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Synthesis and structural characterization of phosphinoferrocene carboxylic acids with extended carboxyl pendants and their palladium(II) phosphinocarboxylate complexes
Journal of Organometallic Chemistry 846 (2017) 193e200
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Synthesis and structural characterization of phosphinoferrocene carboxylic acids with extended carboxyl pendants and their palladium(II) phosphinocarboxylate complexes e pni branský, Ivana Císarova Petr St cka*, Martin Za Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history: Received 16 May 2017 Received in revised form 12 June 2017 Accepted 14 June 2017 Available online 16 June 2017
Two phosphinoferrocene carboxylic acids differing in the two-carbon spacer separating the phosphinoferrocene moiety and the carboxyl group, Ph2PfcCH¼CHCO2H (1a) and Ph2PfcCH2CH2CO2H (1b; fc ¼ ferrocene-1,10 -diyl), were prepared from aldehyde Ph2PfcCHO by Horner-Wadsworth-Emmons olefination, reduction and hydrolysis. These acids reacted with [(LNC)Pd(acac)] (LNC ¼ 2-[(dimethylamino-kN)methyl]phenyl-kC1, acac ¼ pentane-2,5-dionate) under protonation and elimination of the Pdbound acetylacetonate ligand to afford the respective phosphinocarboxylate complexes, namely, the P,Obridged dimer [(LNC)Pd{m(P,O)-Ph2PfcCH¼CHCO2}]2 (6a) and the coordination polymer [(LNC)Pd{m(P,O)Ph2PfcCH2CH2CO2}]n (6a). The crystal structures of P-sulfides prepared from acids 1a and 1b, compounds Ph2P(S)fcCH¼CH2CO2H and Ph2P(S)fcCH2CH2CO2H, and the phosphinocarboxylate complexes 6a and 6b (in solvated form) were determined by single-crystal X-ray diffraction analysis. © 2017 Elsevier B.V. All rights reserved.
Keywords: Ferrocene Hybrid phosphines Phosphinocarboxylic ligands Hemilabile coordination Palladium complexes Structure elucidation
1. Introduction Phosphinocarboxylic acids are unique hybrid functional phosphine donors [1] that exhibit rich coordination chemistry, offering diverse coordination modes that differ by the involvement of the donor moieties present in their molecules in coordination and by the protonation state of the carboxyl group. The versatile coordination properties and modular structures make phosphinocarboxylic acids useful supporting ligands for a range of metalcatalyzed organic transformations [2]. In 1996, we reported the synthesis of the first ferrocene-based phosphinocarboxylic ligand, 10 -(diphenylphosphino)ferrocene-1carboxylic acid (Hdpf in Scheme 1) [3]. Along with studies into the coordination and catalytic properties of this relatively simple and synthetically accessible compound [4], we designed and studied several related phosphinoferrocene carboxylic donors including the isomeric, planar-chiral isomer of Hdpf, viz., (Sp)-2(diphenylphosphino)ferrocene-1-carboxylic acid [5], and other structurally related compounds [6]. Recently, we turned to the true Hdpf homologues A and B [7] (Scheme 1). Coordination studies
* Corresponding author. e pni E-mail address: [email protected] (P. St cka). http://dx.doi.org/10.1016/j.jorganchem.2017.06.013 0022-328X/© 2017 Elsevier B.V. All rights reserved.
with these ligands and the soft Pd(II) ion with various supporting ligands revealed considerable differences between the coordination behaviors of these compounds [7]. To further elucidate the role of the linking group connecting the phosphinoferrocenyl moiety and the carboxylic group representing the functional parts of these molecules, we decided to prepare compounds with longer saturated and unsaturated two-carbon bridges and evaluate their coordination properties under similar conditions. This contribution reports the synthesis and structural characterization of a pair of phosphinoferrocene carboxylic acids 1a and 1b (Scheme 1) and the Pd(II) phosphinocarboxylate complexes obtained thereof.
2. Results and discussion 2.1. Synthesis and characterization of phosphinocarboxylic acids 1 Both target ligands were prepared from 10 -(diphenylphosphino)-1-ferrocenecarboxaldehyde (1) [8] as depicted in Scheme 2. Phosphinocarboxylic acid 1a, possessing an unsaturated bridge, was prepared by Horner-Wadsworth-Emmons olefination [9] and subsequent hydrolysis of the intermediate ester 3a with 1 M KOH in a ternary THF-methanol-water system. It was isolated as a bright red crystalline solid in approximately 68% yield with respect to the
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Scheme 1.
starting aldehyde. Acid 1b was synthesized by reduction of ester 3a with diimine (HN¼NH) [10] generated in situ from 4toluenesulfonyl hydrazide and sodium acetate in aqueous THF, followed by hydrolysis of the obtained saturated ester 3b (the yield of 1b with respect to 3a was 49% after crystallization). The 31P NMR signals of compounds 1 and 3 were observed at dP z 16 ppm, similarly to that of the parent Hdpf [3]. The presence of the ethen-1,2-diyl bridge in 1a and 3a was evidenced by a characteristic pair of doublets due to the AM spin system of the CH¼CH protons in the 1H NMR spectrum with 3JHH constants (z16 Hz) indicating trans arrangements and, further, by the corresponding 13C NMR signals at dC ca. 115 and 148 ppm. Reduction of the linking group resulted in replacement of these resonances with signals of the ethane-1,2-diyl linker at a higher field in both 1H and 13 C NMR spectra (dH 2.47 ppm for 1b (degenerate) and 2.38e2.50 ppm for 3b; dC z 24 and 35 ppm for both compounds). In their IR spectra, the acids displayed strong bands attributable to C¼O stretching vibrations at 1662 and 1691 cm1 for the conjugated derivative 1a and the non-conjugated “aliphatic” acid 1b, respectively. As in the case of trans-cinnamic acid [11], the n(C¼O) band in the spectrum of 1a was observed in the proximity of another strong band tentatively attributable to C¼C stretching vibrations (1613 cm1 in 1a). In addition, the different extents of conjugation in the pairs of analogous compounds 1a-1b and 3a-3b were clearly manifested in their color. While the propenoic derivatives 1a and 3a were intensely red, their saturated counterparts were deep yellow (N.B. the conversion of 3a to 3b could be easily followed visually via the color change). Accordingly, the UV-vis spectrum of 1a recorded in dichloromethane showed a strong band at 300 nm and a pair of
Fig. 1. UV-vis spectra of 1a (red) and 1b (blue) recorded for 0.1 mM (1.0 mM in the inset) dichloromethane solutions (optical path 1 cm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
bands at 357 and 472 nm, whereas in the case of the saturated (non-conjugated) acid 1b, the low-energy absorption band appeared shifted to higher energies (443 nm) and was substantially weaker (Fig. 1). Crystallization of acids 1a and 1b proved to be rather difficult, especially when aimed at the preparation of X-ray quality single crystals. To obtain a pair of chemically analogous but better crystallizing derivatives allowing structure determination, phosphinocarboxylic acids 1 were converted to their corresponding phosphine sulfides 4 by treatment with elemental sulfur in acetone (Scheme 2). Thionation of the phosphine substituent was mainly indicated by a shift of the 31P NMR resonances to a lower field (dP 41e42) and, additionally, in the 13C NMR spectra through an increase in the JPC coupling constants [12]. The crystal structures of the phosphine sulfides are presented in Fig. 2, and the pertinent structural parameters are given in Table 1. Parameters describing the molecular geometry of 4a and 4b compare well with those reported for the structurally related acids, trans-2-[(2-ethoxycarbonyl)ferrocenyl]propenoic acid [13] and 3ferrocenylpropanoic acid [14], and also for 1,10 -bis(diphenylphosphinothioyl)ferrocene (dppfS2) [15]. The disubstituted ferrocene units in the structures of 4a and 4b assume positions near synclinal eclipsed (ideal value: t ¼ 72 [16]), and their cyclopentadienyls are tilted by less than approximately 3 . Because of conjugation, the entire polar pendant in 4a is located in the plane of its parent cyclopentadienyl ring, whereas in the structure of 4b, it extends
Scheme 2. Synthesis of phosphinocarboxylic acids 1 and their phosphine sulfides 4.
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located at the other cyclopentadienyl ring. The individual molecules in the crystals of both 4a and 4b associate into pairs via double O-H/O hydrogen bridges around the crystallographic inversion centers (i.e., cyclic R22(8) motifs in graph-set notation [18]; O1/O2 ¼ 2.624(2) Å for 4a, and 2.622(2) Å for 4b). In the case of 4b, the hydrogen-bonded dimers further assemble into infinite columnar stacks by intermolecular p/p interactions between inversion-related cyclopentadienyl rings C(1e5) at a centroid/centroid distance of 3.841(2) Å and an interplanar separation of 3.395(1) Å (Fig. 3). 2.2. Synthesis and characterization of Pd(II) phosphinocarboxylate complexes
Fig. 2. Views of the molecular structures of 4a (a) and 4b (b).
Table 1 Selected distances and angles for acids 4a and 4b (in Å and deg).a Parameter
4a
4b
P¼S P-Cb C1-C23 C23-C24 C24-C25 C25¼O1 C25-O2 S-P-Cc C-P-Cd C1-C23-C24 C23-C24-C25 C1-C23-C24-C25 O1-C25-O2 Fe-Cg1 Fe-Cg2 :Cp1,Cp2
1.9562(7) 1.797(2)-1.817(2) 1.447(3) 1.335(3) 1.459(3) 1.222(2) 1.323(2) 112.37(6)-115.63(6) 103.96(8)-106.01(8) 126.5(2) 120.3(2) 179.1(2) 122.6(2) 1.649(1) 1.6432(9) 2.9(1) 69.1(1)
1.9482(8) 1.786(2)-1.817(2) 1.497(3) 1.526(3) 1.486(4) 1.251(3) 1.293(3) 112.11(7)-115.07(7) 103.70(9)-106.52(9) 112.0(2) 113.8(2) 68.6(2) 122.9(2) 1.648(1) 1.636(1) 1.1(1) 65.5(2)
te
To prepare phosphinocarboxylate complexes from 1a and 1b and thus possibly employ both functional groups present in the structures of these donors (see Ref. [7]), we reacted the acids with the acetylacetonate (acac) complex [LNCPd(acac)] (5; LNC ¼ 2[(dimethylamino-kN)methyl]phenyl-kC1). Indeed, these reactions took the expected course, producing the anticipated phosphinocarboxylate complexes as a result of proton transfer between the acids and the acac ligand (Scheme 3). However, the natures of the crystallized products were substantially different. The reaction of acid 1a, featuring the less flexible unsaturated spacer, led to dimeric complex 6a, in which two chemically equivalent Pd(II) centers were bridged by the formed phosphinocarboxylate anion. Notably, analogous dipalladium complexes were obtained from 5 and acid B, whereas the similar reaction with ligand A led to a monopalladium chelate (Scheme 1) [7]. In contrast, the reaction involving 1b reproducibly afforded the coordination polymer catena-[(LNC)Pd(Ph2PfcCH2CH2CO2)]n (6b), whose one-dimensional polymeric chain propagated through an O,P-bridging phosphinocarboxylate ligand. Both complexes crystallized in solvated forms. The solubility of the discrete compound 6a was expectedly higher than that of the polymeric 6b, for which, however, a cleavage into smaller fragments (e.g., into cyclic oligomers or a monopalladium chelate) can be expected upon dissolution.
a Definition of the ring planes: Cp1 ¼ C(1e5), Cp2 ¼ C(6e1). Cg1 and Cg2 are the respective ring centroids. b The range of P-C(6,11,17) bond lengths. c The range of S-P-C(6,11,17) angles. d The range of C6-P-C(11,17) and C11-P-C17 angles. e Torsion angle C1-Cg1-Cg2-C6.
away from the ferrocene unit with the substituents at the central C23-C24 bond adopting a gauche conformation (cf. the torsion angles C1-C23-C24-C25 in Table 1) [17]. The conjugation can also be held responsible for a significant shortening of the bonds connecting the CH¼CH moiety in 4a to its functional substituents (viz., bonds C1-C23 and C24-25) as compared to the respective bonds in the structure of 4b featuring the saturated CH2CH2 bridge. The Ph2P(S) substituents in both structures are oriented with one phenyl group pointing above the ferrocene unit and the sulfur atoms directed away from the hydrocarbyl substituents, which are
Fig. 3. Principal intermolecular interactions in the crystal structure of 4b. The O2H90,,,O1 hydrogen bonds (black) and C23-H23,,,Ph interactions (red) are indicated by dotted lines and the p,,,p stacking interactions of cyclopentadienyl rings C(1e5) by blue double arrows. For clarity, only hydrogens involved in H-bonding interaction are shown. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. Section of the infinite coordination chain in the structure of 6b$2CHCl3. All hydrogen atoms are omitted for clarity.
