5127
Organometallics 1996, 14, 5127-5137
Synthesis of a New Family of Metallafurans from (0xapentadienyl)metalPrecursors John R. Bleeke,* Pamela R. New, Jonathan M. B. Blanchard, Tesfamichael Haile, and Alicia M. Beatty Department of Chemistry, Washington University, St. Louis, Missouri 63130-4899 Received June 26, 1995@ Treatment of ((1,2,5-v)-4-methyl-5-oxapentadienyl)Ir(PMe3)3 (1)with HBF4aOEtz leads to protonation a t carbon C3 and production of [(( 1,2,5-v)-4-methyl-5-oxapenta-1,4-diene)Ir(PMe3)31+BF4-(4). At room temperature, this species rearranges to the iridafuran complex
-
,...............,
[~~C-CH~CUCHUC(CH~)LIO"I~(PM~~)~(H)]+BF~(6). Similar treatment of the five-membered iridacycle, mer-CHz=CCH=C(CH3)0Ir(PMe3)3(H) (3)with HBF40OEt2 results in direct
...............
electrophilic attack at carbon C1 and production of the mer isomer of 5, [mer-
CH~~UCHUC(CH~)LIOUII.(PM~~)~(H)I+BF~(6). In the tris(PEt3) reaction system, treatment of the six-membered ring compound, mer-dH=CHCH--C(CH3)OIkPEt3)3(H) (7), with I HBF4-OEtz leads to protonation at C3 and production of [mer-&H=CHCHzC(CH3)=OIr-
-
...............
(PEt3)3(H)l+BF4-(9). Upon heating in tetrahydrofuran at reflux, this species rearranges to I
I
the iridafuran complex, [~~~-CH~CUCHUC(CH~)LIOUI~(PE~~)~(H)I+BF~(10).Protonation
of the five-membered-ring compound, mer-CHz=CCH=C(CH3)0Ir(PEt3)3(H) (8),with HBF4. OEtz also produces iridafuran 10 via direct electrophilic addition to C1. Excess IZ reacts with compound 10 exclusively a t the metal center to produce the neutral diiodide compound,
...............
~~U~S-CH~~-CH~C(CHJ)LIOUI:(PE~~)Z(I)Z (1l),while excess Brz reacts with 10 a t both the iridium center and C3 of the ring to form the electrophilic aromatic substitution
................ ............... CH3d"CH"C(CH3)LIO"I:(PEt3)3(H)]+PF6...............
product,
~~u~s-CH~~"C(B~)LIC(CH~)LIOUII.(PE~~)Z(B~)Z (12). Molecular structures of [mer(the
salt of lo), ................
PF6-
trans-CH3I
~.'CH'C(CH~)LIO'I~(PE~~)Z(I)Z(111, and ~ ~ U ~ S - C H ~ ~ " C ( B ~ ) L L C ( C H ~ ) L I O Y I ~ ( P E ~ ~ ) Z ( B ~ ) Z (12)have been determined by single-crystal X-ray diffraction studies. Introduction
During the past several years, we have been developing a new synthetic route to unsaturated metallacycles, which utilizes pentadienide and heteropentadienide reagents as the source of ring carbons or heteroatoms and exploits C-H bond activation in the key ringforming step. By using this approach, we have synthesized metallacyclohexadiene complexes' and a variety of unsaturated five- and six-membered thia-2 and oxametal la cycle^.^ Several of these species have been Abstract published in Advance ACS Abstracts, October 15,1995. (1)(a) Bleeke, J. R.; Peng, W.-J. Organometallics 1987,6,1576.(b) Bleeke, J . R.; Peng, W.-J.; Xie, Y.-F.; Chiang, M. Y. Organometallics 1990, 9, 1113. (c) Bleeke, J. R.; Rohde, A. M.; Boorsma, D. W. Organometallics 1993,12, 970. (2)(a) Bleeke, J. R.; Ortwerth, M. F.; Chiang, M. Y. Organometallics 1992, 11, 2740. (b) Bleeke, J. R.; Ortwerth, M. F.; Rohde, A. M. Organometallics 1995,14, 2813. (3)(a)Bleeke, J . R.; Haile, T.; Chiang, M. Y. Organometallics 1991, 10, 19. (b) Bleeke, J. R.; Haile, T.; New, P. R.; Chiang, M. Y. Organometallics 1993,12, 517. (4)(a) Bleeke, J . R.; Xie, Y.-F.; Peng, W.-J.; Chiang, M. Y. J.Am. Chem. SOC.1989,111, 4118. (b) Bleeke, J. R. Acc. Chem. Res. 1991, 24, 271.
subsequently converted to aromatic metallacycles, particularly metal la benzene^^ and metallathi~phenes.~ We now report the synthesis of a family of metallafurans.6 These species are generated either by direct protonation of (oxapentadieny1)metalcomplexes or by protonation of the oxametallacyclesproduced from these complexes via C-H bond activation. X-ray crystal structures, NMR spectra, and chemical reactivity studies of the metallafurans fully support the characterization of these species as aromatic metallacycles. In these novel compounds, metal d orbitals participate with carbon and oxygen p orbitals in forming the n bonds of the aromatic rings.
@
Results and Discussion
A. Reaction of (Cl)Ir(PMes)s with Potassium 4Methyl-Ssxapentadienide. As we reported treatment of (Cl)Ir(PMe3)3with potassium 4-methyl-5oxapentadienide produces ((1,2,5-~)-4-methy1-5-oxapen( 5 ) (a) Bleeke, J. R.; Ortwerth, M. F.; Chiang, M. Y. Organometallics 1993, 12, 985. (b) Bleeke, J. R.; Ortwerth, M. F.; Rohde, A. M. Organometallics 1995,14, 2813.
0276-733319512314-5127$09.00/0 0 1995 American Chemical Society
Bleeke et al.
5128 Organometallics, Vol. 14, No. 11, 1995 Scheme 1
Ci
1 tadienyl)Ir(PMe& (1)(see Scheme 1). Compound 1 can be isolated and fully characterized, but upon stirring at room temperature in tetrahydrofuran, it slowly (over several days) equilibrates with the five-membered-ring compound,fac-CHz=(!!CH=C(CH3)0IkPMe3)3(H) (2) (see Scheme 2). The metallacycle is produced via intramolecular activation of C-H2 in 16e intermediate B (Scheme 2) or the corresponding 18e agostic specie^.^ This mixture then euen more slowly (over several weeks at room temperature) converts to the thermodynamically preferred meridional isomer of the five-membered (6) A sizable number of compounds containing the metallafuran structure have been reported, although the extent to which these species exhibit aromatic character varies widely. The largest classes of metallafurans are metal-carbonyl complexes of the group VI and VI1 metals. Key references include the following: (a) Green, M.; Nyathi, J. Z.; Scott, C.; Stone, F. G. A.; Welch, A. J.; Woodward, P. J. Chem. SOC.,Dalton Trans. 1978, 1067. (b) Allen, S. R.; Green, M.; Norman, N. C.; Paddick, K. E.; Orpen, A. G. J. Chem. Soc., Dalton Trans. 1983, 1625. (c) Watson, P. L.; Bergman, R. G. J. Am. Chem. SOC.1979, 101, 2055. (d) Alt, H. G. J. Organomet. Chem. 1985,288, 149. (e) Alt, H. G.; Herrmann, G. S.; Engelhardt, H. E.; Rogers, R. D. J. Orgunomet. Chem. 1987,331, 329. (0 Burkhardt, E. R.; Doney, J. J.; Bergman, R. G.; Heathcock, C. H. J. Am. Chem. SOC.1987, 109, 2022. (g) Chaona, S.; Lalor, F. J.; Ferguson, G.; Hunt, M. M. J. Chem. SOC.,Chem. Commun. 1988, 1606. (h) Rusik, C. A.; Collins, M. A.; Gamble, A. S.; Tonker, T. L.; Templeton, J. L. J.Am. Chem. Soc. 1989, 111, 2550. (i) Garrett, K. E.; Sheridan, J. B.; Pourreau, D. B.; Feng, W. C.; Geoffroy, G. L.; Staley, D. L.; Rheingold, A. L. J. Am. Chem. SOC.1989,111,8383. (i) Van der Zeijden, A. A. H.; Bosch, H. W.; Berke, H. Organometallics 1992, 11, 563. (k) Carter, J. D.; Schoch, T. It; McElwee-White, L. Organometallics 1992, 11, 3571. (1) Masters, A. P.; Parvez, M.; Sorensen, T. S.; Sun, F. Can. J. Chem. 1993, 71, 230. (m) Booth, B. L.; Hargreaves, R. G. J. Chem. SOC.A 1970, 308. (n) Herrmann, W. A,; Ziegler, M. L.; Serhadli, 0. Organometallics 1983, 2,958. (0)DeShong, P.; Sidler, D. R.; Rybczynski, P. J.; Slough, G. A.; Rheingold, A. L. J.Am. Chem. SOC.1988,110,2575. (p) DeShong, P.; Slough, G. A.; Sidler, D. R.; Rybczynski, P. J.; von Philipsborn, W.; Kunz, R. W.; Bursten, B. E.; Clayton, T. W., Jr. Organometallics 1989, 8, 1381. (q) Stack, J. G.; Simpson, R. D.; Hollander, F. J.; Bergman, R. G.; Heathcock, C. H. J. Am. Chem. SOC.1990, 112, 2716. (r) OConnor, J. M.; Uhrhammer, R.; Rheingold, A. L.; Roddick, D. M. J. Am. Chem. SOC.1991, 113, 4530. (s) Adams, R. D.; Chen, G.; Chen, L.; Wu, W.; Yin, J. J.Am. Chem. SOC.1991,113, 9406. (t)Adams, R. D.; Chen, L.; Wu, W. Organometallics 1992,11, 3505. (u)Padolik, L. L.; Gallucci, J. C.; Wojcicki, A. J. Am. Chem. SOC.1993, 115, 9986. A substantial number of Group VI11 metallafurans have also been reported. Key references include the following: (v) Komiya, S.; Ito, T.; Cowie, M.; Yamamoto, A.; Ibers, J . A. J. Am. Chem. Soc. 1976,98, 3874. (w) Deeming, A. J.;Manning, P. J.;Rothwell, I. P.; Hursthouse, M. B.; Walker, N. P. C. J. Chem. Soc., Dalton Trans. 