Organometallics 1996, 14,4431-4434
4431
Reaction of a tert-Butyl-SubstitutedIron(0) Alkynyl(ethoxy)carbene Complex with Dimethylamine Jaiwook Park* and Jinkyung Kim Department of Chemistry and Center for Biofunctional Molecules, Pohang University of Science and Technology, S a n 31 Hyoja-Dong, Pohang, Kyung-Buk 790-784, Republic of Korea Received May 4, 1995@ Summary: The reaction of [(3,3-dimethylbutynyE)ethoxymethylenelFe(C0)4 (1) with dimethylamine was investigated. [(3,3-Dimethylbutynyl)(dimethylamim)methykn.e1Fe(CO)4 (2) was formed in 95% yield by substitution of the ethoxy group a t -78 "C. Meanwhile, the r3-(2-(tertbutylcarbony1)vinyl)carbene complex (3) was produced a t 25 "C in 96% yield through the Michael-type addition of dimethylamine and subsequent rearrangements. The a1kynyKamino)carbene complex 2 was further reacted with dimethylamine in acetonitrile a t 25 "C to give the v3-vinylcarbene complex 4 analogous to 3. Under CO pressure 3 and 4 were converted slowly to (y4-a-pyrone)Fe(CO)3 complexes 5 and 6. Metal alkynylcarbene complexes have attracted interest due to their distinct properties and potentials in synthetic organic chemistry.l For group 6 metal alkynylcarbene complexes, reactions with amines have shown a variety of reactivities depending on reaction conditions.1e,2 Substitution reaction a t the carbene carbon competes with the reaction at the P-carbon of the alkynyl group to give a n alkenylcarbene complex and a 3-aminoallenylidene complex.2 The selectivity varies considerably with reaction temperature as well as participating amines and alkynylcarbene complexes. As a part of our research on (alkynylcarbene)Fe(C0)4 c ~ m p l e x e sthe , ~ reaction with amines was investigated. tert-Butyl-substituted alkynylcarbene complex 1 and dimethylamine were chosen for convenient manipulation and easy analysis. The reaction a t -78 "C proceeded in a pathway similar t o those of group 6 metal alkynylcarbene complexes.4 However, the reaction pathway changed dramatically a t 25 "C. An unexpected product was obtained through a complex rearrangement in almost quantitative yield.
Results and Discussion The reaction pathways were affected greatly by temperature (Scheme 1): At -78 "C, substitution reaction Abstract published in Advance ACS Abstracts, August 1, 1995. (1)( a ) Wulff, W. D. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press: New York, 1990;Vol. 5.(b) Wulff, W. D. In Advances in Metal-Organic Chemistry; Liebeskind, L. S., Ed.; JAI Press Inc.: Greenwich, CT, 1989;Vol. 1. (c) Duetsch, M.; Vidoni, S.; Stein, F.; Funke, F.; Noltemeyer, M.; de Meijere, A. J.Chem. Soc., Chem. Comm., 1994,1679.(d) Funke, F.; Duetsch, M.; Stein, F.; Noltemeyer, M.; de Meijere, A. Chem. Ber. 1994,127,911.(e) Rahm, A.;Wulff, W. D. Organometallics 1993, 12, 597. (B Duetsch, M.; Lackmann, R.; Stein, F.; de Meijere, A. Synlett 1991,324. (2)(a)Stein, F.; Duetsch, M.; Pohl, E.; Herbst-Irmer, R.; de Meijere, A. Organometallics 1993,12,2556.(b) Duetsch, M.; Stein, F.; Funke, F.; Pohl, E.; Herbst-Irmer, R.; de Meijere, A. Chem. Ber. 1993,126, 2535. (3)( a ) Park, J.;Kang, S.; Won, C.; Whang, D.; Kim, K. Organometallics 1993, 12, 4704. (b) Park, J.; Kang, S.; Whang, D.; Kim, K. Organometallics 1992,11,1738.(c) Park, J.; Kang, S.;Whang, D.; Kim, K. Organometallics 1991,10,3413.(d) Park, J.;Kang, S.; Whang, D.; Kim, K. Taehan Hwahakhoe Chi 1992,36,770. (4) Fischer, E. 0.; Kalder, H. J. J. Organomet. Chem. 1977,131, 57. @
c15 Figure 1. Structure of 3 with the atom-labeling scheme.