Scheme 3. Reactions of Pd(II) acetylacetonate complex 5 with acids 1a and 1b.
The NMR spectra of 6a and 6b recorded in CD2Cl2 solutions suggested that the phosphine moieties remain coordinated in solution (dP z 30) and revealed only one set of resonances for both the phosphinocarboxylate ligand and the (LNC)Pd moiety. The signals of the LNC ligands were observed as 31P-coupled doublets (NMe2 and NCH2) and a set of second-order multiptets due to the C6H4 groups. The signals of the CH2CH2 linking groups were seen as distinct signals at dH 2.38 and 2.57 (those in 1a are degenerate), while the presence of the unsaturated bridge was manifested through a pair of doublets at dH 6.19 and 7.55. IR spectra recorded for the solid samples clearly confirmed deprotonation of the carboxyl groups (6a: 1581, 6b: 1579 cm1) and, in the case of 6a, also the presence of solvating ethyl acetate (1729 cm1 [19]). The structures of 6a$xAcOEt and 6b$2CHCl3 determined by single-crystal X-ray diffraction analysis are presented in Figs. 4 and 5, and the pertinent structural parameters are given in Tables 2 and 3. Compound 6a crystallizes extensively solvated with the solvent molecules disordered in structural voids left between the bulky complex molecules. The complex itself is a compact symmetrical dimer, but its molecules lack any external (crystallographic) symmetry. Geometric parameters describing the coordination
Table 2 Selected distances and angles for 6a$xAcOEt (in Å and deg).a Pd1-P1 Pd1-O22 Pd1-N1 Pd1-C31 P1-Pd1-O22 P1-Pd1-C31 N1-Pd1-O22 N1-Pd1-C31 C6-C23 C23-C24 C24-C25 C25¼O11 C25-O12 C6-C23-C24 C23-C24-C25 C6-C23-C24-C25 O11-C25-O12 C25-O12-Pd2 Fe1-Cg11 Fe1-Cg12 :Cp11,Cp12 t1b
2.2624(7) 2.113(2) 2.143(2) 2.000(3) 89.69(6) 97.60(7) 91.46(9) 81.43(9) 1.453(4) 1.322(3) 1.497(4) 1.236(3) 1.281(3) 125.2(2) 124.7(2) 179.6(2) 125.9(3) 116.9(2) 1.646(1) 1.646(1) 2.4(2) 137.7(2)
Pd2-P2 Pd2-O12 Pd2-N2 Pd2-C81 P2-Pd2-O12 P2-Pd2-C81 N2-Pd2-O12 N2-Pd2-C81 C56-C73 C73-C74 C74-C75 C75¼O21 C75-O22 C56-C73-C74 C73-C74-C75 C56-C73-C74-C75 O21-C75-O22 C75-O22-Pd1 Fe2-Cg21 Fe2-Cg22 :Cp21,Cp22 t2b
2.262(1) 2.114(2) 2.151(2) 1.997(3) 92.61(6) 94.63(8) 91.66(8) 81.18(9) 1.455(4) 1.329(4) 1.504(4) 1.250(3) 1.250(4) 125.7(3) 123.7(3) 179.3(2) 126.8(3) 117.3(2) 1.648(1) 1.649(1) 3.3(1) 138.8(2)
a Definition of the ring planes: Cp11 ¼ C(1e5), Cp12 ¼ C(6e10), Cp21 ¼ C(51e55), Cp22 ¼ C(56e60). Cg11, Cg12, C21 and Cg22 are the corresponding ring centroids. b Torsion angles C1-Cg11-Cg12-C6 (t1) and C51-Cg21-Cg22-C56 (t2).
Fig. 4. View of the complex molecule in the structure of 6a$xAcOEt. The hydrogen atoms are omitted to avoid complicating the figure.
P. Stepnicka et al. / Journal of Organometallic Chemistry 846 (2017) 193e200 Table 3 Selected interatomic distances and angles for 6b$2CHCl3 (in Å and deg).a Distances Pd-P Pd-O2i Pd-N Pd-C31 C6-C23 C23-C24 C24-C25 C25¼O1 C25-O2 Fe-Cg1 Fe-Cg2
P-Pd-O2i P-Pd-C31 N-Pd-O2i N-Pd-C31 C6-C23-C24 C23-C24-C25 C6-C23-C24-C25 O1-C25-O2 C25-O2-Pdii :Cp1,Cp2
tb
4. Experimental 4.1. Materials and methods
Angles 2.2573(5) 2.108(2) 2.153(2) 1.999(2) 1.504(3) 1.519(3) 1.532(3) 1.240(2) 1.278(2) 1.647(1) 1.655(1)
197
94.28(4) 95.01(6) 88.53(6) 82.78(7) 116.0(2) 112.4(2) 171.4(2) 125.7(2) 118.5(1) 4.6(1) 77.3(1)
a
Definition of the ring planes: Cp1 ¼ C(1e5), Cp2 ¼ C(6e1). Cg1 and Cg2 are the respective ring centroids). Symmetry operations used to generate equivalent positions: i ¼ 1x, 1/2 þ y, 3/2z, ii ¼ 1x, 1/2 þ y, 3/2z. b Torsion angle C1-Cg1-Cg2-C6.
environment of the Pd(II) center compare well to those reported for the analogous phosphinocarboxylate complexes obtained from ligands A and B (see Scheme 1) [7]. The Pd center has a {PONC} donor set with trans-PN arrangement with very similar Pdedonor distances for both structurally independent Pd atoms. A difference can be found among the interligand angles because the P2-Pd2-O12 is slightly more opened and the adjacent P2-Pd2-C81 is slightly more acute (both by ca. 3 ) than the corresponding angles pertaining to Pd1, which can, however, be ascribed to steric factors. The propanoate chains in the structure of 6a remain in the plane of their bonding cyclopentadienyl rings, but the ferrocene substituents assume more distant positions than in 4a (compare the t angles in Tables 1 and 2) so as to allow for bridging coordination. Furthermore, deprotonation and coordination of the carboxyl group diminished the difference between the individual C-O distances compared with those in 4a. The crystal structure of 6b,2CHCl3 confirms the polymeric nature of this compound. The anions resulting through deprotonation of acid 1b bridge equivalent (LNC)Pd fragments related by a crystallographic two-fold screw axis into an infinite zig-zag chain oriented parallel to the b axis and the twisted square-planar geometry around the Pd atom is very similar to that in 6a. The conformation of the disubstituted ferrocene unit in the structure of 6b is close to synclinal eclipsed with the carboxylate pendant extending to the side of the ferrocene unit, nearly perpendicularly with respect to the C1-P bond.
3. Conclusion The newly prepared phosphinocarboxylic acids 1a and 1b reacted with complex 5 similarly to how Hdpf and compounds A and B do, providing Pd(II) phosphinocarboxylate complexes. While 1a gave rise to a P,O-bridged dipalladium(II) complex 6a (analogous to that obtained from compound B), the reaction involving 1b produced one-dimensional coordination polymer 6b, which propagates through bridging phosphinocarboxylate ligands. The selective formation of these particular products appears to be the result of a subtle interplay between solubility and crystallization phenomena in addition to equilibria of various forms such as presumed monopalladium chelates, dipalladium dimers and other oligomeric species, rather than real changes in the reaction course imparted by changes in the ligand structure. Such a behavior is clearly enabled by hemilabile coordination of the phosphinocarboxylate ligands, whose donor atoms form dative bonds to the soft palladium(II) ions of different strength.
