Coordination Behavior of the 1, 2, 3-Triphosphaferrocene [Cp

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Organometallics 2009, 28, 1075–1081

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Coordination Behavior of the 1,2,3-Triphosphaferrocene [Cp′′′Fe(η5-P3C2(H)Ph)] with Organometallic Moieties Shining Deng,† Christoph Schwarzmaier,† Manfred Zabel,† John F. Nixon,‡ Alexey Y. Timoshkin,§ and Manfred Scheer*,† Institut fu¨r Anorganische Chemie, UniVersita¨t Regensburg, 93040 Regensburg, Germany, Chemistry Department, School of Life Sciences, UniVersity of Sussex, Falmer, Brighton, BN19QJ, Sussex, United Kingdom, and Department of Chemistry, St. Petersburg State UniVersity, UniVersity pr. 26, 198504 Old Peterhoff, St. Petersburg, Russian Federation ReceiVed NoVember 24, 2008

The reaction of the 1,2,3-triphosphaferrocene [Cp′′′Fe(η5-P3C2(H)Ph)] (1) with the Lewis acidic complex [PtCl2(PEt3)]2 yields the monosubstituted derivative [Cp′′′Fe(η5-P3C2(H)Ph){PtCl2(PEt3)}] (2), in which the Pt moiety is located at the P atom adjacent to the C(H) group of the cyclo-P3C2 ring. Using an excess of the Pt complex no multiple substitution occurs. In contrast, using [W(CO)5] units as Lewis acids results in mono-, di-, and tricoordination at the cyclo-P3C2 ring. The products, [Cp′′′Fe(η5P3C2(H)Ph){W(CO)5}n] (n ) 1 (3), 2 (4), 3 (5)), have all been spectroscopically characterized, and the substitution patterns of the experimentally found (mono- and disubstituted) isomers are found to be in accordance with the energetically favored derivatives calculated by DFT methods. For these structures the energetically favored rotational conformers have also been calculated. The energetically favored 2,3coordinated isomer 4b could be crystallized, and its structure and that of the tricoordinated derivative 5 were determined by X-ray diffraction methods. Introduction Phosphaferrocenes are an interesting class of compounds because they combine fundamental aspects as well as applied research.1 Within this class of compounds triphosphaferrocenes are long-known compounds typified by the 1,2,4-triphosphaferrocene derivatives A (Scheme 1).2 In contrast, not long ago the first 1,2,3-substituted derivatives B (R ) R′ ) Ph) were synthesized.3 Recently, we succeeded in the synthesis of a new, sterically less crowded type B derivative [Cp′′′Fe(η5P3C2(H)Ph)] (Cp′′′ ) η5-C5H2tBu3) (1).4 The coordination chemistry behavior of type A compounds was studied by the groups of Bartsch5,6 and Nixon7 (Scheme 2). By reacting [CpRFe(η5-P3C2tBu2)] (CpR ) Cp, Cp*) with * To whom correspondence should be addressed. Tel: +49 941 9434441. Fax: +49 941 9434439. E-mail: [email protected]. † Universita¨t Regensburg. ‡ University of Sussex. § St. Petersburg State University. (1) Mathey, F. In Phosphorus-Carbon Heterocyclic Chemistry: The Rise of a New Domain; Mathey, F., Ed.; Elsevier: Oxford, 2001; p 767. Cornils, B.; Herrmann, W. A., Eds. Homogeneous Catalysis with Organometallic Compounds; VCH: Weinheim, 1996; Vols. 1 and 2. Dillon, K. B.; Mathey, F.; Nixon, J. F. In Phosphorus: The Carbon Copy; Wiley: Chichester, 1998 Mathey, F. Angew. Chem. 2003, 115, 1617; Angew. Chem., Int. Ed. 2003, 42, 1578. Mathey, F. Coord. Chem. ReV. 1994, 137, 1. (2) (a) Mu¨ller, C.; Bartsch, R.; Fischer, A.; Jones, P. G.; Schmutzler, R. J. Organomet. Chem. 1996, 512, 141. (b) Bartsch, R.; Hitchcock, P. B.; Nixon, J. F. J. Organomet. Chem. 1988, 340, C37. (c) Bartsch, R.; Hichcock, P. B.; Nixon, J. F. J. Chem. Soc., Chem. Commun. 1987, 1146. (d) Mu¨ller, C.; Bartsch, R.; Fischer, A.; Jones, P. G. J. Organomet. Chem. 1993, 435, C16. (3) Scherer, O. J.; Hilt, T.; Wolmersha¨user, G. Angew. Chem. 2000, 112, 1484; Angew. Chem., Int. Ed. 2000, 39, 1425. For the 1,2,3,4 derivative cf.: Scheer, M.; Deng, S.; Scherer, O. J.; Sierka, M. Angew. Chem. 2005, 117, 3821; Angew. Chem., Int. Ed. 2005, 44, 3755. (4) Deng, S.; Schwarzmaier, Ch.; Eichhorn, Ch.; Scherer, O. J.; Wolmersha¨user, G.; Zabel, M.; Scheer, M. Chem. Commun. 2008, 4064. (5) Mu¨ller, C.; Bartsch, R.; Fischer, A.; Jones, P. G.; Schmutzler, R. J. Organomet. Chem. 1996, 512, 141.

