Starting from [q5-C5Br5]M n(CO),, the first
r-complex of a cyclopentadienyl ligand with five silyl
substituents, [q 5-C5(SiMe2H)5M] n(CO),, was prepared by
a series of halogen-lithium exchange reactions, followed
by silylation with SiMe2HCI. The crystal structure determination of this compound shows a highly symmetrical
"paddle wheel" orientation of the five silyl groups around
the cyclopentadienyl ring

Hofmann, Julian

Sünkel, Karlheinz

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Coordination chemistry of perhalogenated cyclopentadienes and alkynes. 8. Pentakis(dimethylsilyl)cymantrene

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Organometallics 1992, 11, 3923-3925 Coordination Chemistry of Perhaiogenated Cyciopentadienes and Karlheinz Sunkel' and Julian Hofmann Institut f"ur Anorganlsche Chemk der Universfit, hMwrstrasse 1, PBOOO Munlch 2, Germany Received June 8, 1992 Alkynes. 8. ' Pent a kis (dimet h ylsii y i) cymant renet Summary: Starting from [q5-C5Br5] Mn(CO),, the first r-complex of a cyclopentadienyl ligand with five silyl substituents, [ q5-C5(SiMe2H)5] Mn(CO),, was prepared by a series of halogen-lithium exchange reactions, followed by silylation with SiMe2HCI. The crystal structure deter- mination of this compound shows a highly symmetrical "paddle wheel" orientation of the five silyl groups around the cyclopentadienyl ring. Introduction Polysilylated cyclopentadienyl ligands have been of in- terest over the past decade. Increasing the number of silyl substituents is believed to enhance the solubility in non- polar solvents and the volatility of the compounds and to increase their kinetic stability. Thus, a series of stable r-cyclopentadienyl complexes of main-group elements and lanthanides or actinides with the [C6(SiMe3)3H2] ligand could be obtained? However, attempts to introduce more than three SiMe3 group into the cyclopentadienyl system thus far have been unsucceaaful.9 We report here the fmt ?r-complex containing a &fold silylated cyclopentadienyl ligand. Results and Discussion We showed recently that starting from [(C6CI4Br)Mn- (CO),] (I), the consecutive introduction of five SMe group into the cyclopentadienyl ligand can be achieved by re- peated alternate d o n  with n-butyllithium and dimethyl disulfide.' When other electrophiles are used, multiple substitution in 1 worke only when electrophiles containing donor atoms such as S, Se, or P are used. However, in the case of the related [(C,Brs)Mn(CO),] (2)6 all the bromine atoms can be substituted stepwise by the SiMezH group (Scheme I). Double lithiations can be performed for each of the compounds 2-6. Thus, 7 can be prepared in three steps from 2 in an overall yield of about 60%. All derivatives [CsBr&3iMezH)n]Mn(C0)3 with n = 1-5 are air-stable, crystalline powders, that are very soluble in hexane and can be obtained in good to excellent yields. Their lH NMR spectra show the minimum number of signals that can be expected from symmetry considerations. This means ob- viously that in all compounds, even in the sterically crowded 6 and 7, a rapid rotation of the silyl group around the ring-silicon bond must occur. Comparable sterically congested systems such as Cr- (CO)3[Ce(SiMe2H)6],6 [Cs~Pr)61CoCp+,' and [CS(WSI- 'Dedicated to Prof. Wolfgang Beck on the occasion of his 60th birthday. (1) Part 7: Sbkel, K. Chem. Ber. 1991,124, 2449. (2) For a review, see: Jutzi, P. J. Organomet. Chem. 1990,400,1, and literature cited therein. (3) The synthesis of C6(SiMe& was reported in a short communica- tion: Miftakhot, M. S.; Toletikov, G. A.; Lo", 5. I. Zh. Obehch. Khim. 1976,46, 2751, Chem. Abstr. 