J. Am. Chem. SOC.1989, 1 1 1 , 8383-8391
8383
Transient Generation of the Reactive Carbene Complex [ Cp(C0)2W=CH(Tol)]+ and Its Reactions with Alkynes To Form Vinylcarbene, Allyl, Naphthol, Diene, and Metallafuran Complexes Kevin E. Garrett,? John B. Sheridan,t Daniel B. Pourreau,? Wu Chang Feng,t Gregory L. Geoffroy,*.t Donna L. Staley,l and Arnold L. Rheingold' Contribution from the Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, and Department of Chemistry, The University of Delaware, Newark, Delaware 19716. Received April 20, 1989
Abstract: Although Cp(C0)2W=CTol, 9, does not itself react with alkynes, protonation of -78 OC solutions of the complex with HBF4 generates the transient carbene complex [Cp(C0)2W=CH(Tol)]+ which readily incorporates alkyne. Protonation of 9 in the presence of P h C s P h gives the vinylcarbene complex [Cp(CO)2W=C(Ph)C(Ph)=€H(Tol)]BF4, 14, which results from insertion of the alkyne into the tungsten-arbene bond. Vinylcarbene complex 14 readily undergoes substitution of iodide for CO to give the neutral vinylcarbene complex Cp(CO)(I)W=C(Ph)C(Ph)=CH(Tol), 15, which has been crystallographically characterized. The vinylcarbene ligand is coordinated to tungsten via the three carbon atoms (W-C = 1.999 (7), 2.305 (8), 2.293 (8) A) with a 130.4' bend in the C-C-C linkage. The geometrical parameters indicate an sp2 hybridization for each of the three carbons, but the substituents on this ligand are rotated such that a-bonding between the carbons is far from optimal. Vinylcarbene complex 14 also reacts with [BH4]- and P(Bu"), to form the allyl complexes C~(CO),W(T$P~CHC(P~)CH(TO~)} and [Cp(CO)2W{q3-(Bu"3P)(Ph)CC(Ph)CH(Tol)}]BF4, respectively. Complex 14 also reacts with the nitrone PhCH=N(O)Me to form the metallafuran complex Cp(CO),W(OC(Ph)C(Ph)C(Tol)), 19. This species results from oxygen-atom transfer from the nitrone to the carbene carbon of 14, deprotonation of the vinyl group, and ring closure. The metallafuran complex 19 has been crystallographically characterized. It possesses a planar metallafuran ring with bond distances within the ring implying delocalized bonding. Protonation of Cp(C0)2W=CTol in the presence of MeCECMe and CO gives high yield formation 20, which possesses a coordinated naphthol ligand. The latter can be released from the metal of [Cp(C0)2W(C13H,40}]BF4, by air oxidation, and the naphthol ligand undergoes deprotonation to form the allyl complex Cp(C0)2W(C13H130J. Reaction of the carbyne complex Cp(CO),W~C(2,6-Me2C6H3! with HBF4 in the presence of MeC=CMe led to the formation of 25, which possesses a coordinated diene ligand assembled by a benzannulation reaction from the [Cp(C0)2W(C14H1602)]+r carbyne, alkyne, and a CO ligand. The relevance of these various reactions to the general mechanism of naphthol formation from metal carbenes and alkynes is discussed.
Introduction Transition-metal carbene complexes have found numerous applications in organic and one especially important class of reactions is one that occurs between carbene complexes and a l k y n e ~ . ~ JThese reactions give a variety of products, depending upon the metal involved, its ligand set, the carbene substituents, and the nature of the alkyne employed. A typical set of organic products isolated after oxidative workup of such a reaction with (CO)5Cr=C(OMe)Ph is shown in eq 1.2c (COj5Cr=C/ O
+RC=CR
BOT
heptane
wl
Scheme I ,OMc
(C0)sCr C :,
+RCdX
+coPh
OH
+
\
\
R
O?de
OMe R
(1)
R
+
Ph
Even though the synthetic applications of these types of reactions are now well-established, the mechanism(s) by which they occur have never been fully elu~idated.~J" For the formation of naphthols from metal carbenes and alkynes, the mechanisms shown in Schemes I and I1 have been invoked, although there is no general agreement as to which specific path is f~llowed.~" An early step common to each proposed path is the formation of the metallacyclobutene complex 1. This species can ring open to yield the vinylcarbene complex 2 which would give the vinylketene complex 3 upon CO insertion. Electrocyclic ring closure to give 4 followed by a 1,3-hydrogen migration would yield complex 5, 'The Pennsylvania State University. *The University of Delaware.
