyliron complexes.
Introduction The chemistry of the silicon-silicon bond in transition metal-substituted oligosilanes has recently received considerable attention. 1-5 isomerization^,^^^^^^^^ migrations t o ancilliary ligands,2band silylene eliminations have been o b ~ e r v e d . ~Using ~ , ~ ~chemical ,~ substitutions t o investigate the mechanism in the case of oligosilane complexes of the (r5-C5H5)Fe(C0)2,Fp, system, such chemistry was proposed to occur via a series of equilibrating silyl(sily1ene)iron intermediates formed upon photoelimination of CO and by undergoing a series of @Abstractpublished in Advance ACS Abstracts, April 15,1995. (1)Sharma, H. K.;Pannell, K. H. Chem. Rev., in press. (2)(a) Pannell, K. H.; Rice, J. R. J. Organomet. Chem. 1974,78, C35. (b) Pannell, K. H.; Cervantes, J.; Hernandez, C.; Cassias, J.; Vincenti, S. Organometallics 1986,5,1056.(c) Pannell, K. H.; Wang, L.J.; Rozell, J. M. Organometallics 1989,8, 550. (d) Pannell, K. H.; Rozell, J. M.; Hernandez, C. J . Am. Chem. Soc. 1989,111, 4482.(e) Hernandez, C.; Sharma, H. K.; Pannell, K. H. J. Organomet. Chem. 1993,462,259. (0Jones, K. L.; Pannell, K H. J. Am. Chem. Soc. 1993, 115,11336.(g) Pannell, K H.; Sharma, H. Organometallics 1991,10, 954. (3)(a) Tobita, H.;Ueno, K.; Ogino, H. Bull. Chem. Soc. Jpn. 1988, 61,2979.(b)Ueno, K;Tobita, H.; Shimoi, M.; Ogino, H. J . Am. Chem. Soc. 1988,110,4092. (c) Tobita, H.; Ueno, K.; Shimoi, M.; Ogino, H. J. Am. Chem. Soc. 1990,112,3415.(d)Ueno, K.;Tobita, H.; Ogino, H. Chem. Lett. 1990,369.(e) Tobita, H.; Wada, H.; Ueno, K.;Ogino, H. Organometallics 1994,13,2545. (0 Ueno, K.;Ito, S.; Endo, K.; Tobita, H.; Inomata, S.; Ogino, H. Organometallics 1994,13,3309.(g) Ueno, K.;Hamashima, N.; Shimoi,M.; Ogino, H. Organometallics 1991,10, 959. (4)Haynes,A.; George, M. W.; Haward, M. T.; Poliakoff, M.; Turner, J. J.; Boag, N. M.; Green, M. J. Am. Chem. Soc. 1991,113,2011. ( 5 )Pannell, K. H.; Brun, M-C.; Sharma, H. K.;Jones, K.; Sharma, S. Organometallics 1994,13,1075.
0276-733319512314-2605$09.0010
1,3-methyl, -aryl, or -silyl, migrations.2b-fUsing alkoxyand amine-substituted disilanes, the OginoPTobita group isolated stable examples of this s ~ s t e mand , ~ the Turner group spectroscopically observed the intermediate (r5CsHs)Fe(CO)(=SiMez)SiMe3,using low-temperature matrix isolation and flash photolysis techniques? Recently, the silylene elimination from, and isomerization of, oligosilanes was effected using FpSiMes and (q5-C5H5)Fe(COI(PPh3)SiMescomplexes as ~ a t a l y t s t s . ~ Since the initial studies on the Fp systems, related 1,3-alkyl migrations in silyl(silylene) tungsten complexes have been observed by Pestana et and Fink and co-workers have observed similar chemistry occurring for platinum d i ~ i l a n e s . ~ In the case of the oligosilanes with a single Fp substituent, recombination of the Si-Si bond in the silyl(sily1ene)iron intermediates occurred only in the case of the oligosilanes containing at least three silicon atoms;2c,ehowever, recombination did occur upon photolysis of the bimetallic complex FpSiMezSiMezFp to form initially [(q5-CsH5)Fe(C0)1201-CO~-S~eSiMe3).2g~3g In an extension of the oligosilane chemistry to the analogous indenyliron complexes, (r5-CgH7)Fe(C0)2oligosilane, we reported that the photochemical reaction and PPh3 rebetween (r5-CgH7)Fe(C0)2SiMe2SiMe3 sulted in phosphine substitution with no de-oligomerization, eq 1;similar treatment of the related trisilane resulted in isomerization and phosphine substitution, eq 2.8 In neither case was SiMez elimination observed; therefore the results suggested that the indenyl ligand profoundly altered the photochemistry of the system. Since the disilane used was permethylated, isomerization was impossible to observe. On the basis of a preliminary observation of the chemistry of (r5-C9H7)Fe(CO)zSiMezSiMezPh,2gwe now report the synthesis of a series of isomeric disilane complexes (r5-CgH7)Fe(C0)zSizMezPhs and the results obtained upon photochemical irradiation in inert hydrocarbon solvents.
