Synthesis, structural characterization, and catalytic evaluation of palladium complexes with homologous ferrocene-based pyridylphosphine ligands

DOI: 10.1021/om100339p

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Organometallics p. 3187 - 3200 (2010)

Update date:2022-09-26

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Authors:

Stepnicka, Petr

Schulz, Jiri

Klemann, Thorsten

Siemeling, Ulrich

Cisarova, Ivana

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Article abstract of DOI:10.1021/om100339p

A ferrocene-based phosphinopyridine, Ph₂PfcPy (1; fc = ferrocene-1,1'-diyl, Py = 2-pyridyl), was newly synthesized by Negishi coupling of Ph2PfcZnCl with PyBr. Its homologous compound Ph₂PfcCH ₂Py (2) was obtained by reductive dehydroxylation of Ph ₂PfcCH(OH)Py (4), the latter resulting via reaction of in situ generated Ph2PfcLi with PyCHO. Depending on the stoichiometry, compounds 1 and 2 react with [PdCl₂(cod)] (cod = η²:η²- cycloocta-1,5-diene) to give P,N-chelate and bis-phosphine complexes, [PdCl ₂(L-?²P,N)] (5, L = 1;6, L = 2) and [PdCl ₂(L-?P)₂] (7, L = 1;8, L = 2), respectively. Analogously, [(L^NC)PdCl]₂ or [(L^NC)Pd(MeCN) ₂]ClO₄ (L^NC = [(2-dimethylamino-?N)methyl] phenyl-?C¹) react with 1 and 2 to afford complexes featuring these compounds as P-monodentate ligands ([(L^NC)PdCl(L-?P)]: 9, L = 1;10, L = 2) or P,N-chelating donors ([(L^NC)Pd(L-?²P,N)]ClO ₄: 11, L = 1;12, L = 2), respectively. With the exception of compound 9, which undergoes self-ionization in solution, all complexes are defined air-stable solids and were characterized by elemental analysis and conventional spectroscopic methods (multinuclear NMR, IR, and MS). The crystal structures of 4, 5, 7 3 CH₂Cl₂, 8, 11, and 12 were determined by X-ray crystallography, revealing structural differences resulting from a more flexible geometry of the methylene-spaced ligand 2. The catalytic potential of the Pd complexes 5 and 6 and their in situ generated counterparts (Pd(OAc) ₂/L, L = 1, 2) was studied in Suzuki-Miyaura cross-coupling of 4-bromotoluene (13) with phenylboronic acid and in cyanation of the same substrate with K₄[Fe-(CN)₆]. The results were compared with those obtained under identical conditions with analogous catalysts based on the related donor-symmetric ligand 1,1'-bis(diphenylphosphino)ferrocene.

Full text of DOI:10.1021/om100339p

Organometallics 2010, 29, 3187–3200 3187

DOI: 10.1021/om100339p

Synthesis, Structural Characterization, and Catalytic Evaluation

of Palladium Complexes with Homologous Ferrocene-Based

Pyridylphosphine Ligands

,†

Petr Stepnicka,* Jirı

Schulz,^†Thorsten Klemann,^‡Ulrich Siemeling,^‡and Ivana Cı

ꢀ

ꢁ^†

sarova

ꢀ

^†Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030,

CZ-12840 Prague 2, Czech Republic, and Institute of Chemistry, University of Kassel,

‡

Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany

Received April 23, 2010

A ferrocene-based phosphinopyridine, Ph₂PfcPy (1; fc = ferrocene-1,1⁰-diyl, Py = 2-pyridyl), was

newly synthesized by Negishi coupling of Ph₂PfcZnCl with PyBr. Its homologous compound

Ph₂PfcCH₂Py (2) was obtained by reductive dehydroxylation of Ph₂PfcCH(OH)Py (4), the latter

resulting via reaction of in situ generated Ph₂PfcLi with PyCHO. Depending on the stoichiometry,

compounds 1 and 2 react with [PdCl₂(cod)] (cod = η²:η²-cycloocta-1,5-diene) to give P,N-chelate

and bis-phosphine complexes, [PdCl₂(L-κ²P,N)] (5, L = 1; 6, L = 2) and [PdCl₂(L-κP)₂] (7, L = 1; 8,

L = 2), respectively. Analogously, [(L^NC)PdCl]₂or [(L^NC)Pd(MeCN)₂]ClO₄(L^NC= [(2-dimethyl-

amino-κN)methyl]phenyl-κC¹) react with 1 and 2 to afford complexes featuring these compounds

as P-monodentate ligands ([(L^NC)PdCl(L-κP)]: 9, L = 1; 10, L = 2) or P,N-chelating donors

([(L^NC)Pd(L-κ²P,N)]ClO₄: 11, L = 1; 12, L = 2), respectively. With the exception of compound 9,

which undergoes self-ionization in solution, all complexes are defined air-stable solids and were

characterized by elemental analysis and conventional spectroscopic methods (multinuclear NMR,

IR, and MS). The crystal structures of 4, 5, 7 CH₂Cl₂, 8, 11, and 12 were determined by X-ray

crystallography, revealing structural differences resulting from a more flexible geometry of the

methylene-spaced ligand 2. The catalytic potential of the Pd complexes 5 and 6 and their in situ

generated counterparts (Pd(OAc)₂/L, L = 1, 2) was studied in Suzuki-Miyaura cross-coupling of

4-bromotoluene (13) with phenylboronic acid and in cyanation of the same substrate with K₄[Fe-

(CN)₆]. The results were compared with those obtained under identical conditions with analogous

catalysts based on the related donor-symmetric ligand 1,1⁰-bis(diphenylphosphino)ferrocene.

Introduction

patterns of the donor groups. In addition, the specific com-

bination of hard and soft donor atoms³makes these com-

pounds typical examples of hybrid ligands and may result in

hemilabile coordination.²

The intrinsic attractiveness of P,N-donors naturally led

to the design of ferrocene-based ligands of this kind.⁴

Phosphinylated N-heterocycles, particularly pyridylpho-

sphines, are highly versatile ligands finding use in coordina-

tion chemistry and catalysis.^1,2This is largely because the

properties of these donors can be tuned over a wide range via

changing the organic scaffold and the nature and substitution

*To whom correspondence should be addressed. E-mail: stepnic@

natur.cuni.cz.

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Chiral 1,2-Disubstituted Ferrocene Diphosphines for Asymmetric Catalysis.

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2067. (b) Espinet, P.; Soulantica, K. Coord. Chem. Rev. 1999, 193-195,

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In Ferrocenes: Ligands, Materials and Biomolecules; Stepnicka, P., Ed.;

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(g) Hayashi, T.; Sawamura, M.; Ito, Y. Tetrahedron 1992, 48, 1999.

(h) Burckhardt, U.; Hintermann, L.; Schnyder, A.; Togni, A. Organometal-

lics 1995, 14, 5415. (i) Ireland, T.; Perea, J. J. A.; Knochel, P. Angew. Chem.,

(4) For overviews of the chemistry of ferrocene ligands, see:

ꢀ

(a) Ferrocenes: Ligands, Materials and Biomolecules; Stepnicka, P., Ed.;

Wiley: Chichester, U.K., 2008. (b) Ferrocenes: Homogeneous Catalysis,

Organic Synthesis, Materials Science; Togni, A., Hayashi, T., Eds.; VCH:

Weinheim, Germany, 1995. (c) Richards, C. J.; Locke, A. J. Tetrahedron:

Asymmetry 1998, 9, 2377. (d) Atkinson, R. C. J.; Gibson, V. C.; Long, N. J.

Chem. Soc. Rev. 2004, 33, 313. (e) Siemeling, U.; Auch, T.-C. Chem. Soc.

ꢀ

ꢀꢁ

ꢁ

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Int. Ed. 1999, 38, 1457. (j) Gotov, B.; Toma, S.; Solcaniova, E.; Cvengros, J.

Tetrahedron 2000, 56, 671. (k) Hu, X.; Chen, H.; Dai, H.; Hu, X.; Zheng, Z.

Tetrahedron: Asymmetry 2003, 14, 2073. (l) Hu, X.; Dai, H.; Bai, C.; Chen,

H.; Zheng, Z. Tetrahedron: Asymmetry 2004, 15, 1065. (m) Hu, X.-P.;

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2010 American Chemical Society

Published on Web 06/22/2010

pubs.acs.org/Organometallics

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Stepnicka et al.

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3188 Organometallics, Vol. 29, No. 14, 2010

Scheme 1

Scheme 1), its 1,2-isomer (I),⁹and other 1⁰-(diphenylphos-

phino)-1-(heteroaryl)ferrocenes II-IV (Scheme 1)¹⁰were

reported by Butler already in the 1990s. This author and

co-workers also demonstrated that compound II coordinates

to palladium as a unique trans-spanning, donor-unsymme-

tric ligand.¹¹Tani el al. utilized 1 in the synthesis of the bis-

chelate complex [Rh(cod)(1-κ²N,P)]PF₆(cod = η²:η²-cyclo-

octa-1,5-diene), featuring a Rh H-C interaction,¹²which

3 3 3

later became the subject of a quantum-chemical study.¹³The

same group also showed that the analogous Ir complex has a

different structure, resulting via oxidative addition of a

pyridine C-H bond across the metal center.¹²

Stimulated by the lack of any recent information on

phosphinoferrocene heterocycles¹⁴and our results on the

related amidophosphine ligands Ph₂PfcCONH(CH₂)_nPy

(n = 1, 2),¹⁵we decided to explore the coordination and

catalytic chemistry of 1 and the related donors. In this

contribution, we report an improved synthesis of ligand 1

and the preparation of its homologous compound Ph₂Pfc-

CH₂Py (2). Also reported are the preparation and structural

characterization of a series of palladium(II) complexes with

these phosphinopyridines and their utilization in palladium-

catalyzed C-C bond forming reactions.

Results and Discussion

Preparation and Characterization of Ligands 1 and 2.

Although the synthesis of donor 1 has been already reported,⁹

we sought for a different synthetic approach in order to devise

an alternative to the original low-yielding procedure based on

the direct reaction of pyridine with 1⁰-(diphenylphosphino)-1-

lithioferrocene. Thus, compound 1 was synthesized (Scheme 2)

via Pd-catalyzed Negishi cross-coupling¹⁶of 2-bromopyridine

(PyBr) with 1⁰-(diphenylphosphino)-1-(chlorozinc)ferrocene,

the latter being generated in situ by lithiation of 1⁰-(diphenyl-

phosphino)-1-bromoferrocene (3)¹⁷and subsequent transme-

talation with [ZnCl₂(1,4-dioxane)]. This method gave 1 repro-

ducibly and in an improved yield of ca. 50%.

The combination of a ferrocene scaffold with P- and N-donor

moieties is particularly appealing, since the ferrocene unit is

not only an electron-rich, redox-active organometallic moi-

ety but, owing to its defined geometry and conformational

flexibility, can serve as a sort of molecular hinge, assisting in

preorganization of the donor atoms prior to coordination.

Among the ferrocene P,N-ligands reported to date, chiral P,

N-donors derived from N,N-dimethyl-1-ferrocenylethyl-

amine^4,5and phosphinoferrocene oxazolines^4,6are especially

worth mentioning due to their numerous successful applica-

tions in catalysis.

In contrast, the archetypal representatives of ferrocene

P,N-donors such as simple phosphinoferrocene amines⁷

and N-heterocycles⁸have been studied considerably less.

Thus, Ph₂PfcPy (1; fc = ferrocene-1,1⁰-diyl, Py = 2-pyridyl;

(10) Butler, I. R. Polyhedron 1992, 11, 3117.

(11) Butler, I. R.; Kalaji, M.; Nehrlich, L.; Hursthouse, M.; Karau-

lov, A. I.; Malik, K. M. A. J. Chem. Soc., Chem. Commun. 1995, 459.

(12) Yoshida, T.; Tani, K.; Yamagata, T.; Tatsuno, Y.; Saito, T.

J. Chem. Soc., Chem. Commun. 1990, 292.

(13) Zhang, Y.; Lewis, J. C.; Bergman, R. G.; Ellman, J. A.; Oldfield,

E. Organometallics 2006, 25, 3515.

(14) This is surprising in view of the rich coordination chemistry and

catalytic applications of “organic” phosphinopyridine donors.^1a-cFor

recent examples of their catalytic use, see: (a) Yang, H.; Gao, H.;

Angelici, R. J. Organometallics 2000, 19, 622. (b) Chen, H.-P.; Liu,

Y.-H.; Peng, S.-M.; Liu, S.-T. Organometallics 2003, 22, 4893. (c) Speiser,

F.; Braunstein, P.; Saussine, L. Organometallics 2004, 23, 2625. (d) Speiser,

F.; Braunstein, P.; Saussine, L. Organometallics 2004, 23, 2633. (e) Oshiki,

T.; Yamashita, H.; Sawada, K.; Utsunomiya, M.; Takahashi, K.; Takai, K.

Organometallics 2005, 24, 6287. (f) Xue, Z.; Lee, B. W.; Noh, S. K.; Lyoo,

W. S. Polymer 2007, 48, 4704. (g) Karam, A.; Tenia, R.; Martínez, M.;

ꢀ

(6) (a) Stepnicka, P.; Lamac, M. Synthesis and Catalytic Use of

ꢀ

Planar Chiral and Polydentate Ferrocene Donors. In Ferrocenes: Li-

ꢀ

gands, Materials and Biomolecules; Stepnicka, P., Ed.; Wiley: Chichester,

U.K., 2008; Chapter 7, p 237. (b) Sutcliffe, O. B.; Bryce, M. R. Tetrahedron:

Asymmetry 2003, 14, 2297.

(7) Ph₂PfcNH₂: (a) Butler, I. R.; Quayle, S. C. J. Organomet. Chem.

1998, 552, 63. Ph₂PfcCH₂N(R)Me (R = Me, (R)-CH(Me)Ph): (b) Wright,

M. E. Organometallics 1990, 9, 853.

(8) Representative examples are as follows. Pyrrolidinyl-phosphines:

(a) Ganter, C.; Wagner, T. Chem. Ber. 1995, 128, 1157. (b) Farrell, A.;

Goddard, R.; Guiry, P. J. J. Org. Chem. 2002, 67, 4209. N-[m-(Diphenyl-

phosphino)ferrocene-1-yl]-3,5-dihydro-4H-dinapthth[2,1-c:1⁰,2⁰-e]azepines

(m = 1⁰, 2): (c) Widhalm, M.; Nettekoven, U.; Mereiter, K. Tetrahedron:

Asymmetry 1999, 10, 4369. Ferrocenophane phosphine-pyridines: (d) Ekici,

S.; Nieger, M.; Glaum, R.; Niecke, E. Angew. Chem., Int. Ed. 2003, 42, 435.

(e) Chiral pyrrolidine hydrazones: Mino, T.; Segawa, H.; Yamashita, M.

