Reactivity of ortho-β-enaminone-phenyl palladium complexes. Insertion of CO into the Pd-C bond to give the first acyl C,N,O-pincer complexes. sequential insertion of dimethylacetylenedicarboxylate into the enaminone C-H bond and of isocyanide into the Pd-

DOI: 10.1021/om1005403

Source and publish data:

Organometallics p. 5693 - 5707 (2010)

Update date:2022-07-29

Topics:

Authors:

Vicente, Jose

Chicote, Maria Teresa

Martinez-Martinez, Antonio Jesus

Abellan-Lopez, Antonio

Bautista, Delia

Read Full Text PDF DownLoad Join now for total 90,000,000 free articles

Article abstract of DOI:10.1021/om1005403

Insertion of CO into the Pd-C_aryl bond of complexes [PdI{C ₆H₄{NHC(Me)CHC(O)Me}-2}(N^N)] afforded the benzoyl derivatives [PdI{C(O)C₆H₄{NHC(Me)CHC(O)Me}-2}(N^N)] [N^N = 4,4′-di-tert-butyl-2,2′-dipyrid

Full text of DOI:10.1021/om1005403

Organometallics 2010, 29, 5693–5707 5693

DOI: 10.1021/om1005403

Reactivity of ortho-β-Enaminone-phenyl Palladium Complexes. Insertion

of CO into the Pd-C Bond to Give the First Acyl C,N,O-Pincer

Complexes. Sequential Insertion of Dimethylacetylenedicarboxylate

into the Enaminone C-H Bond and of Isocyanide into the Pd-C Bond.

A New Photooxigenation/Cyclization Process^†

ꢀ

Jose Vicente,* Marıa Teresa Chicote, Antonio Jesus Martınez-Martınez, and

ꢀ

Antonio Abellan-Lopez

ꢀ

Grupo de Quımica Organometalica, Departamento de Quımica Inorganica, Universidad de Murcia,

ꢀ

Apartado 4021, 30071 Murcia, Spain

Delia Bautista

SAI, Universidad de Murcia, Apartado 4021, 30071 Murcia, Spain

Received May 31, 2010

Insertion of CO into the Pd-C_arylbond of complexes [PdI{C₆H₄{NHC(Me)CHC(O)Me}-2}-

(N^∧N)] afforded the benzoyl derivatives [PdI{C(O)C₆H₄{NHC(Me)CHC(O)Me}-2}(N^∧N)] [N^∧N =

4,4⁰-di-tert-butyl-2,2⁰-dipyridyl (^tBubpy) (1a), N,N,N⁰,N⁰-tetramethylethylenediamine (tmeda) (1b)].

The reactions of [Pd{C,C-C₆H₄{NHdC(Me)CHC(O)Me}-2}(tmeda)]OTf (OTf = CF₃SO₃) with

excess CO and tmeda (2:1) or HOTf (1:1) produced the dinuclear benzoyl complex [{Pd{C,N,

O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-2}₂(μ-tmeda)] (2) or [Pd₂{μ-O,C,N,O⁰-{OdCC₆H₄{NC(Me)-

CHC(O)Me}-2}₂}] (3), respectively. The latter reacted with anionic or neutral ligands to give

complexes Bu₄N[{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-2}₂(μ-OH)] (4), Q[Pd{C,N,O-{C-

(O)C₆H₄{NC(Me)CHC(O)Me}-2}}Cl] [Q = PPN (5a), NMe₄(5b)], or [{Pd{C,N,O-{C(O)C₆H₄-

{NC(Me)CHC(O)Me}-2}L] (L = CN^tBu (6a), CNXy (6b), PPh₃(6c), NH₃(6d), NH₂Me (6e), MeCN

(6f), dmso (6g)), respectively. The reaction of dimethylacetylenedicarboxylate (DMAD) with [PdI-

{C₆H₄{NHC(Me)CHC(O)Me}-2}(tmeda)] (1:1) afforded [PdI{C₆H₄{NHC(Me)C{Z-C(CO₂Me)d

CH(CO₂Me)}C(O)Me}}-2}(tmeda)] (7Z), resulting from the insertion of the alkyne into the C-

(sp²)-H bond of the enaminone substituent. 7Z isomerized into the E analogue (7E) when heated in

toluene at 95 °C and reacted in two steps with AgClO₄and XyNC (1:1:2) to give the C,N,O-pincer

derivative Pd{C,N,O-{C(dNXy)C₆H₄{NC(Me)C{C(CO₂Me)dCHCO₂Me)}C(O)Me}-2}(CNXy)]

(8) as a mixture of the Z and E isomers. The latter complex converted, after a photochemical oxy-

genation, into the palladacycle [Pd{C,N,O-{C(dNXy)C₆H₄{N(dmoc)}-2](CNXy)] 2CHCl₃(9),

where the imino substituent dmoc is the cycle 1,2-di(methoxycarbonyl)-3-oxocyclopent-1-ene-4-yl.

Compound 8 or 9 reacted with triflic or picric acid to give the species Pd{C,N,O-{C(dNHXy)C₆H₄-

{NC(Me)C{C(CO₂Me)dCHCO₂Me)}C(O)Me}-2}(CNXy)]OTf (10) or [Pd{C,N,O-{C(dNXy)C₆-

H₄{N(dmoc)}-2](CNXy)] Hpic (11; Hpic = picric acid), respectively. The crystal structures of

complexes 2, 3, 5a, 6b, 6c, 6e, 7Z, 7E, and 10 have been determined.

Introduction

alkenes,^3,20allenes,^19,20carbodiimides,^21,22isothiocyanates,^9,22

nitriles,^22,23cyanamides²²). These reactions are of interest

because they are involved in many stoichiometric and catalytic

palladium-mediated organic transformations.^{3,5,6,9,10,12-14,17,24}

We are studying the synthesis of ortho-functionalized aryl

metal complexes and their reactivity toward unsaturated mo-

lecules (isocyanides,^1-11CO,^{1,3,5,9,11-16}alkynes,^{3-6,11,12,17-19}

ꢀ

(2) Vicente, J.; Abad, J. A.; Frankland, A. D.; Lopez-Serrano, J.;

^†Part of the Dietmar Seyferth Festschrift. Dedicated to Prof. Dietmar

Seyferth, on occasion of his retirement as Editor-in-Chief of Organometallics,

for his outstanding contribution to organometallic chemistry.

*To whom correspondence should be addressed. E-mail: jvs1@

um.es (J.V.), mch@um.es (M.T.C.), dbc@um.es (D.B.). WWW: http://

www.um.es/gqo/.

Ramırez de Arellano, M. C.; Jones, P. G. Organometallics 2002, 21, 272.

Vicente, J.; Abad, J. A.; Hernandez-Mata, F. S.; Rink, B.; Jones, P. G.;

Ramírez de Arellano, M. C. Organometallics 2004, 23, 1292. Vicente, J.;

Abad, J. A.; Lopez-Serrano, J.; Jones, P. G. Organometallics 2004, 23, 4711.

Vicente, J.; Abad, J. A.; Martínez-Viviente, E.; Jones, P. G. Organometallics

2002, 21, 4454. Vicente, J.; Arcas, A.; Fernandez-Hernandez, J. M.; Bautista,

D.; Jones, P. G. Organometallics 2005, 24, 2516. Vicente, J.; Chicote, M. T.;

ꢀ

€

(1) Vicente, J.; Abad, J. A.; Fortsch, W.; Jones, P. G.; Fischer, A. K.

ꢀ

Organometallics 2001, 20, 2704.

Vicente-Hernandez, I.; Bautista, D. Inorg. Chem. 2007, 46, 8939.

2010 American Chemical Society

Published on Web 08/04/2010 pubs.acs.org/Organometallics

5694 Organometallics, Vol. 29, No. 21, 2010

Vicente et al.

Recently, we have described some aryl palladium com-

plexes ortho-functionalized with a β-enaminone substituent

and their reactivity toward isocyanides. The functionalized

aryl ligand was designed with the hope that novel types of

pincer complexes would result upon the insertion of unsatu-

rated molecules into the Pd-C_arylbond and that novel

reactivity patterns could be found caused by the severe

restrictions imposed on the coordination sphere of the metal

by the tridentate ligand. Our expectations were more than

fulfilled since, by reacting these aryl complexes with isocya-

nides under different reaction conditions, not only C,N,O-

pincer but also bridging iminoacyl derivatives, related to

each other through acid/base processes, were obtained.⁸

These findings prompted us to study the reactivity of the

same starting materials toward CO and alkynes.

complexes, are assumed to take place through acylpalladium

intermediates. Their outstanding significance is mainly

based on the fact that they have given access, both at

laboratory and industrial levels, to valuable products such

as alcohols, aldehydes, carboxylic acids, anhydrides, acid

fluorides, esters, or amides and to a variety of heterocycles

including lactones, lactams, oxazoles, thiazoles, and imida-

zoles, as compiled in some recent reviews.²⁵Although most

carbonylation reactions have been carried out with alkyl

derivatives, a few carbonylation products of arylpalladium-

(II) complexes have been reported.^{1,3,5,8,9,12,13,15,16,26}

On the other hand, although the reactions of alkynes with

metal complexes have led to an enormous amount and

variety of complexes resulting from the coordination of the

alkyne in various manners or its insertion into different

M-X (X = H, C, S, P, etc.) bonds, only a few examples

are known in which the alkyne reacts with the ligands present

in the complex. In particular, only three complexes have been

characterized by X-ray crystallography, in which DMAD

inserts into the C-H or S-H bond of chelating diphos-

phanylmethanide,²⁷σ-ferrocenyl,²⁸or bridging hydrosulfide²⁹

ligands, respectively, none of them containing palladium.