1977,86, 1214302. (4) Slfnkel, K.; Mob, D. Angew. Chem., Znt. Ed. Engl. 1988,27,934. (5) Nefedov, V. A. Zh. Org. Khim. 1978, 9, 719. Herrmann, W. A., Huber, M. J. Organomet. Chem. 1977,140,55. (6) Schuater, I. I.; Weiaeensteiner, W.; Mislow, K. J. Am. Chem. SOC. 1986,IoB,6661. 0276-73331 92/23l1-3923%03.OOl 0 3923 C41 c22 C Figve 1. Molecular structure of 7 (thermal ellipsoids on the 20% probability level; the picture shows the higher populated A form). Averaged bond lengths (A): Mn-(ClA45A) 2.17 (1); C 4  1.46 (1); C*-Si 1.87 (1); Si-&:, 1.88 (1). MO(CO)~M~~ show strongly temperature-dependent NMR spectra with internal rotation barriers ranging from 56 to 72 kJ/mol. Cooling a toluene solution of 7 results in broadening of the 'H NMR doublet for the methyl groups until one broad resonance is observed at -80 "C. Going down to -90 "C, which is the lowest reasonable tempera- ture achievable in this solvent, resulta in two broad signals without any fine structure. This leads to an approximate AG* value of 40 kJ/mol. In comparison to the above- mentioned compounds, this is a much lower value which means the steric hindrance is here not as great as might have been expected. All SiMezH group show the same "paddle wheel" orientation with the Si-H bond lying in the plane of the cyclo- pentadienyl ring. Compound 7 is therefore chiral. In- terestingly, there is an obvious disorder in the silicon positions, which also can be resolved for the ring carbon atoms but not for the methyl groups. The site occupancy factors can be refined to values of 0.740.26, which means that both enantiomers are distributed statistically over the four symmetq-equivalent positions of the unit cell and not in special pairs, as would be demanded by crystallographic symmetry. Similar observations have been reported for Figure 1 shows the solid state structure of 7.9 (7) Gloaguen, B.; Aetruc, D. J. Am. Chem. SOC. 1990,112,4807. (8) Sitzmnnn, H. Chem. Ber. 1990, 123, 2311. (9) In the fmt difference Fourier synthesis after the whole molecule had been identified, five maxima of electron density were found in a distance of about 1 A from each of the Si atoms in the plane of the cyclopentadienyl ring. Refinement of these positions 88 site B for the silicon a tom lead to relative site occupancy factors of 31 for AB, but no new poeitions for the corresponding five ring C atom could be located. However, the appearance of the corresponding thermal ellipsoids indi- cated that there were two carbon positions as well. By fuing the sof s of the found carbon sitea to 0.5 and the isotropic thermal parameters to 0.02 A*, a new difference Fourier synthesis could localize the B site for the ring carbons as