0002-786318911511-8383$01SO10
Scheme I1
the precursor to the free naphthol. Alternatively, as shown in Scheme I, metalation of the arene ring can occur from the vi(1) Collman, J. P.; Hegedus, L. s.;Norton, J. R.; Finke, R. G.Principles and Applications of Orgonotransition Metal Chemistry; University Science Books: Mill Valley, CA, 1987; Chapter 16. (2) (a) Dotz, K. H. In Reactions of Coordinated Ligands; Braterman, P. S . , Ed.; Plenum: New York, NY, 1986; Chapter 4. (b) Dotz, K. H. In Transition Metal Carbene Complexes; Verlag Chemie: Deerfield Beach, FL, 1983; pp 191-226. ( c ) Dotz, K. H. Angew. Chem., Int. Ed. Engl. 1975, 14, 644. (d) Dotz, K . H. Pure Appl. Chem. 1983, 55, 1689.
0 1989 American Chemical Society
8384 J . Am. Chem. Soc., Vol. 1 1 1 , No. 22, 1989 nylcarbene complex 2 to form the metallacycle 6. This species would then yield 7 upon carbonylation, and reductive elimination from 7 would give intermediate 4 and from that 5. A third suggested mechanism is shown in Scheme I1 and involves insertion of C O into the metallacyclobutene 1 to form a metallacyclopentenone 8 which could rearrange to give vinylketene complex 3 and from that 4 and 5.2,3a Although a metallacyclobutene complex has generally been proposed as a common intermediate in the mechanisms of Schemes I and 11, there is no direct evidence for its involvement. Indeed, the results described herein indicate that the reaction may well proceed directly from the carbene to the vinylcarbene stage without the intermediacy of a metallacyclobutene complex. It has proven difficult to completely validate the mechanistic suggestions of Scheme I since the rate-limiting step typically involves ligand loss to open a coordination site for the alkyne to bind. Once bound, rapid ring closure occurs to give the observed products. No single reaction has been followed completely through the individual steps illustrated in Schemes I and 11, although there are now several examples of the addition of alkynes to carbenes to form vinyl~arbenes~3~and the carbonylation of vinylcarbenes to yield v i n y l k e t e n e ~ . ~ ~However, ~ ~ ~ * ~ to ~ ~our knowledge the conversion of a well-characterized vinylcarbene or vinylketene complex into a naphthol or indene product has never been achieved. One approach to investigating these mechanisms in more detail is to generate a coordinatively unsaturated carbene complex at a temperature sufficiently low to retard subsequent reactions so that they can be studied in detail. This can be achieved to some degree by opening a coordination site for the alkyne to bind through photoinduced ligand loss at low temperature as illustrated in our earlier study of the photosubstitution chemistry of (CO)5W=C(OMe)Ph.7 Irradiation of this complex in the presence of excess diphenylacetylene at -40 O C gave C O loss and ~
~
~~
~~