Scheme 1. Types of Triphosphaferrocenes

Scheme 2. Mono- and Disubstituted 1,2,4-Triphosphaferrocene Complexes

metal carbonyl fragments the monosubstituted products A-1 are obtained. The 31P NMR spectrum of the Cp*-containing complex has been interpreted as the M(CO)5 fragment (M ) Cr, Mo, W) undergoing a 1,2-shift between the two adjacent P atoms of the η5-P3C2tBu2 ring in solution.5,6 However, in the Cpsubstituted derivative [CpFe(η5-P3C2tBu2){W(CO)5}]7 a rigid structure in solution is described, revealing a W,P coupling constant, whereas in the corresponding Cp*-substituted deriva(6) Mu¨ller, C.; Bartsch, R.; Fischer, A.; Jones, P. G. Polyhedron 1993, 12, 1383. (7) Bartsch, R.; Hitchcock, P. B.; Nixon, J. F. J. Organomet. Chem. 1988, 340, C37.

10.1021/om801118k CCC: $40.75  2009 American Chemical Society Publication on Web 01/29/2009

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tives even at low temperature (-35 °C) no such coupling was resolved.6 Interestingly, in all of these reactions it has been found that only one metal carbonyl moiety is able to coordinate to type A complexes. Additionally, several square-planar Pt(II) complexes, such as A-2 and A-3, have been prepared by the Nixon group, which are nonfluxional in solution and are formed always as the corresponding cis isomers (Scheme 2), whereas the bis-substituted products A-3 have a cis-trans stereochemistry.8,9 In contrast to the well-known coordination chemistry of type A complexes no such studies have been done so far with the 1,2,3-substituted triphosphaferrrocenes of type B. Thus, the questions arise (a) whether the coordination behavior of B would be similar to type A complexes, (b) how many complex moieties will be able to coordinate, and (c) are there preferred coordination patterns at the adjacent P atoms. Results of such investigations are reported herein.

Results and Discussion When [Cp′′′Fe(η5-P3C2(H)Ph)] (1) is allowed to react with [PtCl2(PEt3)]2 in a 1:1 stoichiometric ratio of the metal atoms at room temperature, a brown powder of 2 was obtained (eq 1). In different reactions an excess of the Pt complex (1 and 2 equiv, respectively) was also used to react with 1. However, inspecting the 31P NMR spectra of these crude reaction mixtures showed, apart from some amounts of 2, no evidence of products consisting of an intact 1,2,3-triphosphacyclopentadienyl ring, suggesting that fragmentation of this moiety had occurred. A possible explanation for the coordination of only one [PtCl2(PEt3)] unit at the P3C2 ring of 1, as illustrated in eq 1, is that the square-planar coordination mode of platinum is sterically demanding. Due to the adjacent bulky Cp′′′ ligand, it is difficult for a second [PtCl2(PEt3)] unit to coordinate at the cyclo-P3C2 ring of 1, as in the case of Cp-containing complex A-3, where the PMe3-substituted Pt complex does (Scheme 2).9 The abovementioned possible fragmentation of the cyclo-P3C2 ring of 1 in the reaction with an excess of the coordination compound was found very recently in a similar system when type A complexes possessing the bulky Cp′′′ ligand are allowed to react with an excess of CuCl, whereas the corresponding Cp complex remains intact.10 Complex 2 is only slightly soluble in CH2Cl2 and THF, but not in nonpolar solvents such as hydrocarbons. The mass spectrum of 2 reveals a molecular ion peak minus two ethylene groups of the PEt3 ligand.

Deng et al.

comparison to the uncoordinated compound [Cp′′′Fe(η5P3C2(H)Ph)] (1) (δ(PB) ) 48.9 ppm) this signal is shifted about 10 ppm downfield. The signals attributed to PD are centered at δ ) 17.4 ppm and have the smallest P-Pt coupling constant (J(PD,Pt) ) 30 Hz), while the signal centered at δ ) -68.2 ppm, which reveals the largest P-P coupling constant (J(PM,PA) ) 517.5 Hz), is assigned to PM. The doublet at δ ) 9.9 ppm belongs to PE, with a large coupling constant to the 195Pt nucleus (J(PE,Pt) ) 3212.9 Hz). PE and PA must be located in cis-positions, because of the relatively small coupling constant (J(PE,PA) ) 28.0 Hz); otherwise the coupling between the atoms PA and PE would be much larger (about 500 Hz). The sharp signals representing these four phosphorus centers in the 31P{1H} NMR spectrum of 2 at room temperature indicate that no dynamic process occurs in solution. Tungsten pentacarbonyl units were used as Lewis acids to investigate whether all three phosphorus atoms of the 1,2,3triphosphaferrocene 1 can coordinate to metal centers simultaneously. Treating 1 with a THF solution containing 1 equiv of [W(CO)5thf] gave after workup a reddish precipitate of 3 containing a mixture of two monosubstituted compounds, 3a and 3b, in an almost 1:1 ratio (eq 2), as determined by its 31 P{1H} NMR spectrum. Interestingly, from the crude reaction mixture at low temperatures only a few red-orange crystals of the disubstituted derivative 4b precipitated out.

Compound 4b is more efficiently obtained by the reaction of 1 with 2 equiv of [W(CO)5thf] (eq 3). However by using an excess of [W(CO)5thf] (4 equiv) orange-red plates of 5 were isolated in which all three P atoms are coordinated to [W(CO)5] moieties (eq 4).

