Effect of the Substitution on the Protonation of Allyl Cyclopentadienyl

Article pubs.acs.org/Organometallics

Effect of the Substitution on the Protonation of Allyl Cyclopentadienyl Molybdenum(II) Compounds Jan Honzíček,*,† Pavel Kratochvíl,† Jaromír Vinklárek,† Aleš Eisner,‡ and Zdeňka Padělková† †

Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice, Czech Republic ‡ Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice, Czech Republic S Supporting Information *

ABSTRACT: Synthesis, characterization, and reactivity of new allyl cyclopentadienyl molybdenum(II) compounds [(η3C3H4R1)(η5-C5H3(R2)2)Mo(CO)2] (R1 = H, COOMe; R2 = COOMe, CONHtBu) are reported. Although these compounds are structural analogues of [(η3-C3H5)(η5-Cp)Mo(CO)2], their reactivity is very different. While protonation of [(η3-C3H5)(η5-Cp)Mo(CO)2] gives a cationic cyclopentadienyl complex, the presented compounds give cationic allyl complexes [(η3-C3H4R)Mo(CO)2(NCMe)3][BF4] (R = H, COOMe) or stable cationic allyl cyclopentadienyl complexes. The theoretical calculations have shown that this behavior is a result of high affinity of the functional groups in the cyclopentadienyl ligand toward protonation.

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INTRODUCTION Mono- and bis-cyclopentadienyl molybdenum complexes are currently under comprehensive scrutiny due to their catalytic1 and biological properties.2 Monocyclopentadienyl compounds [η5-Cp′MoO2Cl] (Cp′ = substituted Cp; Cp = C5H5; X = halide, alkyl) and their precursors [η5-Cp′Mo(CO)3X] and [(η3-C3H5)(η5-Cp′)M(CO)2] catalyze the oxidation of olefins3 and sulfides.4 H/D exchange,5 transfer hydrogenation,6 nitrile hydration,7 and organophosphates hydrolysis8 are catalyzed with molybdenocene dichloride [η5-Cp2MoCl2] and its ringsubstituted analogues. Promising cytostatic properties were reported for molybdenocene dichloride9 and some cationic monocyclopentadiendyl complexes [η5-Cp′Mo(CO)2L2][BF4] (L = N,N-, P,P-, and S,S-chelating ligands).10 Allyl complexes [(η3-C3H5)(η5-Cp′)M(CO)2] (M = Mo, W) are known as suitable precursors for the synthesis of ringsubstituted molybdenocenes and tungstenocenes.11 Protonation of [(η3-C3H5)(η5-Cp′)M(CO)2] (M = Mo, W) with HBF4 gives a strongly dienophilic intermediate, which coordinates cyclopentadienes to give η4-compounds. The bis-cyclopentadienyl compounds are then available through an oxidative, reductive, or photochemical pathway.12−14 This procedure was found to be suitable for a variety of mixed cyclopentadienyl− indenyl compounds12,14,15 as well as for bis-cyclopentadienyl compounds containing a functionalized cyclopentadienyl ring.16 ansa-Molybdenocenes [(η5-Ind′)Mo(η5-C5H4CH2-η1-CH2)(CO)][BF4] (Ind′ = substituted indenyl) were synthesized by a modified route starting from [(η5-Ind′)Mo(CO)2(NCMe)2][BF4] and spiro[2.4]hepta-4,6-diene.17 This work is focused 1,2-disubstituted cyclopentadienyl ligands bearing strong electron-withdrawing functional groups. © 2012 American Chemical Society

The previous studies have shown that such ligands bearing two acyl, alkyloxycarbonyl, alkylcarbamoyl, and imidoyl substituents form stable pentahapto coordination compounds only with soft late transition metals: [(η5-C5H3(COOEt)2)M(CO)3] (M = Mn, Re), [(η 5 -C 5 H 3 (COOEt) 2 ) 2 Ru 2 (CO) 2 ], 1 8 [(η 5 C5H3(CONHtBu)2)RuCl(PPh3)2], [(η5C5H3(CONHtBu)2)2M] (M = Fe, Ru),19 [(η5-C5H3(COPh)2)(η5-C5Me5)M][Cl] (M = Rh, Ir),20 [(η5-C5H3((CNC6H3R2)Ph) 2 )(η 5 -C 5 Me 5 )Ru] (R = Me, i Pr, Cl), 23 and [(η 5 C5H3((CNC6H3R2)CF3)2)(η5-C5Me5)Ru] (R = H, Cl).21 Due to low nucleophilicity of the cyclopentadienyl system, highly oxophilic zirconium(IV) gives compounds with a κ2O,O-bonded ligand: [Cp(κ 2 -O,O-C 5 H 3 (CONH t Bu) 2 )ZrCl2(THF)], [(κ2-O,O-C5H3(CONHtBu)2)ZrCl3(THF)], and [(κ2-O,O-C5H3(CONHtBu)2)2ZrCl2]; see Scheme 1.22 Scheme 1. Bonding Modes of the C5H3(COR)2 Ligands

This study shows that the molybdenum(II) compounds favor the η5-coordination mode of the 1,2-disubstituted methoxycarbonyl- and tert-butylcarbamoyl−cyclopentadienyl ligands. Such substitution of the cyclopentadienyl ligand has an Received: October 24, 2011 Published: March 2, 2012 2193

dx.doi.org/10.1021/om2010244 | Organometallics 2012, 31, 2193−2202

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unexpected effect on the protonation of the allyl compounds [(η3-C3H5)(η5-Cp′)Mo(CO)2].

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RESULTS AND DISCUSSION Synthesis of the Allyl Complexes. 1,2-Disubstituted cyclopentadienides Na[C5H3(COOMe)2] (1-Na) and Na[C5H3(CONHtBu)2] (2-Na) and molybdenum precursor [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (4) were prepared according to literature procedures.18,22,23 [{(η3-C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5) was prepared by oxidative a d d i t i o n o f t r a n s - 4- b r o m o - 2 - bu t e n o a t e t o [ M o (CO)3(NCMe)3]. The substituted cyclopentadienides react with [(η 3 -C 3 H 5 )Mo(CO) 2 (NCMe) 2 Cl] (4) and [{(η 3 C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5) to give [(η3C3H5)(η5-C5H3R2)Mo(CO)2] (6: R = COOMe, 7: R = CONHtBu) and [(η3-C3H4COOMe)(η5-C5H3R2)Mo(CO)2] (8: R = COOMe, 9: R = CONHtBu), respectively (Scheme 2). The same procedure was used for the preparation of [(η3Figure 1. ORTEP drawing of [(η3-C3H5)(η5-C5H3(CONHtBu)2)Mo(CO)2] (7). The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

