Phosphinoferrocenyl carboxamides bearing glycine pendant groups: Synthesis, palladium(II) complexes, and catalytic use in polar and aqueous reaction media

DOI: 10.1021/om900209j

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Organometallics p. 3288 - 3302 (2009)

Update date:2022-08-02

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Authors:

Tauchman, Jiri

Cisarova, Ivana

Stepnicka, Petr

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Article abstract of DOI:10.1021/om900209j

The reaction of 1'-(diphenylphosphino)-1-ferrocenecarboxylic acid (Hdpf) with H₂NCH₂CO₂CR₃ mediated by peptide coupling agents (EDC/HOBt) afforded novel glycine phosphino-carboxamides Ph₂PfcCONHCH View More

Full text of DOI:10.1021/om900209j

3288

Organometallics 2009, 28, 3288–3302

Phosphinoferrocenyl Carboxamides Bearing Glycine Pendant

Groups: Synthesis, Palladium(II) Complexes, and Catalytic Use in

Polar and Aqueous Reaction Media

Jirˇ´ı Tauchman, Ivana C´ısarˇova´, and Petr Steˇpnicˇka*

Department of Inorganic Chemistry, Faculty of Science, Charles UniVersity in Prague,

HlaVoVa 2030, 128 40 Prague, Czech Republic

ReceiVed March 19, 2009

The reaction of 1′-(diphenylphosphino)-1-ferrocenecarboxylic acid (Hdpf) with H₂NCH₂CO₂CR₃

mediated by peptide coupling agents (EDC/HOBt) afforded novel glycine phosphino-carboxamides

Ph₂PfcCONHCH₂CO₂CR₃(fc ) ferrocene-1,1′-diyl; R ) H (1) and Me (2*)). Compound 1 was converted

to its corresponding phosphine oxide (3*) and sulﬁde (4*), to N-acyl glycine Ph₂PfcCONHCH₂CO₂H

(5), and to bis-amide Ph₂PfcCONHCH₂CONH₂(6*). Compounds 1 and 6 reacted with [PdCl₂(cod)] (cod

) η²:η²-cycloocta-1,5-diene) and 5 reacted with Na₂[PdCl₄] to afford the respective, mostly solvated

bis-phosphine complexes trans-[PdCl₂(L-κP)₂] (7: L ) 1; 8: L ) 5, 9: L ) 6). Two different solvatomorphs

of 9 were isolated in crystalline form and structurally characterized (9* and 9a*). Furthermore, bridge

cleavage reaction of [{Pd(µ-Cl)(L^NC)}₂] (L^NC) 2-[(dimethylamino-κN)methyl]phenyl-κC¹) with 1 gave

[(L^NC)Pd(Cl)(1-κP)] (10*), which was further reacted with AgClO₄or KOt-Bu to afford bis-chelate

complexes [(L^NC)Pd(1-κ²O,P)]ClO₄(11*) and [(L^NC)Pd(L-κ²N,P)] (12*; L ) 1 deprotonated at the NH

group), respectively. All compounds were characterized by spectroscopic methods (multinuclear NMR,

MS, and IR) and by elemental analyses; the asterisk indicates that the crystal structure has been determined.

Compounds 1, 3-6, and 10-12 were studied by electrochemical methods, while phosphines 1, 5, and 6

in combination with palladium(II) acetate were shown to be highly active catalysts for the Suzuki-Miyaura

cross-coupling of aryl bromides with phenylboronic acid in polar solvents (ethanol and dioxane), in their

aqueous mixtures, and in pure water.

demonstrated to be valuable synthetic building blocks⁸and

Introduction

ﬂexible ligands for coordination chemistry and catalysis.^6,7The

Conjugation of ferrocenecarboxylic acids with amino acids

or peptides via amide bonds represents a convenient method

for introduction of the ferrocene moiety into biomolecules. A

vast number of such conjugates have been prepared from

ferrocenecarboxylic and 1,1′-ferrocenedicarboxylic acids mainly

for redox labeling or structural studies,¹while only little has

been done with ferrocenecarboxylic acids possessing additional

functional groups.²While studying the chemistry of 1′-(diphe-

nylphosphino)-1-ferrocenecarboxylic acid (Hdpf)³and the re-

lated acids,^4,5we found that they can be readily converted to

simple and N-functionalized phosphine-carboxamides.^6,7The

possibility of changing the substituents at the amide nitrogen

part makes these compounds highly versatile. So far, they were

latter application ﬁelds can particularly beneﬁt from ﬁne-tuning

of the ligand properties by means of substituents in the amide

(5) Recent examples: (a) Lamacˇ, M.; C´ısaˇrova´, I.; Steˇpnicˇka, P. New

J. Chem. 2009, 33, doi: 10.1039/b901262a. (b) Lamacˇ, M.; Cvacˇka, J.;

Steˇpnicˇka, P. J. Organomet. Chem. 2008, 693, 3430. (c) Bianchini, C.; Meli,

A.; Oberhauser, W.; Segarra, A. M.; Passaglia, E.; Lamacˇ, M.; Steˇpnicˇka,

P. Eur. J. Inorg. Chem. 2008, 441. (d) Ku¨hnert, J.; Lamacˇ, M.; Ru¨ffer, T.;

Walfort, B.; Steˇpnicˇka, P.; Lang, H. J. Organomet. Chem. 2007, 692, 4303.

(e) Lamacˇ, M.; C´ısaˇrova´, I.; Steˇpnicˇka, P. Collect. Czech. Chem. Commun.

2007, 72, 985. (f) Lamacˇ, M.; C´ısaˇrova´, I.; Steˇpnicˇka, P. Eur. J. Inorg.

Chem. 2007, 2274. (g) Steˇpnicˇka, P.; C´ısaˇrova´, I. Collect. Czech. Chem.

Commun. 2006, 71, 279. (h) Lamacˇ, M.; C´ısaˇrova´, I.; Steˇpnicˇka, P. J.

Organomet. Chem. 2005, 690, 4285. (i) Trzeciak, A. M.; Steˇpnicˇka, P.;

Mieczyn˜ska, E.; Zio´lkowski, J. J. Organomet. Chem. 2005, 690, 3260.

(6) (a) Schulz, J.; C´ısaˇrova´, I.; Steˇpnicˇka, P. J. Organomet. Chem. 2009,

694, doi: 10.1016/j.jorganchem.2009.04.007. (b) Ku¨hnert, J.; C´ısarˇova´, I.;

Lamacˇ, M.; Steˇpnicˇka, P. Dalton Trans. 2008, 2454. (c) Ku¨hnert, J.; Lamacˇ,

* Corresponding author. E-mail: stepnic@natur.cuni.cz.

M.; Demel, J.; Nicolai, A.; Lang, H.; Steˇpnicˇka, P. J. Mol. Catal. A: Chem.

(1) Selected reviews: (a) Metzler-Nolte, N.; Salmain, M. The Bioorga-

nometallic Chemistry of Ferrocene in Ferrocenes: Ligands, Materials and

2008, 285, 41. (d) Lamacˇ, M.; Tauchman, J.; C´ısaˇrova´, I.; Steˇpnicˇka, P.

Organometallics 2007, 26, 5042. (e) Ku¨hnert, J.; Dusˇek, M.; Demel, J.;

Lang, H.; Steˇpnicˇka, P. Dalton Trans. 2007, 2802. (f) Steˇpnicˇka, P.; Schulz,

J.; C´ısaˇrova´, I.; Fejfarova´, K. Collect. Czech. Chem. Commun. 2007, 72,

453. See also refs 5a and 5f.

Biomolecules; Steˇpnicˇka, P., Ed.; Wiley: Chichester, 2008; Chapter 13, pp

499-639. (b) Heinze, K.; Beckmann, M.; Hempel, K. Chem.sEur. J. 2008,

14, 9468. (c) Moriuchi, T.; Hirao, T. Top. Organomet. Chem. 2006, 17,

143. (d) Kraatz, H.-B. J. Inorg. Organomet. Polym. Mater. 2005, 15, 83.

(e) van Staveren, D. R.; Metzler-Nolte, N. Chem. ReV. 2004, 104, 5931. (f)

Moriuchi, T.; Hirao, T. Chem. Soc. ReV. 2004, 33, 294.

(7) For further examples, see: (a) Zhang, W.; Shimanuki, T.; Kida, T.;

Nakatsuji, Y.; Ikeda, I. J. Org. Chem. 1999, 64, 6247. (b) Longmire, J. M.;

Wang, B.; Zhang, X. J. Am. Chem. Soc. 2002, 124, 13400. (c) You, S.-L.;

Hou, X.-L.; Dai, L.-X. J. Organomet. Chem. 2001, 637-639, 762. (d) You,

S.-L.; Hou, X.-L.; Dai, L.-X.; Zhu, X.-Z. Org. Lett. 2001, 3, 149. (e)

Longmire, J. M.; Wang, B.; Zhang, X. Tetrahedron Lett. 2000, 41, 5435.

(f) You, S.-L.; Hou, X.-L.; Dai, L.-X.; Cao, B.-X.; Sun, J. Chem. Commun.

2000, 1933.

(2) Several bis(peptidyl) derivatives of 1′-amino-1-ferrocenecarboxylic

acid were reported (refs 1a and 1b).

(3) Podlaha, J.; Steˇpnicˇka, P.; C´ısarˇova´, I.; Ludv´ık, J. Organometallics

1996, 15, 543.

(4) (a) Steˇpnicˇka, P. Eur. J. Inorg. Chem. 2005, 3787. (b) Steˇpnicˇka, P.

1′-Functionalised Ferrocene Phosphines: Synthesis, Coordination Chemistry

and Catalytic Applications in Ferrocenes: Ligands, Materials and Biomol-

(8) (a) Meca, L.; Dvorˇa´k, D.; Ludv´ık, J.; C´ısaˇrova´, I.; Steˇpnicˇka, P.

Organometallics 2004, 23, 2541. (b) Drahonˇovsky´, D.; C´ısaˇrova´, I.;

ecules; Steˇpnicˇka, P., Ed.; Wiley, Chichester, 2008; Chapter 5, pp 177-

Steˇpnicˇka, P.; Dvorˇa´kova´, H.; Malonˇ, P.; Dvorˇa´k, D. Collect. Czech. Chem.

204.

Commun. 2001, 66, 588.

10.1021/om900209j CCC: $40.75

2009 American Chemical Society

Publication on Web 05/13/2009

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3289

part. For instance, introduction of additional donor moieties was

shown to increase the range of accessible coordination modes

and may impart hemilabile coordination,⁹while polar groups

render the amidophosphines (and their complexes) more soluble

in polar solvents.^6a,10

This led us to design ferrocene phosphinocarboxamides

derived from amino acids that, to the best of our knowledge,

were not reported to date. Indeed, organic phosphine-substituted

amino acids are in no way unprecedented. Yet, they were

typically prepared by direct synthesis and manipulation of amino

acid side chains^11,12or, alternatively, by Mannich condensation

from amino acids, formaldehyde, and secondary phosphines (or

hydroxymethylphosphines) to give N-(phosphinomethyl) amino

acids.¹³By contrast, the straightforward approach making use

of amidation reactions with phosphinocarboxylic acids remains

still less explored¹⁴despite holding considerable synthetic

potential, mainly for the preparation of multidentate ligands with

great structural and coordination variability that can be advan-

tageously applied in coordination chemistry and catalysis.

With this contribution, we report the preparation and structural

characterization of the ﬁrst phosphinoferrocene-carboxamides

with glycine-based pendant groups (Gly-OH, Gly-OR, Gly-NH₂)

obtained by “conjugation” of Hdpf with glycine esters (Gly-

OR) and subsequent transformations at the phosphinoferrocenyl

group and in the glycine moiety. Also reported are the

preparation and crystal structures of several palladium(II)

complexes with these hybrid donors, electrochemical charac-

terization of the compounds, and the results of their catalytic

testing in Suzuki-Miyaura cross-coupling reaction.

Results and Discussion

Synthesis of Glycine-amides. Conjugates of ferrocenecar-

boxylic acids with amino acids or peptides are typically prepared

by the direct reaction mediated by peptide coupling agents.¹

Because of high yields and mild reaction conditions, this method

was employed also for the preparation of Hdpf-glycine amides.¹⁵

Thus, compounds 1 and 2 were synthesized by the coupling of

respective glycine esters, H-Gly-OMe and H-Gly-Ot-Bu (gener-

ated in situ from their hydrochlorides and triethylamine), to Hdpf

in the presence of 1-hydroxybenzotriazole and N-[3-(dimeth-

ylamino)propyl]-N′-ethylcarbodiimide (Scheme 1). The amides

were puriﬁed by column chromatography and isolated as air-

stable orange solids in excellent yields and were characterized

by conventional spectral methods and by combustion analysis.

The crystal structure of 2 was determined by single-crystal X-ray

diffraction.

(9) (a) Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40, 680.

(b) Slone, C. S.; Weinberger, D. A.; Mirkin, C. A. Prog. Inorg. Chem.

1999, 48, 233. (c) Bader, A.; Lindner, E. Coord. Chem. ReV. 1991, 108,

27.

(10) (a) Aqueous-Phase Organometallic Catalysis, 2nd ed.; Cornils, B.,

Herrmann, W. A., Eds.; Wiley-VCH: Weinheim, 2004. (b) Joo´, F. Aqueous

Organometallic Catalysis; Kluwer: New York, 2002.

(11) Selected examples: (a) Meyer, C.; Scherer, M.; Scho¨nberg, H.;

Ru¨egger, H.; Loss, S.; Gramlich, V.; Gru¨tzmacher, H. Dalton Trans. 2006,

137. (b) Heinicke, J.; Peulecke, N.; Jones, P. G. Chem. Commun. 2005,

262. (c) Agarkov, A.; Greenﬁeld, S.; Xe, D.; Pawlick, R.; Starkey, G.;

Gilbertson, S. R. Biopolymers 2005, 84, 48. (d) Iyengar, V.; Galka, P. V.;

Pletsch, A.; Kraatz, H.-B. Can. J. Chem. 2002, 80, 1562. (e) Greenﬁeld,

S. J.; Gilbertson, S. R. Synthesis 2001, 2337. (f) Brauer, D. J.; Kottsieper,

K. W.; Schenk, S.; Stelzer, O. Z. Anorg. Allg. Chem. 2001, 627, 1151. (g)

Kratz, H.-B.; Pletsch, A. Tetrahedron: Asymmetry 2000, 11, 1617. (h)

Gilbertson, S. R.; Collibee, S. E.; Agarkov, A. J. Am. Chem. Soc. 2000,

122, 6522. (i) Brauer, D. J.; Schenk, S.; Rossenbach, S.; Tepper, M.; Stelzer,

O.; Ha¨usler, T.; Sheldrick, W. S. J. Organomet. Chem. 2000, 598, 116. (j)

Gilbertson, S. R.; Chang, C.-W. T. J. Org. Chem. 1998, 63, 8424. (k) Porte,

A. M.; van der Donk, W. A.; Burgess, K. J. Org. Chem. 1998, 63, 5262.

(l) Tepper, M.; Stelzer, O.; Ha¨usler, T.; Sheldrick, W. S. Tetrahedron Lett.