J. Organomet. Chem. 2004, 689, 2833. [3]Ferrocenophane donors:

ꢁ

Lopez-Linares, F.; Albano, C.; Diaz-Barrios, A.; Sanchez, Y.; Catarí, E.;

Casas, E.; Pekerar, S.; Albornoz, A. J. Mol. Catal. A: Chem. 2007, 265, 127.

(h) Grotjahn, D. B.; Kragulj, E. J.; Zeinalipour-Yazdi, C. D.; Miranda-Soto,

V.; Lev, D. A.; Cooksy, A. L. J. Am. Chem. Soc. 2008, 130, 10860.

(i) Flapper, J.; van Leeuwen, P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J.

Organometallics 2009, 28, 3264.

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(f) Liptau, P.; Tebben, L.; Kehr, G.; Frohlich, R.; Erker, G.; Hollmann,

F.; Rieger, B. Eur. J. Org. Chem. 2005, 1909. [Fe{η⁵-C₅H₃(PPh₂-1)(Qn-

2)}(η⁵-C₅H₅)] (Qn = 1-isoquinolin-1-yl, quinolin-8-yl): (g) Kloetzing, R. J.;

Knochel, P. Tetrahedron: Asymmetry 2006, 17, 116. [Fe{η⁵-C₅H₃(PPh₂-

1)(CH(OR)Py-2)}(η⁵-C₅H₅)] (R = Me, CH₂Ph; Py = 2-pyridyl): (h) Chee-

mala, M. N.; Knochel, P. Org. Lett. 2007, 9, 3089. [Fe(η⁵-C₅H₄P(t-Bu)₂)(η⁵-

C₅H_5-nY_n)] (n = 4, 5; Y = pyrid-4-yl or 2,6-dimethylpyrid-4-yl): (i) Oms, O.;

Jarrosson, T.; Tong, L. H.; Vaccaro, A.; Bernardinelli, G.; Williams, A. F.

Chem. Eur. J. 2009, 15, 5012.

(15) (a) Kuhnert, J.; Dusek, M.; Demel, J.; Lang, H.; Stepnicka, P.

ꢀ

€

ꢀ

ꢁ

ꢀ

Dalton Trans. 2007, 2802. (b) K€uhnert, J.; Císarova, I.; Lamac, M.;

ꢀ

Stepnicka, P. Dalton Trans. 2008, 2454.

(16) Mamane, V. Mini-Rev. Org. Chem. 2008, 5, 303.

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(17) (a) Butler, I. R.; Davies, R. L. Synthesis 1996, 1350. (b) Stepnicka,

P. 1⁰-Functionalised Ferrocene Phosphines: Synthesis, Coordination Chemi-

stry and Catalytic Applications. In Ferrocenes: Ligands, Materials and

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Biomolecules; Stepnicka, P., Ed.; Wiley: Chichester, U.K., 2008; Chapter 5,

(9) Butler, I. R. Organometallics 1992, 11, 74.

p 177.

Article

Organometallics, Vol. 29, No. 14, 2010 3189

Scheme 2. Synthesis of the Pyridylphosphine Ligands 1 and 2^a

Figure 1. PLATON plot of the molecular structure of 4. The

displacement ellipsoids correspond to the 30% probability level.

Selected distances and angles(inA anddeg): Fe-Cg1 = 1.640(1),

Fe-Cg2 = 1.642(1), —Cp1,Cp2 = 3.8(1); C6-C11 = 1.509(3),

C11-O = 1.386(3), C11-C12 = 1.531(3), P-C1 = 1.817(2),

P-C17 = 1.836(2), P-C23 = 1.837(2); C6-C11-O = 112.5(2),

C6-C11-C12 = 109.0(2), C-P-C = 100.70(9)-103.83(9).

compounds 2 and 4 were fully characterized by spectroscopic

methods and combustion analysis. In addition, the solid-

state structure of 4 was determined by X-ray crystallo-

graphy. The characterization data for 1, 2, and 4 are rather

unexceptional and corroborate the formulation. Notably,

however, the presence of a stereogenic center makes the

ferrocene CH protons and the phenyl rings in 4 diastereo-

topic, which is reflected by a doubling of the number of the

associated NMR signals.

A view of the molecular structure of 4 is shown in Figure 1

along with selected geometric data. The compound is race-

mic and crystallizes in the triclinic space group P1 with two

inversion-related molecules (enantiomers) per unit cell,

^aPy = pyrid-2-yl.

The synthesis of the homologous ligand 2 (Scheme 2) also

started with bromide 3, which was first converted to

1⁰-(diphenylphosphino)-1-lithioferrocene. Without isolation,

this intermediate was reacted with pyridine-2-carbaldehyde

(PyCHO) to give the secondary alcohol 4 as an ocher solid in

58% yield after aqueous workup and chromatography.¹⁸In

addition, some (diphenylphosphino)ferrocene, resulting from

protonolysis of the lithiated intermediate (28%), and a small

amount of ketone 4a (<1%) were also isolated.¹⁹The sub-

sequent removal of the hydroxyl group from 4 proved a

challenging task, since several conventional methods failed

(e.g., Me₃SiCl/NaI, NaBH₄/CF₃CO₂H, and LiAlH₄/AlCl₃).²⁰

Finally, the dehydroxylation was accomplished by reacting

the alcohol with SmI₂/HMPA and then with pivalic acid as

reported by Kato and Mase for “organic” pyridylmethanols.²¹

This procedure afforded 2 in a satisfactory yield of 55% as an

amber-brown oil, which solidified upon prolonged standing.

Phosphine 1 was identified by a comparison of its spectro-

scopic data with those in the literature;²²the newly prepared

which are interlinked via soft C-H N contacts (Figure 2).

3 3 3

The geometry of the ferrocene unit in 4 is quite regular: the

cyclopentadienyl (Cp) rings are bonded symmetrically (the

difference in Fe-ring centroid distances being 0.002 A), are

practically parallel (tilt angle 3.8(1)ꢀ), and adopt an eclipsed

conformation with the substituents assuming anticlinal posi-

tions (the dihedral angle C1-Cg1-Cg2-C6 is 147ꢀ; cf. the

ideal value of 144ꢀ). The geometry of the functional substitu-

ents compares well with that of [1⁰-(diphenylphosphino)-

ferrocenyl]methanol²³and [Fe{η⁵-C₅H(P(S)Ph₂-1)(CH(OMe)-

Py-2)}(η⁵-C₅H₅)].^8h

Preparation and Characterization of Simple Pd Complexes.

Aiming at a comparison of structural and coordination

properties of 1 and 2, we focused on their complexes with

palladium, which is known to readily coordinate both phos-

phorus and nitrogen donors.²⁴The preparation of the com-

plexes was first attempted starting from [PdCl₂(cod)] (cod =

η²:η²-cycloocta-1,5-diene) at 1:1 and 1:2 metal-to-ligand

ratios (Scheme 3). At the former stoichiometry, both ligands

(18) For the preparation of ferrocenyl(pyrid-2-yl)methanol from

monolithioferrocene and PyCHO, see: Kloetzing, R. J.; Krasovskiy;

Knochel, P. J. Chem. Eur. J. 2007, 13, 215.

(19) Dong and Chang previously reported that a similar reaction of

1-PR₂-1⁰-lithioferrocenes with 6-methylpyridine-2-carbaldehyde affords

1-PR₂-1⁰-[(6-methylpyrid-2-yl)carbonyl]ferrocenes (R = Ph, i-Pr, yields

72-80%; formationof an alcoholwas not noted): (a) Dong, T.-Y.; Chang,

C.-K. J. Chin. Chem. Soc. 1998, 45, 577. The same authors later reported that a

similar reaction with 1-bromo-1⁰-lithioferrocene gives 1-bromo-1⁰-[(6-methyl-

pyrid-2-yl)hydroxymethyl]ferrocene (60% yield): (b) Dong, T.-Y.; Ho, P.-H.;

Chang, C.-K. J. Chin. Chem. Soc. 2000, 47, 421.

(20) Larock, R. C. Comprehensive Organic Transformations, A Guide

to Functional Groups Preparations, 2nd ed.; Wiley-VCH: New York, 1999;

Chapter 1, Section 9, p 44.

(21) Kato, Y.; Mase, T. Tetrahedron Lett. 1999, 40, 8823.

(22) A minor difference was noted in the ¹H NMR data. The original

reference gives δ_H7.97 (dd) for the pyridyl H⁴. We found the same signal

at δ_H7.53 (ddd): i.e., shifted by 0.44 ppm to higher fields.

ꢀ

(23) Stepnicka, P.; Base, T. Inorg. Chem. Commun. 2001, 4, 682.

(24) (a) Hartley, F. R. The Chemistry of Platinum and Palladium;

Applied Science: London, 1973. (b) Barnard, C. J.; Russell, M. J. H.

Palladium. In Comprehensive Coordination Chemistry; Wilkinson, G.,

Gillard, R. D., McCleverty, J. A., Eds.; Pergamon Press: Oxford, U.K.,

1987; Vol. 5, Chapter 51, p 1099. (c) Hutton, A. T.; Morley, C. P.

Palladium(II): Phosphorus Donor Complexes. In Comprehensive Co-

ordination Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;

Pergamon Press: Oxford, U.K., 1987; Vol. 5, Chapter 51.9, p 1157.

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3190 Organometallics, Vol. 29, No. 14, 2010

sequences. Upon going from 1 to 5, the characteristic low-

field signal due to the pyridine H⁶moves by þ0.12 ppm,

while the same coordination shift but in the opposite direc-

tion is detected for H⁶in complex 6. Similar trends are

detected also for the ¹³C NMR signals due to pyridine C²

and CH⁶(data for 5/6: Δδ_C(C²) = -1.0/þ2.0; Δδ_C(CH⁶) =

þ4.3/þ2.5).

The chelate coordination of the P,N-ligands leads to

conformationally locked, C₁-symmetric structures, which

are chiral. As a result, the ferrocene CH groups (and also

the methylene protons in 6) become diastereotopic and

anisochronic. In addition, some resonances due to ferrocene

protons appear markedly shifted from the usual region,

being probably influenced by ring currents of the proximal

aromatic rings (cf. δ_Hranges of the ferrocene protons:

4.63-6.64 and 2.32-5.03 for 5 and 6, respectively). An

additional reason for the remarkable anisochronicity of the

ferrocene protons can be in principle sought in a deformation

of the ferrocene backbone, particularly in tilting of the

cyclopentadienyl rings as observed for, e.g., [3]ferroceno-

phane-like palladium complexes.²⁵However, this does not

appear to be the decisive factor in the present case, because

complex 5 comprising the more tightly embracing ligand 1

shows a tilt of only ca. 6ꢀ in its crystal structure.

Figure 2. View of the hydrogen-bonded dimeric motif in the

structure of 4 (only pivotal phenyl ring carbons are shown for

clarity). Hydrogen-bond parameters: O-H1O N = 126ꢀ,

3 3 3

3.402(3) A. The atoms labeled with a prime are generated by

N = 2.644(3) A; C3-H3 N⁰= 151ꢀ, C3 N⁰=

3 3 3 3 3 3

3 3 3

crystallographic inversion (operation: -x, -y, 1 - z).

Any NMR characterization of 7 and 8 was complicated by

a poor solubility of the crystallized samples. Hence, the spec-

tra were recorded for in situ generated complexes (see the

Experimental Section). As expected, the ³¹P NMR signals of

the bis-phosphine complexes 7 and 8 were found at fields

lower than those of the free ligands (Δδ_P= 33.0 for 7 and

32.4 for 8), whereas the ¹H and ¹³C NMR parameters of the

pyridyl pendants remained similar to those of free ligands (cf.

for 7/8: Δδ_H(H⁶) = 0.06/0.04, Δδ_C(C²) = -0.43/-0.63, and

Δδ_C(CH⁶) = 0.23/-0.38 ppm). In contrast to 5 and 6, the

signals due to ferrocene and phenyl C and CH groups were

observed to be degenerate, indicating conformational flex-

ibility and equivalency of the ligands. Furthermore, the

signals of the Cp^Pand phenyl ring carbons (C_ipsoand all

CH except for phenyl CH_para) in the ¹³C NMR spectra were

seen as apparent triplets arising from the ABX spin systems

¹²C-³¹P(A)-M-³¹P(B)-¹³C(X) (M = metal). Such beha-

vior is typical for bis-phosphine complexes²⁶and was pre-

viously noted also for the related complexes trans-[PdCl₂-

(Ph₂PfcY-κP)₂], where Y = CO₂H,²⁷CONHCH₂Py,^15a

CONHCH₂COMe,²⁸CHdCH₂,²⁹PO₃Et₂.³⁰

Scheme 3. Preparation of Chloropalladium(II) Complexes 5-8

The molecular structure of 5 (Figure 3 and Table 1)

confirms the anticipated P,N-chelate coordination of donor

1. Unlike [PdCl₂{Ph₂Pfc(2,2⁰-bipyrid-6-yl)-κ²P,N}],¹¹how-

ever, complex 5 adopts a cis-P,N geometry, which apparently

reflects a tighter disposition of the donor atoms. The palla-

dium and its four ligating atoms are coplanar within ca.

0.07 A, forming a coordination plane which is void of any

cleanly produced the corresponding chelate complexes [PdCl₂-

(L-κ²N,P)] (5, L = 1; 6, L = 2), whereas the analogous reac-

tions with 2 molar equiv of the ligands afforded the respective

bis-phosphine complexes trans-[PdCl₂(L-κP)₂] (7, L = 1; 8,

L = 2). All complexes were isolated as air-stable solids and

were characterized by spectroscopic methods and by elemental

(25) Metallinos, C.; Tremblay, D.; Barrett, F. B.; Taylor, N. J.

J. Organomet. Chem. 2006, 691, 2044 and references cited therein.

(26) 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.; Springer: Berlin, 1979; Vol. 16,

chapter E, p 65ff and references therein.

analysis. The crystal structures of 5, 7 CH₂Cl₂, and 8 were

determined by X-ray crystallography.

The coordination of phosphorus in complexes 5 and 6 is

clearly manifested in the NMR spectra through a shift of the

phosphorus signals to lower fields (coordination shifts

Δδ_P= 33.2 for 5 and 38.7 for 6) and further by a high-field

shift of the resonance due to ferrocene C-P (Δδ_C= -12.5

ppm for 5 and -7.0 ppm for 6) and a simultaneous increase in

the associated scalar coupling constant ¹J_PC(¹J_PC(complex)/

¹J_PC(ligand) is ca. 7.6 for 5 and ca. 10 for 6). In contrast,

coordination of the pyridyl nitrogen has less obvious con-

ꢀ

ꢀ ꢁ

(27) Podlaha, J.; Stepnicka, P.; Ludvı

tallics 1996, 15, 543.

(28) Tauchman, J.; Cısarova, I.; Stepnicka, P. Organometallics 2009,

28, 3288.

k, J.; Cısarova, I. Organome-

´ ´

ꢀ

ꢁ

ꢀ

ꢀ ꢁ

(29) Stepnicka, P.; Cı

sarova, I. Collect. Czech. Chem. Commun. 2006,

71, 215.