The 31P{1H} NMR spectrum of 2 contains four signals. The doublet of doublet signal with 195Pt satellites centered at δ ) 77.1 ppm is readily attributed to PA, which coordinates to the Pt(II) center, revealing as expected a large coupling constant J(PA,Pt) ) 4017.5 Hz. The coordination of PA (not PD) with Pt was further confirmed by the P-H coupling constant (J(PA,Ha) ) 28.2, J(PD,Ha) ) 6.5 Hz) in the 31P NMR spectrum. In (8) Al-Ktaifani, M.; Nixon, J. F.; Hitchcock, P. B. Unpublished results. Al-Ktaifani, M. D. Phil. Thesis, Sussex University, 2004. (9) Callaghan C. S. J., Nixon; J. F.; Hitchcock, P. B. Unpublished results. Callaghan, C. S. J., D. Phil. Thesis, Sussex University, 1998. (10) Deng, S.; Schwarzmaier, C.; Vogel, U.; Zabel, M.; Nixon, J. F.; Scheer, M. Eur. J. Inorg. Chem. 2008, 4870.

Whereas the 31P NMR spectrum of the crude reaction mixture of reaction 4 indicates the existence of only the tricoordinated product 5, the corresponding spectrum of reaction 3 as well as

Coordination BehaVior of a 1,2,3-Triphosphaferrocene

that of the isolated compound 4 indicates that the major component is the 1,3-substituted derivative 4a; however the 2,3isomer 4b as well as the 1,2-isomer 4c are also present in solution as well as in the solid state (2:1:1 ratio). Interestingly, only suitable single crystals of the 2,3-isomer 4b have been obtained. The products 3, 4, and 5 are soluble in CH2Cl2 and THF, but dissolve only moderately in nonpolar solvents such as hydrocarbons. They are air-sensitive and can be stored under an inert atmosphere at low temperatures. In the EI-MS spectrum of 3 the molecular ion peak is observed, whereas for 4 the fragment with the highest relative abundance is attributable to the [Cp′′′Fe(P3C2(H)Ph)]+ cation. In addition, the cations [Cp′′′Fe(P3C2(H)Ph)W(CO)5]+ and [Cp′′′Fe(P3C2(H)Ph)W]+ are also detected and indicate the existence of 4. In the EI-MS spectra of 5 no molecular ion was detected, but fragments such as [Cp′′′Fe(η5-P3C2(H)Ph){W(CO)5}2]+, [Cp′′′Fe(η5-P3C2(H)Ph)W(CO)5]+, and [Cp′′′Fe(η5-P3C2(H)Ph)W]+ were found. The solid-state structure of 4b has been established by X-ray crystallography as shown in Figure 1. In complex 4b, two phosphorus atoms in the cyclo-P3C2 ring coordinate to two tungsten centers with an average P-W bond length of 2.502(2) Å. The coordination geometry of the two phosphorus atoms is distorted trigonal. Due to the repulsion between the two bulky [W(CO)5] units, the two P-W bonds curl upward slightly from the cyclo-P3C2 plane in order to keep the two [W(CO)5] units away from each other (Figure 3). In comparison to the P2-P1 bond length (2.130(3) Å), the P3-P2 bond length, which carries the coordinated [W(CO)5] units, is slightly shorter (2.112(3) Å). The latter bond length is comparable with that in compound B (R ) R′ ) Ph; 2.1287(14) and 2.1193(15) Å).3 The solid-state structure of 5 has also been established by X-ray crystallography as shown in Figure 2. Complex 5 possesses three phosphorus atoms in the phospholyl ring coordinated to three different [W(CO)5] units. The P2-W2 bond, which is coplanar with the cyclo-P3C2 ring, has a bond length similar to the other two P-W bonds (P2-W2 2.5135(17), P1-W1 2.5154(15), P3-W3 2.5120(17) Å). Because of the repulsion of the two tBu groups on the cyclopentadienyl ring, the P1-W1 and P3-W3 bonds are bent upward from the cyclo-P3C2 plane (Figures 2 and 3). The average distance of W-P in 5 (2.514(2) Å) is longer than that in 4b (2.502(2) Å). The average P-P bond length (2.123(2) Å) is

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Figure 1. Molecular structure of 4b in the crystal (depicted at the 30% probability level; hydrogen atoms are omitted for clarity). Selected bond lengths (Å) and angles (deg): P3-P2 2.112(2), P2-P1 2.130(2), P3-C22 1.746(8), P1-C21 1.772(6), P3-W2 2.488(2), P2-W1 2.515(2), Fe-P3 2.332(2), Fe-P2 2.369(2), Fe-P1 2.363(2), P1-P2-P3 100.54(11), P1-P2-W1 124.69(10), P2-P3-W2 137.41(11), W2-P3-C22 122.7(3), P2-P3-C22 97.5(3).

Figure 2. Molecular structure of 5 in the crystal (depicted at the 30% probability level; hydrogen atoms are omitted for clarity). Selected bond lengths (Å) and angles (deg): P1-P2 2.125(2), P2-P3 2.121(2), P1-C17 1.755(7), P3-C16 1.751(6), P1-W1 2.5154(15), P2-W2 2.5135(17), P3-W3 2.5120(17), Fe-P1 2.3653(17), Fe-P2 2.3808(19), Fe-P3 2.3508(19), P1-P2-P3 99.45(9),P1-P2-W2130.49(8),W2-P2-P3129.43(8),W1-P1-P2 128.19(8), W3-P3-P2 133.92(9).

slightly longer than that in 4b (2.121(2) Å) and is almost the same as that in complex [Cp′′′Fe(η5-P3C2Ph2)] B (2.124(2) Å).3 It is noteworthy that the P-P bond shows no significant change after coordination of [W(CO)5] fragments. The average P-Fe bond length in 5 (2.366 Å) is longer than that in 4b (2.355 Å). All these bond length elongations in 5 compared to 4b may be caused by steric effects. The 31P{1H} NMR spectrum of complex 5 shows three slightly broadened doublets of doublets of a ABM spin system (PA ) P1, PB ) P3, PM ) P2). All signals shift upfield in comparison to the uncoordinated complex 1 (Table 1). If 4 is dissolved in CD2Cl2 in the 31P{1H} NMR spectrum at ambient temperature, broadened signals of a ABM spin system of 4a as the major component as well as poorly resolved multiplets of 4b and 4c showing no evidence for J(P,W) couplings are observed. On lowering the temperature, the signals get sharper and the corresponding 183W satellites are resolved. Whereas the signals of the tungsten-substituted P atoms very slightly shifted with temperature decrease, the signals of the uncoordinated P2 atom are significantly shifted to higher field (-82.4 f -88.5

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Deng et al.