All syntheses were performed under an argon atmosphere with the exclusion of direct daylight. Toluene was dried over potassium metal and distilled under argon. THF and acetone were distilled from potassium/benzophenone ketyl and from anhydrous K2CO3, respectively. Chloroform was dried over calcium hydride and distilled under an argon atmosphere. Compounds 2 [8] and 5 [20] were prepared according to reported procedures. Other chemicals (Sigma-Aldrich, Fluka) and solvents for crystallizations (Lach-Ner, Czech Republic; analytical grade) were used without any additional purification. NMR spectra were recorded on a Varian Unity Inova spectrometer (1H, 399.95; 13C, 100.58; 31P, 161.90 MHz) at 25 C. Chemical shifts (d/ppm) are given relative to internal tetramethylsilane (13C and 1H) or to external 85% aqueous H3PO4 (31P). In addition to the standard notation of signal multiplicity, vt and vq are used to denote virtual triplets and quartets arising from AA0 BB0 and AA0 BB0 X spin systems of the ferrocene cyclopentadienyls (A, B ¼ 1H, X ¼ 31P). IR spectra were measured with an FT IR Nicolet Magna 650 instrument in Nujol mulls. Electron impact (EI) and electrospray ionization (ESI) mass spectra were obtained on a VG Zab SEQ and a Bruker Esquire 3000 spectrometer, respectively. 4.2. Synthesis of (E)-ethyl 3-[10 -(diphenylphosphino)ferrocenyl]propenoate (3a) Triethyl phosphonoacetate (3.0 mL, 15 mmol) was added dropwise to a stirred suspension of sodium hydride (0.242 g, 10 mmol) in toluene (15 mL), whereupon the solid hydride dissolved rapidly and with vigorous effervescence to give a clear, colorless solution. After stirring for another 15 min at 0 C, a solution of aldehyde 2 (2.003 g, 5.00 mmol) in toluene (35 mL) was introduced, and the reaction flask was transferred to an oil bath maintained at 60 C. The reaction mixture was stirred overnight (the initial orange brown color due to the aldehyde changed quickly to deep red) before being cooled to room temperature. Then, the mixture was diluted with diethyl ether (ca. 25 mL; insoluble brown gummy material was discarded), washed successively with water and saturated aqueous NaCl solution and finally dried over anhydrous magnesium sulfate. The volatiles were removed under reduced pressure, and the dark red oily residue was purified by column chromatography (silica gel, hexaneeether 1:2). The first dark red band was collected and evaporated under vacuum (1 h at 60 C/ 1 Torr) to afford 3a as a deep red viscous oil. Yield: 2.198 g (93%). 1 H NMR (CDCl3): d 1.32 (t, 3JHH ¼ 7.1 Hz, 3 H, OCH2Me), 4.07 (vq, 0 J ¼ 1.9 Hz, 2 H, fc), 4.20 (q, 3JHH ¼ 7.1 Hz, 2 H, OCH2), 4.28 (vt, J0 ¼ 1.9 Hz, 2 H, fc), 4.36, 4.37 (2 vt, J0 ¼ 1.8 Hz, 2 H, fc), 5.93 (d, 3 JHH ¼ 15.8 Hz, 1 H, ¼CH(a)), 7.28e7.39 (m, 10 H, PPh2), 7.37 (d, 3 JHH ¼ 15.8 Hz, 1 H, ¼CH(b)). 13C{1H} NMR (CDCl3): d 14.35 (OCH2Me), 60.15 (OCH2), 69.42, 72.08, 72.79 (d, JPC ¼ 4 Hz), 74.15 (d, JPC ¼ 15 Hz) (4 CH of fc); 77.41 (d, 1JPC ¼ 8 Hz, CP of fc), 79.31 (CCH of fc), 115.65 (¼CH(a)), 128.19 (d, JPC ¼ 7 Hz), 128.63, 133.42 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 138.63 (d, 1JPC ¼ 10 Hz, Cipso of PPh2), 144.74 (¼CH(b)), 167.02 (CO2H). 31P{1H} NMR (CDCl3): d 16.9 (s). EI MS: m/z (relative abundance) 469 (32), 468 (100, Mþ$), 439 (4, [M Et]þ), 395 (14, [M Et CO2]þ), 370 (68, [FcPPh2]þ$), 321 (10), 293 (16), 226 (7), 171 (7), 170 (5), 121 (6, [FeC5H5]þ), 83 (10). EI HR MS calc. for C27H56 25FeO2P: 468.0942, found 468.0932. 4.3. Synthesis of ethyl 3-[10 -(diphenylphosphino)ferrocenyl]propanoate (3b) p-Toluenesulfonyl hydrazide (2.79 g, 15 mmol) was added to 3a
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(1.409 g, 3.0 mmol) dissolved in dry THF (30 mL) followed by an aqueous solution of sodium acetate (1.27 g, 15 mmol in 30 mL). The resulting heterogeneous mixture was refluxed overnight (22 h; the original burgundy red color changed to orange yellow) and then cooled to room temperature and treated with saturated aqueous K2CO3 solution under vigorous stirring for 30 min. The organic layer was separated, washed twice with brine and dried over MgSO4. The solvent was removed under vacuum, and the residue was purified by column chromatography (silica gel, hexaneeether 1:1). Evaporation of the major yellow orange band (a small forerun was discarded) yielded the propanoate ester 3b as an amber oil, which solidified upon standing at 4 C. Yield: 1.142 g (81%). 1 H NMR (CDCl3): d 1.25 (t, 3JHH ¼ 7.1 Hz, 3 H, OCH2Me), 2.38e2.50 (m, 4 H, CH2CH2), 3.95, 4.00 (2 vt, J0 ¼ 1.8 Hz, 2 H) and 4.04 (vq, J0 ¼ 1.9 Hz, 2 H) (3 CH of fc); 4.12 (q, 3JHH ¼ 7.1 Hz, 2 H, OCH2), 4.32 (vt, J0 ¼ 1.9 Hz, 2 H, fc); 7.27e7.40 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 14.26 (OCH2Me), 24.54 and 35.69 (CH2CH2); 60.37 (OCH2), 68.70, 69.08, 71.53 (d, JPC ¼ 4 Hz), 73.41 (d, JPC ¼ 15 Hz) (4 CH of fc); 75.71 (br s, CP of fc), 88.11 (CCH of fc), 128.10 (d, JPC ¼ 7 Hz), 128.45, 133.49 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 139.16 (br d, 1 JPC ¼ 10 Hz, Cipso of PPh2), 173.03 (CO2H). 31P{1H} NMR (CDCl3): d 16.2 (s). EI MS: m/z (relative abundance) 471 (31), 470 (100, Mþ$), 425 (5), 386 (12), 370 (32, [FcPPh2]þ$), 293 (11), 226 (6), 221 (7), 212 (19),171 (11),170 (7), 147 (6), 121 (5, [FeC5H5]þ), 91 (5). EI HR MS calc. for C27H56 27FeO2P: 470.1098, found 470.1085. 4.4. Synthesis of (E)-3-[10 -(diphenylphosphino)ferrocenyl]propenoic acid (1a) A solution of 3a (2.106 g, 4.50 mmol) in THF (30 mL) was mixed with methanol (30 mL) and aqueous KOH (30 mL 3 M), and the resulting clear solution was refluxed for 6 h. The mixture was poured onto crushed ice (ca. 100 g) and strongly acidified with 85% aqueous H3PO4. The organic solvents were removed under vacuum, and the residue was extracted with dichloromethane (several times). The combined organic layers were washed with saturated aqueous NaCl, dried over MgSO4, and filtered through a pad of silica gel, which was subsequently eluted with dichloromethaneemethanol (95:5). The eluate was evaporated under vacuum to leave a residue, which was immediately dissolved in hot ethyl acetate; the solution was crystallized at room temperature and then at 18 C. The solid formed was filtered off, washed with hexane and dried in air to give analytically pure 1a as deep red needles. Yield: 1.445 g (73%). M.p. 176e177 C (ethyl acetate). 1H NMR (CDCl3): d 4.09 (vq, J0 ¼ 1.9 Hz, 2 H), 4.34, 4.38, 4.40 (3 vt, J0 ¼ 1.9 Hz, 2 H) (4 CH of fc); 5.92 (d, 3JHH ¼ 15.6 Hz, 1 H, ¼CH(a)), 7.29e7.38 (m, 10 H, PPh2), 7.47 (d, 3JHH ¼ 15.6 Hz, 1 H, ¼CH(b)). 13C{1H} NMR (CDCl3): d 69.76, 72.51, 72.82 (d, JPC ¼ 4 Hz), 74.29 (d, JPC ¼ 15 Hz) (4 CH of fc); 77.69 (d, 1JPC ¼ 8 Hz, CP of fc), 78.66 (CCH of fc), 114.51 (¼CH(a)), 128.22 (d, JPC ¼ 7 Hz), 128.70, 133.41 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 138.53 (d, 1JPC ¼ 9 Hz, Cipso of PPh2), 147.74 (¼CH(b)), 172.39 (CO2H). 31P{1H} NMR (CDCl3): d 17.0 (s). IR (DRIFTS, KBr): nmax 1662 (vs), 1613 (vs), n(C¼O) and n(C¼C); 1474 (m), 1430 (m), 1308 (s), 1280 (m), 1246 (m), 1227 (m), 1160 (m), 1046 (m), 1032 (m), 978 (m), 867 (m), 834 (m), 818 (m), 747 (m), 741 (m), 696 (s), 657 (m), 500 (s), 479 (m) cm1. UV-vis (CH2Cl2): lmax 300 nm (ε 14770 M1 cm1), 357 nm (ε 1890 M1 cm1), 472 nm (ε 1070 M1 cm1). Anal. Calc. for C25H21FeO2P: C 68.20, H 4.81%. Found: C 68.11, H 4.76%. 4.5. Synthesis of 3-[10 -(diphenylphosphino)ferrocenyl]propanoic acid (1b) Hydrolysis of 3b was performed as described in detail above. A
mixture obtained by mixing a solution of 3b (1.177 g, 2.5 mmol) in THF (25 mL), methanol (25 mL) and aqueous KOH solution (25 mL 3 M) was refluxed for 6 h and then poured onto ice (ca. 100 g). The mixture was acidified with 85% aqueous H3PO4, the organic solvents were removed under vacuum, and the residue was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and filtered through a pad of silica gel (elution with dichloromethane). The eluate was evaporated under vacuum, the residue was dissolved in hot ethyl acetate, and the solution was crystallized by addition of hexane and standing at 18 C overnight. The separated crystalline solid was filtered off, washed with hexane and dried in air to give 1b as fine, bright yellow needles. Yield: 0.679 g (61%). M.p. 129e130 C (ethyl acetate-hexane). 1H NMR (CDCl3): d 2.47 (s, 4 H, CH2CH2), 3.97, 4.01 (2 vt, J0 ¼ 1.8 Hz, 2 H), 4.05 (vq, J0 ¼ 1.8 Hz, 2 H), 4.33 (vt, J0 ¼ 1.8 Hz, 2 H) (4 CH of fc); 7.28e7.40 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 24.19 and 35.29 (CH2CH2); 68.79, 69.15, 71.64 (d, JPC ¼ 4 Hz), 73.47 (d, JPC ¼ 15 Hz) (4 CH of fc); 75.01 (d, 1JPC z 2 Hz, CP of fc), 87.89 (CCH of fc), 128.18 (d, JPC ¼ 7 Hz), 128.72, 133.46 (d, JPC ¼ 19 Hz) (3 CH of PPh2); 138.27 (d, 1JPC ¼ 5 Hz, Cipso of PPh2), 178.55 (CO2H). 31P{1H} NMR (CDCl3): d 16.4 (s). IR (DRIFTS): nmax 1691 (vs) n(C¼O); 1475 (m), 1432 (s), 1308 (s), 1227 (m), 1192 (m), 1161 (m), 1094 (m), 1041 (w), 1027 (m), 951 (br m), ca. 830 (m composite), 749 (s), 741 (s), 697 (s), 634 (m), 501 (s), 476 (s), 459 (m) cm1. UV-vis (CH2Cl2): lmax 443 nm (ε 162 M1 cm1). Anal. Calc. for C25H23FeO2P: C 67.89, H 5.24%. Found: C 67.67, H 5.16%. 4.6. Synthesis of (E)-3-[10 -(diphenylphosphinothioyl)ferrocenyl]propenoic acid (4a) A solution of acid 1a (88.2 mg, 0.20 mmol) and elemental sulfur (8.0 mg, 0.25 mmol) in acetone (5 mL) was stirred at room temperature overnight and then evaporated to dryness. The residue was extracted with hot ethyl acetate, and the product was crystallized by addition of hexane and cooling to 18 C overnight. The separated material was filtered off, washed with a small quantity of hexane and dried in air to give 4a as a burgundy red, crystalline solid. Yield: 80.7 mg (85%). 1 H NMR (CDCl3): d 4.42 (vq, J0 ¼ 1.9 Hz, 2 H), 4.47, 4.50 (2 vt, J0 ¼ 1.9 Hz, 2 H), 4.51 (vq, J0 ¼ 1.9 Hz, 2 H) (4 CH of fc); 5.88 (d, 3 JHH ¼ 15.7 Hz, 1 H, ¼CH(a)), 7.36 (d, 3JHH ¼ 15.7 Hz, 1 H, ¼CH(b)), 7.40e7.76 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 70.46, 73.37, 73.66 (d, JPC ¼ 10 Hz), 74.32 (d, JPC ¼ 12 Hz) (4 CH of fc); 76.69 (d, 1 JPC ¼ 96 Hz, CP of fc), 79.43 (CCH of fc), 115.38 (¼CH(a)), 128.31 (d, JPC ¼ 12 Hz), 131.46 (d, JPC z 4 Hz), 131.54 (d, JPC ¼ 11 Hz) (3 CH of PPh2); 134.10 (d, 1JPC ¼ 87 Hz, Cipso of PPh2), 146.78 (¼CH(b)), 171.91 (CO2H). 31P{1H} NMR (CDCl3): d þ41.4 (s). EI MS, m/z (relative abundance): 472 (82, Mþ$), 440 (8, [M S]þ$), 428 (5, [M CO2]þ$), 402 (5), 368 (6), 354 (23), 337 (100, [M C5H4CHCHCO2H]þ). EI HR MS calc. for C25H56 21FeO2PS: 472.0349, found 472.0331. 4.7. Synthesis of 3-[10 -(diphenylphosphinothioyl)ferrocenyl]-