ꢀ

(30) Stepnicka, P.; Cı

ꢀ

ꢀ ꢁ

sarova, I.; Gyepes, R. Eur. J. Inorg. Chem. 2006,

926.

Article

Organometallics, Vol. 29, No. 14, 2010 3191

Figure 3. PLATON plot of the molecular structure of 5 show-

ing the atom-labeling scheme. The displacement ellipsoids en-

close the 30% probability level.

Table 1. Selected Distances (A) and Angles (deg) for Complex 5

Pd-Cl1

Pd-Cl2

Pd-P

2.3638(7)

2.3062(7)

2.2442(7)

2.045(2)

1.654(1)

Fe-Cg2

P-C1

P-C17

P-C23

C6-C12

1.663(1)

1.793(3)

1.820(3)

1.820(2)

1.479(4)

Pd-N

Fe-Cg1

Cl1-Pd-Cl2

Cl1-Pd-N

Cl2-Pd-P

P-Pd-N

91.28(2)

88.44(7)

90.67(2)

89.77(7)

—Cp1,Cp2

5.7(2)

77.1(1)

33.7(2)

82.5(1)

τ^c

Figure 4. PLATON plot of the crystallographically indepen-

dent molecules 1 (a) and 2 (b) in the structure of 7 CH₂Cl₂.The

displacement ellipsoids are drawn at the 30% probability level.

—Cp1,{PdL₄}

—Cp2,Py

C-P-C^b

105.0(1)-107.4(1) —Py,{PdL₄}

^aDefinition of the ring planes: Cp1 = C(1-5), Cp2 = C(6-10),

{PdL₄} = (Pd, Cl1, Cl2, P, N), and Py = {N, C(12-16)}. Cg1 and Cg2

are the centroids of the rings Cp1 and Cp2, respectively. ^bThe range of

C1-P-C(17/23) and C17-P-C23 angles. ^cTorsion angle C1-Cg1-

Cg2-C6.

lengths can be accounted for by a greater trans influence of

the phosphorus atom.³⁶

The chelate coordination of 1 in complex 5 is facilitated by

an inclination of the donor substituents (τ = 17ꢀ; the angle

subtended by the C6-C12/P-C1 bond vectors is 26.3(1)ꢀ)

and is further aided by a rotation of the pyridyl ring along its

pivotal C6-C12 bond (the dihedral angle of the Py ring and

its bonding Cp plane is ca. 34ꢀ). However, such a conforma-

tional change leaves the ferrocene scaffold virtually undis-

torted, as indicated by the perpendicular distances of the

pivotal atoms P and C12 from the planes of their bonding Cp

rings (ca. 0.1 A) and by the relatively minor variation in the

Fe-C bond lengths (2.033(3)-2.066(3) A).

The crystal structures of the bis-phosphine complexes 7

and 8 (Figures 4 and 5, Table 2) share many common

features. Both compounds crystallize with the symmetry of

the triclinic space group P1 so that the Pd atoms reside on the

crystallographic inversion centers (N.B.: compound 7 crys-

significant tetrahedral distortion, as is indicated by the sum

of the interligand angles of 360.2ꢀ. Likewise, the indivi-

dual interligand angles differ only slightly from the ideal

90ꢀ, with the ligand bite angle (P-Pd-N) being 89.77(7)ꢀ.

The Pd-donor distances compare well with those of [PdCl₂-

(dppf-κ²P,P⁰)] CHCl₃(average Pd-Cl = 2.348 A; dppf =

1,1⁰-bis(diphenylphosphino)ferrocene),³¹the bis-phosphine

complexes trans-[PdCl₂(Ph₂PfcX-κP)₂] (Pd-Cl=2.27-2.34

A for X=P(O)Ph₂,³²SiPh₂Bu,³³SMe,³⁴CO₂H,²⁷CONHCH₂-

Py,^15aCONHCH₂COMe,²⁸CHdCH₂,²⁹PO₃Et₂³⁰), and [PdCl-

(Me)(fcPy₂-κ²N,N⁰)] (Pd-N bond trans to Cl: 2.074(4) A).³⁵

The statistically significant difference in the Pd-Cl bond

tallizes as the solvate 7 CH₂Cl₂with two structurally inde-

(31) Hayashi, T.; Konishi, M.; Kobori, Y.; Kumada, M; Higuchi, T.;

Hirotsu, K. J. Am. Chem. Soc. 1984, 106, 158.

(32) Hursthouse, M. B.; Hibbs, D. E.; Butler, I. R. Private commu-

nication to Cambridge Structural Database, 2003 (CSD refcode

GATGAF).

(33) Hursthouse, M. B.; Coles, S. J.; Butler, I. R. Private commu-

nication to Cambridge Structural Database, 2003 (CSD refcode

EKAQUC).

(34) Gibson, V. C.; Long, N. J.; White, A. J. P.; Williams, C. K.;

Williams, D. J.; Fontani, M.; Zanello, P. Dalton Trans. 2002, 3280.

(35) Delis, J. G. P.; van Leeuwen, P. W. N. M.; Vrieze, K.; Veldman,

N.; Spek, A. L.; Fraanje, J.; Goubitz, K. J. Organomet. Chem. 1996, 514,

125.

pendent complex molecules per unit cell). The imposed

symmetry renders the coordination planes {PdCl₂P₂} in 7

and 8 ideally planar and also situates the bulky phosphino-

ferrocene ligands at anti positions, while making their PC₃

moieties mutually staggered as viewed along the P-P⁰direc-

tion. These features were encountered in all structurally

characterized³⁷bis-phosphine complexes featuring achiral

1⁰-functionalized (diphenylphosphino)ferrocenes as P-mono-

dentate donors, [PdCl₂(Ph₂PfcX-κP)₂] (see above), which

(36) (a) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem.

Rev. 1973, 10, 335. (b) Hartley, F. R. The Chemistry of Platinum and

Palladium; Applied Science: London, 1973; Chapter 11, p 299.

(37) According to a search in Cambridge Structural Database, ver-

sion 5.31 of November 2009 with an update of November 2009.

ꢀ

Stepnicka et al.

ꢀ

3192 Organometallics, Vol. 29, No. 14, 2010

Scheme 4. Preparation of (L^NC)Pd Complexes with Ligands

1 and 2

Figure 5. PLATON plot of the molecular structure of 8 show-

ing probability displacement ellipsoids at the 30% probability

level.

Table 2. Selected Distances (A) and Angles (deg) for 7 CH₂Cl₂

and 8^a

NMR data of 10 obtained in CD₂Cl₂solution confirmed

the proposed structure and also suggested a trans-P-NMe₂

relationship via the coupling of the CH₂N(CH₃)₂protons

with phosphorus.³⁹In contrast, NMR spectra of 9 recorded

in the same solvent revealed the presence of two species in an

approximately 1:1.2 molar ratio. Although the exact nature

of these species could not be unequivocally established, we

believe that the solution behavior arises from an equilibrium

between the primary bridge-cleavage product 9 and its

dissociated form 11a (Scheme 5). This explanation is sup-

7 CH₂Cl₂

param

molecule 1

molecule 2

Pd-Cl

2.2994(7)

2.3357(8)

94.36(3)

1.640(2)

1.650(2)

3.6(2)

2.3037(8)

2.3394(8)

86.37(3)

1.651(2)

1.657(2)

3.3(2)

2.3041(4)

2.3490(4)

88.11(2)

1.6531(7)

1.6559(8)

2.2(1)

Pd-P

Cl-Pd-P^b

Fe-Cg^P

Fe-Cg^Py

—Cp^P,Cp^C

τ^c

136

25.7(2)

149

17.1(2)

150

68.0(1)^d

—Py,Cp^C

ported mainly by NMR data. In the H NMR spectrum,

complex 9 (the minor component) displays four ferrocene

resonances and its pyridine CH⁶proton is found at a

relatively high field (cf. δ_H(H⁶) in CD₂Cl₂: 8.25 for 9, 8.43

for 1 and 8.98 for 11). On the other hand, the major

component, presumably 11a, gives rise to eight well-sepa-

rated ferrocene signals (some of them at very low fields; cf.

data for 11), two doublets for CH₂Py, and a pair of double

doublets for the CH₂N protons, as would be expected when

these protons become diastereotopic due to a fixed chelate

geometry (cf. the data for 5 and 11). The resonance of pyr-

idine CH⁶in 11a is found shifted to lower field (δ_H8.92).

Moreover, the involvement of a dissociation process is in line

with a strong solvent dependence of the equilibrium (Figure 6)

and also with the observation that the NMR spectra re-

corded in CD₃CN as a donor solvent suggested an additional

species to be present, most likely a solvento complex.

^aDefinition of the ring planes: Cp^Pand Cp^Cdenote Ph₂P- and

“pyridyl”-substituted Cp rings, respectively. Cg^Pand Cg^Cstand for

the respective ring centroids. ^bThe sum of the complementary Cl-Pd-P

and Cl-Pd-P⁰angles is 180ꢀ due to imposed symmetry. ^cTorsion angle

C1-Cg^P-Cg^C-C6 for 7 CH₂Cl₂, molecule 1 and analogously for all

others. ^dAngle subtended by the C11-C12 bond and Cp^pplane is

67.7(1)ꢀ.

also exhibited similar Pd-donor distances and interligand

angles (Pd-Cl = 2.27-2.34 A, Pd-P = 2.33-2.36 A;

Cl-Pd-P = 86.2-89.9ꢀ³⁸).

The ferrocene units in 7 and 8 show tilts below 4ꢀ and

negligible variation in the Fe-C bond lengths (ca. 0.02 A). In

comparison to 5, the Cp rings in the bis-phosphine com-

plexes assume sterically more relaxed conformations close to

eclipsed anticlinal (ideal τ = 144ꢀ), while the uncoordinated

pyridyl pendants are directed away from the coordination

plane (for 8 also away from the ferrocene unit).

NMR data for the cationic bis-chelates 11 and 12 are

in accordance with the formulation, suggesting a trans-

P-NMe₂configuration to be present. Similarly to 5 and 6,

the constrained geometry of 11 and 12 results in chirality of

the ferrocene units and makes the ferrocene and phenyl CH

Preparation of and Structural Characterization of (L^NC)Pd

Complexes. Reaction of [(L^NC)PdCl]₂(L^NC= [(2-dimethyl-

amino-κN)methyl]phenyl-κC¹) with 2 molar equiv of 1 or 2 in

CH₂Cl₂(Scheme 4) yielded the corresponding bridge-clea-

vage products “[(L^NC)PdCl(L-κP)]” (9, L = 1; 10, L = 2). A

similar reaction with the preformed solvento complex

[(L^NC)Pd(MeCN)₂]ClO₄at a 1:1 molar ratio gave the re-

spective cationic bis-chelate complexes 11 and 12 (Scheme 4).

(39) For NMR data of (L^NC)Pd complexes with phosphinoferro-

cenes, see: (a) Ma, J.-M; Yamamoto, Y. Inorg. Chim. Acta 2000, 299,

ꢀ

ꢀ ꢁ

164. (b) Stepnicka, P.; Císarova, I. Organometallics 2003, 22, 1728.

ꢀ

ꢁ

ꢀ

Lamac, M.; Císarova, I. Polyhedron 2004, 23, 921. (e) Stepnicka, P.;

Císarova, I. Inorg. Chem. 2006, 45, 8785. (f) Stepnicka, P.; Krupa, M.;

ꢀ

ꢁ

ꢀ

(38) P-Pd-Cl or P-Pd-Cl⁰depending on the choice of the crystal-

lographically independent part.

Lamac, M.; Císarova, I. J. Organomet. Chem. 2009, 694, 2987. See also

refs 27 and 28.

ꢀ

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Article

Organometallics, Vol. 29, No. 14, 2010 3193

Figure 6. ¹H NMR spectra of complex [(L^NC)PdCl(1)] (9) in the

region of pyridine H-6 protons as recorded in different solvents.

The arrow indicates the position of the resonance due to H-6

in 11.

Figure 7. PLATON plot of the cation in the structure of 11

showing the atom-labeling scheme and displacement ellipsoids

at the 30% probability level.

Scheme 5

groups, methylene protons, and NMe₂methyls diastereoto-

pic, while the ring currents further differentiate these signals.

Also in analogy with the simple chelate complexes, the P,N-

coordination of 1 is manifested by a shift of the pyridine H⁶

signal to lower fields (cf. δ_H(H⁶): 8.43 for 1 and 8.98 for 11),

whereas the position of this signal in 2 varies only marginally in

the series comprising free 2 (δ_H8.44) and complexes 10 (δ_H

8.46) and 12 (Δδ_H8.38). ESI mass spectra of 11 and 12 display

exclusively the cations [(L^NC)Pd(L)]^þ(L = 1, 2). The pre-

sence of the perchlorate counterion is evidenced by IR spectra,

mainly by the strong composite ν₃band at ca. 1090 cm^{-1 40}

Figure 8. PLATON plot of the cation in the crystal structure of

12. Displacement ellipsoids correspond to the 30% probability

level.

The crystal structures of complexes 11 and 12 (Figures 7

and 8 and Table 3) were determined, allowing for a structural

comparison of the homologous pyridylphosphine ligands. In

both cases, the coordination environments of the palladium

atoms are severely distorted from the regular square, reflect-

ing both steric crowding and unlike Pd-donor bond lengths.

Nonetheless, the individual Pd-donor distances in 11 and 12

do not depart much from those reported for the related com-

plexes [(μ-dppf){(L^NC)PdCl}₂],^39a[(L^NC)PdCl(L-κP)] (L =

Ph₂PfcCHdCH₂,²⁹Ph₂PfcCONHCH₂CO₂Me²⁸), [(L^NC)Pd-

(CH₃CN-κN)(Ph₂PfcCO₂Me-κP)]ClO₄,^39dand [(L^NC)PdCl-

(Ph₂PfcCONHCH₂CO₂Me-κ²P,O)]ClO₄.²⁸

The C29-Pd-N2 angles in 11 and 12 are the most acute

among interligand angles and are quite similar. In contrast,

the bite angles of the chelating ferrocene ligands, P-Pd-N1,

are considerably more opened and also differ in the pair.

Whereas the angle constituted by ligand 1 in complex 11 is ca.

99ꢀ, the same parameter in 12 approaches the ideal value of

90ꢀ (ca. 92ꢀ). A lower flexibility of 1 as compared with 2 is

further manifested by a more pronounced distortion of the

coordination environment in 11 (cf. the maximum deviations

of the plane-defining atoms from the PdL₄least-squares

plane: 0.193(3) A for 11 and 0.105(1) A for 12) and by a

higher mutual rotation of the PdL4 and Cp1 planes (the

dihedral angles are 59.8(2) and 36.3(1)ꢀ for 11 and 12,

(40) Nakamoto, K. Infrared and Raman Spectra of Inorganic and

Coordination Compounds, Part A: Theory and Applications in Inorganic

Chemistry, 5th ed.; Wiley: New York, 1997; Section II, Chapter II-6, p 189,

and Chapter II-8, p 214.