Figure 3. Top view of the molecular structures of 4b and 5 to express the configurations in the solid state (ball-and-stick presentation, hydrogen atoms are omitted for clarity). Table 1. Comparison of Selected 31P NMR Spectroscopic Data of [Cp′′′Fe(η5-P3C2(H)Ph)] (1) and Its Tungsten Complexes 3a, 3b, 4a, 4b, 4c, and 5 in CH2Cl2 at 293 Ka [Cp′′′Fe(η5-P3C2(H)Ph)] 1 [Cp′′′Fe(η5-P3C2(H)Ph)3-{W(CO)5}] 3ac [Cp′′′Fe(η5-P3C2(H)Ph)2-{W(CO)5}] 3bc [Cp′′′Fe(η5-P3C2(H)Ph)1,3-{W(CO)5}2] 4aa,c [Cp′′′Fe(η5-P3C2(H)Ph)2,3-{W(CO)5}2] 4ba,c [Cp′′′Fe(η5-P3C2(H)Ph)1,2-{W(CO)5}2] 4ca,c [Cp′′′Fe(η5-P3C2(H)Ph){W(CO)5}3] 5c a

δ(P1) [ppm]

δ(P2) [ppm]

δ(P3) [ppm]

J(P1,P2) [Hz]

J(P2,P3) [Hz]

J(P1,P3) [Hz]

51.7 43.1 1.7 47.4 -25.6 -4.0 2.7

15.2 -32.4 16.8 -88.5 7.6 7.8 -54.9

48.9 45.7 1.1 35.0 -14.6 -16.7 -3.7

427.1 425.9 432.4 466.9 512 512 446.7

399.6 471.3 445.7 468.0 412 412 412.4

0b 4.4 26.9 13.8 10 30 0b

At 183 K. b As a consequence of the line broadening. c Labeling scheme cf. Scheme 3.

Scheme 3. Labeling Scheme of the Isomers at the 1,2,3-Triphospholyl Ring of the Complexes

ppm). By simulation of the spectra of the individual compounds and comparison with the proton coupled spectra the assignment of the P atoms can be given (Table 1), and the data for all isomers of compound 4 can be determined. In contrast, for 3a,b already at 293 K the corresponding 183W satellites are revealed. In 3a and 4a (both revealing the energetically favored structures, cf. DFT calculations), the coordination of the P atoms by [W(CO)5] moieties has not much influence on the chemical shift of the corresponding P atoms in comparison with the starting material, whereas the uncoordinated P atoms shift much more. In contrast, in the energetically less favored derivatives 3b, 4b, and 4c and in the tricoordinated derivative 5 the influence of the coordination on chemical shifts and coupling constants is much more important. This might reflect the angle and bond length effects in the sterically crowded derivatives. DFT Computations. To gain more insight into the stability of the formed derivatives and for any possible dissociation behavior, density functional calculations have been carried out for all possible isomers. For the monocoordinated compounds 3 the relative conformational stability of the three isomers with respect to the orientation of the Cp′′′ ligand have been calculated. According to the calculations, the 2-isomer 3b and the 3-isomer 3a are the most stable isomers, with 3a being disfavored by only 1.3 kJ mol-1 (Figure 4). This small isomer energy difference between 3b and 3a suggests that they should be

present in comparable quantities if an equilibrium exists between the isomers in solution. In contrast the 1-isomer 3c would be much less favored by 18.2 kJ mol-1. Other rotational conformers of 3c are even more disfavored (by 28-32 kJ mol-1). This confirms the experimentally obtained results, in which only 3a and 3b could be identified as the reaction products of reaction 1. Moreover, within the possible disubstituted isomers the 2,3isomer 4b is the thermodynamically most favored one, followed by the 1,3-isomer 4a, which is only 0.8 kJ mol-1 higher in energy, and the 1,2-isomer 4c, which is 7.3 kJ mol-1 less stable than 4b (Figure 5). Interestingly, the observed energetically favored rotational conformer of the 2,3-isomer is identical with the fully structurally characterized product 4b. However, if entropy change is taken into account, computations predict that at room temperature isomers 3a and 4a will be slightly more favored compared to 3b and 4b (Table 2). This agrees well with experimental observation of both 3a, 3b and 4a, 4b in solution. We have also estimated the influence of the solvent on the isomer stability using a self-consistent reaction field approach. CH2Cl2 solvent was modeled by the polarizable continuum model (PCM). The extended 6-31++G** basis set, which includes diffuse functions, has been applied. The energy difference between isomers 4b and 4c decreases from 7.3 to 5.0 (B3LYP/6-31++G** SCRF single-point energy at B3LYP/ 6-31G* optimized geometry) or 4.8 kJ mol-1 (B3LYP/631++G** SCRF full optimization). Thus, we conclude that CH2Cl2 as a solvent does not have a large influence on energy differences between isomers. In the further discussion, only gas phase data will be considered. Our optimized geometries for the gas phase 4b and 5 are in reasonable agreement with experimental X-ray data for the solid compounds. Bond distances are slightly overestimated, which is usual for the B3LYP level of theory. Theoretically predicted P-P-P angles in 4b and 5 (101.0° and 99.4°) are in excellent

Coordination BehaVior of a 1,2,3-Triphosphaferrocene

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Figure 4. Optimized geometries of the most stable conformers of monoadducts 3. Relative energies in kJ mol-1. (a) [Cp′′′Fe(η5-P3C2(H)Ph)1{W(CO)5}] 3c; (b) [Cp′′′Fe(η5-P3C2(H)Ph)2-{W(CO)5}] 3b; (c) [Cp′′′Fe(η5-P3C2(H)Ph)3-{W(CO)5}] 3a. B3LYP/6-31G*(LANL2DZ basis for W) level of theory.