Scheme 2. Synthesis of Molybdenum(II) Compounds 6−9a

a

carbonyl ligands and the characteristic CO stretching bands of the ester and amide functional groups; see Table 1. The spectra of compounds 6 and 8 have CO stretching modes of the methoxycarbonyl groups in the range 1714−1738 cm−1. This feature indicates low delocalization of π-electrons from the CO group that is supposed for η5-coordination of the C5H3(COOMe)2. The vibrational spectra of compounds 7 and 9 have CO stretching bands of the carbamoyl groups at high wavenumbers (see Table 1), which is incompatible with an O,O-bonding mode.22 The compounds with a methoxycarbonyl-substituted allyl ligand (8, 9) display CO stretching bands at considerably higher wavenumbers than their unsubstituted analogues (6, 7). The higher values suggest progressively lower electron density at the metal. This is commensurate with the strong electron-withdrawing effect of the functional group in the η3-allyl ligand. Reaction with HBF4. Protonation of the allyl molybdenum compound [(η3-C3H5)(η5-Cp)Mo(CO)2] in noncoordinating solvents generates the labile η2-propene complex [(η2C3H6)(η5-Cp)Mo(CO)2(FBF3)].25 The weakly bonded propene and BF4− are easily exchanged with stronger donors. For example, the reaction in acetonitrile gives cationic species [(η5Cp)Mo(CO)2(NCMe)2][BF4] (Scheme 3).26 This behavior was observed for a variety of substituted cyclopentadienyl compounds including those with condensed benzene rings (e.g. indenyl,12 cyclopenta[l]phenanthrenyl27) or compounds with strong electron-withdrawing substituents (e.g. C5H4COOMe).16 In the case of compounds 6 and 7, we observe a very different product. Reaction with HBF4 in the solution containing acetonitrile gives cationic allyl compound [(η3C3H5)Mo(CO)2(NCMe)3][BF4] (11) as the sole product; see Scheme 4. The analytical and spectroscopic data collected for this compound agree with those previously reported for [(η3C3H5)Mo(CO)2(NCMe)3][PF6] (11-PF6).28 The proposed structure was further proved by X-ray analysis (see Figure 4). The appearance of compound 11 upon protonation of the allyl cyclopentadienyl compounds 6 and 7 could be explained so that the proton attacks the substituted cyclopentadienyl instead of the allyl ligand. The theoretical calculations on the

1, 6, and 8: R = COOMe; 2, 7, and 9: R = CONHtBu.

C3H4COOMe)(η5-C5H4COOMe)Mo(CO)2] (10). It is given by reaction of monosubstituted cyclopentadienide Na[C5H4COOMe] (3-Na) and allyl compound 5. The η5-coordination of the substituted cyclopentadienyl ligands was evidenced by spectroscopic measurements and in the case of compounds 7, 8, and 10 further supported with Xray analysis (Figures 1−3). The NMR spectroscopic measurements show that the allyl compounds 6 and 7 have Cssymmetric structure in solution. It is an effect of the fast rotation of the allyl ligand and the functional groups in the cyclopentadienyl ligands. The lower overall symmetry of compounds 8−10 results in the more complex pattern of the NMR spectra that is further complicated by the appearance of two conformers generated by orientation of the η 3 C3H4COOMe relative to the Cp′ ligand. The endo and exo conformers are in this case observable due to hindered rotation of the bulky allyl ligand. Our measurements show that the endo:exo ratio depends on the sterical hindrance of the substituted cyclopentadienyl ligand. It increases with bulkiness of the substituents in the order 1:1.4 (10), 1:1 (8), and 1.4:1 (9). The assignment of allyl protons to the endo and exo conformers was made according to a study published elsewhere.24 The vibrational spectra of compounds 6−10 show characteristic bands of CO stretching in the range typical for terminal 2194


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Figure 2. ORTEP drawing of the two crystallographically independent molecules of [(η3-C3H4COOMe)(η5-C5H3(COOMe)2)Mo(CO)2] present in the crystal structure of 8. The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

Table 1. Summary of the Infrared and Raman Dataa ν(CO)CO 5 6 7 8 9 10 11 14 9-H a

FTIR Raman FTIR Raman FTIR Raman FTIR FTIR FTIR Raman FTIR Raman FTIR Raman FTIR

1964, 1944, 1950, 1942, 1952, 1941, 1975, 1979, 1954, 1948, 1950, 1865 1988, 1987, 1995,

ν(CO)COR

1881 1861 1871 1870 1862 1875 1901 1909 1876 1881 1861

1704 1703 1736, 1738 1645, 1656, 1714 1710, 1712, 1715,

1890 1902 1941

1716 1723 1712, 1562

1719 1632 1629 1670, 1647 1699 1696

Wavenumbers of the CO stretching bands are given in cm−1.

Scheme 3. Protonation of [(η3-C3H5)(η5-Cp)Mo(CO)2] Figure 3. ORTEP drawing of [(η3-C3H4COOMe)(η5-C5H4COOMe)Mo(CO)2] (10). The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

DFT level support this theory. They show that the oxygen atom of the functional group in compounds 6 and 7 has considerably higher affinity toward proton attack (6-H1 = 37.9 kcal mol−1, 7-H1 = 29.2 kcal mol−1) than the carbon atom of the allyl ligand (6-H2 = 16.9 kcal mol−1, 7-H2 = 18.7 kcal mol−1). The affinities of the different parts of the molecules were calculated from the energies of the starting compounds and differently protonated species according to Scheme 5. In the case of compounds 6 and 7, the species protonated in the functional group of the cyclopentadienyl ring (denoted H1)

have considerably lower energy than those protonated at the allyl ligand (denoted H2). This behavior contrasts that of compound 12, which prefers protonation in the allyl ligand. Although compound 12 also contains an ester group, protonation at this part of the molecule brings considerably lower stabilization (9.9 kcal mol−1) than in the case of the disubstituted analogue (37.9 kcal mol−1). This may be the reason that compound 12 gives under the same conditions cationic cyclopentadienyl species [(η5-C5H4COOMe)Mo(CO)2(NCMe)2][BF4] (13).16 2195


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The splitting of the Mo−Cp′ bond in the protonated analogues of 6 and 7 is very probably induced with acetonitrile. In the case of compound 7, the solution in dichloromethane was treated with one equivalent of HBF4 and analyzed with ESI mass spectrometry. This experiment shows a peak with m/z = 459 and a molybdenum pattern that was assigned to 7-H1. Of course, various dissociative and associative processes could appear under mass spectrometric conditions. Nevertheless, it is very likely that this species is present already in the analyzed solution. The substitution in the allyl ligand with a methoxycarbonyl group has only a minor effect on the protonation reaction. Methoxycarbonyl cyclopentadienyl compounds 8 and 10 behave similarly to their unsubstituted analogues. Disubstituted compound 8 gives cationic allyl compound [(η 3 C3H4COOMe)Mo(CO)2(NCMe)3][BF4] (14). Protonation of monosubstituted compound 10 produces cationic cyclopentadienyl compound [(η5-C5H4COOMe)Mo(CO)2(NCMe)2][BF4] (13); see Scheme 6. The vibrational

Scheme 4. Reaction of Allyl Molybdenum Compounds 6 and 7 with HBF4·Et2Oa

a

6: R = COOMe; 7: R = CONHtBu.

