ARTICLE pubs.acs.org/Organometallics
j1- and j2-Complexes of FluorenylideneAllenyl Phosphines and Phosphine Oxides with Palladium Chloride and Iron Carbonyl: Displacement of Trimethylsilyl by Diphenylphosphino via a Stabilized Carbanion Sandra Milosevic, Emilie V. Banide, Helge M€uller-Bunz, Declan G. Gilheany, and Michael J. McGlinchey* School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
bS Supporting Information ABSTRACT: An attempt to prepare 3,3-(biphenyl-2,20 -diyl)-1diphenylphosphino-1-(trimethylsilyl)allene, 15, by treatment of 3,3-(biphenyl-2,20 -diyl)-1-lithio-1-(trimethylsilyl)allene with chlorodiphenylphosphine led instead to 3,3-(biphenyl-2,20 diyl)-1,1-bis(diphenylphosphino)allene, 14. The proposed mechanism invokes attack on the trimethylsilyl group in 15 by liberated chloride to form a stabilized anion that reacts with a second molecule of the chlorophosphine. The diphosphine, 14, reacts with di-iron nonacarbonyl to form monodentate 14-Fe(CO)4 and the chelate 14-Fe(CO)3. 9-Ethynyl-9H-fluoren-9-ol and chlorodiphenylphosphine form 3,3-(biphenyl-2,20 -diyl)-1-diphenylphosphinylallene, which is readily deprotonated by triethylamine to generate a stabilized fluorenyl anion, which reacts with a second molecule of the chlorophosphine to furnish 3,3-(biphenyl2,20 -diyl)-1-diphenylphosphino-1-diphenylphosphinylallene, 26. This bis-phosphine-monoxide (BPMO) reacts with di-iron nonacarbonyl to form initially monodentate P-bonded 26-Fe(CO)4, which loses a carbonyl, allowing the adjacent allene double bond in 26-Fe(CO)3 to coordinate to iron and leave the phosphine oxide uncoordinated. In contrast, the BPMO, 26, and (PhCN)2PdCl2 yield the phosphine-coordinated, chlorine-bridged dimer 34 and also the chelate 35, in which the palladium is linked to both the diphenylphosphino and diphenylphosphinyl groups via phosphorus and oxygen, respectively. Surprisingly, chlorodiphenylphosphine and 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne, 37, do not yield the expected 3,4-bis(phosphinyl)hexa1,2,4,5-tetraene, 33, but rather the 1-chloro-2-diphenylphosphinocyclobutene, 38, bearing a spiro-bonded fluorenylidene and a fluorenylidene-allene. All new compounds were characterized by 31P NMR spectroscopy and X-ray crystallography.
’ INTRODUCTION Our recent studies on the mechanism of formation of electroluminescent tetracenes from fluorenylidene-containing allenes, 1, revealed the sequential generation of a series of dimers.1 The initially formed head-to-tail dimers, 2, when thermolyzed, yielded C2 -symmetric 1,2-di(fluorenylidene)cyclobutanes, 3 and 4 (Scheme 1).2 In these tail-to-tail dimers, the very large wingspan (∼8.8 Å) of the overlapping fluorenylidenes results in their conrotation out of the plane of the cyclobutane. Moreover, the helical sense of the trans-oriented substituents at C(3) and C(4) can parallel that of the fluorenylidenes, as in 3, or oppose it, as in the thermodynamically favored diastereomer, 4. In those cases that we have characterized by X-ray crystallography, the dihedral angle between the fluorenylidene planes is noticeably larger in the latter case: for example, in 3 and 4 (R = Ph) these angles are 41° and 60°, respectively.1c There is enormous current interest in the use of enantiomerically pure C2-symmetric diphosphines as components of catalysts for asymmetric synthesis3 (BINAP4 being a classic example), and one of our goals is to prepare a series of such systems whereby the positioning of the two phosphine centers is controlled by the degree of overlap between fluorenylidenes, or other related r 2011 American Chemical Society
moieties possessing large wingspans, such as dibenzosuberenylidenes.5 In particular, we have focused on devising syntheses of fluorenylidene-containing allenyl-phosphines, 5, with the potential to form dimers, 6 (as in Scheme 2), structurally analogous to the 1,2-di(fluorenylidene)cyclobutanes, 3 and 4. The initially chosen molecule, 7, was readily prepared from the precursor bromoallene by lithiation and subsequent treatment with chlorodiphenylphosphine.6 However, the allenylphosphine 7 could not be induced to dimerize, presumably for steric reasons. Nevertheless, 7 did furnish a novel, and in some cases surprising, series of complexes, typified by molecules 811 in Scheme 3, with chromium and iron carbonyls, and with gold and ruthenium chlorides.6 Consequently, we chose to investigate allenylphosphines bearing less sterically demanding substituents, and we here describe our observations.
’ RESULTS AND DISCUSSION With the aim of preparing the minimally substituted fluorenylidene-containing allenylphosphine, 12 (Scheme 4), Received: April 27, 2011 Published: June 29, 2011 3804
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Scheme 1. Synthetic Route to Tetracenes via Allene Dimers
3,3-(biphenyl-2,20 -diyl)-1-bromo-1-(trimethylsilyl)allene, 13, was treated consecutively with n-butyllithium and chlorodiphenylphosphine. The product isolated in 50% yield after chromatographic separation was identified as the diphosphine 14, on the basis of its 1H, 13C, and 31P NMR spectra, in conjunction with microanalytical data. The 31P resonance at 2.9 ppm is in the normal range for a tertiary diphenylphosphino moiety (see Table 1), and the 13C spectrum of 14 (see Figure 1) exhibits 1:2:1 triplets at 105.4 (1JPC = 40 Hz C(11)), 207.2 (2JPC = 1.7 Hz C(10)), and 105.2 ppm (3JPC = 2.5 Hz C(9)), clearly indicating the presence of two magnetically equivalent phosphino substituents. It is, of course, well established that multiple phosphino groups can be introduced into the allene skeleton; repeated lithiation and addition of Ph2PCl to Ph2PCtCCH3 ultimately furnishes tetrakis(diphenylphosphino)allene.7 Nevertheless, in the present case a different mechanism appears to be operating. As depicted in Scheme 4, the initial product is presumably the silyl-phosphino allene 15, which then suffers attack at silicon by the liberated chloride to generate Me3SiCl and the fluorenidestabilized anion 16; subsequent reaction with a second molecule of chlorodiphenylphosphine yields the observed diphosphine 14. The crucial factor appears to be the enhanced carbanion stability provided by delocalization of the negative charge onto the fluorenyl framework, thus generating a 14π aromatic system. As depicted in Scheme 5, the diphosphine 14 reacted with diiron nonacarbonyl to form two products: the tetracarbonyliron complex 17, whose 31P NMR spectrum exhibited 106 Hz doublets at 5.9 ppm (noncomplexed phosphorus) and at 80.5 ppm (Fe-PPh2), closely analogous to the data previously found for 10 (Fe-PPh2 at 79.8 ppm),6 and a second material, 18, that exhibited a 31P NMR singlet at 39.1 ppm, implying formation of a system with symmetry-equivalent phosphorus environments. The most closely analogous system of which we are aware involves the reaction of 1,1-bis(diphenylphosphino)ethene (dppee) with Fe(CO)5/Me3NO to form two products. It was found that [H2CdC(PPh2)2]Fe(CO)4, 19, exhibited 59 Hz doublets at 10.8 ppm (noncomplexed phosphorus) and at 79.7 ppm (Fe-PPh2) and subsequently decomposed with loss of a carbonyl to yield the chelate complex [k2-H2CdC(PPh2)2]Fe(CO)3, 20 (31P singlet at 41.5 ppm), which was unambiguously identified by X-ray crystallography.8 Moreover, when heated with di-iron nonacarbonyl, dppee behaves as a bridging ligand to