Carbonylation reactions incorporate carbon monoxide,

the currently most important C₁building block, into differ-

ent organic substrates. These reactions, usually carried out in

the presence of a nucleophile and catalyzed by palladium

ꢀ

(3) Vicente, J.; Abad, J. A.; Lopez-Saez, M. J.; Fortsch, W.; Jones,

€

P. G. Organometallics 2004, 23, 4414.

ꢀ

(4) Vicente, J.; Abad, J. A.; Lopez-Serrano, J.; Clemente, R.; Ramırez

de Arellano, M. C.; Jones, P. G.; Bautista, D. Organometallics 2003, 22,

4248.

(24) (a) Holton, R. A. Tetrahedron Lett. 1977, 18, 355. (b) Yamamoto,

Y.; Yamazaki, H. Inorg. Chim. Acta 1980, 41, 229. (c) Barr, N.; Dyke, S. F.;

Quessy, S. N. J. Organomet. Chem. 1983, 253, 391. (d) O'Sullivan, R. D.;

Parkins, A. W. J. Chem. Soc., Chem. Commun. 1984, 1165. (e) Ryabov,

A. D. Synthesis 1985, 233. (f) Ryabov, A. D.; Sakodinskaya, I. K.; Dvor-

yantsev, S. N.; Eliseev, A. V.; Yatsimirsky, A. K.; Kuz'mina, L. G.; Struchkov,

Y. T. Tetrahedron Lett. 1986, 27, 2169. (g) Wu, G.; Rheingold, A. L.; Geib,

S. J.; Heck, R. F. Organometallics 1987, 6, 1941. (h) Wu, G.; Rheingold,

A. L.; Heck, R. F. Organometallics 1987, 6, 2386. (i) Dupont, J.; Pfeffer, M.;

Rotteveel, M. A.; De Cian, A.; Fischer, J. Organometallics 1989, 8, 1116.

(j) Beydoun, N.; Pfeffer, M. Synthesis 1990, 729. (k) Maassarani, F.; Pfeffer,

M.; Borgne, G. L. Organometallics 1990, 9, 3003. (l) Pfeffer, M. Recl. Trav.

Chim. Pays-Bas 1990, 109, 567. (m) Beydoun, N.; Pfeffer, M.; Decian, A.;

Fischer, J. Organometallics 1991, 10, 3693. (n) Dupont, J.; Pfeffer, M.;

Theurel, L.; Rotteveel, M. A.; Decian, A.; Fischer, J. New J. Chem. 1991, 15,

551. (o) Ryabov, A. D.; Sakodinskaya, I. K.; Yatsimirsky, A. K. J. Organo-

met. Chem. 1991, 406, 309. (p) Pfeffer, M. Pure Appl. Chem. 1992, 64, 335.

(q) Pfeffer, M.; Sutter, J. P.; Rotteveel, M. A.; Decian, A.; Fischer, J.

Tetrahedron 1992, 48, 2427. (r) Pfeffer, M.; Sutter, J. P.; Decian, A.; Fischer,

J. Organometallics 1993, 12, 1167. (s) Wensbo, D.; Eriksson, A.; Jeschke, T.;

Annby, U.; Gronowitz, S.; Cohen, L. A. Tetrahedron Lett. 1993, 34, 2823.

(t) Larock, R. C.; Doty, M. J.; Cacchi, S. J. J. Org. Chem. 1995, 60, 3270.

(u) Spencer, J.; Pfeffer, M.; Kyritsakas, N.; Fischer, J. Organometallics 1995,

14, 2214. (v) Negishi, E.; Coperet, C.; Ma, S. M.; Mita, T.; Sugihara, T.; Tour,

J. M. J. Am. Chem. Soc. 1996, 118, 5904. (w) Fagnola, M. C.; Candiani, I.;

Visentin, G.; Cabri, W.; Zarini, F.; Mongelli, N.; Bedeschi, A. Tetrahedron

Lett. 1997, 38, 2307. (x) Dyker, G.; Markwitz, H. Synthesis 1998, 1750.

(y) Park, S. S.; Choi, J. K.; Yum, E. K.; Ha, D. C. Tetrahedron Lett. 1998, 39,

627. (z) Ma, C. R.; Liu, X. X.; Yu, S.; Zhao, S.; Cook, J. M. Tetrahedron

Lett. 1999, 40, 657. (aa) Catellani, M.; Motti, E.; Ghelli, S. Chem. Commun.

2000, 2003. (bb) Kadnikov, D. V.; Larock, R. C. Org. Lett. 2000, 2, 3643.

ꢀ

(5) Vicente, J.; Abad, J. A.; Lopez-Serrano, J.; Jones, P. G.; Najera,

C.; Botella-Segura, L. Organometallics 2005, 24, 5044.

(6) Vicente, J.; Abad, J. A.; Shaw, K. F.; Gil-Rubio, J.; Ramırez de

Arellano, M. C.; Jones, P. G. Organometallics 1997, 16, 4557.

(7) Vicente, J.; Chicote, M. T.; Martınez-Martınez, A. J.; Bautista, D.

Organometallics 2009, 28, 5915.

(8) Vicente, J.; Chicote, M. T.; Martınez-Martınez, A. J.; Jones, P. G.;

Bautista, D. Organometallics 2008, 27, 3254.

(9) Vicente, J.; Saura-Llamas, I.; Garcıa-Lopez, J. A.; Bautista, D.

ꢀ

Organometallics 2009, 28, 448.

(10) Vicente, J.; Saura-Llamas, I.; Grunwald, C.; Alcaraz, C.; Jones,

€

P. G.; Bautista, D. Organometallics 2002, 21, 3587.

(11) Vicente, J.; Saura-Llamas, I.; Turpın, J.; Ramırez de Arellano,

M. C.; Jones, P. G. Organometallics 1999, 18, 2683.

(12) Vicente, J.; Saura-Llamas, I.; Turpın, J.; Bautista, D.; Ramırez

de Arellano, C.; Jones, P. G. Organometallics 2009, 28, 4175.

ꢀ

(13) Vicente, J.; Saura-Llamas, I.; Garcıa-Lopez, J. A.; Calmuschi-

Cula, B.; Bautista, D. Organometallics 2007, 26, 2768.

(14) Vicente, J.; Abad, J. A.; Martınez-Viviente, E.; Jones, P. G.

Organometallics 2003, 22, 1967.

(15) Vicente, J.; Abad, J. A.; Frankland, A. D.; Ramırez de Arellano,

M. C. Chem.;Eur. J. 1999, 5, 3066.

(16) Vicente, J.; Abad, J. A.; Frankland, A. D.; Ramırez de Arellano,

M. C. Chem. Commun. 1997, 959.

(17) Vicente, J.; Abad, J. A.; Gil-Rubio, J. J. Organomet. Chem. 1992,

436, C9. Vicente, J.; Abad, J. A.; Gil-Rubio, J.; Jones, P. G. Inorg. Chim.

ꢀ

Acta 1994, 222, 1. Vicente, J.; Abad, J. A.; Fernandez-de-Bobadilla, R.;

Jones, P. G.; Ramírez de Arellano, M. C. Organometallics 1996, 15, 24.

Vicente, J.; Abad, J. A.; Gil-Rubio, J. Organometallics 1996, 15, 3509.

Vicente, J.; Abad, J. A.; Martínez-Viviente, E.; Ramírez de Arellano, M. C.;

ꢀ

Jones, P. G. Organometallics 2000, 19, 752. Vicente, J.; Abad, J. A.; Lopez-

(cc) Vicente, J.; Arcas, A.; Fernandez-Hernandez, J. M.; Bautista, D.

Organometallics 2001, 20, 2767. (dd) Roesch, K. R.; Larock, R. C.

J. Org. Chem. 2001, 66, 412. (ee) Zhang, H. M.; Larock, R. C. Org. Lett.

2001, 3, 3083. (ff) Zhang, H. F.; Hussain, I.; Brust, M.; Cooper, A. I. Chem.

Commun. 2006, 2539.

Pelaez, B.; Martínez-Viviente, E. Organometallics 2002, 21, 58.