Scheme 6. Reaction of Allyl Molybdenum Compounds 8−10 with HBF4·Et2O

Figure 4. ORTEP drawing of the cation [(η 3 -C 3 H 5 )Mo(CO)2(NCMe)3]+ present in the crystal structure of 11. The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

Scheme 5. Proposed Structures of the Species Protonated in the Cyclopentadienyl (H1) and Allyl Ligand (H2)

spectra of the compound 14 show both antisymmetrical (IR: 1988 cm−1, Raman: 1987 cm−1) and symmetrical CO stretching bands (IR: 1890 cm−1, Raman: 1902 cm−1) at higher frequencies than the unsubstituted analogue 11. This shifting reflects a strong electron-withdrawing effect of the methoxycarbonyl group in the allyl ligand that progressively lowers the electron density at the metal. The positive-ion ESI mass spectrum shows one peak with a molybdenum pattern at m/z = 355. It was assigned to [(C3H4COOMe)Mo(CO)2(NCMe)2]+. The absence of expected [(C3H4COOMe)Mo(CO)2(NCMe)3]+ reflects weak bonding of the acetonitrile ligands. The structure of compound 14 was determined by Xray diffraction analysis (Figure 5). In the case of the tert-butylcarbamoyl-substituted compound 9, the reaction of tetrafluoroboric acid does not lead to acetonitrile complex 14 but produces stable adduct [(η3C3H4COOMe)(η5-C5H3(CONHtBu)2)Mo(CO)2]·HBF4 (9H); see Scheme 6. The integrity of the molecule was evidenced by ESI mass spectrometry. The positive-ion spectrum gives one 2196


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Scheme 7. Reaction of Compound 11 with Cyclopentadiene

X-ray Structures. The structures of compounds 5, 7, 8, 10, 11, and 14 were determined by X-ray diffraction analysis. The bond distances and bond angles describing the coordination around molybdenum are summarized in Tables 2 and 3. Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for Compounds 7, 8, and 10 Mo−C(CO) Mo−Cg(allyl) Mo−Cg(Cp) C(CO)−Mo− C(CO) Cg(allyl)−Mo− Cg(Cp)

3

Figure 5. ORTEP drawing of the cation [(η -C3H4COOMe)Mo(CO)2(NCMe)3]+ present in the crystal structure of 14. The labeling scheme for all non-hydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

7

8 (A)

8 (B)

10

1.944(2) 1.939(2) 2.047(2) 2.034(1) 79.32(7)

1.958(4) 1.947(4) 2.048(5) 2.016(2) 77.50(18)

1.962(4) 1.952(5) 2.054(4) 2.011(2) 80.13(18)

1.946(4) 1.955(4) 2.051(4) 2.011(2) 79.95(16)

129.10(7)

125.50(16)

125.40(13)

128.63(12)

Table 3. Selected Bond Lenghts (Å) and Bond Angles (deg) for Compounds 5, 11, and 14

peak with a molybdenum pattern that was assigned to [(C3H4COOMe)(C5H3(CONHtBu)2)Mo(CO)2 + H]+ (m/z = 517). The inertness of the protonated molecule 9-H toward ligand exchange may be caused by hydrogen bonding between functional groups of the cyclopentadienyl and allyl ligands. The theoretical calculations support this theory. The optimized structure of 9-H contains a hydrogen bond between the protonated carbamoyl group and the oxygen of the ester group (H−OCONHR = 1.029 Å, H···OCOOR = 1.478 Å), which provides 15.2 kcal mol−1 stabilization. Reaction of Compound 11 with Cyclopentadiene. Compounds with weakly bonded acetonitrile ligands may act as precursors of the η5-cyclopentadienyl compounds. The cyclopentadiene coordination is often associated with C−H activation, which can result in aromatization of the cyclopentadienyl and hydrogen transfer. For example, tris-acetonitrile complex [Mo(CO)3(NCMe)3] reacts with cyclopentadienes (Cp′H) to give hydride complexes [η5-Cp′Mo(CO)3H].29 Less reactive [η5-Cp′Mo(CO)2(NCMe)2][BF4] gives stable diene complexes; these undergo hydrogen transfer under photochemical conditions.12 The ability of the allyl complex [(η 3 -C 3 H 5 )Mo(CO)2(NCMe)3][BF4] (11) to assembly the “CpMo” fragment was studied in the reaction with cyclopentadiene. The reaction gives η4-diene compound [(η4-C5H6)(η5-Cp)Mo(CO)2][BF4] (15) in high yield; see Scheme 7. Formation of this product indicates that the expected cyclopentadiene coordination is followed by intramolecular abstraction of the hydrogen (from η4-C5H6) by the neighboring η3-allyl ligand. The appearing η2propene and remaining acetonitrile are then replaced with excess cyclopentadiene. Similar hydrogen migration was previously described for the protonated fluorenyl compound [(η3-C3H5)(η5-Flu)Mo(CO)2].11

Mo−C(CO) Mo−Cg(allyl) Mo−Neq Mo−Leqa Mo−Laxa C(CO)−Mo−C(CO) Cg(allyl)−Mo−Laxa C(CO)−Mo−Neq C(CO)− Mo−Leqa

5

11

14

1.959(4) 1.962(4) 2.053(4) 2.221(3) 2.7236(5) 2.6583(5) 79.76(16) 176.71(11) 170.06(15) 164.39(12)

1.957(5) 1.942(3) 2.043(8) 2.225(2) 2.210(4) 2.187(4) 80.3(2) 173.0(2) 171.10(16) 170.25(17)

1.939(4) 1.985(3) 2.062(4) 2.223(3) 2.214(3) 2.164(3) 79.54(14) 177.03(13) 171.50(12) 165.41(11)

a

5: Leq. = Br1a, Lax. = Br1; 11: Leq. = N2, Lax. = N1; 14: Leq. = N2, Lax. = N3.

Compound 5 is a dimer with two [(η3-C3H4COOMe)Mo(CO)2(NCMe)] units bridged via two bromine atoms; see Figure 6. The molecule has rigorous overall Ci symmetry. Donor atoms of the coordinated ligands form a distorted octahedron around molybdenum. The centroid of the allyl ligand and bromide ligand (Br1) are placed in axial positions, while the second bromide ligand (Br1a), nitrogen atom of the acetonitrile (N1), and two carbon atoms of the carbonyl ligands (C6 and C7) are in equatorial positions. The carbonyl ligands are cis-coordinated. The bond distance between molybdenum and the axial bromide ligand was found to be considerably shorter (Mo−Br1 = 2.6583(5) Å) than in the case of the equatorial bromide ligand (Mo−Br1a = 2.7236(5) Å). It is a result of the trans-effect of the carbonyl ligands.30 The molecules of the compounds 7, 8, and 10 have distorted tetrahedral structure with one η3-allyl, one η5-cyclopentadienyl, and two carbonyls around molybdenum in oxidation state II. The allyl ligands are in exo-conformation (Figures 1−3). Compound 8 has two crystallographically independent but essentially the same complexes in the unit cell. The angles 2197


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molybdenum and equatorial nitrogen atoms. This is caused by the trans-effect of the carbonyl ligands.30 The structural data of compound 11 are in the line with those previously reported for [(η3 -C3H 5)Mo(CO) 2(NCMe)3][{(η3 -C3 H5)Mo(CO)2}2 (μCl)3].31 The ester group in compound 14 seems to be fully conjugated with allyl. The interplanar angle between the COO group and allyl (PlC1,C2,C3−PlC4,O1,O2 = 2.5(6)°) is considerably lower than in the case of the other molybdenum(II) compounds containing a η3-bonded methoxycaronyl allyl ligand (5: PlC1,C2,C3−PlC4,O1,O2 = 5.3(6)°, 9: PlC10,11,12−PlC13,O5,O6 = 13.5(7)°, PlC26,C27,C28−PlC29,O13,O14 = 9.1(7)°, 10: PlC8,C9,C10− PlC11,O3,O4 = 16.5(6)°).