Figure 5. Optimized geometries of the most stable conformers of the bis-adducts. Relative energies in kJ mol-1. (a) [Cp′′′Fe(η5-P3C2(H)Ph)1,2{W(CO)5}2] 4c; (b) [Cp′′′Fe(η5-P3C2(H)Ph)2,3-{W(CO)5}2] 4b; (c) [Cp′′′Fe(η5-P3C2(H)Ph)1,3-{W(CO)5}2] 4a. B3LYP/6-31G*(LANL2DZ basis for W) level of theory. Table 2. Thermodynamic Characteristics for the Gas Phase Processes at the B3LYP/6-31G*(LANL2DZ basis for W) Level of Theory ∆E process 3c ) 3a 3b ) 3a 3c ) 1 + W(CO)5 3b ) 1 + W(CO)5 3a ) 1 + W(CO)5 3c + THF ) 1 + [W(CO)5thf] 3b + THF ) 1 + [W(CO)5thf] 3a + THF ) 1 + [W(CO)5thf] 4b ) 4a 4c ) 4a 4b ) 3b + W(CO)5 4b ) 3a + W(CO)5 4b + THF ) 3b + [W(CO)5thf] 4b +THF ) 3a + [W(CO)5thf] 5 ) 4b + W(CO)5 5 ) 4c + W(CO)5 5 ) 4a + W(CO)5 5 + THF ) 4b + [W(CO)5thf] 5 + THF ) 4c + [W(CO)5thf] 5 + THF ) 4a + [W(CO)5thf] [W(CO)5thf] ) W(CO)5 + THF

∆H°298 -1

kJ mol

kJ mol

-16.9 1.3 122.6 140.8 139.4 12.4 30.6 29.2 0.8 -6.4 115.5 116.9 5.3 6.7 99.0 106.2 99.8 -11.2 -3.9 -10.4 110.2

-17.7 0.1 116.6 134.4 134.3 13.5 31.2 31.2 0.5 -6.9 109.8 109.9 6.7 6.8 92.9 100.3 93.5 -10.2 -2.8 -9.7 103.1

agreement with experimental values 100.54(11)° and 99.45(9)°. The calculated mean W-P bond distance in 5 (2.576 Å) is longer than that in 4b (2.561 Å), in agreement with experimental observations for the solid-state compounds. Thermodynamic characteristics of complex dissociation processes are summarized in Table 2. The [W(CO)5] moiety is quite strongly bound to phosphorus and P-W bond dissociation energies are in the range 99-141 kJ mol-1. The stability of the complexes decreases with increasing numbers of [W(CO)5] units

∆S°298

-1

J mol

-1

∆G°298 -1

K

6.8 8.8 181.0 183.0 174.2 20.7 22.7 13.9 15.4 24.3 192.3 201.1 32.0 40.8 204.5 195.6 219.9 44.2 35.3 59.6 160.3

kJ mol

-1

-19.7 -2.5 62.7 79.8 82.4 7.3 24.5 27.0 -4.1 -14.1 52.6 50.0 -2.8 -5.4 32.0 42.0 27.9 -23.4 -13.3 -27.4 55.4

∆G°398 kJ mol-1 -20.4 -3.4 44.6 61.5 65.0 5.2 22.2 25.6 -5.6 -16.5 33.3 29.9 -6.0 -9.4 11.6 22.5 6.0 -27.8 -16.9 -33.4 39.3

(141 > 116 > 99 kJ mol-1 for the most stable isomers 3b, 4b, and 5, respectively). If THF is present in the solution, formation of the [W(CO)5thf] complex should be taken into account. These data are also summarized in Table 2. The thf-W(CO)5 bond energy is larger compared to P-W bonds in tris-adducts, but smaller than the one found in bis- and monoadducts. Thus, the triscomplex 5 reacts with THF exothermically, while reactions of THF with bis-adducts 4 and monoadducts 3 are endothermic.

1080 Organometallics, Vol. 28, No. 4, 2009

Deng et al. Table 3. Crystallographic Data for 4b and 5 5 · CH2Cl2

4b empirical formula fw temperature wavelength cryst syst space group unit cell dimens

C35H35FeO10P3W2 1132.07 123(1) K 1.54184 Å monoclinic C2/c a ) 32.8307(5) Å b ) 11.56806(18) Å c ) 21.5150(3) Å β ) 107.9860(17)

volume Z density calcd absorp coeff F(000) cryst size θ range for data collection index ranges no. of reflns collected no. of indep reflns completeness to θ absorp corr max. and min. transm no. of data/restraints/params goodness-of-fit on F2 final R indicesa [I > 2σ(I)] R indicesb (all data) largest diff peak and hole a