a t the carbene carbon was completed in 5 min to give the alkynyl(amin0)carbene complex 2 in 95% yield. However, at 25 "C, (r3-(p-(tert-butylcarbonyl)vinyl)carbene)Fe(C0)3complex 3 was obtained in 96% yield within 2 min. At 0 "C a mixture of 2 and 3 was obtained in a 1:5 ratio. The substitution product 2 underwent an addition reaction to give 4 in 91% yield, which is analogous to 3,by treatment with another equivalent of dimethylamine in acetonitrile at 25 "C. Under moderate CO pressure (30 psi) at 25 "C, complex 3 in 1,2-dichloroethane was slowly transformed to the (q4a-pyrone)Fe(CO)s complexes 5 in 77% yield. The yield decreased with increasing reaction temperature as well as with decreasing CO pressure. However, the reaction of 4 with CO was so slow at 25 "C that the reaction mixture was heated to 80 "C for 19 h t o give 6 in 81% yield. The spectroscopic and elemental analyses revealed that 3 is a 1:l adduct of dimethylamine and the alkynylcarbene complex. However, the analyses were not consistent with those for a (P-aminoalkeny1)carbene complex or a 3-aminoallenylidene complex,2 which have been observed in the reaction of group 6 metal alkynyl(alkoxylcarbene complexes with amines. Compound 3 was recrystallized from hexane, and its molecular structure was established by X-ray crystallography (Figure 1): It has the structure of a n (y3-(P-acylvinyl)carbene)Fe(C0)3 ~ o m p l e x .The ~ structure is indicative of a CO insertion and a rearrangement involving the amino group and the carbonyl oxygen if rearrangement of the tert-butyl group is ruled out. (y3-(P-Acylvinyl)carbene)Fe(C0)3 complexes analogous to 3 and 4 have been suggested as common intermediates for furans and a-pyrone complexes in reactions of metal carbene complexes with alkyne^.^^,^,^ In addition, it is well-known that a Michael-type addition of amines (5) For previous examples of ($-P-acylvinylcarbene)Fe(C0)3 complexes, see: Mitsudo, T.; Watanabe, H.; Sasaki, T.; Takegami, Y.; Watanabe, Y.; Kafuku, K.; Nakatsu, K. Organometallics 1989,8, 368 and references therein.
0276-733319512314-4431$09.00/0 0 1995 American Chemical Society
Notes
4432 Organometallics, Vol. 14, No. 9, 1995
Scheme 1
111
'I'
HNMez CH&N
'Bu
HNMe2
Me2"
4
80 'C
2
I co
I
I
'Bu __c
1
co
25 'C EtO'
M e 2 N \ i b/ t B u X I H ?~(CO), 5: X=OEt 6: X=NMe2
3
Scheme 2
-
HNMe2 1 (or2)
7
L
to group 6 metal alkynylcarbene complexes is predominant over substitution at the carbene carbon above room t e m p e r a t ~ r e .Thus, ~ a reaction pathway can be presented for the isolated products 3-6 a s shown in Scheme 2: At first a ((P-aminovinyl)carbene)iron(O) complex (7) is formed by a Michael-type addition of dimethylamine to alkynylcarbene complexes 1 and 2. Then coordination of the vinyl group t o the iron and CO insertion at the carbene carbon give y4-vinylketene complex 8. Rearrangement of the dimethylamino unit and the ketenyl oxygen leads to ((P-acylvinyl)carbene)Fe(C0)3 complexes 3 and 4 through formation of a coordinated furan derivative (9) and ring opening of the furan with breaking the bond between oxygen and the carbon bearing the dimethylamino group. In the presence of CO, complexes 3 and 4 are obvious precursors of the pyrone complexes 5 and 6 which can be formed by CO insertion at the carbene carbon (to give 10)and subsequent ~ y c l i z a t i o n . ~ ~ ~ ~ ~ ~ ~ We have observed that two types of products can be obtained selectively both in almost quantitative yields from reactions of the iron(0) tert-butyl-substituted alkynyl(ethoxy)carbenecomplex l with dimethylamine with varying reaction temperature. Furthermore, the X-ray crystal structure of the addition product 3 has revealed that CO insertion and rearrangement of the dimethylamino group proceed at room temperature. (6) (a) McCallum J. S.; Kunng, F.-A.; Gilbertson, S. R.; Wulff, W. D. Organometallics 1988, 7, 2346. (b) Semmelhack, M. F.; Tamura, R.; Schnatter, W.; Springer, J. J.Am. Chem. SOC.1984, 106,5363. ( c ) Semmelhack, M. F.; Park, J. Organometallics 1986,5 , 2550.