propanoic acid (4b) Starting with 1b (88.7 mg, 0.20 mmol) and sulfur (8.0 mg, 0.25 mmol), the same procedure used for the synthesis of 4a (see Section 4.6) provided 4b as fine yellow needles. Yield: 90.2 mg (95%). 1 H NMR (CDCl3): d 2.46 (s, 4 H, CH2CH2), 4.04, 4.14 (2 vt, J0 ¼ 1.8 Hz, 2 H), 4.38, 4.46 (2 vq, J0 ¼ 1.8 Hz, 2 H) (4 CH of fc); 7.38e7.76 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 24.04 and 35.07 (CH2CH2); 69.66, 70.07, 72.48 (d, JPC ¼ 10 Hz), 73.53 (d, JPC ¼ 13 Hz) (4 CH of fc); 75.10 (d, 1JPC ¼ 99 Hz, CP of fc), 88.69 (CCH of fc),
P. Stepnicka et al. / Journal of Organometallic Chemistry 846 (2017) 193e200
128.19 (d, JPC ¼ 13 Hz), 131.21 (d, JPC ¼ 3 Hz), 131.61 (d, JPC ¼ 11 Hz) (3 CH of PPh2); 134.57 (d, 1JPC ¼ 87 Hz, Cipso of PPh2), 177.75 (CO2H). 31P{1H} NMR (CDCl3): d þ42.1 (s). Anal. Calc. for C25H23FeO2PS: C 63.30, H 4.89%. Found: C 63.27, H 4.82%. 4.8. Preparation of complex 6a Acid 1a (44.0 mg, 0.10 mmol) and complex 5 (34.0 mg, 0.10 mmol) were dissolved in chloroform (1 mL), and the resulting mixture was stirred for 1 h, whereupon it deposited an orange precipitate. Then, the reaction mixture was evaporated under vacuum, leaving an orange residue that was taken up with dichloromethane (ca. 5 mL) with sonication and gentle heating; the extract was filtered directly into warm ethyl acetate (20 mL). Slow cooling to room temperature and then to 4 C resulted in the separation of a crystalline product, which was isolated by suction, washed with ethyl acetate and pentane, and dried under vacuum to give 6a$4AcOEt as an orange crystalline solid (needles). Yield: 58.2 mg (68%). Crystals used for structure determination were obtained from hot ethyl acetate. 1 H NMR (CD2Cl2): d 2.76 (d, 4JPH ¼ 2.6 Hz, 6 H, NMe2), ca. 4.1 (very br s, 4 H), 4.19 (br s, 2 H), 4.92 (br s, 4 H) (4 CH of fc and CH2N), 6.19 (d, 3JHH ¼ 15.7 Hz, 1 H, CH¼), 6.24e6.31 (m, 2 H, 2 CH of C6H4), 6.73e6.77 (m, 1 H, CH of C6H4), 6.97 (br dd, J1 ¼ 7.6, J2 ¼ 1.0 Hz, 1 H, CH in C6H4), 7.30e7.37 (br m, 4 H, PPh2), 7.40e7.46 (br m, 2 H, PPh2), 7.55 (d, 3JHH ¼ 15.7 Hz, 1 H, CH¼), 7.64 (br s, 4 H, PPh2). 31P{1H} NMR (CD2Cl2): d 30.6 (s). IR (Nujol): nmax 3369 (br w), 3047 (m), 1729 (s), 1645 (m), 1581 (s), 1353 (vs), 1339 (s), 1306 (m), 1279 (m), 1246 (s), 1183 (w), 1168 (m), 1100 (m), 1046 (m), 1024 (m), 994 (w), 974 (m), 867 (vw), 844 (m), 827 (m), 780 (vw), 745 (s), 710 (w), 696 (m), 681 (m), 631 (w), 541 (m), 525 (m), 505 (s), 471 (m) cm1. ESIþ MS: m/z 680 ([Pd(C6H4CH2NMe2)(Ph2PfcCH¼ CHCO2) þ H]þ). Anal. Calc. for C68H64Fe2N2O4P2Pd2$4AcOEt (1712.07): C 58.93, H 5.65, N 1.64%. Found: C 58.87, H 5.26, N 1.75%. 4.9. Preparation of complex 6b Acid 1b (44.2 mg, 0.10 mmol) and complex 5 (34.0 mg, 0.1 mmol) were dissolved in chloroform (1 mL). The reaction mixture was stirred for 1 h and then filtered through a PTFE syringe filter (pore size 0.45 mm) into a test tube. The solution was layered with 0.5 mL of chloroform used to rinse the reaction vessel and
199
0.5 mL of pure chloroform and then cooled to 4 C. The cooled solution was layered with a chloroformemethyl t-butyl ether mixture (1 þ 1 mL) and then methyl t-butyl ether (ca. 20 mL). The test tube was stoppered and set aside for crystallization at room temperature. The solid, which separated after several days, was filtered off, washed with methyl t-butyl ether and dried under vacuum to afford solvated complex 6b. Yield of 6b,0.45CHCl3: 49.5 mg (67%). Crystals suitable for X-ray diffraction analysis were selected from the reaction batch. 1 H NMR (CD2Cl2): d 2.38 (br t, 3JHH ¼ 6.1 Hz, 2 H, CH2 of CH2CH2CO2), 2.57 (br t, 3JHH ¼ 5.4 Hz, 2 H, CH2 of CH2CH2CO2), 2.75 (d, 4JPH ¼ 2.8 Hz, 6 H, NMe2), 3.64 (br s, 2 H, CH of fc), 3.89 (br s, 2 H, CH of fc), 3.99 (br d, 4JPH ¼ 1.8 Hz, 2 H, NCH2), 4.48 (br s, 2 H, CH of fc), 4.72 (br s, 2 H, CH of fc), 5.91 (br ddd, J1 ¼ 7.8, J2 ¼ 5.5, J3 ¼ 1.1 Hz, 1 H, CH of C6H4), 6.24 (br td, J1 ¼ 7.6, J2 ¼ 1.5 Hz, 1 H, CH of C6H4), 6.68 (br td, J1 ¼ 7.3, J2 ¼ 1.2 Hz, 1 H, CH of C6H4), 6.86 (br dd, J1 ¼ 7.4, J2 ¼ 1.5 Hz, 1 H, CH of C6H4), 7.68e7.86 (br s, 4 H, PPh2), 7.32e7.42 (br m, 6 H, PPh2). 31P{1H} NMR (CD2Cl2): d 29.6 (s). IR (Nujol): nmax 3048 (m), 2210 (m), 1579 (vs), 1396 (m), 1392 (m), 1326 (m), 1304 (w), 1243 (m), 1183 (w), 1164 (m), 1101 (m), 1064 (w), 1035 (m), 996 (w), 975 (w), 936 (w), 847 (m), 837 (m), 815 (w), 783 (vw), 750 (s), 740 (s), 733 (m), 727 (m), 696 (s), 662 (w), 640 (w), 543 (m), 522 (m), 503 (m), 493 (m), 473 (m) cm1. ESIþ MS: m/z 682 ([Pd(C6H4CH2NMe2)(Ph2PfcCH2CH2CO2) þ H]þ). Anal. Calc. for C34H34FeNO2PPd$0.45CHCl3 (735.56): C 58.25, H 4.72, N 1.90%. Found: C 55.87, H 5.12, N 1.70%. 4.10. X-ray crystallography X-ray quality crystals were either selected directly from the reaction batch (4b: yellow needle, 0.05 0.10 0.43 mm3; 6b$2CHCl3: orange prism, 0.04 0.21 0.28 mm3) or, alternatively, grown by recrystallization from chloroformehexane (4a: ruby red prism, 0.18 0.25 0.30 mm3) and warm ethyl acetate (6a$xAcOEt: orange-red prism, 0.04 0.11 0.28 mm3). Full-set diffraction data (qmax ¼ 27.5 , data completeness > 99%) were collected on a Nonius KappaCCD diffractometer (4a and 4b) or a Bruker D8 VENTURE Kappa Duo diffractometer with a PHOTON100 detector and an ImS micro-focus X-ray source (6a and 6b), both equipped with a Cryostream Cooler (Oxford Cryosystems) using Mo Ka radiation (l ¼ 0.71073 Å) at 150(2) K. The structures were solved by direct methods (SIR97 for 4a/4b
Table 4 Summary of the relevant crystallographic data and structure refinement parameters. Compound
4a
4b
6a$xAcOEt
6b$2CHCl3
Formula M (g mol1) Crystal system Space group a (Å) b(Å) c (Å) a ( ) b ( ) g ( ) Z V (Å3) Dcalc (g mL1) Collected diffrns, Rint (%)a Unique/observedb diffrns R (obsd data) (%)c R, wR (all data)(%)c Dr (e Å3)
C25H23FeO2PS 472.30 monoclinic P21/n (no.14) 14.8629(3) 9.9182(2) 15.7146(3)
C25H23FeO2PS 474.31 triclinic P1 (no. 2) 8.7530(2) 9.3560(3) 13.6180(5) 100.447(2) 90.333(2) 97.398(2) 2 1087.12(6) 1.449 21133, 4.30 5023/3801 3.69 6.05, 8.43 0.34, 0.38
C68H64Fe2N2O4P2Pd2$C4H8O2d 1447.75d monoclinic C2/c (no. 15) 42.196(2) 10.7797(6) 34.949(2)
C34H34FeNO2PPd$2CHCl3 920.58 monoclinic P21/c (no.14) 14.3586(7) 13.8101(6) 18.8254(9)
113.632(2)
93.250(2)
8 14564(1) 1.321d 98124, 2.56 14323/11939 2.95 4.05, 7.13 0.91, 0.63
4 3727.0(3) 1.641 74422, 1.63 8559/7532 2.51 3.23, 6.32 1.06, 0.69
a b c d
112.104(1) 4 2146.28(7) 1.462 29659, 3.20 4912/4163 3.14 4.05, 8.09 0.37, 0.36
Rint ¼ SrF2o F2o(mean)r/SF2o, where F2o(mean) stands for an average intensity of symmetry-equivalent diffractions. Diffractions with Io > 2s(Io). R ¼ SrrFor rFcrr/SrFor, wR ¼ [S{w(F2o F2c )2}/S w(F2o)2]1/2. These values are affected by PLATON/SQUEEZE.
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P. Stepnicka et al. / Journal of Organometallic Chemistry 846 (2017) 193e200
[21] and XT2014 for solvated 6a/6b [22]) and then refined by a fullmatrix least squares procedure based on F2 (SHELXL97 for 4a/4b, and SHELXL-2014 for solvated 6a/6b [23]). The non-hydrogen atoms were refined with anisotropic thermal motion parameters. Carboxylic hydrogen atoms in the structures of 4a and 4b were located on difference Fourier maps, and their positions were freely refined with Uiso(H) assigned to 1.2 Ueq(O2). All other hydrogen atoms were included in their calculated positions and refined using the “riding model”. Some of the solvent molecules present in the structure of extensively solvated 6a$xAcOEt were disordered. Hence, their contribution to the overall scattering was removed using the SQUEEZE routine [24] in PLATON [25], and the structure was refined against the generated data. Relevant crystallographic data, data collection and refinement parameters are presented in Table 4. All geometric calculations were performed with a recent version of the PLATON program [25], which was also used to prepare the structural diagrams. CCDC 1549289 (4a), 1549290 (4b), 1549291 (6a$xAcOEt), and 1549292 (6b$2CHCl3) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via the Internet at http://www.ccdc.cam.ac.uk/ Acknowledgments
[3] [4] [5] [6]
[7] [8] [9]
[10] [11] [12] [13]
[14] [15]
[16] [17]
Research leading to the results reported in this paper received financial support from the Czech Science Foundation (project no. 15-11571S).