Scheme 2. Potential Dimerization of an Allenylphosphine
generate [μ2-H2CdC(PPh2)2]Fe2(CO)7, 21, which exhibits a 31 P NMR singlet at 68.4 ppm.9 These data support the assignment of the second product formed from diphosphine 14 and iron carbonyl as the chelate 18, analogous to 20, rather than the bridged system 21. A second approach to introducing a phosphorus-containing substituent into a fluorenylidene-allene involves treatment of a 9-alkynyl-9H-fluoren-9-ol with chlorodiphenylphosphine in the presence of triethylamine to neutralize the liberated hydrogen chloride. As shown in Scheme 6, the resulting [2,3] sigmatropic shift of the Ph2PO fragment provides the conventional route to allenyl phosphine oxides,10 which could be subsequently reduced to the corresponding allenylphosphines. When 9-ethynyl-9Hfluoren-9-ol, 22, was subjected to these conditions, two different products were formed, dependent on the quantity of added triethylamine. In the absence of excess Et3N, the desired product, 23, reacts with HCl to form the adduct 24, whose structure is shown in Figure 2. Mechanistically, it is most reasonable to postulate initial addition of chloride to 23; it has been reported that allenes bearing electron-withdrawing substituents, such as cyano or nitro, react directly with lithium chloride.11 In the present case, the intermediate anion 25 can be stabilized by the fluorenyl and/or the phosphinyl substituent, thus greatly facilitating addition of chloride. In contrast, when the triethylamine is in excess, the product is the allenyl bis-phosphine monoxide (BPMO) 26, whose structure is shown in Figure 3. Evidently, the phosphinylallene 23 is readily deprotonated to form the stabilized anion 27, which reacts with a second molecule of chlorodiphenylphosphine to yield 3,3-(biphenyl-2,20 -diyl)-1-diphenylphosphino-1-(diphenylphosphinyl)allene, 26, which exhibits 31P NMR resonances at 25.4 ppm (Ph2PdO) and 6.2 (Ph2P). As listed in Table 1, the 2JPP(O) value of 88 Hz in 26 matches almost exactly the 3805
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Scheme 3. Metal Complexes of the Allenylphosphine 7
Scheme 4. Proposed Mechanism for the Formation of Allenyldiphosphine 14
87 Hz coupling observed in the closely analogous system PhNCdC(PPh2)[P(O)Ph2], 28.12 Likewise, the 1JPC and 1JP(O)-C values of 52 and 90 Hz, respectively, in 26 compare well with the corresponding coupling constants of 50 and 105 Hz in 28. The sensitivity of the unsubstituted allenylphosphine oxide 23 toward either chloride ion or triethylamine has thus far not allowed its isolation, and attempts to trap the liberated HCl without using an organic base are continuing. We note also that treatment of the BPMO 26 with sulfur yields the corresponding phosphine oxidephosphine sulfide 29 (Scheme 6). Bis-phosphine monoxides are of considerable current interest because of their ability to function as hemilabile ligands that contain both soft (P) and hard (O) Lewis base centers in the same molecule and to stabilize a range of transition metals in low and high oxidation states. Moreover, BPMOs often form labile chelates whereby a metal can be firmly bonded to one atom but rather weakly attached to a second, thus allowing the reversible generation of a vacant coordination site appropriate for catalytic activity.13 In addition, several allenylphosphine oxides have exhibited antitumor activity and other interesting applications in DNA cleavage.14 Currently used synthetic methods to form
BPMOs generally involve either a specific mono-oxidation of a diphosphine13 or deprotonation of a phosphine oxide possessing an acidic hydrogen with an alkyllithium and subsequent treatment with a chlorophosphine, as in Scheme 7.15 In effect, this present approach is a modification of the latter route whereby even a relatively weak base, such as triethylamine, serves to deprotonate the initially generated phosphine oxide. The anion so formed is particularly favored because it can be stabilized as an aromatic 14π fluorenide system. As noted above, the fluorenylidene-containing allenyl-monophosphine 7 reacts with iron carbonyl to yield initially the iron tetracarbonyl complex 10, which is very thermally sensitive and readily loses a carbonyl, thus allowing the adjacent allene double bond to coordinate to the newly available vacant site, as in 11. Likewise, the initial product of the reaction of the BPMO, 26, with di-iron nonacarbonyl is the tetracarbonyl complex 30, in which the Fe(CO)4 moiety is bonded to the diphenylphosphino substituent (Scheme 8). As in 10, the Fe(CO)4 fragment in 30 is fluxional, and the 13CO NMR absorption is a 31P-coupled single resonance. The 31P NMR spectrum of 30 exhibits peaks at 80.4 ppm for the Fe-PPh2 moiety and at 24.8 for the phosphinyl 3806
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Organometallics Table 1.
a
31
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P NMR Data for Fluorenylidene-Containing Allenes and Related Moleculesabc
This work. b Ph2PdS at 42.5 ppm. c Grim, S. O.; Walton, E. D. Inorg. Chem. 1980, 19, 19821987.
Figure 1. Section of the 101 MHz 13C NMR spectrum of 14 showing the allenic carbons.
substituent, with a 2JPP value of 10.6 Hz. Furthermore, there is facile loss of a carbonyl ligand with concomitant formation of a bond from the adjacent allene-double bond to Fe(CO)3 in 31 (rather than a Ph2PdOfFe(CO)3 linkage, as in 32). The phosphinyl 31P NMR resonance is almost unchanged at 24.3 ppm, but the Ph2PFe absorption is now seen at 15.5 ppm, similar to the chemical shift previously found in 11 (12.5 ppm); 2JPP is now 6.5 Hz. In 31, as with 11, the tricarbonyliron moiety is
nonrotating on the NMR time scale and so exhibits three 13CO NMR resonances, each with a different coupling constant to phosphorus: δ(CO) = 211.8, 209.8, and 209.4, 2J(31P13C) = 15.7, 28.5, and 23.2 Hz, respectively. Because of a minor crystallographic disorder, the only available crystals of 31 were not ideal, and so we cannot claim precise geometric parameters; however, the atom connectivity shown in Figure 4 is quite definitive. Interestingly, the preferential bonding of an Fe(CO)2 moiety to the adjacent double bond of an allene rather than formation of a diphosphine chelate has also been observed by Wojcicki.16 The reaction of 26 with iron carbonyl also revealed a minor side-product, 33, in very low yield, but sufficient to furnish an X-ray quality crystal whose structure appears in Figure 5. Molecule 33 was characterized as s-trans-1,6-bis(biphenyl-2,20 -diyl)-3,4bis(diphenylphosphinyl)-1,2,4,5-hexatetraene, in which the allenic double bonds, C(9)dC(10) and C(10)dC(11), are not significantly different, with values of 1.312(2) and 1.310(2) Å, respectively. This contrasts with the situation previously found in the closely analogous system trans-1,6-bis(biphenyl-2,20 -diyl)-3,4bis(trimethylsilyl)-1,2,4,5-hexatetraene, whereby the corresponding 3807
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Scheme 5. Reactions of Allenyldiphosphine 14 and of dppee with Iron Carbonylsa
a 31
P NMR shifts are in parentheses.