(18) Vicente, J.; Abad, J. A.; Gil-Rubio, J.; Jones, P. G. Organome-

tallics 1995, 14, 2677. Vicente, J.; Saura-Llamas, I.; Palin, M. G.; Jones, P. G.

J. Chem. Soc., Dalton Trans. 1995, 2535. Vicente, J.; Saura-Llamas, I.;

Ramírez de Arellano, M. C. J. Chem. Soc., Dalton Trans. 1995, 2529.

Vicente, J.; Abad, J. A.; Bergs, R.; Jones, P. G.; Ramírez de Arellano, M. C.

Organometallics1996, 15, 1422. Vicente, J.; Martínez-Viviente, E.; Fernandez-

Rodriguez, M.-J.; Jones, P. G. Organometallics 2009, 28, 5845.

(19) Vicente, J.; Abad, J. A.; Bergs, R.; Ramırez de Arellano, M. C.;

Martınez-Viviente, E.; Jones, P. G. Organometallics 2000, 19, 5597.

Vicente, J.; Abad, J. A.; Lopez-Saez, M.-J.; Jones, P. G. Organometallics

2010, 29, 409.

€

(25) Brennfuhrer, A.; Neumann, H.; Beller, M. Angew. Chem., Int.

Ed. 2009, 48, 4114. Veige, A. S. Polyhedron 2008, 27. Trzeciak, A. M.;

Ziozkowski, J. J. Coord. Chem. Rev. 2005, 249, 2308. Barnard, C. F. J.

Organometallics 2008, 27, 5402.

(26) Dupont, J.; Pfeffer, M.; Daran, J. C.; Jeannin, Y. Organometal-

lics 1987, 6, 899. Cinellu, M. A.; Gladiali, S.; Minghetti, G. J. Organomet.

Chem. 1989, 363, 401. Negishi, E.; Zhang, Y.; Shimoyama, I.; Wu, G. J. Am.

Chem. Soc. 1989, 111, 8018. Dupont, J.; Pfeffer, M. J. Chem. Soc., Dalton

Trans. 1990, 3193. Suzaki, Y.; Osakada, K. Organometallics 2003, 22,

2193. Lindsell, W. E.; Palmer, D. D.; Preston, P. N.; Rosair, G. M.; Jones,

R. V. H.; Whitton, A. J. Organometallics 2005, 24, 1119. Komine, N.;

Tsutsuminai, S.; Hirano, M.; Komiya, S. J. Organomet. Chem. 2007, 692,

4486. Sergeev, A. G.; Spannenberg, A.; Beller, M. J. Am. Chem. Soc. 2008,

130, 15549.

ꢀ

(20) Vicente, J.; Arcas, A.; Fernandez-Hernandez, J. M.; Bautista, D.

Organometallics 2008, 27, 3978.

(21) Vicente, J.; Abad, J. A.; Lopez-Saez, M. J.; Jones, P. G. Orga-

ꢀ

nometallics 2006, 25, 1851.

(22) Vicente, J.; Abad, J. A.; Lopez-Saez, M.-J.; Jones, P. G. Chem.;

Eur. J. 2010, 16, 661.

ꢀ

(23) Vicente, J.; Abad, J. A.; Lopez-Saez, M. J.; Jones, P. G. Angew.

ꢀ

(27) Ruiz, J.; Quesada, R.; Riera, V.; Castellano, E.; Piro, O. Orga-

Chem., Int. Ed. 2005, 44, 6001.

nometallics 2004, 23, 175.

Article

Herein we report a family of palladium complexes bear-

Organometallics, Vol. 29, No. 21, 2010 5695

oxygen or moisture. Melting points were determined on a

Reichert apparatus and are uncorrected. Elemental analyses

were carried out with a Carlo Erba 1106 microanalyzer. The

molar conductivities were measured with a CRISON micro CM

2200 conductimeter on ca. 5 ꢀ 10^-4M solutions in acetone. IR

spectra were recorded on a Perkin-Elmer 16F PC FT-IR spec-

trometer with Nujol mulls between polyethylene sheets. NMR

spectra were recorded in Varian 200, 300, or 400 NMR spectro-

meters. The NMR assignments were performed, in some cases,

with the help of APT, HMQC, and HMBC experiments.

Schemes 1, 2 and 5 show the atom numbering used in the

NMR assignments. CO (Air Products), HOTf, PPh₃, XyNC,

^tBuNC, tmeda, bpy, ^tBubpy (Fluka), NH₂Me, AgClO₄(Sigma-

Aldrich), DMAD (Alfa Aesar), Hpic (Probus), NH₃(Carburos

ing monocoordinate or C,N,O-pincer benzoyl ligands,

which result from the insertion of CO into the Pd-C_aryl

bond of some β-enaminone-substituted aryl complexes

under different reaction conditions. Complexes with a

monocoordinate benzoyl ligand spontaneously lose CO at

room temperature: slowly in the solid state and faster in

solution. The current interest in acyl complexes resides in

the fact that some of them behave as CO-releasing mole-

cules (CORMs), which are relevant in view of the versatile

properties of CO and its recently recognized participation in

important biological processes causing antioxidative, vaso-

dilator, anti-inflammatory, antiapoptotic, and antiproli-

ferative effects.^30,31Additionally, decarbonylation of acyl

complexes by thermal or photochemical means has been

reported to afford aryl or perfluoroalkyl complexes not

accessible through more conventional ways.³²As far as we

are aware, the complexes described here are the first acyl

C,N,O-pincer derivatives of any metal.^33,34The crystal

structures we describe include the first palladium example

of a very small family of complexes bearing a bridging acyl

ligand^35-39and a dipalladium complex with a bridging

N,N⁰-tmeda ligand, of which only a few precedents are

known,⁴⁰including one of palladium.⁴¹

ꢀ

Metalicos), MeCN, and dmso (SDS) were obtained from com-

mercial sources. [Pd₂(dba)₃] dba (“Pd(dba)₂”),⁴⁴[PdI{C₆H₄-

3_∧

{NHC(Me)CHC(O)Me}-2}(N N)] (N^∧N = tbbpy, tmeda), and

[Pd{C,C-C₆H₄{NHdC(Me)CHC(O)Me}-2}(tmeda)]OTf⁸were

prepared as reported in the literature. The solvents were distilled

before use.

Synthesis of [PdI{C(O)C₆H₄{NHC(Me)CHC(O)Me}-2}(N^∧N)]

[N^∧N = Bubpy (1a), tmeda (1b)]. CO was bubbled for 5 min

through a solution of [PdI{C₆H₄{NHC(Me)CHC(O)Me}-2}-

(N^∧N)] (for 1a, N^∧N = 4,4⁰-di-tert-butyl-2,2⁰-dipyridyl =

^tBubpy, 300 mg, 0.44 mmol; for 1b, N^∧N = N,N,N⁰,N⁰-tetramet-

hylethylenediamine = tmeda, 600 mg, 1.15 mmol) in CH₂Cl₂

(3 mL), and the solution was stirred under a CO atmosphere for

16 (1a) or 18 (1b) h. Upon the addition of cold Et₂O (25 mL,

0 °C; for 2b under a CO atmosphere) a suspension formed, which

was stirred in a water/ice bath (0 °C) for 5 (1a) or 15 (1b) min and

filtered. The solid collected was washed with Et₂O (3 ꢀ 3 mL)

and dried by suction to give 1a or 1b as a yellow solid. 1b was

stored at 4 °C under CO atmosphere.

We also report that dimethylacetylenedicarboxylate

(DMAD) inserts into the C-H bond of the β-enaminone

substituent instead of into the C-Pd bond. The attack of

DMAD on various β-enaminones has been reported

recently.^42,43In addition, we have found that the resulting

complex inserts an isocyanide into the Pd-C bond, which, in

turn, undergoes a photooxygenation process giving rise to an

unprecedented palladium pincer derivative and acetic acid.

1a. Yield: 260 mg, 83%. Mp: 157 °C. H NMR (400 MHz,

CDCl₃, 25 °C): δ 1.420 (s, 9 H, ^tBu), 1.423 (s, 9 H, ^tBu), 1.92 (s, 3

H, Me⁸), 2.00 (s, 3 H, Me¹¹), 4.93 (s, 1 H, H⁹), 7.03 (d, 1 H, Ar,

³J_HH= 7 Hz), 7.26 (m, 1 H, Ar), 7.39 (“t”, 1 H, Ar, J_HH

Experimental Section

7 Hz), 7.43 (d, 1 H, ^tBubpy, ³J_HH= 6 Hz), 7.46 (d, 1 H, ^tBubpy,

³J_HH= 6 Hz), 7.93 (s, 1 H, ^tBubpy), 7.97 (s, 1 H, tbbpy), 8.00 (d,

1 H, Ar, ³J_HH= 7 Hz), 8.32 (d, 1 H, ^tBubpy, ³J_HH= 6 Hz), 9.25

General Procedures. When not stated, the reactions were

carried out without precautions to exclude light or atmospheric

(d, 1 H, Bubpy, J_HH= 6 Hz), 12.81 (br, 1 H, NH). ¹³C{¹H}

NMR (100 MHz, CDCl₃): δ 21.2 (Me⁸), 28.6 (Me¹¹), 30.3 (Me,

^tBu), 30.4 (Me, ^tBu), 35.3 (CMe₃), 35.4 (CMe₃), 96.5 (C⁹), 117.6

(CH, tbbpy) 118.4 (CH), 123.1 (CH), 123.8 (CH), 126.0 (CH),

127.7 (CH), 130.0 (CH), 131.2 (CH), 136.5 (C), 138.8 (C), 150.1

(CH), 151.9 (CH), 153.4 (C), 154.8 (C), 160.6 (C⁷), 162.9 (C),

163.1 (C), 194.7 (C¹⁰), 224.1 (C¹²). IR (cm^-1): ν(CdO) 1652.