ꢀ

Stepnicka et al.

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3194 Organometallics, Vol. 29, No. 14, 2010

Scheme 6. Reaction of 10 with in Situ Generated (Ph₃P)Au^þ

Table 3. Selected Distances (A) and Angles (deg) for Complexes

11 and 12^a

param

Pd-P

2.2571(9)

2.174(3)

2.166(3)

2.013(3)

99.13(8)

91.8(1)

89.2(1)

81.5(1)

59.8(2)

1.802(4)-1.831(3)

100.1(2)-108.8(2)

1.636(2)

1.639(2)

3.1(2)

2.2491(7)

2.142(2)

2.138(2)

2.032(2)

91.90(6)

94.41(8)

91.07(7)

81.93(9)

36.3(1)

1.805(2)-1.832(3)

101.1(1)-110.3(1)

1.653(1)

1.662(2)

2.9(2)

Pd-N1

Pd-N2

Pd-C29

P-Pd-N1

P-Pd-C29

N1-Pd-N2

N2-Pd-C29

—PdL₄,Cp1

P-C^b

C-P-C^c

Fe-Cg1

Fe-Cg2

—Cp1,Cp2

34.2(2)

108.7(3)

0.478(3)

36.0(4)

65.6(2)^e

108.4(2)

0.416(2)

40.4(3)

—Py,Cp2

N2-C35-C30

Q_ring

j_ring

^aThe ring planes, ring centroids, and τ angle parameters are defined

as for 4 (PdL₄= {Pd,P,N1,N2,C29}). See footnotes to Table 1. ^bThe

range of the P-C(1,17,23) bond lengths. ^cThe range of the C1-P-C-

(17,23) and C17-P-C23 angles. ^dRing puckering parameters for the

ring {Pd, C29, C30, C35, N2}: Q_ring= total puckering amplitude in A;

abstraction of the chloride ligand took place, regenerating

[(Ph₃P)AuCl] with formation of complex 12a (Scheme 6).

Compound 12a separated as a rusty orange crystalline solid

upon addition of diethyl ether (81% isolated yield) and was

structurally characterized.⁴³Solution NMR data of 12a

matched very well those of 12 (maximum difference in the

¹H spectrum is 0.04 ppm for H⁶; the ³¹P NMR shifts of 12

_ring= phase angle in deg. An ideal envelope requires j_ring= k ꢀ 36ꢀ.

^eThe angle subtended by the Cp2 plane and the C11-C12 bond is

43.7(2)ꢀ.

respectively). It also affects the coordination of the pyridyl

nitrogen, as indicated by the angles subtended by the Pd-N1

bonds and the Py planes being 16.4(1)ꢀ for in 11 and 7.0(1)ꢀ in

12. On the other hand, the (L^NC)Pd rings assume similar

envelope conformations (cf. the ring puckering parameters⁴¹

in Table 3), in which the N2 atoms are displaced from the

“plane” of the remaining ring atoms.

Reactivity Studies with Complex 10. In order to study the

reactivity of the uncoordinated nitrogen atom, several alky-

lation, protonation, and metalation reactions were carried

out following the H^þ, CH₃^þ, Ph₃PAu^þisolobal relationship.

The reactions were performed on an NMR scale with com-

pound 10, which was chosen mainly because of its high

solubility and stability in a solution.

The reaction of 10 with 1 molar equiv of HCl or CF₃CO₂H

led to extensive decomposition (HCl) or yielded a complex

mixture (CF₃CO₂H) probably because of competitive pro-

tonolysis of the Pd-C bonds. On the other hand, the addi-

tion of MeI (4 equiv) left the complex unchanged. A reaction

of 10 with in situ generated [(Ph₃P)Au]SbF₆did not yield

any ligand-bridged Au-Pd complex either.⁴²Instead, an

and 12a differ by 0.2 ppm), whereas the presence of a SbF₆

anion was corroborated by IR (ν₃band at 658 cm^{-1 40}

and

)

by mass spectra (m/z 234/236 in ESI-). The residue obtained

after evaporation of the mother liquor from crystallization

was analyzed as essentially pure [(Ph₃P)AuCl].

Catalytic Tests. Catalytic properties of ligands 1 and 2

were evaluated in practically relevant Pd-catalyzed C-C

bond forming reactions, namely in Suzuki-Miyaura aryla-

tion⁴⁴and cyanation⁴⁵of 4-bromotoluene (13) as a deacti-

vated model substrate. For the sake of comparison, the

experiments were performed simultaneously with both phos-

phinopyridine donors and with dppf as the exemplary and

very successful ferrocene ligand.⁴⁶[PdCl₂(L)] (L = 1, 2,

dppf) were used as defined catalyst precursors and compared

to precatalysts generated in situ by mixing palladium(II)

acetate with the appropriate ligand.

The Suzuki-Miyaura cross-coupling of 13 with phenyl-

boronic acid to give 4-methylbiphenyl (14) (Scheme 7) was

carried out in 1,4-dioxane at 80 ꢀC using 0.5 or 0.25 mol %

palladium catalyst and potassium carbonate as the base. The

results (Table 4) indicate that both the defined and in situ

(41) (a) Ring puckering analysis may be dubious due to different in-

ring bond lengths. However, the parameters describe the same moieties

and only their trends are compared. For a reference, see: (b) Cremer, D.;

Pople, J. A. J. Am. Chem. Soc. 1975, 97, 1354.

(44) 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, Germany, 2004; Vol. 1, Chapter 2, p 41.

(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.

(45) (a) Sundermeier, M.; Zapf, A.; Beller, M. Eur. J. Inorg. Chem.

2003, 3513. (b) Ellis, G. P.; Romney-Alexander, T. M. Chem. Rev. 1987, 87,

779.

(42) For preparation of [Ph₃PAu(pyridine-κN)]BF₄, see: Thwaite,

S. E.; Schier, A.; Schmidbaur, H. Inorg. Chim. Acta 2004, 357, 1549.

(43) The crystal structure of 12a is very similar to that of 12, including

the disorder of the anion. Crystallographic data for 12a are as follows:

C₃₇H₃₆F₆FeN₂PPdSb (937.65 g mol^-1), monoclinic, C2/c, T = 150(2)

K, a = 24.152(1) A, b = 18.5909(8) A, c = 19.799(1) A, β = 126.225(3)ꢀ,

V = 7171.8(6) A³, Z = 8 (μ = 1.749 mm^-1; corrected for absorption). A

total of 46 292 reflections were measured (θ_max= 27.5ꢀ), from which

8215 were unique and 5601 observed according to the I > 2σ(I) criterion.

Refinementwas carried out as described in the Experimental Section and

converged to R = 4.28% for the observed diffractions and R = 7.93%,

R_w= 9.61% for all diffractions (maximum and minimum residual

electron density ΔF = 1.20, -1.11 e A^-3). The structure was deposited

with the Cambridge Crystallographic Database: CCDC reference no.

771197.

(46) (a) Chien, S. W.; Hor, T. S. A. The Coordination and Homo-

genous Catalytic Chemistry of 1,1⁰-Bis(diphenylphosphino)ferrocene

and its Chalcogenide Derivatives. In Ferrocenes: Ligands, Materials

ꢀ

and Biomolecules; Stepnicka, P.; Ed.; Wiley: Chichester, U.K., 2008;

Chapter 2, p 33. (b) Colacot, T. J. Platinum Met. Rev. 2001, 45, 22.

Coordination Chemistry, Organic Syntheses, and Catalysis. In Ferrocenes:

Homogeneous Catalysis, Organic Synthesis, Materials Science; Togni, A.,

Hayashi, T., Eds.; VCH: Weinheim, Germany, 1995; Chapter 1, p 3.

Article

Organometallics, Vol. 29, No. 14, 2010 3195

Scheme 7. Model Suzuki-Miyaura Cross-Coupling Reaction

Table 4. Catalytic Results for Suzuki-Miyaura Cross-Coupling

Obtained at 0.5 mol % Palladium Loading^a

yield of biphenyl 14 (%)

[PdCl₂(L)]^b

Pd(OAc)₂/L^c

at 80 ꢀC

at 100 ꢀC

t (h)

dppf

100

Figure 9. Kinetic profiles for the model Suzuki-Miyaura reac-

tion catalyzed with defined precatalysts [PdCl₂(L)] (L = dppf

(b), 1 (4), 2 (()) at 0.25 mol % metal loading and 80 ꢀC.

^aThe coupling reactions were performed with 0.5 mol % of palladium

catalyst using 2.0 mmol of 4-bromotoluene (13), 2.2 mmol of phenyl-

boronic acid, and 4.4 mmol of K₂CO₃in 10 mL of dry dioxane. ^bDefined

precatalyst. ^cCatalyst generated in situ.

generated complexes efficiently promote the coupling reac-

tions at 0.5 mol % Pd loading. When performed at 80 ꢀC,

the reactions catalyzed by 0.5 mol % [PdCl₂(L)] proceeded

with similar conversions over time, regardless of the nature

of ligand L. However, raising the reaction temperature to

100 ꢀC led to better conversions and also discriminated the

catalysts. The conversions achieved with [PdCl₂(L)] in-

creased in the following order of ligands L: dppf ≈ 1 < 2.

A similar trend was noted for the in situ generated precata-

lysts (Pd(OAc)₂/L), which also showed a generally higher

activity.

As indicated by the kinetic profiles in Figures 9 and 10, the

coupling reaction proceeded quite well even with 0.25 mol %

Pd catalyst at 80 ꢀC. Yet again, the in situ generated pre-

catalysts afforded faster-reacting systems, with ligand 2 per-

forming best in the series of ligands tested. The trends in

reactivity ([PdCl₂(L)] < Pd(OAc)₂/L and dppf ≈ 1 < 2) can

be attributed to changed electronic properties of the ligands

and the ease of reduction of the metal source to a catalytically

active species.⁴⁷

The palladium-catalyzed cyanation of aryl halides affords

benzonitriles that are both versatile synthetic intermediates

and important commodity chemicals. In comparison with

the Suzuki-Miyaura cross-coupling, the cyanation reaction

still remains less explored and synthetically mastered. In

addition to a CN^-source, a base, and a catalyst, it often

requires the presence of a cocatalyst (e.g., zinc salt) and has

to be performed under relatively harsh conditions (tempera-

ture) to proceed satisfactorily. In our tests (Scheme 8), we

utilized the deactivated substrate 13 and potassium hexa-

cyanoferrate(II)⁴⁸as a safe alternative to the hazardous

inorganic cyanides, Me₃SiCN or Bu₃SnCN.⁴⁵The reactions

were carried out with 0.5 mol % Pd catalyst in N,N-dimethyl-

formamide (DMF) or N-methyl-2-pyrrolidone (NMP) at

130 ꢀC for 16 h (Table 5).

Figure 10. Kinetic profiles for the model Suzuki-Miyaura

reaction catalyzed with Pd(OAc)₂/L (L = dppf (b), 1 (4), 2

(()) at 0.25 mol % metal loading and 80 ꢀC.

In NMP, the overall conversions were high (86-100%)

but the cyanation reaction was accompanied by undesired

reductive dehalogenation of 13 to give toluene. The dppf-

based catalysts [PdCl₂(dppf)] and Pd(OAc)₂/dppf performed

similarly and led to the best conversion to 15. For the

catalysts based on ligands 1 and 2, the defined complexes

gave better results than the Pd(OAc)₂/L mixtures in both the

overall conversion and selectivity. Changing the solvent to

DMF markedly affected the course of the cyanation reac-

tion. With all defined precatalysts [PdCl₂(L)], the reaction

proceeded with complete conversion and selectivity to nitrile

15. The use of the Pd(OAc)₂/L mixtures in DMF ensued in

practically complete overall conversions (100% for dppf,

96% for the pyridylphosphines) and good selectivities to 15

(ca. 90%).

Conclusions

(47) The formation of fine metal particles cannot be ruled out; see:

Astruc, D. Inorg. Chem. 2007, 46, 1884 and references cited therein.

(48) (a) Schareina, T.; Zapf, T.; Beller, M. Chem. Commun. 2004,

1388. (b) Schareina, T.; Zapf, T.; Beller, M. J. Organomet. Chem. 2004, 689,

4576.

The homologous ferrocene pyridylphosphines 1 and 2

have been prepared via an alternative route and newly

synthesized by a combination of conventional synthetic

methods, respectively. These hybrid ligands were found to

ꢀ

Stepnicka et al.

ꢀ

3196 Organometallics, Vol. 29, No. 14, 2010

Scheme 8. Model Cyanation Reaction of Substrate 13

NMR spectra were measured with a Varian Unity Inova

spectrometer (¹H, 399.95 MHz; ¹³C, 100.58 MHz; ³¹P, 161.90

MHz) at 25 ꢀC. Chemical shifts (δ) are given relative to internal

SiMe₄(¹H and ¹³C) 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,

respectively, arising from magnetically nonequivalent protons

in the AA⁰BB⁰and AA⁰BB⁰X spin systems (X = ³¹P) of the

unsymmetrically 1,1⁰-disubstituted ferrocene moiety. Note:

fc = ferrocene-1,1⁰-diyl, Py = 2-pyridyl; Cp^Pand Cp^Cdenote

the phosphinylated and pyridyl-substituted cyclopentadienyl

rings, respectively. IR spectra were recorded with an FT IR

Table 5. Catalytic Results for Pd-Catalyzed Cyanation of

4-Bromotoluene^a

conversion to 15 (%)^b

catalyst

NMP

DMF

Nicolet Magna 650 spectrometer in the range 400-4000 cm^-1

[PdCl₂(dppf)]

[PdCl₂(1)] (5)

[PdCl₂(2)] (6)

Pd(AcO)₂/dppf

Pd(AcO)₂/1

93 (7)

92 (8)

87 (9)

92 (8)

64 (22)

71 (20)

100 (n.d.)

91 (9)

90 (6)

Electrospray ionization (ESI) mass spectra were recorded with

a Bruker Esquire 3000 spectrometer. The samples were dis-

solved in a small amount of a “good” solvent (dichloromethane

or dimethyl sulfoxide) and then diluted with methanol.

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.

Preparation of 1⁰-(Diphenylphosphino)-1-(pyrid-2-yl)ferrocene

(1). Butyllithium (7.5 mL, 1.6 M in hexanes, 12 mmol) was

slowly added to a solution of 1⁰-(diphenylphosphino)-1-bromo-

ferrocene (3; 5.0 g, 11 mmol) in dry THF (40 mL) with stirring

and cooling to ca. -70 ꢀC. After stirring was carried out at this

temperature for 45 min, a solution of [ZnCl₂(1,4-dioxane)] (2.50 g,

11 mmol) in THF (25 mL) was introduced and stirring was

continued at room temperature for 2 h. Then, neat 2-bromopyr-

idine (1.1 mL, 11 mmol) and [Pd(PPh₃)₄] dissolved in THF (108

mg, 0.09 mmol in 5 mL) were added successively, and the

resulting mixture was warmed to 60 ꢀC and stirred at this

temperature for 72 h. Then, the reaction mixture was evaporated

under vacuum, and the residue was dissolved in dichloro-

methane. The solution was washed with water, dried over

Na₂SO₄, and evaporated to dryness. The residue was purified

by column chromatography over neutral alumina first with

hexanes as eluent to remove nonpolar side products and then

with dichloromethane to elute the product. Subsequent eva-

poration gave 1 as a dark orange-brown oil, which crystallized

upon standing. Yield: 2.39 g (48%). Note: The product typically

contains traces of its corresponding phosphine oxide.