Scheme 6. Reaction of the Allenylphosphine Oxide 23 with HCl or Et3N
Figure 2. Molecular structure of 1,1-(biphenyl-2,20 -diyl)-2-chloro3-(diphenylphosphinyl)propene, 24. Thermal ellipsoids are at 25%.
double bond distances are 1.318(2) and 1.306(2) Å.17 However, the central C(11)C(110 ) single bond length is almost identical in the two cases (1.493(3) vs 1.496(2) Å). One can only speculate about the source of 33, which may have arisen via
homolytic cleavage of the carbonphosphorus linkage in 30 or 31; subsequent dimerization would lead directly to the bis(phosphinyl)-bis(allene) skeleton. Presumably, the corresponding metal-containing product should be the phosphido-bridged dimer (OC)3Fe(μ-PPh2)2Fe(CO)3,18 but this was not detectable. It is relevant to note that the reaction of 1,1-bis(diphenylphosphino)ethene or bis(diphenylphosphino)methane with iron carbonyls also yields products derived from cleavage of carbon phosphorus bonds.9,19 Bis-phosphine monoxide complexes of palladium have been extensively studied, and their catalytic efficacy has been evaluated.20 Treatment of the BPMO 26 with bis(benzonitrile)palladium dichloride yields two products. The minor product is the [(k1-PBPMO)PdCl2]2 chloride-bridged dimer 34 (Figure 6), in which each PdCl2 fragment is bonded only to the diphenylphosphino group, and neither the allene double bond nor the phosphinyl substituent interacts with the metal centers. 31P NMR resonances are seen at 34.7 ppm for the PdP linkage and at 28.7 ppm for the noncoordinated phosphinyl unit with a 2JPP value of 19 Hz. The major product is the (k2-P,O-BPMO)PdCl2 3808
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Organometallics chelate 35, whose structure appears in Figure 7 and which exhibits peaks at 34.6 and 56.3 ppm for the FeP linkage and for the coordinated phosphinyl unit, respectively; the 2JPP value is now 70 Hz. In the chloride-bridged dimer 34, the PdCl distances range from 2.327 to 2.437 Å (bridging) and 2.2783(6) to 2.2825(6) Å (terminal); the PdP bond lengths are 2.2064(6) and 2.2169(6) Å, and the PdO linkages are 1.481(2) and 1.482(2) Å. These may
Figure 3. Molecular structure of 3,3-(biphenyl-2,20 -diyl)-1-diphenylphosphino-1-(diphenylphosphinyl)allene, 26. Thermal ellipsoids are at 20%.
Scheme 7. Conventional Route to Bis-phosphine-monoxides
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be compared to the somewhat longer corresponding values of 2.357(1) and 2.387(1) Å (terminal PdCl), 2.254(1) and 2.248(1) Å (PdP), and 1.476(3) and 1.467(4) (PdO) Å in cis-[(Me2P(O)-CH2-PMe2)2PdCl2 3 H2O], in which the phosphine oxides are also nonbonding.21 The structure of the chelate 35, compared to that of the dimer 34, reveals a number of interesting features. These include a lengthening of the Ph2PPd bond to 2.2246(5) Å, a noticeable shortening of the C(11)P(O) carbonphosphorus linkage from 1.842(3) Å to 1.804(2) Å, and, of course, the establishment of a PdO bond (2.086(1) Å) together with the lengthening of the PdO distance from 1.482(2) Å to 1.522(1) Å. The palladiumchlorine bonds are now markedly different such that the one trans to oxygen (2.2673(5) Å) is considerably shorter than the PdCl bond trans to phosphorus (2.3526(5) Å), as expected for a linkage trans to a relatively weak PdO bond. These data may be compared to those reported for (dppmO)Pd(Me)Cl, for which the PdP and PdO distances are 2.204(2) and 2.276(4) Å, respectively, the PdO linkage is 1.508(4) Å, and the PdCl bond trans to phosphorus is 2.378(2) Å. As with 35, the central carbonP(O)Ph2 bond (1.796(6) Å) is noticeably shorter than the carbonPPh2 distance (1.834(6) Å).22 The pattern of metalchlorine bond lengths in 35 also parallels that seen in other (k2-P,O-BPMO)MCl2 systems, M = Pd or Pt, whereby the longer bond is trans to the phosphine.23 Moreover, as illustrated in Figure 7, the asymmetric unit in 35 also contains a molecule of chloroform that exhibits bifurcated hydrogen bonding to both of the palladium-bonded chlorines. Returning to the original goal of preparing a 1,2-bis (fluorenylidene)-3,4-bis(phosphino)cyclobutane or -cyclobutene, we noted the report by Cai and Blackburn that the bis-allenyl-bisphosphine oxide 36 is claimed to undergo cyclization upon thermolysis (Scheme 9).24
Scheme 8. Metal Complexes of BPMO 26
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Figure 4. Structure of the (BPMO)Fe(CO)3 complex 31. Thermal ellipsoids are at 30%.
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Figure 7. Molecular structure of the (BPMO-k2-P,O)PdCl2 3 CHCl3 35. Thermal ellipsoids are at 50%. Selected distances (Å) and angles (deg): PdCl(1) 2.2673(5), PdCl(2) 2.3526(5), PdP(2) 2.2246(5), PdO 2.0858(12), P(1)O 1.5220(14), Cl(1)Pd(1)Cl(2) 92.7, OPdP(2) 90.6, OPdCl(1) 176.4, P(2)PdCl(2) 177.1, OPdCl(2) 89.1, P(2)PdCl(1) 87.7.
Scheme 9. Formation and Electrocyclization of 1,1,6,6-Tetramethyl-3,4-bis(diethoxyphosphinyl)-1,2,4,5-hexatetraene, 3624
Figure 5. Molecular structure of s-trans-1,6-bis(biphenyl-2,20 -diyl)-3,4bis(diphenylphosphinyl)-1,2,4,5-hexatetraene, 33. Thermal ellipsoids are at 50%.
Figure 6. Molecular structure of the [(BPMO)PdCl2]2 34. Thermal ellipsoids are at 50%. Selected distances (Å) and angles (deg): Pd(1) Cl(1) 2.2783(6), Pd(1)Cl(2) 2.3272(6), Pd(1)Cl(3) 2.4114(6), Pd(2)Cl(2) 2.4367(6), Pd(2)Cl(3) 2.3303(6), Pd(2)Cl(4) 2.2825(6), Pd(1)P(2) 2.2169(6), Pd(2)P(4) 2.2064(6), P(1)O(1) 1.482(2), P(3)O(2) 1.481(2), Cl(2)Pd(1)Cl(3) 91.4, Cl(2)Pd(2)Cl(3) 85.1, Pd(1)Cl(2)Pd(2) 92.8, Pd(1)Cl(3) Pd(2) 93.3, P(1)C(11)P(2) 118.9.