Anal. Calcd for C₃₀H₃₆N₃O₂IPd: C, 51.19; H, 5.15; N, 5.97.

Found: C, 50.90; H, 5.45; N, 6.11.

(28) Onitsuka, K.; Yoshida, T.; Adachi, T.; Yoshida, T.; Sonogashira,

K. Chem. Lett. 1995, 233.

(29) Kaneko, Y.; Suzuki, T.; Isobe, K. Organometallics 1998, 17, 996.

(30) Alberto, R.; Motterlini, R. Dalton Trans. 2007, 1651.

(31) Hartinger, C. G.; Dyson, P. J. Chem. Soc. Rev. 2009, 38, 391.

(32) King, R. G.; Bisnette, M. B. J. Organomet. Chem. 1964, 2, 1651.

(33) https://scifinder.cas.org/

(34) Cambridge Structural Database, version 5.30; Cambridge Crystal-

lographic Data Centre: Cambridge, U.K., November 2008, Updated Septem-

ber 2009; www.ccdc.cam.ac.uk.

(35) Acha, F.; Ciganda, R.; Garralda, M. A.; Hernandez, R.;Ibarlucea,

L.; Pinilla, E.; Torres, M. R. Dalton Trans. 2008, 4602. Acha, F.; Garralda,

M. A.; Hernandez, R.; Ibarlucea, L.; Pinilla, E.; Torres, M. R.; Zarandona, M.

Eur. J. Inorg. Chem. 2006, 3893.

(36) Mason, M. R.; Song, B.; Han, Y.; Hu, X. Inorg. Chim. Acta 2008,

361, 3332.

(37) Schweiger, M. J.; Nagel, U.; Beck, W. J. Organomet. Chem. 1988,

355, 289.

(38) Funaioli, T.; Cavazza, C.; Marchetti, F.; Fachinetti, G. Inorg.

Chem. 1999, 38, 3361.

(39) Mason, M. R.; Song, B.; Kirschbaum, K. J. Am. Chem. Soc.

2004, 126, 11812.

1b. Yield: 530 mg, 84%. Mp: 98 °C. H NMR (400 MHz,

CDCl₃, 25 °C): δ 2.03 (s, 3 H, C⁸), 2.10 (s, 3 H, Me¹¹), 2.45-2.96

(various m, 4 H, CH₂, tmeda), 2.53 (br s, 6 H, Me, tmeda), 2.59

(br s, 6 H, Me, tmeda), 5.31 (s, 1 H, H⁹), 6.98 (d, 1 H, Ar, ³J_HH

8 Hz), 7.29 (t, 1 H, Ar, ³J_HH= 7 Hz), 7.36 (td, 1 H, Ar, ³J_HH= 8

Hz, ⁴J_HH= 1 Hz), 8.43 (d, 1 H, Ar, ³J_HH= 7 Hz), 12.70 (s, 1 H,

NH). ¹³C{¹H} NMR (100 MHz, CDCl₃, 25 °C): δ 21.0 (Me⁸),

29.4 (Me¹¹), 48.9 (Me, tmeda), 50.0 (Me, tmeda), 57.7 (CH₂,

tmeda), 61.5 (CH₂, tmeda), 99.7 (C⁹), 125.0 (CH, Ar), 126.4

(CH, Ar), 131.1 (CH, Ar), 134.1 (C, Ar), 135.0 (CH, Ar), 135.2

(C, Ar), 160.0 (C⁷), 195.7 (C¹⁰), 222.3 (C¹²). IR (cm^-1): ν(CdO)

1628. Anal. Calcd for C₁₈H₂₈N₃O₂IPd: C, 39.18; H, 5.11; N,

7.62. Found: C, 38.55; H, 4.99; N, 7.49.

Synthesis of [{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-

2}₂(μ-tmeda)] (2). To a suspension of [Pd{C,C-C₆H₄{NHd

C(Me)CHC(O)Me}-2}(tmeda)]OTf⁸(530 mg, 0.97 mmol) in

acetone (5 mL) was added tmeda (0.15 mL, 1.0 mmol), and

after 5 min of stirring, CO was bubbled through the reaction

(40) Kheradmandan, S.; Fox, T.; Schmalle, H. W.; Venkatesan, K.;

Berke, H. Eur. J. Inorg. Chem. 2004, 2004, 3544. Lee, H. K.; Lam, T. S.;

Lam, C. K.; Li, H. W.; Fung, S., M. New J. Chem. 2003, 27, 1310.

(41) Skupov, K. M.; Marella, P. R.; Simard, M.; Yap, G. P. A.; Allen,

N.; Conner, D.; Goodall, B. L.; Claverie, J. P. Macromol. Rapid

Commun. 2007, 28, 2033.

(42) Moradi, S.; Rajabi Mehr, F.; Baharvand, A.; Rostami, C.

Iranian J. Chem. Chem. Eng. 2008, 27, 17.

ꢀ

(43) Simunek, P.; Peskova, M.; Bertolasi, V.; Lycka, A.; Machacek,

C. Eur. J. Org. Chem. 2004, 2004, 5055. Ali, A. A.; Winzerberg, K. N. Aust.

J. Chem. 2005, 58, 870.

(44) Takahashi, Y.; Ito, S.; Sakai, S.; Ishii, Y. J. Chem. Soc., Chem.

Commun. 1970, 1065.

5696 Organometallics, Vol. 29, No. 21, 2010

Vicente et al.

mixture for 10 min. An orange solution initially formed, which

converted into a suspension within a few minutes. The suspen-

sion was further stirred under a CO atmosphere for 6 h and

concentrated under vacuum (1 mL), and H₂O (25 mL) was

added. The suspension was filtered, and the solid collected was

washed with Et₂O (3 ꢀ 5 mL) and dried by suction to give 2 as an

orange solid. Yield: 268.8 mg, 76%. Mp: 170 °C (dec). ¹H NMR

(400 MHz, CDCl₃, 25 °C): δ 1.91 (s, 3 H, Me¹¹), 2.25 (s, 3 H,

Me⁸), 2.69 (s, 6 H, Me, tmeda), 3.39 (s, 2 H, CH₂), 4.97 (s, 1 H,

Synthesis of PPN[Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)-

Me}-2}}Cl] (5a). To a suspension of 3 (100 mg, 0.16 mmol) in

CHCl₃(10 mL) was added (PPN)Cl (186.6 mg, 0.33 mmol). The

reaction mixture was stirred for 5 h and filtered through a short

pad of Celite. The solution was concentrated under vacuum

(1 mL), and cold Et₂O (0 °C, 20 mL) was added. After 15 min of

stirring in an ice/water bath the suspension was filtered and the

solid collected was washed with Et₂O (3 ꢀ 5 mL), recrystallized

from CH₂Cl₂/Et₂O, and dried first by suction and then in an

oven at 70 °C for 8 h to give 5a as a yellow solid. Yield: 253 mg,

88%. Mp: 184 °C (dec). ¹H NMR (400 MHz, CDCl₃, 25 °C): δ

1.90 (s, 3 H, Me¹¹), 2.19 (s, 3 H, Me⁸), 4.85 (s, 1 H, H⁹), 6.59 (m,

1 H, Ar), 7.13 (d, 1 H, Ar, ³J_HH= 7.5 Hz), 7.06 (m, 1 H, Ar), 7.30

(d, 1 H, Ar, ³J_HH= 7 Hz), 7.41-7.51 (various m, 24 H, ortho- þ

meta-PPN), 7.67 (m, 6 H, para-PPN). ¹³C{¹H} NMR (75 MHz,

CDCl₃, 25 °C): δ 24.2 (Me⁸), 28.1 (Me¹¹), 102.2 (C⁹), 119.7 (CH,

Ar), 121.1 (CH, Ar), 122.6 (CH, Ar), 126.7 (dd, ipso-C, PPN,

¹J_CP= 108 Hz, ³J_CP= 2 Hz), 129.4 (m, ortho-PPN), 130.6 (CH,

Ar), 131.8 (m, meta-PPN), 133.8 (para-PPN), 140.4 (C), 157.0

(C), 162.3 (C⁷), 185.5 (Me¹⁰), 212.4 (Me¹²). ³¹P{¹H} NMR (162

MHz, CDCl₃, 25 °C): δ 21.2. Λ_M= 135 Ω^-1cm²mol^-1(5.49 ꢀ

10^-4mol L^-1). IR (cm^-1): ν(CdO), 1661. Anal. Calcd for

C₄₈H₄₁ClN₂O₂P₂Pd: C, 65.39; H, 4.69; N, 3.18. Found: C,

65.26; H, 4.92; N, 3.23. Crystals suitable for an X-ray diffraction

study were obtained by slow diffusion on n-pentane into a

solution of 5a in CH₂Cl₂.