1997, 38, 2257. (m) Gilbertson, S. R.; Chang, C.-W. T. Chem. Commun.

1997, 975. (n) Gilbertson, S. R.; Pawlick, R. V. Angew. Chem., Int. Ed.

Engl. 1996, 35, 902. (o) Gilbertson, S. R.; Wang, X. J. Org. Chem. 1996,

61, 434. (p) Gilbertson, S. R.; Starkey, G. W. J. Org. Chem. 1996, 61,

2922. (q) Gilbertson, S. R.; Chen, G.; McLoughlin, M. J. Am. Chem. Soc.

1994, 114, 4481.

³¹P{¹H} NMR resonances of 1 and 2 are found at positions

similar to free Hdpf,³while the glycine CH₂groups are observed

as NH-coupled doublets at δ_Hca. 4.0 in H NMR and singlets

at δ_C41-42 in ¹³C{¹H} NMR spectra. The NMR spectra further

comprise characteristic signals due to the phosphinoferrocene

moiety and a pair of CdO resonances at δ_Cca. 170. The

presence of the ester and amide groups is further manifested

by their diagnostic bands in IR spectra. Compounds 1 and 2

are thermally robust, showing abundant molecular ions in

electron-impact mass spectra. Their fragmentation pathways are

similar, involving the elimination of OCR₃and CH₂CO₂CR₃

radicals (R ) H and Me) and disintegration of the phosphino-

ferrocene unit.¹⁶

(12) For the preparation of N-phosphino amino acids esters, see: Slawin,

A. M. Z.; Woolins, D. J.; Zhang, Q. J. Chem. Soc., Dalton Trans. 2001,

621.

(13) Selected examples: (a) Servin, P.; Laurent, R.; Romerosa, A.;

Peruzzini, M.; Majoral, J.-P.; Caminade, A.-M. Organometallics 2008, 27,

2066. (b) Smolen´ski, P.; Pruchnik, F. P. Pol. J. Chem. 2007, 81, 1771. (c)

Zhang, J.; Vittal, J. J.; Henderson, W.; Wheaton, J. R.; Hall, I. H.; Hor,

T. S. A.; Yan, Y. K. J. Organomet. Chem. 2002, 650, 123. (d) Karasik,

A. A.; Georgiev, I. O.; Musina, E. I.; Sinyashin, O. G.; Heinicke, J.

Polyhedron 2001, 20, 3321. (e) Berning, D. E.; Katti, K. V.; Barnes, C. L.;

Volkerts, W. A. J. Am. Chem. Soc. 1999, 121, 1658. (f) Kellner, K.; Hanke,

W. J. Organomet. Chem. 1987, 326, C9. (g) Kellner, K.; Hanke, W.;

Tzschach, A. Z. Chem. 1984, 24, 193. (h) Kellner, K.; Tzschach, A.; Nagy-

Magos, Z.; Marko, L. J. Organomet. Chem. 1980, 193, 307. (i) Kosty-

anovskii, R. G.; El’natanov, Yu, I.; Shikhaliev, Sh. M. IzV. Akad. Nauk.

SSSR, Ser. Khim. 1978, 972.

(14) (a) Caprioara, M.; Fiammengo, R.; Engeser, M.; Ja¨schke, A.

Chem.sEur. J. 2007, 13, 2089 (phosphino-acyl amino acids and DNA).

(b) Kobayashi, Y.; Tanaka, D.; Danjo, H.; Uozumi, Y. AdV. Synth. Catal.

2006, 348, 1561 (supported phosphine-acyl amino acid ligands). (c)

Riondato, M.; Camporese, D.; Mart´ın, D.; Suades, J.; Alvarez-Larena, A.;

Mazzi, U. Eur. J. Inorg. Chem. 2005, 4048 (phosphine-acyl glycine for

radiopharmaceutical applications). (d) Breit, B.; Laungani, A. C. Tetrahe-

dron: Asymmetry 2003, 14, 3823 (phosphino-acyl peptides). (e) Hird, A. W.;

Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42, 1276. (f) Lam, H.; Cheng,

X.; Steed, J. W.; Aldous, D. J.; Hii, K. K. Tetrahedron Lett. 2002, 43,

5875 (chiral proline amidophosphines). (g) Gilbertson, S. R.; Chang, C.-

W. T. J. Org. Chem. 1998, 63, 8424 (preparation of chiral oxazoline ligands).

(h) Joo´, F.; Tro´csa´nyi, E. J. Organomet. Chem. 1982, 231, 63 (Rh-catalyzed

asymmetric hydrogenation with phosphinoacyl amino acid ligands). (i)

Frolovskii, V. A.; Studnyev, Yu, N.; Rozancev, G. G. Zh. Obshch. Khim.

1993, 63, 1673 (condensation of Ph₂P(O)CH₂CO₂Et with amino acids esters).

See also ref 11a.

Compound 1 was subsequently modiﬁed at the phosphine

moiety and in the pendant glycine substituent (Scheme 1).

Oxidation with hydrogen peroxide or with sulfur produced the

corresponding phosphine oxide (3) and sulﬁde (4) in practically

quantitative yields after crystallization or chromatography,

respectively. Hydrolysis of 1 with NaOH in dioxane/water

followed by acidiﬁcation also proceeded cleanly to afford N-acyl

glycine 5. Isolation by column chromatography provided the

acid in a very good yield and reasonable purity. Exhaustive

puriﬁcation of 5 proved difﬁcult, as the acid is notoriously

contaminated with traces of its corresponding phosphine oxide,

which coelutes during the chromatography and cannot be

removed by crystallization (N.B. Acid 5 is reluctant to crystal-

lize). Finally, treatment of a methanolic solution of 1 with liquid

ammonia gave bis-amide 6, which was isolated in 88% yield

after chromatography and crystallization. Compounds 3-6 were

(15) For examples concerning amidation of ferrocene phosphinocar-

boxylic acids, see refs 6 and 8.

(16) Pola´sˇek, M.; Steˇpnicˇka, P. J. Mass Spectrom. 1998, 33, 739, and

references therein.

3290 Organometallics, Vol. 28, No. 11, 2009

Scheme 1. Synthesis of 1-6^a

Tauchman et al.

Figure 1. (a) View of the molecular structure of 2 showing

displacement ellipsoids at the 30% probability level and the atom-

labeling scheme. (b) Depiction of intermolecular H-bond interac-

tions in the structure of 2. Only pivotal atoms from the phenyl rings

are shown for clarity. Symmetry operations: A ) (x, y, z), B ) (x,

1/2-y, -1/2+z), C ) (x, 1/2-y, 1/2+z).

HOBt ) 1-hydroxybenzotriazole, EDC ) N-[3-(dimethylamino)-

propyl]-N′-ethylcarbodiimide.

characterized similarly to their parent amide 1, and the solid-

state structures of 3, 4, and 6 were established by X-ray

crystallography.

1). Additional differences can be seen in the conformation at

the N-C(24) bond and, particularly, in the mutual orientation

of the ferrocene substituents (Table 1). The substituents in 2

assume a conformation close to anti-eclipsed (ideal value τ )

144°), whereas those in 3 and 4 are near to syn-eclipsed (ideal

value 72°). This is apparently due to the formation of intramo-

lecular N-H · · · E hydrogen bonds in the chalcogenides (E )

O for 3 and S for 4; Table 2), the longer E · · · N distance in 4

corresponding with the higher τ and lower ꢀ angles. Apart from

this interaction, the molecules of 3 and 4 generate similar sets

of soft intra- and intermolecular C-H · · · E contacts in their

crystals (Table 2) that, when taken together, lead to the

formation of centrosymmetric dimer units and their columnar

propagation (Figure 2b).

The ferrocene moiety in 6 adopts a conformation near to syn-

eclipsed (i.e., similar to 4), but the C(11)-N-C(24)-C(25)

angle is more opened. Such changes are in accordance with

intermolecular aggregation, which is more complex than in 2-4

owing to a higher number of available H-bond donors.

Individual molecules of 6 assemble to centrosymmetric dimers

via N(2)-H(3N) · · · O(1) hydrogen bonds. These dimers further

associate through N-H · · · O interactions, forming layers parallel

to the crystallographic bc plane (Figure 5, Table 2). Softer

C-H · · · O contacts support the formed assembly.

Modiﬁcations of the phosphorus substituent (1 f 3 and 4)

are clearly reﬂected in the ³¹P NMR spectra through a shift to

lower ﬁelds (δ_P) 32.1 for 3 and 42.9 for 4). The position of

the ³¹P signals as well as the H and ¹³C NMR parameters of

the Ph₂P(E)-substituted ferrocenyl groups (E ) O and S) match

those of the respective Hdpf derivatives,^3,6fwhereas the NMR

response of glycine pendant group in 3 and 4 remain largely

unaffected. On the other hand, modiﬁcations at the glycine

moiety such as in 5 and 6 have quite opposite (though not

dramatic) effect. The carboxyl ν_CdOband in the IR spectrum

of 5 is shifted to lower energies than for 1, while the amide

bands appear moved in the opposite direction. The IR spectra

of 6 and 1 differ expectedly more because of the change at the

polar functional moiety (CO₂Me f C(O)NH₂).

Crystal Structures of 2-4 and 6. The molecular structures

of 2, 3, 4, and 6 are shown in Figures 1-4. Relevant geometric

data are given in Table 1. The overall molecular geometries

compare favorably with those of Hdpf,³its P-chalcogen

derivatives,^3,6fand the related ferrocenecarboxylic derivatives:

FcCONHCH₂CO₂R (R ) Me and CH₂Ph;¹⁷Fc ) ferrocenyl)

and fc(CONHCH₂CONH₂)₂· 2H₂O (fc ) ferrocene-1,1′-diyl).¹⁸

The ferrocene units in 2-4 and 6 are regular, showing

negligible tilts and similar Fe-ring centroid distances. The

secondary amide moieties are planar but tilted with respect to

their parent cyclopentadienyl (Cp) rings (see ꢀ angles in Table

Preparation and Structural Characterization of Bis-phos-

phine Complexes 7-9. Reactions of [PdCl₂(cod)] (cod ) η²:

η²-cycloocta-1,5-diene) with 1 and 6 and the reaction of

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3291

Figure 4. Molecular structure of diamide 6. Displacement ellipsoids

correspond to the 30% probability level.

Table 1. Selected Distances and Angles for 2-4 and 6 (in Å and

deg)^a

parameter

void

O(4)

void

Fe-Cg(1)

1.6521(7) 1.6385(8) 1.6480(7) 1.645(1)

1.6489(7) 1.6451(7) 1.6536(7) 1.648(1)

Fe-Cg(2)

Cp(1),Cp(2)

0.33(9)

133

2.14(9)

1.96(9)

2.1(2)

τ^b

PdE

1.494(1)

1.225(2)

1.348(2)

1.438(2)

1.193(2)

1.342(2)

1.446(2)

26.7(2)

122.5(1)

118.7(1)

124.5(1)

115.4(1)

7.9(2)

1.9601(4)

1.230(2)

1.351(2)

1.443(2)

1.196(2)

1.340(2)

1.452(3)

14.9(2)

122.5(1)

120.2(1)

124.0(2)

115.9(2)

4.9(2)

C(11)-O(1)

1.235(2)

1.349(2)

1.445(2)

1.202(2)

1.339(2)

1.492(2)

26.1(2)

121.8(1)

121.5(1)

126.1(1)

121.4(1)

1.229(3)

1.353(3)^d

1.450(3)^d

1.243(3)

1.321(3)^e

C(11)-N

N-C(24)

C(25)-O(2)

C(25)-O(3)

O(3)-C(26)

ꢀ^c

13.6(3)

O(1)-C(11)-N

C(11)-N-C(24)

O(2)-C(25)-O(3)

C(25)-O(3)-C(26)

O(1)-C(11)-N-C(24) 5.6(2)

C(11)-N-C(24)-C(25) 92.9(2)

122.1(2)^d

119.7(2)^d

122.6(2)^f

Figure 2. (a) Molecular structure of 3. Displacement ellipsoids

correspond to 30% probability. (b) View of the dimeric motif in

the crystal of 3 showing hydrogen bonds as dotted lines. Phenyl

ring carbon atoms are omitted for clarity. Molecules A and B relate

by a crystallographic inversion operation.

4.4(3)^d

65.2(2)

87.2(2)

126.9(2)^d

^aThe ring planes are deﬁned as follows: Cp(1) ) C(1-5), Cp(2) )

C(6-10). Cg(1) and Cg(2) denote the respective ring centroids.

^bTorsion angle C(1)-Cg(1)-Cg(2)-C(6). ^cDihedral angle of the Cp(2)

and {C(11), O(1), N} ({C(11), O(1), N(1)} for 6) planes. ^dParameter

involving N(1). ^eC(25)-N(2). ^fO(2)-C(25)-N(2).

stoichiometric solvates with three water and four acetic acid

molecules per the complex molecule, respectively. Yet another

solvate, trans-[PdCl₂(6-κP)₂] · 4CHCl₃(9a), was obtained upon

crystallization of 9 from chloroform/hexanes.

Complexes 7-9 were characterized by elemental analysis and

by NMR, IR, and ESI mass spectra; a negligible solubility of 8

precluded any NMR analysis.¹⁹¹H and ³¹P NMR data of 7 and

9 indicate that the ferrocene ligands are chemically equivalent

and coordinate as monodentate phosphines, the ³¹P NMR data

comparing well with those of trans-[PdCl₂(Hdpf-κP)₂].²⁰The

P-monodentate coordination was corroborated by IR spectra,

showing the amide bands at positions similar to the free ligands.

In addition, the ¹³C NMR spectra exhibited signals due to the

(17) (a) Gallagher, J. F.; Kenny, P. T. M.; Sheehy, M. J. Inorg. Chem.

Commun. 1999, 2, 200. (b) Gallagher, J. F.; Kenny, P. T. M.; Sheehy, M. J.

Acta Crystallogr, Sect. C, Cryst. Struct. Commun. 1999, 55, 1257.

(18) Georgopoulou, A. S.; Mingos, D. M. P.; White, A. J. P.; Williams,

D. J.; Horrocks, B. R.; Houlton, A. J. Chem. Soc., Dalton Trans. 2000,

2969.

Figure 3. Molecular structure of 4. Displacement ellipsoids are

drawn at the 30% probability level.