Pd(AcO)₂/2

^aConditions: 4-bromotoluene (2.0 mmol), K₄[Fe(CN)₆] (0.5 mmol),

Na₂CO₃(2.0 mmol), and 0.5 mol % of a Pd catalyst in dry solvent (3 mL)

were reacted at 130 ꢀC for 16 h. Conversions were determined by

integration of ¹H NMR signals. NMP = N-methyl-2-pyrrolidone;

DMF = N,N-dimethylformamide. ^bNMR yield of toluene is given in

parentheses; n.d. = toluene not detected.

coordinate to palladium(II) as P-monodentate or P,N-che-

lating donors, depending on the reaction conditions (stoi-

chiometry) and the palladium source. The presence of a

methylene spacer makes compound 2 more flexible as com-

pared with 1, which is naturally reflected in the structures of

palladium complexes with these ligands and may also have

“chemical” consequences such as the tendency toward self-

ionization via closure of the P,N-chelate ring.

Both the defined complexes [PdCl₂(L)] (L = 1, 2) and the

in situ formed precatalysts Pd(OAc)₂/L efficiently promote

Suzuki-Miyaura cross-coupling of 4-bromotoluene with

phenylboronic acid (0.5 of 0.25 mol % Pd), with the latter

systems showing better results. The activities of 2-based

catalysts are similar to or slightly better than those obtained

with the corresponding catalysts based on dppf as the

archetypal donor-symmetric ferrocene ligand. The results

obtained with ligand 1, on the other hand, are comparable to

but slightly worse than those noted for the dppf benchmark.

In contrast, the Pd-catalyzed cyanation of 4-bromotoluene is

better effected by the defined complexes [PdCl₂(L)] (0.5 mol

% Pd), with dppf being a ligand superior to both pyridylpho-

sphines studied.

¹H NMR (CD₂Cl₂): δ 3.94 (vq, J⁰= 1.9 Hz, 2 H), 4.20 (vt,

J⁰= 1.9 Hz, 2 H), 4.25 (vt, J⁰= 2.0 Hz, 2 H), 4.82 (vt, J⁰= 1.9

Hz, 2 H) (4 ꢀ CH of fc), 7.05 (ddd, J = 7.4, 4.8, 1.1 Hz, 1 H, H⁵

of Py), 7.27 (dt, J = 7.9, 1.1 Hz, H³of Py), 7.29-7.38 (m, 10 H,

PPh₂), 7.53 (ddd, J = 7.9, 7.4, 1.8 Hz, H⁴of Py), 8.43 (ddd, J =

4.8, 1.8, 1.0 Hz, H⁶of Py). ¹³C{¹H} NMR (CD₂Cl₂): δ 68.65 (s,

CH of Cp^C), 71.53 (s, CH of Cp^C), 73.30 (d, J_PC= 4 Hz, CH of

Cp^P), 74.55 (d, J_PC= 15 Hz, CH of Cp^P), 77.31 (d, ¹J_PC= 8 Hz,

_ipsoof Cp^P), 85.08 (s, C_ipsoof Cp^C), 120.56 and 121.02 (s, CH^3/5

Experimental Section

of Py), 128.53 (d, ³J_PC= 7 Hz, 4 C, CH_mof PPh₂), 128.86 (s, 2 C,

CH_pof PPh₂), 133.84 (d, J_PC= 20 Hz, 4 C, CH_oof PPh₂),

Materials and Methods. All syntheses were performed under

an argon atmosphere and with exclusion of direct daylight.

1⁰-(Diphenylphosphino)-1-bromoferrocene (3),^17a[PdCl₂(cod)]

(cod = η²:η²-cycloocta-1,5-diene),⁴⁹di-μ-chloro-bis{[(2-di-

methylamino-κN)methyl]phenyl-κC¹}dipalladium(II),⁵⁰bis(ace-

tonitrile-κN){[(2-dimethylamino-κN)methyl]phenyl-κC¹}palla-

dium(II) perchlorate,^39cand chloro(triphenylphosphine)gold(I)⁵¹

were prepared according to literature procedures. Solvents used

in syntheses and catalytic tests were dried over appropriate

drying agents (dichloromethane and chloroform, anhydrous

potassium carbonate; 1,4-dioxane and toluene, sodium; aceto-

nitrile, P₂O₅) and distilled under argon. Other chemicals (Fluka,

Aldrich) and solvents used in crystallizations and chromato-

graphy (Lach-Ner) were used without any further purification.

136.19 (s, CH⁴of Py), 139.63 (d, J_PC= 11 Hz, 2 C, C_ipsoof

PPh₂), 149.60 (s, CH⁶of Py), 158.74 (s, C²of Py). ³¹P{¹H} NMR

(CD₂Cl₂): δ -16.8 (s). ESIþ MS: m/z 448 ([M þ H]^þ), 464 ([MO

þ H]^þ), 470 (dominant, [M þ Na]^þ), 486 ([M þ K]^þor [MO þ

Na]^þ).

Preparation of 1⁰-(Diphenylphosphino)-1-[(pyrid-2-yl)hydro-

xymethyl]ferrocene (4). A solution of bromide 3 (4.49 g, 10.0

mmol) in dry THF (50 mL) was treated with butyllithium

(4.0 mL of 2.5 M in hexanes, 10.0 mmol) with stirring and

cooling to ca. -78 ꢀC (dry ice/ethanol bath). After 15 min, neat

pyridine-2-carboxaldehyde (1.29 g, 12.0 mmol) was added, and

the resulting mixture was stirred at -78 ꢀC for 15 min and then

at room temperature for 90 min. The reaction mixture was

quenched by addition of water and stirring for 30 min and then

extracted with dichloromethane. The extract was washed suc-

cessively with saturated aqueous NaHCO₃and NaCl solutions,

dried over MgSO₄, and evaporated under vacuum. The residue

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

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

(51) Gregory, B. J.; Ingold, C. K. J. Chem. Soc. B 1969, 276.

Article

Organometallics, Vol. 29, No. 14, 2010 3197

was purified by column chromatography on silica gel using a 1:5

ethyl acetate-hexane mixture (v/v) to elute first a yellow band

containing (diphenylphosphino)ferrocene (1.04 g, 28%) and a

following minor red band containing ketone 4a (burgundy red

solid; 27 mg, ca. 0.6%). Then, the mobile phase was changed to

1:1 ethyl acetate-hexane (v/v) to elute alcohol 4, which was

isolated as an ocher solid following evaporation. Yield of 4: 2.78

g (58%).

alcohol 4 elutes as a second band during the chromatography on

alumina.

¹H NMR (CD₂Cl₂): δ 3.63 (s, 2 H, CH₂Py), 3.97 (vt, J⁰= 1.8

Hz, 2 H), 4.05 (vq, J⁰= 1.9 Hz, 2 H), 4.07 and 4.33 (2 ꢀ vt, J⁰=

1.8 Hz, 2 H) (4 ꢀ CH of fc), 7.02 (dt, J = 7.8, 1.1 Hz, 1 H, H³of

Py), 7.06 (ddd, J = 7.4, 4.9, 1.2 Hz, 1 H, H⁵of Py), 7.28-7.40 (m,

10 H, PPh₂), 7.54 (td, J = 7.7, 1.8 Hz, 1 H, H⁴of Py), 8.44 (ddd,

J = 4.9, 2.0, 1.0 Hz, 1 H, H⁶of Py). ¹³C{¹H} NMR (CD₂Cl₂):

δ 38.65 (s, CH₂Py), 69.36 and 70.31 (2 ꢀ CH of Cp^C); 72.18 (d,

Analytical Data for 4. ¹H NMR (CDCl₃): δ 4.01 and 4.04 (2 ꢀ

td, J = 2.4, 1.3 Hz, 1 H), 4.10 (m, 2 H), 4.14 (m, 1 H), 4.20 (dt,

J = 2.5, 1.3 Hz, 1 H) (6 ꢀ CH of fc), 4.21 (br s, 1 H, CHOH), 4.40

and 4.41 (2 ꢀ td, J = 2.4, 1.2 Hz, 1 H, CH of fc); 5.36 (s, 1 H,

CHOH), 7.16 (ddd, J_HH= 7.5, 4.9, 1.2 Hz, 1 H, H⁵of Py), 7.26

(dm, J_HH≈ 8 Hz, 1 H, H³of Py), 7.28-7.41 (m, 10 H, PPh₂), 7.63

(td, J_HH= 7.7, 1.7 Hz, 1 H, H⁴of Py), 8.51 (ddd, J_HH= 4.9, 1.8,

1.0 Hz, 1 H, H⁶of Py). ¹³C{¹H} NMR (CDCl₃): δ 66.79, 68.32,

69.37, 69.33 (4 ꢀ s, CH of Cp^C), 71.21 (s, CHOH), 71.65 and

71.68 (2 ꢀ d, J_PC≈ 5 Hz), 73.39 (d, J_PC= 13 Hz), 73.62 (d,

_PC= 4 Hz), 73.96 (d, J_PC= 15 Hz) (2 ꢀ CH of Cp^P), 76.34 (d,

¹J_PC= 6 Hz, C_ipsoof Cp^P), 87.50 (s, C_ipsoof Cp^C), 121.44 and

122.73 (CH^3/5of Py), 128.48 (d, ³J_PC= 7 Hz, 4 C, CH_mof PPh₂),

128.80 (s, 2 C, CH_pof PPh₂), 133.86 (d, ²J_PC= 20 Hz, 4 C, CH_o

of PPh₂), 136.50 (s, CH⁴of C₅H₄N), 139.92 (d, ¹J_PC= 9 Hz, 2 C,

C_ipsoof PPh₂), 149.43 (s, CH⁶of Py), 161.44 (s, C²of Py).

³¹P{¹H} NMR (CD₂Cl₂): δ -16.5 (s). IR (Nujol): ν/cm^-11589

(s), 1568 (m), 1417 (m), 1318 (w), 1305 (m), 1244 (w), 1226 (w),

1190 (m), 1160 (w), 1147 (w), 1089 (m), 1071 (m), 1048 (m), 1038

(m), 1022 (s), 993 (m), 916 (m), 889 (m), 840 (m), 831 (s), 747 (vs),

700 (vs), 632 (m), 568 (m), 501 (vs), 487 (vs), 451 (s). ESIþ MS:

m/z 462 ([L þ H]^þ), 484 ([L þ Na]^þ). EI MS: m/z (relative

abundance) 462 (26), 461 (70, M^þ³), 277 (100, [M - Ph₂P þ

_PC= 15 Hz) (4 ꢀ CH of Cp^P), 76.22 (d, ¹J_PC= 6 Hz, C_ipsoof

Cp^P), 92.89 (s, C_ipsoof Cp^C), 120.79 and 122.49 (s, CH^3/5of Py),

128.14 (d, 4 C, J_PC= 6 Hz), 128.49 (s), 128.58 (s), 133.48 (vt,

J⁰= 20 Hz, 4 C) (CH of PPh₂), 136.76 (s, CH⁴of Py), 138.77 and

138.95 (2 ꢀ d, ¹J_PC= 9 Hz, C_ipsoof PPh₂), 147.90 (s, CH⁶of Py),

161.02 (s, C²of Py). ³¹P{¹H} NMR (CDCl₃): δ -16.3 (s). IR

(Nujol): ν/cm^-13390-3415 (composite m), 1738 (m), 1592 (s),

1583 (w), 1568 (s), 1308 (m), 1228 (w), 1209 (w), 1188 (w), 1159

(s), 1148 (m), 1095 (m), 1066 (s), 1048 (s), 1024 (s), 988 (m), 886

(m), 839/834 (s), 821 (s), 758 (s), 745 (vs), 707 (s), 699 (s), 636 (m),

624 (w), 530 (m), 507 (s), 496 (s), 486 (s), 458 (s), 421 (w). Anal.

Calcd for C₁₈H₂₄FeNOP (477.3): C, 70.45; H, 5.07; N, 2.94.

Found: C, 70.27; H, 5.18; N, 2.84.

H]^þ), 276 (51), 212 (75, [M - Ph₂P - C₅H₅þ H]^•þ), 211 (12), 210

(18), 134 (14). HR MS: m/z calcd for C₂₈H₂₄⁵⁶FeNP (M^þ

)

461.0996, found 461.1000.

Preparation of Dichloro[1⁰-(diphenylphosphino-KP)-1-(pyrid-

2-yl-KN)ferrocene]palladium(II) (5). [PdCl₂(cod)] (28.5 mg,

0.10 mmol) and 1 (44.5 mg, 0.10 mmol) were mixed with

dichloromethane (2 mL), and the mixture was stirred at room

temperature for 3 h, during which time the product separated as

an orange solid. Pentane (2 mL) was added, and the product was

filtered off, washed with diethyl ether and pentane, and dried

Analytical Data for 4a. ¹H NMR (CDCl₃): δ 4.05 (vq, J⁰= 1.8

Hz, 2 H), 4.30 (vt, J⁰= 1.8 Hz, 2 H), 4.48 and 5.27 (2 ꢀ vt, J⁰=

2.0 Hz, 2 H) (CH of fc), 7.28-7.35 (m, 10 H, PPh₂), 7.44 (ddd,

J = 7.6, 4.8, 1.3 Hz, 1 H, H⁵of Py), 7.83 (td, J = 7.7, 1.8 Hz, 1 H,

H⁴of Py), 8.01 (dt, J = 7.8, 1.1 Hz, 1 H, H³of Py), 8.66 (ddd,

J = 4.8, 1.8, 1.0 Hz, 1 H, H⁶of Py). ¹³C{¹H} NMR (CDCl₃): δ

73.27 (2 C), 73.55 (d, J_PC= 4 Hz, 2 C), 74.42 (d, J_PC= 12 Hz, 2

C), 74.48 (d, J_PC= 3 Hz, 2 C) (CH of fc), 77.62 (C_ipsoof Cp^C),

78.22 (d, ¹J_PC= 9 Hz, C_ipsoof Cp^P), 122.74 and 125.91 (CH^3/5of

under vacuum to give 5 0.2CH₂Cl₂as an orange solid. Yield:

60 mg (96%).