H⁹), 6.78 (t, 1 H, Ar, ³J_HH= 7.5 Hz), 7.10 (d, 1 H, Ar, ³J_HH

7.5 Hz), 7.22 (td, 1 H, Ar, ³J_HH= 7.5 Hz, ⁴J_HH= 1.5 Hz), 7.36

(dd, 1 H, Ar, ³J_HH= 7.5 Hz, ⁴J_HH= 1.5 Hz). ¹³C{¹H} NMR

(100 MHz, CDCl₃, 25 °C): δ 24.3 (Me⁸), 27.9 (Me¹¹), 51.2 (Me,

tmeda), 60.2 (CH₂), 103.2 (C⁹), 120.6 (CH, Ar), 122.7 (CH, Ar),

122.9 (CH, Ar), 132.1 (CH, Ar), 139.8 (C), 157.1 (C), 164.2 (C⁷),

185.6 (C¹⁰), 216.3 (C¹²). IR (cm^-1): ν(CdO), 1653. Anal. Calcd

for C₃₀H₃₈N₄O₄Pd₂: C, 49.29; H, 5.24; N, 7.66. Found: C, 48.85;

H, 5.13; N, 7.93. FAB^þMS: (m/z, %) 732.0 [M^þ, 8], 423.0

[{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-2}{tmeda} - 1

H}^þ, 84]. Crystals suitable for an X-ray diffraction study were

obtained by slow diffusion of n-pentane into a CH₂Cl₂solution

of 2.

Synthesis of [Pd₂{μ-O,C,N,O⁰-{OdCC₆H₄{NC(Me)CHC-

(O)Me}-2}₂}] (3). CO was bubbled through a suspension of

[Pd{C,C-C₆H₄{NHdC(Me)CHC(O)Me}-2}(tmeda)]OTf⁸(800

mg, 1.47 mmol) in acetone (10 mL) for 15 min. HOTf (130 μL,

1.49 mmol) was added, and the stirring was continued for 1 h

while the reaction mixture was kept under a CO atmosphere.

Acetone (50 mL) was added to the resulting suspension, and the

mixture was filtered through a short pad of Celite. The solution

was concentrated under vacuum to dryness, the residue was

stirred with acetone (5 mL), and the suspension was filtered. The

solid collected was washed with acetone (3 ꢀ 5 mL) and dried by

suction to give a brown-red solid containing 3 with traces of

colloidal palladium, which were removed by treating the crude

product with MeCN (70 mg, 1.7 mmol) in acetone (15 mL),

filtering the resulting solution through a short pad of Celite,

concentrating under vacuum to dryness, stirring the residue with

acetone, filtering the suspension, washing the solid with Et₂O,

and drying the solid by suction. Yield: 407 mg, 90%. Mp: 177 °C

(dec). ¹H and ¹³C NMR spectra could only be measured in

dmso-d₆solution and coincide with those of 6g in the same

solvent. IR (cm^-1): ν(CdO), ν(CdC), 1604, 1567, 1549, 1519.

Anal. Calcd for C₂₄H₂₂N₂O₄Pd₂: C, 46.85; H, 3.60; N, 4.55.

Found: C, 46.31; H, 3.48; N, 4.42. Crystals of 3 suitable for an

X-ray diffraction study were obtained by slow diffusion of Et₂O

into a CHCl₃solution of complex 6f.

Synthesis of Me₄N[Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC-

(O)Me}-2}}Cl] (5b). To a suspension of 3 (55.5 mg, 0.09 mmol)

in acetone (20 mL) was added anhydrous (Me₄N)Cl (35.5 mg,

0.32 mmol). The reaction mixture was stirred for 1.5 h and

filtered through a short pad of Celite. The solution was con-

centrated under vacuum (2 mL), and cold Et₂O (0 °C, 20 mL)

was added. The suspension was filtered, and the solid collected

was recrystallized from CH₂Cl₂and Et₂O and dried first by

suction and then in an oven at 70 °C under vacuum for 10 h to

give 5b as a yellow solid. Yield: 53.2 mg, 71%. Mp: 192 °C (dec).

¹H NMR (400 MHz, CDCl₃, 25 °C): δ 1.87 (s, 3 H, Me¹¹), 2.25

(s, 3 H, Me⁸), 3.49 (s, 12 H, NMe₄), 4.89 (s, 1 H, H⁹), 6.71 (t, 1 H,

Ar, ³J_HH₃= 7.5 Hz), 7.13 (d, 1 H, Ar, ³J_HH= 7.5 Hz), 7.18 (t, 1

H, Ar, J_HH= 7.5 Hz), 7.25 (d, 1 H, Ar, J_HH= 7.5 Hz).

¹³C{¹H} NMR (100 MHz, CDCl₃, 25 °C): δ 24.5 (Me⁸), 28.3

(Me¹¹), 56 (NMe₄), 102.8 (C⁹), 120.3 (CH, Ar), 122.3 (CH, Ar),

122.5 (CH, Ar), 131.9 (CH, Ar), 139.6 (C), 157.3 (C), 163.4 (C⁷),

185.5 (C¹⁰), 214.4 (C¹²). Λ_M= 118 Ω^-1cm²mol^-1(9.40 ꢀ 10^-4

mol L^-1). IR (cm^-1): ν(CdO), 1654. Anal. Calcd for

C₁₆H₂₃ClN₂O₂Pd: C, 46.06; H, 5.56; N, 6.71. Found: C, 45.82;

H, 5.84; N, 6.68.

Synthesis of [{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-

2}L] [L = ^tBuNC (6a), XyNC (6b), PPh₃(6c), MeNH₂(6d), NH₃

(6e), MeCN (6f), dmso (6g)]. To a suspension of 3 (for 6a, 6b,

80 mg, 0.13 mmol; for 6c, 150 mg, 0.24 mmol; for 6d, 160 mg,

0.26 mmol; for 6e, 90 mg, 0.15 mmol; for 6f, 77 mg, 0.13 mmol;

for 6g 34 mg, 0.06 mmol) in acetone (6a-c, 15 mL) or CH₂Cl₂

(for 6d, 5; for 6e, 10; for 6f, 0.5; for 6g, 2 mL) was added the

appropriate L ligand (for 6a, ^tBuNC, 24.9 μL, 0.26 mmol; for 6b,

XyNC, 34.1 mg, 0.26 mmol; for 6c, PPh₃, 127.7 mg, 0.49 mmol;

for 6d, MeNH₂8 M in abs. EtOH, 77.8 μL, 0.62 mmol; for 6e,

NH₃was bubbled for 10 min; for 6f, MeCN, 15 mg, 0.37 mmol;