Na₂[PdCl₄] with 5 proceed straightforwardly to yield bis-

phosphine complexes 7-9 (Scheme 2). Complex 7 was isolated

solvent-free, while its more polar analogues 8 and 9 resulted as

(19) Complex 8 is virtually insoluble in all common laboratory solvents

except for warm dimethylsulfoxide, in which, however, it rapidly decomposes.

3292 Organometallics, Vol. 28, No. 11, 2009

Tauchman et al.

Table 2. Hydrogen Bond Parameters for the Structures of 2-4 and 6^a

D-H · · · A

D · · · A (Å)

Compound 2

D-H · · · A (deg)

N(1)-H(1N) · · · O(1ⁱ)

C(7)-H(7) · · · O(1ⁱ)

C(3)-H(3) · · · O(2) (I)

2.953(2)

3.058(2)

3.365(2)

171(2)

135

163

Compound 3

N(1)-H(1N) · · · O(4) (I)

C(5)-H(5) · · · O(2) (I)

C(4)-H(4) · · · O(1ⁱⁱ)

2.858(2)

3.413(2)

3.322(2)

3.114(2)

172(2)

158

150

C(26)-H(26C) · · · O(1ⁱⁱⁱ)

126

Compound 4

N(1)-H(1N) · · · S (I)

C(2)-H(2) · · · O(2) (I)

C(16)-H(16) · · · O(1^iv)

C(20)-H(20) · · · O(1^v)

3.659(1)

3.456(2)

3.477(2)

3.337(2)

176

160

155

Compound 6

N(1)-H(1N) · · · O(2^vi)

N(2)-H(2N) · · · O(2^vii)

3.149(2)

2.877(3)

2.846(3)

3.315(3)

3.281(3)

175

166

137

147

N(2)-H(3N) · · · O(1^viii

)

Figure 6. View of the complex molecule in the crystals of 9.

Displacement ellipsoids enclose 30% probability. Primed atoms are

generated by the crystallographic inversion.

C(10)-H(10) · · · O(2^vi)

C(24)-H(24A) · · · O(1^viii

)

^aLegend: D ) donor, A ) acceptor, (I) ) intramolecular contact.

Symmetry codes: i (x, 1/2-y, -1/2+z), ii (1-x, -1-y, 1-z), iii (1-x,

1/2+y, 3/2-z), iv (1-x, 1-y, 1-z), v (x, 3/2-y, -1/2+z), vi (1-x,

1/2+y, 1/2-z), vii (1-x, -1/2+y, 1/2-z), viii (1-x, -y, 1-z).

Table 3. Comparison of the Selected Structural Data for 9 and 9a

(values in Å and deg)^a

parameter

Pd-Cl

Pd-P

2.2955(9)

2.3374(8)

93.67(3)

1.645(2)

1.647(2)

3.5(2)

2.283(1)

2.3522(9)

90.40(4)

1.641(2)

1.640(2)

1.3(3)

Cl-Pd-P^b

Fe-Cg(1)

Fe-Cg(2)

Cp(1),Cp(2)

C(11)-O(1)

C(11)-N(1)

O(1)-C(11)-N(1)

C(25)-O(2)

C(25)-N(2)

O(2)-C(25)-N(2)

τ^c

1.239(5)

1.339(5)

120.8(3)

1.240(4)

1.318(5)

124.0(4)

138

6.8(4)

2.4(5)

88.6(4)

1.239(5)

1.338(5)

121.6(4)

1.226(6)

1.324(6)

123.3(4)

151

14.8(5)

4.5(6)

83.9(5)

ꢀ^d

O(1)-C(11)-N(1)-C(24)

C(11)-N(1)-C(24)-C(25)

Figure 5. Section of the solid-state molecular assembly of 6

showing hydrogen bonds as dashed lines. Phenyl ring carbons and

CH hydrogens are omitted to avoid complicating the ﬁgure.

^aThe ring planes are deﬁned as follows: Cp(1) ) C(1-5), Cp(2) )

C(6-10). Cg(1) and Cg(2) denote the respective ring centroids. ^bThe

Cl-Pd-P and Cl-Pd-P′ angles sum up to 180° due to molecular

symmetry. ^cTorsion angle C(1)-Cg(1)-Cg(2)-C(6). ^dDihedral angle

of the Cp(2) and {C(11), O(1), N(1)} least-squares planes.

Scheme 2. Synthesis of Bis-phosphine Complexes 7-9

previously noted for the related complexes trans-[PdCl₂(Ph₂PfcY-

κP)₂] (Y ) CO₂H,²⁰CHdCH₂,²²and PO₃Et₂²³).

Crystal structures of 9 and 9a have been determined in order

to establish the inﬂuence of the solvent of crystallization on

the crystal assembly. The molecular structure of 9 is shown in

Figure 6 (for structural drawings of 9 and 9a, see Supporting

Information, Figure S1). Geometric data for 9 and 9a are

presented in Table 3.

Both solvatomorphs crystallize with the symmetry of the P1

space group, with the Pd atoms residing on crystallographic

inversion centers. This renders only half of their molecules

structurally independent and makes the coordination environ-

ment around palladium perfectly planar. Owing to the imposed

symmetry, the “PC₃” moieties are staggered and the ferrocene

ligands assume anti positions. Whereas the Pd-Cl/P distances

and Cl-Pd-P/P′ angles in 9 are almost identical with those

found for trans-[PdCl₂(Hdpf-κP)₂] · 2AcOH,²⁰the parameters

phosphinylated Cp and phenyl ring carbons (CH and C_ipso

except for phenyl CH_para) as apparent triplets. Such behavior is

typical for ABX spin systems ¹²C-³¹P(A)-M-³¹P(B)-¹³C(X)

(M ) metal)²¹arising in bis-phosphine complexes and was

(20) Steˇpnicˇka, P.; Podlaha, J.; Gyepes, R.; Pola´sˇek, M. J. Organomet.

Chem. 1998, 552, 293.

(21) Pregosin, P. S.; Kunz, R. W. ³¹P and ¹³C NMR of Transition Metal

Phosphane Complexes in NMR Basic Principles and Progress; Diehl, P.,

Fluck, E., Kosfeld, R., Eds.; Vol. 16, Chapter E, pp 65ff, and references

therein.

(22) Steˇpnicˇka, P.; C´ısaˇrova´, I. Collect. Czech. Chem. Commun. 2006,

71, 215.

(23) Steˇpnicˇka, P.; C´ısaˇrova´, I.; Gyepes, R. Eur. J. Inorg. Chem. 2006,

926.

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3293

Figure 8. Section of the H-bonded array in the crystal of 9a showing

hydrogen bonds as dashed lines. For clarity, phenyl ring carbons,

irrelevant hydrogens, and solvating molecules are omitted. Propaga-

tion of the assembly is indicated with small (via H-bonds) and larger

(via PdCl₂moieties) arrows. H-bond parameters are given as for 9

(see caption to Figure 7). Molecules A and B (C and D) relate by

crystallographic inversion; molecules C and D result by translation

of A and B along the a axis.

Figure 7. Section of the H-bonded array in solid 9. Hydrogen bonds

are shown as dashed lines, and the hydrogen-bonded cage is

highlighted with a dotted circle. Propagation of the supramolecular

assembly is indicated with small (via H-bonds) and larger (via

PdCl₂) arrows. For clarity, phenyl ring carbons, irrelevant hydro-

gens, and PdCl₂units are omitted. Data for H-bonds are given as

follows: D-H · · · A, D · · · A (Å)/D-H · · · A angle (deg) (D ) donor,

A ) acceptor). Molecules A and B (C and D) relate by crystal-

lographic inversion; the C-D pair results by translation of A-B

along the b axis.

cooperative N-H · · · O/Cl and C-H · · · O interactions (Figure

8).²⁵Further propagation of the molecular assembly again occurs

via the PdCl₂moiety, giving rise to sheets in the crystallographic

ac plane. Unlike 9, however, these sheets are not interconnected

but instead deﬁne structural voids that host the solvent of

crystallization.²⁶

of 9a slightly differ from 9 and the reference compound (N.B.

The interligand angles in 9a deviate from the ideal 90° only

negligibly). Another difference can be found in the mutual

orientation of the ferrocene ligands and the coordination plane,

the dihedral angles of the Cp(1) and {Pd,Cl,P} planes being

52.2(2)° and 36.1(2)° for 9 and 9a, respectively. Compared to

free 6, the ferrocene substituents in 9 and 9a are more distant,

assuming positions near anti-eclipsed (Figure S1). The Cp-bound

amide moiety {C(11),O(1),N(1)} in 9a is symmetrically rotated

around the C(6)-C(11) bond (ꢀ ≈ 15°). In 9 the amide plane

exerts a lower rotation but is tilted toward the ferrocene unit.²⁴

The conformation of the glycine pendants is changed as well,

reﬂecting hydrogen bond formation (Table 3).

As expected, the crystal architecture of both 9 and 9a is based

on hydrogen-bonding interactions. In the crystals of 9, the ligand

units and the solvent assemble into centrosymmetric cages by

means of N-H · · · O and O-H · · · O hydrogen bonds (Figure

7). These cages are interlinked via H-bonds generated by the

second acetic acid molecule, forming columnar stacks oriented

parallel to the crystallographic b axis. However, since each

complex molecule possesses two ligands, these stacks propagate

into inﬁnite layers through the PdCl₂fragments. Additional

intermolecular C-H · · · O and C-H · · · Cl contacts cross-link

the individual sheets.

Synthesis and Crystal Structures of (L^NC)Pd Complexes.

Three chemically different palladium(II) complexes with a

2-[(dimethylamino-κN)methyl]phenyl-κC¹(L^NC) auxiliary ligand,

compounds 10-12, have been prepared from ligand 1 (Scheme

3). First, a bridge cleavage reaction between dimer [{Pd(µ-

Cl)(L^NC)}₂] and 1 cleanly afforded complex 10 in 95% yield

after crystallization. Subsequent halide removal with AgClO₄

yielded cationic complex 11 (90% yield), in which the amide

oxygen takes up the free coordination site with concomitant

closure of a P,O-chelate ring. Another bis-chelate complex 12

resulted when 10 was treated with potassium tert-butoxide (59%

yield after crystallization). The conversion of 10 into 12 formally

consists of two steps: the removal of the amide proton with

t-BuO^-and the intramolecular displacement of the Pd-bound

chloride, converting the ferrocene ligand to an anionic P,N-

chelate donor. The reverse reaction also proved feasible,

complex 12 being smoothly converted back to 10 upon treatment

with 1 molar equiv of HCl.

Complexes 10-12 were characterized by spectral methods

and by elemental analysis, and their solid-state structures were

(25) The H-bond parameters are as follows: C(15)-H(15) · · · O(92):

C(15) · · · O(92) ) 3.272(5) Å, angle at H(15) ) 149°; C(20)-H(20) · · · Cl:

C(20) · · · Cl ) 3.673(4) Å; angle at H(20) ) 155°; C(24)-H(24A) · · · O(1):

C(24) · · · O(1) ) 3.384(5) Å, angle at H(24A) ) 144°.

(26) The solvate molecules form Cl₃C-H · · · O contacts to carbonyl

oxygens of the ligand. The H-bond parameters are as follows: C(80)-

H(80) · · · O(2): C(80) · · · O(2) ) 3.056(6) Å; angle at H(80) ) 163°; C(90)-

H(90) · · · O(1): C(90) · · · O(1) ) 3.111(7) Å; angle at H(90) ) 164°.

On the other hand, the ligands in 9a aggregate into ladder-

like arrays oriented along the crystallographic a axis via

(24) The distances from the Cp(2) plane for 9/9a are as follows: C(11)

0.109(4)/0.012(4), O(1) 0.034(3)/-0.275(3), and N(1) 0.268(3)/0.295(4) Å.

3294 Organometallics, Vol. 28, No. 11, 2009

Tauchman et al.

to higher energies, the frequency of the amide I band (ν_CdO

Scheme 3. Preparation and Reactions of (L^NC)Pd Complexes

with Ligand 1

)

decreases by ca. 30 cm^-1, while that of the amide II band

(largely NH bending) increases by 35 cm^-1. The ester ν_CdOband

also shifts to higher frequencies, albeit much less. Furthermore,

the IR spectrum of 11 also conﬁrms the presence of the

perchlorate counterion. The conversion of 10 to 12 is reﬂected

by a disappearance of the ν_NHband and a shift of the amide I

and ester ν_CdObands to lower energies (by ca. 60 and 20 cm^-1

vs 10, respectively).

Views of the molecular structures of 10-12 are presented in

Figure 9, and selected geometric data are given in Table 4.

Unlike 11, complexes 10 and 12 crystallize with two molecules

in the asymmetric unit. The structurally independent molecules

of 10 are very similar (see Supporting Information, Figure S2),

and their multiplication likely results from intermolecular

interactions.²⁸On the other hand, the molecules of 12 differ

substantially (Table 4, Figure S2), and the reasons for their

duplication in the asymmetric unit remain unclear.

Generally, the structural parameters of 10-12 compare well

with the data reported for (L^NC)Pd complexes featuring simple

and ferrocene-based phosphinocarboxylic ligands^27,29and con-

ﬁrm a trans P-N(metallacycle) relation as suggested from NMR

data. The coordination environment around the palladium atoms

in 10-12 departs signiﬁcantly from the regular square owing

to different Pd-donor bond lengths, steric constraints imposed

by the small palladacycle, and limitations resulting from spatial

contacts between the ligands.³⁰Whereas the Pd-P and Pd-C

bonds in 10-12 are of similar length, all other Pd-donor

distances differ noticeably, even among the structurally inde-

pendent molecules. Likewise, the N-Pd-C angle within the

rigid metallacycle varies only by ca. 1.5° (ring puckering

parameters conﬁrm structural similarity of the (L^NC)Pd units;³¹

Table 4), while all other interligand angles change signiﬁcantly

more.

established by single-crystal X-ray diffraction analysis. NMR

spectra of 10-12 reveal characteristic signal sets attributable

to L^NCand the ferrocene ligands. The NMR data correspond

with those reported for Pd(L^NC) complexes with phosphinocar-

boxylic donors²⁷and, via the ³J_PCand ⁴J_PCcoupling constants,

suggest a trans-P,N relationship²⁷in all cases. The ³¹P NMR

signals are found in a rather narrow range, δ_P30.9-33.6 (12 >

10 > 11), shifted downﬁeld versus free 1. The ¹H and ¹³C NMR

parameters of 10-12 are roughly similar (especially those

relating to molecular parts not involved in coordination). It

should be noted, however, that despite the planar chirality

resulting from ﬁxed conformation of the ferrocene unit in the

bis-chelate complexes, the resonances due to ferrocene CH

groups are observed as nondegenerate only for 12 (eight

diastereotopic signals). This may reﬂect a lower ﬂexibility of

the anionic (P,N^-) chelate over the neutral (P,O) one. Structural

data support this explanation.