1984, 2039. (x) Werner, H.; Weinand, R.; Otto, H. J. Organomet. Chem. 1986, 307, 49. (y) Romero, A.; Vegas, A.; Dixneuf, P. H. Angew. Chem., Int. Ed. Engl. 1990,29, 215. ( 2 ) Akita, M.; Terada, M.; Oyama, S.; Sugimoto, S.; Moro-oka, Y. Organometallics 1991, 10, 1561. (aa) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Valero, C. Organometallics 1993, 12, 663. (bb) Werner, H.; Dirnberger, T.; Schulz, M. Angew. Chem., Int. Ed. Engl. 1988,27, 948. (cc) Sunley, G. J.; Menanteau, P. C.; Adams, H.; Bailey, N. A.; Maitlis, P. M. J . Chem. Soc., Dalton Trans. 1989,2415. (dd)Bianchini, C.; Innocenti, P.; Masi, D.; Meli, A,; Sabat, M. Organometallics 1986,5, 72. (eel Carmona, E.; Gutierrez-Puebla, E.; Monge, A.; Marin, J. M.; Paneque, M.; Poveda, M. L. Organometallics 1989, 8 , 967. (ff) Allevi, C.; Garlaschelli, L.; Malatesta, M. C.; Ganazzoli, 'F. Organometallics 1990, 9, 1383. One example of a metallafuran in which the oxygen atom resides beta to the metal center has been reported. See (gg) Shih, K.-Y.; Fanwick, P. E.; Walton, R. A. J. Am. Chem. SOC.1993, 115, 9319. (7) A small quantity of the six-membered-ring compound merdH=CHCH=C(CH,)OI:(PMe&(H), produced via C-H1 bond activation, is also observed in the equilibrium mixture.
metallacycle, ~~-CHZ=CH=C(CH~)OI~PM~~)~(H) (3h8 Upon heating, this conversion occurs much more rapidly and is essentially complete in 20 h in refluxing tetrahydrofuran. B. Protonation of Compounds 1 and 3. Treatment of compound 1 with HBF4-OEtz in diethyl ether at -30 "C results in electrophilic attack at carbon C3 and production of [((1,2,5-q)-4-methyl-5-oxapenta-1,4diene)Ir(PMe&]+BF4- (4) (see Scheme 3). Other acids, including H03SCF3, H02CCF3, and NH4+PF6-, yield the same cationic product. In the lH NMR spectrum of 4, H3 and H3' resonate at 6 3.55 and 3.27 and strongly couple to each other (JHH = 22.0 Hz!). The signal for H2 appears a t 6 2.23, while H1 and H1' resonate at 6 0.52 and 1.48. In the 13C{lH} NMR spectrum of 4, C3 resonates at 6 54.4, while C2 and C1 appear a t 6 28.3 and 21.8, respectively. The C2 and C 1 signals are doublets (J= 34.2 and 34.5 Hz), reflecting substantial coupling to the phosphorus nuclei of the PMe3 ligands. C4 appears far downfield (6 233.41, clearly indicating that it is not coordinated to the iridium center. The 31P{'H} NMR spectrum shows the expected set of three doublet-of-doublet patterns, due to the three inequivalent PMe3 ligands. While 4 is relatively stable a t -30 "C, it isomerizes to I
..............
I
the iridafuran complex [~uc-CH~C"CH~C(CH~PO"I~(PMe3)3(H)]+BF4-(5) at room temperature. Although the mechanistic details of this rearrangement have not been probed, a likely pathway is shown in Scheme 4. Dissociation of double bond Cl-C2 from the iridium center, followed by C2-C3 bond rotation and C-H2 bond activation, generates the five-membered metallacycle C. Proton migration from C3 t o C1 then produces iridafuran 5.9 The lH NMR spectrum of 5 provides evidence for its aromatic character. The signal for ring proton H3 is shifted downfield, appearing as a doublet (JHP = 6.9 Hz)l0at 6 7.00 in acetone-&. By comparison, H3 in the nonaromatic five-membered-ringcompound 2 resonates a t 6 4.90 in acet0ned6.l~A similar downfield shift is obsewed for the methyl protons on C5, which resonate a t 6 2.42 in 5 vs 6 1.65 in 2 in acetone-d6. The methyl protons on C 1 in 5 resonate at 6 2.83, while the metal hydride appears a t 6 -10.52 and is a doublet of triplets due t o strong coupling to the trans-phosphine (JHP = 117.6 Hz) and weaker coupling to the two cis-phosphines (JHP = 19.7 Hz). In the 13C{lH} NMR spectrum, ring carbons C2, C3, and C4 resonate at 6 231.0, 137.3, and 212.7, respectively, and the C2 signal is split into a widely spaced doublet of triplets due to strong coupling to the truns-PMe3 ligand (Jcp = 82.1 Hz) and weaker coupling t o the two cis-PMe3 ligands (Jcp = 6.1 Hz). Methyl carbons C1 and C5 resonate at 6 37.0 and 23.9, (8! Steric interactions between the phosphines are reduced in the mer isomer. (9) It is possible that the proton transfer step precedes the C-H2 bond activation step. Support for the viability of this alternate sequence comes from the observation that treatment of (Cl)Ir(PMe+ with AgBFd in the presence of excess 3-penten-2-one produces 6 in about 50% yield. We thank one of the reviewers for suggesting this experiment. (10) Selective 3iP-decoupling experiments have established that this coupling is due to an equatorial (ring plane) phosphine ligand. (11)The chemical shifts for the p proton in furan and the p proton in the nonaromatic analogue 4,5-dihydrofuran are 6 6.41 and 4.95, respectively. See Bird, C. W.; Cheeseman, G. W. H. Comprehensive Heterocyclic Chemistry; Pergamon Press: Oxford, 1984; Vol. 4.
Synthesis of Metallafirans from (0xapentadienyl)metals
Organometallics, Vol. 14, No. 11, 1995 5129
Scheme 2
P Scheme 3
treatment of (Cl)Ir(PEt3)3with potassium 4-methyl-5oxapentadienide results in the production of the sixmembered-ring compound, mer-CH=CHCH=C(CHa)1
1
4
respectively. The 31P{1H} NMR spectrum consists of three doublet-of-doubletpatterns for the three inequivalent PMe3 ligands. When compound 5 is treated with lithium diisopropylamide (LDA), methyl group C1 is cleanly deproto-
-
nated, producing fac-CHz=CCH=C(CH3)01r(PMe3)3(H) (2). Reprotonation of 2 occurs at C1, yielding 5 directly.12 Compound 5 does not convert to its mer isomer, even upon heating in tetrahydrofuran at reflux for 2 weeks. However, this mer isomer can be cleanly synthesized by protonating mer-CHz-CCH-C(CH3)OIr(PMe3)dH) (3). Hence, as shown in Scheme 5, treatment of 3 with HBF4eOEh results in electrophilic attack at C1 and production of [mer-
..........,,...
CHB~"CH"C(CH~~O"II:(PM~~)~(H)I+BF~(6).13 In the lH NMR spectrum of 6, ring proton H3 appears = 7.5 Hz)l0 at 6 7.12 (as compared to as a doublet (JHP 6 4.79 in precursor 3),14while methyl groups C1 and C5 resonate at 6 2.82 and 2.41, respectively. The metal hydride, which resides cis to all three phosphine ligands, appears at 6 -24.54 and is split into a closely spaced = 17.5, 12.0 Hz). The 13C{lH} triplet of doublets (JHP NMR spectrum strongly resembles that of 5; ring carbons C2, C3, and C4 resonate a t 6 229.4,137.3, and 214.6, respectively, while methyl carbons C1 and C5 resonate at 6 36.7 and 25.4, respectively. C2 shows the expected strong coupling t o the trans-PMe3 ligand (Jcp = 77.6 Hz) and weaker coupling to the two cis-PMe3 ligands (Jcp = 10.2 Hz). Compound 6 possesses mirror plane symmetry; hence, the trans-diaxial phosphines are equivalent and appear as a doublet in the 31P{lH} NMR spectrum. The unique equatorial phosphine appears as a triplet. C. Reaction of (Cl)Ir(PEt& with Potassium 4Methyl-5-oxapentadienide.As we reported (12) Low-temperature NMR monitoring of this reaction shows no evidence for initial protonation at C3. (13)This reaction can be reversed by the addition of lithium diisopropylamide to the iridafuran. (14)These chemical shifts are observed in acetone-&.