8
10
J
Experimental Section General Comments. Solvents used for reactions were all reagent grade and were further purified by standard techniques. The alkynylcarbene complex 1 was prepared by the method described p r e v i o ~ s l y . ~ ~ All reactions and manipulations were carried out on a dual manifold providing vacuum and dry argon. For reactions involving CO pressure, a Schlenk tube equipped with highvacuum O-ring right-angle stopcock was used. Flash column chromatography was carried out with mixtures of degassed hexane and ethyl acetate as the eluents and silica gel (Merck: silica gel 60, 40-63 pm particle size) as the stationary phase. IR spectra were recorded on a Bomem Michelson 100 FTIR spectrometer using a matched NaCl solution cell of 0.5mm path length. lH and 13C NMR spectra were recorded on a Bruker ASPECT 300 spectrometer. Chemical shifts are reported in ppm downfield from TMS but were measured relative to the residual 'H in the solvent. Electron impact mass spectra were recorded on a Kratos 25-RAF. Melting points were measured on a Thomas Hoover capillary melting point apparatus and are uncorrected. High-resolution mass spectroscopy and elemental analyses were conducted by Korea Basic Science Center, Seoul, Korea. Reaction of (C0)4Fe=C(OEt)C=C-tBu(1) with Dimethylamine at -78 "C. Dimethylamine was injected to a solution of 1 (10.12mmol) in ether (30 mL) a t -78 "C through a cannula with the resulting solution being stirred for 2 min until the color of the solution changed from purple t o dark red. The reaction mixture was concentrated under vacuum, and the residue was chromatographed (4:l hexane/EtOAc) t o give 2.93 g (95%)of 2 as a dark red oil. High-resolution MS (EI) calcd for 2: m i z 305.0346, found, 305.0351. IR (CH2C12, cm-l): vcc 2194 (w), vco 2040 (s), 1950 (s), 1937 (s). lH NMR
Organometallics, Vol. 14, No. 9, 1995 4433
Notes
Table 1. Crystallographic Data for 3 formula fw space group
C15H21N05Fe 351.19 monoclinic,P21/c (No. 14) 8.834(2) 22.484(2) 9.380(2)
a, A
b, A c,
A
4 23 1.329 0.50 x 0.40 x 0.30 Mo Ka [A(Kal) = 0.710 73 A) 8.76
2'
temp, "C D (calcd),g cm-3 crystal dimens, mm3 radiation linear abs coeff, cm-I scan mode w-scan width, deg 20 limit, deg no. of data collcd no. of unique data no. of unique data with I no. of variables GOF R(FIa RW.(FIb
w
>
0.85 + 0.35 tan 0 48 2711 2579 3o(I) 1901 262 0.47 0.029 0.029
R = XIIF0 - lF~ll/lF~l. R, = [Zw(lFol - lFcl)2E~lFo~21"2; w= 4F02/02(F,,2);a(Fo2)= [u2(1) (p1)2]1'2, p = 0.04.