for 6g, dmso, 36 mg, 0.46 mmol). The reaction mixture was

stirred for 3 h (6a, b), 5 h (6c), 2 h (6d, 6e under NH₃atmo-

sphere), or 10 min (6f, 6g). In the cases of 6b and 6c a suspension

formed, which was concentrated under vacuum (2 mL). For 6b,

the suspension was filtered, and the solid collected was washed

with acetone (1 mL) and Et₂O (5 mL) and dried by suction, while

for 6c, Et₂O (20 mL) was added, the suspension was filtered, and

the solid collected was recrystallized form CH₂Cl₂/Et₂O and

dried in an oven at 65 °C for 10 h. For 6f n-hexane (20 mL) was

added, the resulting suspension was stirred in an ice-water bath

for 15 min, allowed to stand at -20 °C overnight, and filtered,

and the solid was collected and dried under nitrogen. For 6g the

Synthesis of Bu₄N[{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC-

(O)Me}-2}₂(μ-OH)] (4). To a suspension of 3 (33 mg, 0.05

mmol) in CH₂Cl₂(3 mL) was added (Bu₄N)OH (0.05 mL, 1 M

solution in MeOH). After 30 min of stirring the resulting solu-

tion was concentrated under vacuum to 1 mL, Et₂O (20 mL) was

added, and the resulting suspension was filtered. The brown

solid collected was dissolved in CH₂Cl₂(1 mL) and filtered

though a short pad of anhydrous MgSO₄, and the solution was

dropped into stirred n-hexane (20 mL). The suspension was

filtered and the solid was dried by suction to give 4 as a yellow

powder. Yield: 30 mg, 69%. Mp: 176 °C. ¹H NMR (400 MHz,

CDCl₃, 25 °C): δ 0.87 (t, 6 H, CH₃, NBu₄, ³J_HH= 7.2 Hz), 1.37

(m, 4 H, CH₂, NBu₄), 1.53 (m, 4 H, CH₂, NBu₄), 1.80 (s, 3 H,

C¹¹), 2.18 (s, 3 H, Me⁸), 3.45 (m, 4 H, CH₂, NBu₄), 4.79 (s, 1 H,

H⁹), 6.67 (t, 1 H, Ar, ³J_HH= 7.0 Hz), 7.07-7.14 (m, 2 H, Ar),

7.35 (d, 1 H, Ar, J_HH= 6.8 Hz). ¹³C{¹H} NMR (100 MHz,

CDCl₃, 25 °C): δ 13.8 (Me, NBu₄), 19.8 (CH₂, NBu₄), 24.2 (CH₂,

NBu₄), 24.7 (Me⁸), 28.1 (Me¹¹), 58.7 (CH₂, NBu₄), 102.4 (C⁹),

120.0 (CH, Ar), 121.5 (CH, Ar), 122.2 (CH, Ar), 131.4 (CH, Ar),

140.0 (C), 158.2 (C), 162.2 (C⁷), 185.6 (C¹⁰), 217.4 (C¹²). Λ_M

140 Ω^-1cm²mol^-1(6.13 ꢀ 10^-4mol L^-1). IR (cm^-1): ν(CdO),

1666. Anal. Calcd for C₄₀H₅₉N₃O₅Pd₂: C, 54.92; H, 6.80; N,

4.80. Found: C, 54.66; H, 7.20; N, 4.87.

Article

Organometallics, Vol. 29, No. 21, 2010 5697

reaction mixture was concentrated to dryness, the oily residue

was stirred with n-pentane at 0 °C for 15 min, the resulting

suspension was filtered, and the solid collected was washed with

n-pentane (2 mL) and dried with a nitrogen stream and then in an

oven under vacuum at 70 °C for 10 h. In all other cases, the

reaction mixture was filtered through a short pad of Celite and

the solution was concentrated under vacuum to dryness (6a, 6d)

or to 2 mL (6e). The oilyresidue was stirred with n-pentane (6a, 5;

6d, 20 mL) in an ice-water bath for 15 min, the suspension was

filtered, and the solid collected was washed with cold n-pentane

(6a, 2 ꢀ 1; 6d, 3 ꢀ 3 mL) and dried by suction. For 6e, the result-

ing suspension was stirred at 0 °C for 15 min and filtered, and the

solid washed with Et₂O (5 mL) and dried by suction.

H, Me⁸), 2.46 (s br, 3 H, NH₃), 4.97 (s, 1 H, H⁹), 6.82 (m, 1 H,

Ar), 7.23-7.29 (m, 2 H, Ar), 7.35-7.37 (m, 1 H, Ar). ¹³C{¹H}

NMR (75 MHz, CD₂Cl₂, 25 °C): δ 25.5 (Me⁸), 28.0 (C(O)Me),

103.3 (CH), 121.0 (CH, Ar), 123.0 (CH, Ar), 123.2 (CH, Ar),

133.0 (CH, Ar), the quaternary carbons are not observed

because of the scarce solubility of 6e. IR (cm^-1): ν(NH) 3357,

3306, 3145; ν(CdO), 1650. Anal. Calcd for C₁₂H₁₄N₂O₂Pd: C,

44.40; H, 4.35; N, 8.63. Found: C, 44.43; H, 4.32; N, 8.56.

Crystals suitable for an X-ray diffraction study were obtained by

slow evaporation of a solution of the complex in CH₂Cl₂.

6f: yellow powder. Yield: 83 mg, 92%. Mp: 114 °C (dec). ¹H

NMR (300 MHz, CDCl₃, 25 °C): δ 2.00 (s, 3 H, Me¹¹), 2.33 (s,

6 H, Me⁸þ MeCtN), 5.00 (s, 1 H, H⁹), 6.81 (t, 1 H, Ar, ³J_HH

8 Hz), 7.19-7.27 (various m, 2 H, Ar), 7.42 (d, 1 H, Ar, ³J_HH= 8

Hz). ¹³C{¹H} NMR (75 MHz, CDCl₃, 25 °C): δ 1.87 (MeCtN),

25.0 (Me⁸), 28.0 (Me¹¹), 103.3 (C⁹), 116.4 (MeCtN), 120.5 (CH,

Ar), 123.0 (CH, Ar), 123.4 (CH, Ar), 132.6 (CH, Ar), 138.4 (C),

157.9 (C), 164.2 (C⁷), 185.9 (C¹⁰), 211.5 (C¹²). IR (cm^-1):

ν(CdO), 1659; ν(CC) þ ν(CN) þ ν(CO), 1585, 1547, 1519.

Anal. Calcd for C₁₄H₁₄N₂O₂Pd: C, 48.23; H, 4.05; N, 8.03.

Found: C, 47.95; H, 4.25; N, 8.03.

6a: yellow powder. Yield: 78 mg, 76%. Mp: 127 °C. ¹H NMR

(400 MHz, CDCl₃, 25 °C): δ 1.59 (s, 9 H, ^tBu), 2.0 (s, 3 H, Me¹¹),

2.30 (s, 3 H, Me⁸), 5.01 (s, 1 H, H⁹), 6.82 (td, 1 H, Ar, ³J_HH

7 Hz, ⁴J_HH= 1 Hz), 7.15 (d, 1 H, Ar, ³J_HH= 8 Hz), 7.24 (ddd,

1 H, Ar, ³J_HH= 8 Hz, ³J_HH= 7 Hz, ⁴J_HH= 1 Hz), 7.38 (dd,

1 H, Ar, ³J_HH= 8 Hz, ⁴J_HH= 1 Hz). ¹³C{¹H} NMR (75 MHz,

CDCl₃, 25 °C): δ 24.7 (Me⁸), 27.8 (Me¹¹), 30.0 (CMe₃), 57.6

(CMe₃), 103.1 (C⁹), 120.8 (CH, Ar), 123.0 (CH, Ar), 123.7 (CH,

Ar), 132.5 (CH, Ar), 139.0 (C), 157.1 (C), 164.2 (C⁷), 185.3 (C¹⁰),

212.5 (C¹²). IR (cm^-1): ν(CtN), 2198; ν(CdO), 1660. Anal.

Calcd for C₁₇H₂₀N₂O₂Pd: C, 52.25; H, 5.16; N, 7.17. Found: C,

52.20; H, 5.38; N, 7.13.

6g 0.5H₂O: deep yellow powder. Yield: 37 mg, 85%. Mp: 103

°C. ¹H NMR (400 MHz, CDCl₃, 25 °C): δ 1.66 (s, 1 H, H₂O),

2.02 (s, 3 H, C¹¹), 2.36 (s, 3 H, Me⁸), 3.21 (s, 6 H, dmso), 5.07 (s,

1 H, H⁹), 6.85 (t, 1 H, Ar, ³J_HH= 7.6 Hz), 7.20 (d, 1 H, Ar, ³J_HH

= 7.6 Hz), 7.27 (td, 1 H, Ar, ³J_HH= 7.6 Hz, ⁴J_HH= 1.2 Hz),

7.43 (d, 1 H, Ar, ³J_HH= 7.5 Hz); (400 MHz, dmso-d₆, 25 °C) δ

1.92 (s, 3 H, Me¹¹), 2.31 (s, 3 H, Me⁸), 5.11 (s, 1 H, H⁹), 6.88 (t,

6b: yellow powder. Yield: 79.4 mg, 70%. Mp: 184 °C. H

NMR (300 MHz, CDCl₃, 25 °C): δ 2.02 (s, 3 H, Me¹¹), 2.33 (s, 3

H, Me⁸), 2.52 (s, 6 H, Me, Xy), 5.06 (s, 1 H, H⁹), 6.80 (td, 1 H, Ar,

³J_HH= 8 Hz, ⁴J_HH= 1 Hz), 7.11 (d, 2 H, meta-Xy, ³J_HH= 7

Hz), 7.16-7.30 (various m, 3 H, Ar þ ortho-Xy), 7.40 (dd, 1 H,

1 H, Ar, J_HH= 6.5 Hz), 7.29 (d, 1 H, Ar, J_HH= 6.5 Hz),

7.34-7.38 (m, 2 H, Ar). ¹³C{¹H} NMR (50 MHz, CDCl₃,

25 °C): δ 24.8 (Me⁸), 28.1 (Me¹¹), 42.5 (Me, dmso), 103.9 (C⁹),

120.8 (CH, Ar), 123.3 (CH, Ar), 124.2 (CH, Ar), 133.3 (CH, Ar),

138.4 (C), 157.1 (C), 164.2 (C⁷), 186.7 (C¹⁰), the (C(O)Pd)

resonance (C¹²) is not observed; (100 MHz, dmso-d₆, 25 °C) δ

24.4 (Me⁸), 27.7 (Me¹¹), 103.5 (C⁹), 121.1 (2 CH, Ar), 123.3 (CH,

Ar), 133.6 (CH, Ar), 137.9 (C), 156.5 (C), 164.5 (C), 185.4 (C¹⁰),

213.3 (C¹²). IR (cm^-1): ν(CdO), 1658, ν(SdO), 1101.⁴⁵Anal.