To this end, 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne, 37, was prepared in 33% yield by the reaction of butyllithium with hexachlorobutadiene with subsequent addition of fluorenone. This one-pot route to diynes25 is more convenient than the previously reported multistep palladium or copper coupling procedures.26 Surprisingly perhaps, the molecular structure of
the diyne-diol 37 has not previously been reported, and since we had crystals in hand, an X-ray study was undertaken. In fact, the molecule crystallizes both with and without DMSO. In the former case (Figure 8), each hydroxyl group is hydrogen-bonded to a molecule of the dimethyl sulfoxide solvent. In contrast, in the absence of DMSO, the diols give rise to an infinite lattice whereby the OH units from four different diyne-diol molecules form hydrogen-bonded square arrays, as illustrated in Figure 9. The O 3 3 3 O distances within these square arrays range from 2.69 to 2.72 Å, comparable to the values reported for other hydrogenbonded alkynol tetramers.27 In the DMSO solvate structure, there is a clear alternation of single and triple bonds—C(9)C(10) 1.472(2) Å, C(10)C(11) 1.206(2) Å, C(11)C(12) 1.370(3) Å, C(12)C(13) 1.204(3) Å, C(13)C(14) 1.481(2) Å—but the angles along the C(9) to C(14) chain are all ∼177°, such that the system is slightly bowed. In the expectation of developing a rational, high-yield route to trans-1,6-bis(biphenyl-2,20 -diyl)-3,4-bis(diphenylphosphinyl)1,2,4,5-hexatetraene, 33, the diyne-diol 37 was subjected to the 3810
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Organometallics normal reaction conditions (chlorodiphenylphosphine/triethylamine) for the conversion of an alkynol to an allenyl phosphine oxide, as exemplified in Scheme 6. Out of the multiplicity of products, one was isolated that appeared to contain an allenelinked fluorenylidene together with chloro and diphenylphosphinyl substituents. The structure was definitively identified by X-ray crystallography as 38, in which the Ph2PdO moiety was positioned between the chloro and spiro-fluorenylidene within a cyclobutene ring (Figure 10). Both fluorenyls are almost exactly orthogonal to the cyclobutene ring plane, in which the carboncarbon single-bond lengths vary quite substantially. The ClC(1)dC(2)P double bond is 1.352(2) Å, and the C(1) C(4) bond that connects the chlorine and allenyl substituents is 1.463(2) Å, but the other two single bonds, C(2)C(3) and C(3)C(4), are much longer at 1.565(2) and 1.569(2) Å, respectively. Moreover, in the allenyl fragment, the carbon carbon double bonds are also significantly different: C(4)C(5) 1.296(2) Å and C(5)C(6) 1.321(2) Å. The isolation of such a novel molecule poses an interesting mechanistic question. The most obvious proposal, an initial [2,3]
Figure 8. Molecular structure of 1,4-bis(9-hydroxy-9H-fluorenyl)buta1,3-diyne, 37 3 DMSO, showing hydrogen bonding to the solvent. Thermal ellipsoids are at 50%.
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sigmatropic rearrangement to yield the allenylphosphine oxide 39, with subsequent attack by chloride on cation 40 and electrocyclization of the cumulene 41, leads to the incorrect isomer, 42 (Scheme 10). Instead, one has to envisage formation of a fourmembered ring, 43, that suffers attack by chloride; Arbusov-type ring-opening furnishes the appropriate cumulene, 44, that, after bond rotation, is ideally poised for electrocyclization to the observed product, 38. We note that 1-phosphinylcyclobutene opens to the 2-phosphinyl-1,3-butadiene only at elevated temperatures to give DielsAlder adducts, thus demonstrating that the cyclic isomer is thermodynamically favored.28 Interestingly, 2,3-bis(diphenylphosphinyl)-1,3-butadiene favors the open chain form.29 In the context of Baldwin’s rules,30 formation of the allenylphosphine oxide 39 would occur via a 5-endo-dig process, whereas the route to the observed product 38, via 43, apparently requires the normally disfavored 4-exo-dig cyclization. However, the latter process has been observed in a number of cyclocarbopalladations;31 moreover, numerous exceptions to Baldwin’s rules are known for cationic and radical systems32 and especially for reactions in which a second-row element is included in the ring.33 Interestingly, a comprehensive study combining DFT calculations with Marcus theory indicated clearly that 4-exo-dig radical cyclizations are kinetically competitive with the 5-endo-dig process, but are less favorable thermodynamically.34 To conclude, attempts to synthesize 3,3-(biphenyl-2,20 -diyl)1-diphenylphosphinoallene, 12, and 3,3-(biphenyl-2,20 -diyl)-1diphenylphosphinylallene, 23, led instead to 3,3-(biphenyl-2, 20 -diyl)-1,1-bis(diphenylphosphino)allene, 14, and 3,3-(biphenyl2,20 -diyl)-1-diphenylphosphino-1-diphenylphosphinylallene, 26, respectively, in each case via an aromatic fluorenide-stabilized anion. These ligands react with iron carbonyl to form initially the phosphine-coordinated Fe(CO)4 complexes 17 and 30, respectively, which readily lose carbon monoxide. In the former case, the product is the chelate 18, whereas in the BPMO the Fe(CO)3 unit coordinates to the adjacent double bond of the allene rather than to the phosphinyl oxygen. However, the BPMO 26 and
Figure 9. Section of the packing motif of the solvent-free diyne-diol 37, showing the square arrays arising from the intermolecular hydrogen bonding between (OH)4 moieties. 3811
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Organometallics (PhCN)2PdCl2 yield the phosphine-coordinated, chlorinebridged dimer 34 and also the (k2-P,O-BPMO)PdCl2 chelate 35, in which the palladium is linked to both the diphenylphosphino and diphenylphosphinyl groups via phosphorus and oxygen, respectively. The catalytic potential of this system, which bears a hemilabile BPMO ligand, has yet to be explored. The bis-allene 3,4-bis(diphenylphosphinyl)hexa-1,2,4,5-tetraene, 33, a possible precursor to a cyclobutane-diphosphine with
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C2-symmetry resulting from overlapping substituents with large wingspans, is formed in very low yield, apparently by decomposition of 30, the monocoordinated Fe(CO)4 derivative of the BPMO 30. An attempted rational synthesis of 33 by reaction of chlorodiphenylphosphine and 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne, 37, did not yield the expected product, but rather the 1-chloro-2-diphenylphosphinocyclobutene 38, bearing a spiro-bonded fluorenylidene and a fluorenylidene-allene.
’ EXPERIMENTAL SECTION
Figure 10. Molecular structure of the cyclobutene 38.
General Methods. All reactions were carried under a nitrogen atmosphere, and solvents were dried by standard procedures. 1H, 13C, and 31P NMR spectra were recorded on Varian Inova 300 or 400 MHz or VNMRS 500 or 600 MHz spectrometers. Assignments were based on standard two-dimensional NMR techniques (1H1H COSY, 1H13C HSQC, HMBC, NOESY). Infrared spectra were recorded on a PerkinElmer Paragon 1000 FT-IR spectrometer and were calibrated with polystyrene. Electrospray mass spectrometry was performed on a Micromass Quattro microinstrument. Merck silica gel 60 (230400 mesh) was used for flash chromatography. Melting points were determined on an Electrothermal ENG instrument and are uncorrected.