7771.8 (2) Å3 8 1.935 Mg/m3 15.281 mm-1 4352 0.03 × 0.06 × 0.14 mm 2.8 to 51.5° -33 e h e 27, -11 e k e 10, -21 e l e 21 11 470 4150 [R(int) ) 0.032] 97.3% multiscan 1.0000 and 0.37878 4150/0/466 1.066 R1 ) 0.0325, wR2 ) 0.0693 R1 ) 0.0431, wR2 ) 0.0743 1.02 and -0.92 e A-3

C41H37FeO15P3W3Cl2 1540.89 123(1) K 1.54184 Å triclinic P1j a ) 11.4506(6) Å b ) 12.8637(7) Å c ) 18.9303(9) Å R ) 78.287(4)° β ) 78.727(4)° γ ) 65.317(5)° 2461.6(2) Å3 2 2.079 Mg/m3 17.411 mm-1 1460 0.200 × 0.170 × 0.130 mm 2.40 to 62.17° -13 e h e 13, -14 e k e 14, -20 e l e 21 23 456 7607 [R(int) ) 0.0219] 97.8% multiscan 1.00000 and 0.61563 7607/0/595 1.034 R1 ) 0.0343, wR2 ) 0.0848 R1 ) 0.0370, wR2 ) 0.0868 2.298 and -2.830 e A-3

R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2]/[∑(Fo2)2.

However, if entropy change is taken into account, standard Gibbs energies for the reaction with THF are negative for both 5 (-13 kJ mol-1) and 4b (-3 kJ mol-1) and positive for 3b (25 kJ mol-1). Since these reactions proceed with no change in the number of gaseous molecules, the trend in thermodynamic characteristics found for the gas phase should also be retained in CH2Cl2 solution. Due to small absolute values of the standard Gibbs energies, a shift of the equilibrium toward formation of 5 is expected with an excess of [W(CO)5thf].

predicted by DFT computations. It seems likely that the broadened signals of the 31P NMR spectra at room temperature are due to the rotation of the Cp′′′ ring of the ferrocenes. The static behavior of all the complexes described in this paper sharply contrasts with the behavior of η1-bonded 1,2,4-P3C2R2 ring complexes of a variety of metals, which show a strong tendency to undergo 1,2 shift and ring inversion dynamics.11

Conclusions

General Procedures. All manipulations were performed under an atmosphere of dry nitrogen using standard glovebox and Schlenk techniques. Solvents were purified and degassed by standard procedures. The starting material 1 was prepared according to our published methods;4 [PtCl2PEt3]2 was synthesized from PtCl2 and [PtCl2(PEt3)2].12,13 Solution NMR spectra were recorded on a Bruker AVANCE 400 spectrometer (1H: 400.13 MHz, 31P: 161.976 MHz, with δ [ppm] referenced to external SiMe4 (1H) and H3PO4 (31P)). Mass spectra were performed using a Finnigan MAT 95. IR spectra were recorded on a Varian FTS 2000, and elemental analyses were performed with an Elementar Vario EL III. Syntheses of [Cp′′′Fe(µ,η5:η1-P3C2(H)Ph){PtCl2(PEt3)}] (2). A solution of [Cp′′′Fe(η5-P3C2PhH)] (20 mg, 0.041 mmol) and [(PtCl2PEt3)2] (16 mg, 0.02 mmol) in CH2Cl2 (10 mL) was stirred for 1 h at room temperature. An orange-red solution was formed. After concentration under reduced pressure to about one-third of the original volume, hexane (5 mL) was added and a brown powder was obtained (20 mg, 55.9% yield). 31P{1H} NMR (CD2Cl2, 293 K, 161.98 MHz): δ(PA) ) 77.1 ppm, δ(PD) ) 17.4 ppm, δ(PE) ) 9.9 ppm, δ(PM) ) -68.2 ppm, J(PD,PM) ) 420.8 Hz, J(PA,PM) )

We have shown in reactions of the 1,2,3-triphosphaferrocene with organometallic Lewis acids that a particular steric influence of the adjacent tri-tert-butylcyclopentadienyl ligand as well as the organic substituents at the triphospholyl ring exists. Thus, the square-planar complex moiety [PtCl2(PEt3)] gives only a monocoordinated complex 2, whereas the more flexible [W(CO)5] unit yields all types of substitution patterns depending on the used stoichiometry. Even if an excess of [W(CO)5thf] is used, the tricoordinated derivative 5 is obtained. Interestingly, in the 1:1 stoichiometric reaction only the energetically favored monocoordinated derivatives 3a and 3b are obtained, as DFT calculations incorporating all possible conformational rotamers have shown. In a 1:2 reaction all possible dicoordinated derivatives 4a-c are detected. However, the energetically favored 1,3-coordinated isomer 4a is the main product of the reaction. In general, the P atom adjacent to the CH unit of the 1,2,3-triphospholyl ring is favored for coordination for steric reasons. The room-temperature 31P NMR spectra of the monocoordinated derivatives 3 and the variable-temperature NMR studies for complexes 4 have shown that there is no dynamic behavior involving movement of the [W(CO)5] moieties between two adjacent P atoms of the η5-P3C2(H)Ph ring. This observation is in accordance with strong W-P bonding in the complexes

Experimental Section

(11) Hofmann, M.; Clark, T.; Heinemann, F. W.; Zenneck, U. Eur. J. Inorg. Chem. 2008, 2225, and references therein. (12) McDermott, J. X.; White, J. F.; Whitesides, G. M. J. Am. Chem. Soc. 1976, 98, 6521. (13) Hartley, F. R. Organomet. Chem. ReV. A 1970, 6, 119.