Calcd for C₁₄H₁₈NO_3.5PdS: C, 42.60; H, 4.60; N, 3.55; S, 8.12.

Found: C, 42.88; H, 4.35; N, 3.60; S, 7.98.

Ar, J_HH= 8 Hz, J_HH= 2 Hz). ¹³C{¹H} NMR (75 MHz,

CDCl₃, 25 °C): δ 18.7 (Me, Xy), 24.7 (Me⁸), 27.8 (Me¹¹), 103.2

(C⁹), 120.8 (CH, Ar), 123.0 (CH, Ar), 123.9 (CH, Ar), 126.2

(ipso-C, Xy), 127.9 (meta-Xy), 129.5 (para-Xy), 132.7 (CH, Ar),

135.9 (C, ortho-Xy), 138.9 (Pd-CNXy), 148.0 (C), 157.2 (C),

164.1 (C⁷), 185.6 (C¹⁰), 212.5 (C¹²). IR (cm^-1): ν(CtN), 2181;

ν(CdO), 1666. Anal. Calcd for C₂₁H₂₀N₂O₂Pd: C, 57.48; H,

4.59; N, 6.38. Found: C, 57.31; H, 4.68; N, 6.44. Crystals suitable

for an X-ray diffraction study were obtained by slow diffusion

on n-pentane into a solution of 6b in CHCl₃.

Synthesis of (Z)-[PdI{C₆H₄{NHC(Me)C{C(CO₂Me)dCH-

(CO₂Me)}{C(O)Me}}-2}(tmeda)] (7Z). To a solution of [PdI-

{C₆H₄{NHC(Me)CHC(O)Me}-2}(tmeda)] (553 mg, 1.06 mmol)

in CHCl₃(10 mL) was added dimethylacetylenedicarboxylate

(DMAD, 130 μL, 1.06 mmol). The reaction mixture was stirred

at room temperature for 10 h and concentrated under vacuum

to dryness. The residue was dissolved in CH₂Cl₂(1 mL), Et₂O

(20 mL) was added, and the suspension was stirred at 0 °C for

20 min and then filtered. The solid collected upon filtration was

washed with Et₂O (4 ꢀ 1.5 mL) and dried by suction to give 7Z

as a pale orange solid contaminated with a small amount of the

E isomer (molar ratio 20:1), which could not be removed after

repeated recrystallizations or by chromatography. Yield: 591

mg, 86%. Mp: 153-154 °C (dec). ¹H NMR (400 MHz, CDCl₃,

25 °C): δ 2.05 (s, 3 H, Me⁸), 2.24 (s, 3 H, Me¹¹), 2.37 (s, 3 H, Me,

tmeda), 2.57 (s, 3 H, Me, tmeda), 2.62 (s, 3 H, Me, tmeda), 2.68

(s, 3 H, Me, tmeda), 2.40-3.30 (several m, 4 H, CH₂, tmeda),

3.78 (s, 3 H, Me^{14 or 17}), 3.84 (s, 3 H, Me^{14 or 17}), 6.15 (s, 1 H, H¹⁵),

6c H₂O: yellow powder. Yield: 242 mg, 86%. Mp: 213 °C. ¹H

NMR (300 MHz, CDCl₃, 25 °C): δ 1.53 (s, 2 H, H₂O), 1,74 (s, 3

H, Me¹¹), 2.32 (s, 3 H, Me⁸), 4.98 (s, 1 H, H⁹), 6.76 (td, 1 H, Ar,

³J_HH= 8 Hz, ⁴J_HH= 1 Hz), 7.15 (d, 1 H, Ar, ³J_HH= 8 Hz),

7.21-7.26 (various m, 2 H, Ar), 7.33-7.44 (various m, 9 H,

PPh₃), 7.60-7.65 (various m, 6 H, PPh₃). ¹³C{¹H} NMR (100

MHz, CDCl₃, 25 °C): δ 24.4 (d, Me⁸, ⁴J_CP= 4 Hz), 27.4 (Me¹¹),

103.0 (C⁹), 120.8 (d, CH, Ar, J_CP= 4 Hz), 122.6 (CH, Ar),

123.9 (CH, Ar), 128.0 (d, meta-CH, PPh₃, ³J_CP= 11 Hz), 130.1

(d, para-CH, PPh₃, ⁴J_CP= 2 Hz), 131.0 (d, ipso-C. PPh₃, ¹J_CP

46 Hz), 132.3 (CH, Ar), 134.8 (d, ortho-CH, PPh₃, J_CP= 12

Hz), 140.1 (d, C, J_CP= 3 Hz), 156.6 (C), 163.9 (C⁷), 185.2 (C¹⁰),

216.8 (C¹²). ³¹P{¹H} NMR (162 MHz, CDCl₃, 25 °C): δ 35.6. IR

(cm^-1): ν(CdO), 1659. Anal. Calcd for C₃₀H₂₈NO₃PPd: C,

61.29; H, 4.80; N, 2.38. Found: C, 61.37; H, 4.64; N, 2.53. Cry-

stals of 6c suitable for an X-ray diffraction study were obtained

by slow diffusion on n-pentane into a solution of 6c in Et₂O.

6d: yellow powder. Yield: 155 mg, 88%. Mp: 114 °C. ¹H

NMR (400 MHz, CDCl₃, 25 °C): δ 1.96 (s, 3 H, Me¹¹), 2.33 (s, 3

H, Me⁸), 2.71 (t, 3 H, NH₂Me, ³J_HH= 7 Hz), 2.83 (s br, 2 H,

NH₂), 4.97 (s, 1 H, H⁹), 6.83 (m, 1 H, Ar), 7.22-7.27 (m, 2 H,

Ar), 7.42-7.44 (m, 1 H, Ar). ¹³C{¹H} NMR (100 MHz, CDCl₃,

25 °C): δ 25.2 (Me⁸), 28.0 (Me¹¹), 31.3 (NH₂Me), 103.3 (C⁹),

120.6 (CH, Ar), 122.8 (CH, Ar), 123.0 (CH, Ar), 132.6 (CH, Ar),

139.3 (C), 158.0 (C), 163.9 (C⁷), 185.3 (C¹⁰), 219.2 (C¹²). IR

(cm^-1): ν(NH) 3308, 3257 ; ν(CdO), 1654. Anal. Calcd for

C₁₃H₁₆N₂O₂Pd: C, 46.10; H, 4.76; N, 8.27. Found: C, 46.37; H,

4.94; N, 8.29.

6.80 (dd, 1 H, H⁶, ³J_HH= 7Hz, ⁴J_HH= 2 Hz), 6.88 (td, 1 H, H^{4 or 5}

³J_HH= 7 Hz, ⁴J_HH= 2 Hz), 6.91 (td, 1 H, H^{4 or 5}, ³J_HH= 7 Hz,

⁴J_HH= 2 Hz), 7.25 (dd, 1 H, H³, ³J_HH= 7 Hz, ⁴J_HH= 2 Hz),

14.13 (s, 1 H, NH). ¹³C{¹H} NMR (50 MHz, CDCl₃, 25 °C): δ

18.8 (Me⁸), 28.5 (Me¹¹), 48.3 (Me, tmeda), 48.4 (Me, tmeda),

50.6 (Me, tmeda), 50.9 (Me, tmeda), 51.9 (Me^{14 or 17}), 52.4

(Me^{14 or 17}), 58.6 (CH₂, tmeda), 62.0 (CH₂, tmeda), 104.4 (C⁹),

123.1 (CH, Ar), 125.0 (CH, Ar), 125.1 (CH, Ar), 127.3 (C¹⁵),

136.8 (CH, Ar), 141.1 (C^{1 or 2}), 142.0 (C^{1 or 2}), 147.4 (C¹²), 163.3

(C⁷), 165.6 (C^{13 or 16}), 169.1 (C^{13 or 16}), 192.5 (C¹⁰). IR (cm^-1):

6e: yellow powder. Yield: 65 mg, 69%. Mp: 188 °C (dec). ¹H

(45) Vicente, J.; Arcas, A.; Borrachero, M. V.; Molıns, E. M., C.