Garrett et al. formation of a carbene-alkyne complex that was isolated and was spectroscopically characterized.' Upon warmup to room temperature, this species rapidly underwent ring closure to yield an indenyl ether, but no intermediates could be detected in this conversion. Another approach to generating coordinatively unsaturated carbene complexes is through the addition of electrophiles to nucleophilic carbyne ligands.8-'0 This is well illustrated by the work of Stone and co-workers summarized in eq 2.8 Protonation of Cp(CO),W=LTol, 9, at -50 OC was proposed to give transient formation of the reactive carbene complex [Cp(CO)2W=C(H)Tol]+, 10. Although this species was not detected, its intermediacy was inferred from the formation of 12 by the presumed mechanism of eq 2 and by the formation of Cp(CO)2(I)W=C(H)Tol when the protonation was conducted in the presence of iodide.s Also, protonation of Cp(CO),W=Tol with HCI instead of HBF4 was shown by Kreissl and co-workers to result in double proton addition to the carbyne carbon to form an alkyl ligand that subsequently yields the $-acyl complex 13 upon C O insertion, eq 3.9
~~~~
(3) For lead references see: (a) McCallum, J. S.; Kunng, F. A,; Gilbertson, S. R.; Wulff, W. D. Organometallics 1988, 7, 2346. (b) Tang, P.-C.; Wulff, W. D. J . Am. Chem. SOC.1984, 106, 1132. (c) Wulff, W. D.; Yang, D. C. J . Am. Chem. SOC.1984, 106, 7565. (d) Wulff, W. D.; Gilbertson, S . R.; Springer, J. P. J . Am. Chem. SOC.1986, 108, 520. (e) Wulff, W. D.; Xu, Y.-C. J . Am. Chem. SOC.1988, 110, 2312. (f) Wulff, W. D.; Tang, P.-C.; McCallum, J. S. J . Am. Chem. Soc. 1981,103,7677. (g) Wulff, W. D.; Tang, P.-C. J . Am. Chem. SOC.1984,106,434. (h) Semmelhack, M. F.; Park, J. Organometallics 1986, 5, 2550. (i) Semmelhack, M. F.; Ho, S.; Steigerwald, M.; Lee, M. C. J . Am. Chem. SOC.1987,109,4397. Semmelhack, M. F.; Bozell, J. J.; Sato, T.; Wulff, W.; Spiess, E.; a s k , A. J. Am. Chem. SOC.1982, 104, 5850. (4) (a) Templeton, J. L.; Herrick, R. S.; Rusik, C . A,; McKenna, C. E.; McDonald, J. W.; Newton, W. E. Inorg. Chem. 1985,24, 1383. (b) Newton, M. G.; Pantaleo, N. S.; King, R. B.; Chu, C.-K. J . Chem. SOC.,Chem. Commun. 1979, 10. (c) Binger, P.; Cetinkaya, B.; Kriiger, C. J . Organomet. Chem. 1978,159,63. (d) Dettlaf, G.; Behrens, U.; Weiss, E. Chem. Ber. 1978, 111, 3019. (e) Mitsudo, T.-A.; Sasaki, T.; Watanabe, Y.;Takegami, Y.; Nishigaki, S . ; Nakatsu, K. J . Chem. SOC.,Chem. Commun. 1978, 252. (5) (a) Mayr, A.; Asaro, M. F.; Glines, T. J. J . Am. Chem. Soc. 1987,109, 2215. (b) Dotz, K. H.; Kreiter, C. G. J . Organomet. Chem. 1975, 99, 309. (c) Aumann, R.; Heinen, H. Chem. Ber. 1987, 120, 537. (d) Fischer, H.; Dotz, K. H. Chem. Ber. 1980, 113, 193. (e) Wood, C. D.; McLain, S. J.; Schrock, R. R. J . Am. Chem. SOC.1979, 101, 3210. (f) Casey, C. P.; Polichnowski, S. W.; Shusterman, A. J.; Jones, C. R. J . Am. Chem. SOC.1979, 101,7282. (g) Wilson, J. W.; Fischer, E. 0. J . Organomet. Chem. 1973.57, C63. (h) Kuo, G. H.; Helquist, P.; Kerber, R. C. Organometallics 1984, 3, 806. (i) Casey, C. P.; Miles, W. H. Organometallics 1984, 3, 808. 6)
u)