well. Isotropic refinement of the C and Si positiom with the restriction of common thermal parameters for each A-B pair yielded a fmal sof of 0.74 for site A. No B sitea for the methyl  bo^ could be localized; nor could any hydrogen positions. Thus, only one methyl carbon site was u a d  in refinement and hydrogens were omitted at all. Q 1992 American Chemical Societv 3924 Organometallics, Vol. 11, No. 11, 1992 Scheme I" Notes Table I. CrvstallomaDhic Data for 7 formula space group cryst syet a, A b, A c ,  A v, A3 diffractometer mono- chromator scan technique radiation A, A 28 range, deg std rflns Program abs corr minimax transm R, % &(d, e A-3 Crystal Parameters CI8H,MnO3Si5 2 Pna2, cryst dimens, orthorhombic cryst color 19.329 (13) D(calc), g/cm3 10.693 (6) p(Mo Ka), cm-I 13.200 (3) temp, OC 2728 (3) Data Collection Nicolet R3 rflns collcd graphite indpt rflns R(merg), % w-2e indpt rflns obsd Mo Ka F, 1 40(F") mm 0.710 73 data collcd 2-20 20-50 2 std/98 rflns SHELXTL PLUS 4.11/V empirical ($ scan) 0.388/0.502 5.3 R,, % 0.71 w-1 = aZ(F,) + Refinement 0.0005(F0)2 4 0.50 X 0.50 X 0.15 yellow 1.119 6.91 18 3955 2670 3.98 2308 kh,kk,kl  +h,+k,+l 6.54 the benzene derivativea c6(cHR& (R = C1, Me)'O and very recently, for the [C$Pr6] radical." The C6 ring in 7 show no deviation from planarity. Two silicon atoms in 1,3 position are shifted out of this plane by 30 pm away from the manganese atom, while the silicon atom in between is situated 12 pm on the proximal side of the ring. Thus the steric interaction between the silyl groups becomes min- imized. 7 contains not only a 5-fold silylated cyclopentadienyl ring but also five Si-H groups that might be used for further functionalization. Complexes with the [C6H4- (SiM%H)] ligand have been used in the hydrosilylation of alkyneP aa well aa of metal carbonyls.l3 Use of com- (10) Siegel, J.; Gutierrez, A.; Schweizer, W. B.; Ekmer, 0.; Mielow, K. J. Am. Chem. SOC. 1986,108,1569. Kahr, B.; Biali, 5. E.; Schaefer, W.; Buda, A. B.; Mielow, K. J. Org. Chem. 1987,52,3713. (11) Sitzmann, H.; Boeee, R. Angew. Chem., Znt. Ed. Engl. 1991,30, 971. (12) Dr&smar-Wolf, M. Cmelin Handbook of Inorganic Chemistry, 8th ed.; Organoiron Compounds Part A, Ferrocene 9; Springer-Verlag: Berlin, 1989; p 305. Table 11. Positional (XlO') and Equivalent Isotropic Thermal Parameters (A* x 13) X 1432 (1) 1625 (5) 1279 (5) 602 (5) 541 (5) 1164 (5) 2486 (1) 1570 (2) -149 (2) -173 (1) 1314 (2) 1564 (15) 1453 (15) 740 (18) 475 (14) 958 (16) 2308 (4) 2033 (4) 294 (5) -387 (4) 819 (5) 3123 (4) 2382 (5) 2349 (5) 1631 (6) -74 (5) -366 (5) -938 (4) -395 (5) 563 (6) 1523 (5) 2313 (4) 2886 (3) 1438 (5) 1456 (4) 1191 (4) 1040 (3) Y 928 (1) 509 (8) 1707 (8) 1478 (11) 181 (7) -454 (10) 255 (3) 3265 (3) 2613 (3) -648 (3) -2178 (2) 57 (26) 1415 (27) 1661 (32) 601 (26) -454 (28) -780 (8) 2604 (7) 3240 (7) 293 (9) -2165 (7) -725 (9) -356 (9) 3926 (7) 3266 (9) 4006 (8) 3126 (9) -882 (8) -2903 (7) -3035 (7) 1287 (7) 1528 (6) -164 (9) -852 (7) 2094 (8) 2822 (7) 42 (9) z 0 1581 (8) 1498 (8) 1023 (10) 785 (8) 1157 (9) 2182 (3) 1966 (3) 962 (3) 101 (3) 1280 (3) 1512 (22) 1602 (22) 1094 (29) 807 (23) 980 (24) 2077 (7) 2176 (7) 1284 (7) 154 (9) 766 (7) 1423 (8) 3495 (7) 1375 (8) 3391 (7) 2287 (8) 944 (9) -1159 (7) 1962 (9) 71 (9) -234 (6) -409 (6) -998 (6) -1667 (6) -900 (7) -1489 (6) 67 (10) pounds 3-7 in such reactions should res+ in a variety of interesting, novel polyfunctionalized cyclopentadienyl complexes. Compound 7 can be expected to be a key intermediate in the synthesis of persilylated cyclo- pentadienyl ligands. Experimental Section All reactions were carried out under nitrogen with standard Schlenk tube techniques. Solvents were dried according to standard procedures and saturated with nitrogen. For the  (13) E.g.: Colomer, E.; Corriu, R. J. P.; Pleixats, R. J. Orgonomet. Chem. 1990,381, C1. Notes Organometallics, Vol. 11, No. 11, 1992 3926 Table 111. Important Dirtances (A) and Angles (de& in 7 C(lA)C(M) 1.472 (14) C (1A)C (2A) 1.449 (12) C(2A)-C(3A) 1.472 (14) C(3A)C(4A) 1.426 (14) C(4A)-C(SA) C (2A)-Si(2A) 1.864 (9) C(3A)-Si(3A) C(5A)SYSA) 1.873 (11) C(PA)-C(lA)-C(5A) 108.0 (8) C (4A)C (5A)C( 1A) 107.5 (8) C(2A)C(3A)C(4A) 109.2 (9) chromatographic separations Kieselgel60 from Merck was used. 2 was prepared from Mn(CO)&r and C&N2 according to a literature procedure! n-Butyllithium was purchased as a 1.6 M solution in hexane from Aldrich. SiM+HCl (Fluka) was distilled from CaH2 under nitrogen. For details of the crystal structure determination, see Table I. Positional and thermal parameters of all atoms are included in Table II; important distances and angles are in Table 111. Preparation of 3. With continuous stirring, 1.04 mL of BuLi solution (1.66 "01) was added to a solution of 1.0 g of 2 (1.67 "01) in 20 mL of EBO at -76 OC. After 30 min, 0.18 mL of SiMhHCl(l.67 "01) was added, and then the temperature was gradually raised to ambient temperature during 14 h. After evaporation of the solvent in vacuo, the reaidue was ertmcted with hexane, the extracts were evaporated, and the residue was chromatographed on silica gel (2.5 cm X 10 cm, eluent hexane). Rscrystallization of the eluate yielded 0.87 g of analytically pure product (91%), mp 100-102 OC. 'H NMR (270 MHz, c a s )  6 = 0.215 (d, 3J(H,H) = 3.9 Hz, 6 H, SiCHd, 4.548 (sept, 3J(H,H) = 3.9 Hz, 1 H, SiH). I3C NMR (68 MHz, C a s )  6 = -2.7 (SiCHs), 2169 w (Si-H), 2039 vs, 1969 va (MnC-0). Cl&Br4Mn03Si (577.80) (calcd/found) C 20.79/21.02, H 1.22/1.30. Preparation of 4. A solution of 0.50 g of 2 (0.84 mmol) in 10 mL of JZt& waa treated with 1.05 mL of BuLi solution (1.68 "01) at -76 OC with continuous stirring. After 35 min, 0.18 mL of SiMe2HCl (1.67 mmol) was added. The temperature was raised to 20 OC during the course of 14 h. M e r  workup was performed as described for 3, yield 0.45 g (92%), mp 96-98 OC). 'H NMR (270 MHz, C a d  6 0.279 (d, 3J(H,H) 3.9 Hz, 6 H, SiCH3), 0.312 (d, 3J(H,H) = 4.0 Hz, 6 H, SiCHd, 4.697 (sept, 3J(H,H) = 3.9 Hz, 2 H, SM). 