¹H NMR (CD₂Cl₂): δ 4.63 (dq, J = 1.2, 1.2 Hz, 1 H), 4.76,

4.77, and 4.85 (3 ꢀ dt, J = 1.3, 2.6 Hz, 1 H), 4.89 (m, 2 H), 5.81

(m, 1 H), 6.64 (dq, J = 1.3, 1.3 Hz, 1 H) (8 ꢀ CH of fc), 6.76 (ddd,

J = 7.5, 5.9, 1.6 Hz, H of Py), 6.95-7.75 (m, 12 H, PPh₂and 2 H

of Py: δ_Hca. 7.4 and 7.5 according to 2D spectra), 8.55 (dm, J =

5.9 Hz, 1 H, H⁶of Py). ¹³C{¹H} NMR (CD₂Cl₂): δ 64.84 (d,

¹J_PC= 61 Hz, C_ipsoCp^P), 70.47, 71.40, and 73.25 (3 ꢀ CH of

Cp^C), 73.83 (d, J_PC= 3 Hz, CH of Cp^P), 73.96 (d, J_PC= 6 Hz,

CH of Cp^P), 74.46 (CH of Cp^C), 75.01 (d, J_PC= 11 Hz, CH of

Cp^P), 79.07 (d, J_PC= 21 Hz, CH of Cp^P), 91.06 (d, J_PC= 2 Hz,

C_ipsoof Cp^C), 123.69 (CH of Py, δ_H6.76), 128.26 (d, J_PC= 12

Hz, 2 C, CH of PPh₂), 128.81 (d, ¹J_PC= 53 Hz, C_ipsoof PPh₂),

128.83 (d, J_PC= 10 Hz, 2 C, CH of PPh₂), 128.88 (CH of Py, δ_H

Py), 128.17 (d, J_PC= 4 Hz, 4 C, CH_mof PPh₂), 128.59 (2 C,

CH_pof PPh₂), 133.42 (d, J_PC= 20 Hz, 4 C, CH_oof PPh₂),

136.75 (CH⁴of Py), 138.51 (d, ¹J_PC= 10 Hz, 2 C, C_ipsoof PPh₂),

148.41 (CH⁶of Py), 155.87 (C²of Py), 195.78 (CdO). ³¹P{¹H}

NMR (CDCl₃): δ -17.5 (s). HR MS: m/z calcd for C₂₈H₂₂⁵⁶Fe-

NOP (M^þ³) 475.0788, found 475.0787.

Preparation of 1⁰-(Diphenylphosphino)-1-[(pyrid-2-yl)methyl]-

ferrocene (2). Commercial SmI₂solution (100 mL of 0.1 M in

THF, 10 mmol) was introduced to a stirred mixture of alcohol 4

(1.91 g, 4.0 mmol), (Me₂N)₃PO (HMPA; 7.0 mL, 40 mmol), and

dry THF (10 mL) over 10 min, yielding a dark brown mixture.

After the mixture was stirred for 5 min, a solution of pivalic acid

(514 mg, 5.0 mmol in 5 mL of THF) was added, causing the color

of the reaction mixture to turn back to the initial orange-yellow.

The mixture was stirred for another 15 min and diluted with

diethyl ether and saturated aqueous NaCl. The organic phase

was separated, and the aqueous layer was extracted with diethyl

ether, adding a small amount of hexane to facilitate phase

separation. The combined organic layers were washed with

saturated aqueous NaCl, dried (MgSO₄), and evaporated. The

residue was passed through a short silica gel column with ethyl

acetate-hexane (1:1 v/v) as eluent to remove some polar by-

product and inorganic residue. The first yellow-orange band

was collected and evaporated to afford the crude product, which

was immediately purified by chromatography on an alumina

column using diethyl ether-hexane (4:1 v/v) as the eluent.

Evaporation of the first yellow band followed by careful eva-

poration and drying under vacuum (80 ꢀC/0.1 Torr) gave 2

as a dark orange-brown oil, which slowly crystallized when

stored at 4 ꢀC. Yield: 1.02 g (55%). Note: Some unreacted

ca. 7.4), 129.44 (d, J_PC= 59 Hz, C_ipsoof PPh₂), 130.49 (d,

J_PC= 4 Hz, CH of PPh₂), 130.94 (d, J_PC= 9 Hz, 2 C, CH of

PPh₂), 131.55 (d, J_PC= 3 Hz, CH of PPh₂), 134.44 (d, J_PC= 10

Hz, 2 C, CH of PPh₂), 137.68 (CH of Py, δ_Hca. 7.5), 153.92 (CH⁶

of Py, δ_H8.55), 157.71 (C²of Py). ³¹P{¹H} NMR (CD₂Cl₂): δ

16.4 (s). ESIþ MS: m/z 587 ([M - Cl]^þ), 552 (weak, [M - Cl -

HCl]^þ). IR (Nujol): ν/cm^-11596 (m), 1562 (w), 1309 (w), 1171

(m), 1159 (m), 1097 (s), 1032 (m), 827 (m), 780 (m), 758 (s), 753

(s), 700 (s), 697 (s), 537 (w), 527 (vs), 499 (s), 483 (s), 469 (m).

Anal. Calcd for C₂₇H₂₂Cl₂FeNPPd 0.2CH₂Cl₂(641.6): C,

50.92; H, 3.52; N, 2.18. Found: C, 51.06; H, 3.48; N, 2.18.

Preparation of Dichloro{1⁰-(diphenylphosphino-KP)-1-[(pyrid-

2-yl-KN)methyl]ferrocene}palladium(II) (6). A solution of 2

(93 mg, 0.20 mmol) and [PdCl₂(cod)] (57 mg, 0.20 mmol) in

dichloromethane (5 mL) was stirred at room temperature for

90 min and then filtered through a PTFE syringe filter (0.45 μm

pore size). The filtrate was diluted with dichloromethane (5 mL)

and layered with diethyl ether (8 mL), and the mixture was

allowed to crystallize at room temperature for several days. The

separated product was filtered off, washed with pentane, and

dried under vacuum. Evaporation of the mother liquor followed

by crystallization (dichloromethane (3 mL) þ diethyl ether-

pentane (1:1, 8 mL)) and isolation as above afforded a second

ꢀ

Stepnicka et al.

ꢀ

3198 Organometallics, Vol. 29, No. 14, 2010

crop of the product. Combined yield of 6 0.5CH₂Cl₂: 120 mg

Preparation of trans-Dichlorobis{1⁰-(diphenylphosphino-KP)-

1-[(pyrid-2-yl)methyl]ferrocene}palladium(II) (8). Ligand 2 (92.5

mg, 0.20 mmol) and [PdCl₂(cod)] (28.5 mg, 0.10 mmol) were

dissolved in dichloromethane (4 mL) to give a deep red solution,

which was stirred for 1 h and then filtered through a 0.45 μm

PTFE syringe filter. The filtrate was diluted with dichloro-

methane (1 mL) and layered with diethyl ether (ca. 10 mL),

and the mixture was left crystallizing by liquid-phase diffu-

sion over several days. The separated product was filtered off,

(88%), orange microcrystalline solid.

¹H NMR (CD₂Cl₂): δ 2.32 and 3.64 (2 ꢀ br s, 1 H), 4.04 (dt,

J = 2.6, 1.3 Hz, 1 H) (3 ꢀ CH of fc), 4.08 (d, ²J_HH= 14.8 Hz,

1 H, CH₂Py), 4.24 (dt, J = 1.4, 2.6 Hz, 1 H), 4.27-4.31 (m, 2 H),

4.36 (br m, 1 H), 5.03 (dt, J = 2.4, 1.4 Hz, 1 H) (5 ꢀ CH of fc),

5.42 (d, ²J_HH= 14.8 Hz, 1 H, CH₂Py), 7.10 (ddd, J ≈ 7.3, 5.7,

1.5 Hz, 1 H, Py), 7.38-7.82 (partly broad m, 11 H, PPh₂and 1 H

of Py: δ_Hca. 7.55 according to 2D spectra), 7.87 (td, J = 7.7, 1.6

Hz, 1 H, H⁴of Py), 8.32 (d of unresolved t, J = 5.9 Hz, 1 H, H⁶of

Py). ¹³C{¹H} NMR (CD₂Cl₂): δ 39.14 (CH₂Py), 69.31 (d,

¹J_PC= 61 Hz, C_ipsoof Cp^P), 69.31, 70.01, 70.03 (3 ꢀ CH of

Cp^C), 72.22 (d, J_PC= 7 Hz, CH of Cp^P), 73.30 (d, J_PC= 12 Hz,

CH of Cp^P), 74.41 (d, J_PC= 8 Hz, CH of Cp^P), 74.87 (br s, CH of

Cp^C), 75.66 (d, J_PC= 8 Hz, CH of Cp^P), 87.35 (C_ipsoof Cp^C),

123.70 and 127.64 (CH^3/5of Py), 128.09 (d, J_PC= 12 Hz, 2 C,

CH of PPh₂), 129.46 (d, ¹J_PC= 49 Hz, C_ipsoof PPh₂), 129.48 (d,

J_PC= 11 Hz, 2 C, CH of PPh₂), 129.67 (d, ¹J_PC= 64 Hz, C_ipsoof

PPh₂), 131.42 (d, J_PC= 3 Hz, CH of PPh₂), 132.01 (d, J_PC= 2

Hz, CH of PPh₂), 134.03 (br d, J_PC≈ 11 Hz, 2 C, CH of PPh₂),

134.21 (br d, J_PC≈ 9 Hz, 2 C, CH of PPh₂), 139.29 (CH⁴of Py),

151.96 (d, J ≈ 1 Hz, CH⁶of Py), 163.39 (C²of Py). ³¹P{¹H}

NMR (CD₂Cl₂): δ 22.2 (s). ESI ( MS: m/z 602 ([M - Cl]^þ), 566

([M - Cl - HCl]^þ); 674 ([M þ Cl]^-). IR (Nujol): ν/cm^-11602

(s), 1569 (m), 1306 (s), 1275 (m), 1227 (m), 1173 (s), 1168 (s), 1162

(s), 1143 (m), 1100 (vs), 1068 (w), 1042 (s), 1036 (s), 1027 (m), 998

(m), 920 (w), 849 (w), 837 (w), 827 (m), 817 (m), 793 (s), 767 (m),

748 (vs), 730 (vs), 713 (m), 697/693 (vs), 626 (m), 544 (s), 522 (vs),

485 (s), 477 (s), 466 (vs), 451 (m). Anal. Calcd for C₂₈H₂₄Cl₂-

washed with pentane, and dried under vacuum. Yield of 8 0.2-

CH₂Cl₂: 87 mg (78%), well-developed ruby red crystals.

As was the case for complex 7, the NMR spectra of 8 were

recorded on a solution of in situ generated compound due to its

limited solubility. ¹H NMR (CD₂Cl₂): δ 3.81 (br s, 2 H, CH₂Py),

4.32 (vt, J⁰= 1.8 Hz, 2 H), 4.36 (unresolved vt, 2 H), 4.51 (br m,

4 H) (8 ꢀ CH of fc), 7.03-7.11 (m, 2 H, Py), 7.31-7.69 (m, 11 H,

PPh₂þ 1 H of Py), 8.48 (br d, J = 3.1 Hz, H⁶of Py). ¹³C{¹H}

NMR (CD₂Cl₂): δ 38.42 (CH₂Py), 70.55 and 71.00 (2 ꢀ s, 2 C,

CH of Cp^C), 72.92 (apparent t, J⁰= 4 Hz, 2 C, CH of Cp^P), 75.91

(apparent t, J⁰= 5 Hz, 2 C, CH of Cp^P), 87.51 (C_ipsoof Cp^C),

121.20 and 122.60 (2 ꢀ br s, CH^3/5of Py), 127.68 (apparent t,

J⁰= 5 Hz, 4 C, CH of PPh₂), 130.18 (s, 2 C, CH of PPh₂), 131.41

(apparent t, J⁰= 25 Hz, 2 C, C_ipsoof PPh₂), 134.15 (apparent t,

J⁰= 6 Hz, 4 C, CH of PPh₂), 136.38 (CH⁴of Py), 149.05 (CH⁶of

Py), 160.81 (C²of Py) (note: signal due to C_ipsoof C₅H₄P was not

found). ³¹P{¹H} NMR (CD₂Cl₂): δ 15.9 (s). ESIþ MS: m/z 1064

([M - Cl]^þ), 816 ([M - 2Cl - C₅H₄CH₂Py]^þ), 602 ([PdCl(2)]^þ).

IR (Nujol): ν/cm^-11590 (s), 1569 (m), 1303 (m), 1217 (w), 1175

(m), 1166 (s), 1152 (w), 1101 (m), 1091 (m), 1056 (w), 1038 (w),

1026 (s), 996 (m), 929 (w), 847/839/832 (m), 748 (vs), 697/690 (s),

624 (m), 541 (m), 519 (s), 497 (vs), 477 (s), 466 (m), 429/423 (m).

FeNPPd 0.5CH₂Cl₂(681.1): C, 50.16; H, 3.79; N, 1.87. Found:

C, 50.26; H, 3.70; N, 2.06.

Preparation of trans-Dichlorobis[1⁰-(diphenylphosphino-KP)-

1-(pyrid-2-yl)ferrocene]palladium(II) (7). [PdCl₂(cod)] (28.5 mg,

0.10 mmol) and 1 (89.5 mg, 0.21 mmol) were mixed with di-

chloromethane (2 mL), and the resulting mixture was stirred at

room temperature for 3 h to give a red precipitate. Pentane(2 mL)

was added to ensure complete precipitation, and the separated

solid was filtered off, washed successively with diethyl ether and

Anal. Calcd for C₅₆H₄₈Cl₂Fe₂N₂P₂Pd 0.2CH₂Cl₂(1116.9): C,

60.43; H, 4.37; N, 2.51. Found: C, 60.54; H, 4.37; N, 2.40.

Preparation of [SP-4-4]-Chloro{2-[(dimethylamino)methyl]-

phenyl-KC¹}[1⁰-(diphenylphosphino-KP)-1-(pyrid-2-yl)ferrocene]-

palladium(II) (9). [(L^NC)PdCl]₂(27.5 mg, 50 μmol) and 1 (44.5 mg,

0.10 mmol) were dissolved in dichloromethane (2 mL). The

resulting solution was stirred for 2 h and then evaporated to

dryness. The residue was washed successively with diethyl

ether-pentane (1:1 v/v) and pentane and dried under vacuum

to give 9 as an orange solid. Yield: 67 mg, 87% (the compound

pentane, and dried under vacuum to afford 7 0.2CH₂Cl₂as a red

solid (101 mg, 94%). Crystalline material resulted when the

initially separated product was redissolved by addition of more

dichloromethane, and the resulting solution was layered with

diethyl ether and allowed to crystallize by liquid-phase diffusion.

Because the isolated (crystallized) complex is only poorly soluble

in CD₂Cl₂, the NMR spectra were recorded for in situ generated

7. The NMR spectra indicated that 7 is formed cleanly, the libe-

rated cycloocta-1,5-diene and a tiny amount of 5 being the only

side products.

retains traces of dichloromethane, analyzing as 9 0.5CH₂Cl₂).