Nakatsu, K.; Mitsudo, T.-A,; Nakanishi, H.; Watanabe, Y.; Takegami, Y. Chem. Lett. 1977, 1447. (k) Mitsudo, T.-A.; Watanabe, Y.; Nakanishi, N.; Morishima, I.; Inubushi, T.; Takegami, Y. J. Chem. Soc., Dalton Trans. 1978, 1298. (I) Casey, C. P.; Brunsvold, W. R. Inorg. Chem. 1977, 16, 391. (m) Dotz, K. H. Chem. Ber. 1977, 110, 78. (n) Casey, C. P.; Boggs, R. A,; Anderson, R. L. J. Am. Chem. Soc. 1972.94.8947. ( 0 ) Rudler-Chauvin, M.; Rudler, H. J . Organomet. Chem. 1981, 212, 203. (p) Dotz, K. H.; Pruskil, I. J . Organomet. Chem. 1977, 132, 115. (9)Casey, C. P.; Miles, W. H.; Tukada, H. J . Am. Chem. SOC.1985, 107, 2924. (6) (a) Mitsudo, T.; Ishihara, A.; Kadokura, M.; Watanabe, Y. Organometallics 1986, 5, 238. (b) Casey, C. P.; OConnor, J. M. J . Am. Chem. SOC. 1983, 105, 2919. (c) Casey, C. P.; O'Connor, J. M.; Haller, K. J. J . Am. Chem.Soc. 1985,107,3172. (d) Dotz. K. H. Angew. Chem., Int. Ed. Engl. 1979, 18, 954. (e) Klimes, J.; Weiss, E. Angew. Chem., Int. Ed. Engl. 1982, 21, 205. (0 Herrmann, W. A.; Plank, J.; Kriechbaum, G . W.; Ziegler, M. L.; Pfisterer, H.; Atwood, J. L.; Rogers, R. D. J . Organomet. Chem. 1984, 264, 327. (g) DBtz, K. H.; Fiigen-Koster, B. Chem. Ber. 1980, 113, 1449. (7) Foley, H. C.; Strubinger, L. M.; Targos, T. S . ; Geoffroy, G. L. J . Am. Chem. SOC.1983, 105, 3064.
Protonation of these carbyne complexes in the presence of alkynes has never been reported, although the isolobal analogy between carbyne complex 9 and alkynes and the apparent intermediacy of 11 in reaction 2 suggests this to be a promising reaction. We have accordingly examined the reactivity of carbyne complex 9 with HBF4 in the presence of alkynes, and those reactions are described herein. As expected, the chemistry is markedly sensitive to the alkyne employed and to the carbene substituents. Protonation of 9 in the presence of MeC=CMe results in formation of a naphthol complex analogous to 5 in Scheme I. By varying the carbene and alkyne substituents, vinylcarbene and diene complexes analogous to intermediates 2 and 4 have been isolated and crystallographically defined. New transformations of vinylcarbene complexes are also described, including their reactions with nucleophiles to form allyl and metallafuran derivatives.
Results Protonation of Cp(CO),W=CToI, 9, in the Presence of P h m P h . Addition of HBF, to a solution of 9 in the presence of P h C E C P h was found to give rapid formation of the q3vinylcarbene complex 14, eq 4. For simplicity, complex 14 is drawn in eq 4 with a metal-carbene double bond and with a (8) (a) Howard, J. A. K.; Jeffery, J. C.; Laurie, J. C. V.; Moore, I.; Stone, F. G. A.; Stringer, A. Inorg. Chim. Acta 1985, 100, 23. (b) Jeffery, J. C.; Laurie, J. C. V.; Moore, I.; Stone, F. G. A. J . Organomet. Chem. 1983, 258, c37. (9) (a) Kreissl, F. R.; Sieber, W. J.; Keller, H.; Riede, J.; Wolfgruber, M. J . Organomet. Chem. 1987, 320, 83. (b) Kreissl, F. R.; Sieber, W. J.; Wolfgruber, M.; Riede, J. Angew. Chem., Int. Ed. Engl. 1984, 23, 640.