+
(C6D6, ppm): d 3.80 (s, 3 H, -NCH3), 3.53 ( s , 3 H, -NCH3), 1.31 (s, 9 H, -C(CH3)3). I3C NMR (CsD6, ppm): b 232.0 (Fe=C), 216.20 (CO),133.48 (-CEC-), 84.98 (-C&-), 47.84 (-NCH3), 45.96 (-NCH3), 29.87 (-CMe3), 29.49 (-C(CH&). MS (EI): m l z 305 (M+,2.0), 276 (5.0), 249 (611, 221 (861, 193 (100). Reaction of 1 with Dimethylamine at 25 "C. Dimethylamine was injected to a solution of l (6.08 mmol) in ether (30 mL) a t 25 "C through a cannula, with the resulting solution being stirred for 2 min. The color of the reaction mixture changed from purple to dark brown. The reaction mixture was concentrated under vacuum, and the residue was chromatographed (4:l hexane/EtOAc) to give 2.05 g (96%) of 3 as a yellow solid. It was recrystallized from hexane to prepare single crystals for X-ray diffraction analysis. Mp: 106-107 "C. Anal. Calcd for 3: C, 51.30; H, 6.03; N, 3.99. Found: C, 51.31; H, 6.00; N, 4.06. IR (CH2C12, cm-'1: Y C O 2033 (SI, 1956 (s), YC-0 1645 (s). 'H NMR ( C & 3 , ppm): b 4.29 ( s , 1 H, -C=C-H), 3.05 (m, 1 H, -0CH~CH3),2.90(m, 1H, -0CH2CH3),2.71 (br s, 3 H, -NCH3), 2.62 (br s, 3 H, -NCH3), 1.28 (s, 9 H, -C(CH3)3), 0.96 (dd, J = 6.87, 8.19 Hz, 3 H, -OCH2CH3). 13CNMR (C6D6,ppm): 6 226.04 (Fe=C), 213.62 (Fe-CO), 211.37 (-C=O), 107.0 (-C=C-H), 64.5 (-C=C-OCH2CH3), 49.4 (-C=C-OEt), 45.5 (-NCH3), 44.6 (-NCH3), 43.8 (-CMe3), 28.0 (-C(CH&), 14.6 (-0CH2CH3). MS (EI) m l z 351 (M+, l.O), 323 (24), 295 (451, 267 (100). Reaction of (C0)4Fe=C(NMe2)C=C-tBu (2) with Dimethylamine. Dimethylamine was injected to a solution of 2 (424 mg, 1.39 mmol) in acetonitrile (15 mL) at 25 "C through a cannula for 5 s. After being stirred for 3 h, the reaction mixture was concentrated under vacuum and the residue was chromatographed (4:l hexane/EtOAc) to give 442 mg (91%)of 4 as a yellow solid. Mp: 123-124 "C. Anal. Calcd for 4: C, 51.45; H, 6.33; N, 8.00. Found: C, 51.44; H, 6.25; N, 8.12. IR (CH2C12,cm-'1: Y C O 2020 ( s ) , 1943 (SI, vc-o 1641 (s). 'H NMR (C& ppm): d 4.02 (s, 1 H, -C=C-H), 2.66 (br s, 6 H, -N(CH3,2),1.72 (s, 6 H, -N(CH3d, 1.30 (s, 9 H, -C(CH3)3). 13C NMR (C6Ds,ppm): b 232.04 (Fe=C), 215.57 (Fe-CO), 211.33 (-C=O), 97.96 (-C=C-H), 49.46 (-NCH3), 44.41 (-NCH3), 43.48 (-NCH3), 39.98 (-CMe3), 28.23 (-C(CH&). MS (EI) m / z 350 (M+, 2.0), 322 (21), 294 (40), 266 (731, 251 (100). Reaction of 3 with CO. A Schlenk tube, containing a solution of 3 (260 mg, 0.74 mmol) in 1,2-dichloroethane (20 mL), was filled with CO gas (30 psi). After being stirred a t 25 "C for 4 days, the reaction mixture was concentrated under
Table 2. Positional Parameters and Be, Valuesa for Non-Hydrogen Atoms of 3 atom Fe 01 02 03 04 05 N
c1
c2 c3 c4 c5 C6 c7 C8 c9 c10
c11 c12 C13 C14 C15
Y
X
0.63135(5) 0.3832(3) 0.4377(3) 0.8339(3) 1.0153(2) 0.6140(2) 0.8115(3) 0.4780(4) 0.5117(4) 0.7529(4) 0.8230(4) 0.8901(4) 0.7493(3) 0.6997(3) 0.7431(3) 0.9083(3) 0.9464(4) 0.8021(4) 1.0837(4) 0.9956(5) 0.4983(4) 0.4183(4)