Scheme 10. Proposed Mechanism for the Formation of Cyclobutene 38
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Organometallics Elemental analyses were carried out by the Microanalytical Laboratory at University College Dublin. 3,3-(Biphenyl-2,2 0 -diyl)-1-bromo-1trimethylsilylallene, 13, and 9-ethynyl-9H-fluoren-9-ol, 22, were prepared as previously described.2a
Synthesis of 3,3-(Biphenyl-2,20 -diyl)-1,1-bis(diphenylphosphino)allene (14). A solution of 3,3-(biphenyl-2,20 -diyl)-1-
bromo-1-trimethylsilylallene (876 mg, 2.57 mmol) in dry THF (12 mL) was added very slowly at 78 °C to a solution of nBuLi (1.76 mL, 1.6 M in hexane, 2.82 mmol) in dry THF (10 mL). After stirring for 10 min at 78 °C, chlorodiphenylphosphine (1.11 mL, 5.9 mmol) was slowly added. The mixture was allowed to warm slowly to room temperature and stirred overnight. After quenching with water and removing the solvent, the crude material was extracted three times with dichloromethane. The organic layers were combined, washed with water and brine, and dried over MgSO4, and the filtrate was concentrated to give a dark yellow oil. The oil was purified by chromatography on a silica column using dichloromethane/pentane as eluent to give 3,3-(biphenyl2,20 -diyl)-1,1-bis(diphenylphosphino)allene, 14 (712 mg, 1.27 mmol; 50%), as a white solid. 1H NMR (400 MHz, CDCl3): δ 7.617.58 (m, 2H), 7.517.46 (m, 8H), 7.267.13 (m, 18H). 13C NMR (101 MHz, CDCl3): δ 207.2 (t, 2JPC = 1.7 Hz, C10), 137.65, 137.64 (fluorenyl-C), 135.7 (t, J = 4.9 Hz, phenyl ipso-C), 134.0 (t, J = 10.7 Hz, phenyl o-C), 129.3 (phenyl p-C), 128.3 (t, J = 3.7 Hz, phenyl m-C), 127.2, 126.57, 122.61, 120.0 (fluorenyl-CH), 105.4 (t, 1JPC = 40.1 Hz, C11), 105.2 (t, 3JPC = 2.5 Hz, C9). 31P{1H} NMR (162 MHz, CDCl3): δ 2.9 (s, PPh2). IR (CH2Cl2): 1909 cm1 (CdCdC). Anal. Calcd for C39H28P2 3 0.5THF: C, 82.80; H, 5.43; P, 10.42. Found: C, 82.86; H, 5.24; P, 9.92.
Syntheses of [3,3-(Biphenyl-2,20 -diyl)-1,1-bis(diphenylphosphino)allene]-Fe(CO)4 (17) and -Fe(CO)3 (18). Diiron-nonacar-
bonyl (74 mg, 0.203 mmol) and 3,3-(biphenyl-2,20 -diyl)-1-bis(diphenylphosphine)allene, 37 (94 mg, 0.168 mmol), were dissolved in dry THF (9 mL) and stirred for 5 days at room temperature under a nitrogen atmosphere. The solvent was removed in vacuo, and the red residual solid was filtered through silica with ethyl acetate. Total conversion of the starting material into the major products 17 and 18 (ratio 5:2, respectively) was confirmed by 31P NMR. It was then purified by chromatography on a silica column using ethyl acetate/pentane, to yield 17 (23 mg, 0.032 mmol; 19%) and 18 (10 mg, 0.014 mmol; 8%) as very air-sensitive, yellow and red solids, respectively. Data for 17: 31 1 P{ H} NMR (162 MHz, CDCl3) δ 80.5 (d, J = 106, Ph2P-Fe(CO)4), 5.9 (d, J = 106 Hz, PPh2). Data for 18: 31P{1H} NMR (162 MHz, CDCl3) δ 39.1 (s, Ph2P-Fe(CO)3-PPh2).
Synthesis of 1,1-(Biphenyl-2,20 -diyl)-2-chloro-3-(diphenylphosphinyl)propene (24). Triethylamine (90 μL, 0.63 mmol) was
added to a solution of 9-ethynyl-9H-fluoren-9-ol (100 mg, 0.49 mmol) in dry dichloromethane (10 mL) at room temperature. Chlorodiphenylphosphine (100 μL, 0.54 mmol) was then added slowly, and after stirring at room temperature for 2.5 h, water was poured onto the yellow mixture. The solution was extracted twice with dichloromethane, and the organic layers were combined, washed with water and brine, dried over MgSO4, filtered, and concentrated to give a green-yellow oil. The oil was purified by chromatography on a silica column using dichloromethane/ethyl acetate as eluent to give 1,2-(biphenyl-2,20 -diyl)-2chloro-3-(diphenylphosphinyl)propene, 24 (66 mg, 0.16 mmol; 32%), as a white powder, mp 180.5181.5 °C, and recovered 9-ethynyl-9Hfluoren-9-ol (40 mg, 0.19 mmol; 40%). A sample of 24 suitable for an X-ray crystal structure determination was obtained by recrystallization from dichloromethane/pentane. 1H NMR (500 MHz, CDCl3): δ 8.35 (d, 1H, J = 8.0 Hz), 7.91 (d, 1H, J = 8.0 Hz), 7.907.85 (m, 4H), 7.66 (d, 1H, J = 7.5 Hz), 7.64 (d, 1H, J = 7.5 Hz), 7.557.51 (m, 2H), 7.487.4 (m, 4H), 7.34 (t, 1H, J = 7.5 Hz), 7.31 (t, 1H, J = 7.5 Hz), 7.25 (t, 1H, J = 7.5 Hz), 7.20 (t, 1H, J = 7.5 Hz), 4.33 (d, 2H, 2JPH = 14.7 Hz). 31P NMR (121 MHz, CDCl3): δ 27.9 (t, 2JPH = 13 Hz). Anal. Calcd for
ARTICLE
C27H20POCl 3 0.5CH3CO2C2H5: C, 73.96; H, 5.14. Found: C, 74.45; H, 5.31.
Synthesis of 3,3-(Biphenyl-2,2 0 -diyl)-1-(diphenylphosphino)-1-(diphenylphosphinyl)allene (26). Triethylamine (620 μL,
4.45 mmol) was added to a solution of 9-ethynyl-9H-fluoren-9-ol (420 mg, 2.04 mmol) in dry dichloromethane (4 mL) and pentane (21 mL). Chlorodiphenylphosphine (820 μL, 4.44 mmol) was then added slowly at 0 °C and stirred for 15 min. After stirring for 1 h at room temperature, the mixture was extracted twice with dichloromethane, and the organic layers were combined, washed with water and brine, dried over MgSO4, filtered, and concentrated to give an orange oil, which was purified by chromatography on a silica column using pentane/ethyl acetate as eluent to give 3,3-(biphenyl-2,20 -diyl)-1-(diphenylphosphino)-1-(diphenylphosphinyl)allene, 26 (945 mg, 1.64 mmol; 81%), as a white powder. A sample of 26 suitable for an X-ray crystal structure determination was obtained by recrystallization from ethyl acetate/pentane. 1H NMR (500 MHz, CDCl3): δ 7.81 (dd, J = 7.1 Hz, J = 1.2 Hz, 2H), 7.79 (dd, J = 7.1 Hz, J = 1.2 Hz, 2H), 7.59 (d, J = 7.5 Hz, 2H), 7.44 (dt, J = 7.9 Hz, J = 1.2 Hz, 4H), 7.40 (td, J = 7.3 Hz, J = 1.3 Hz, 2H), 7.31 (t, J = 7.5 Hz, 2H), 7.30 (t, J = 7.5 Hz, 2H), 7.26 (t, J = 7.4 Hz, 2H), 7.197.08 (m, 10H). 13C NMR (125 MHz, CDCl3): δ 210.9 (t, 2J CP = 2.1 Hz, C10), 138.1 (d, J = 0.7 Hz, ipso-Ph), 136.5 (d, J = 5.8 Hz, ipso-Ph), 135.3 (dd, J = 15.1 Hz, J = 4.3 Hz, ipso-Ph), 134.0 (s, 2 aromatic CH), 133.8 (s, 2 aromatic CH), 133.0, 132.2 (C4a, C4b, C8a, C9a), 132.1 (d, J = 2.9 Hz, 2 aromatic CH), 131.8 (s, 2 aromatic CH), 131.6 (s, 2 aromatic CH), 129.3 (s, 2 aromatic CH), 128.5 (s, 2 aromatic CH), 128.4 (d, J = 2.7 Hz, 4 aromatic CH), 128.3 (s, 2 aromatic CH), 128.1 (d, J = 1.0 Hz, 2 aromatic CH), 126.9 (d, J = 0.8 Hz, 2 aromatic CH), 123.0 (d, J = 1.5 Hz, 2 aromatic CH), 120.3 (s, J = 0.6 Hz, 2 aromatic CH), 106.4 (dd, 1JCP = 90.3 and 51.7 Hz, C11), 106.3 (dd, 3JCP = 12.7 and 1.3 Hz, C9). 31P NMR (121 MHz, CDCl3): δ 25.4 (dp, 2JPP = 88.0 Hz, 3 JPH = 12.5 Hz, P(O)Ph2), 6.2 (dp, 2JPP = 88.0 Hz, 3JPH = 8.0 Hz, PPh2). IR (CH2Cl2): 1916 (CdCdC), 1263 cm1 (PdO). ESMS: calcd for C39H29OP2 [M + H+], 575.19; found 575.15. Anal. Calcd for C39H28OP2 3 0.5CH3CO2C2H5: C, 79.60; H, 5.21. Found: C, 79.74; H, 5.40.