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Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structural characterization of phosphinoferrocene carboxylic acids with extended carboxyl pendants and their palladium(II) phosphinocarboxylate complexes e pni branský, Ivana Císarova Petr St cka*, Martin Za Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history: Received 16 May 2017 Received in revised form 12 June 2017 Accepted 14 June 2017 Available online 16 June 2017
Two phosphinoferrocene carboxylic acids differing in the two-carbon spacer separating the phosphinoferrocene moiety and the carboxyl group, Ph2PfcCH¼CHCO2H (1a) and Ph2PfcCH2CH2CO2H (1b; fc ¼ ferrocene-1,10 -diyl), were prepared from aldehyde Ph2PfcCHO by Horner-Wadsworth-Emmons olefination, reduction and hydrolysis. These acids reacted with [(LNC)Pd(acac)] (LNC ¼ 2-[(dimethylamino-kN)methyl]phenyl-kC1, acac ¼ pentane-2,5-dionate) under protonation and elimination of the Pdbound acetylacetonate ligand to afford the respective phosphinocarboxylate complexes, namely, the P,Obridged dimer [(LNC)Pd{m(P,O)-Ph2PfcCH¼CHCO2}]2 (6a) and the coordination polymer [(LNC)Pd{m(P,O)Ph2PfcCH2CH2CO2}]n (6a). The crystal structures of P-sulfides prepared from acids 1a and 1b, compounds Ph2P(S)fcCH¼CH2CO2H and Ph2P(S)fcCH2CH2CO2H, and the phosphinocarboxylate complexes 6a and 6b (in solvated form) were determined by single-crystal X-ray diffraction analysis. © 2017 Elsevier B.V. All rights reserved.
Keywords: Ferrocene Hybrid phosphines Phosphinocarboxylic ligands Hemilabile coordination Palladium complexes Structure elucidation
1. Introduction Phosphinocarboxylic acids are unique hybrid functional phosphine donors [1] that exhibit rich coordination chemistry, offering diverse coordination modes that differ by the involvement of the donor moieties present in their molecules in coordination and by the protonation state of the carboxyl group. The versatile coordination properties and modular structures make phosphinocarboxylic acids useful supporting ligands for a range of metalcatalyzed organic transformations [2]. In 1996, we reported the synthesis of the first ferrocene-based phosphinocarboxylic ligand, 10 -(diphenylphosphino)ferrocene-1carboxylic acid (Hdpf in Scheme 1) [3]. Along with studies into the coordination and catalytic properties of this relatively simple and synthetically accessible compound [4], we designed and studied several related phosphinoferrocene carboxylic donors including the isomeric, planar-chiral isomer of Hdpf, viz., (Sp)-2(diphenylphosphino)ferrocene-1-carboxylic acid [5], and other structurally related compounds [6]. Recently, we turned to the true Hdpf homologues A and B [7] (Scheme 1). Coordination studies
* Corresponding author. e pni E-mail address: [email protected] (P. St cka). http://dx.doi.org/10.1016/j.jorganchem.2017.06.013 0022-328X/© 2017 Elsevier B.V. All rights reserved.
with these ligands and the soft Pd(II) ion with various supporting ligands revealed considerable differences between the coordination behaviors of these compounds [7]. To further elucidate the role of the linking group connecting the phosphinoferrocenyl moiety and the carboxylic group representing the functional parts of these molecules, we decided to prepare compounds with longer saturated and unsaturated two-carbon bridges and evaluate their coordination properties under similar conditions. This contribution reports the synthesis and structural characterization of a pair of phosphinoferrocene carboxylic acids 1a and 1b (Scheme 1) and the Pd(II) phosphinocarboxylate complexes obtained thereof.
2. Results and discussion 2.1. Synthesis and characterization of phosphinocarboxylic acids 1 Both target ligands were prepared from 10 -(diphenylphosphino)-1-ferrocenecarboxaldehyde (1) [8] as depicted in Scheme 2. Phosphinocarboxylic acid 1a, possessing an unsaturated bridge, was prepared by Horner-Wadsworth-Emmons olefination [9] and subsequent hydrolysis of the intermediate ester 3a with 1 M KOH in a ternary THF-methanol-water system. It was isolated as a bright red crystalline solid in approximately 68% yield with respect to the
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Scheme 1.
starting aldehyde. Acid 1b was synthesized by reduction of ester 3a with diimine (HN¼NH) [10] generated in situ from 4toluenesulfonyl hydrazide and sodium acetate in aqueous THF, followed by hydrolysis of the obtained saturated ester 3b (the yield of 1b with respect to 3a was 49% after crystallization). The 31P NMR signals of compounds 1 and 3 were observed at dP z 16 ppm, similarly to that of the parent Hdpf [3]. The presence of the ethen-1,2-diyl bridge in 1a and 3a was evidenced by a characteristic pair of doublets due to the AM spin system of the CH¼CH protons in the 1H NMR spectrum with 3JHH constants (z16 Hz) indicating trans arrangements and, further, by the corresponding 13C NMR signals at dC ca. 115 and 148 ppm. Reduction of the linking group resulted in replacement of these resonances with signals of the ethane-1,2-diyl linker at a higher field in both 1H and 13 C NMR spectra (dH 2.47 ppm for 1b (degenerate) and 2.38e2.50 ppm for 3b; dC z 24 and 35 ppm for both compounds). In their IR spectra, the acids displayed strong bands attributable to C¼O stretching vibrations at 1662 and 1691 cm1 for the conjugated derivative 1a and the non-conjugated “aliphatic” acid 1b, respectively. As in the case of trans-cinnamic acid [11], the n(C¼O) band in the spectrum of 1a was observed in the proximity of another strong band tentatively attributable to C¼C stretching vibrations (1613 cm1 in 1a). In addition, the different extents of conjugation in the pairs of analogous compounds 1a-1b and 3a-3b were clearly manifested in their color. While the propenoic derivatives 1a and 3a were intensely red, their saturated counterparts were deep yellow (N.B. the conversion of 3a to 3b could be easily followed visually via the color change). Accordingly, the UV-vis spectrum of 1a recorded in dichloromethane showed a strong band at 300 nm and a pair of
Fig. 1. UV-vis spectra of 1a (red) and 1b (blue) recorded for 0.1 mM (1.0 mM in the inset) dichloromethane solutions (optical path 1 cm). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
bands at 357 and 472 nm, whereas in the case of the saturated (non-conjugated) acid 1b, the low-energy absorption band appeared shifted to higher energies (443 nm) and was substantially weaker (Fig. 1). Crystallization of acids 1a and 1b proved to be rather difficult, especially when aimed at the preparation of X-ray quality single crystals. To obtain a pair of chemically analogous but better crystallizing derivatives allowing structure determination, phosphinocarboxylic acids 1 were converted to their corresponding phosphine sulfides 4 by treatment with elemental sulfur in acetone (Scheme 2). Thionation of the phosphine substituent was mainly indicated by a shift of the 31P NMR resonances to a lower field (dP 41e42) and, additionally, in the 13C NMR spectra through an increase in the JPC coupling constants [12]. The crystal structures of the phosphine sulfides are presented in Fig. 2, and the pertinent structural parameters are given in Table 1. Parameters describing the molecular geometry of 4a and 4b compare well with those reported for the structurally related acids, trans-2-[(2-ethoxycarbonyl)ferrocenyl]propenoic acid [13] and 3ferrocenylpropanoic acid [14], and also for 1,10 -bis(diphenylphosphinothioyl)ferrocene (dppfS2) [15]. The disubstituted ferrocene units in the structures of 4a and 4b assume positions near synclinal eclipsed (ideal value: t ¼ 72 [16]), and their cyclopentadienyls are tilted by less than approximately 3 . Because of conjugation, the entire polar pendant in 4a is located in the plane of its parent cyclopentadienyl ring, whereas in the structure of 4b, it extends
Scheme 2. Synthesis of phosphinocarboxylic acids 1 and their phosphine sulfides 4.
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located at the other cyclopentadienyl ring. The individual molecules in the crystals of both 4a and 4b associate into pairs via double O-H/O hydrogen bridges around the crystallographic inversion centers (i.e., cyclic R22(8) motifs in graph-set notation [18]; O1/O2 ¼ 2.624(2) Å for 4a, and 2.622(2) Å for 4b). In the case of 4b, the hydrogen-bonded dimers further assemble into infinite columnar stacks by intermolecular p/p interactions between inversion-related cyclopentadienyl rings C(1e5) at a centroid/centroid distance of 3.841(2) Å and an interplanar separation of 3.395(1) Å (Fig. 3). 2.2. Synthesis and characterization of Pd(II) phosphinocarboxylate complexes
Fig. 2. Views of the molecular structures of 4a (a) and 4b (b).
Table 1 Selected distances and angles for acids 4a and 4b (in Å and deg).a Parameter
4a
4b
P¼S P-Cb C1-C23 C23-C24 C24-C25 C25¼O1 C25-O2 S-P-Cc C-P-Cd C1-C23-C24 C23-C24-C25 C1-C23-C24-C25 O1-C25-O2 Fe-Cg1 Fe-Cg2 :Cp1,Cp2
1.9562(7) 1.797(2)-1.817(2) 1.447(3) 1.335(3) 1.459(3) 1.222(2) 1.323(2) 112.37(6)-115.63(6) 103.96(8)-106.01(8) 126.5(2) 120.3(2) 179.1(2) 122.6(2) 1.649(1) 1.6432(9) 2.9(1) 69.1(1)
1.9482(8) 1.786(2)-1.817(2) 1.497(3) 1.526(3) 1.486(4) 1.251(3) 1.293(3) 112.11(7)-115.07(7) 103.70(9)-106.52(9) 112.0(2) 113.8(2) 68.6(2) 122.9(2) 1.648(1) 1.636(1) 1.1(1) 65.5(2)
te
To prepare phosphinocarboxylate complexes from 1a and 1b and thus possibly employ both functional groups present in the structures of these donors (see Ref. [7]), we reacted the acids with the acetylacetonate (acac) complex [LNCPd(acac)] (5; LNC ¼ 2[(dimethylamino-kN)methyl]phenyl-kC1). Indeed, these reactions took the expected course, producing the anticipated phosphinocarboxylate complexes as a result of proton transfer between the acids and the acac ligand (Scheme 3). However, the natures of the crystallized products were substantially different. The reaction of acid 1a, featuring the less flexible unsaturated spacer, led to dimeric complex 6a, in which two chemically equivalent Pd(II) centers were bridged by the formed phosphinocarboxylate anion. Notably, analogous dipalladium complexes were obtained from 5 and acid B, whereas the similar reaction with ligand A led to a monopalladium chelate (Scheme 1) [7]. In contrast, the reaction involving 1b reproducibly afforded the coordination polymer catena-[(LNC)Pd(Ph2PfcCH2CH2CO2)]n (6b), whose one-dimensional polymeric chain propagated through an O,P-bridging phosphinocarboxylate ligand. Both complexes crystallized in solvated forms. The solubility of the discrete compound 6a was expectedly higher than that of the polymeric 6b, for which, however, a cleavage into smaller fragments (e.g., into cyclic oligomers or a monopalladium chelate) can be expected upon dissolution.
a Definition of the ring planes: Cp1 ¼ C(1e5), Cp2 ¼ C(6e1). Cg1 and Cg2 are the respective ring centroids. b The range of P-C(6,11,17) bond lengths. c The range of S-P-C(6,11,17) angles. d The range of C6-P-C(11,17) and C11-P-C17 angles. e Torsion angle C1-Cg1-Cg2-C6.
away from the ferrocene unit with the substituents at the central C23-C24 bond adopting a gauche conformation (cf. the torsion angles C1-C23-C24-C25 in Table 1) [17]. The conjugation can also be held responsible for a significant shortening of the bonds connecting the CH¼CH moiety in 4a to its functional substituents (viz., bonds C1-C23 and C24-25) as compared to the respective bonds in the structure of 4b featuring the saturated CH2CH2 bridge. The Ph2P(S) substituents in both structures are oriented with one phenyl group pointing above the ferrocene unit and the sulfur atoms directed away from the hydrocarbyl substituents, which are
Fig. 3. Principal intermolecular interactions in the crystal structure of 4b. The O2H90,,,O1 hydrogen bonds (black) and C23-H23,,,Ph interactions (red) are indicated by dotted lines and the p,,,p stacking interactions of cyclopentadienyl rings C(1e5) by blue double arrows. For clarity, only hydrogens involved in H-bonding interaction are shown. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. Section of the infinite coordination chain in the structure of 6b$2CHCl3. All hydrogen atoms are omitted for clarity.