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CONCLUSIONS

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EXPERIMENTAL SECTION

Reaction of ring-substituted molybdenum(II) compounds of formula [(η3-C3H5)(η5-Cp′)Mo(CO)2] with tetrafluoroboric acid leads to different outcomes depending on the nature of the attached substituents. The compounds with two neighboring ester or carbamoyl groups produce cationic allyl compound [(η3-C3H5)Mo(CO)2(NCMe)3][BF4] (11), while the unsubstituted counterpart gives cationic cyclopentadienyl compound [(η5-C5H5)Mo(CO)2(NCMe)2][BF4]. We have previously observed that the attachment of only one COOMe group at the Cp ligand does not influence the reaction path.16 The herereported unexpected switch of the reactivity can be explained by much higher affinity of the functional groups in the cyclopentadienyl toward protonation. The second electronwithdrawing group crosses the borderline between attack of the allyl and cyclopentadienyl ligands. Cationic species containing both coordinated allyl and cyclopentadienyl ligands can be stabilized through the functionalization of the allyl ligand, as was evidenced in compound 9-H. Theoretical calculations show that this species is stabilized through hydrogen bonding between functional groups of the allyl and cyclopentadienyl ligands.

Figure 6. ORTEP drawing of [{(η 3 -C 3 H 4 COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5). The labeling scheme for all nonhydrogen atoms is shown. Thermal ellipsoids are drawn at the 30% probability level.

between molybdenum and the centroids of allyl and cyclopentadienyl were found to be in a narrow range of 125.40(13)− 129.10(7)°. The C(CO)−Mo−C(CO) angles vary between 77.50(18)° and 80.13(18)°. In compounds 7 and 8, the functional groups are not fully conjugated with the cyclopentadienyl ring. The COX groups are rotated around the Cipso−CCOX bond. The orientation of the carbamoyl groups of compound 7 (PlC1−C5−PlC6,O1,N1 = 26.8(2)°, PlC1−C5−PlC11,O2,N2 = 15.5(2)°) is stabilized by an intramolecular hydrogen bond between the proton of one carbamoyl group and the oxygen atom of the second carbamoyl group (N2···O1 = 2.752(2) Å). The ester groups in compound 8 do not provide similar hydrogen bonding. The C−O oxygen atoms of the COOMe groups are pointed apart. The interplanar angles between the ester group and Cp ring vary between 22.4(5)° and 28.8(5)°. These values are considerably higher than in the case of monosubstituted analogues [(η3C3H4COOMe)(η5-C5H4COOMe)Mo(CO)2] (10: PlC1−C5− PlC6,O1,O2 = 6.7(5)°) and [(η3-C3H5)(η5-C5H4COOMe)Mo(CO)2] (12: PlC1−C5−PlC6,O1,O2 = 6.1(3)°).16 The cationic parts of complexes 11 and 14 have a distorted octahedral structure with the centroid of the allyl ligand and nitrogen atom of the acetonitrile in the axial positions. The carbon atoms of two carbonyl ligands and the nitrogen atoms of two acetonitrile ligands are placed in equatorial positions; see Figures 4 and 5. The carbonyl ligands are cis-coordinated. The bond distances between molybdenum and axial nitrogen atoms were found to be considerably shorter than those between

Methods and Materials. All operations were performed under nitrogen using conventional Schlenk-line techniques. The solvents were purified and dried by standard methods.32 Starting materials were available commercially or prepared according to literature procedures: Na[C5H3(COOMe)2] (1-Na),18 Na[C5H3(CONHtBu)2] (2-Na),22 Na[C5H4COOMe] (3-Na),33 and [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (4).23 Measurements. 1H and 13C{1H} NMR spectra were measured in CDCl3 and CD3CN solutions on a Bruker Avance 400 spectrometer at room temperature. Chemical shifts are given in ppm relative to TMS. The infrared spectra were recorded in the 4000−400 cm−1 region (2 cm−1 steps) on a Nicolet Magna 550 FTIR spectrometer in a Nujol mull between KBr windows. Solution spectra were measured in CsI cuvettes. Raman spectra were run on a Bruker IFS 55 equipped with an FRA 106 extension at 50−3500 cm−1 in quartz capillaries. Mass spectrometry was performed on an LCMS 2010 quadrupole mass spectrometer (Shimadzu, Japan). The sample was injected into the mass spectrometer with infusion mode at a constant flow rate of 10 μL/min, and electrospray ionization-mass spectrometry (ESI-MS) was used for identification of analyzed samples. X-ray Structure Determination. The X-ray data (Table 4) for crystals of compounds 5, 7, 8, 10, 11, and 14 were obtained at 150 K using an Oxford Cryostream low-temperature device on a Nonius KappaCCD diffractometer with Mo Kα radiation (λ = 0.71073 Å) and a graphite monochromator. Data reductions were performed with DENZO-SMN.34 The absorption was corrected by integration methods.35 Structures were solved by direct methods (Sir92)36 and refined by full-matrix least-squares based on F2 (SHELXL97).37 2198


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Table 4. Crystallographic Data of Molybdenum Compounds 5

7

formula

C18H20Br2Mo2N2O2

C20H28MoN2O4

fw temp (K) cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z Dc (g cm−3) μ (mm−1) F(000) cryst size (mm) θ range index ranges

744.06 150(1) monoclinic P21/c 9.2980(4) 12.3701(4) 10.5919(4) 90 101.320(3) 90 1194.55(8) 2 2.069 4.440 720 0.18 × 0.18 × 0.14 2.23−27.50 −10 ≤ h ≤ 12 −16 ≤ k ≤ 16 −13 ≤ l ≤ 13 11 279 2190 (Rint = 0.0632) 145 R1 = 0.0338 wR2 = 0.0664 R1 = 0.0501 wR2 = 0.0735 0.563, −0.727

456.38 150(1) triclinic P1̅ 10.1270(4) 10.7620(4) 10.8101(5) 66.654(4) 77.431(4) 84.127(4) 1055.61(8) 2 1.436 0.647 472 0.18 × 0.18 × 0.14 2.06−27.50 −13 ≤ h ≤ 13 −13 ≤ k ≤ 13 −14 ≤ l ≤ 14 21 051 4438 (Rint = 0.0299) 244 R1 = 0.0217 wR2 = 0.0511 R1 = 0.0255 wR2 = 0.0536 0.376, −0.565

reflns collected indep reflns params final R indices [I > 2σ(I)]a,b final R indices (all data)a,b largest diff peak and hole (e Å−3) a

8 C16H16MoO8

10 C14H14MoO6

11

C11H14MoN3O, BF4 432.23 374.19 403.00 150(1) 150(1) 150(1) monoclinic triclinic orthorhombic P21/c P1̅ Pna21 33.9870(12) 7.5069(5) 21.3469(3) 7.2670(6) 9.9120(5) 7.4500(6) 13.8271(12) 10.4911(8) 10.1251(11) 90 82.833(5) 90 94.584(5) 75.196(5) 90 90 72.820(4) 90 3404.1(4) 720.01(8) 1610.2(2) 8 2 4 1.687 1.726 1.662 0.812 0.935 0.862 1744 376 800 0.47 × 0.20 × 0.09 0.57 × 0.22 × 0.15 0.57 × 0.22 × 0.15 1.80−27.40 2.01−27.50 2.77−27.50 −44 ≤ h ≤ 44 −9 ≤ h ≤ 9 −27 ≤ h ≤ 25 −8 ≤ k ≤ 9 −12 ≤ k ≤ 11 −9 ≤ k ≤ 7 −17 ≤ l ≤ 16 −13 ≤ l ≤ 13 −10 ≤ l ≤ 13 28 542 12 690 6917 6225 2959 2737 (Rint = 0.0558) (Rint = 0.0680) (Rint = 0.0311) 451 190 199 R1 = 0.0463 R1 = 0.0368 R1 = 0.0279 wR2 = 0.0867 wR2 = 0.0838 wR2 = 0.0657 R1 = 0.0653 R1 = 0.0456 R1 = 0.0347 wR2 = 0.0935 wR2 = 0.0883 wR2 = 0.0697 1.195, −0.608 0.765, −0.712 0.447, −0.607