0.07610(2) 0.1248(1) -0.0204(1) 0.0101(1)
0.13373(9) 0.17432(9) 0.0519(1) 0.1053(2) 0.0181(2) 0.0365(1) -0.0129(1) 0.0841(2) 0.0798(1) 0.1394(1) 0.1612(1) 0.1562(1) 0.1828(1) 0.1827(2) 0.1483(2) 0.2474(2) 0.1455(2) 0.1909(2)
2
0.20391(5) -0.0666(3) 0.2569(3) 0.0681(3) 0.3532(2) 0.4388(2) 0.5380(3) 0.0382(4) 0.2333(4) 0.1173(4) 0.5465(4) 0.6784(4) 0.4101(3) 0.3727(3) 0.2506(3) 0.2480(3) 0.1129(3) -0.0341(4) 0.0886(4) 0.1554(4) 0.4913(4) 0.5571(4)
Be,, 3.664(9) 7.53(8) 7.11(7) 6.40(7) 4.62(5) 4.09(5) 3.53(5) 4.89(8) 4.79(8) 4.39(8) 4.87(8) 4.90(8) 3.44(6) 3.47(7) 3.58(7) 3.51(7) 4.10(7) 5.56(9) 7.0(1) 6.5(1) 5.33(8) 6.8(1)
Table 3. Selected Bond Lengths (A)and Angles (deg) for 3 Fe-C(l) Fe-C(2) Fe-C(3) Fe-C(6) Fe-C(7) Fe-C(8) O(l)-C(l) 0(2)-C(2) 0(3)-C(3)
Bond Lengths 1.807(3) 0(4)-C(9) 1.757(4) 0(5)-C(7) 1.787(4) N-C(4) 1.865(2) N-C(5) 2.063(3) N-C(6) 2.131(3) C(6)-C(7) 1.143(4) C(7)-C(8) 1.151(5) C(8)-C(9) 1.139(5) C(9)-C(lO)
1.222(3) 1.374(4) 1.461(4) 1.459(4) 1.301(3) 1.417(4) 1.412(5) 1.473(4) 1.538(5)
Bond Angles 95.1(1) C(5)-N-C(6) 100.5(2) Fe-C(l)-O(l) 150.6(2) Fe-C(2)-0(2) 110.5(1) Fe-C(3)-0(3) 90.6(1) Fe-C(6)-N 100.7(2) Fe-C(6)-C(7) 91.5(1) Fe-C(7)-0(5) Fe-C(7)-C(6) 115.3(1) 153.6(5) Fe-C(7)-C(8) 106.4(1) Fe-C(8)-C(7) Fe-C(8)-C(9) 128.9 (1) 103.6 (1) 0(4)-C(9)-C(8) 0(4)-C(9)-C(lO) 41.9 (1) 0(5)-C(7)-C(6) 71.8 (1) 39.3 (1) 0(5)-C(7)-C(8) 116.3 (2) N-C(6)-C(7) C(8)-C(9)-C(lO) 122.1 (2)
121.2(2) 178.6(3) 177.6(3) 177.0(3) 148.2(2) 76.5(2) 132.6(2) 61.5(1) 73.0(2) 67.7(2) 108.7 (2) 121.4 (3) 120.2 (3) 126.9 (3) 120.5 (2) 133.2 (3) 118.4 (2)
vacuum and the residue was chromatographed (2:1 hexane/ EtOAc) to give 216 mg (77%)of 5 as a yellow solid. Mp 107109 "C. Anal. Calcd for 5: C, 50.68; H, 5.58; N, 3.69. Found: C, 50.64; H, 5.68; N, 3.74. IR (CH2C12, cm-'1: Y C O 2060 (SI, 1994 (SI, YC-0 1716 (m). 'H NMR (CsD6, ppm): 6 5.30 ( s , 1 H, -C-C-H), 3.26 (m, 2 H, -OCHzCH3), 2.56 ( s , 6 H, -N(CH3)2), 1.27 (s, 9 H, -C(CH3)3), 0.95 (dd, J = 6.84, 6.84 Hz, 3 H, -0CHzCH3). NMR (C&, ppm): d 209.1 (Fe-CO), 124.7, 74.2, 70.5, 64.3 (-OCH2CH3), 42.2 (-N(CH3)2), 34.4 (-CMe3), 30.4 (-C(CH&), 14.3 (-0CHzCH3). MS (EI) m / z 379 (MA, 3.0), 351 (171, 323 (631, 295 (871, 267 (100). Reaction of 4 with CO. A Schlenk tube, containing a solution of 4 (110 mg, 0.291 mmol) in 1,2-dichloroethane (6 mL), was filled with CO gas (30 psi). After being stirred a t 80 "C for 19 h, the reaction mixture was concentrated under vacuum and the residue was chromatographed (1:1 hexane/ EtOAc) to give 96 mg (87%) of 6 as a yellow solid. Mp 125-
Notes