Experimental Section The syntheses of the isomeric complexes (q5-C9H7)Fe(C0)z(1);(q5-C&)Fe(C0)~SiaezPh, [(175-CgH7)Fe(CO)zSiMezSiPh3 SiMePhSiMePhz (2); and (q5-CgH7)Fe(CO)zSiPhaSiMezPh(3)l and the monosilane complexes (175-CsH7)Fe(CO)zSiMezPh (41, (175-CgH,)Fe(CO)zSiMePh~ (S),and (q5-CgH,)Fe(CO)~Sifi (6) (6)Pestana, D. C.; Koloski, T. S.; Berry, D. H. Organometallics 1994,
13,4173.
(7) Fink, M. J. Personal communication. (8) Pannell, K. H.; Lin,SH.; Kapoor, R. N.; Cervantes-Lee, F.; Pinon, M.; Pftrktinyi, L. Organometallics 1990,9,2454.
0 1995 American Chemical Society
2606 Organometallics, Vol. 14, No. 5, 1995
-?
Notes Table 1. Spectral and Analytical Properties of New ComDlexesa (q5-CgH7)Fe(CO)2SiMezSiPh3, 1: mp 141-142 "C.
zPh3Pw Fe-SiMe2SiMe,
+
CO
(1)
+
CO
(2)
PPhj
Fe-SiMe2SiMe2SiMe,
oc' c'
hv
.-b Ph3P
-
I)
\ ' C O
Fe-SiMe bMe
PhjP
Calcd (found): C, 68.37 (68.30); H, 5.18 (5.23) 23.9, -17.6 6.30 (SiMe); 72.5, 90.0, 105.5, 124.5,127.2, 128.3, 129.3,136.7,137.2(CgH7, Ph); 215.0 (CO) 'H 0.52 (SiMe); 4.50, 4.61, 7.1-7.7 (C9H7, Ph) IR 1996,1946 u v l v i s 392 (21301,322 (14 800) (q5-CgH7)Fe(CO)2SiF'hMeSiPh2Me, 2: Oil. Calcd (found): C, 68.37 (68.61); H, 5.18 (5.23) 29Si 19.0, -18.9 13c -2.67, 2.61 (SiMe); 72.2, 72.6,90.9, 105.0, 105.4, 124.1, 124.2, 127.0, 127.5, 127.7, 128.7, 134.1, 135.1, 138.1, 138.5, 144.9 (CgH7, Ph); 214.3,214.5 (CO) 'H 0.86, 0.92 (SiMe);4.29,4.55,6.7-7.7 (C9H7, Ph) 1999,1949 IR Wlvis 404 (18601,324 (11 100) (q5-CgH7)Fe(CO)zSiPhzSiPhMez.3: mD 121.5-122.5 "C. Calcd (found): C,-68.37 (68.31); H, 5.18 (5.21) 29Si 25.4, -16.7 13c -1.20 (SiMe), 74.2, 93.0, 105.7, 124.8, 127.7, 128.0, 128.1, 128.4, 128.9, 134.9, 135.9, 140.8, 143.3 (CgH7, Ph); 215.5 (CO) 'H 0.51 (SiMe), 4.29, 4.52, 6.8-7.8 (C9H7, Ph) 1997,1947 IR W l v i s 402 (3510), 336 (17 700) (q5-CgH7)Fe(CO)2SiPhMe2,4: mp 70-71 "C. Calcd (found): C, 62.99 (63.23); H, 5.08 (4.95) 29Si 41.3 13c 5.55 (SiMe); 72.7,93.2, 105.6, 124.4, 127.0,128.6,133.1, 133.5, 147.1 (CgH7, Ph); 215.3 (CO) 'H 0.68 (SiMe); 4.26,6.8-7.7 (CgH7, Ph) 1995,1944 IR Wlvis 376 (3970), 296 (22 800) (q5-C9H7)Fe(CO)zSiPh2Me,5: mp 82-84 "C. Calcd (found): C, 67.99 (68.41), H, 4.75 (5.10) 29Si 39.6 13c 5.48 (SiMe); 73.7,92.8, 105.8, 124.7, 127.5, 128.0, 128.6, 134.5, 144.0 (CgH7, Ph); 215.0 (CO) 'H 0.91 (SiMe); 4.39, 4.46, 6.8-7.8(CgH7, Ph) IR 1998,1948 W l v i s 378 (20101,292 (16 400) (q5-CgH7)Fe(CO)zSiP~, 6: mp 166-167 "C. Calcd (found) C, 71.61 (71.87); H, 4.56 (4.87) 29Si 40.1 13c 74.4, 92.6, 105.9, 124.8, 128.0, 128.7, 130.1, 135.8, 142.4 (CgH7, Ph); 215.5 (CO) 'H 4.82, 7.3, 7.5 (C9H7, Ph) 2001,1951 IR u v l v i s 378 (2140),300 (14 100) 2gSi '3C
3