Synthesis of 3,3-(Biphenyl-2,20 -diyl)-1-(diphenylphosphinyl)-1-(diphenylthiophosphinyl)allene (29). The BPMO 26
(84 mg, 0.146 mmol) and sulfur (375 mg, 1.46 mmol) were stirred in dry toluene (13 mL) at room temperature for 46 h under a nitrogen atmosphere. The solvent was removed under vacuum, and the yellow residue was purified by column chromatography using ethyl acetate/ pentane as eluent to give 29 (85 mg, 0.140 mmol; 96%) as a beige powder. 1H NMR (400 MHz, CDCl3): δ 8.00 (d, J = 7.0 Hz, 2H), 7.96 (d, J = 7.1 Hz, 2H), 7.77 (d, J = 7.2 Hz, 2H), 7.74 (d, J = 7.3 Hz, 2H), 7.55 (d, J = 7.3 Hz, 2H), 7.377.31 (m, 4H), 7.317.22 (m, 12H), 7.19 (td, J = 7.5 Hz, J = 0.9 Hz, 2H). 31P{1H} NMR (162 MHz, CDCl3): δ 42.5 (d, 2JPP = 24.0 Hz, P(S)Ph2), 25.6 (d, J = 24.0 Hz, P(O)Ph2). ESMS: calcd for C39H29OSP2 [M + H+], 607.16; found 607.12. IR (CH2Cl2): 1919 (CdCdC), 1259 cm1 (PdO). Reaction of BPMO 26 with Fe2(CO)9. Diiron-nonacarbonyl (192 mg, 0.653 mmol) and the BPMO 26 (125 mg, 0.218 mmol) were dissolved in dry THF (8 mL) and stirred for 7 days at room temperature under a nitrogen atmosphere. Total conversion of the starting material into 30 and 31 (ratio 85:15, respectively) was confirmed by 31P NMR. The solvent was removed in vacuo, and the red-green residual solid was filtered through silica with ethyl acetate. It was then purified by chromatography on a silica column using ethyl acetate/pentane to yield 30 (39 mg, 0.053 mmol; 24%) as a yellow solid and 31 (11 mg, 0.015 mmol; 7%) as an orange solid. In the solid state, the tetracarbonyl complex 30 is stable below 0 °C; however, when dissolved in CDCl3 at room temperature, 30 rapidly evolved into 31. Moreover, when an NMR sample containing a mixture of 30 and 31 was left for several days, it yielded a small quantity of trans-1,6-bis(biphenyl-2,20 -diyl)-3,4-bis(diphenylphosphinyl)-1,2,4,5-hexatetraene, 33, as colorless crystals. Samples of 31 and 33 suitable for X-ray crystal structure determinations 3813
dx.doi.org/10.1021/om200357v |Organometallics 2011, 30, 3804–3817
Organometallics
ARTICLE
Table 2. Crystallographic Data for 24, 26, 31, 33, and 34 24
26
31
33
34
formula
C27H20OClP
C39H28O1.06P2
C42H28FeO4P2
C54H36O2P2 3 2CHCl3
(C78H56O2P4Cl4Pd2)2 3 5CHCl3
M
426.85
575.45
714.43
1017.50
3604.26
cryst syst
monoclinic
monoclinic
triclinic
monoclinic
triclinic
space group
C2/c (#15)
C2/c (#15)
P1 (#2)
P21/c (#14)
P1 (#2)
a [Å]
42.332(4)
18.3202(16)
10.7362(11)
9.7769(9)
10.4539(3)
b [Å]
5.5148(5)
10.6458(9)
10.7918(11)
12.4243(12)
12.5942(3)
c [Å]
41.938(4)
16.8451(14)
16.2959(17)
19.6343(18)
29.1459(7)
R [deg] β [deg]
90 120.266(2)
90 111.483(2)
100.162(3) 106.620(3)
90 93.615(2)
84.129(2) 87.199(2)
γ [deg]
90
90
104.711(3)
90
81.094(2)
V [Å3]
8455.9(14)
3057.1(5)
1685.5(3)
2380.3(4)
3769.03(17)
Z
16
4
2
2
1
Fcalcd [g cm3]
1.341
1.250
1.408
1.420
1.588
T [K]
293(2)
293(2)
100(2)
100(2)
100(2)
μ [mm1]
0.273
0.173
0.586
0.472
8.785
F(000) θ range for data collection [deg]
3552 1.11 to 21.15
1201.6 2.37 to 26.42
736 1.35 to 20.85
1044 2.08 to 26.47
1810 3.57 to 76.97
index ranges
42 e h e 42
22 e h e 22
10 e h e 10
12 e h e 12
13 e h e 13
5 e k e 5
13 e k e 13
10 e k e 10
15 e k e 15
15 e k e 15
42 e l e 41
21 e l e 21
16 e l e 16
24 e l e 24
36 e l e 36
reflns measd
21 460
26 395
7958
41 568
75 669
indep reflns
4616
3117
3538
4879
15 282
Rint
0.0331
0.0423
0.0323
0.0386
0.0447
data/restraints/params final R values [I > 2θ(I)]:
4616/166/541
3117/46/252
3559/0/495
4879/3/387a
15 282/0/919
R1
0.0429
0.0448
0.0827
0.0369
0.0310
wR2
0.0952
0.1177
0.1702
0.0910
0.0805
R1
0.0515
0.0476
0.0906
0.0424
0.0385
wR2
0.0997
0.1194
0.1745
0.0945
0.0830
GOF on F2
1.091
1.130
1.199
1.037
1.064
R values (all data):
a
The minor disorder part of the solvent was restrained to be regular using SADI.