14 C13H16MoN3O4, BF4 461.04 150(1) monoclinic C21/c 27.3613(11) 13.4790(3) 10.7391(8) 90 107.741(5) 90 3772.3(3) 8 1.624 0.755 1840 0.26 × 0.20 × 0.06 1.56−27.50 −35 ≤ h ≤ 32 −17 ≤ k ≤ 16 −11 ≤ l ≤ 13 16 940 3346 (Rint = 0.0551) 235 R1 = 0.0384 wR2 = 0.0665 R1 = 0.0616 wR2 = 0.0747 0.441, −0.558

R1 = ∑||Fo| − |Fc||/∑|Fo|. bwR2 = (∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2])1/2. (CO)2(NCMe)2Cl] (4; 1.55 g, 5 mmol) precooled to −80 °C. The reaction mixture was stirred at room temperature overnight and then vacuum evaporated to dryness. The solid residue was extracted with hot hexane. The yellow extract was vacuum evaporated to dryness. The crude product was recrystallized from a mixture of hexane−Et2O at −60 °C. Yield: 1.08 g (2.9 mmol, 58%). Anal. Calcd for C14H14MoO6: C, 44.94; H, 3.77. Found: C, 44.76; H, 3.89. 1H NMR (CDCl3, 500 MHz, δ ppm): 5.79 (s-br, 2H, C5H3), 5.41 (s-br, 1H, C5H3), 3.79 (s, 6H, COOCH3), 3.72 (m 1H, meso of C3H5), 2.83 (s-br, 2H, syn of C3H5), 1.12 (d, 3J(1H,1H) = 10.3 Hz, 2H, anti of C3H5). FTIR (Nujol, cm−1): 3115 s [ν(CH)], 1950 vs [νa(CO)CO], 1871 vs [ν s (CO) CO ], 1736 vs [ν a (CO) COOMe ], 1719 vs [νs(CO)COOMe]. Raman (quartz capillary, cm−1): 3010(7) [ν(CH)], 2960(8) [ν(CH)], 1942(5) [νa(CO)CO], 1870(10) [νs(CO)CO], 1738(9) [ν(CO)COOMe]. Synthesis of [(η3-C3H5)(η5-C5H3(CONHtBu)2)Mo(CO)2] (7). The reaction was carried out as described for compound 6, but with Na[C5H3(CONHtBu)2] (2-Na; 1.43 g, 5 mmol) and [(η3-C3H5)Mo(CO)2(NCMe)2Cl] (4; 1.55 g, 5 mmol). The crude product was purified by vacuum sublimation (120 °C; 10 Pa). Yield: 1.78 g (3.9 mmol, 78%). Anal. Calcd for C20H28MoN2O4: C, 52.63; H, 6.18; N, 6.14. Found: C, 52.49; H, 6.12; N, 6.19. 1H NMR (CDCl3, 360 MHz, δ ppm): 7.86 (s, 2H, NH), 5.70 (s-br, 2H, C5H3), 5.42 (s-br, 1H, C5H3), 3.85 (s-br 1H, meso of C3H5), 2.81 (s-br, 2H, syn of C3H5), 1.40 (s, 18H, C(CH3)3), 1.12 (s-br, 2H, anti of C3H5). FTIR (Nujol, cm−1): 3341 m-br [ν(NH)], 3238 m-br [ν(NH)], 3035 m-br [ν(CH)Cp], 1952 vs [νa(CO)CO], 1862 vs [νs(CO)CO], 1645 vs [νa(CO)CONH], 1632 vs, [νs(CO)CONH]. FTIR (CCl4 solution, cm−1): 3445 w [ν(NH)], 3257 m [ν(NH)], 3215 m [ν(NH)], 3062 [ν(CH)], 2968 s [ν(CH)], 1961 vs [νa(CO)CO], 1884 vs [νs(CO)CO], 1666 s

Hydrogen atoms were mostly localized on a difference Fourier map. However, to ensure uniformity of the treatment of the crystal, all hydrogen atoms were recalculated into idealized positions (riding model) and assigned temperature factors Uiso(H) = 1.2[Ueq(pivot atom)] or 1.5Ueq for the methyl moiety with C−H = 0.96, 0.97, and 0.93 Å for methyl, methylene, and hydrogen atoms in the aromatic rings or the allyl moiety, respectively. Synthesis of [{(η3-C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5). A suspension of [Mo(CO)6] (10 g; 38 mmol) in acetonitrile (50 mL) was refluxed overnight. The yellow solution was cooled to 0 °C, and an excess of methyl trans-4-bromo-2-butenoate (6 mL; 47 mmol) was added dropwise. During the treatment CO evolution was observed and the color of the solution turned dark red. The reaction mixture was stirred overnight at room temperature and then vacuum evaporated. A red solid of the crude product was dissolved in dichloromethane and treated with hexane to give an orange-red precipitate of the product. Yield: 14.7 g (36 mmol, 94%). Anal. Calcd for C18H20O8Mo2N2Br2: C, 29.06; H, 2.71; N, 3.77. Found: C, 29.28; H, 2.56; N, 3.89. 1H NMR (CD3CN, 400 MHz, δ ppm): 4.67 (dd, 2H, C3H4), 3.66 (s, 6H, COOCH3), 3.31 (d, J(1H,1H) = 6.4 Hz, 2H, C3H4), 1,85 (d, J(1H,1H) = 8.8 Hz, 2H, C3H4), 1.39 (d, J(1H,1H) = 9.2 Hz, 2H, C3H4). FTIR (Nujol, cm−1): 1964 vs [νa(CO)CO], 1881 vs [νs(CO)CO], 1704 vs [ν(CO)COOMe]. Raman (quartz capillary, cm−1): 3001(10) [ν(CH)], 1944(6) [ν a (CO) CO ], 1861(8) [ν s (CO) CO ], 1703(6) [ν(CO)COOMe]. Single crystals suitable for X-ray diffraction analysis were obtained by the vapor diffusion of Et2O into a saturated solution of 5 in dichloromethane at room temperature. Synthesis of [(η3-C3H5)(η5-C5H3(COOMe)2)Mo(CO)2] (6). Na[C5H3(COOMe)2] (1-Na; 1.02 g, 5 mmol) was dissolved in THF (15 mL) and added dropwise to a THF solution of [(η3-C3H5)Mo2199