OIr(PEt3MH) (7)(see Scheme 6). This reaction proceeds through 16e compound (q1-4-methyl-5-oxapentadienyl)Ir(PEt3)3 (A)(and perhaps through the related 18e agostic species), which undergoes intramolecular C-H1 bond activation. Unlike the tris(PMe3) reaction system described earlier, ((1,2,5-q)-4-methyl-5-oxapentadienyl)Ir(PEtd3 cannot be isolated or even observed in situ by NMR m0nit0ring.l~ Upon heating in refluxing tetrahydrofuran for 2 h, compound 7 isomerizes to the thermodynamically favored five-membered-ringcompound, mer-CHz=CCH=CI
(CH3)OIr(PEt3)3(H)(8). The fac isomer of 8 is not observed. The X-ray crystal structure of 8, which we reported shows the expected localized bonding around the metallacycle. Ring bond distances and angles are summarized in Table 1. D. Protonation of Compounds 7 and 8. Like
compound 1,mer-(!H=CHCH=C(CH3)01kPEt3)3(H)(7) undergoes electrophilic addition at C3 when treated I
with HBF4.OEt-2, producing [mer-CH=CHCHzC(CHs)= 1
OIr(PEt3)3(H)]+BF4-(9) (see Scheme 7). Other acids, including H03SCF3, H02CCF3, and NH4+PFs-, yield the identical cationic product. Because 9 possesses mirror plane symmetry, the two protons on C3 are equivalent and appear as a broad singlet a t 6 4.27. The olefinic ring protons H1 and H2 resonate at 6 7.22 and 5.99, respectively, while the metal hydride signal appears at 6 -27.60 and is split into a closely spaced triplet of doublets ( J = 16.5, 11.5 Hz) as a result of phosphorus coupling. In the l3C{lH) NMR spectrum, saturated carbon C3 appears a t 6 47.1, while olefinic carbons C1 and C2 resonate a t 6 134.0 and 117.3, respectively. Carbonyl carbon C4 appears far downfield at 6 215.7. As expected, the C1 signal is split into a widely spaced doublet of triplets ( J = 71.8,14.0 Hz) due to phosphorus coupling. The 31P{1H} NMR spectrum consists of a doublethiplet pattern, characteristic of planar metallacycles with a mer arrangement of phosphine ligands. (15) The 1,2,5-r] bonding mode is apparently destabilized by the steric bulk of the tris(PEts) ligand set.
Bleeke et al.
5130 Organometallics, Vol.14,No.11, 1995 Scheme 4
L-
L'
E
3
Scheme 5
Although stable at room temperature, 9 isomcompound [mererizes to the iridafuran
...,,.,.......
C H ~ C Y C H Y C ( C H ~ ~ ~ ~ I : O ~BF4( H ) (10) I C upon heating in tetrahydrofuran a t reflux.16 The probable mechanism for this rearrangement, outlined in Scheme 8, involves migration of the hydride ligand back t o C1, rotation about C2-C3, activation of C-H2, and proton transfer from C3 to C1. Iridafuran 10 is also produced
compound 10 exhibits delocalized n bonding. Ring bonds Ir-C2 [2.029(6)AI and C4-0 [1.258(8) AI have shortened significantly with respect to their distances in 8 (see Table 1)to values intermediate between those of normal single and double bonds.17 Similarly, the C-C distances within the ring have moved toward equalization, with C2-C3 shortening to 1.348(9)A and C3-C4 lengthening to 1.408(10) A. Overall, the circumference of the five-memberedring in 10 has shrunk by 0.169 A from its value in 8 (8.249 A in 10 vs 8.418 A in 8). The five internal angles within the ring range from 77.0(2)" (for C2-Ir-0) to 119.7(6)' (for C3-C40), but their sum of 539.7' falls very close t o the theoretical value of 540" for planar five-membered rings. The spectroscopic and structural data described earlier suggest that several resonance structures contribute to the overall bonding picture in 10. Structure A is supported by the short Ir-C2 distance and the downfield ucarbene-like"chemical shift position of C2. Resonance form B, on the other hand, accounts for the short C4-0 bond distance. The aromatic character of 10 can be explained qualitatively by noting that both resonance structures A and B possess a closed loop of six n electrons. In A, a lone pair on oxygen contributes two n electrons, while in B,a pair of metal-based d electrons completes the Huckel sextet.
'
upon protonation of mer-CH2=CCH-C(CH3)0Ir(PEtd3(H) ( 8 ) (Scheme 9). In this case, electrophilic attack occurs directly on exocyclic carbon Cl.13 The NMR spectra for 10 closely resemble those described earlier for the tris(PMe3) analogue 6. In particular, ring proton H3 is shifted downfield to 6 7.15 (from 6 4.80 in precursor 8),14which is consistent with the presence of an aromatic ring current. Ring methyl groups C1 and C5 resonate at 6 2.91 and 2.42, respectively. The metal hydride signal appears a t 6 -24.68 and is split into a closely spaced triplet of doublets (JHP = 15.5, 12.0 Hz). In the l3C(lH} NMR spectmm, ring carbons C2, C3, and C4 resonate at 6 228.3,138.5, and 214.2, respectively, while methyl carbons C1 and C5 appear a t 6 37.2 and 25.2, respectively. C2 strongly couples t o the trans-PEts ligand (JCP= 75.1 Hz) and weakly couples to the two cis-PEta ligands (Jcp = 9.7 Hz). The 31P{1H} NMR spectrum consists of the expected doublethiplet pattern. The X-ray crystal structure of the PF6- salt of 10 (see Figure 1,Tables 2 and 3) provides additional evidence for the presence of an aromatic ring. Unlike precursor 8, in which the bonding around the ring is localized, ~~~~~
(16) NMR monitoring of the reaction solution also shows the presence of a small quantity of the fac isomer of 10, Wac-
...............
CH3dlrCHlrC(CH3)rrO~JII:olfBF4-, but this ultimately converts to the thermodynamically preferred mer geometry. Selected NMR data for the facial isomer of 10 are summarized here. 'H NMR (acetone-& 22 "C): 6 6.97 (d, JHP = 6.9 Hz, 1,H3), 2.84 (d, JHP = 4.2 Hz, 3, Hl's), 2.35 (s,3, H5's), -12.26 (d o f t , J H P= 114.6,20.4 Hz, 1, IrH). 31PflHl NMR (acetone-&. 22 "C): 6 -20.2 (dd, JPP= 11.0,10.0 Hz,1,PE&), -22.0 (dd, J p p = 21.0, 11.0 Hz, 1, PEtd,'-22.7 (dd, J p p = 21.0, 10.0 Hz, 1, PEt3).
Ci
PEta
9
Ci
PEta
-B
E. Reactions of Compound 10 with Halogens. Ring halogenation is one of the characteristic reactions of aromatic compounds. Therefore, we have explored the reactivity of iridafuran 10 toward I2 and Br2. As shown in Scheme 10, excess 1 2 reacts exclusively ut the metal center to produce the neutral dihalide compound, (17)(a) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, 0.; Watson, D. G.; Taylor, R. J . Chem. Soc., Dalton Trans. 1989,S1. (b) Huheey, J. E. Inorganic Chemistry, 3rd ed.; Harper and Row: New York, 1983; Appendix E and references cited therein. (18)In furan, the bond distances (A) and angles (deg) are as follow^: 0-C, = 1.362, C,-Co = 1.361, Cp-Co = 1.430,C,-O-C, = - 110.65,Ca-Cp-Cp = 106.07. See Bird, C. W.; 106.5, 0-C,-C Cheeseman, G . kYH. Comprehensive Heterocyclic Chemistry; Pergamon Press: Oxford, 1984; Vol. 4. (19) The structural parameters reported for compound 11 in Table 1 and in the text are averages of the bond distances and angles observed in the two independent molecules in the unit cell.
Organometallics, Vol.14, No. 11, 1995 5131
Synthesis of Metallafuram from (0xapentadienyl)metals Scheme 6
-
Table 1. Comparison of Key Bond Distances (A) and Bond Angles (deg) with Estimated Standard
................