Coordination BehaVior of a 1,2,3-Triphosphaferrocene 517.5 Hz, J(PA,PE) ) 28.0 Hz, J(PA,PD) ) 4.7 Hz, J(PD,Pt) ) 30 Hz, J(PM,Pt) ) 149.0 Hz, J(PA,Pt) ) 4017.5 Hz, J(PE,Pt) ) 3212.9 Hz. 31P NMR (CD2Cl2, 300 K, 161.98 MHz): J(Pa,Ha) ) 6.5 Hz, J(Pc,Ha) ) 28.2 Hz. 1H NMR (C6D6, 298 K, 400.13 MHz): δ 1.29 (s, 9H), 1.38 (s, 9H), 1.45 (s, 9 H), 2.10 (m, 15H, Et), 4.18 (dd, 1H, Cp′′′), 4.61 (dd, 1H, Cp′′′), 6.18 (ddd, 1H, P3C2-ring), 7.70 (m, 3H, C6H5), 7.77 (m, 2H, C6H5) ppm. ESI-MS (MeCN, RT): m/z ) 750 [Cp′′′Fe(P3C2PhH)PtCl2]+ (3.6%), 768 [Cp′′′Fe(P3C2PhH)PtPEt2]+ (1.7%), 812 [Cp′′′Fe(P3C2PhH)PtCl2PEt(H)2]+ (1.4%). Syntheses of [{Cp′′′Fe(µ,η5:η1:η1-P3C2(H)Ph)}W(CO)5] (3a, 3b). A solution of [Cp′′′Fe(η5-P3C2(H)Ph)] (24 mg, 0.05 mmol) and [W(CO)5thf] (0.05 mmol) in THF (5 mL) was stirred for 1 h at room temperature. The color of the reaction solution changed from red to red-orange. After removal of all solvent in vacuum, the residue was dissolved in about 2 mL of dichloromethane, the solution was kept at -28 °C for 1 week, and red microcrystals were obtained (20 mg, 51% yield). EI-MS (70 eV): m/z ) 484 [Cp′′′Fe(P3C2PhH)]+ (100%), 667 [Cp′′′Fe(P3C2PhH)W]+ (16%), 807 [Cp′′′Fe(P3C2PhH)W(CO)5]+ (7%). Anal. Calcd for C30H35FeO5P3W: C, 44.58; H 4.36. Found: C, 44.13; H, 4.01. 3a: 31 P{1H} NMR (CD2Cl2, 293 K, 161.98 MHz, ABM spin system): δ(PA) 43.1 ppm, δ(PB) ) 45.7 ppm, δ(PM) -32.4 ppm, J(PA,PM) ) 425.9 Hz, J(PM,PB) ) 471.3 Hz, J(PA,PB) ) 44 Hz, J(PB,W) ) 241.4 Hz. 3b: 31P{1H} NMR (CD2Cl2, 293 K, 161.98 MHz, ABM spin system): δ(PA) 1.7 ppm, δ(PB) 1.1 ppm, δ(PM) 16.8 ppm, J(PA,PM) ) 432.4 Hz, J(PM,PB) ) 445.7 Hz, J(PA,PB) ) 26.9 Hz, J(PM,W) ) 214.8 Hz. 1H NMR (CD2Cl2, 300 K, 400.13 MHz): δ 1.20/1.23 (s, 9H), 1.40/1.42 (s, 9H), 1.50/1.52 (s, 9 H), 4.32 (dd, 2H, Cp′′′), 4.56 (dd, 2H, Cp′′′), 5.75 (ddd, 2H, P3C2-ring), 7.32 (m, 6H, C6H5), 7.80 (m, 4H, C6H5) ppm. [{Cp′′′Fe(µ,η5:η1:η1-P3C2(H)Ph)}{W(CO)5}2] (4). A solution of [Cp′′′Fe(η5-P3C2(H)Ph)] (20 mg, 0.041 mmol) and [W(CO)5thf] (30 mg, 0.08 mmol) in THF (15 mL) was stirred for 1 h at room temperature. The color of the reaction solution changed from red to red-orange. After removal of all solvent in vacuum, the residue was dissolved in about 2 mL of dichloromethane. By adding n-hexane an orange solid of 4 (25 mg, 48% yield) was precipitated. If the CH2Cl2 solution was kept at -28 °C for 1 week, orange-red crystals of 4b were obtained: IR (CH2Cl2): ν(CO) [cm-1]: 2078 (w), 2072 (m), 1975 (sh), 1953 (s, br). EI-MS (70 eV): m/z ) 484 [Cp′′′Fe(P3C2PhH)]+ (100%), 667 [Cp′′′Fe(P3C2PhH)W]+ (42%), 807 [Cp′′′Fe(P3C2PhH)W(CO)5]+ (66%), 1131 [{Cp′′′Fe(P3C2PhH)}{W(CO)5}2]+ (35%). Anal. Calcd for C35H35FeO10P3W2: C, 37.13; H 3.12. Found: C, 36.89; H, 3.81. 4a: 31P{1H} NMR (CD2Cl2, 293 K, 161.98 MHz, ABM spin system): δ(PA) 47.3 ppm, δ(PB) 36.0 ppm, δ(PM) -82.4 ppm; 31P{1H} NMR (CD2Cl2, 183 K, 161.98 MHz, ABM spin system): δ(PA) 47.4 ppm, δ(PM) -88.5 ppm, δ(PB) 35.0 ppm, J(PA,PM) ) 466.9 Hz, J(PM,PB) ) 468.0 Hz, J(PA,PB) ) 13.8 Hz, J(PA,183W) ) 244 Hz, J(PB,183W) ) 244 Hz. 31P{1H} NMR (THF-d8/CH2Cl2 (3:1), 293 K, 161.98 MHz, ABM spin system): δ(PA) 48.5 ppm, δ(PB) 38.1 ppm, δ(PM) -81.0 ppm, J(PA,PM) ) 462 Hz, J(PM,PB) ) 466 Hz, J(PA,PB) ) 14.9 Hz, J(PA,183W) ) 250 Hz, J(PB,183W) ) 250 Hz. 4b: 31P{1H} NMR (CH2Cl2, 183 K, 161.98 MHz, ABM spin system): δ(PA) -25.6 ppm, δ(PB) -14.6 ppm, δ(PM) 7.6 ppm, J(PA,PM) ) 512 Hz, J(PM,PB) ) 412 Hz, J(PA,PB) ) 10 Hz, J(PA,183W) ) 244 Hz, J(PB,183W) ) 244 Hz. 1H NMR (CD2Cl2, 293 K, 400.13 MHz): δ 1.19 (s, 9H), 1.22 (s, 9H), 1.39 (s, 9 H), 4.28 (dd, 2H, Cp′′′), 5.80 (ddd, 1H, P3C2-ring), 7.35 (m, 3H, C6H5), 7.80 (m, 2H, C6H5) ppm. IR (CH2Cl2): ν(CO) [cm-1]: 2076, 1975, 1950. 4c: 31P{1H} NMR (CH2Cl2, 183 K, 161.98 MHz, ABM spin system): δ(PA) -4.0 ppm, δ(PB) -16.7 ppm, δ(PM) 7.8 ppm, J(PA,PM) ) 512 Hz, J(PM,PB) ) 412 Hz, J(PA,PB) ) 30 Hz, J(PA,183W) ) 300 Hz, J(PB,183W) ) 244 Hz.