Interatomic distances and angles within the ferrocene ligands

are similar to those of free ester-amide 2; notable differences

are seen in the conformation. The P-monodentate ligand in 10

has the sterically relaxed anti-eclipsed conformation, and its

carboxamide moiety is coplanar with its parent Cp(2) ring (ꢀ

≈ 2°). Formation of chelate rings in 11 and 12 requires

reorientation of the ferrocene substituents to a conformation

close to syn-eclipsed (τ: 12 < 11 < ideal value 72°) and,

simultaneously, leads to distortion of the carboxamide moiety.

As evidenced by the ꢀ angles, the amide planes in the chelate

complexes are no longer coplanar with their bonding Cp(2) plane

(ꢀ: 12 > 11 . 10) because the amide donor atoms are brought

to proximity of Pd via a combination of symmetric rotation

along the pivotal C(Cp)-C bond and twisting of the C(O)N

Conversion of 10 into 11 causes relatively small changes in

the NMR parameters. The most notable change is observed for

the amide CdO group, the C-13 resonance of which shifts from

ca. δ_C170-171 (in 10) to δ_C175.27. Deprotonation and

coordination of the amide nitrogen (10 f 12) has a more

pronounced effect: The H NMR signals due to glycine CH₂

protons in 12 become anisochronic (∆δ_H) 0.48), but their

average chemical shift (δ_H4.06) remains nearly the same as in

10 and 11. The C-13 signals due to the glycine moiety in 12

are shifted signiﬁcantly more (CH₂by +9.8 ppm and the amide

CdO by ca. +4 ppm vs 10). Finally, a resonance due to the

amide proton is expectedly missing from the ¹H NMR spectrum

of 12, and one of the ferrocene signals (R-CH at the amide-

substituted Cp ring) appears markedly downﬁeld compared to

the remaining ones (δ_H6.44 vs 4.09-4.91).

(28) The molecules of 10 form inﬁnite chains along the b direction via

N-H · · · Cl contacts between alternating, structurally independent moieties

1 and 2. The H-bond parameters are as follows (without symmetry codes):

N(11)-H(1N) · · · Cl(2): N(11) · · · Cl(2) ) 3.249(3) Å, angle at H(1N) )

155°; N(21)-H(2N) · · · Cl(1): N(21) · · · Cl(1) ) 3.194(3) Å, angle at H(2N)

) 150°. These chains are interconnected by C-H · · · O contacts.

Because complexes 10-12 differ predominantly at their polar

pendants, valuable structural information can be inferred from

their IR spectra. Upon converting 10 to 11, the ν_NHband moves

(29) Structural data for some related compounds can be found in: (a)

Steˇpnicˇka, P.; C´ısarˇova´, I. Inorg. Chem. 2006, 45, 8785. (b) Ma, J.-F.;

Yamamoto, Y. Inorg. Chim. Acta 2000, 299, 164. See also ref 22.

(30) The maximum deviations from the least-squares planes comprising

the palladium and its four ligating atoms are ca. 0.10/0.14 Å for 10 (molecule

1/2), ca. 0.19 Å for 11, and ca. 0.12/0.11 Å for 12 (molecule 1/2).

(31) Although any ring puckering analysis for the palladacycles can be

regarded as dubious due to very different in-ring bond lengths, the

parameters describe the same moiety and their trend is unambiguous. For

a reference, see: Cremer, D.; Pople, J. A. J. Am. Chem. Soc. 1975, 97,

1354.

(27) Ferrocene-based ligands: (a) Steˇpnicˇka, P.; Lamacˇ, M.; C´ısaˇrova´,

I. Polyhedron 2004, 23, 921. (b) Steˇpnicˇka, P. Inorg. Chem. Commun. 2004,

7, 426. (c) Steˇpnicˇka, P.; C´ısaˇrova´, I. Organometallics 2003, 22, 1728. See

also ref 5e. “Simple” phosphinocarboxylic ligands: (d) Braunstein, P.; Matt,

D.; Dusausoy, Y.; Fischer, J.; Mitschler, A.; Ricard, L. J. Am. Chem. Soc.

1981, 103, 5115. (e) Braunstein, P.; Matt, D.; Nobel, D.; Bouaoud, S.-E.;

Grandjean, D. J. Organomet. Chem. 1986, 301, 401.

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3295

Figure 9. Molecular structures of 10-12: (a) molecule 1 in the structure of 10, (b) cation in the structure of 11, and (c) molecule 1 in the

structure of 12. Displacement ellipsoids enclose 30% probability. Note: Atom labels in molecules 2 are obtained by changing the ﬁrst digit

in the respective label to 2 for heavy atoms (except for C) and by adding 40 (for 10) or 50 (for 12) for the carbon atom labels.

Table 4. Selected Distances and Angles for Complexes 10-12 (in Å and deg)^a

10 (E ) Cl)

12 (E ) N(11)/N(21))

parameter

molecule 1

molecule 2

11 (E ) O(1))

molecule 1

molecule 2

Pd-E

2.4123(9)

2.266(1)

2.144(3)

2.018(4)

90.86(3)

91.70(8)

97.0(1)

80.8(1)

0.498(3)

30.7(4)

1.648(2)

1.652(2)

3.0(2)

2.4120(9)

2.262(1)

2.161(3)

2.015(4)

90.94(3)

91.57(8)

97.1(1)

2.145(1)

2.2569(6)

2.145(2)

1.998(2)

98.43(4)

87.50(6)

92.92(6)

82.50(8)

0.429(2)

221.6(3)

1.644(1)

1.647(1)

6.5(1)

2.127(2)

2.2597(5)

2.188(2)

2.025(2)

96.30(5)

90.06(7)

93.19(6)

80.96(8)

0.508(2)

213.0(2)

1.640(1)

1.647(1)

6.9(1)

2.109(2)

2.2644(5)

2.166(2)

2.028(2)

88.34(5)

92.01(7)

98.57(6)

81.49(8)

0.427(2)

220.4(4)

1.642(1)

8.4(1)

Pd-P

Pd-N

Pd-C

E-Pd-P

E-Pd-N

P-Pd-C

N-Pd-C

81.2(1)

Q_ring

ꢀ_ring

0.452(3)

212.05(5)

1.648(2)

1.647(2)

2.9(2)

Fe-Cg(1)

Fe-Cg(2)

Cp(1),Cp(2)

τ^c

148

2.0(4)

149

2.3(4)

19.8(2)

24.5(3)

21.9(3)

ꢀ^d

CdO^e

1.228(5)

1.341(5)

122.5(4)

1.201(6)

1.309(6)

1.237(5)

1.353(5)

121.9(4)

1.195(6)

1.345(6)

1.252(2)

1.334(3)

119.3(2)

1.193(3)

1.330(3)

1.253(3)

1.341(3)

125.4(2)

1.197(3)

1.346(3)

1.252(3)

1.332(3)

123.6(2)

1.202(3)

1.341(3)

C-N^e

N-CdO^e

C(OMe)dO^f

(O)C-OMe^f

^aThe ring planes are deﬁned as follows: Cp(1) ) C(1-5), Cp(2) ) C(6-10). Cg(1) and Cg(2) stand for the respective ring centroids. Labeling of

“molecules 2” is strictly analogous (see comment in Figure 9). ^bRing puckering parameters: Q_ring) total puckering amplitude, ꢀ_ring) phase angle. Ideal

envelope requires ꢀ_ringto be equal to k × 36° (i.e., 36° or 216° in the present cases). See ref 31. ^cTorsion angle C(1)-Cg(1)-Cg(2)-C(6). ^dDihedral

angle of the Cp(2) and its bonded {C,O,N} plane. ^eParameters describing the Cp-bound amide moiety. ^fParameters involving the terminal

methoxycarboxyl group.

Table 5. Summary of Electrochemical Data^a

unit.³²Coordination of the amide moiety in either form (neutral

compound

wave I: E°′ [V]

further waves: E_pa/E_pc[V]

via O or deprotonated via N) brings on a slight elongation of

the CdO bond (ca. 0.02 Å) and an even less pronounced

shortening of the C-N bond (on average). The data in Table 4

indicate that the deformation of the ligand structure increases

from 10 to 11 and further to 12: ﬁrst markedly, owing to chelate

formation, and then less due to steric crowding when the glycine

pendant is forced closer to the coordination plane and to other

ligands.

0.26

0.43

0.40/0.31, 0.86/- (II)

n.o.

0.43

E_pa> 1.0 V (II)

0.85/- (II)

E_pa) 0.30

E_pa) 0.29

0.32

0.77/0.63 (II)

0.63/0.55, ca. 0.93 (E_pa, II)

n.o.

0.59

0.21

ca. 0.22, 0.48, 0.62 (all E_pa)

^aSee text for discussion. Recorded at platinum electrode in

dichloromethane solutions. The potentials are given relative to the

ferrocene/ferrocenium couple. For details, see Experimental Part. E°′ )

1/2(E_pa+ E_pc), where E_pa(E_pc) is the anodic (cathodic) peak potential in

CV. n.o. ) not observed.

Electrochemistry. Electrochemical behavior of Gly-amides

(1, 3-6) and of complexes 10-12 was studied by cyclic

voltammetry (CV) at a platinum disk electrode on dichlo-

romethane solutions. The pertinent data are summarized in

Table 5.^33,34

Ester-amide 1 undergoes an oxidation (wave I, Figure 10,

A), which is electrochemically quasi-reversible when scanned

separately (E°′ ) 0.26 V, ∆E_p) 90 mV at scan rate 100 mV

s^-1) and can be attributed to a ferrocene/ferrocenium couple.

Its shift toward more positive potentials versus ferrocene itself

(but negative of Hdpf: E°′ ) 0.32 V³) corresponds with the

nature of the substitutens (cf. σ_Pconstants:³⁵0.36 for CONH₂

(32) The distances of the C/O/N atoms forming the amide plane from

the Cp(2) plane are as follows (in Å): 10: 0.054(4)/0.093(3)/0.047(3) and

[0.021(4)/0.063(3)/0.027(3)] for molecule 1 [molecule 2]; 11: 0.241(2)/

0.665(1)/0.025(2); 12: 0.119(2)/0.278(2)/0.657(2) [0.271(2)/0.125(2)/

0.751(2)] for molecule 1 [molecule 2]. Directions of the displacement are

not indicated.

3296 Organometallics, Vol. 28, No. 11, 2009

Tauchman et al.

Figure 10. Cyclic voltammograms of 1 (in CH₂Cl₂at Pt electrode).

The partial voltammogram is started at +20 µA to avoid overlaps

(for B: full line ) ﬁrst scan, dashed line ) second scan).

Figure 11. Cyclic voltammograms of complex 10 (in CH₂Cl₂at a

Pt electrode, scan rate 100 mV s^-1).

reVersible ferrocene oxidation (wave I) at 0.32 V (∆E_p) 80

mV) for 10 and at 0.21 V (∆E_p) 85 mV) for 12. In the case

of 10, the observed anodic shift of wave I (vs 1) is in line with

electron density transfer upon coordination (ligand f Pd), which

renders any electron removal from the ferrocene unit more

difﬁcult. The opposite shift observed for 12 likely reﬂects the

anionic nature of the ferrocene ligand. When the CV scans on

10 and 12 are performed further beyond the ﬁrst wave (i.e.,

toward more positive potentials), the voltammograms change.

For 10, an additional minor redox couple develops (E°′ ) 0.59

V) on account of the ﬁrst wave (i_pa(I) ≈ i_pc(I) + i_pc(new wave))

and becomes better resolved during the second scan and after

scanning to higher potentials. Upon increasing the switching

potential even further, a minor irreversible oxidation emerges

(wave II; E_pa≈ 0.93 V). For 12, these additional oxidative peaks

are hardly discernible (no free CONH group is present in 12),

while two cathodic peaks at E_paca. +0.52 and +0.22 V can be

detected during back scanning, the latter convoluting with the

reduction counter-wave due to ﬁrst oxidation (wave I). In

contrast, the redox response of complex 11 is rather simple,

the compound showing a single reversible wave attributable to

ferrocene oxidation. The pronounced anodic shift of the fer-

rocene/ferrocenium wave (by 330 mV vs 1) can be accounted

for a synergy between 1-to-Pd donation and positive charge of

the complex species.

Catalytic Tests. Because of their polar nature, the phosphi-

noferrocene Gly-carboxamides could turn into potentially useful

ligands for catalysis in organic solvents. Replacement of

hazardous organic solvents for environmentally benign ones and

for water remains a challenging task, as it not only helps in

minimizing waste production and energy consumption during

product isolation but may also aid catalyst recovery and

recycling.^10,39The catalytic potential of the compounds under

study was assessed in palladium-catalyzed Suzuki-Miyaura

cross-coupling,⁴⁰using catalysts generated in situ from palla-

dium(II) acetate and phosphines 1, 5, 6, or Hdpf (1.2 equiv vs

Pd), and the model coupling of phenylboronic acid to 4-bro-

and 0.19 for PPh₂). When the switching potential is increased,

an additional follow-up peak emerges. The second oxidative

peak develops more at slower scan rates and after increasing

the switching potential. Upon back scanning, its corresponding

cathodic counter-peak is detected (E_pa/E_pc) 0.40/0.31 V).

Depending on the scan rate, the new wave convolutes with or

almost entirely replaces wave I (Figure 10, B). Finally, when

the scan range is extended even further, additional irreversible

oxidation is observed at E_pa) 0.86 V (wave II), attributable to

one-electron oxidation of the carboxamide moiety.³⁶It appears

likely that the initial oxidation at the ferrocene unit is followed

by chemical reactions giving rise to another redox-active species

(EC mechanism). Such behavior resulting from instability of

primary electrogenerated species is not uncommon among

ferrocene phosphines.^3,37

The electrochemical behavior of 5 and 6 is similar to that of

1. Thus, acid 5 undergoes one-electron oxidation at the ferrocene

unit (E_pa0.30 V, wave I), which is associated with chemical

complications that make it quasi-reversible. The following

oxidation of the amide moiety (wave II) is irreversible. Diamide

6 is also oxidized ﬁrst in a quasi-reversible step at E_pa0.29 V

(wave I), but the subsequent oxidation is observed as a broad

(probably composite due to oxidation of two amide groups)

wave at E_paca. 0.77 V and has a counter-peak at E_pc0.63 V

(wave II). Phosphine oxide 3 and sulﬁde 4, lacking a reactive

site (lone electron pair), undergo a reversible one-electron

removal³⁸at 0.43 V. Anodic shift of this ferrocene/ferrocenium

wave corresponds with an increased electron-withdrawing

character of the substituents (σ_P:³⁵0.53 for P(O)Ph₂and 0.47

for P(S)Ph₂).