Deviations for mer-CHpCCH=C(CI&)OIr(PEts)sH
Ir-C2 C2-C3 c3-c4 C4-0 O-Ir Cl-C2 c4-c5
Bond Distances 2.107(5) 2.029(6) 1.484(6) 1.348(9) 1.408(10) 1.338(6) 1.322(6) 1.258(8) 2.206(4) 2.167(2) 1.326(7) 1.516(9) 1.503(6) 1.505(12)
O-Ir-C2 Ir-C2-C3 c2-c3-c4 C3-C4-0 C4-O-Ir Ir-C2-C1 Cl-C2-C3 O-C4-C5 c3-c4-c5
80.1(1) 108.0(3) 119.7(5) 120.6(4) 111.5(2) 132.6(4) 119.4(5) 114.4(4) 124.9(5)
Bond Angles 77.0(2) 115.3(4) 116.6(6) 119.7(6) 111.1(4) 126.4(5) 118.3(6) 118.6(6) 121.7(6)
1.996(12) 1.349(18) 1.406(21) 1.265(17) 2.078(8) 1.518(22) 1.484(19)
1.971(13) 1.371(16) 1.415(18) 1.283(17) 2.054(7) 1.498(17) 1.481(15)
79.3(5) 113.0(10) 117.1(12) 117.3(11) 113.4(9) 128.3(9) 118.8(12) 116.9(14) 125.9(13)
80.8(4) 111.4(9) 118.8(13) 114.7(10) 114.3(7) 128.1(9) 120.5(12) 117.9(12) 127.5(13)
Reference 3b. This work. Average of two independent molecules.
Scheme 7
...............
I
I
z
8
31P{1H} NMR spectrum of 11 consists of a singlet, consistent with the presence of equivalent trans-diaxial phosphines. The structure of 11 has been confirmed by singlecrystal X-ray diffraction (see Figure 2, Tables 4 and 5). A comparison of structural parameters in 11 with those in 8 and 10 is provided in Table l.19 As in 10, the ring bond distances in 11 exhibit the delocalization that is characteristic of aromatic systems. The two ring carboncarbon bond distances [1.349(18) and 1.406(21)AI and the carbon-oxygen bond distance [1.265(17) 8,l are intermediate in length between those of normal single and double bonds.17 The iridium-ring bond distances of 1.996(12) A for Ir-C2 and 2.078(8) 8, for Ir-0 are quite short, indicating substantial participation by the metal-ligand moiety in ring n bonding. As a result of these strong z interactions, the circumference of the metallacycle in 11 is reduced to 8.094 A (vs 8.249 A in 10). The sum of the five internal angles in 11 is 539.9", which is very close to the theoretical value of 540" for planar five-membered rings. As shown in Scheme 10, excess Brz adds to compound 10 at the metal center and a t C3 of the ring to form the electrophilic aromatic substitution product, trans-
.................
CH3 ~ U C ( B ~ P C ( C H ~ P O U I ( P E ~ ~ )( Z 12hZ0 (B~)Z The substitution at C3 is apparent from the 'H NMR spectrum of 12, because the downfield H3 signal is absent. All other features of the lH, 13C,and 31Pspectra of 12 closely resemble those of 11. The structure of 12 has also been confmned by singlecrystal X-ray diffraction (see Figure 3, Tables 6 and 7). As can be seen from the comparison of structural parameters in Table 1, the bond distances in the ring of 12 closely parallel those in 11. The circumference of the metallacycle in 12 is 8.094 A, identical to that in 11,while the sum of the five internal angles is exactly 540", as required for a planar five-membered ring.
trans-CH3C~CH~(CH3PO"Ir(PEts)z(I)z (11). This reaction involves formal loss of PEt3 and H+ from the Ir center, but its detailed mechanism has not been explored. The 'H NMR spectrum of 11 shows the presence of a downfield signal a t 6 6.82,14indicating that ring proton H3 has not been replaced by halogen and that the aromatic ring remains intact. Unlike the H3 signal for 10, which is a doublet due to equatorial phosphine coupling, the H3 signal for 11 is a sharp singlet, because iodide ligands now occupy the equatorial positions. Ring methyl groups C1 and C5 in 11 resonate a t 6 2.99 and No signals are observed in the 2.48, re~pective1y.l~ upfield "hydride" region of the IH NMR spectrum. In the l3C(lH} NMR spectrum, ring carbons C2, C3, and C4 resonate at Q 223.5, 134.1, and 212.4, respectively, while methyl carbons C1 and C5 resonate at 6 35.4 and 21.6, respectively. C2 resides cis to the two PEt3 ligands and, hence, couples to them weakly (JCP= 5.4 Hz). The
Summary
A new family of metallafurans has been synthesized. These species are obtained either by direct protonation of (oxapentadieny1)metal complexes or by protonation of the oxametallacycles produced from these complexes via C-H bond activation. For example, treatment of (( 1,2,5-q)-4-methy1-5-oxapentadienyl)Ir(PMe& (1)with HBF4.OEtz leads to initial protonation a t C3 and formation of [((1,2,5-~)-4-methyl-5-0xapenta-l,4-diene)Ir(PMe3)3l+BF4-(4), but this species rearranges to the
...............
I
I
iridafuran complex, &c-CH~C-CH-C(CH~PO"I~(PMe&(H)]+BF4- (6). Similarly, protonation of mer-
CHZ=CCH-C(CH~)OI;.(PM~~)~(H) (3)(which is derived (20) Analogous bromination of a related manganafuran system has been reported. See ref 60.
Bleeke et al.
5132 Organometallics, Vol. 14,No. 11, 1995 Scheme 8
c32
Figure
Ir
Q
1.
P1 P2 P3 P4 0
ORTEP
drawing
of
[mer-CHa-
. . . . . . . . . . . . . e .
I
~+ICH+IC(CH3)zlO”1r(PEt3)3(H)lfPF6(PF6- salt of 10).
from 1 via C-H2 bond activation) yields the mer isomer
...............
I
of iridafuran 5, [mer-CH3&CH~C(CH3PO=Ir(PMe3)3(H)I+BF4-(6). In the tris(PEt3) system, treatment of the six-membered-ring compound mer-
c1 c2 c3 c4 c5 c11 c12 C13 C14 C15 C16 c21 c22 C23 C24 C25 C26 C31 C32 c33 c34 c35 C36
2811(1) 2023(2) 5001(2) 3395(2) 7842(2) 1927(4) 361(7) 935(6) 148(6) 749(7) -3(9) 2022(8) 1055(9) 2872(8) 2900(11) 278(7) -285(9) 5568(7) 6952(8) 6369(6) 6497(8) 5392(7) 4632(9) 1985(7) 2286(9) 4229(7) 3438(10) 4511(7) 3876(9)
F1
8855(5)
F2 F3 F4 F5
8252(5) 8980(5) 7426(5) 6812(5) 6720(5) 3344(66)
F6 H
5792(1) 4768(1) 5648(1) 6788(1) 7703(1) 6345(2) 5789(4) 5974(3) 6297(3) 651l(3 6909(5) 4616(4) 4993(5) 4041(4) 40066) 4601(3) 3930(5) 4848(3) 4823(5) 5824(4) 5343(5) 6173(4) 5977(4) 7327(3) 7958(4) 6683(4) 6316(5) 7355(3) 7695(4) 7844(3) 8377(2) 7331(2) 7029(2) 7572(2) 8075(3) 5504(33)
7041(1) 7438(1) 7743(1) 6417(1) 5431(1) 8037(2) 5612(4) 6503(4) 6998(5) 7792(4) 8382(6) 8574(5) 9030(5) 7069(5) 6120(6) 7040(5) 7277(7) 8171(5) 8652(6) 7107(5) 6378(5) 8670(4) 9422(5) 6085(5) 5629(6) 5460(4) 4743(5) 7041(5) 7765(6) 6246(3) 5036(3) 5011(3) 5827(3) 4628(3) 5870(3) 6326(40)
81(2) 75(2) 78(2) 842) 87W 81(2) 52(20)
6H=CHCH=C(CH3)OIkPEt3)3(H)( 7 )with HBF4.OEt2 leads to initial protonation at C3 and formation of [mer~H=CHCHZC(CH~)=OI~(PE~~)~(H)I+BF~(91, but upon heating, this compound rearranges to the iridafuran
...............
-
complex, [mer-CH3~-CH-C(CH3)O-I~(PEt3)3(H)]+BF4- (10). The identical iridafuran is obtained upon protonation of the five-membered-ringisomer of 7 , mer-
CH2=CCH=C(CH3)0Ir(PEt3)3(H)(8). The aromatic character of iridafurans 5,6, and 10 is supported by downfield IH NMR chemical shifts for ring
proton H3. Furthermore, the X-ray crystal structure of 10 shows a planar metallacycle and delocalized JC bonding around the ring. Treatment of compound 10 with excess Brz leads to electrophilic substitution a t C3
.................
and production of trans-CH3 d~C(BrW(CH3PO~I:(PEt&Or)z (12). The X-ray crystal structure of 12 shows a planar metallacycle whose circumference is smaller than that of 10 as a result of very strong JC interactions within the ring.