Selected ¹H NMR data for 9 (CD₂Cl₂): δ 3.93 (d, J = 3.4 Hz,

2 H, CH₂Py), 4.09 (m, 2 H, fc), 4.15 (d, J = 2.2 Hz, 2 H, NCH₂),

4.36 (m, 2 H, fc), 4.90 (vt, J⁰= 1.9 Hz, 2 H, fc), 5.07 (vt, J⁰= 1.9

Hz, 2 H, fc), 8.45 (d of unresolved m, J = 4.2 Hz, 1 H, H⁶of Py).

Selected ¹H NMR data for 11a (CD₂Cl₂): δ 3.79 and 3.98 (2 ꢀ d,

J = 14.2 Hz, 1 H, CH₂Py), 4.05 (m, 1 H, fc), 4.05 (dd, J = 13.4,

ca. 2.5 Hz, 1 H, NCH₂), 4.21 (dd, J = 13.4, 2.1 Hz, 1 H, NCH₂),

4.31 (m, 1 H, fc), 4.36 (m, 1 H, fc), 4.48 (m, 1 H, fc), 4.98 (d of vt,

J⁰= 1.3, 2.6 Hz, 1 H, fc), 5.00 (d of vt, J⁰= 1.3, 2.6 Hz, 1 H, fc),

5.63 (d of vt, J⁰= 2.6, 1.3 Hz, 1 H, fc), 6.23 (d of vt, J⁰= 2.6, 1.3

Hz, 1 H, fc), 8.92 (dd, J = 5.6, 1.1 Hz, 1 H, H⁶of Py). ³¹P{¹H}

NMR (CD₂Cl₂): δ 32.7 and 32.9 (2 ꢀ s). ESIþ MS: m/z 687

([M - Cl]^þ). IR (Nujol): ν/cm^-11600 (w), 1578 (m), 1559 (m),

1305 (w), 1288 (vw), 1162 (m), 1097 (m), 1027 (m), 986 (w), 968

(w), 891 (w), 845 (m), 740 (s), 696 (m), 521 (m), 498 (w). Anal.

¹H NMR (CD₂Cl₂): δ 4.18 (vt, J⁰≈ 1.9 Hz, 2 H), 4.53 (br m,

2 H), 4.84 (vt, J⁰≈ 1.9 Hz, 2 H), 5.10 (vt, J⁰≈ 1.9 Hz, 2 H) (4 ꢀ

CH of fc), 7.10 (ddd, J = 7.4, 4.9, 1.1 Hz, 1 H, Py), 7.36-7.50 (m,

7 H, 6 H of PPh₂þ 1 H of Py), 7.57 (td, J = 7.8, 2.0 Hz, 1 H, Py),

7.62-7.69 (m, 4 H, PPh₂), 8.49 (ddd, J = 4.9, 1.8, 0.9 Hz, 1 H,

H⁶of Py). ¹³C{¹H} NMR (CD₂Cl₂): δ 69.30 (2 C, CH of Cp^C),

74.78 (apparent t, J⁰= 27 Hz, C_ipsoof Cp^P), 73.44 (2 C, CH of

Cp^C), 74.89 (2 C, apparent t, J⁰= 4 Hz, CH of Cp^P), 76.41 (2 C,

apparent t, J = 5 Hz, CH of Cp^P), 85.96 (C_ipsoof Cp^C), 120.79

and 121.38 (2 ꢀ CH of Py), 128.12 (apparent t, J⁰= 5 Hz, 4 C,

CH of PPh₂), 130.71 (2 C, CH of PPh₂), 131.72 (apparent t, J⁰=

25 Hz, 2 C, C_ipsoof PPh₂), 134.58 (apparent t, J⁰= 5 Hz, 4 C, CH

of PPh₂), 136.38 (CH⁴of Py), 149.83 (CH⁶of Py), 158.31 (C²of

Py). ³¹P{¹H} NMR (CD₂Cl₂): δ 16.2 (s). ESIþ MS: m/z 1035

([M - Cl]^þ), 802 (weak, [M - 2Cl - FeC₅H₄C₅H₄N]^þ), 589

([M - Cl - 1]^þ). IR (Nujol): ν/cm^-11585 (s), 1566 (m), 1496 (m),

1306 (w), 1288 (w), 1277 (w), 1195 (w), 1180 (w), 1168 (m), 1160

(w), 1097 (m), 1055 (w), 1049 (w), 1034 (m), 1024 (m), 894 (w),

826 (m), 782 (m), 747 (w), 740 (m), 734 (w), 709 (w), 696 (s), 688

(m), 623 (m), 527 (w), 515 (s), 493 (s), 471 (m), 439 (w), 423 (w).

Calcd for C₃₆H₃₄ClFeN₂PPd 0.5CH₂Cl₂(765.79): C, 57.24; H,

4.61; N, 3.66. Found: C, 57.27; H, 4.67; N, 3.53.

Preparation of [SP-4-4]-Chloro{2-[(dimethylamino)methyl]-

phenyl-KC¹}{1⁰-(diphenylphosphino-KP)-1-[(pyrid-2-yl)methyl]-

ferrocene}palladium(II) (10). [(L^NC)PdCl]₂(27.5 mg, 50 μmol)

and 2 (46.5 mg, 0.10 mmol) were dissolved in dichloromethane

(3 mL). The solution was stirred for 1 h, filtered (0.45 μm PTFE

filter), and evaporated to dryness. The solid residue was washed

with diethyl and pentane and dried under vacuum to afford 10 as

an orange solid. Yield: 62 mg, 84%.

¹H NMR (CD₂Cl₂): δ 2.80 (d, ⁴J_PH= 2.7 Hz, 3 H, NMe₂),

3.85 (s, 2 H, CH₂Py), 4.11 (d, ⁴J_PH= 2.3 Hz, 2 H, NCH₂), 4.33

(br s, 4 H, CH of fc), 4.41 and 4.52 (2 ꢀ vt, J⁰= 1.8 Hz, 2 H, CH

Anal. Calcd for C₅₄H₄₄Cl₂Fe₂N₂P₂Pd 0.2CH₂Cl₂(1088.8): C,

59.78; H, 4.11; N, 2.57. Found: C, 59.50; H, 4.13; N, 2.52.

Article

Organometallics, Vol. 29, No. 14, 2010 3199

of fc), 6.31 (ddd, J = 7.7, 6.3, 1.2 Hz, 1 H, CH of C₆H₄), 6.39 (td,

J = 7.7, ca. 1.3 H, 1 H, CH of C₆H₄), 6.83 (td, J = 7.3, 1.2 Hz,

1 H, CH of C₆H₄), 7.02 (dd, J = 7.4, 1.5 Hz, 1 H, CH of C₆H₄),

7.06-7.12 (m, 2 H, CH^3/5of Py), 7.32-7.62 (m, 11 H, PPh₂þ

1 H of Py), 8.45 (ddd, J = 4.9, 1.8, 0.8 Hz, 1 H, H⁶of Py).

¹³C{¹H} NMR (CD₂Cl₂): δ 38.68 (CH₂Py), 50.28 (d, ³J_PC= 2

Hz, NMe₂), 70.99 and 71.38 (2 ꢀ 2 C, CH of Cp^C), 73.22 (d,

Preparation of [SP-4-3]-{2-[(Dimethylamino)methyl]phenyl-

KC¹}{1⁰-(diphenylphosphino-KP)-1-[(pyrid-2-yl-KN)methyl]ferro-

cene]palladium(II) Perchlorate (12). [(L^NC)Pd(MeCN)₂]ClO₄(42.5

mg, 0.10 mmol) and 1 (46 mg, 0.1 mmol) were dissolved in

dichloromethane (3 mL). The solution was stirred for for 1 h

and filtered (0.45 μm PTFE filter). The filtrate was diluted with

dichloromethane (3 mL) and overlayered with diethyl ether

(12 mL). Crystallization at room temperature for several days

afforded a crystalline product, which was filtered off, washed with

diethyl ether, and dried under vacuum. Yield of 12: 74 mg (92%),

rusty brown crystals.

_PC= 7 Hz, 2 C, CH of Cp^P), 73.48 (d, ¹J_PC= 59 Hz, C_ipsoof

Cp^P), 73.86 (d, ³J_PC= 4 Hz, NCH₂), 76.21 (d, J_PC= 10 Hz, 2 C,

CH of Cp^C), 88.17 (C_ipsoof Cp^C), 121.53 and 122.80 (CH^3/5of

Py), 122.84 and 124.00 (2 ꢀ CH of C₆H₄), 125.04 (d, J_PC= 6 Hz,

CH of C₆H₄), 128.12 (d, J_PC= 10 Hz, 4 C, CH of PPh₂), 130.80

(d, J_PC= 2 Hz, 2 C, CH of PPh₂), 132.55 (d, ¹J_PC= 49 Hz, 2 C,

C_ipsoof PPh₂), 134.74 (d, J_PC= 12 Hz, 4 C, CH of PPh₂), 136.60

(CH⁴of Py), 138.79 (d, J_PC= 10 Hz, CH of C₆H₄), 149.07 (d,

¹H NMR (CD₂Cl₂): δ 2.25 (d, ⁴J_PH= 3.3 Hz, 3 H, NMe), 2.54

(d, ⁴J_PH= 2.1 Hz, 3 H, NMe), 2.80 and 3.84 (2 ꢀ br s, 1 H, CH of

fc), 3.98 (dd, ²J_HH= 13.4, ⁴J_PH= 3.2 Hz, 1 H, NCH₂), 3.98 (dt,

J⁰= 2.7, 1.3 Hz, 1 H), 4.25 (dt, J⁰= 1.3, 2.4 Hz, 1 H), 4.28 (dt,

J = 1.3, 2.6 Hz, 1 H) (3 ꢀ CH of fc), 4.33 (d, ²J_HH= 14.3 Hz,

1 H, CH₂Py), 4.37 and 4.48 (2 ꢀ m, 1 H, CH of fc), 4.48 (br d,

²J_HH= 13.4 Hz, 1 H, NCH₂), 4.63 (dt, J⁰= 2.4, 1.3 Hz, CH of

fc), 5.03 (d, ²J_HH= 14.3 Hz, 1 H, CH₂Py), 6.35-6.43 (m, 2 H,

C₆H₄), 6.85-6.92 and 7.06-7.10 (2 ꢀ m, 1 H, C₆H₄), 7.27-7.63

(m, 9 H, 8 H of PPh₂þ 1 H of Py), 7.69 (dt, J = 7.9, 1.1 Hz, 1 H,

Py), 7.77-7.84 (m, 2 H, PPh₂), 8.03 (td, J = 7.8, 1.7 Hz, H⁴of

Py), 8.38 (ddd, J = 5.5, 1.6, 0.6 Hz, H⁶of Py). ¹³C{¹H} NMR

(CD₂Cl₂): δ 39.28 (CH₂Py), 50.71 and 50.32 (2 ꢀ d, ³J_PC= 2 Hz,

NMe₂), 70.01, 70.32, 70.48, and 72.27 (CH of Cp^C), 72.46 (d,

J_PC= 7 Hz, CH of Cp^P), 72.83 (d, ¹J_PC= 59 Hz, C_ipsoof Cp^P),

72.86 (d, ³J_PC= 3 Hz, NCH₂), 73.37 (d, J_PC= 10 Hz, CH of

Cp^P), 74.62 (d, J_PC= 7 Hz, CH of Cp^P), 75.45 (d, J_PC= 10 Hz,

CH of Cp^P), 85.96 (C_ipsoof Cp^C), 123.51 (CH of C₆H₄), 125.07

(CH^3/5of Py), 125.30 (CH of C₆H₄), 125.69 (d, J_PC= 5 Hz, CH

of C₆H₄), 127.81 (CH^3/5of Py), 128.45 (d, J_PC= 12 Hz, 2 C, CH

of PPh₂), 129.48 (d, J_PC= 11 Hz, 2 C, CH of PPh₂), 130.18 (d,

¹J_PC= 48 Hz, C_ipsoof PPh₂), 130.57 (d, ¹J_PC= 56 Hz, C_ipsoof

PPh₂), 131.50 and 131.97 (2 ꢀ d, J_PC= 2 Hz, CH of PPh₂),

134.35 and 134.88 (2 ꢀ d, J_PC= 12 Hz, 2 C, CH of PPh₂), 139.79

(d, J_PC= 12 Hz, CH of C₆H₄), 140.02 (CH⁴of Py), 148.32 and

148.53 (2 ꢀ d, J_PC= 2 Hz, C_ipsoof C₆H₄), 150.18 (CH⁶of Py),

160.98 (C²of Py). ³¹P{¹H} NMR (CD₂Cl₂): δ 34.3 (s). ESIþ MS:

m/z 701 ([(L^NC)Pd(2)]^þ). IR (Nujol): ν/cm^-11601 (m), 1567 (m),

1307 (m), 1230 (w), 1187 (w), 1166 (m), 1090 (br vs), 1045 (w),

1033 (w), 1020 (m), 994 (w), 977 (w), 900 (w), 866 (w), 856 (w),

845 (m), 830 (m), 817 (m), 794 (m), 768 (m), 752 (s), 743 (s), 702

(s), 695 (s), 622 (s), 545 (s), 521 (s), 491 (s), 469 (s), 450 (w), 437

(m). Anal. Calcd for C₃₇H₃₆ClFeN₂O₄PPd (801.3): C, 55.45; H,

4.53; N, 3.50. Found: C, 55.15; H, 4.63; N, 3.38.

_PC= 2 Hz, C_ipsoof C₆H₄), 149.43 (CH⁶of Py), 152.66 (C_ipsoof

C₆H₄), 161.25 (C²of Py). ³¹P{¹H} NMR (CD₂Cl₂): δ 33.1 (s). IR

(Nujol): ν/cm^-11589 (s), 1579 (m), 1568 (m), 1303 (m), 1180 (w),

1163 (s), 1098 (s), 1028 (s), 994 (m), 972 (w), 928 (w), 864 (w), 845

(s), 744 (vs), 695 (vs), 626 (w), 544 (m), 524 (s), 503 (vs), 476 (s).

ESIþ MS: m/z 701 ([M - Cl]^þ). Anal. Calcd for C₃₇H₃₆-

ClFeN₂PPd (737.3): C, 60.27; H, 4.92; N, 3.80. Found: C,

61.10; H, 5.15; N, 3.48.

Preparation of [SP-4-3]-{2-[(Dimethylamino)methyl]phenyl-

KC¹}[1⁰-(diphenylphosphino-KP)-1-(pyrid-2-yl-KN)ferrocene]-

palladium(II) Perchlorate (11). [(L^NC)Pd(MeCN)₂]ClO₄(42 mg,

0.10 mmol) and 1 (44.5 mg, 0.1 mmol) were dissolved in dichlo-

romethane (2 mL), and the mixture was stirred for 2 h (the product

partly separates). Pentane (2 mL) was added to complete precipi-

tation of the product, and the separated solid was filtered off,

washed with diethyl ether and pentane, and dried under vacuum to

give 11 as an orange solid. Yield: 67 mg, 85%. Crystalline material

resulted when the initially precipitated 11 was redissolved by

adding more dichloromethane and the solution was allowed to

crystallize by liquid-phase diffusion of diethyl ether.