Redox behavior of complexes 10 (Figure 11) and 12 parallels

that of 1 only partly. Both compounds undergo an essentially

(33) The compounds do not undergo deﬁned reductions (ill-deﬁned or

none at all) in the potential window provided by the solvent and, therefore,

were studied mainly in the anodic region.

(34) Deﬁnitions: E_paand i_paare anodic peak potential and anodic peak

current, respectively. Parameters of cathodic processes are denoted similarly

(E_pcand i_pc). Separation of the peaks: ∆E_p) E_pa- E_pc.

(35) Hansch, C.; Leo, A.; Taft, R. W. Chem. ReV. 1991, 91, 165.

(36) Weinberg, N. L.; Weinberg, H. R. Chem. ReV. 1968, 68, 449.

(37) (a) Ong, J. H. L.; Nataro, C.; Golen, J. A.; Rheingold, A. L.

Organometallics 2003, 22, 5027. (b) Zanello, P.; Opromolla, G.; Giorgi,

G.; Sasso, G.; Togni, A. J. Organomet. Chem. 1996, 506, 61. (c) Pilloni,

G.; Longato, B.; Corain, B. J. Organomet. Chem. 1991, 420, 57.

(38) An additional oxidative peak is observed for 4 (E_pa≈ 1.0 V),

probably due to amide oxidation.

(39) (a) Shaughnessy, K. H. Eur. J. Org. Chem. 2006, 1827. (b) Li, C.-J.

Chem. ReV. 2005, 105, 3095. (c) Franze´n, R.; Xu, Y. Can. J. Chem. 2005,

83, 266. (d) Pinault, N.; Bruce, D. W. Coord. Chem. ReV. 2003, 241, 1.

(40) (a) Miyaura, N. Metal-Catalyzed Cross-Coupling Reactions of

Organoboron Compounds with Organic Halides in Metal-Catalyzed Cross-

Coupling Reactions, 2nd ed.; de Meijere, A. ; Diederich, F., Eds.; Wiley-

VCH: Weinheim 2004; Vol. 1, Chapter 2, pp 41-123. (b) Miayura, N.;

Suzuki, A. Chem. ReV. 1995, 95, 2457. (c) Suzuki, A. J. Organomet. Chem.

1999, 576, 147. (d) Miyaura, N. Top. Curr. Chem. 2002, 219, 11.

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3297

Scheme 4. Suzuki-Miyaura Cross-Coupling of 4-Bromotoluene

to Give Biphenyl 13

Table 6. Catalytic Results Obtained with the 5/Pd(OAc)₂System in

Different Solvents^a

yield of 13 (%)^b

entry

solvent

dioxane

dioxane/H₂O

EtOH

EtOH/H₂O

H₂O

toluene/H₂O

t ) 6 h

t ) 16 h

95 (89)

100 (96)

100 (92)

100 (94)

95 (91)

50 (-)

100 (97)

100 (98)

100 (93)

100 (95)

100 (93)

49 (-)

Figure 13. Kinetic proﬁle of the coupling reaction performed in

water with Pd(OAc)₂/5 catalyst. The conversion attained with a

ligandless catalyst after 6 h is indicated for comparison. Conditions:

0.5 mol % Pd catalyst, 80 °C.

^a4-Bromotoluene (1.0 mmol), phenylboronic acid (1.2 mmol), K₂CO₃

(2 mmol) in the appropriate solvent (5 mL). Reactions were performed

with 0.5 mol % Pd catalyst at 80 °C for 6 or 16 h. ^bNMR yield

(isolated yield in parentheses). The results are an average of two

independent runs.

Table 7. Comparison of Catalytic Efﬁciency of Phosphinoamide-

and Hdpf-Supported Catalysts in Various Solvents^a

yield of 13 (%)^b

entry

solvent

dioxane

dioxane/H₂O

EtOH

EtOH/H₂O

H₂O

[Pd]/1

[Pd]/5

[Pd]/6

[Pd]/Hdpf

100

^a4-Bromotoluene (1.0 mmol), phenylboronic acid (1.2 mmol), K₂CO₃

(2 mmol) in the appropriate solvent (5 mL). Reactions were performed

with 0.5 mol % Pd catalyst at 80 °C for only 2 h ([Pd] ) Pd(OAc)₂).

The yields were determined from integration of H NMR spectra.

boxylate. The beneﬁciary effect of the polar side chain in 5

was corroborated through a comparison of the results obtained

with Pd(OAc)₂/L (L ) 1, 5, and 6) and Pd(OAc)₂/Hdpf catalysts

at shorter reaction times (i.e., at lower conversions; Table 7).

In all solvents tested, the reaction with the former system

involving Hdpf Gly-amides possessing extended polar pendants

gave better yields that the Hdpf-based catalyst. Furthermore,

the catalyst supported with acid 5 showed the least pronounced

dependence of its catalytic performance on the nature of the

reaction solvent and exerted practically the same or better

activity than other Gly-Hdpf amides (Table 7).

Figure 12. Kinetic proﬁles for the coupling reactions performed

in dioxane and in dioxane/water (1:1): Pd(OAc)₂/5 in dioxane (b),

Pd(OAc)₂/5 in dioxane/water (1), Pd(OAc)₂in dioxane (O),

Pd(OAc)₂in dioxane/water (∆). Conditions: 0.5 mol % Pd catalyst,

80 °C.

motoluene (a deactivated substrate) to give 4-methylbiphenyl

(13; Scheme 4).

Since the best catalytic results were obtained in ethanol and

in ethanol/water (1:1), these solvents were studied in more detail

and compared with pure water (Table 8). Coupling reactions in

ethanolic media proceeded signiﬁcantly faster than in other

solvents tested but with only a marginal effect of the supporting

ligand. The efﬁciency of Pd(OAc)₂and 5/Pd(OAc)₂catalysts

was practically equal, the former system exerting somewhat

lower conversions in ethanol and higher conversions in ethanol/

water. This acceleration can be attributed to a mild reducing

ability of ethanol facilitating the generation of a molecular

catalyst (L_nPd⁰) or catalytically active, solvent- and ligand-

stabilized ﬁne metal particles.⁴¹Upon decreasing the catalyst

amount to 0.1 and 0.05 mol %, the reactions still proceeded

with good to excellent yields within 30 min, particularly in

aqueous ethanol, where the turnover frequencies (TOFs) ex-

ceeded 3600 mmol product (mmol Pd)^-1h^-1. At 0.01 mol %

catalyst loading, the conversions dropped below 50% even in

Initial tests were carried out in ethanol and dioxane, in their

aqueous mixtures (1:1 v/v), and also in pure water, all at 80 °C

and in the presence of 0.5 mol % palladium catalyst based on

acid 5 as the most polar donor in the series. The results (Table

6) already indicated that the coupling reaction proceeds rapidly

and with excellent conversions in all homogeneous reaction

media. In contrast, the results obtained in a toluene/water

biphasic mixture were rather disappointing, as the conversion

reached only ca. 50% within 6 h and did not increase any further.

Subsequent kinetic experiments in dioxane and in dioxane/

water revealed (i) that the 5/Pd(OAc)₂catalytic system is much

more efﬁcient than the corresponding ligand-free catalysts (i.e.,

Pd(OAc)₂itself) and (ii) that the reaction proceeds faster in a

dioxane/water mixture than in dioxane itself (Figure 12). A

considerably higher activity of the phosphine-supported catalyst

was noted also in water (Figure 13). Apparently, the polar

phosphine stabilizes the catalytically active species (via P-

coordination) and positively affects its solubility (stability) in

polar reaction media, acting as a surfactant-like anionic car-

(41) Astruc, D. Inorg. Chem. 2007, 46, 1884, and references therein.

3298 Organometallics, Vol. 28, No. 11, 2009

Tauchman et al.

Table 8. Comparison of Catalytic Results Obtained in Ethanol, Aqueous Ethanol, and Water^a

yield to 13 (%)

reaction time (h)

[Pd]/5 in EtOH

[Pd] in in EtOH

[Pd]/5 in EtOH/H₂O

[Pd] in EtOH/H₂O

[Pd]/5 in H₂O

[Pd] in H₂O

0.5

1.0

2.0

4.0

100

67^e

n.a.

6.0

0.5^b

0.5^c

0.5^d

n.a.

^a4-Bromotoluene (1.0 mmol), phenylboronic acid (1.2 mmol), and K₂CO₃(2 mmol) were reacted in the appropriate solvent (5 mL) in the presence of

0.5 mol % Pd catalyst at 80 °C for the reaction time speciﬁed. [Pd] ) Pd(OAc)₂. ^b0.1 mol % Pd catalyst. ^c0.05 mol % Pd. ^d0.01 mol % Pd. ^eUnder

identical conditions (0.5 mol % Pd, 1 h), the analogous catalysts [Pd]/1 and [Pd]/6 afforded 60% and 51% yields of the coupling product, respectively.

the best solvent (Table 8).⁴²As opposed to ethanolic media,

the efﬁciency of both catalytic systems differed dramatically

from magnetically nonequivalent protons in the AA′BB′ and

AA′BB′X spin systems (X ) ³¹P) of the ferrocene unit. IR spectra

were recorded with an FT IR Nicolet Magna 650 spectrometer in

the range 400-4000 cm^-1. Positive ion electron impact (EI) and

fast atom bombardment (FAB) mass spectra were obtained on a

VG Analytical ZAB EQ spectrometer. Electrospray (ESI) mass

spectra were recorded with a Bruker Esquire 3000 or with a Thermo

Scientiﬁc LTQ Orbitrap XL spectrometers. Samples were dissolved

in a little dichloromethane or dimethylsulfoxide and then diluted

with methanol. Melting points were determined on a Koﬂer block.

in pure water (Table 8). Only the phosphine-supported catalyst

gave good conversions, with acid 5 performing better than

compounds 1 and 6.

Concluding Remarks. Amide coupling of Hdpf with glycine

esters smoothly affords novel organometallic phosphino-car-

boxamides. These donors can be designed in modular fashion,

allowing for facile modiﬁcations at both the ferrocene moiety

(e.g., through variation of the phosphorus groups) and in the

amino acid moiety (e.g., by modiﬁcation at the carboxyl group

or by changing the amino acid moiety). The multidonor nature

of these ligands results in their high coordination versatility,

already demonstrated by the series of (L^NC)Pd complexes

prepared form the archetypal ligand 1. When the amino acid

pendant groups remain uncoordinated, they can be utilized for

the construction of deﬁned supramolecular networks (see the

structures of 9 and 9a, in which the molecular arrays propagate

via a combination of dative and hydrogen bonds, differently for

both solvatomorphs). Alternatively, a free amino acid pendant

increases the solubility of these donors in polar organic solvents

and in water, making the phosphinoferrocene carboxamides

attractive as ligands for catalysis in such “greener” reaction

media.

Electrochemical measurements were carried out with a computer-

controlled µAUTOLAB III (Eco Chemie) multipurpose potentiostat

at room temperature using a standard three-electrode cell equipped

with a platinum disk (AUTOLAB RDE, 3 mm diameter) as the

working electrode, platinum sheet auxiliary electrode, and saturated

calomel reference electrode (SCE) separated by a salt bridge.

Samples were dissolved in dichloromethane (Fluka, absolute,

declared H₂O content below 0.005%) to give a solution containing

ca. 5 × 10^-4M of the analyte and 0.1 M Bu₄N[PF₆] (Fluka,

purissimum for electrochemistry). The solutions were deaerated with

argon before the measurement and then kept under an argon blanket.

The potentials are given relative to a ferrocene/ferrocenium

reference.

Safety Note. Caution! Although we have not encountered any

problems, it should be noted that perchlorate salts of metal

complexes with organic ligands are potentially explosive and should

be handled only in small quantities and with care.

Experimental Section

Preparation of 1-(Diphenylphosphino)-1′-{N-[(methoxycarbon-

yl)methyl]carbamoyl}ferrocene (1). Hdpf (4.15 g, 10 mmol) and

1-hydroxybenzotriazole (1.62 g, 12 mmol) were dissolved in

dichloromethane (90 mL). The solution was cooled in an ice bath

and treated with N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide

(2.10 mL, 12 mmol). After stirring at 0 °C for 30 min, a mixture

of [H₃NCH₂CO₂Me]Cl (1.80 g, 14 mmol), triethylamine (2.25 mL,

16 mmol), and dichloromethane (90 mL) was introduced, and the

cooling bath was removed. The reaction mixture was stirred

overnight at room temperature and then washed with 10% aqueous

citric acid (50 mL), saturated aqueous NaHCO₃(2× 50 mL), and

brine (50 mL). After drying over MgSO₄, the volatiles were

removed under vacuum, and the residue was puriﬁed by ﬂash

chromatography (silica gel, dichloromethane/methanol, 10:1, v/v).

A single orange band was collected and evaporated to afford

analytically pure 1 as an orange solid. Yield: 4.95 g (98%).

Materials and Methods. Unless noted otherwise, the syntheses

were performed under an argon atmosphere and with exclusion of

direct daylight. Hdpf,³glycine methyl ester hydrochloride,⁴³

[PdCl₂(cod)],⁴⁴and di-µ-chloridobis{[(2-dimethylamino-κN)meth-

yl]phenyl-κC¹}dipalladium(II)⁴⁵were prepared by the literature

procedures. Solvents used in the syntheses were dried by standing

over appropriate drying agents and distilled under argon: dichlo-

romethane and chloroform (K₂CO₃), dioxane (sodium), acetonitrile

(P₂O₅). Methanol was distilled from MeONa. Other chemicals

(Fluka, Aldrich) and solvents used for crystallizations and in

chromatography were used without further puriﬁcation.

NMR spectra were measured with a Varian Unity Inova

spectrometer (¹H, 399.95; ¹³C, 100.58; ³¹P, 161.90 MHz) at 25 °C.

Chemical shifts (δ) are given relative to internal SiMe₄(¹³C and

¹H) or to external 85% aqueous H₃PO₄(³¹P). In addition to the

standard notation of the signal multiplicity, vt and vq are used to

distinguish virtual triplets and quartets (J′ ) 1.8-2.0 Hz) arising

Mp: 131-133 °C (CHCl₃). H NMR (CDCl₃): δ 3.75 (s, 3 H,

OMe), 4.07 (d, J_HH) 5.6 Hz, 2 H, NHCH₂), 4.20 (vq, 2 H, fc),

4.25 (vt, 2 H, fc), 4.50 (vt, 2 H, fc), 4.60 (vt, 2 H, fc), 6.08 (t, ³J_HH

) 5.6 Hz, 1 H, NH), 7.29-7.41 (m, 10 H, PPh₂). ¹³C{¹H} NMR

(CDCl₃): δ 41.19 (NHCH₂), 52.30 (OMe), 69.46 (2 C, CH fc), 71.77

(42) When the less reactive 4-chlorotoluene was used instead of

4-bromotoluene as the substrate, the coupling reaction did not proceed

(aqueous ethanol, 80 °C, 0.5 mol % Pd(OAc)₂/5, 24 h).