(10) For other examples of carbyne protonation reactions see: (a) Green, M.; Orpen, A. G.; Williams, I. D. J . Chem. Soc., Chem. Commun. 1982,493. (b) Holmes, S. J.; Schrock, R. R. J . Am. Chem. SOC.1981, 103,4599. (c) Clark, G. R.; Marsden, K.; Roper, W. R.; Wright, L. J. J . Am. Chem. SOC. 1980, 102, 6570. (d) Kreissl, F. R.; Sieber, W. J.; Wolfgruber, M. J . Organomet. Chem. 1984, 270, C45.
Transient Generation of [Cp(C0J2W=CH( Tol)]'
J . Am. Chem. SOC.,Vol. 111, No. 22, 1989 8385 -+
CP
\
, I OC
ECTol
c 0
+ HBF, + P h G C P h
Table I. Crystallographic Data for
Cp(CO)(I)W(=C(Ph)(Ph)C=CHTol),15, and Cp(CO)2W [OC(Ph)C(Ph)C(Tol)],19"
%
15 9
0
Ill
formula crystal system space group a, A b, A c.
A
8, deg
v.A3
*-coordinated vinyl group, although the crystal structure of the derivative 15 discussed below indicates that the alternative drawing given in the equation is more accurate. Complex 14 was isolated in high yield as a thermally sensitive red solid and has been spectroscopically characterized. It has been further defined by its conversion to the crystallographically characterized vinylcarbene complex Cp(CO)( I) W=C( Ph)(Ph)C=CHTol, 15, described below. Two v(C0) bands at 2054 and 1975 cm-' are present in the IR spectrum of 14, indicating a dicarbonyl formulation, and its IH N M R spectrum shows characteristic C p and vinyl proton resonances a t 6 6.40 and 6.05, respectively. The l3C(IH]N M R spectrum of 14 shows a resonance at 6 269.3 ppm attributed to the carbene carbon and two resonances at 6 98.2 and 60.8 due to the vinyl carbons as well as C p (6 95.2) and aryl resonances. The 6 98.2 resonance splits into a doublet (JCH= 184.6 Hz) upon recording the proton-coupled I3C N M R spectrum, indicating its assignment to the terminal vinyl carbon bearing the hydrogen atom. The downfield 6 269.3 ppm resonance of 14 is in the region typical of metal carbenes and strongly indicates the q3-vinylcarbene formulation drawn in eq 4 rather than a metallacyclobutene structure. Iodide for CO Substitution in Vinylcarbene Complex 14. The vinylcarbene complex 14 rapidly undergoes substitution of CO by added iodide to give the neutral vinylcarbene complex 15, eq 5. This complex was isolated as a yellow solid and has been
L? T
19
(a) Crystal Parameters
Ph l 4 ( 8 9 W )
Z
D(calcd) p(Mo K a ) , cm-I temp, K
C28H2301W*i/2CH2C12 C29H2203.W monoclinic monoclinic 12/a 16.383 (5) 15.609 (5) 20.935 (6) 101.39 (2) 5248 (3) 8 1.84 59.3s 296
P2dn
12.130 (2)
color
brown
size, mm
0.52 X 0.28 1.63
T m a J Tmin
diffractometer radiation
wavelength, A scan method scan limits, deg octants collected rflns collected indpdt rflns obs rflns
R (merge) std rflns var in stds. %
X
0.21
14.455 (3) 13.572 (3) 97.28 (2) 2360.5 (8) 4 1.695 52.0 295 deep red 0.27 X 0.29 X 0.31
2.47
(b) Data Collection Nicolet R3m Mo Ka 0.71073 Wyckoff 4 I20 I50 4528555 =kh,+k,+l *h,+k,+l 4943 5881 4618 5429 3340 (SuF,) 4047 (5aFJ 0.032 0.023 3 std/97 rflns 3 std/97 rflns