Scheme 3. Reactions of Pd(II) acetylacetonate complex 5 with acids 1a and 1b.
The NMR spectra of 6a and 6b recorded in CD2Cl2 solutions suggested that the phosphine moieties remain coordinated in solution (dP z 30) and revealed only one set of resonances for both the phosphinocarboxylate ligand and the (LNC)Pd moiety. The signals of the LNC ligands were observed as 31P-coupled doublets (NMe2 and NCH2) and a set of second-order multiptets due to the C6H4 groups. The signals of the CH2CH2 linking groups were seen as distinct signals at dH 2.38 and 2.57 (those in 1a are degenerate), while the presence of the unsaturated bridge was manifested through a pair of doublets at dH 6.19 and 7.55. IR spectra recorded for the solid samples clearly confirmed deprotonation of the carboxyl groups (6a: 1581, 6b: 1579 cm1) and, in the case of 6a, also the presence of solvating ethyl acetate (1729 cm1 [19]). The structures of 6a$xAcOEt and 6b$2CHCl3 determined by single-crystal X-ray diffraction analysis are presented in Figs. 4 and 5, and the pertinent structural parameters are given in Tables 2 and 3. Compound 6a crystallizes extensively solvated with the solvent molecules disordered in structural voids left between the bulky complex molecules. The complex itself is a compact symmetrical dimer, but its molecules lack any external (crystallographic) symmetry. Geometric parameters describing the coordination
Table 2 Selected distances and angles for 6a$xAcOEt (in Å and deg).a Pd1-P1 Pd1-O22 Pd1-N1 Pd1-C31 P1-Pd1-O22 P1-Pd1-C31 N1-Pd1-O22 N1-Pd1-C31 C6-C23 C23-C24 C24-C25 C25¼O11 C25-O12 C6-C23-C24 C23-C24-C25 C6-C23-C24-C25 O11-C25-O12 C25-O12-Pd2 Fe1-Cg11 Fe1-Cg12 :Cp11,Cp12 t1b
2.2624(7) 2.113(2) 2.143(2) 2.000(3) 89.69(6) 97.60(7) 91.46(9) 81.43(9) 1.453(4) 1.322(3) 1.497(4) 1.236(3) 1.281(3) 125.2(2) 124.7(2) 179.6(2) 125.9(3) 116.9(2) 1.646(1) 1.646(1) 2.4(2) 137.7(2)
Pd2-P2 Pd2-O12 Pd2-N2 Pd2-C81 P2-Pd2-O12 P2-Pd2-C81 N2-Pd2-O12 N2-Pd2-C81 C56-C73 C73-C74 C74-C75 C75¼O21 C75-O22 C56-C73-C74 C73-C74-C75 C56-C73-C74-C75 O21-C75-O22 C75-O22-Pd1 Fe2-Cg21 Fe2-Cg22 :Cp21,Cp22 t2b
2.262(1) 2.114(2) 2.151(2) 1.997(3) 92.61(6) 94.63(8) 91.66(8) 81.18(9) 1.455(4) 1.329(4) 1.504(4) 1.250(3) 1.250(4) 125.7(3) 123.7(3) 179.3(2) 126.8(3) 117.3(2) 1.648(1) 1.649(1) 3.3(1) 138.8(2)
a Definition of the ring planes: Cp11 ¼ C(1e5), Cp12 ¼ C(6e10), Cp21 ¼ C(51e55), Cp22 ¼ C(56e60). Cg11, Cg12, C21 and Cg22 are the corresponding ring centroids. b Torsion angles C1-Cg11-Cg12-C6 (t1) and C51-Cg21-Cg22-C56 (t2).
Fig. 4. View of the complex molecule in the structure of 6a$xAcOEt. The hydrogen atoms are omitted to avoid complicating the figure.
P. Stepnicka et al. / Journal of Organometallic Chemistry 846 (2017) 193e200 Table 3 Selected interatomic distances and angles for 6b$2CHCl3 (in Å and deg).a Distances Pd-P Pd-O2i Pd-N Pd-C31 C6-C23 C23-C24 C24-C25 C25¼O1 C25-O2 Fe-Cg1 Fe-Cg2
P-Pd-O2i P-Pd-C31 N-Pd-O2i N-Pd-C31 C6-C23-C24 C23-C24-C25 C6-C23-C24-C25 O1-C25-O2 C25-O2-Pdii :Cp1,Cp2
tb
4. Experimental 4.1. Materials and methods
Angles 2.2573(5) 2.108(2) 2.153(2) 1.999(2) 1.504(3) 1.519(3) 1.532(3) 1.240(2) 1.278(2) 1.647(1) 1.655(1)
197
94.28(4) 95.01(6) 88.53(6) 82.78(7) 116.0(2) 112.4(2) 171.4(2) 125.7(2) 118.5(1) 4.6(1) 77.3(1)
a
Definition of the ring planes: Cp1 ¼ C(1e5), Cp2 ¼ C(6e1). Cg1 and Cg2 are the respective ring centroids). Symmetry operations used to generate equivalent positions: i ¼ 1x, 1/2 þ y, 3/2z, ii ¼ 1x, 1/2 þ y, 3/2z. b Torsion angle C1-Cg1-Cg2-C6.
environment of the Pd(II) center compare well to those reported for the analogous phosphinocarboxylate complexes obtained from ligands A and B (see Scheme 1) [7]. The Pd center has a {PONC} donor set with trans-PN arrangement with very similar Pdedonor distances for both structurally independent Pd atoms. A difference can be found among the interligand angles because the P2-Pd2-O12 is slightly more opened and the adjacent P2-Pd2-C81 is slightly more acute (both by ca. 3 ) than the corresponding angles pertaining to Pd1, which can, however, be ascribed to steric factors. The propanoate chains in the structure of 6a remain in the plane of their bonding cyclopentadienyl rings, but the ferrocene substituents assume more distant positions than in 4a (compare the t angles in Tables 1 and 2) so as to allow for bridging coordination. Furthermore, deprotonation and coordination of the carboxyl group diminished the difference between the individual C-O distances compared with those in 4a. The crystal structure of 6b,2CHCl3 confirms the polymeric nature of this compound. The anions resulting through deprotonation of acid 1b bridge equivalent (LNC)Pd fragments related by a crystallographic two-fold screw axis into an infinite zig-zag chain oriented parallel to the b axis and the twisted square-planar geometry around the Pd atom is very similar to that in 6a. The conformation of the disubstituted ferrocene unit in the structure of 6b is close to synclinal eclipsed with the carboxylate pendant extending to the side of the ferrocene unit, nearly perpendicularly with respect to the C1-P bond.
3. Conclusion The newly prepared phosphinocarboxylic acids 1a and 1b reacted with complex 5 similarly to how Hdpf and compounds A and B do, providing Pd(II) phosphinocarboxylate complexes. While 1a gave rise to a P,O-bridged dipalladium(II) complex 6a (analogous to that obtained from compound B), the reaction involving 1b produced one-dimensional coordination polymer 6b, which propagates through bridging phosphinocarboxylate ligands. The selective formation of these particular products appears to be the result of a subtle interplay between solubility and crystallization phenomena in addition to equilibria of various forms such as presumed monopalladium chelates, dipalladium dimers and other oligomeric species, rather than real changes in the reaction course imparted by changes in the ligand structure. Such a behavior is clearly enabled by hemilabile coordination of the phosphinocarboxylate ligands, whose donor atoms form dative bonds to the soft palladium(II) ions of different strength.