(43) (a) Meyers, A. I.; Williams, D. R.; Erickson, G. W.; White, S.;

Druelinger, M. J. Am. Chem. Soc. 1981, 103, 3081. (b) Brenner, M.; Huber,

W. HelV. Chim. Acta 1953, 36, 1109.

(2 C, CH fc), 72.96 (d, J_PC) 4 Hz, 2 C, CH fc), 74.43 (d, J_PC

)

15 Hz, 2 C, CH fc), 75.75 (C-CONH fc), 128.26 (d, J_PC) 7 Hz,

4 C, CH_mPPh₂), 128.70 (2 C, CH_pPPh₂), 133.50 (d, ²J_PC) 19 Hz,

(44) Drew, D.; Doyle, J. R. Inorg. Synth. 1972, 13, 47.

(45) Cope, A. C.; Friedrich, E. C. J. Am. Chem. Soc. 1968, 90, 909.

4 C, CH_oPPh₂), 138.49 (d, J_PC) 9 Hz, 2 C, C_ipsoPPh₂), 170.25

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3299

(CONH), 170.51 (CO₂Me); the signal due C-P of fc is obscured

by the solvent resonance. ³¹P{¹H} NMR (CDCl₃): δ -16.9 (s). IR

(Nujol): ν/cm^-1ν_NH3332 s, ν_CO(ester) 1758 vs, amide I 1650 vs,

amide II 1544 vs, 1439 s, 1403 m, 1360 m, 1313 m, 1208 s, 1182 s,

1029 m, 836 w, 825 w, 747 m, 697 s, 489 m. MS (EI+): m/z

(relative abundance) 485 (100, M^{+ ·}), 454 (5, [M - OMe]⁺), 412

(80, [M

CH₂CO₂Me]⁺), 397 (8), 370 (6), 321 (55,

“[Fe(C₅H₄PPh₂)O]⁺”), 305 (15), 266 (20), 226 (16), 201 (56,

[Ph₂PO]⁺), 183 (18, [PPh₂- 2H]⁺), 171 (24), 149 (45), 121 (15,

[FeC₅H₅]⁺), 115 (23), 98 (17), 83 (31), 55 (59). HR-MS (EI+):

calcd for C₂₆H₂₄NO₃P⁵⁶Fe (M^+•) 485.0843, found 485.0821. Anal.

Calcd for C₂₆H₂₄NO₃PFe: C 64.35, H 4.99, N 2.89. Found: C 64.29,

H 4.89, N 2.85.

Preparation of 1-(Diphenylphosphino)-1′-{N-[(tert-butyloxycar-

bonyl)methyl]carbamoyl}ferrocene (2). Compound 2 was prepared

similarly to 1, starting with Hdpf (414 mg, 1.0 mmol), 1-hydroxy-

benzotriazole (162 mg, 1.2 mmol), N-(3-dimethylaminopropyl)-N′-

ethylcarbodiimide (186 mg, 1.2 mmol), [H₃NCH₂CO₂CMe₃]Cl (201

mg, 1.2 mmol), and triethylamine (0.17 mL, 1.2 mmol). Isolation

as above afforded 2 as an orange solid. Yield: 501 mg (95%).

Mp: 130-132 °C (CHCl₃). H NMR (CDCl₃): δ 1.49 (s, 9 H,

CMe₃), 3.97 (d, J_HH) 5.2 Hz, 2 H, NHCH₂), 4.19 (vq, 2 H, fc),

4.24 (vt, 2 H, fc), 4.48 (vt, 2 H, fc), 4.59 (vt, 2 H, fc), 6.05 (t, ³J_HH

) 5.2 Hz, 1 H, NH), 7.29-7.40 (m, 10 H, PPh₂). ¹³C{¹H} NMR

(CDCl₃): δ 28.10 (3 C, CMe₃), 41.99 (NHCH₂), 69.38 (2 C, CH

fc), 71.79 (d, J ≈ 1 Hz, 2 C, CH fc), 73.10 (d, J_PC) 4 Hz, 2 C,

CH fc), 74.40 (d, J_PC) 14 Hz, 2 C, CH fc), 76.21 (C-CONH fc),

82.05 (CMe₃), 128.28 (d, ³J_PC) 7 Hz, 4 C, CH_mPPh₂), 128.78 (2

C, CH_pPPh₂), 133.50 (d, J_PC) 19 Hz, 4 C, CH_oPPh₂), 138.17

(d, J_PC) 7 Hz, 2 C, C_ipsoPPh₂), 169.22, 169.93 (2× CdO); the

signal due to C(fc)-P is obscured by the solvent resonance. ³¹P{¹H}

NMR (CDCl₃): δ -16.9 (s). IR (Nujol): ν/cm^-1ν_NH3296 w, ν_CO

(ester) 1743 vs, amide I 1640 vs, amide II 1539 vs, 1305 m, 1224 s,

1154 vs, 1093 w, 1069 w, 1028 m, 999 w, 905 w, 889 w, 844 m,

771 w, 744 s, 697 s, 496 m. MS (EI+): m/z (relative abundance)

528 (35, M^{+ ·}), 454 (5, [M - OCMe₃]⁺), 427 (10), 412 (45, [M -

CH₂CO₂CMe₃]⁺), 397 (7), 370 (6), 320 (25, “[Fe(C₅H₄PPh₂)O]⁺”),

304 (10), 225 (9), 200 (20, [Ph₂PO]⁺), 183 (11, [Ph₂P - 2H]⁺),

170 (15), 149 (9), 136 (10), 120 (9, [FeC₅H₅]⁺), 114 (7), 94 (15),

81 (38), 55 (71). HR-MS (EI+): calcd for C₂₉H₃₀NO₃P⁵⁶Fe (M^{+ ·}

)

527.1313, found 527.1329. Anal. Calcd for C₂₉H₃₀NO₃PFe: C 66.04,

H 5.73, N 2.66. Found: C 65.88, H 5.53, N 2.77.

Preparation of 1-(Diphenylphosphinoyl)-1′-{N-[(methoxycarbon-

yl)methyl]carbamoyl}ferrocene (3). In air, hydrogen peroxide (0.10

mL 30%, 0.8 mmol) was added dropwise to an ice-cooled solution

of 1 (123 mg, 0.25 mmol) in acetone (10 mL). The mixture was

stirred at 0 °C for 30 min and diluted with water (5 mL) and 10%

aqueous Na₂S₂O₃(1 mL). The acetone was removed under reduced

pressure, and the aqueous residue was extracted with chloroform

(2× 10 mL). Combined organic extracts were washed with brine,

dried (MgSO₄), and evaporated. The solid residue was dissolved

in ethyl acetate (3 mL), and the solution ﬁltered (PTFE syringe

ﬁlter, pore size 0.45 µmm) and carefully layered with hexane (8

mL). Crystallization by liquid-phase diffusion over several days

afforded 3 as orange crystals, which were isolated by suction and

dried in air. Yield: 122 mg (96%).

Mp: 201-203 °C (ethyl acetate). H NMR (CDCl₃): δ 3.62 (s,

3 H, OMe), 4.12 (d, J_HH) 6.1 Hz, 2 H, NHCH₂), 4.12 (vt, 2 H,

fc), 4.51 (vq, 2 H, fc), 4.61 (vq, 2 H, fc), 5.06 (vt, 2 H, fc),

7.44-7.73 (m, 10 H, PPh₂), 9.49 (t, J_HH) 6.1 Hz, 1 H, NH).

¹³C{¹H} NMR (CDCl₃): δ 41.36 (NHCH₂), 51.84 (OMe), 70.54 (2

C, CH fc), 70.87 (2 C, CH fc), 72.76 (d, J_PC) 10 Hz, 2 C, CH fc),

73.28 (d, ¹J_PC) 115 Hz, C-P fc), 75.21 (d, J_PC) 13 Hz, 2 C, CH

fc), 78.26 (C-CONH fc), 128.43 (d, ³J_PC) 12 Hz, 4 C, CH_mPPh₂),

131.48 (d, ²J_PC) 10 Hz, 4 C, CH_oPPh₂), 131.93 (d, ⁴J_PC) 3 Hz,

2 C, CH_pPPh₂), 132.87 (d, ¹J_PC) 108 Hz, 2 C, C_ipsoPPh₂), 170.72,

170.80 (2 × CdO). ³¹P{¹H} NMR (CDCl₃): δ 32.1 (s). IR (Nujol):

3300 Organometallics, Vol. 28, No. 11, 2009

ν/cm^-1

Tauchman et al.

_NH3223 w, ν_CO(ester) 1754 vs, amide I 1664 vs, amide II

HR-MS (FAB+): calcd for C₂₅H₂₂NO₃P⁵⁶FeK ([M + K]⁺) 510.0324,

1551 s, 1306 s, 1209 m, 1197 s, 1155 vs, 1119 s, 1068 w, 1047 w,

1036 w, 1001 w, 978 w, 854 w, 844 w, 823 w, 753 m, 703 s,

571 s, 537 s, 531 m, 515 m, 498 m, 483 w. MS (EI+): m/z (relative

abundance) 501 (36, M^+•), 470 (2, [M - OMe]⁺), 413 (2, [M -

NHCH₂CO₂Me]⁺), 386 (2), 338 (2), 321 (15, “[Fe(C₅H₄PPh₂)O]⁺”),

256 (5), 201 (4, [Ph₂PO]⁺), 149 (10), 137 (10), 109 (11), 97 (20),

85 (49), 83 (77), 69 (100), 55 (63). HR-MS (EI+): calcd for

C₂₆H₂₄NO₄P⁵⁶Fe (M^+•) 501.0792, found 501.0782. Anal. Calcd for

C₂₆H₂₄NO₄PFe: C 62.29, H 4.83, N 2.79. Found: C 62.28, H 4.83,

N 2.66.

found 510.0300.

Preparation of 1-(Diphenylphosphino)-1′-[N-(carbamoylmeth-

yl)carbamoyl]ferrocene (6). A solution of ester 1 (49 mg, 0.10

mmol) in methanol (5 mL) was added to liquid ammonia (5 mL)

while cooling to ca. -75 °C. After the addition, the cooling bath

was removed and the mixture was stirred at room temperature for

5 h. The volatiles were removed under vacuum, and the residue

was puriﬁed by column chromatography (silica gel, dichlormethane/

methanol, 5:1, v/v). Evaporation left an orange solid, which was

crystallized from ethyl acetate/hexane at 5 °C. The separated

crystalline product was ﬁltered off, washed with hexane, and dried

under vacuum to afford 6 as an orange solid. Yield: 35 mg (88%).

Preparation of 1-(Diphenylthiophosphoryl)-1′-{N-[(methoxy-

carbonyl)methyl]carbamoyl}ferrocene (4). A solution of 1 (128 mg,

0.26 mmol) and sulfur (12 mg, 0.37 mmol) in ethyl acetate (30

mL) was heated at reﬂux for 90 min. The mixture was cooled to

room temperature and evaporated. Puriﬁcation by ﬂash chroma-

tography (silica gel, dichloromethane/methanol, 20:1, v/v) followed

by evaporation afforded 4 as an orange solid. Yield: 134 mg (98%).

¹H NMR (CDCl₃): δ 4.00 (d, J_HH) 5.5 Hz, 2 H, NHCH₂),

4.14 (vq, 2 H, fc), 4.25 (vt, 2 H, fc), 4.45 (vt, 2 H, fc), 4.63 (vt, 2

H, fc), 5.64 br s, 1 H, CONH₂), 6.53 (br s, 1 H, CONH₂), 6.54 (t,

³J_HH) 5.5 Hz, 1 H, NH), 7.29-7.40 (m, 10 H, PPh₂). ¹³C{¹H}

NMR (CDCl₃): δ 43.25 (NHCH₂), 69.47 (2 C, CH fc), 71.98 (2 C,

CH fc), 72.86 (d, J_PC) 3 Hz, 2 C, CH fc), 74.35 (d, J_PC) 15 Hz,

2 C, CH fc), 75.59 (C-CONH fc), 77.67 (d, J ) 7 Hz, C-P fc),

128.29 (d, ³J_PC) 7 Hz, 4 C, CH_mPPh₂), 128.77 (2 C, CH_pPPh₂),

133.47 (d, ²J_PC) 20 Hz, 4 C, CH_oPPh₂), 138.35 (d, ¹J_PC) 9 Hz,

2 C, C_ipsoPPh₂), 170.90, 171.68 (2× CdO). ³¹P{¹H} NMR (CDCl₃):

δ -17.2 (s). IR (Nujol): ν/cm^-1ν_NH3262 m, ν_NH3138 m, amide

I 1694 s, amide I 1644 vs, amide II 1551 s, 1307 s, 1251 m, 1191 w,

1160 w, 1120 w, 1023 w, 996 w, 840 w, 810 w, 743 s, 699 s,

573 w, 501 m. HR-MS (ESI+): calcd for C₂₅H₂₄⁵⁶FeN₂O₂P ([M +

H]⁺) 471.0925, found 471.0919. Anal. Calcd for C₂₅H₂₃N₂O₂PFe:

C 63.85, H 4.93, N 5.96. Found: C 63.44, H 4.93, N 5.81.

Preparation of Complex 7. A solution of 1 (195 mg, 0.40 mmol)

in chloroform (6 mL) was added to solid [PdCl₂(cod)] (52 mg, 0.20

mmol). The formed dark red solution was stirred for 1 h and then

precipitated with pentane (60 mL). The separated solid was collected

by ﬁltration and dried under vacuum to give 7. Yield: 220 mg

(96%), orange solid.