¹H NMR (CD₂Cl₂): δ 2.03 (d, ⁴J_PH= 3.4 Hz, 3 H, NMe), 2.55

(d, ⁴J_PH= 1.8 Hz, 3 H, NMe), 3.02 (m, 1 H, CH of fc), 3.61 (dd,

²J_HH= 13.4, ⁴J_PH= 3.7 Hz, 1 H, NCH₂), 3.72 (m, 1 H), 4.30 (m,

1 H), 4.59 (tdd, J = 2.6, 1.2, 0.4 Hz, 1 H), 4.71 (m, 1 H) (4 ꢀ CH

of fc), 4.82 (d, ²J_HH= 13.4 Hz, 1 H, NCH₂), 4.90-4.93 (m, 2 H,

CH of fc), 6.37-6.46 (m, 2 H, C₆H₄), 6.84 (m, 1 H, CH of fc;

partly obscured by the neighboring signal), ca. 6.84-6.90 (m,

1 H, C₆H₄), 7.07 (d of unresolved m, J ≈ 7.4 Hz, 1 H, C₆H₄),

7.24-7.69 (m, 8 H of PPh₂þ 1 H of Py: δ_H7.35, ddd, J ≈ 7.6, 5.5,

1.4 Hz), 7.69 (ddd, J = 8.1, 1.4, 0.7 Hz, 1 H, CH of Py), 7.89

(ddd, J = 8.1, 7.6, 1.7 Hz, 1 H, H⁴of Py), 7.99-8.06 (m, 2 H,

PPh₂), 8.98 (ddd, J = 5.5, 1.6, 0.7 Hz, 1 H, H⁶of Py). ¹³C{¹H}

NMR (CD₂Cl₂): δ 49.39 and 49.41 (2 ꢀ d, ³J_PC= 2 Hz, NMe₂),

70.65 (CH of Cp^C), 71.75 (d, J_PC= 7 Hz, CH of Cp^P), 72.54 (d,

NMR Reactions of 10 with HCl, CF₃CO₂H, or MeI. An NMR

tube was charged with a solution of complex 10 in CD₂Cl₂(14.8

mg, 20 μmol in ca. 0.7 mL). The appropriate reagent was added

(30 μL of 0.69 M methanolic HCl or 40 μL of 0.51 M CF₃CO₂H

in CD₂Cl₂; ca. 20 μmol), and the mixture was allowed to stand

for 1 h before being analyzed by ¹H and ³¹P{¹H} NMR

spectroscopy. The reaction with MeI was carried out at a half

molar scale (i.e., with 7.4 mg (10 μmol) of the complex and

5.6 mg (39 μmol) of MeI).

¹J_PC= 60 Hz, C_ipsoof Cp^P), 72.63 (CH of Cp^C), 73.15 (d, ³J_PC

3 Hz, NCH₂), 74.24 (CH of Cp^C), 76.07 and 76.17 (2 ꢀ d, J_PC

8 Hz, CH of Cp^P), 77.42 (d, J_PC= 4 Hz, CH of Cp^P), 78.68 (d,

J_PC= 12 Hz, CH of Cp^P), 81.37 (C_ipsoof Cp^C), 123.38 (CH of

Py), 123.68 (CH of C₆H₄), 125.09 (CH of Py), 125.28 (CH of

C₆H₄), 126.13 (d, J_PC= 6 Hz, CH of C₆H₄), 128.08 (d, ¹J_PC

Attempted Reaction of 10 with in Situ Generated [(Ph₃P)-

Au]SbF₆. Isolation of 12a. A solution of silver(I) hexafluoroan-

timonate (17.5 mg, 0.05 mmol) in THF (1 mL) was added to a

dichloromethane solution of [(Ph₃P)AuCl] (25 mg, 0.05 mmol in

1 mL), causing immediate separation of an off-white precipitate

(AgCl). The mixture was stirred for 10 min and filtered through

a PTFE syringe filter (0.45 μm pore size), and the filtrate was

added to a solution of complex 9 (37 mg, 0.05 mmol) in di-

chloromethane (2 mL). The mixture was stirred for 30 min and

evaporated under vacuum. The orange-brown residue was dis-

solved in dichloromethane, and the solution was layered with

diethyl ether. Crystallization by liquid-phase diffusion at 4 ꢀC

over several days afforded a crystalline solid, which was filtered

off, washed with diethyl ether, and dried under vacuum to afford

12a as a rusty orange crystalline solid. Yield: 38 mg (81%). The

filtrate was evaporated, and the residue was analyzed by NMR

46 Hz, C_ipsoof PPh₂), 128.65 (br d, J_PC≈ 12 Hz, 4 C, CH of

¹J_PC= 56 Hz, C_ipsoof PPh₂), 131.42 and 130.90 (2 ꢀ d, J_PC

PPh₂), 129.97 (d, J_PC= 11 Hz, 2 C, CH of PPh₂), 130.36 (d,

2 Hz, CH of PPh₂), 136.11 (d, J_PC= 14 Hz, 2 C, CH of PPh₂),

139.80 (d, J_PC= 12 Hz, CH of C₆H₄), 140.02 (CH⁴of Py),

147.56 and 148.49 (2 ꢀ d, J_PC= 2 Hz, C_ipsoof C₆H₄), 150.13

(CH⁶of Py), 161.04 (C²of Py). ³¹P{¹H} NMR (CD₂Cl₂): δ 32.6

(s). ESIþ MS: m/z 687 ([(L^NC)Pd(1)]^þ). IR (Nujol): ν/cm^-11597

(m), 1580 (w), 1564 (w), 1497 (m), 1306 (w), 1291 (w), 1281 (w),

1168 (m), 1162 (w), 1115 (w), 1107 (s), 1095 (vs), 1083 (vs), 1037

(s), 1021 (m), 1006 (w), 991 (w), 972 (w), 892 (w), 865 (w), 842

(m), 818 (w), 793 (m), 747 (s), 697 (m), 689 (m), 622 (m), 537 (m),

513 (m), 493 (w), 480 (m), 462 (w), 432 (w). Anal. Calcd for

C₃₆H₃₄ClFeN₂O₄PPd (787.3): C, 54.92; H, 4.35; N, 3.56.

Found: C, 54.76; H, 4.25; N, 3.49.

ꢀ

Stepnicka et al.

ꢀ

3200 Organometallics, Vol. 29, No. 14, 2010

and ESI mass spectroscopy as essentially pure [AuCl(PPh₃)]

(NMR (CDCl₃): δ_H7.44-7.57 (m, PPh₃); δ_P33.8 (s). ESIþ

(methanol): m/z 517 ([Ph₃PAuCl þ Na]^þ), 658, 721 ([(Ph₃P)₂-

Au]^þ), 953 ([(Ph₃PAu)₂Cl]^þ)), containing only traces of several

unidentified compounds (³¹P{¹H} NMR (CDCl₃): δ 28.9, 29.1,

29.7, and 43.0).

Full-set diffraction data ((h,(k,(l, θ_max= 26ꢀ for 11 and ca.

27.5ꢀ for all other compounds; data completeness 99.2-99.9%)

were collected with a Nonius KappaCCD diffractometer

equipped with a Cryostream Cooler (Oxford Cryosystems)

at 150(2) K using graphite-monochromated Mo KR radiation

(λ = 0.710 73 A). If appropriate, the data were corrected for

absorption by using the correction routines incorporated in the

diffractometer software. The ranges of transmission factors

(TF) are given in the Supporting Information.

Analytical Data for 12a. ¹H NMR (CD₂Cl₂): δ 2.23 (d, ⁴J_PH

3.3 Hz, 3 H, NMe), 2.53 (d, ⁴J_PH= 2.0 Hz, 3 H, NMe), 2.78 and

3.82 (2 ꢀ br s, 1 H, CH of fc), ca. 3.95 (br dd, ²J_HHnot read due

to overlaps, J_PH= 3.2 Hz, 1 H, NCH₂), 3.97 (dt, J = 2.6,

The structures were solved by direct methods (SIR97⁵²) and

refined by full-matrix least squares on F²(SHELXL97⁵³). With

only a few exceptions (see below), the non-hydrogen atoms were

refined with anisotropic displacement parameters. The hydroxyl

hydrogen in the structure of 4 was identified on the difference

electron density map and refined as a riding atom. Other hydro-

gen atoms were included in their calculated positions and refined

as riding atoms with U_iso(H) assigned to a multiple of U_eqof

their bonding atom. Relevant crystallographic data are sum-

marized in the Supporting Information. Particular details on

structure refinement are as follows.

The CHOH group in the structure of 4 is probably disordered

in the space defined by its bulky substituents. However, the con-

tributions from other orientations are rather minor and could

not be refined, resulting in relatively high residual electron den-

sity maxima. Furthermore, the perchlorate ion in the structure

of 12 is contributed from two positions, one of them with

chlorine in a special position and the other located around the

symmetry element. The proximity of the two symmetry-related

orientations of the latter did not allow the oxygen atoms to be

refined with anisotropic displacement parameters.

Geometric parameters and structural drawings were obtained

with a recent version of the Platon program.⁵⁴All calculated

values are rounded with respect to their estimated standard

deviations (esd’s) given with one decimal; parameters involving

atoms in constrained positions are given without esd’s.

CCDC file numbers 771191-771197 contain the supplemen-

tary 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.

1.4 Hz, 1 H), 4.25 (dt, J = 1.3, 2.6 Hz, 1 H), 4.28 (dt, J = 1.3,

2.6 Hz, 1 H) (3 ꢀ CH of fc), 4.31 (d, J_HH= 14.2 Hz, 1 H,

CH₂Py), 4.36 and 4.48 (2 ꢀ m, 1 H, CH of fc), 4.48 (br d, ²J_HH

13.2 Hz, 1 H, NCH₂), 4.62 (dt, J = 2.6, 1.3 Hz, CH of fc), 5.02

(d, J_HH= 14.2 Hz, 1 H, CH₂Py), 6.35-6.43 (m, 2 H, C₆H₄),

6.86-6.92 and 7.06-7.10 (2 ꢀ m, 1 H, C₆H₄), 7.28-7.63 (m, 9

H, 8 H of PPh₂þ 1 H of Py), 7.68 (d of unresolved t, J = 7.9 Hz,

1 H, Py), 7.76-7.82 (m, 2 H, PPh₂), 8.01 (td, J = 7.8, 1.7 Hz, H⁴

of Py), 8.34 (d of m, J ≈ 5 Hz, H⁶of Py). ³¹P{¹H} NMR

(CD₂Cl₂): δ 34.5. ESI ( MS: m/z 701 ([(L^NC)Pd(2)]^þ); 235/237

(SbF₆^-). IR (Nujol): ν/cm^-11602 (m), 1582 (w), 1567 (w), 1307

(m), 1231 (w), 1166 (m), 1096 (m), 1060 (w), 1034 (w), 1019 (m),

991 (w), 974 (w), 924 (w), 841 (m), 719 (m), 791 (m), 767 (w), 755

(s), 745 (s), 698 (s), 658 (vs), 626 (w), 546 (s), 521 (s), 492 (s),

471 (s), 450 (m), 443 (m). Anal. Calcd for C₃₇H₃₆F₆FeN₂-

PPdSb (937.6): C, 47.39; H, 3.87; N, 2.99. Found: C, 47.12; H, 3.94;

N, 2.84.

Suzuki-Miyaura Cross-Coupling. A Schlenk tube was charged

with phenylboronic acid (268 mg, 2.2 mmol), 4-bromotoluene

(342 mg, 2.0 mmol), potassium carbonate (604 mg, 4.4 mmol),

and dioxane (10 mL). The respective palladium precatalyst

(0.25 or 0.5 mol % Pd) was introduced as a solution in dichloro-

methane (0.5 mL), and the resulting mixture was heated to 80 or

100 ꢀC for 24 h. The progress in the reaction was monitored by

NMR spectroscopy. As precatalysts, the defined compounds

[PdCl₂(L)] (L = dppf, 1, 2) or complexes generated in situ by

mixing Pd(AcO)₂with the appropriate ligand L (1.2 equiv; in

0.5 mL of dichloromethane for 5 min) were used.

Pd-Catalyzed Cyanation Reactions. A solution of palladium

precatalyst (0.5 mol % of Pd) in dry NMP or DMF (3 mL) was

added to a mixture of solid sodium carbonate (212 mg, 2.0

mmol), 4-bromotoluene (342 mg, 2.0 mmol), and anhydrous

potassium hexacyanidoferrate(II) (184 mg, 0.5 mmol) in a

Schlenk tube. The resulting mixture was heated to 130 ꢀC for

16 h and then analyzed by NMR spectroscopy. As the palladium

precatalyst were used the defined complexes [PdCl₂L] (L =

dppf, 1, 2) or complexes prepared in situ by reacting Pd(AcO)₂

and the respective ligand (1.2 equiv) in dichloromethane

(0.5 mL) for 5 min and mixing the solution with DMF or NMP

(3 mL) .

Acknowledgment. This work was supported by the

Czech Science Foundation (Project No. P207/10/0176)

and a bilateral KONTAKT program by the Ministry of

Education of the Czech Republic (Project MEB100906)

and the Deutsche Akademischer Austauschdienst (Project

D/07/01319). It is also a part of the long-term research

projects of the Faculty of Science, Charles University

in Prague, supported by the Ministry of Education,

Youth and Sports of the Czech Republic (Project No.

MSM0021620857).

X-ray Crystallography. Crystals suitable for single-crystal

X-ray diffraction analysis were grown from ethyl acetate-

hexane (4, orange-brown block, 0.36 ꢀ 0.48 ꢀ 0.55 mm³), di-

chloromethane-ethanol (5, orange-brown plate, 0.10 ꢀ 0.23 ꢀ

Supporting Information Available: A table giving crystal data

and details of the data collection and structure refinement and

CIF files giving crystal data for 4, 5, 7 CH₂Cl₂, 8, 11, and 12.

This material is available free of charge via the Internet at http://

pubs.acs.org.

0.25 mm³), or dichloromethane-diethyl ether (7 CH₂Cl₂, red

bar, 0.13 ꢀ 0.35 ꢀ 0.35 mm³; 8, red block, 0.20 ꢀ 0.42 ꢀ 0.43

mm³; 11, orange-brown plate, 0.03 ꢀ 0.10 ꢀ 0.13 mm³; 12,

orange prism, 0.23 ꢀ 0.25 ꢀ 0.37 mm³).

(53) Sheldrick, G. M. SHELXL97: Program for Crystal Structure

€

Refinement from Diffraction Data; University of Gottingen, Gottingen,

Germany, 1997.

(52) 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.

(54) (a) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7. (b) This program

package is available via the Internet at http://www.cryst.chem.uu.nl/platon/.

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