All syntheses were performed under an argon atmosphere with the exclusion of direct daylight. Toluene was dried over potassium metal and distilled under argon. THF and acetone were distilled from potassium/benzophenone ketyl and from anhydrous K2CO3, respectively. Chloroform was dried over calcium hydride and distilled under an argon atmosphere. Compounds 2 [8] and 5 [20] were prepared according to reported procedures. Other chemicals (Sigma-Aldrich, Fluka) and solvents for crystallizations (Lach-Ner, Czech Republic; analytical grade) were used without any additional purification. NMR spectra were recorded on a Varian Unity Inova spectrometer (1H, 399.95; 13C, 100.58; 31P, 161.90 MHz) at 25 C. Chemical shifts (d/ppm) are given relative to internal tetramethylsilane (13C and 1H) or to external 85% aqueous H3PO4 (31P). In addition to the standard notation of signal multiplicity, vt and vq are used to denote virtual triplets and quartets arising from AA0 BB0 and AA0 BB0 X spin systems of the ferrocene cyclopentadienyls (A, B ¼ 1H, X ¼ 31P). IR spectra were measured with an FT IR Nicolet Magna 650 instrument in Nujol mulls. Electron impact (EI) and electrospray ionization (ESI) mass spectra were obtained on a VG Zab SEQ and a Bruker Esquire 3000 spectrometer, respectively. 4.2. Synthesis of (E)-ethyl 3-[10 -(diphenylphosphino)ferrocenyl]propenoate (3a) Triethyl phosphonoacetate (3.0 mL, 15 mmol) was added dropwise to a stirred suspension of sodium hydride (0.242 g, 10 mmol) in toluene (15 mL), whereupon the solid hydride dissolved rapidly and with vigorous effervescence to give a clear, colorless solution. After stirring for another 15 min at 0 C, a solution of aldehyde 2 (2.003 g, 5.00 mmol) in toluene (35 mL) was introduced, and the reaction flask was transferred to an oil bath maintained at 60 C. The reaction mixture was stirred overnight (the initial orange brown color due to the aldehyde changed quickly to deep red) before being cooled to room temperature. Then, the mixture was diluted with diethyl ether (ca. 25 mL; insoluble brown gummy material was discarded), washed successively with water and saturated aqueous NaCl solution and finally dried over anhydrous magnesium sulfate. The volatiles were removed under reduced pressure, and the dark red oily residue was purified by column chromatography (silica gel, hexaneeether 1:2). The first dark red band was collected and evaporated under vacuum (1 h at 60 C/ 1 Torr) to afford 3a as a deep red viscous oil. Yield: 2.198 g (93%). 1 H NMR (CDCl3): d 1.32 (t, 3JHH ¼ 7.1 Hz, 3 H, OCH2Me), 4.07 (vq, 0 J ¼ 1.9 Hz, 2 H, fc), 4.20 (q, 3JHH ¼ 7.1 Hz, 2 H, OCH2), 4.28 (vt, J0 ¼ 1.9 Hz, 2 H, fc), 4.36, 4.37 (2 vt, J0 ¼ 1.8 Hz, 2 H, fc), 5.93 (d, 3 JHH ¼ 15.8 Hz, 1 H, ¼CH(a)), 7.28e7.39 (m, 10 H, PPh2), 7.37 (d, 3 JHH ¼ 15.8 Hz, 1 H, ¼CH(b)). 13C{1H} NMR (CDCl3): d 14.35 (OCH2Me), 60.15 (OCH2), 69.42, 72.08, 72.79 (d, JPC ¼ 4 Hz), 74.15 (d, JPC ¼ 15 Hz) (4 CH of fc); 77.41 (d, 1JPC ¼ 8 Hz, CP of fc), 79.31 (CCH of fc), 115.65 (¼CH(a)), 128.19 (d, JPC ¼ 7 Hz), 128.63, 133.42 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 138.63 (d, 1JPC ¼ 10 Hz, Cipso of PPh2), 144.74 (¼CH(b)), 167.02 (CO2H). 31P{1H} NMR (CDCl3): d 16.9 (s). EI MS: m/z (relative abundance) 469 (32), 468 (100, Mþ$), 439 (4, [M Et]þ), 395 (14, [M Et CO2]þ), 370 (68, [FcPPh2]þ$), 321 (10), 293 (16), 226 (7), 171 (7), 170 (5), 121 (6, [FeC5H5]þ), 83 (10). EI HR MS calc. for C27H56 25FeO2P: 468.0942, found 468.0932. 4.3. Synthesis of ethyl 3-[10 -(diphenylphosphino)ferrocenyl]propanoate (3b) p-Toluenesulfonyl hydrazide (2.79 g, 15 mmol) was added to 3a
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(1.409 g, 3.0 mmol) dissolved in dry THF (30 mL) followed by an aqueous solution of sodium acetate (1.27 g, 15 mmol in 30 mL). The resulting heterogeneous mixture was refluxed overnight (22 h; the original burgundy red color changed to orange yellow) and then cooled to room temperature and treated with saturated aqueous K2CO3 solution under vigorous stirring for 30 min. The organic layer was separated, washed twice with brine and dried over MgSO4. The solvent was removed under vacuum, and the residue was purified by column chromatography (silica gel, hexaneeether 1:1). Evaporation of the major yellow orange band (a small forerun was discarded) yielded the propanoate ester 3b as an amber oil, which solidified upon standing at 4 C. Yield: 1.142 g (81%). 1 H NMR (CDCl3): d 1.25 (t, 3JHH ¼ 7.1 Hz, 3 H, OCH2Me), 2.38e2.50 (m, 4 H, CH2CH2), 3.95, 4.00 (2 vt, J0 ¼ 1.8 Hz, 2 H) and 4.04 (vq, J0 ¼ 1.9 Hz, 2 H) (3 CH of fc); 4.12 (q, 3JHH ¼ 7.1 Hz, 2 H, OCH2), 4.32 (vt, J0 ¼ 1.9 Hz, 2 H, fc); 7.27e7.40 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 14.26 (OCH2Me), 24.54 and 35.69 (CH2CH2); 60.37 (OCH2), 68.70, 69.08, 71.53 (d, JPC ¼ 4 Hz), 73.41 (d, JPC ¼ 15 Hz) (4 CH of fc); 75.71 (br s, CP of fc), 88.11 (CCH of fc), 128.10 (d, JPC ¼ 7 Hz), 128.45, 133.49 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 139.16 (br d, 1 JPC ¼ 10 Hz, Cipso of PPh2), 173.03 (CO2H). 31P{1H} NMR (CDCl3): d 16.2 (s). EI MS: m/z (relative abundance) 471 (31), 470 (100, Mþ$), 425 (5), 386 (12), 370 (32, [FcPPh2]þ$), 293 (11), 226 (6), 221 (7), 212 (19),171 (11),170 (7), 147 (6), 121 (5, [FeC5H5]þ), 91 (5). EI HR MS calc. for C27H56 27FeO2P: 470.1098, found 470.1085. 4.4. Synthesis of (E)-3-[10 -(diphenylphosphino)ferrocenyl]propenoic acid (1a) A solution of 3a (2.106 g, 4.50 mmol) in THF (30 mL) was mixed with methanol (30 mL) and aqueous KOH (30 mL 3 M), and the resulting clear solution was refluxed for 6 h. The mixture was poured onto crushed ice (ca. 100 g) and strongly acidified with 85% aqueous H3PO4. The organic solvents were removed under vacuum, and the residue was extracted with dichloromethane (several times). The combined organic layers were washed with saturated aqueous NaCl, dried over MgSO4, and filtered through a pad of silica gel, which was subsequently eluted with dichloromethaneemethanol (95:5). The eluate was evaporated under vacuum to leave a residue, which was immediately dissolved in hot ethyl acetate; the solution was crystallized at room temperature and then at 18 C. The solid formed was filtered off, washed with hexane and dried in air to give analytically pure 1a as deep red needles. Yield: 1.445 g (73%). M.p. 176e177 C (ethyl acetate). 1H NMR (CDCl3): d 4.09 (vq, J0 ¼ 1.9 Hz, 2 H), 4.34, 4.38, 4.40 (3 vt, J0 ¼ 1.9 Hz, 2 H) (4 CH of fc); 5.92 (d, 3JHH ¼ 15.6 Hz, 1 H, ¼CH(a)), 7.29e7.38 (m, 10 H, PPh2), 7.47 (d, 3JHH ¼ 15.6 Hz, 1 H, ¼CH(b)). 13C{1H} NMR (CDCl3): d 69.76, 72.51, 72.82 (d, JPC ¼ 4 Hz), 74.29 (d, JPC ¼ 15 Hz) (4 CH of fc); 77.69 (d, 1JPC ¼ 8 Hz, CP of fc), 78.66 (CCH of fc), 114.51 (¼CH(a)), 128.22 (d, JPC ¼ 7 Hz), 128.70, 133.41 (d, JPC ¼ 20 Hz) (3 CH of PPh2); 138.53 (d, 1JPC ¼ 9 Hz, Cipso of PPh2), 147.74 (¼CH(b)), 172.39 (CO2H). 31P{1H} NMR (CDCl3): d 17.0 (s). IR (DRIFTS, KBr): nmax 1662 (vs), 1613 (vs), n(C¼O) and n(C¼C); 1474 (m), 1430 (m), 1308 (s), 1280 (m), 1246 (m), 1227 (m), 1160 (m), 1046 (m), 1032 (m), 978 (m), 867 (m), 834 (m), 818 (m), 747 (m), 741 (m), 696 (s), 657 (m), 500 (s), 479 (m) cm1. UV-vis (CH2Cl2): lmax 300 nm (ε 14770 M1 cm1), 357 nm (ε 1890 M1 cm1), 472 nm (ε 1070 M1 cm1). Anal. Calc. for C25H21FeO2P: C 68.20, H 4.81%. Found: C 68.11, H 4.76%. 4.5. Synthesis of 3-[10 -(diphenylphosphino)ferrocenyl]propanoic acid (1b) Hydrolysis of 3b was performed as described in detail above. A
mixture obtained by mixing a solution of 3b (1.177 g, 2.5 mmol) in THF (25 mL), methanol (25 mL) and aqueous KOH solution (25 mL 3 M) was refluxed for 6 h and then poured onto ice (ca. 100 g). The mixture was acidified with 85% aqueous H3PO4, the organic solvents were removed under vacuum, and the residue was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and filtered through a pad of silica gel (elution with dichloromethane). The eluate was evaporated under vacuum, the residue was dissolved in hot ethyl acetate, and the solution was crystallized by addition of hexane and standing at 18 C overnight. The separated crystalline solid was filtered off, washed with hexane and dried in air to give 1b as fine, bright yellow needles. Yield: 0.679 g (61%). M.p. 129e130 C (ethyl acetate-hexane). 1H NMR (CDCl3): d 2.47 (s, 4 H, CH2CH2), 3.97, 4.01 (2 vt, J0 ¼ 1.8 Hz, 2 H), 4.05 (vq, J0 ¼ 1.8 Hz, 2 H), 4.33 (vt, J0 ¼ 1.8 Hz, 2 H) (4 CH of fc); 7.28e7.40 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 24.19 and 35.29 (CH2CH2); 68.79, 69.15, 71.64 (d, JPC ¼ 4 Hz), 73.47 (d, JPC ¼ 15 Hz) (4 CH of fc); 75.01 (d, 1JPC z 2 Hz, CP of fc), 87.89 (CCH of fc), 128.18 (d, JPC ¼ 7 Hz), 128.72, 133.46 (d, JPC ¼ 19 Hz) (3 CH of PPh2); 138.27 (d, 1JPC ¼ 5 Hz, Cipso of PPh2), 178.55 (CO2H). 31P{1H} NMR (CDCl3): d 16.4 (s). IR (DRIFTS): nmax 1691 (vs) n(C¼O); 1475 (m), 1432 (s), 1308 (s), 1227 (m), 1192 (m), 1161 (m), 1094 (m), 1041 (w), 1027 (m), 951 (br m), ca. 830 (m composite), 749 (s), 741 (s), 697 (s), 634 (m), 501 (s), 476 (s), 459 (m) cm1. UV-vis (CH2Cl2): lmax 443 nm (ε 162 M1 cm1). Anal. Calc. for C25H23FeO2P: C 67.89, H 5.24%. Found: C 67.67, H 5.16%. 4.6. Synthesis of (E)-3-[10 -(diphenylphosphinothioyl)ferrocenyl]propenoic acid (4a) A solution of acid 1a (88.2 mg, 0.20 mmol) and elemental sulfur (8.0 mg, 0.25 mmol) in acetone (5 mL) was stirred at room temperature overnight and then evaporated to dryness. The residue was extracted with hot ethyl acetate, and the product was crystallized by addition of hexane and cooling to 18 C overnight. The separated material was filtered off, washed with a small quantity of hexane and dried in air to give 4a as a burgundy red, crystalline solid. Yield: 80.7 mg (85%). 1 H NMR (CDCl3): d 4.42 (vq, J0 ¼ 1.9 Hz, 2 H), 4.47, 4.50 (2 vt, J0 ¼ 1.9 Hz, 2 H), 4.51 (vq, J0 ¼ 1.9 Hz, 2 H) (4 CH of fc); 5.88 (d, 3 JHH ¼ 15.7 Hz, 1 H, ¼CH(a)), 7.36 (d, 3JHH ¼ 15.7 Hz, 1 H, ¼CH(b)), 7.40e7.76 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 70.46, 73.37, 73.66 (d, JPC ¼ 10 Hz), 74.32 (d, JPC ¼ 12 Hz) (4 CH of fc); 76.69 (d, 1 JPC ¼ 96 Hz, CP of fc), 79.43 (CCH of fc), 115.38 (¼CH(a)), 128.31 (d, JPC ¼ 12 Hz), 131.46 (d, JPC z 4 Hz), 131.54 (d, JPC ¼ 11 Hz) (3 CH of PPh2); 134.10 (d, 1JPC ¼ 87 Hz, Cipso of PPh2), 146.78 (¼CH(b)), 171.91 (CO2H). 31P{1H} NMR (CDCl3): d þ41.4 (s). EI MS, m/z (relative abundance): 472 (82, Mþ$), 440 (8, [M S]þ$), 428 (5, [M CO2]þ$), 402 (5), 368 (6), 354 (23), 337 (100, [M C5H4CHCHCO2H]þ). EI HR MS calc. for C25H56 21FeO2PS: 472.0349, found 472.0331. 4.7. Synthesis of 3-[10 -(diphenylphosphinothioyl)ferrocenyl]-