4434 Organometallics, Val. 14, No. 9, 1995 127 "C. Anal. Calcd for 6: C, 50.81; H, 5.86; N, 7.41. Found: C, 50.70; H, 6.12; N, 7.28. IR (CH2C12, cm-'): vco 2023 (s), 1945 (s), VC-0 1730 (m). 'H NMR (C&, ppm): d 4.79 (s, 1 H, -C=C-H), 3.12 (s, 3 H, -N(CHs)z), 2.66 ( 8 , 6 H, -N(CHdz), 2.21 (6, 3 H, -N(CH3)2), 1.23 (s,9 H, -C(CH3)3), 0.95 (dd, J = 6.84, 6.84 Hz, 3 H, -0CHzCH3). 13C NMR (CsD6, ppm): d 215.4 (Fe-CO), 168.4 (-C=O), 162.6 (-0-C-C-1, 80.2 (-C=C-NMe2), 67.8 (-C=C-NMeZ), 64.6 (-C-C-H), 50.2 (-NCH3), 48.5 (-NCH3), 37.3 (-NCH3), 30.7 (-CMe3), 28.5 (-C(CH3)3). MS (EI): m l z 378 (Mt, 39), 322 (711, 294 (711, 266 (831, 238 (83),210 (511, 195 (100). X-ray Crystallography. A crystal of 3 (0.5 x 0.4 x 0.3 "3) sealed in a Lindemann capillary tube was mounted on an Enraf-Nonius CAD4 diffractometer using Mo Ka radiation. Cell parameters and a n orientation matrix for data collection were obtained from least-squares refinement, using the setting angles of 25 reflections in the range 23.7 < 28 < 29.9". The crystallographic data and additional details of data collection are summarized in Table 1. The intensities of three standard reflections, recorded every 3 h of X-ray exposure, showed no systematic changes. All the calculations were carried out with the Enraf-Nonius MolEN package. The intensity data were corrected for Lorentz and polarization effects. Empirical absorption corrections were also applied (DIFABS). The structure was solved by a combination of Patterson and difference Fourier methods (SHELXS86).' All the nonhydrogen atoms were refined anisotropically by full-matrix leastsquares methods. The positions of hydrogen atoms were identified on a n electron density map. Each hydrogen atom (7) Sheldrick, G. M. SHEWZS-86 User Guide; Crystallography Department, University of Gottingen: mttingen, Germany, 1986.
was assigned a n isotropic thermal parameter of 1.2 times that of attached atom. All the calculations except solving structures were carried out with the Enraf-Nonius MolEN program package.8 The final cycle of refinement led to the R indices listed in Table 1. The atomic scattering factors were taken from ref 9 for the non-hydrogen atoms and from the ref 10 for hydrogen. The positional and equivalent isotropic thermal parameters of the non-hydrogen atoms are listed in Table 2, and selected bond lengths and bond angles for 3 are listed in Table 3.
Acknowledgment. We are grateful to the Ministry of Education (Basic Science Research Institute Program) and the Korea Science and Engineering Foundation (CBM Center) for financial support. We thank D. M. Whang and Prof. Kimoon Kim for the crystallographic analysis. Supporting Information Available: Tables of positional parameters for hydrogen atoms, anisotropic temperature factors, bond lengths, and bond angles for 3 (3 pages). Ordering information is given on any current masthead page. OM950321X (8) Fair, C. K. MolEN, Enraf-Nonius: 2624 BD Delft, The Netherlands, 1990. (9) Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystallography; Kynoch Press: Birmingham, England, 1974;Vol. IV. (10)Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J . Chem. Phys. 1966,42, 3175.