Mp: 153-155 °C (toluene). H NMR (CDCl₃): δ 3.76 (s, 3 H,

OMe), 4.02 (vt, 2 H, fc), 4.10 (d, J_HH) 6.1 Hz, 2 H, NHCH₂),

4.49 (vq, 2 H, fc), 4.66 (vq, 2 H, fc), 4.95 (vt, 2 H, fc), 7.42-7.76

(m, 10 H, PPh₂), 7.85 (t, ³J_HH) 6.1 Hz, 1 H, NH). ¹³C{¹H} NMR

(CDCl₃): δ 41.11 (NHCH₂), 52.18 (OMe), 71.11 (2 C, CH fc), 71.26

(2 C, CH fc), 73.28 (d, J_PC) 10 Hz, 2 C, CH fc), 75.08 (d, J_PC

)

13 Hz, 2 C, CH fc), 76.10 (d, J_PC) 97 Hz, C-P fc), 77.68 (C-

CONH fc), 128.38 (d, J_PC) 13 Hz, 4 C, CH_mPPh₂), 131.60 (d,

⁴J_PC) 3 Hz, 2 C, CH_pPPh₂), 131.62 (d, J_PC) 10 Hz, 4 C, CH_o

PPh₂), 133.45 (d, J_PC) 87 Hz, 2 C, C_ipsoPPh₂), 170.13, 170.39

(2× CdO). ³¹P{¹H} NMR (CDCl₃): δ 42.9 (s). IR (neat, ATR):

ν/cm^-1

ν_NH3295 m, ν_CO(ester) 1750 vs, amide I 1648 vs, amide II

1535 vs, 1305 m, 1174 s, 1102 s, 1028 s, 1001 m, 978 m, 836 m,

749 s, 713 vs, 693 s, 652 s, 538 m, 484 s. MS (EI+): m/z (relative

abundance) 517 (100, M^{+ ·}), 486 (3, [M - OMe]⁺), 429 (3, [M -

NHCH₂CO₂Me]⁺), 386 (6), 368 (5), 337 (64, “[Fe(C₅H₄PPh₂)S]⁺”),

321 (7), 273 (6), 256 (8), 217 (7, Ph₂PS⁺), 183 (14), 171 (10), 129

(12), 111 (14), 97 (28), 69 (54), 55 (83). HR-MS (EI+): calcd for

C₂₆H₂₄NO₃PS⁵⁶Fe (M^{+ ·}) 517.0564, found 517.0553. Anal. Calcd

for C₂₆H₂₄NO₃PSFe: C 60.36, H 4.68, N 2.71. Found: C 60.18, H

4.63, N 2.63.

¹H NMR (CDCl₃): δ 3.73 (s, 3 H, OMe), 3.93 (d, J_HH) 5.7

Hz, 2 H, NHCH₂), 4.58 (vt, 2 H, fc), 4.63 (m, 2 H, fc), 4.65 (vt, 2

H, fc), 4.90 (vt, 2 H, fc), 6.52 (t, J_HH) 5.7 Hz, 1 H, NH),

7.30-7.67 (m, 10 H, PPh₂). ¹³C{¹H} NMR (CDCl₃): δ 41.10

(NHCH₂), 52.23 (OMe), 70.14 (2 C, CH fc), 72.98 (apparent t, J′

) 27 Hz, C-P fc), 73.43 (2 C, CH fc), 74.05 (apparent t, J′ ) 4

Hz, 2 C, CH fc), 76.91 (C-CONH fc), ca. 77.03 (apparent t, J′ )

5 Hz, 2 C, CH fc), 127.92 (apparent t, J′ ) 5 Hz, 4 C, CH PPh₂),

130.55 (2 C, CH PPh₂), 130.80 (apparent t, J′ ) 25 Hz, 2 C, C_ipso

PPh₂), 134.12 (apparent t, J′ ) 6 Hz, 4 C, CH PPh₂), 169.94, 170.38

(2× CdO). ³¹P{¹H} NMR (CDCl₃): δ 15.9 (s). IR (Nujol): ν/cm^-1

3238 s, 3182 w, 3106 s, 3084 m, ν_CO(ester) 1750 vs, amide I 1632

vs, amide II 1557 vs, 1319 m, 1307 m, 1211 s, 1199 s, 1174 s,

1096 m, 1036 m, 1006 w, 877 w, 842 w, 773 w, 743 m, 710 m,

690 m, 628 w, 517 s, 501 s, 477 m, 455 w. MS (ESI+): m/z 1171

([M + Na]⁺). Anal. Calcd for C₅₂H₄₈N₂O₆P₂Fe₂PdCl₂: C 54.41, H

4.22, N 2.44. Found: C 54.55, H 4.22, N 2.25.

Preparation of 1-(Diphenylphosphino)-1′-[N-(carboxymethyl)-

carbamoyl]ferrocene (5). Aqueous sodium hydroxide (200 mg, 5.0

mmol in 17 mL of deoxygenated water) was added to a solution of

1 in dioxane (485 mg, 1.0 mmol in 17 mL), and the mixture was

heated to 50 °C overnight. The reaction mixture was cooled in ice,

acidiﬁed with 85% H₃PO₄to pH ≈ 2, and extracted with

dichloromethane. The organic layer was dried (MgSO₄) and

evaporated, leaving a brown residue, which was puriﬁed ﬂash

chromatography (silica gel, dichloromethane/methanol, 1:1, v/v).

The single orange band was collected and evaporated under vacuum,

and the residue was dried over sodium hydroxide to give acid 5 as

a glassy orange solid. Yield: 446 mg (95%). The product typically

contains traces of the corresponding phosphine oxide, which cannot

be efﬁciently removed by chromatography or crystallization.

Preparation of Complex 8. A solution of acid 5 (20 mg, 0.04

mmol) in hot glacial acetic acid (3 mL) was added to an equivalent

amount of Na₂[PdCl₄] dissolved in water (6 mg, 0.02 mmol in 2

mL), yielding a dark red solution that quickly deposited a

microcrystalline solid. After standing for several minutes at room

temperature, the solid was ﬁltered off, washed with aqueous acetic

acid (ca. 50%), and dried under vacuum. Yield: 19 mg (81%) of

[PdCl₂(5-κP)₂] · 3H₂O (8), red microcrystalline solid.

¹H NMR (DMSO): δ 3.68 (d, J_HH) 5.6 Hz, 2 H, NHCH₂),

4.11 (vq, 2 H, fc), 4.13 (vt, 2 H, fc), 4.53 (vt, 2 H, fc), 4.68 (vt, 2

H, fc), 7.80 (t, J_HH) 5.6 Hz, 1 H, NH), 7.26-7.41 (m, 10 H,

PPh₂). ¹³C{¹H} NMR (DMSO): δ 41.99 (NHCH₂), 68.76 (2 C, CH

fc), 71.20 (2 C, CH fc), 73.05 (d, J_PC) 4 Hz, 2 C, CH fc), 74.47

(d, J_PC) 15 Hz, 2 C, CH fc), 76.45 (d, J_PC) 9 Hz, C-P fc),

77.07 (C-CONH fc), 128.20 (d, J_PC) 7 Hz, 4 C, CH_mPPh₂),

128.52 (2 C, CH_pPPh₂), 132.90 (d, ²J_PC) 20 Hz, 4 C, CH_oPPh₂),

IR (Nujol): ν/cm^-1

ν_NH3336 w, ν_CO(carboxyl) 1715 vs, amide

138.36 (d, J_PC) 10 Hz, 2 C, C_ipsoPPh₂), 168.21, 172.19 (2×

I 1606 vs, amide II 1541 vs, 1303 w, 1233 vs, 1196 w, 1166 m,

1097 m, 1061 w, 1041 m, 1030 w, 1000 w, 938 w, 834 w, 771 w,

745 s, 696 s, 627 w, 610 m, 514 vs, 498 w, 471 s, 455 w, 436 w.

MS (ESI+): m/z 1047 ([M - 2Cl - H]⁺), 526 ([5 + O + K]⁺),

510 ([5 + K]⁺). MS (ESI-): m/z 612 ([Pd(5)Cl - 2H]^-), 486 ([5

CdO). ³¹P{¹H} NMR (DMSO): δ -18.0 (s). IR (Nujol): ν/cm^-1

_NH3335 w, ν_CO(carboxyl) 1732 s, amide I 1637 vs, amide II 1538

vs, 1303 m, 1193 m, 1160 m, 1119 m, 1027 m, 999 w, 888 w,

872 m, 833 m, 743 vs, 698 vs, 634 w, 613 w, 570 w, 493 s, 452 m.

Phosphinoferrocenyl Gly-carboxamides

Organometallics, Vol. 28, No. 11, 2009 3301

+ O - H]^-). Anal. Calcd for C₅₀H₄₄N₂O₆P₂Fe₂PdCl₂· 3H₂O: C

51.16, H 4.29, N 2.39. Found: C 50.99, H 4.10, N 2.09.

Preparation of Complex 9. A solution of 6 (19 mg, 0.04 mmol)

in dichlormethane (5 mL) was added to solid [PdCl₂(cod)] (6 mg,

0.02 mmol). The resulting dark red solution was stirred at room

temperature for 1 h and evaporated under vacuum. The residue was

dissolved in hot glacial acetic acid (5 mL), and the solution was

allowed to crystallize by cooling slowly to room temperature. The

separated solid was ﬁltered off, washed with 50% aqueous acetic

acid and water, and dried under vacuum. Yield: 17 mg (63%) of

[PdCl₂(6-κP)₂] · 4CH₃CO₂H (9) as an orange crystalline solid.

stirred for 30 min in the dark and ﬁltered. The ﬁltrate was

concentrated to ca. 2 mL under vacuum and layered with diethyl

ether. Crystallization at +4 °C for several days afforded 11 as

orange crystals, which were ﬁltered off, washed with diethyl ether,

and dried under vacuum. Yield: 75 mg (91%).

¹H NMR (CD₂Cl₂): δ 2.70 (d, ⁴J_PH) 2.7 Hz, 6 H, NMe₂), 3.63

(s, 3 H, OMe), 4.02 (d,³J_HH) 5.9 Hz, 2 H, NHCH₂), 4.10 (vq, 2

H, fc), 4.14 (d,⁴J_PH) 2.3 Hz, 2 H, CH₂NMe₂), 4.65 (d of vt, 2 H,

fc), 4.67 (vt, 2 H, fc), 5.61 (bt vt, 2 H, fc), 6.30 (ddd, J_HH) 1.2,

6.6, ca. 7.9 Hz, 1 H, C₆H₄), 6.38 (tdd, J_HH) ca. 7.9, 1.6, 0.6 Hz,

1 H, C₆H₄), 6.85 (td, J_HH) 1.2, 7.3 Hz, 1 H, C₆H₄), 7.01 (dd, J_HH

) 1.7, 7.4 Hz, 1 H, C₆H₄), 7.37-7.82 (m, 10 H, PPh₂), 8.14 (br t,

³J_HH≈ 5.5 Hz, 1 H, NH). ¹³C{¹H} NMR (CD₂Cl₂): δ 42.64

(NHCH₂), 49.75 (d, ³J_PC) 2 Hz, 2 C, NMe₂), 52.61 (d, J ≈ 2 Hz,

OMe), 71.99 (d, ³J_PC) 4 Hz, CH₂NMe₂), 72.60 (d, ¹J_PC) 58 Hz,

C-P fc), 73.40 (br, 2 C, CH fc), 73.75 (C-CONH fc), 74.04 (2 C,

CH fc), 74.31 (d, J_PC) 7 Hz, 2 C, CH fc), 76.84 (d, J_PC) 10 Hz,

2 C, CH fc), 123.47 (CH C₆H₄), 125.20 (CH C₆H₄), 125.94 (d, J_PC

) 6 Hz, CH C₆H₄), 129.08 (d, J_PC) 11 Hz, 4 C, CH PPh₂), 130.13

¹H NMR (CDCl₃): δ 2.10 (s, 6 H, CH₃CO₂H), 3.97 (d, J_HH

)

5.7 Hz, 2 H, NHCH₂), 4.55 (m, 4 H, fc), 4.63 (br s, 2 H, fc), 5.04

(vt, 2 H, fc), 6.23 (br s, 1 H, CONH₂), 6.64 (br s, 1 H, CONH₂),

7.34 (t, J_HH) 5.7 Hz, 1 H, NH), 7.35-7.65 (m, 10 H, PPh₂).

¹³C{¹H} NMR (CDCl₃): δ 20.74 (CH₃CO₂H), 43.20 (NHCH₂),

70.49 (2 C, CH fc), 73.41 (2 C, CH fc), 73.59 (apparent t, J′ ) 27

Hz, C-P fc), 73.76 (apparent t, J′ ) 4 Hz, 2 C, CH fc), 127.91

(apparent t, J′ ) 5 Hz, 4 C, CH PPh₂), 130.57 (2 C, CH PPh₂),

130.91 (apparent t, J′ ) 25 Hz, 2 C, C_ipsoPPh₂), 134.17 (apparent

t, J′ ) 6 Hz, 4 C, CH PPh₂), 170.85, 173.09 (2× CdO); 176.19

(CH₃CO₂H); two ferrocene resonances (C-CONH and one CH) are

obscured by the signal of the solvent. ³¹P{¹H} NMR (CDCl₃): δ

16.5 (s). IR (Nujol): ν/cm^-1ν_NH3401 m, ν_NH3337 w, amide I

1713 vs, amide I 1625 s, amide II 1547 s, 1437 s, 1304 s, 1255 s,

1167 m, 1101 m, 1059 w, 1028 w, 860 w, 836 w, 750 m, 693 m,

542 m, 512 s, 468 m, 454 w. MS (ESI+): m/z 1141 ([M + Na]⁺).

Anal. Calcd for C₅₀H₄₆N₄O₄P₂Fe₂PdCl₂· 4CH₃CO₂H: C 51.29, H

4.60, N 4.13. Found: C 51.28, H 4.47, N 4.03.

(d, J_PC) 49 Hz, 2 C, C_ipsoPPh₂), 131.88 (d, J_PC) 2 Hz, 2 C,

CH_pPPh₂), 134.81 (d, J_PC) 13 Hz, 4 C, CH PPh₂), 139.09 (d, J_PC

) 13 Hz, CH C₆H₄), 143.06 (d, J_PC) 4 Hz, C C₆H₄), 148.37 (d,

J_PC) 2 Hz, C C₆H₄), 169.48 (CO₂Me), 175.27 (CONH). ³¹P{¹H}

NMR (CD₂Cl₂): δ 30.9 (s). IR (Nujol): ν/cm^-1ν_NH3358 m,

_CO(ester) 1754 vs, amide I 1598 vs, amide II 1578 s, 1321 m,

1216 vs, 1180 s, 1167 m, 1126 vs, 1098 vs, 1067 vs, 1046 s, 1031 s,

1010 m, 996 m, 978 m, 931 m, 844 m, 814 m, 766 m, 750 vs,

699 s, 691 m, 622 s, 538 m, 520 s, 501 s, 494 m, 484 s, 468 m.

MS (ESI+): m/z 725 ([M - ClO₄]⁺; i.e., the cation). Anal. Calcd

for C₃₅H₃₆N₂O₇PFePdCl: C 50.93, H 4.40, N 3.40. Found: C 50.84,

H 4.49, N 3.60.

Preparation of Complex 12. Compound 10 (76 mg, 0.10 mmol)

and potassium tert-butoxide (22 mg, 0.20 mmol) were dissolved

in dichloromethane (5 mL), and the mixture was stirred at room

temperature overnight. Then, hexane (5 mL) and diatomaceous earth

(Celite; ca. 100 mg) were added, and stirring was continued for 10

min. The mixture was ﬁltered (PTFE, 0.45 µm), and the ﬁltrate

was evaporated under vacuum. The solid residue was dissolved in

ethyl acetate (2 mL) and layered with hexane. Crystallization at

room temperature over several days afforded 12 as dark orange

crystals. The separated product was ﬁltered off, washed with hexane,

and dried under vacuum. Yield: 43 mg (59%).