Organometallics,
Synthesis of Metallafurans from (0xapentadienyl)metals
Table 3. Selected Bond Distances (A)and Bond Angles (deg) with Estimated Standard Deviations
n
r,,,
................
for C ~ ~ ~ - C H S ~ - C H ~ + C ( C ~ ) ~ I ~ ( P E ~ S ) S ( H ) I ' P F ~ (PFs- Salt of 10) Ir-P1 Ir-P2 Ir-P3 Ir-0 Ir-C2 Ir-H
Bond Distances 2.347(2) 0-C4 2.387(2) Cl-C2 2.366(2) C2-C3 2.206(4) c3-c4 2.029(6) c4-c5 1.431(67) Bond Angles 95.1(1) 0-Ir-H 170.3(1) C2-Ir-H 92.3(1) 0-Ir-C2 95.2(1) Ir-0-C4 98.9(1) Ir-C2-C1 89.8(1) Ir-C2-C3 87.0(2) Cl-C2-C3 175.6(2) c2-c3-c4 86.0(2) O-C4-C3 90.8(27) O-C4-C5 84.8(26) C3-C4-C5 83.7(26)
Pl-Ir-P2 Pl-Ir-P3 P2-Ir-P3 P1-Ir-0 P2-Ir-0 P3 -Ir-0 Pl-Ir-C2 P2-Ir- C2 P3-1r- C2 P1-Ir-H P2-Ir-H P3-Ir-H
Vol.14,No.11, 1995 5133
C23
1.258(8) 1.516(9) 1.348(9) 1.408(10) 1.505(12)
172.6(26) 99.0(26) 77.0(2) 111.1(4) 126.4(5) 115.3(4) 118.3(6) 116.6(6) 119.7(6) 118.6(6) 121.7(6)
V
0C14
c15c1C16 1&c13
2. ORTEP ...............
Figure
drawing
of
trans-CH3-
of
trans-CH3-
~-CHLZC(CH3~O~I~(PEt3)z(I)z (11).
Scheme 10
BF;
PEb
1L Br3
LP
Experimental Section General Comments. All manipulations were carried out under a nitrogen atmosphere, using either glovebox or doublemanifold Schlenk techniques. Solvents were stored under nitrogen after being distilled from the appropriate drying agents. Deuterated NMR solvents were obtained from Cambridge Isotope Laboratories in 1 g sealed vials and used as received. The following reagents were used as obtained from the supplier indicated: tetrafluoroboric acid (Aldrich), trifluoromethanesulfonic acid (Aldrich), trifluoroacetic acid (Aldrich), ammonium hexafluorophosphate (Aldrich), lithium diisopropylamide (Aldrich), iodine (Aldrich), bromine (Fisher), flash silica gel (Aldrich). (( 1,2,5-y)-4-Methyl-5-oxapentadienyl)Ir-
3. ORTEP .................
Figure
drawing
correlation spectroscopy), and HMQC (IH-detected multiple quantum coherence) experiments aided in assigning some of the 1H and 13Cpeaks. The spectra of cationic compounds were recorded in acetone-&, while those of neutral compounds were recorded in benzene-&. In addition, 'H NMR spectra of neutral compounds were obtained in acetone-& to allow direct comparisons of IH NMR chemical shifts in related neutral and cationic compounds. Note: In all of the NMR spectra, carbon atoms and associated hydrogens in the oxapentadienyl group are numbered by starting a t the end of the chain opposite (PMed3 (l),mer-CHz=dCH=C(CH3)0Ik(PMe&(H)(3),meroxygen. I Microanalyses were performed by Galbraith Laboratories, dH=CHCH=C(CH3)0IkPEt3)3(H)(71, and mer-CHpCCH-CInc. (Knoxville, TN). (CH3)0IkPEt&H) (8)were prepared as previously described.3b Synthesis of fac-CHz=CCH-C(CHs)OIkPMe~)s(H) (2). NMR experiments were performed on a Varian Unity-300 Note: Previously, we observed compound 2 in a complex spectrometer (IH, 300 MHz; 13C, 75 MHz; 31P, 121 MHz), a mixture of isomers, including compounds 1 and 3.3bThe Varian Unity-500 spectrometer (IH, 500 MHz; 13C,125 MHz; procedure described here produced 2 as a pure species, 31P,202 MHz), or a Varian VXR-600 spectrometer (IH, 600 allowing full spectral characterization. MHz; 13C, 150 MHz; 31P,242 MHz). lH and 13C spectra were referenced to tetramethylsilane, while 31Pspectra were refer[fac-CH3C"CH~(CH3~-I~(PMe3)3(H)I+BF4(6)(0.38 g, enced t o external H3P04. In general, IH connectivities were 6.4 x lo-* mol) was dissolved in 100 mL of tetrahydrofuran determined from COSY (IH-IH correlation spectroscopy)data. (THF) and cooled t o -30 "C. A cold (-30 "C) solution of AFT (attached proton test), HETCOR (13C-'H heteronuclear
...............
5134 Organometallics, Vol. 14, No. 11, 1995
Bleeke et al.
Table 4. Atomic Coordinates ( x lo4)and Equivalent Isotropic Displacement Coefficients (Azx 10s) with
................
I
Estimated Standard Deviations for Non-HydrogenAtoms in trane-CHsCI%H~(CHs)llOl.ZI~(PEts)z(I)z (11) molecule 1 atom Irl I1 I2 P1 P2 01
c1
c2 c3 c4 c5 c11 c12 C13 C14 C15 C16 c21 c22 C23 C24 C25 C26
X
3971(1) 5168(1) 4004(1) 3993(2) 3927(2) 3036(4) 4211(8) 3791(6) 3189(6) 2795(7) 2125(7) 4202(8) 4822(10) 4504(8) 4508(11) 3250(9) 2911(10) 4202(8) 4875(8) 3147(6) 2770(7) 4311(8) 4363(8)
molecule 2
Y
z
4054(1) 4288(1) 1198(1) 3011(4) 5125(4) 3943(10) 7259(16) 6083(14) 6283(14) 5139(17) 5132(22) 4244(19) 4702(21) 1409(17) 658(22) 2465(28) 1400(25) 4094(18) 3749(24) 5566(17) 4211(19) 6927(17) 7653(19)
2376(1) 2878(1) 2835(1) 1509(2) 3223(1) 1969(3) 1988(7) 1990(5) 1691(5) 1674(6) 1362(7) 1034(7) 1234(9) 1645(7) 1094(9) 943(8) 1067(11) 3916(6) 4214(7) 3109(6) 3093(7) 3421(6) 3999(6)
Ues)
Table 6. Selected Bond Distances (A)and Angles (deg) with Estimated Standard Deviations for
................
I
I
truns-CHsC-CH~C(CHs)llOl.ZIr(PEts)z(I)z(11) molecule 1 Irl-I1 Irl-I2 Irl-P1 Irl-P2 Irl-01 Irl-C2 01-C4 Cl-C2 C2-C3 c3-c4 c4-c5 11-Irl-I2 11-Irl-P1 12-Irl-PI I1-Ir 1-P2 I2 -1r 1-P2 Pl-Irl-P2 I1-1r 1-01 12-11-1-01 P1-Irl-01 P2-11-1-01 11- Irl -C2 12-Irl-C2 Pl-Irl-C2 P2-Irl-C2 Ol-Irl-C2 Ir 1-01 -C4 Irl-C2-C1 Irl-C2-C3 Cl-C2-C3 c2-c3-c4 01-C4-C3 01-C4-C5 c3-c4-c5
molecule 2
Bond Distances Ir2-I3 2.665(1) 2.787(1) Ir2-I4 Ir2-P3 2.375(4) 2.364(4) Ir2-P4 Ir2-02 2.079(8) Ir2-C7 2.013(12) 1.291(17) 02-C9 C6-C7 1.473(23) 1.353(18) C7-C8 1.396(22) C8-C9 1.491(20) c9-c10 Bond Angles 92.6(1) 13-Ir2-I4 90.7(1) 13-Ir2-P3 90.3(1) 14-Ir2-P3 90.5(1) 13-Ir2-P4 90.5(1) 14-Ir2-P4 P3-Ir2-P4 178.6(1) 178.0(3) 13-Ir2-02 89.4(3) 14-Ir2-02 .89.1(3) P3-Ir2-02 P4-Ir2-02 89.7(3) 97.4(4) 13-Ir2-C7 14-Ir2-C7 170.0(4) 90.3(4) P3-Ir2-C7 88.7(4) P4-Ir2-C7 80.6(5) 02-Ir2-C7 112.4(9) Ir2-02-C9 129.3(10) Ir2-C7-C6 110.4(10) Ir2-C7-C8 120.3(12) C6-C7-C8 119.9(12) C7-C8-C9 116.6(12) 02-C9-C8 115.5(14) 02-C9-C10 127.9(13) C8-Cg-ClO
2.666(1) 2.792(1) 2.371(5) 2.368(4) 2.077(7) 1.978(11) 1.238(16) 1.563(20) 1.345(17) 1.415(21) 1.477(17)
92.4(1) 90.3(1) 89.9(1) 90.8(1) 90.2(1) 178.8(1) 177.2(3) 90.0(2) 88.3(3) 90.6(3) 99.7(4) 167.9(4) 90.5(4) 89.1(4) 77.9(4) 114.3(8) 127.3(8) 115.5(10) 117.2(11) 114.3(12) 117.9(10) 118.2(14) 123.8(13) lithium diisopropylamide (0.069 g, 6.4 x mol) in 20 mL of THF was then added dropwise with vigorous stirring. O an orange oil, Removal of the THF solvent in U ~ C U revealed which was extracted with benzene and filtered. The benzene was removed under vacuum, and the resulting residue was
atom Ir2 I3 I4 P3 P4 02 C6 c7 C8 c9 c10 C31 C32 c33 c34 c35 C36 C41 C42 c43 c44 c45 C46
Y
X
2444(1) 2972(1) 2920(1) 1582(2) 3294(2) 1999(4) 2059(7) 20366) 1715(6) 1715(6) 1367(8) 982(10) 1171(13) 1103(8) 1307(10) 1726(8) 1184(10) 3490(6) 4085(7) 3148(7) 3139(9) 4004(6) 4333(8)
U(ed
2
7335(1) 7589(1) 4482(1) 6261(5) 8410(4) 7204(10) 10583(15) 9297(12) 9549(15) 8345(17) 8339(21) 5795(24) 4509(32) 7494(21) 7970(24) 4726(17) 3947(21) 10211(15) 10937(18) 8874U5) 7486(17) 7376(15) 7032(22)
-1012(1) 164(1) -978(1) -964(2) -1082(1) -1929(3) -786(6) -1220(5) -1802(6) -2170(5) -2820(6) -1692(10) -1988(13) -769(8) - 157(9) -451(7) -433(9) -717(7) -662(7) -1857(6) -2239(7) -830(6) -180(7)
Table 6. Atomic Coordinates ( x 104) and Equivalent Isotropic Displacement Coefficients (k x 109) with Standard Deviations for Non-Hydrogen Atoms in I
.................