were performed using the same general procedure used for the cyclopentadienyl analogs, substituting [(q5-CgH7)Fe(CO)21~ for [(q5-C5H5)Fe(CO)2]2.8A typical synthetic procedure is outlined below, and the spectroscopic and analytical data for the new complexes are recorded in Table 1. Synthesisof ($s-CsH,)Fe(CO)zSiPhaS~e~h. Into a 250 mL round-bottomed flask equipped with a side arm was placed 4 mL of Hg and 0.15 g of freshly cut Na metal. To this amalgam was added 1.0 g (2.2 mmol) of [(q5-C9H7)Fe(CO)212 in 60 mL of THF. After vigorous shaking for 1 h the violet solution changed to orange and infrared spectroscopyindicated the presence of the required salt [(q5-CgH7)Fe(C0)2]-Naf,(Y(CO) 1883, 1866, 1815, 1780 cm-l). Excess amalgam was drained via the side arm, and a solution of ClSiPhzSiMe~Ph (1.47 g, 4.2 mmol, in 5 mL of THF) was added slowly to the stirred salt solution a t 0 "C over a 30 min period. The solution was permitted to warm to room temperature and stirred for 3 h. Infrared spectroscopy at this time indicated complete removal of the salt and the appearance of new carbonyl bands at 1997 and 1947 cm-l indicative of a silicon-iron c ~ m p l e x . ~ The solvent was removed in uacuo, and the resulting oil was dissolved in 60 mL of a hexandmethylene chloride (9:l)solvent mixture. This solution was concentrated to 5 mL and placed upon a 2.5 x 15 cm silica gel column (MCB Reagents, grade 950, 60-200 mesh). Elution with hexane resulted in the development of a yellow band that was collected and (subsequent to the removal of the solvent and recrystallization of the resulting residue from hexane) yielded 0.64 g (1.2 mmol, 28%)of (q5-C9H7)Fe(CO)2SiPh2SiMe2Ph, 3, mp 121.5-122.5 "C. Photolysis and Product Analysis of a C a s Solution of (qs-C&)Fe(CO)&iPh&iMeaPh. This was performed using two different experimental setups, and an example of each is detailed below. We made no general attempt t o recover, separate, and purify the photoproducts and starting materials in such reactions. In a single experiment, of type A below, after 5 h of irradiation of 1 and subsequent to column chromatography as outlined in the syntheses described above using a 1 x 6 cm column, we recovered 75%of the material as a mixture of 1-6. A. A solution of 0.1 g of 3 in C& (0.6 mL) was sealed into a Pyrex N M R tube in uacuo. The solution was irradiated by a Hanovia 450 W medium pressure lamp, a t a distance of 10 cm and was monitored by 'H, 13C,and 29SiNMR spectroscopy. After 1 h of irradiation, in addition to the 29Siresonances a t 25.4 ppm (Fe-Si-Si) and -16.7 ppm (Fe-Si-Si) due to the (9) Pannell, K. H.; Wu,C. C.; Long,G . J.J.Orgummet. Chem. 1980, 186,85.