Preparation of Complex 10. A solution of 1 (97 mg, 0.20 mmol)

in chloroform (3 mL) was added to solid [{Pd(µ-Cl)(L^NC)}₂] (55

mg, 0.10 mmol). The resulting mixture was stirred at room

temperature for 1 h and ﬁltered (PTFE, 0.45 µm), and the ﬁltrate

was layered with pentane (8 mL). Crystallization at room temper-

ature over several days afforded 10 as a dark orange crystalline

solid, which was ﬁltered off and dried under vacuum. Yield: 145

mg (90%) of 10 · 0.35CHCl₃(the product retains the reaction

solvents).

¹H NMR (CD₂Cl₂): δ 2.83 (d, ⁴J_PH) 2.8 Hz, 6 H, NMe₂), 3.70

(s, 3 H, OMe), 4.03 (d, ³J_HH) 6.0 Hz, 2 H, NHCH₂), 4.14 (d,⁴J_PH

) 2.4 Hz, 2 H, CH₂NMe₂), 4.47 (vq, 2 H, fc), 4.53 (d of vt, 2 H,

fc), 4.69 (vt, 2 H, fc), 4.98 (vt, 2 H, fc), 6.27 (ddd, J_HH) 1.1, 6.4,

7.7 Hz, 1 H, C₆H₄), 6.36 (tdd, J_HH) ca. 7.6, 1.6, 0.6 Hz, 1 H,

¹H NMR (CD₂Cl₂): δ 2.59 (d, ⁴J_PH) 2.1 Hz, 3 H, NMe₂), 2.68

C₆H₄), 6.81 (td, J_HH) 7.2, 1.1 Hz, 1 H, C₆H₄), 7.00 (t, J_HH≈ 6

(d, J_PH) 3.2 Hz, 3 H, NMe₂), 3.32 (s, OMe), 3.44 (dd, J_PH)

Hz, 1 H, NH), 7.02 (dd, J_HH) 1.6, 7.3 Hz, 1 H, C₆H₄), 7.31-7.62

(m, 10 H, PPh₂). ¹³C{¹H} NMR (CD₂Cl₂): δ 41.46 (NHCH₂), 50.25

(d, ³J_PC) 3 Hz, 2 C, NMe₂), 52.41 (d, J ≈ 2 Hz, OMe), 70.59 (2

C, CH fc), 73.79 (2 C, CH fc), 73.96 (d, ³J_PC) 3 Hz, CH₂NMe₂),

74.13 (d, J_PC) 7 Hz, 2 C, CH fc), 75.76 (d,¹J_PC) 59 Hz, C-P fc),

77.33 (d, J_PC) 10 Hz, 2 C, CH fc), 77.73 (C-CONH fc), 122.83

(CH C₆H₄), 124.08 (CH C₆H₄), 125.20 (d, ⁴J_PC) 6 Hz, CH C₆H₄),

3.8, J_HH) 13.1 Hz, 1 H, CH₂NMe₂), 3.48 (dq, J ) 2.7, 1.3 Hz,

1 H, fc), 3.82 (d, J_HH) 15.7 Hz, 1 H, CONCH₂), 4.09 (m, 1 H,

fc), 4.16 (dt, J ) 1.2. 2.6 Hz, 1 H, fc), 4.30 (d, ²J_HH) 15.7 Hz, 1

H, CONCH₂), 4.50 (dt, J ) 1.5, 2.5 Hz, 1 H, fc), 4.68 (m, 2 H, fc),

4.85 (d, J_HH) 13.1 Hz, 1 H, CH₂NMe₂), 4.91 (dt, J ) 2.7, 1.5

Hz, 1 H, fc), 6.29 (t of m, J ) 7.5 Hz, 1 H, C₆H₄), 6.34 (ddd, J )

1.4, 5.5, 7.6 Hz, 1 H, C₆H₄), 6.44 (dt, J ) 2.6, 1.3 Hz, 1 H, fc),

6.74 (td, J ) 7.3, 1.3 Hz, 1 H, C₆H₄), 6.99 (d of unresolved t, J )

7.3 Hz, 1 H, C₆H₄), 6.99-8.09 (partly broad complex m, 10 H,

128.32 (d, J_PC) 11 Hz, 4 C, CH PPh₂), 130.99 (d, J_PC) 2 Hz,

2 C, CH_pPPh₂), 132.22 (d, ¹J_PC) 49 Hz, 2 C, C_ipsoPPh₂), 134.77

(d, J_PC) 12 Hz, 4 C, CH PPh₂), 138.80 (d, J_PC) 10 Hz, CH

PPh₂). ¹³C{¹H} NMR (CD₂Cl₂): δ 49.49 (d, J_PC) 2 Hz, NMe₂),

C₆H₄), 147.76 (d, J_PC) 2 Hz, C C₆H₄), 152.88 (C C₆H₄), 170.08,

170.90 (2× CdO). ³¹P{¹H} NMR (CD₂Cl₂): δ 32.7 (s). IR (Nujol):

ν/cm^-1ν_NH3216 s, ν_CO(ester) 1742 vs, 1660 w, amide I 1626 vs,

1577 w, amide II 1543 s, 1316 m, 1306 m, 1263 m, 1220 vs,

1195 m, 1169 s, 1097 m, 1040 m, 999 m, 975 m, 866 w, 844 m,

821 m, 762 m, 745 vs, 695 s, 630 m, 545 m, 521 s, 500 m, 475 m,

460 m. MS (ESI+): m/z 725 ([M - Cl]⁺). Anal. Calcd for

C₃₅H₃₆N₂O₃PFePdCl · 0.35CHCl₃: C 52.86, H 4.56, N 3.49. Found:

C 52.73, H 4.40, N 3.25.

Preparation of Complex 11. To a solution of 10 (76 mg, 0.10

mmol) in acetonitrile (4 mL) was added a solution of silver(I)

perchlorate in the same solvent (21 mg, 0.10 mmol in 2 mL). An

off-white precipitate (AgCl) formed immediately. The mixture was

50.12 (d, J_PC) 2 Hz, NMe₂), 51.11 (d, J ≈ 1 Hz, OMe), 51.23

(CONCH₂), 69.63 (CH fc), 69.80 (d, J_PC) 6 Hz, CH fc), 71.89

(CH fc), 72.77 (d, ¹J_PC) 63 Hz, C-P fc), 72.94 (CH fc), 74.17 (d,

³J_PC) 3 Hz, CH₂NMe₂), 75.40 (d, J_PC) 7 Hz, CH fc), 75.60 (d,

J_PC) 8 Hz, CH fc), 77.23 (dd, J ≈ 6 and 2 Hz, CH fc), 80.36 (d,

J_PC) 12 Hz, CH fc), 81.89 (C-CON fc), 122.67 (CH C₆H₄), 123.71

(CH C₆H₄), 125.05 (d, J_PC) 5 Hz, CH C₆H₄), ca. 127.9 (very br

m, 2 C, CH PPh₂), 129.09 (d, J_PC) 11 Hz, 2 C, CH PPh₂), 130.27

(d, J_PC) 2 Hz, CH_pPPh₂), 130.55 (d, J_PC) 45 Hz, C_ipsoPPh₂),

131.3 (br s, CH PPh₂), 131.83 (d, ⁴J_PC) 2 Hz, CH_pPPh₂), 133.06

(d, ¹J_PC) 51 Hz, C_ipsoPPh₂), 135.2 (br s, CH PPh₂), 136.50 (d, J_PC

) 15 Hz, 2 C, CH PPh₂), 140.37 (d, J_PC) 10 Hz, CH C₆H₄), 148.50

(d, J_PC) 2 Hz, C C₆H₄), 153.59 (d, J_PC) 4 Hz, C C₆H₄), 173.02

3302 Organometallics, Vol. 28, No. 11, 2009

Tauchman et al.

(CO₂Me), 174.53 (br, NCdO). ³¹P{¹H} NMR (CD₂Cl₂): δ 33.6

(s). IR (Nujol): ν/cm^-13058 w, 2360 w, ν_CO(ester) 1724 vs,

1653 w, amide I 1565 vs, 1554 s, 1318 m, 1243 m, 1203 w, 1193 w,

1160 m, 1100 m, 1028 m, 906 w, 843 m, 838 m, 813 m, 740 s,

697 s, 531 m, 518 s, 509 s, 481 m. MS (ESI+): m/z 725 ([M +

H]⁺). HR-MS (FAB+): calcd for C₃₅H₃₆N₂O₃P⁵⁶FePd ([M + H]⁺)

725.0848, found 725.0858. Anal. Calcd for C₃₅H₃₅N₂O₃PFePd: C

57.99, H 4.87, N 3.87. Found: C 57.70, H 4.94, N 3.57.

Reaction of 12 with HCl. Complex 12 (11 mg, 15 µmol) was

dissolved in dichloromethane (2 mL), and to the resulting solution

was added a methanolic solution of HCl (21 µL 0.7 M, 15 µmol).

The mixture was stirred at room temperature for 2 h and evaporated.

A subsequent analysis by ¹H and ³¹P{¹H} NMR spectroscopy

indicated a complete regeneration of 10.

Suzuki-Miyaura Cross-Coupling. A General Procedure. A

reaction vessel was charged with palladium(II) acetate (1 mg, 5

µmol), the phosphine ligand (6 µmol; if appropriate), potassium

carbonate (276 mg, 2 mmol), phenylboronic acid (146 mg, 1.2

mmol), and 4-bromotoluene (171 mg, 1.0 mmol), ﬂushed with

argon, and sealed with a rubber septum. Then, solvent was

introduced (5 mL), and the mixture was transferred to an oil bath

preheated to 80 °C and stirred at this temperature for the given

reaction time. Conversion was monitored by withdrawing small

aliquots and recording ¹H NMR spectra. The samples from organic

solvents were ﬁltered through a 0.45 µm PTFE syringe ﬁlter and

diluted with CDCl₃. Samples from experiments in aqueous media

were extracted into diethyl ether, and the extract was dried (MgSO₄),

ﬁltered, and diluted with CDCl₃. In cases of complete conversion,

the reaction mixture was extracted with diethyl ether, and the extract

was dried (MgSO₄) and passed through a short silica column, eluting

with hexane/ethyl acetate (1:1 v/v). Subsequent evaporation afforded

analytically pure 13 as a white solid. The compound was character-

ized by a comparison with an authentic sample.

X-ray Crystallography. Crystals suitable for single-crystal X-ray

diffraction analysis were grown from ethyl acetate/hexane (2: orange

block, 0.35 × 0.58 × 0.60 mm³; 3: orange prism, 0.08 × 0.24 ×

0.36 mm³; 6: orange bar, 0.15 × 0.18 × 0.55 mm³; 12: orange

block, 0.22 × 0.27 × 0.48 mm³), toluene/hexane (4: orange prism,

0.37 × 0.45 × 0.62 mm³), acetone/diethyl ether (10: orange bar,

0.08 × 0.10 × 0.40 mm³), and from acetonitrile/diethyl ether (11:

orange block, 0.13 × 0.30 × 0.33 mm³). Crystals of 9 were grown

from acetic acid/diethyl ether; 9a resulted by recrystallization of 9

from chloroform/diethyl ether (9: orange plate, 0.03 × 0.15 × 0.20

mm³; 9a: orange plate, 0.03 × 0.25 × 0.55 mm³).

routines incorporated in the diffractometer software; the ranges of

transmission factors (TF) are given in Table 9.

The structures were solved by direct methods (SIR97⁴⁶) and

reﬁned by full-matrix least-squares on F²(SHELXL97⁴⁷). Non-

hydrogen atoms were reﬁned with anisotropic thermal motion

parameters. Amide hydrogens were identiﬁed on the difference

electron density maps and reﬁned freely (2, 3, 11) or as a riding

atoms (4, 6, 10, 9, 9a). Other hydrogen atoms were included in the

calculated positions and reﬁned as riding atoms with U_iso(H)

assigned to a multiple of U_eqof their bonding atom.

Particular comments on structure reﬁnement are as follows: The

large residual electron density can be explained by statistical

disorder of the phosphinylated cyclopentadienyl ring, C₅H₄PPh₂.

The largest positive difference electron density peak attributable

to the P atom in the less populated orientation lies in the plane of

the cyclopentadienyl ring and has a similar distance from Fe as

the major component. Reﬁnement over two positions proved

impossible due to low abundance of the less populated orientation

and overlaps. Complex 10 crystallizes with the symmetry of the

chiral space group Pca2₁but as a racemic twin. The contributions

of the enantiomeric cells reﬁned to 0.27:0.73. Finally, the perchlo-

rate anion in the structure of 11 is partly disordered and was

modeled with its Cl, O(4), and O(5) atoms as invariant pivots and

with two positions for each O(6) and O(7).

Relevant crystallographic data are given in Table 9. Geometric

parameters and structural drawings were obtained with a recent

version of the Platon program.⁴⁸All calculated values are rounded

with respect to their estimated standard deviations (esd’s) given

with one decimal; parameters involving atoms in constrained

positions (typically hydrogens) are given without esd’s. CCDC

723117-723125 contain the supplementary crystallographic data

for this paper. These data can be obtained free of charge from The

Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/

data_request/cif.

Acknowledgment. This work is a part of the long-term

research project supported by the Ministry of Education,

Youth and Sports of the Czech Republic (project nos.

MSM0021620857 and LC06070).

Supporting Information Available: Alternative views of the

molecular structures of 9 and 9a and overlaps of the crystallo-

graphically independent molecules for complexes 10 and 12. This

materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.

Full-set diffraction data ((h, (k, (l) of 3 were collected on an

Oxford Diffraction XCalibur 2 diffractometer with Sapphire 2 CCD

detector equipped with an Oxford Instruments Cryojet HT Cooler

(Oxford Cryosystems). The data for all other compounds were

collected with a Nonius KappaCCD diffractometer equipped with

a Cryostream Cooler (Oxford Cryosystems). All measurements were

performed at 150(2) K using graphite-monochromatized Mo KR

radiation (λ ) 0.71073 Å). When appropriate, the intensity data

were corrected for absorption by using the absorption correction

OM900209J

(46) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;

Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,

R. J. Appl. Crystallogr. 1999, 32, 115.

(47) Sheldrick, G. M. SHELXL97. Program for Crystal Structure

Reﬁnement from Diffraction Data; University of Goettingen: Germany, 1997.

(48) (a) Spek, A. L. PlatonsA Multipurpose Crystallographic Tool;

Utrecht University: Utrecht, The Netherlands, 2007. For a reference, see:

(b) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.

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