I
trane-CHsCI%(Br)I%(CHs)~Ir(PEts)z(Br)z (12) atom Ir Brl Br2 Br3 P1 P2 0
c1
c2 c3 c4 c5 c11 c12 C13 C14 C15 C16 c 21 c22 C23 C24 C25 C26
X
7460(1) 8411(1) 6416(1) 8232(1) 6487(2) 8419(2) 6710(5) 8948(9) 8133(7) 7765(8) 6987(10) 6472(10) 5464(9) 4818(9) 6155(10) 5488(11) 6979(12) 6986(12) 9596(9) 9804(9) 8058(10) 7183(11) 8546(11) 8988(20)
.Y
541(1) 173(2) 1930(1) -1345(2) -958(3) 2081(3) 782(7) -1185(13) -470(11) -464(12) 208(11) 312(12) -1080(13) -120(13) -913(13) - 1799(15) -2404(13) -2957( 13) 1706114) 1346(13) 2865(13) 3500(14) 3084(15) 4295(27)
2
8437(1) 10143(1) 8970(1) 6010(1) 8554(2) 8389(3) 7005(6) 8327(10) 7834(8) 6843(9) 6407(9) 5360(8) 7533(10) 7375(13) 9636(10) 9734(11) 8636(12) 7732(14) 8547(11) 7632(11) 7251(12) 7026(14) 9420(15) 9192(24)
washed repeatedly with pentane, producing a gummy yellow powder of 2. Yield: 0.24 g, 75%. Anal. Calcd for C14H34IrOPa: C, 33.39; H, 6.82. Found: C, 33.08; H, 6.90. 1H NMR (acetone-&, 23 "C):6 5.01 (br d, JHP = 17.0 Hz, 1, H l ) , 4.90 (d, JHP = 5.7 Hz, 1, H3), 3.97 (m, 1, Hl'), 1.69 (d, J H P= 9.3 Hz, 9, PMea), 1.65 ( 8 , 3, H5's), 1.57 (d, JHP = 8.1 Hz, = 8.1 Hz, 9, PMes), -10.58 (d oft, JHP = 9, PMes), 1.31 (d, JHP 156.6, 20.7 Hz, 1, IrH). lH NMR (benzene-&, 8 "C): 6 5.90 (br d, JHP = 17.0 Hz, 1, HI), 5.70 (d, JHP = 5.5 Hz, 1, H3), 4.41 (m, 1,Hl'), 2.18 (s, 3, H5's), 1.32 (d, J H =~9.3 Hz, 9, PMeS), 1.25 (d, JHP = 8.5 Hz, 9, = 7.5 Hz, 9, PMea), -10.02 (d o f t , JHP = PMea), 1.10 (d, JHP 162.5, 20.5 Hz, 1, IrH). l3C(lH} NMR (benzene-&, 8 "C): 6 170.4 (d, JCP = 10.3 Hz, C4) 160.0 (br d, JCP= 86.1 Hz,C2), 116.0 ( 6 , C3), 100.9 (s,
Synthesis of Metallafurans from (0xapentadienyl)metals
Organometallics, Vol. 14, No. 11, 1995 5135
Table 7 . Selected Bond Distances (A)and Bond PMes), 1.43 (d, JHP = 9.0 Hz, 9, PMed, -10.52 (d o f t , JHP = Angles (deg) with Estimated Standard Deviations 117.6, 19.7 Hz, 1,IrH). = 82.1, for t r a n e - C H s ~ ~ ( B r ) ~ C ( C H s ) ~I ~ 1 r ( P E t s ) z ( B r ) 2 13C(lH}NMR (acetone-ds, 22 "C): 6 231.0 (d oft, JCP 6.1 Hz, C2), 212.7 (m, C4), 137.3 (8,C3), 37.0 (9, JCP = 6.0 Hz, (12) .~ Cl), 23.9 (s, C5), 22.2 (d, JCP = 43.0 Hz, PMed, 19.3 (d, JCP = 32.0 Hz, PMed, 15.2 (d, JCP = 30.3 Hz, PMe3). Bond Distances
.................
Ir-Brl Ir-Br2 Ir-P1 Ir-P2 Ir-0 Ir-C2 Br 1-1r -Br2 Brl-Ir-Pl Bra-Ir-P1 Brl-Ir-P2 Br2-Ir-P2 Pl-Ir-P2 Brl-Ir-0 Bra-Ir-0 P1-Ir-0 P2-Ir-0 Br 1-Ir -C2 Br2-Ir-C2
2.485(2) 2.596(2) 2.369(4) 2.365(4) 2.054(7) 1.971(13)
0-C4 Cl-C2 C2-C3 c3-c4 C3-Br3 c4-c5
Bond Angles 92.3(1) Pl-Ir-C2 89.2(1) P2-Ir-C2 88.4(1) 0-Ir-C2 89.2(1) Ir-0-C4 89.3(1) Ir-C2-C1 177.1(1) Ir-C2-C3 177.1(2) Cl-C2-C3 90.6(2) Br3-C3-C2 90.5(2) Br3-C3-C4 91.2(2) C2-C3-C4 96.3(3) O-C4-C3 171.4(3) O-C4-C5 c3-c4-c5
1.283(17) 1.498(17) 1.371(16) 1.415(18) 1.910(14) 1.481(15) 91.4(4) 91.1(4) 80.8(4) 114.3(7) 128.1(9) 111.4(9) 120.5(12) 123.5(9) 117.8(9) 118.8(13) 114.7(10) 117.9(12) 127.5(13)
31P(1H}NMR (acetone-ds, 22 "C): 6 -41.9 (dd, JPP = 22.0, 13.4 Hz, 1, PMes), -47.3 (dd, J p p = 13.4, 12.2 Hz, 1, PMes), -48.8 (dd, J p p = 22.0, 12.2 Hz, 1, PMe3).
-
................