were obtained by recrystallization from chloroform. Data for 30: 1H NMR (300 MHz, CDCl3): δ 7.967.85 (m, 4H), 7.687.57 (m, 6H), 7.38 7.27 (m, 10H), 7.237.11 (m, 8H). 13C NMR (101 MHz, CDCl3): δ 216.7 (C10), 213.2 (d, J = 18.2 Hz, 3 CO), 138.6 (C4a, C4b), 135.6 (dd, J = 10.8 and 5.1 Hz, C8a, C9a), 133.8, 133.7, 133.2 (d, J = 11.6 Hz), 133.1, 132.6 (d, J = 3.2 Hz), 131.9 (d, J = 1.8 Hz), 131.5 (dd, J = 16.9 Hz, J = 8.3 Hz), 131.2, 131.2, 131.1, 131.1, 128.9, 128.3, 128.3, 128.2, 128.2, 127.3, 124.0, 120.4, 109.4 (pseudo t, J = 12.5 Hz, C9), 106.6 (dd, J = 74.5 and 21.2 Hz, C11). 31P{1H} NMR (162 MHz, CDCl3): δ 80.4 (d, J = 10.5 Hz, PPh2), 24.8 (d, J = 10.6 Hz, P(O)Ph2). IR (CH2Cl2): 2047, 1978, 1933 (CtO), 1280 cm1 (PdO). Data for 31: 1H NMR (500 MHz, CDCl3): δ 8.15 (d, J = 7.6 Hz, 1H), 8.11 (d, J = 7.0 Hz, 1H), 8.06 (d, J = 7.9 Hz, 1H), 8.04 (d, J = 7.5 Hz, 1H), 7.867.77 (m, 1H), 7.71 (d, J = 7.3 Hz, 1H), 7.69 (d, J = 7.6 Hz, 1H), 7.64 (d, J = 7.7 Hz, 2H), 7.62 (d, J = 7.7 Hz, 1H), 7.53 (d, J = 7.2 Hz, 1H), 7.50 (d, J = 7.4 Hz, 1H), 7.48 (d, J = 8.7 Hz, 2H), 7.36 (td, J = 7.9 Hz, J = 2.9 Hz, 2H), 7.32 (t, J = 7.5 Hz, 2H), 7.22 (t, J = 7.5 Hz, 1H), 7.177.06 (m, 7H), 6.95 (td, J = 7.8 Hz, J = 3.3 Hz, 2H). 13C NMR (126 MHz, CDCl3): δ 211.8 (d, J = 15.7 Hz, CO), 209.8 (d, J = 28.5 Hz, CO), 209.4 (d, J = 23.2 Hz, CO), 159.5 (dd, J = 13.5 Hz, J = 5.6 Hz, C10), 140.1, 139.7 (d, J = 4.4 Hz), 137.0 (d, J = 6.0 Hz), 136.5 (C4a, C4b, C8a, C9a), 135.6 (d, J = 11.4 Hz), 133.5, 133.2 (d, J = 11.4 Hz), 132.6, 132.4 (d, J = 3.0 Hz), 132.3 (d, J = 9.0 Hz), 131.9, 131.7 (d, J = 2.0 Hz), 131.5 (d, J = 2.0 Hz), 131.4 (d, J = 2.0 Hz), 131.2 (d, J = 9.0 Hz), 131.1,
128.8 (d, J = 12.3 Hz), 128.6 (d, J = 12.3 Hz), 128.1 (d, J = 12.3 Hz), 127.8 (d, J = 12.3 Hz), 126.6, 126.4, 126.3, 126.2, 126.1, 126.0, 125.4, 124.9 (d, J = 11.5 Hz), 124.6, 124.1, 123.4, 121.6, 119.4, 118.8 (C1, C4, C5, C8), 31.8 (dd, J = 60.5 Hz, J = 51.8 Hz, C11). 31P{1H} NMR (162 MHz, CDCl3): δ 24.3 (d, J = 6.5 Hz, P(O)Ph2), 15.5 (d, J = 6.5 Hz, PPh2). IR (CH2Cl2): 2047, 1980 (CtO), 1263 cm1 (PdO). Reaction of BPMO 26 with (PhCN)2PdCl2. To a solution of BPMO 26 (99 mg, 0.174 mmol) in dry dichloromethane (8 mL) was added at once solid dichlorobis(benzonitrile)palladium(II) (66 mg, 0.174 mmol). After stirring the mixture for 1 h at room temperature, the volatiles were removed. The orange-yellow residue was washed with a small amount of ether and then pentane to give 35 (101 mg, 0.133 mmol; 76%) as a shiny orange powder. It slowly decomposed to yield the dimer 34 (25 mg, 0.017 mmol; 19%) as a yellow-orange powder. Samples of 34 and 35 suitable for X-ray crystal structure determinations were obtained by recrystallization from chloroform. Data for 34: 31P{1H} NMR (162 MHz, CDCl3): δ 34.7 (pseudo t, J = 19 Hz, PPh2), 28.7 (pseudo t, J = 19 Hz, P(O)Ph2). IR (liquid, CH2Cl2): 1920 cm1 (CdCdC). Anal. Calcd for C78H56Cl4O2P4Pd2 3 CHCl3: C, 58.46; H, 3.54. Found: C, 58.95; H, 3.40. Data for 35: 31P{1H} NMR (162 MHz, CDCl3): δ 56.3 (d, J = 70 Hz, P(O)Ph2), 34.6 (d, J = 70.0 Hz, PPh2). IR (CH2Cl2): 1921 cm1 (CdCdC). Anal. Calcd for C39H28Cl2OP2Pd 3 CHCl3: C, 55.14; H, 3.35. Found: C, 55.62; H, 3.73. 3814
dx.doi.org/10.1021/om200357v |Organometallics 2011, 30, 3804–3817
Organometallics
ARTICLE
Table 3. Crystallographic Data for 35, 37, 37 3 DMSO, and 38 35
37 3 DMSO
37
38
formula
C39H28OP2Cl2Pd 3 2CHCl3
C30H18O2
2(C30H18O2) 3 5(CH3)2SO
C42H26OPCl
M
990.59
410.44
1211.53
613.05
cryst syst
monoclinic
triclinic
orthorhombic
triclinic
space group
P21/n (#14)
P1 (#2)
Pca21 (#29)
P1 (#2)
a [Å]
9.4807(3)
11.5523(4)
24.2699(1)
9.8854(4)
b [Å]
14.3847(4)
11.9264(4)
8.90511(6)
12.6342(7)
c [Å]
30.6171(9)
17.1040(6)
29.1073(2)
13.3036(6)
R [deg] β [deg]
90 97.547(3)
104.621(3) 98.828(3)
90 90
84.502(4) 78.088(4)
γ [deg]
90
101.907(3)
90
69.495(5)
V [Å3]
4139.3(2)
2177.95(13)
6290.85(7)
1522.26(12)
Z
4
4
4
2
Fcalcd [g cm3]
1.590
1.252
1.279
1.337
T [K]
100(2)
160(2)
100(2)
100(2)
μ [mm1]
1.075
0.609
2.157
0.213
F(000) θ range for data collection [deg]
1984 3.45 to 29.60
856 3.96 to 65.00
2552 3.64 to 76.47
636 3.41 to 30.00
index ranges
13 e h e 12
10 e h e 13
30 e h e 30
13 e h e 13
19 e k e 19
13 e k e 14
7 e k e 10
17 e k e 15
41 e l e 39
20 e l e 18
36 e l e 30
17 e l e 18
reflns measd
40 627
14 998
35 889
18 428
indep reflns
10 330
7399
10 869
8854
Rint
0.0363
0.0207
0.0243
0.0307
data/restraints/params final R values [I > 2θ(I)]:
10 330/0/478
7399/0/593
10 869/10/828
8854/0/406
R1
0.0307
0.0355
0.0321
0.0406
wR2
0.0707
0.0901
0.0843
0.1086
R1
0.0433
0.0456
0.0331
0.0529
wR2
0.0737
0.0959
0.0850
0.1126
GOF on F2
1.069
1.046
1.055
1.081
R values (all data):
Synthesis of 1,4-Bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne (37). nBuLi (19 mL, 30 mmol) was added dropwise onto a solution of hexachlorobutadiene (1.95 g, 7.44 mmol) in dry THF (30 mL) at 78 °C, turning the solution black immediately. After stirring at 80 to 60 °C for 1.5 h, the solution was cooled again to 78 °C, and a solution of fluorenone (2.81 g, 15.6 mmol) in dry THF (2 10 mL) was added dropwise over 20 min. The black-yellow solution was allowed to warm slowly to room temperature overnight. After stirring for 40 h at room temperature, the solution was concentrated, then extracted with ether several times. The ethereal fractions were combined, washed with water and brine, dried over MgSO4, filtered, and concentrated to yield a beige solid. This was purified by chromatography on a silica gel column using dichloromethane as eluent to recover the excess fluorenone and then with pentane/ethyl acetate/methanol (12:8:1) as the second eluent to give 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne, 59 (1.01 g, 2.46 mmol; 33%), as a white solid. Samples of 37 and 37 3 DMSO suitable for X-ray crystal structure determinations were obtained by recrystallization from chloroform and dimethylsulfoxide, respectively. Data for 37: 1H NMR (500 MHz, DMSO-d6): δ 7.77 (d, 4H, J = 7.5 Hz), 7.61 (d, 4H, J = 7.5 Hz), 7.42 (td, 4H, J = 7.5 Hz, J = 1.0 Hz), 7.34 (td, 4H, J = 7.5 Hz, J = 1.0 Hz), 6.84 (s, 2H, OH). 1H NMR (500 MHz, CDCl3): δ 7.64 (d, 4H, J = 7.5 Hz), 7.60 (d, 4H, J = 7.5 Hz), 7.39 (td, 4H, J = 7.5 Hz, J = 1.0 Hz), 7.32 (td, 4H, J = 7.5 Hz, J = 1.0 Hz), 2.49 (s, 2H, OH). 13C NMR (126 MHz, CDCl3): δ 146.1, 139.3 (C4a, C4b, C8a, C9a), 130.2, 128.8,