'v NMR (100 MHz, C a d  6 = -3.11, -2.43 (SiCH3), @6.14,97.15,101.92 (r-C&, 223.0 (Mn-CO). IR (hexane) v [cm-'I = 2169 w (Si-HI, 2035 ~8 ,1966 VB (MnC-0). ClzHllBr3Mn03Siz (557.05); C, 25.87/26.36; H, 2.53/2.61. Preparation of 5. In a manner similar to the synthesis of 4, compound 5 is obtained from 3 by double lithiation: A solution of 0.58 g of 3 (1.00 "01) in 10 mL of Ef20 was treated with 1.25 mL of BuLi solution (2.00 "01) at  -76 OC. After 30 min, 0.22 mL of SiMe2HCl(2.01 mmol) was added. After workup, 0.42 g of 5 was obtained (78%), mp 62.5 OC, 'H NMR (400 MHz, C a d  6 = 0.250 (d, 3J(H,H) = 3.7 Hz, 6 H, SiCHB), 0.368 (d, 3J(H,H) = 3.9 Hz, 6 H, SiCHS), 0.415 (d, 3J(H,H) = 4.2 Hz, 6 H, SiCHa), 4.723 (aept, 3J(H,H) = 3.9 Hz, 2 H, SiH), 4.806 (sept, 3J(H,H) 80.6, 90.2, 94.9 (r-C&), 222.4 ( f i c o ) .  IR (Nujol) Y [cm-'1 = 3.9 Hz, 1 H, SM). '9 NMR (100 MHz, C a d  6 = -1.74, -2.55, 1.467 (14) C(lA)-Si(la) 1.864 (10) 1.894 (11) C(4A)-Si(4A) 1.872 (10) C(lA)C(2A)C(3A) 107.2 (8) C(3A)C(4A)C(SA) 108.0 (9) -2.78 (SiCHd, 89.57,94.20, 105.62 (r-C&), 223.6 (fi-Co). IR (hexane) v [cm-'1 = 2166 w (Si-HI, 2030 vs, 1960 VB, 1955 VB (MnC-0). C14HzlBrzMn03Si3 (536.30): C, 31.35/31.16; H, 3.95/4.10. Preparation of 6. Starting from 4,6 was prepared by double lithiation: 0.40 g of 4 (0.72 mmol), dissolved in 10 mL of EBO, was treated with 0.90 mL of BuLi solution (1.44 "01) at  -76 OC. After addition of 0.16 mL of SiMezHCl (1.44 "01) and the usual workup procedure, 0.29 g of 6 was isolated (78%), mp = 3.9 Hz, 6 H, SiCH3), 0.327 (d, 3J(H,H) = 3.9 Hz, 6 H, SiCH3), 0.402 (d, 3J(H,H) = 3.9 Hz, 6 H, SiCH3), 0.502 (d, 3J(H,H) = 3.9 Hz 6 H, SiCH3), 4.562 (m, 2 H, SiH), 4.676 (m, 2 H, SiH). I3C NMR (100 MHz, c a s )  6 = -0.89, -1.15, -1.30, -2.37 (SiCH3), 96.91, 106.41, 110.93 (r-C6R6), 224.3 (Mn-CO). IR (hexane) v [cm-'1 = 2162 w (Si-H), 2023 vs, 1952 vs, 1945 vs (MnC-0). Cl~H&rMn03Si4 (515.55): c, 37.27/36.98; H, 5.47/5.61. Preparation of 7. To a solution of 1.79 g of 5 (3.33 "01) in 20 mL of N O ,  4.58 mL of BuLi solution (7.33 mmol) was added at -76 OC. After stirring for 45 min, 0.80 mL of SiMezHCl (7.33 "01) was added and the temperature was raised to 20 OC during the course of 14 h. After the usual workup procedure, a yield of 1.40 g of light yellow crystals were obtained (85%), mp 121-123 3.9 Hz, 30 H, SiCH3), 4.539 (sept, 3J(H,H) = 3.9 Hz, 5 H, SiH). '9 NMR (68 MHz, C a d  6 = 4 . 7 3  (SiCHd, 109.32 (r-cdia), 226.0 (Mn-CO). Low-temperature 'H NMR (90 MHz, toluene-d8): coaleacence of the doublet at 0.45 ppm is observed at -80 OC, at -90 OC two broad signals with a distance of approximately 27 Hz c8n be seen. IR (hexane) v [cm-'] = 2157 w (Si-H), 2017 VB, 1940 VB (MnC-0). C18H~MnO& (494.80): C, 43.69/43.33; H, 7.13/6.98. Acknowledgment. We are greatly indebted to Prof. W. Beck for providing us with laboratory space and fi- nancial support. This work also was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. Supplementary Material Available: Tables of atomic co- ordinates, bond lengths, bond anglea and anisotropic displacement coefficienta (8 pages). Ordering information is given on any current masthead page. OM920322E 101-103 "C. 'H NMR (270 MHz, C a s )  6 = 0.319 (d, 'J(H,H) OC. 'H NMR (400 MHz, 25 OC, C a s )  6 0.437 (d, 'J(H,H) 

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Coordination chemistry of perhalogenated cyclopentadienes and alkynes. 8. Pentakis(dimethylsilyl)cymantrene

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