Synthesis of [ m e r - C H s d ~ H ~ ( C H s ) ~ ~ ~ = ( P M e , ) , (H)l+BF4- (6). A solution of mer-CH2=CCH=C(CH3)0Ir(PMe3MH) (3) (0.086 g, 1.7 x mmol) in 20 mL of diethyl ether was cooled to -30 "C. HBF4.OEt2 (0.028 g, 1.7 x
mol) in 5 mL of diethyl ether was added dropwise to the cold solution, causing a fluffy,white powder (6)t o precipitate out of solution. The powder was collected and washed with small portions of diethyl ether and pentane. Yield: 0.091 g, 90%. Analogous products were obtained using the following acids: H03SCF3, H02CCF3, and N&+PF6-. Elemental analysis was obtained on the PF6- salt. Anal. Calcd for C14H35F6IrOP4: C, 25.88; H, 5.44. Found: C, 25.49; H, 5.49. lH NMR (acetone-&, 22 "C): 6 7.12 (d, J H P= 7.5 Hz, 1,H3), 2.82 (d, JHP = 5.0 Hz, 3, Hl's), 2.41 (m, 3, H5's), 1.76 (d, JHP = 8.4 Hz, 9, PMe3), 1.50 (m, 18, PMeis), -24.54 (t of d, JHP = 17.5, 12.0 Hz, IrH). Cl), 22.6 (d, JCP = 37.3 Hz, PMed, 20.2 (d, JCP = 26.5 Hz, l3C('H} NMR (acetone-&, 22 "C): 6 229.4 (d oft, JCP= 77.6, PMed, 19.3 (s, C5), 14.9 (d, Jcp = 26.0 Hz, PMe3). 10.2 Hz, C2), 214.6 (d, J c p = 7.5 Hz, C4), 137.3 (s, C3), 36.7 31P{1H}NMR (benzene-&, 8 "C): 6 -46.5 (dd, J p p = 15.0, (d, Jcp = 5.4 Hz, Cl), 25.4 (9, C5), 19.0 (d, Jcp = 30.7 Hz, 10.3 Hz, 1, PMes), -47.5 (dd, J p p = 10.3, 7.0 Hz, 1, PMe3), equatorial PMe3), 17.2 (virtual t, J c p = 38.9 Hz, axial PMeS's). -47.8 (dd, Jpp = 15.0, 7.0 Hz, 1, PMe3). Synt,hesisof [((1,2,5-q)-4-Methyl-5-oxapenta-l,4-diene)- 31P{1H}NMR (acetone-ds, 22 "C): 6 -39.2 (d, JPP= 25.6 Ir(PMe&(H)]+BF4- (4). ((1,2,5-7)-4-Methyl-5-oxapentadi- Hz, 2, axial PMes's), -50.9 (t, J p p = 25.6 Hz, 1, equatorial PMe3). enyl)Ir(PMe& (1)(0.35 g, 7.0 x mol) was dissolved in 20 mL of diethyl ether and cooled to -30 "C. Cold (-30 "C) Synthesis of [mer-~H.~CHcHzc(CHs)=O~(PEt3)3(H)l+HBF4.0Et2 (0.11 g, 7.0 x 10-4 mol) in 5 mL of diethyl ether BF4- (9). mer-CH=CHCH=C(CH3)OIi(PEt3)3(H) (7)(0.31 g, was added dropwise with stirring, causing 4 to precipitate as 5.0 x loW4mol) was dissolved in 20 mL of diethyl ether and a fluffy, white powder. The precipitate was collected and cooled to -30 "C. HBF4.0Et2 (0.081 g, 5.0 x mol) in 5 washed with diethyl ether and pentane. Yield: 0.38 g, 92%. mL of diethyl ether was added dropwise to the solution, Analogous products were obtained using the following acids: causing 9 to precipitate as a fine, off-white powder. The H03SCF3, H02CCF3, and NH4+PF6-. Elemental analysis of 4 diethyl ether was removed under vacuum, and the product was could not be obtained because of its thermal instability; washed with pentane. Yield: 0.33 g, 92%. Analogous products however, analysis of isomeric compound 5 (to which 4 cleanly were obtained using the following acids: H03SCF3, H02CCF3, converts) was obtained. and NH4+PFs-. Elemental analysis was obtained on the PF6'H NMR (acetone-&, -30 "C): 6 3.55 (dd, JHH = 22.0 Hz, salt. Anal. Calcd for C23H53FsIrOP4: C, 35.60; H, 6.90. JHP 11.0 Hz, 1, H3 or H3'), 3.27 (dd, JHH = 22.0,4.8 Hz, 1, Found: C, 35.40; H, 6.72. H3' or H3), 2.40 (s,3, H5's), 2.23(m, 1,H2), 1.69 (d, Jnp = 8.4 lH NMR (acetone-&, 22 "C): 6 7.22 (m, 1, Hl), 5.99 (m, 1, Hz, 9, PMe3), 1.54 (d, JHP = 8.4 Hz, 9, PMed, 1.49 (d, JHP = H2), 4.27 (br s, 2, H3's), 2.33 (9, 3, H5's), 1.99, 1.90, 1.80 (m's, 10.8 Hz, 9, PMe3), 1.48 (m, 1, H1' or H l ) , 0.52 (m, 1, H1 or 18, CH2's of PEta's), 1 . 1 1 , l . O l (m's, 27, CHis of PEts's), -27.60 Hl'). (t of d, J H P= 16.5, 11.5 Hz, 1, IrH). 31C{1H}NMR (acetone-ds, -30 "C): 6 233.4 (d, JCP= 9.9 13C{lH}NMR (acetone-de, 22 "C): 6 215.7 (s, C4), 134.0 (d Hz, C4), 54.4 (s,C3), 28.5 (s,C5), 28.3 (dd, Jcp = 34.2, 7.3 Hz, o f t , J c p = 71.8, 14.0 Hz, Cl), 117.3 (s,C2), 47.1 (s, C3), 30.7 C2), 21.8 (d, Jcp = 34.5 Hz, Cl), 20.2 (d, JCP= 26.8 Hz, PMes), (s, C5), 20.2 (d, Jcp = 25.5 Hz, CH2's of equatorial PEts), 17.0 19.5 (d, J c p = 26.8 Hz, PMe3), 18.3 (d, JCP= 43.5 Hz, PMe3). (virtual t, Jcp = 34.0 Hz, CHis of axial PEtis), 8.6 (s, CHis of 31P{1H}NMR (acetone-&, -30 "C): 6 -38.5 (dd, J p p = 18.9, equatorial PEts), 8.1 (s, CHis of axial PEtis). 13.5 Hz, 1, PMes), -42.0 (dd, J p p = 35.8, 13.5 Hz, 1, PMes), 31P{1H}NMR (acetone-ds, 22 "C): 6 -6.9 (d, J p p = 17.0 Hz, -45.8 (dd, J p p = 35.8, 18.9 Hz, 1, PMe3). 2, axial PEtis), -19.1 (t, J p p = 17.0 Hz, 1, equatorial PEt3).
...............
................
Synthesis of ~=c-CHsdZICH-C(CHs)-O-I~(PMe,),(H)]+BF4- (5). [((1,2,5-~)-4-Methyl-5-oxapenta-1,4-diene)Ir- Synthesis of [mer-CHsCZICHZIC(CHS)~llI~(PEt3),(H)l+BF4- (10). Method 1: A solution of [mer(PMe3)3(H)]+BF4-(4)(0.38 g, 6.4 x mol) was dissolved in 20 mL of tetrahydrofuran and stirred at room temperature for 8 h. After the solvent was removed in uucuo and the light yellow residue was washed with pentane and diethyl ether, 5 was isolated as a light yellow powder. Yield: 0.37 g, 97%. Analogous products were obtained with the following anions: 03SCF3-, 02CCF3-, and PFs-. Elemental analysis was obtained on the PFs- salt. Anal. Calcd for C14H35F&OP4: C, 25.88; H, 5.44. Found: C, 25.68; H, 5.34. lH NMR (acetone-ds, 22 "C): 6 7.00 (d, JHP = 6.9 Hz, 1,H3), = 5.1 Hz, 3, Hl's), 2.42 (d, Jnp = 3.1 Hz, 3, H5's), 2.83 (d, JHP 1.90 (d, JHP = 10.8 Hz, 9, PMes), 1.79 (d, JHP = 9.3 Hz, 9,
hH-CHCH2C(CH3)=OIkPEt3)3(H)I+BF4-(9) (0.082 g, 1.1 x mol) in 25 mL of tetrahydrofuran was heated at reflux for 10 h. After the solvent was removed in uucuo and the residue was washed with diethyl ether and pentane, 10 was isolated as a yellow powder. Yield: 0.057 g, 70%. Method 2: A solution of mer-CH2=CCH=C(CH3)OIk(PEt3)3(H) (8) (0.31 g, 5.0 x mol) in 15 mL of diethyl ether was cooled to -30 "C. HBF4-OEt2 (0.081 g, 5.0 x mol) in 5 mL of diethyl ether was added dropwise to the cold solution, causing compound 10 to precipitate as a yellow powder. The
5136 Organometallics, Vol. 14, No. 11, 1995
Bleeke et al.