aMelting points are uncorrected; NMR spectra (ppm) were recorded in CsD6; IR (cm-') and W [nm ( E ) ] spectra were recorded in n-hexane; analyses were performed by Galbraith Laboratories. starting material, two new resonances were observed due to the formation of (q5-CgH7)Fe(CO)2SiMePhSiMePhz (21,. 19.0 ppm (Fe-Si-Si) and -18.9 ppm (Fe-Si-Si). As irradiation continued, the resonances associated with the starting material became progressively less intense, while those of isomer 2 became dominant. Subsequently, after 5 h of irradiation, the appearance of a resonance indicative of (q5-C9H7)Fe(C0)2SiMePh2 (39.6 ppm) was observed. At this stage the solution was analyzed by high-pressure liquid chromatography (Beckmann llOB with UV detector at 254 nm) using a CISreversed phase column (Beckmann Ultrasphere 23529, 4.6 mm x 25 cm) using a solvent mixture of 80:20 (vh) CH3CN/H20, with a flow rate of 2.5 mumin. This analysis exhibited the presence of all three isomers of the starting disilane, and each of the three possible monosilane complexes, (q5-C9H7)Fe(C0)~R, R= SiMezPh (4), SiMePhz (51, and SiPh (6).The relative amounts of the six complexes from this reaction, and from separate photochemical reactions of the other isomers 2 and 3, are presented in Table 2.
Organometallics, Vol. 14, No. 5, 1995 2607
Notes
Table 2. Relative Yields of Photoproducts, HPLC Analysis, after 5 h product 1 2 3 4 5 (r15-CgH,)Fe(C0)2SiMezSiPh3 2 13 7 19 2 (q5-CgH7)Fe(C0)2SiMePhSiMePhz 1 20 12 33 3 (r,-5-CgH7)Fe(CO)~SiPh~SiMe2Ph 1 25 14 35 5 reagent
/Fe-Si2Me2Ph3
6
2:s
1 1.8:l 1 1.7:l 1 1.8:l
B. A solution similar to that described above was irradiated in a 5 mL Pyrex flask and monitored directly via HPLC, and the relative amounts of the isomers and products were determined. Under the HPLC conditions noted above, the retention times observed for the six complexes were such that a perfect analytical separation could be observed. The retention times ( m i d were as follows: (v5-C9H7)Fe(C0)2SiMezPh (4), 5.04;(rl5-CgH7)Fe(CO)zSiMePhz (5), 5.53;(t;15-CgH7)Fe(C0)2S i P b (6), 6.88; (q5-C9H7)Fe(C0)2SiMePhSiMePhz (2),12.8; (q5CgH7)Fe(CO)zSiPhzSiMezPh (3),14.3; (r16-CgH7)Fe(CO)zSiMezSiPh3 (11,15.8.
Results and Discussion The syntheses of the new complexes were readily achieved in moderate yields via the standard saltelimination reaction illustrated in eq 3.
Fe-S$Me2PS
+NaCl
(3)
oc' The spectroscopic and analytical data, in accord with the assigned structures, are recorded in Table 1. The 29Si"R data follow the same pattern exhibited by the corresponding cyclopentadienyl complexes when compared to their respective methyl analogs. Thus, the Si atoms bonded directly to the Fe atom, Si,, exhibit significant low-field shifts (45-35 ppm) compared to the methyl analog, while those in the /?-position exhibit lesser shifts (12ppm). Photochemical treatment of the disilane complexes ultimately resulted in chemistry identical to that noted for the cyclopentadienyl analogs, i.e. formation of the various monosilyl complexes (v5-CgH7)Fe(C0)2SiR3,SiR3 = SiMezPh (41, SiMePh2 (E), SiPh3 (6). The average ratio of the three complexes formed, independent of which isomer was photolyzed, was 4:5:6 = 1:30:4.The rate of formation of these final photoproducts was slower than that observed for the cyclopentadienyl analogs, and prior to their formation, and loss of the silylene fragment, we observed the isomerization of each of 1,2,or 3 into a photostationary mixture of all three isomers, i.e. eq 4 and Scheme 1. The average isomer ratio after 5 h of irradiation was 1:2:3= 1:15:8. The substitution of the cyclopentadienyl group by the indenyl group altered the progress of the reaction by retarding the elimination of the silylene fragments from the equilibrating silyl(sily1ene)intermediates (~7~-CgH7)Fe(CO)(=SiR2)SiR3. This permits the recoordination of CO to cause the re-formation of the Si-Si bond, i.e. isomerization. Since the Turner group demonstrated
+
"6
(.