Organometallics, Vol. 28, No. 4, 2009 1081 Synthesis of [{Cp′′′Fe(µ,η5:η1:η1-P3C2(H)Ph)}{W(CO)5}3] (5). A solution of [Cp′′′Fe(η5-P3C2(H)Ph)] (20 mg, 0.041 mmol) and [W(CO)5thf] (60 mg, 0.16 mmol) in THF (25 mL) was stirred for 16 h at room temperature. After removal of all solvents in vacuum the residue was dissolved in about 3 mL of dichloromethane and the solution was kept at -28 °C for 1 week. Orange-red crystals of 5 were obtained (20 mg, 33.4% yield). 31P{1H} NMR (CD2Cl2, 293 K, 161.98 MHz, ABM spin system): δ(PA) 2.7 ppm, δ(PM) -54.9 ppm, δ(PB) -3.7 ppm, J(PA,PM) ) 412.4 Hz, J(PM,PB) ) 446.7 Hz, J(PA,W) ) 289 Hz, J(PM,W) ) 202 Hz, J(PB,W) ) 231 Hz. 1H NMR (CD2Cl2, 293 K, 400.13 MHz): δ 1.38(s, 9H), 1.65 (s, 9H), 1.67 (s, 9H), 4.30 (dd, 2H, Cp′′′), 5.85 (ddd, 1H, P3C2ring), 7.35 (m, 3H, C6H5), 7.80 (m, 2H, C6H5) ppm. IR (CH2Cl2): ν(CO) [cm-1]: 2055, 1942, 1908. EI-MS (70 eV): m/z ) 484 [Cp′′′Fe(P3C2PhH)]+ (100%), 668 [Cp′′′Fe(P3C2PhH)W]+ (54%), 807 [Cp′′′Fe(P3C2PhH)W(CO)5]+ (17%), 1131 [{Cp′′′Fe(P3C2PhH)}{W(CO)5}2]+ (5%). Anal. Calcd for C40H35FeO15P3W3: C, 33.00; H 2.42. Found: C, 33.42; H, 2.77. X-ray Structure Analysis. The crystal structure analyses were performed on an Oxford Diffraction Gemini Ultra diffractometer with Cu KR radiation (λ ) 1.54184). Compound 5 crystallizes with 1 equiv of CH2Cl2 per formula unit. The structures were solved by direct methods with the program SHELXS-97,14a and full matrix least-squares refinement on F2 in SHELXL-9714b was performed with anisotropic displacements for non-H atoms. The hydrogen atoms at the carbon atoms were located in idealized positions and refined isotropically according to the riding model. Empirical absorption corrections using spherical harmonics, implemented in the CrysAlis-RED program of Oxford Diffraction, were applied. Computational Details. All structures were fully optimized and verified with subsequent vibrational analysis to be minima on the potential energy surface. Density functional theory in the form of the hybrid B3LYP15 functional was used together with the standard full-electron 6-31G* basis set. The LANL2DZ ECP basis set of Hay and Wadt16 was used for W. The Gaussian 0317 suite of programs was used throughout. Solvent effects (CH2Cl2) were estimated using the self-consistent reaction field approach in a polarizable continuum model (PCM) approximation with the 6-31++G** basis set as implemented in the Gaussian 03 program package.

Acknowledgment. The authors are grateful to the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie for financial support. The Alexander von Humboldt Foundation is gratefully acknowledged for a Research Award (to J.F.N.). Supporting Information Available: Experimental and simulated P NMR spectra of the products, complete ref 17 citation, and computational details (optimized xyz coordinates and total energies of considered compounds). This material is available free of charge via the Internet at http://pubs.acs.org.

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OM801118K (14) (a) Sheldrick, G. M. SHELXS-97; Universita¨t Go¨ttingen, 1997. (b) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, 1997. (15) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785. (16) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (b) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284. (c) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299. (17) Frisch, M. J. et al. Gaussian 03 (ReVision D.01); Gaussian, Inc.: Wallingford, CT, 2004.