Organometallics

Article

2.34 (d, J(1H,1H) = 9.2 Hz, 1H of endo, C3H4), 1.84 (d, J(1H,1H) = 10.8 Hz, 1H of endo, C3H4), 1.75 (d, J(1H,1H) = 9.2 Hz, 1H of exo, C3H4), 1.31 (dd, J(1H,1H) = 11.2 Hz, J(1H,1H) = 1.6 Hz, 1H of exo, C3H4). FTIR (Nujol, cm−1): 3107 m [ν(CH)], 1954 vs [νa(CO)CO], 1876 vs [νs(CO)CO], 1712 s [ν(CO)COOMe], 1699 vs [ν(CO)COOMe]. Raman (quartz capillary, cm−1): 3111(2) [ν(CH)], 3040(2) [ν(CH)], 3005(1) [ν(CH)], 2955(4) [ν(CH)], 1948(5) [νa(CO)CO], 1881(10) [νs(CO)CO], 1715(5) [ν(CO)COOMe], 1696(5) [ν(CO)COOMe]. Single crystals suitable for X-ray diffraction analysis were obtained by the vacuum sublimation of 10 in a flame-sealed ampule at 85 °C (1 Pa). Synthesis of [(η3-C3H5)Mo(CO)2(NCMe)3][BF4] (11). Method a: [(η3-C3H5)(η5-C5H3(COOMe)2)Mo(CO)2] (6; 0.37 g, 1 mmol) was dissolved in a mixture of dichloromethane (20 mL) with acetonitrile (1 mL). The solution was treated with 1 equiv of HBF4·Et2O at 0 °C. After 10 min the reaction was warmed to room temperature and stirred for two more hours. The reaction mixture was concentrated in vacuo to ∼2 mL, and Et2O was added to precipitate the yellow solid. The crude product was washed with Et2O and vacuum-dried. Recrystallization from MeCN−Et2O gave a yellow powder of the product. Yield: 0.22 g (0.55 mmol, 55%). Anal. Calcd for C11H14BF4MoN3O2: C, 32.78; H, 3.50; N, 10.43. Found: C, 32.62; H, 3.41; N, 10.35. Positive-ion MS (MeCN): m/z = 318 [M]+, 277 (100%) [M − MeCN]+. 1H NMR (CDCl3, 360 MHz, δ ppm): 3.91 (m, 1H, meso of C3H5), 3.41 (d, J(1H,1H) = 6.4 Hz, 2H, syn of C3H5), 2.50 (s-br, 3H, CH3CN), 2.31 (s-br, 6H, CH3CN), 1.36 (d, J(1H,1H) = 9.8 Hz, 2H, anti of C3H5). 13C NMR (CDCl3, 90 MHz, δ ppm): 220.3 (CO), 102.2 (CH3CN), 73.0 (1C, C3H5), 59.6 (2C, C3H5), 3.4 (CH3CN). FTIR (Nujol, cm−1): 2359 m [νa(CN)], 2316 m [νa(CN)], 2291 m [νs(CN)], 1950 vs [νa(CO)CO], 1861 vs [νs(CO)CO], 1054 vs-br [νa(BF)]. Raman (quartz capillary, cm−1): 3095(1), 3071(1), 3017(2), 2943(6), 2319(5) [νa(CN)], 2295(10) [νs(CN)], 1865(5) [νs(CO)CO], 950(3) [νs(BF)]. The spectroscopic data obtained for compound 11 are consistent with those previously reported for [(η3-C3H5)Mo(CO)2(NCMe)3][PF6] (11-PF6). Large single crystals suitable for X-ray diffraction analysis were obtained by careful overlayering of the MeCN solution of 11 with ether. Method b: A solution of [(η3-C3H5)(η5-C5H3(CONHtBu)2)Mo(CO)2] (7; 0.46 g, 1 mmol) was used instead of compound 6. Yield: 0.19 g (0.47 mmol, 47%). Synthesis of [(η5-C5H4COOMe)Mo(CO)2(NCMe)2][BF4] (13). The reaction was carried out as described for compound 11, but with [(η3-C3H4COOMe)(η5-C5H4COOMe)Mo(CO)2] (10; 0.37 g, 1 mmol). Yield: 0.40 g (0.90 mmol, 90%). Analytic and spectroscopic data are in agreement with the literature.16 Synthesis of [(η3-C3H4COOMe)Mo(CO)2(NCMe)3][BF4] (14). The reaction was carried out as was described for compound 11, but with [(η3-C3H4COOMe)(η5-C5H3(COOMe)2)Mo(CO)2] (8; 0.43 g, 1 mmol). Yield: 0.24 g (0.52 mmol, 52%). Anal. Calcd for C13H16BF4MoN3O4: C, 33.87; H, 3.50; N, 9.11. Found: C, 33.75; H, 3.46; N, 9.09. Positive-ion MS (MeCN): m/z = 335 (100%) [M − MeCN]+. 1H NMR (CD3CN, 400 MHz, δ ppm): 4.63 (m, 1H, C3H4), 3.74 (s, 3H, C3H4COOCH3), 3.66 (d, J(1H,1H) = 6.8 Hz, 1H, C3H5), 2.18 (s-br, 9H, CH3CN), 1.92 (d, J(1H,1H) = 9.2 Hz, 1H, C3H5), 1.72 (d, J(1H,1H) = 9.6 Hz, 1H, C3H5). FTIR (Nujol, cm−1): 2360 m [ν a (CN)], 2321 m [ν a (CN)], 2291 m [ν s (CN)], 1988 vs [νa(CO)CO], 1890 vs [νs(CO)CO], 1716 vs [ν(CO)COOMe], 1060 vs-br [νa(BF)]. Raman (quartz capillary, cm−1): 3015(2), 2945(3), 2317(5) [νa(CN)], 2290(10) [νs(CN)], 1987(2) [ν(CO)CO], 1902(4) [νs(CO)CO], 1723(1) [ν(CO)COOMe], 945(4) [νs(BF)]. Single crystals suitable for X-ray diffraction analysis were obtained by careful overlayering of the CH2Cl2 solution of 14 with hexane. Synthesis of [(η 3 -C 3 H 4 COOMe)(η 5 -C 5 H 3 (CONH t Bu) 2 )Mo(CO)2]·HBF4 (9-H). The reaction was carried out as was described for compound 11, but with [(η3-C3H4COOMe)(η5C5H3(CONHtBu)2)Mo(CO)2] (9; 0,46 g, 1 mmol). The crude product was washed with hexane and extracted with Et2O. The vacuum evaporation of the solvents gave a yellow, oily solid that was twice recrystallized from mixtures of MeCN−Et2O and CH2Cl2− hexane. Yield: 0.24 g (0.40 mmol, 40%). Anal. Calcd for