propanoic acid (4b) Starting with 1b (88.7 mg, 0.20 mmol) and sulfur (8.0 mg, 0.25 mmol), the same procedure used for the synthesis of 4a (see Section 4.6) provided 4b as fine yellow needles. Yield: 90.2 mg (95%). 1 H NMR (CDCl3): d 2.46 (s, 4 H, CH2CH2), 4.04, 4.14 (2 vt, J0 ¼ 1.8 Hz, 2 H), 4.38, 4.46 (2 vq, J0 ¼ 1.8 Hz, 2 H) (4 CH of fc); 7.38e7.76 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 24.04 and 35.07 (CH2CH2); 69.66, 70.07, 72.48 (d, JPC ¼ 10 Hz), 73.53 (d, JPC ¼ 13 Hz) (4 CH of fc); 75.10 (d, 1JPC ¼ 99 Hz, CP of fc), 88.69 (CCH of fc),
P. Stepnicka et al. / Journal of Organometallic Chemistry 846 (2017) 193e200
128.19 (d, JPC ¼ 13 Hz), 131.21 (d, JPC ¼ 3 Hz), 131.61 (d, JPC ¼ 11 Hz) (3 CH of PPh2); 134.57 (d, 1JPC ¼ 87 Hz, Cipso of PPh2), 177.75 (CO2H). 31P{1H} NMR (CDCl3): d þ42.1 (s). Anal. Calc. for C25H23FeO2PS: C 63.30, H 4.89%. Found: C 63.27, H 4.82%. 4.8. Preparation of complex 6a Acid 1a (44.0 mg, 0.10 mmol) and complex 5 (34.0 mg, 0.10 mmol) were dissolved in chloroform (1 mL), and the resulting mixture was stirred for 1 h, whereupon it deposited an orange precipitate. Then, the reaction mixture was evaporated under vacuum, leaving an orange residue that was taken up with dichloromethane (ca. 5 mL) with sonication and gentle heating; the extract was filtered directly into warm ethyl acetate (20 mL). Slow cooling to room temperature and then to 4 C resulted in the separation of a crystalline product, which was isolated by suction, washed with ethyl acetate and pentane, and dried under vacuum to give 6a$4AcOEt as an orange crystalline solid (needles). Yield: 58.2 mg (68%). Crystals used for structure determination were obtained from hot ethyl acetate. 1 H NMR (CD2Cl2): d 2.76 (d, 4JPH ¼ 2.6 Hz, 6 H, NMe2), ca. 4.1 (very br s, 4 H), 4.19 (br s, 2 H), 4.92 (br s, 4 H) (4 CH of fc and CH2N), 6.19 (d, 3JHH ¼ 15.7 Hz, 1 H, CH¼), 6.24e6.31 (m, 2 H, 2 CH of C6H4), 6.73e6.77 (m, 1 H, CH of C6H4), 6.97 (br dd, J1 ¼ 7.6, J2 ¼ 1.0 Hz, 1 H, CH in C6H4), 7.30e7.37 (br m, 4 H, PPh2), 7.40e7.46 (br m, 2 H, PPh2), 7.55 (d, 3JHH ¼ 15.7 Hz, 1 H, CH¼), 7.64 (br s, 4 H, PPh2). 31P{1H} NMR (CD2Cl2): d 30.6 (s). IR (Nujol): nmax 3369 (br w), 3047 (m), 1729 (s), 1645 (m), 1581 (s), 1353 (vs), 1339 (s), 1306 (m), 1279 (m), 1246 (s), 1183 (w), 1168 (m), 1100 (m), 1046 (m), 1024 (m), 994 (w), 974 (m), 867 (vw), 844 (m), 827 (m), 780 (vw), 745 (s), 710 (w), 696 (m), 681 (m), 631 (w), 541 (m), 525 (m), 505 (s), 471 (m) cm1. ESIþ MS: m/z 680 ([Pd(C6H4CH2NMe2)(Ph2PfcCH¼ CHCO2) þ H]þ). Anal. Calc. for C68H64Fe2N2O4P2Pd2$4AcOEt (1712.07): C 58.93, H 5.65, N 1.64%. Found: C 58.87, H 5.26, N 1.75%. 4.9. Preparation of complex 6b Acid 1b (44.2 mg, 0.10 mmol) and complex 5 (34.0 mg, 0.1 mmol) were dissolved in chloroform (1 mL). The reaction mixture was stirred for 1 h and then filtered through a PTFE syringe filter (pore size 0.45 mm) into a test tube. The solution was layered with 0.5 mL of chloroform used to rinse the reaction vessel and
199
0.5 mL of pure chloroform and then cooled to 4 C. The cooled solution was layered with a chloroformemethyl t-butyl ether mixture (1 þ 1 mL) and then methyl t-butyl ether (ca. 20 mL). The test tube was stoppered and set aside for crystallization at room temperature. The solid, which separated after several days, was filtered off, washed with methyl t-butyl ether and dried under vacuum to afford solvated complex 6b. Yield of 6b,0.45CHCl3: 49.5 mg (67%). Crystals suitable for X-ray diffraction analysis were selected from the reaction batch. 1 H NMR (CD2Cl2): d 2.38 (br t, 3JHH ¼ 6.1 Hz, 2 H, CH2 of CH2CH2CO2), 2.57 (br t, 3JHH ¼ 5.4 Hz, 2 H, CH2 of CH2CH2CO2), 2.75 (d, 4JPH ¼ 2.8 Hz, 6 H, NMe2), 3.64 (br s, 2 H, CH of fc), 3.89 (br s, 2 H, CH of fc), 3.99 (br d, 4JPH ¼ 1.8 Hz, 2 H, NCH2), 4.48 (br s, 2 H, CH of fc), 4.72 (br s, 2 H, CH of fc), 5.91 (br ddd, J1 ¼ 7.8, J2 ¼ 5.5, J3 ¼ 1.1 Hz, 1 H, CH of C6H4), 6.24 (br td, J1 ¼ 7.6, J2 ¼ 1.5 Hz, 1 H, CH of C6H4), 6.68 (br td, J1 ¼ 7.3, J2 ¼ 1.2 Hz, 1 H, CH of C6H4), 6.86 (br dd, J1 ¼ 7.4, J2 ¼ 1.5 Hz, 1 H, CH of C6H4), 7.68e7.86 (br s, 4 H, PPh2), 7.32e7.42 (br m, 6 H, PPh2). 31P{1H} NMR (CD2Cl2): d 29.6 (s). IR (Nujol): nmax 3048 (m), 2210 (m), 1579 (vs), 1396 (m), 1392 (m), 1326 (m), 1304 (w), 1243 (m), 1183 (w), 1164 (m), 1101 (m), 1064 (w), 1035 (m), 996 (w), 975 (w), 936 (w), 847 (m), 837 (m), 815 (w), 783 (vw), 750 (s), 740 (s), 733 (m), 727 (m), 696 (s), 662 (w), 640 (w), 543 (m), 522 (m), 503 (m), 493 (m), 473 (m) cm1. ESIþ MS: m/z 682 ([Pd(C6H4CH2NMe2)(Ph2PfcCH2CH2CO2) þ H]þ). Anal. Calc. for C34H34FeNO2PPd$0.45CHCl3 (735.56): C 58.25, H 4.72, N 1.90%. Found: C 55.87, H 5.12, N 1.70%. 4.10. X-ray crystallography X-ray quality crystals were either selected directly from the reaction batch (4b: yellow needle, 0.05 0.10 0.43 mm3; 6b$2CHCl3: orange prism, 0.04 0.21 0.28 mm3) or, alternatively, grown by recrystallization from chloroformehexane (4a: ruby red prism, 0.18 0.25 0.30 mm3) and warm ethyl acetate (6a$xAcOEt: orange-red prism, 0.04 0.11 0.28 mm3). Full-set diffraction data (qmax ¼ 27.5 , data completeness > 99%) were collected on a Nonius KappaCCD diffractometer (4a and 4b) or a Bruker D8 VENTURE Kappa Duo diffractometer with a PHOTON100 detector and an ImS micro-focus X-ray source (6a and 6b), both equipped with a Cryostream Cooler (Oxford Cryosystems) using Mo Ka radiation (l ¼ 0.71073 Å) at 150(2) K. The structures were solved by direct methods (SIR97 for 4a/4b
Table 4 Summary of the relevant crystallographic data and structure refinement parameters. Compound
4a
4b
6a$xAcOEt
6b$2CHCl3
Formula M (g mol1) Crystal system Space group a (Å) b(Å) c (Å) a ( ) b ( ) g ( ) Z V (Å3) Dcalc (g mL1) Collected diffrns, Rint (%)a Unique/observedb diffrns R (obsd data) (%)c R, wR (all data)(%)c Dr (e Å3)
C25H23FeO2PS 472.30 monoclinic P21/n (no.14) 14.8629(3) 9.9182(2) 15.7146(3)
C25H23FeO2PS 474.31 triclinic P1 (no. 2) 8.7530(2) 9.3560(3) 13.6180(5) 100.447(2) 90.333(2) 97.398(2) 2 1087.12(6) 1.449 21133, 4.30 5023/3801 3.69 6.05, 8.43 0.34, 0.38
C68H64Fe2N2O4P2Pd2$C4H8O2d 1447.75d monoclinic C2/c (no. 15) 42.196(2) 10.7797(6) 34.949(2)
C34H34FeNO2PPd$2CHCl3 920.58 monoclinic P21/c (no.14) 14.3586(7) 13.8101(6) 18.8254(9)
113.632(2)
93.250(2)
8 14564(1) 1.321d 98124, 2.56 14323/11939 2.95 4.05, 7.13 0.91, 0.63
4 3727.0(3) 1.641 74422, 1.63 8559/7532 2.51 3.23, 6.32 1.06, 0.69
a b c d
112.104(1) 4 2146.28(7) 1.462 29659, 3.20 4912/4163 3.14 4.05, 8.09 0.37, 0.36
Rint ¼ SrF2o F2o(mean)r/SF2o, where F2o(mean) stands for an average intensity of symmetry-equivalent diffractions. Diffractions with Io > 2s(Io). R ¼ SrrFor rFcrr/SrFor, wR ¼ [S{w(F2o F2c )2}/S w(F2o)2]1/2. These values are affected by PLATON/SQUEEZE.
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[21] and XT2014 for solvated 6a/6b [22]) and then refined by a fullmatrix least squares procedure based on F2 (SHELXL97 for 4a/4b, and SHELXL-2014 for solvated 6a/6b [23]). The non-hydrogen atoms were refined with anisotropic thermal motion parameters. Carboxylic hydrogen atoms in the structures of 4a and 4b were located on difference Fourier maps, and their positions were freely refined with Uiso(H) assigned to 1.2 Ueq(O2). All other hydrogen atoms were included in their calculated positions and refined using the “riding model”. Some of the solvent molecules present in the structure of extensively solvated 6a$xAcOEt were disordered. Hence, their contribution to the overall scattering was removed using the SQUEEZE routine [24] in PLATON [25], and the structure was refined against the generated data. Relevant crystallographic data, data collection and refinement parameters are presented in Table 4. All geometric calculations were performed with a recent version of the PLATON program [25], which was also used to prepare the structural diagrams. CCDC 1549289 (4a), 1549290 (4b), 1549291 (6a$xAcOEt), and 1549292 (6b$2CHCl3) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via the Internet at http://www.ccdc.cam.ac.uk/ Acknowledgments
[3] [4] [5] [6]
[7] [8] [9]
[10] [11] [12] [13]
[14] [15]
[16] [17]
Research leading to the results reported in this paper received financial support from the Czech Science Foundation (project no. 15-11571S).
[18]
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