124.5, 120.5 (fluorenyl CH), 79.5 (C10, C11), 67.4 (C9). ESMS: calcd for C30H17O [M + H H2O+], 393.12; found 393.12; calcd for [M + Na+], 433.12; found 433.10. Synthesis of Cyclobutene (38). Triethylamine (180 μL, 1.29 mmol) and 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne (182 mg, 0.443 mmol) were suspended in dry dichloromethane (12 mL) and cooled to 50 °C. Chlorodiphenylphosphine (240 μL, 1.29 mmol) was then added slowly, and the orange mixture was stirred for 15 min at 40 °C, then slowly warmed to room temperature overnight. After stirring for 15 h at room temperature, the mixture was quenched with sodium bicarbonate, washed with water and brine, dried over MgSO4, filtered, and concentrated to give a dark red-purple solid. It was purified by chromatography on a silica column using pentane/ethyl acetate as eluent to give the cyclobutene 38 (10 mg, 0.016 mmol; 4%) as a white powder. A sample suitable for an X-ray crystal structure determination was obtained by recrystallization from ethyl acetate/pentane. 1H NMR (400 MHz, CDCl3): δ 7.73 (d, 2H, J = 7.1 Hz), 7.677.61 (m, 1H), 7.58 (d, 2H, J = 7.5 Hz), 7.547.46 (m, 2H), 7.43731 (m, 10H), 7.307.23 (m, 4H), 7.227.16 (m, 7H). 31P{1H} NMR (121 MHz, CDCl3): δ 15.4 (s, P(O)Ph2). IR (CH2Cl2): 1918 cm1 (CdCdC). ESMS: calcd for C42H27ClOP [M + H+], 613.14; found 613.12.
X-ray Measurements for 24, 26, 33, 34, 35, 37, 37 3 DMSO, and 38. Crystallographic data for 24, 26, and 33 were collected on a Bruker SMART APEX CCD area detector diffractometer equipped with 3815
dx.doi.org/10.1021/om200357v |Organometallics 2011, 30, 3804–3817
Organometallics a Bruker SMART 1K CCD area detector (employing the program SMART35) using graphite-monochromated Mo KR radiation (λ = 0.71073 Å) and are listed in Tables 2 and 3 A full sphere of the reciprocal space was scanned by phi-omega scans. Data processing was carried out by use of the program SAINT,36 while the program SADABS37 was utilized for the scaling of diffraction data and an empirical absorption correction based on redundant reflections. Crystal data of 34, 35, 37, 37 3 DMSO, and 38 were collected using an Oxford Diffraction SuperNova A diffractometer fitted with an Atlas detector and X-ray tubes utilizing mirror-monochromated Mo KR radiation (λ = 0.71073 Å; 35, 38) or Cu KR radiation (λ = 1.54184 Å; 34, 37, 37 3 DMSO). An at least complete data set was collected, assuming that the Friedel pairs are not equivalent. An analytical absorption correction based on the shape of the crystal was performed.38All structures were solved by direct methods using SHELXS-97 and refined by full-matrix least-squares methods on F2 for all data using SHELXL-97.39 In the BPMO complex 26, the Ph2P and Ph2PdO moieties are crystallographically disordered, but each oxygen site is only half-occupied. Hydrogen atom treatment varied from compound to compound, depending on the crystal quality. All hydrogen atoms in 33 and hydrogen atoms attached to oxygen in 37 were located in the difference Fourier map and allowed to refine freely. All other hydrogen atoms were added at calculated positions and refined using a riding model. Their isotropic thermal displacement parameters were fixed to 1.2 times (1.5 times for methyl groups) the equivalent one of the parent atom. Anisotropic thermal displacement parameters were used for all non-hydrogen atoms.
’ ASSOCIATED CONTENT
bS
Supporting Information. X-ray crystallographic data for 24 (CCDC 820438), 26 (CCDC 820439), 33 (CCDC 820440), 34 (CCDC 820443), 35 (CCDC 820445), 37 (CCDC 820442), 37 3 DMSO (CCDC 820441), and 38 (CCDC 820444) in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*Phone: (+353) 1 716 2880. Fax: (+353) 1 716 1178. E-mail:
[email protected].
’ ACKNOWLEDGMENT We thank Science Foundation Ireland, University College Dublin, and the Centre for Synthesis and Chemical Biology funded by the Higher Education Authority’s Programme for Research in Third-Level Institutions (PRTLI) for generous financial support. ’ DEDICATION Dedicated to the memory of F. Gordon A. Stone, an inspiring mentor. ’ REFERENCES (1) (a) Banide, E. V.; Oulie, P.; McGlinchey, M. J. Pure Appl. Chem. 2009, 81, 1–17. (b) Harrington, L. E.; Britten, J. F.; McGlinchey, M. J. Org. Lett. 2004, 6, 787–790. (c) Banide, E. V.; Ortin, Y.; Seward, C. M.; Harrington, L. E.; M€uller-Bunz, H.; McGlinchey, M. J. Chem.—Eur. J. 2006, 12, 3275–3286. (d) Maguire, L.; Seward, C. M.; Baljak, S.; Reumann, T.; Ortin, Y.; Banide, E. V.; Nikitin, K.; M€uller-Bunz, H.; McGlinchey, M. J. Eur. J. Inorg. Chem. 2009, 3250–3258. (e) Oulie, P.; Altes, L.; Milosevic, S.; Bouteille, R.; Ortin, Y.; M€uller-Bunz, H.; McGlinchey, M. J. Organometallics 2010, 29, 676–686.
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