Table 8. X-ray Diffraction Structure Summary comnound 10
formula formula weight crystal system space group
a (A) b (A) c
(A)
a (deg)
P (de& @$)
z crystal dimensions (mm) crystal color and habit densitycalcd(g/cm3) radiation (A) scan type scan rate (deg/min in w ) scan range (w)(deg) 20 range (deg) data collected total decay temperature no. of data collected no. of unique data no. of data with I > 3dI) Mo Ka linear abs coeff (cm-l) abs correction applied data to parameter ratio R"
RW" GOP
11
Crystal Parameters and Data Collection Summary C23H53FsIrOP4 C17H3712IrOP2 775.7 762.9 monoclinic monoclinic P21lc P21In 10.103(4) 24.527(8) 20.435(7) 8.944(2) 15.853(7) 24.940(7) 90 90 96.12(3) 115.13(2) 90 90 3254(2) 4953(2) 4 8 0.68 x 0.70 x 0.56 0.10 x 0.50 x 0.22 yellow cube dark orange plate 1.583 2.046 Mo Ka (1= 0.710 73) Mo Ka (1= 0.710 73) 8-20 w variable, 3.50-14.65 variable, 2.49-14.65 1.20 plus Ka separation 1.20 plus Ka separation 3.0-55.0 3.0-50.0 h, 0 to 13 h, 0 to 29 k, 0 to 26 k, 0 to 10 1, -20 to +20 1, -29 to +26 none detected none detected 295 296 Treatment of Intensity Data and Refinement Summary 8099 9507 8662 7469 5231 5368 80.16 43.49 semiempirical semiempirical 16.51 12.51 0.0367 0.0364 O.041gb 0.0514c 0.76 1.56
powder was collected and washed with small portions of diethyl ether. Yield: 0.30 g, 83%. Analogous products were obtained with the following anions: 03SCF3-, 02CCF3-, and PFs-. Elemental andysis was obtained on the PF6- salt. And. Calcd for C23H53F6IrOP4: C, 35.60; H, 6.90. Found: C, 35.71; H, 7.18. 'H NMR (acetone-&, 22 "C): 6 7.15 (d, JHP = 8.0 Hz, 1,H3), 2.91 (d, JHP = 4.5 Hz, 3, Hl's), 2.42 (m, 3, H5's), 2.04, 1.86 (m's, 18, CH2's of PEts), 1.19, 1.03 (m's, 27, CHis of PEts), -24.68 (t of d, JHP = 15.5, 12.0 Hz, 1, IrH). 13C{lH}NMR (acetone-&, 22 "C): 6 228.3 (d oft, J c p = 75.1, 9.7 Hz, C2), 214.2 (8,C4), 138.5 (s, C3), 37.2 (8,Cl),25.2 (s, C5), 18.8 (d, J c p = 26.6 Hz, C H i s of equatorial PEtis), 17.6 (virtual t, J c p = 33.3 Hz, C H i s of axial PEt3), 7.9 (s, C H i s of equatorial PEt3), 7.7 (s, CHis of axial PEtis). 31P{1H}NMR (acetone&, 22 "C): 6 -16.5 (d, J p p = 22.6 Hz, 2, axial PEtis), -23.3 (t,JPP = 22.6 Hz, 1,equatorial PEt3).
12
monoclinic P21/c 15.572(4) 11.786(4) 14.567(5) 90 108.86(2) 90 2530.0(13) 4 0.22 x 0.40 x 0.20 orange prism 1.970 Mo Ka (1= 0.710 73) 8-28 variable, 3.00-14.65 1.20 plus Ka separation 3.0-50.0 h, -18 to $17 k, -14 to 0 1, 0 to 17 none detected 296 4869 4434 2255 101.45 semiempirical 10.4:l 0.0363 0.0375d 1.03
vacuum, the residue was redissolved in a minimal quantity of THF. Slow diffusion of diethyl ether into this THF solution at -30 "C caused 11to crystallize as very dark orange plates. Yield: 0.045 g, 42%. Anal. Calcd for C17H3712IrOP2: C, 26.67; H, 4.88. Found: C, 25.84; H, 4.84. lH NMR (acetone-&, 22 "C): 6 6.82 (6, 1, H3), 2.99 (s, 3, Hl's), 2.48 (8, 3, H5's), 2.19, 1.87 (m's, 12, CH;s of PEts's), 1.11(m, 18, CH3's of PEtis). lH NMR (benzene-&, 22 "C): 6 6.10 (s, 1, H3), 2.91 (s, 3, Hl's), 2.06 (m, 6, CHis of PEtis), 1.88 (s, 3, H5's), 1.78 (m, 6, C H i s of PEtis), 0.95 (m, 18, C H i s of PEtis). l3C(lH} NMR (benzene-&, 22 "C): 6 223.5 (t,JCP = 5.4 Hz, C2), 212.4 (s, C4), 134.1 (8,C3), 35.4 (s, Cl),21.6 (s, C5), 15.8 (virtual t, J c p = 33.6 Hz, C H i s of PEtis), 9.0 (s, CH3's of
PEtis). 31P{1H}NMR (benzene-&, 22 "c): 6 -35.2 (s,2, equivalent
axial PEtis). ................ ................. Synthesis of t r u n s - C H s C ~ H ~ ( C H s ) ~ ~ I z I : ( P E t , ) , ............... trune-CHsC~(Br)llC(CH~)~IrSynthesis of (PEts)z(Br)z (12). A solution of [mer-CHa( 1 ) ~(11). A solution of [mer-CHa~1~CH.sZC(CHs)110"1:............... (PEt&(H)]+BF4- (10) (0.10 g, 1.4 x loW4mol) in 15 mL of I I
I
tetrahydrofuran (THF) was cooled to -30 "C, and excess iodine mol) in 15 mL of THF was added dropwise (0.072 g, 2.8 x with stirring. After the resulting solution was warmed to room temperature and stirred for 27 h, the volatiles were removed under vacuum. The residue was extracted with benzene and filtered through Celite to yield a n orange solution. After in uucuo concentration, the solution was placed onto a silica gel chromatography column and eluted with THF. The first orange band was collected. After removal of the solvent under
I
CLICHfzC(CH3)110'I~PEt3)3(H)I+BF4-(10)(0.18 g, 2.5 x mol) in 15 mL of tetrahydrofuran was cooled to -30 "C. Excess mol) was added to the solution bromine (0.10 g, 6.0 x dropwise, causing the color to change from yellow to orange. After the solution was warmed to room temperature, the volatiles were removed under vacuum. The residue was then extracted with pentane, filtered through Celite, and reduced in volume to 10 mL. Subsequent cooling of the solution to -30 "C caused 12 to crystallize as orange needles. Yield: 0.15 g,
Synthesis of Metallafurans from (0xapentadienyl)metals 80%. Anal. Calcd for C1,H361rBr3P20: C, 27.21; H, 4.85. Found: C, 27.15; H, 4.78. 1H NMR (acetone-&, 22 “C): 6 2.77 (s, 3, Hl’s), 2.67 ( 8 , 3, HFs), 2.00, 1.74 (m’s, 12, CHis of PEts’s), 1.07 (m, 18, CH3’s of PEtis). ‘H NMR (benzene-&, 22 “C): 6 2.86 (s, 3, Hl’s), 2.20 (s, 3, H5’s), 1.80, 1.60 (m’s, 12, C H i s of PEh’s), 0.85 (m, 18, CHis of PEts’s). 13C{1H}NMR (benzene-&, 22 “C): 6 214.8 (br s, C2), 208.5 (9, C4), 115.4 (5, C3), 33.6 (s, Cl), 23.1 (s, C5), 13.5 (virtual t, J c p = 30.4 Hz, C H i s of PEts’S), 7.8 (9, CH3’s Of PEta’s). 31P{1H}NMR (benzene-&, 22 “c): 6 -25.3 (s,2, equivalent axial PEta’s).
X-ray Diffraction Studies of [mer-CHs............... C~H~(CHs)lOrzIr(PEts)s(H)I+PFa(PF6- salt of lo), ............... t r a n ~ - C H s d ~ H ~ ( C H s ) l O r z I ~ ( P E t ~(ll), ) ~ ( I ) and ~ ................. I
trans-CHsCt?.C(Br)~(CHs)~~Ir(PEt,),(Br), (12). Single crystals of compounds 10, 11, and 12 were sealed in glass capillaries under an inert atmosphere. Data were collected at room temperature on a Siemens R3mN diffractometer, using graphite-monochromated Mo K a radiation. Standard reflections were measured every 100 events as check reflections for crystal deterioration and/or misalignment. All data reduction and refinement were done using the Siemens SHELXTL PLUS package on a VAX 3100 workstation.21 Crystal data and details of data collection and structure analysis are listed in Table 8. The iridium atom positions in 10,11, and 12 were determined by direct methods. In each case, the remaining non(21)Atomic scattering factors were obtained from the following: International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. IV.
Organometallics, Vol. 14, No. 11, 1995 5137 hydrogen atoms were found by successive full-matrix leastsquares refinement and difference Fourier map calculations. All non-hydrogen atoms were refined anisotropically, except for two carbon atoms in a disordered PEt3 ethyl group in 11 (C31K31A and C32lC32A) and one carbon atom in a disordered PEt3 methyl group in 12 (C26K26B); these disordered atoms were refined isotropically. The metal-bound hydrogen atom (H) and the hydrogen atom on C3 (H3) in 10 were refined isotropically, while all other hydrogens in 10, 11, and 12 (except those on disordered PEt3 carbons) were placed at idealized positions and assumed the riding model. In each case, a common isotropic U value for all hydrogens was refined.
Acknowledgment. We thank the National Science Foundation (Grants CHE-9003159 and CHE-9303516) and the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research. A loan of IrCly3Hz0 from Johnson-Matthey AlfdAesar is gratefully acknowledged. Washington University’s X-ray Crystallography Facility was funded by the National Science Foundation’s Chemical Instrumentation Program (Grant CHE-8811456). The High Resolution NMR Service Facility was funded in part by National Institutes of Health Biomedical Support Instrument Grant 1S10 RR02004 and by a gift from the Monsanto Company. Supporting InformationAvailable: Tables of structure determination summaries, final atomic coordinates, thermal parameters, bond lengths, and bond angles for compounds 1012 (25 pages). Ordering information is given on any current masthead page. OM950494M