[νa(CO)CONH], 1645 s [νs(CO)CONH]. Raman (quartz capillary, cm−1): 3132(2), 3111(2), 3072(2), 3046(2), 3005(4), 2987(3), 2972(4), 2933(4), 1941(5) [νa(CO)CO], 1875(10) [νs(CO)CO], 1656(1) [νa(CO)CONH], 1629(1) [νs(CO)CONH]. Single crystals suitable for X-ray diffraction analysis were obtained by vacuum sublimation of 7 in a flame-sealed ampule at 113 °C (1 Pa). Synthesis of [(η3-C3H4COOMe)(η5-C5H3(COOMe)2)Mo(CO)2] (8). The reaction was carried out as was described for compound 6, but with Na[C5H3(COOMe)2] (1-Na; 1.02 g, 5 mmol) and [{(η3C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5; 1.86 g, 2.5 mmol). The crude product was recrystallized from a mixture of hexane−Et2O at −60 °C. Yield: 0.80 g (1.9 mmol, 37%). Anal. Calcd for C16H16MoO8: C, 44.46; H, 3.73. Found: C, 44.62; H, 3.76. 1H NMR (CDCl3, 400 MHz, δ ppm): 1:1 mixture of endo and exo conformers; 5.84−5.75 (m, 2H of exo and 2H of endo, C5H3), 5.44, 5.22 (2 × t, J(1H,1H) = 3.0 Hz, 1H of exo and 1H of endo, C5H3), 4.99 (m, 1H of exo, C3H4), 4.25 (m, 1H of endo, C3H4), 3.85, 3.71 (2 × s, 6H of exo and 6H of endo, C5H3COOCH3), 3.79 (2 × s, 3H of exo and 3H of endo, C3H4COOCH3), 3.04 (d, J(1H,1H) = 6.8 Hz, 1H of endo, C3H4), 2.95 (d, J(1H,1H) = 7.6 Hz, 1H of exo, C3H4), 2.54 (d, J(1H,1H) = 9.2 Hz, 1H of endo, C3H4), 2.04 (d, J(1H,1H) = 11.2 Hz, 1H of endo, C3H4), 1.79 (d, J(1H,1H) = 9.6 Hz, 1H of exo, C3H4), 1.41 (d, J(1H,1H) = 11.2 Hz, 1H of exo, C3H4). FTIR (Nujol, cm−1): 3110 m-br [ν(CH)Cp], 1975 vs [νa(CO)CO], 1901vs [νs(CO)CO], 1714 vs-br [ν(CO)COOMe]. Single crystals suitable for X-ray diffraction analysis were obtained by the vacuum sublimation of 8 in a flamesealed ampule at 85 °C (1 Pa). Synthesis of [(η3-C3H4COOMe)(η5-C5H3(CONHtBu)2)Mo(CO)2] (9). The reaction was carried out as was described for compound 6, but with Na[C5H3(CONHtBu)2] (2-Na; 1.43 g, 5 mmol) and [{(η3C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5; 1.86 g, 2.5 mmol). The crude product was purified by vacuum sublimation (150 °C; 10 Pa). Yield: 0.94 g (2.1 mmol, 41%). Anal. Calcd for C22H30MoN2O6: C, 51.36; H, 5.88; N, 5.45. Found: C, 51.29; H, 5.83; N, 5.39. 1H NMR (CDCl3, 400 MHz, δ ppm): 1.4:1 mixture of endo and exo conformers; 8.30 (s, 1H of exo, NH), 8.25 (s, 1H of endo, NH), 7.83 (s, 1H of exo, NH), 7.54 (s, 1H of endo, NH), 5.87 (br-s, 1H of exo, C5H3), 5.84 (br-s, 1H of endo, C5H3), 5.79 (br-s, 1H of endo, C5H3), 5.57 (br-s, 1H of exo, C5H3), 5.39 (br-s, 1H of endo, C5H3), 5.30 (br-s, 1H of exo, C5H3), 4.84 (m, 1H of exo, C3H4), 4.54 (m, 1H of endo, C3H4), 3.70, 3.71 (2 × s, 3H of exo and 3H of endo, C3H4COOCH3), 3.07 (d, J(1H,1H) = 6.8 Hz, 1H of endo, C3H4), 2.82 (d, J(1H,1H) = 7.2 Hz, 1H of exo, C3H4), 2.34 (d, J(1H,1H) = 9.2 Hz, 1H of endo, C3H4), 1.99 (d, J(1H,1H) = 10.8 Hz, 1H of endo, C3H4), 1.75 (d, J(1H,1H) = 9.2 Hz, 1H of exo, C3H4), 1.43 (d, 1H of exo, C3H4), 1.41 (s, 18H of exo and 18H of endo, NHC(CH3)3). FTIR (Nujol, cm−1): 3270 m [ν(NH)], 3204 m [ν(NH)], 1977 vs [ν(CO)CO], 1954 vs [ν(CO)CO], 1907 vs [ν(CO)CO], 1895 vs [ν(CO)CO], 1880 vs [ν(CO)CO], 1709 vs [ν(CO)COOMe], 1649 vs [νa(CO)CONH], 1631 s [νs(CO)CONH]. FTIR (CCl4 solution, cm−1): 3263 m [ν(NH)], 3221 m [ν(NH)], 3062 [ν(CH)], 2968 s [ν(CH)], 1979 vs [νa(CO)CO], 1909 vs [νs(CO)CO], 1710 s [ν(CO)COOMe], 1670 s [νa(CO)CONH], 1647 s [νs(CO)CONH]. Raman (quartz capillary, cm−1): 2928(10) [ν(CH)], 1971(4) [ν(CO)CO], 1954(7) [ν(CO)CO], 1914(9) [ν(CO)CO], 1863(9) [ν(CO)CO], 1710(7) [ν(CO)COOMe], 1621(3) [νs(CO)CONH]. Synthesis of [(η3-C3H4COOMe)(η5-C5H4COOMe)Mo(CO)2] (10). The reaction was carried out as was described for compound 6, but with Na[C5H4COOMe] (3-Na; 0.73 g, 5 mmol) and [{(η3C3H4COOMe)Mo(CO)2(NCMe)(μ-Br)}2] (5; 1.86 g, 2.5 mmol). The crude product was purified by recrystallization from hexane. Yield: 0.90 g (2.4 mmol, 48%). Anal. Calcd for C14H14MoO6: C, 44.94; H, 3.77. Found: C, 44.79; H, 3.87. 1H NMR (CDCl3, 400 MHz, δ ppm): 1:1.4 mixture of endo and exo conformers; 5.84, 5.81 (2 × m, 2H of exo, C5H3), 5.77, 5.75 (2 × m, 2H of endo, C5H3), 5.43−5.37 (m, 1H of exo and 2H of endo, C5H3), 5.23 (m, 1H of exo, C5H3), 4.88 (m, 1H of exo, C3H4), 4.47 (m, 1H of endo, C3H4), 3.81 (s, 3H of exo, COOCH3), 3.75 (s, 3H of endo, COOCH3), 3.69 (s, 3H of exo and 3H of endo, COOCH3), 2.93 (d, J(1H,1H) = 6.4 Hz, 1H of endo, C3H4), 2.77 (dd, J(1H,1H) = 7.4 Hz, J(1H,1H) = 1.8 Hz, 1H of exo, C3H4), 2200


Organometallics

Article

C22H31BF4MoN2O6: C, 43.88; H, 5.19; N, 4.65. Found: C, 43.68; H, 5.32; N, 4.59. Positive-ion MS (CH2Cl2): m/z = 517 [M]+. 1H NMR (CDCl3, 400 MHz, δ ppm): 2:1 mixture of endo and exo conformers; 8.26 (br-s, 1H of exo and 1 H of endo, OH), 7.63, 7.60 (2 × s, 2H of exo, NH), 7.55, 7.52 (2 × s, 2H of endo, NH), 6.39 (br-s, 1H of exo and 1 H of endo, C5H3), 6.34 (br-s, 1H of exo and 1 H of endo, C5H3), 5.69 (br-s, 1H of endo, C5H3), 5.50 (br-s, 1H of exo, C5H3), 5.17 (m, 1H of exo, C3H4), 4.63 (m, 1H of endo, C3H4), 3.77 (s, 3H of exo, C3H4COOCH3), 3.75 (s, 3H of exo, C3H4COOCH3), 3.04 (d, 1H of exo and 1H of endo, C3H4), 2.75 (d, J(1H,1H) = 9.1 Hz, 1H of endo, C3H4), 2.48 (d, J(1H,1H) = 11.1 Hz, 1H of endo, C3H4), 1.84 (d, J(1H,1H) = 9.9 Hz, 1H of exo, C3H4), 1.59 (d, 1H of exo, C3H4), 1.49, 1.45, 1.44 (3 × s, 18H of exo and 18H of endo, NHC(CH3)3). FTIR (CDCl3 solution, cm−1): 3218 s-br [ν(NH)], 2978 m [ν(CH)], 1995 vs [νa(CO)CO], 1941 vs [νs(CO)CO], 1920 s [νs(CO)CO], 1712 m [ν(CO)COOMe], 1562 vs [ν(CO)CONH]. Synthesis of [(η4-C5H6)(η5-Cp)Mo(CO)2][BF4] (15). The solution of [(η3-C3H5)Mo(CO)2(NCMe)3][BF4] (11 0.40 g, 1 mmol) in dichloromethane was treated with an excess of cyclopentadiene (0.5 mL). After stirring the reaction mixture for 16 h, the volatiles were vacuum evaporated. The crude product was washed with ether and recrystallized from dichloromethane−ether. The obtained yellow powder was vacuum-dried. Yield: 0.32 g (0.86 mmol, 86%). Analytic and spectroscopic data are in agreement with the literature.12 Computational Details. Theoretical calculations were performed using the Gaussian 09 software package38 and the PBE1PBE functional39 without symmetry constraints. The geometries of all species were optimized with the LanL2DZ basis set40 augmented with a f-polarization function41 for Mo and a standard 6-31G(d,p) set42 for the remaining elements. Frequency calculations were performed to confirm the nature of the minima and to get zero-point energies (ZPE). Energy values reported in the text include ZPE corrections.

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Antunes, M. M.; Gago, S.; Paz, F. A. A.; Rodrigues, A. E.; Pillinger, M.; Gonçalves, I. S.; Silva, C. M.; Valente, A. A. J. Mol. Catal. A: Chem. 2010, 320, 19−26. (e) Reis, P. M.; Gamelas, C. A.; Brito, J. A.; Saffon, N.; Gómez, M.; Royo, B. Eur. J. Inorg. Chem. 2011, 666−673. (f) Betz, D.; Raith, A.; Cokoja, M.; Kühn, F. E. ChemSusChem 2010, 2010, 559−562. (g) Neves, P.; Pereira, C. C. L.; Paz, F. A. A.; Gago, S.; Pillinger, M.; Silva, C. M.; Valente, A. A.; Romão, C. C.; Gonçalves, I. S. J. Organomet. Chem. 2010, 695, 2311−2319. (4) Gamelas, C. A.; Lourenço, T.; da Costa, A. P.; Simplício, A. L.; Royo, B.; Romão, C. C. Tetrahedron Lett. 2008, 49, 4708−4712. (5) Balzarek, C.; Tyler, D. R. Angew. Chem., Int. Ed. 1999, 38, 2406− 2408. (6) Kuo, L. Y.; Finigan, D. M.; Tadros, N. N. Organometallics 2003, 22, 2422−2425. (7) Breno, K. L.; Pluth, M. D.; Tyler, D. R. Organometallics 2003, 22, 1203−1211. Ahmed, T. J.; Tyler, D. R. Organometallics 2008, 27, 2608−2613. (8) (a) Kuo, L. Y.; Kuhn, S.; Ly, D. Inorg. Chem. 1995, 34, 5341− 5345. (b) Kuo, L. Y.; Adint, T. T.; Akagi, A. E.; Zakharov, L. Organometallics 2008, 27, 2560−2564. (9) (a) Köpf-Maier, P.; Leitner, M.; Voigtlander, R.; Köpf, H. Z. Naturforsch. (C) 1979, 34, 1174−1176. (b) Harding, M. M.; Mokdsi, G. Curr. Med. Chem. 2000, 7, 1289−1303. (10) Norton de Matos, M. R. P.; Romão, C. C.; Pereira, C. C. L.; Rodrigues, S. S.; Mora, M.; Silva, M. J. P.; Alves, P. M.; Reis, C. A. International Patent WO/2005/087783. (11) Romão, C. C. Appl. Organomet. Chem. 2000, 14, 539−548. (12) Ascenso, J. R.; de Azevedo, C. G.; Gonçalves, I. S.; Herdtweck, E.; Moreno, D. S.; Pessanha, M.; Romão, C. C. Organometallics 1995, 14, 3901−3919. (13) Gamelas, C. A.; Herdtweck, E.; Lopes, J. P.; Romão, C. C. Organometallics 1999, 18, 506−515. (14) Gonçalves, I. S.; Romão, C. C. J. Organomet. Chem. 1995, 486, 155−161. (15) Gonçalves, I. S.; Herdtweck, E.; Romão, C. C.; Royo, B. J. Organomet. Chem. 1999, 580, 169−177. (16) Honzíček, J.; Mukhopadhyay, A.; Silva, T. S.; Romão, M. J.; Romão, C. C. Organometallics 2009, 28, 2871−2879. (17) (a) Honzíček, J.; Paz, F. A. A.; Romão, C. C. Eur. J. Inorg. Chem. 2007, 2827−2838. (b) Honzíček, J.; Romão, C. C.; Calhorda, M. J.; Mukhopadhyay, A.; Vinklárek, J.; Padělková, Z. Organometallics 2011, 30, 717−725. (18) Busetto, L.; Cassani, C.; Zanotti, V.; Albano, V. G.; Sabatino, P. Organometallics 2001, 20, 282−288. (19) Klaß, K.; Fröhlich, R.; Erker, G. J. Chem. Soc., Dalton Trans. 1999, 4457−4461. (20) Eisenstecken, D.; Enk, B.; Kopacka, H.; Wurst, K.; Müller, T.; Pevny, F.; Winter, R. F.; Bildstein, B. Eur. J. Inorg. Chem. 2011, 2958− 2966. (21) Enk, B.; Eisenstecken, D.; Kopacka, H.; Wurst, K.; Müller, T.; Pevny, F.; Winter, R. F.; Bildstein, B. Organometallics 2010, 29, 3169− 3178. (22) Klaß, K.; Duda, L.; Kleigrewe, N.; Erker, G.; Fröhlich, R.; Wegelius, E. Eur. J. Inorg. Chem. 1999, 11−19. (23) Faller, J. W.; Chen, C. C.; Mattina, M. J.; Jakubowski, A. J. Organomet. Chem. 1973, 52, 361−386. (24) Vong, W. J.; Peng, S. M.; Lin, S. H.; Lin, W. J.; Liu, R. S. J. Am. Chem. Soc. 1991, 113, 573−582. (25) Markham, J.; Menard, K.; Cutler, A. Inorg. Chem. 1985, 24, 1581−1587. (26) Pereira, C. C. L.; Braga, S. S.; Paz, F. A. A.; Pillinger, M.; Klinowski, J.; Gonçalves, I. S. Eur. J. Inorg. Chem. 2006, 4278−4288. (27) Honzíček, J.; Mukhopadhyay, A.; Bonifacio, C.; Romão, C. C. J. Organomet. Chem. 2010, 695, 680−686. (28) Ascenso, J. R.; de Azevedo, C. G.; Calhorda, M. J.; de C. T. Carrondo, M. A. A. F.; Costa, P.; Dias, A. R.; Drew, M. G. B.; Félix, V.; Galvão, A. M.; Romão, C. C. J. Organomet. Chem. 2001, 632, 197−208. (29) Javier de la Mata, F.; Giner, P.; Royo, P. J. Organomet. Chem. 1999, 572, 155−161.

ASSOCIATED CONTENT

S Supporting Information *

Crystallographic data for 5, 7, 8, 10, 11, and 14 and tables giving atomic coordinates for all optimized species. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +420-46603 7068. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by Czech Science Foundation (Project No. GACR/203/09/P100) and Ministry of Education of the Czech Republic (Project No. MSM0021627501).

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REFERENCES

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Effect of the Substitution on the Protonation of Allyl Cyclopentadienyl

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