J. Organomet. Chem. 1989, 359, 127.

NMR (400 MHz, CD₂Cl₂, 25 °C): δ 1.90 (s, 3 H, Me¹¹), 2.32 (s, 3

5698 Organometallics, Vol. 29, No. 21, 2010

_asym(CO₂), 1730. Anal. Calcd for C₂₃H₃₄IN₃O₅Pd: C, 41.49; H,

5.15; N, 6.31. Found: C, 41.09; H, 5.17; N, 6.29. Crystals suitable

for an X-ray diffraction study were obtained by slow diffusion

on n-hexane into a solution of 7Z in acetone.

Vicente et al.

Xy^{a, Mþm}, ³J_HH= 8 Hz), 7.01 (d, 1 H, H^{6, Mþm}, ³J_HH= 8 Hz),

7.07 (s, 1 H, H^{15, M}), 7.14 (t, 1 H, para-Xy^{a, Mþm}, ³J_HH=8 Hz),

7.20 (td, 1 H, H^{5, M}, ³J_HH= 8 Hz, ⁴J_HH= 2 Hz), 7.21 (td, 1 H,

^{5, m}, ³J_HH= 8 Hz, ⁴J_HH= 2 Hz), 7.99 (dd, 1 H, H^{3, M}, ³J_HH

8 Hz, ⁴J_HH= 2 Hz), 8.01 (d, 1 H, H^{3, m}, ³J_HH= 8 Hz, ⁴J_HH= 2

Hz). ¹³C{¹H} NMR (100 MHz, CDCl₃, 25 °C, major isomer): δ

18.6 (Me, Xy^a), 19.3 (Me, Xy^b), 19.5 (Me, Xy^b), 22.7 (Me⁸), 27.5

(Me¹¹), 52.0 (Me^{14 or 17}), 52.9 (Me^{14 or 17}), 106.9 (C⁹), 121.4 (C⁶),

122.8 (para-Xy^b), 123.3 (C⁴), 125.3 (C³), 126.7 (ortho-Xy^b),

126.9 (ortho-Xy^b), 127.3 (meta-Xy^b), 127.4 (meta-Xy^aþb),

128.8 (para-Xy^a), 129.7 (C⁵), 131.5 (C¹⁵), 134.5 (ortho-Xy^a),

142.3 (C¹), 144.4 (C¹²), 144.7 (ipso-Xy^a), 153.0 (ipso-Xy^b), 154.9

(C²), 163.8 (C⁷), 166.0 (C¹⁶), 168.1 (C¹³), 178.2 (CNXy^b), 181.4

(C¹⁰). ¹³C resonances assigned to the minor isomer appear

at 23.7 (Me⁸), 28.2 (Me¹¹), 52.4 (Me^{14 or 17}), 53.4 (Me^{14 or 17}),

110.0 (C⁹), 121.6, 123.6, 125.4, 128.2, 128.9, 144.7, 148.6,

152.9, 154.6, 164.3, 165.6, 169.1, 177.3 (CdN), 182.6 (C¹⁰),

but some could not be assigned unambiguously. IR (cm^-1):

ν(CtN), 2169, ν_asym(CO₂), 1716; ν(CdN), 1628. Anal. Calcd

for C₃₅H₃₅N₃O₅Pd: C, 61.45; H, 5.16; N, 6.14. Found: C, 61.08;

H, 5.31; N, 6.20.

Synthesis of (E)-[PdI{C₆H₄{NHC(Me)C{C(CO₂Me)dCH-

(CO₂Me)}C(O)Me}}-2}(tmeda)] (7E). 7Z (201 mg, 0.30 mmol)

was dissolved in toluene (8 mL) and stirred in a Carius tube at

95 °C for 15 h. The resulting suspension was filtered through a

short pad of Celite, the solution was concentrated under vacuum

to dryness, the residue was dissolved in CH₂Cl₂(1 mL), Et₂O

(12 mL) was added, and the resulting suspension was stirred at

0 °C for 10 min. The solid collected upon filtration was washed

with Et₂O (3 ꢀ 1.5 mL) and dried, first by suction and then in an

oven at 75 °C under vacuum for 24 h to give 7E 2H₂O as a

yellow solid. Yield: 72 mg, 36%. Mp: 168 °C (dec). H NMR

(400 MHz, CDCl₃, 25 °C, two conformers: = major,

minor, M:m = 1.2:1): δ 1.54 (s, 4 H, H₂O), 1.84 (s, 3 H, Me^{8, M}),

1.86 (s, 3 H, Me^{8, m}), 2.00 (s, 3 H, Me^{11, M}), 2.08 (s, 3 H, Me^{11, m}),

2.40 (s, 3 H, Me, tmeda^M), 2.41 (s, 3 H, Me, tmeda^m), 2.59 (s, 3

H, Me, tmeda^m), 2.60 (s, 3 H, Me, tmeda^M), 2.68 (s, 3 H, Me,

tmeda^M), 2.70 (s, 3 H, Me, tmeda^Mþm), 2.75 (s, 3 H, Me,

tmeda^m) 2.40-3.30 (several m, 4 H, CH₂, tmeda^Mþm), 3.77

(s, 3 H, Me^{14 or 17, m}), 3.81 (s, 3 H, Me^{14 or 17, M}), 3.82 (s, 3 H,

Synthesis of [Pd{C,N,O-{C(dNXy)C₆H₄{N(dmoc)}-2](CNXy)]

(9). After exposing to sunlight a solution of 8 (23 mg, 0.034

mmol) in a mixture of CHCl₃/n-pentane (1:5, 3 mL, 80 h),

crystals of 9 formed along with some metallic palladium, which

separated from them by adhering to the flask wall. The mother

liquor was decanted, and the crystals were washed with

n-pentane (3 ꢀ 0.5 mL) and dried under vacuum in an oven

(80 °C, 15 h). Further crops of crystals grew from the mother liquor

upon standing in the sunlight; these were treated as above. The

procedure was repeated five times, yielding a total 18 mg (82%)

Me^{14 or 17, m}), 3.85 (s, 3 H, Me^{14 or 17, M}), 6.76 (dd, 1 H, H^{6, m}

³J_HH= 7 Hz, ⁴J_HH= 2 Hz), 6.80 (dd, 1 H, H^{6, M}, ³J_HH= 7 Hz,

⁴J_HH= 2 Hz), 6.85-6.90 (various overlapped td, 4 H, H^{4, Mþm}

^5,Mþm), ³J_HH= 7 Hz, ⁴J_HH= 2 Hz), 7.06 (s, 1 H, H^{15, M}), 7.11

(s, 1 H, H^{15, m}), 7.25 (dd, 1H, H^{3, Mþm}, ³J_HH= 7 Hz, ⁴J_HH= 2

Hz), 14.05 (s, 1 H, NH^m), 14.10 (s, 1 H, NH^M); (400.9 MHz,

CDCl₃, 90 °C) δ 1.79 (s, 3 H, Me⁸), 1.92 (s, 3 H, Me¹¹), 2.25 (s,

3 H, Me, tmeda), 2.53 (s, 3 H, Me, tmeda), 2.63 (s, 6 H, Me,

tmeda), 2.30-3.10 (various m, 4 H, CH₂, tmeda), 3.71 (s, 3 H,

Me^{14 or 17}), 3.78 (s, 3 H, Me^{14 or 17}), 6.70 (m, H⁶), 6.79 (m, 2 H,

H⁴þ H⁵), 6.96 (s, 1 H, H¹⁵), 7.17 (m, 1H, H³), 13.81 (s, 1H, NH).

¹³C{¹H} NMR (50 MHz, CDCl₃, 25 °C): δ 18.0, 18.6 (Me⁸),

27.9, 28.0 (Me¹¹), 48.2 48.6, 50.6, 50.9, 51.8, 52.4, 52.6, 52.8 (Me,

tmeda), 58.58, 58.62, 61.9, 62.1 (CH₂, tmeda), 101.3, 101.5 (C⁹),

122.9, 123.0 (CH, Ar), 124.7, 124.8 (CH, Ar), 124.9, 125.3 (CH,

Ar), 130.1, 132.2 (C¹⁵), 136.98, 137.01 (CH, Ar), 140.9, 141.0,

141.7, 142.18, 142,20, 144.4 (C¹þ C²þ C¹²), 160.6, 161.9, 165.7

(2 C), 168.21, 168.23 (C⁷þ C¹³þ C¹⁶), 191.7, 192.7 (C¹⁰). IR

(cm^-1): ν_asym(CO₂), 1725. Anal. Calcd for C₂₃H₃₈IN₃O₇Pd: C,

39.36; H, 5.46; N, 5.97. Found: C, 39.37; H, 5.13; N, 5.98.

Crystals were obtained by slow diffusion of n-hexane into a

solution of 7E in CH₂Cl₂.

after 150 h of exposure. Mp: >200 °C (dec). H NMR (200

MHz, CDCl₃, 25 °C): δ 2.15 (s, 3 H, Me, Xy^b), 2.16 (s, 3 H, Me,

Xy^b), 2.24 (s, 6 H, Me, Xy^a), 3.01, 3.28 (AB part of an ABX

system, 2 H, H^11aþ11b, ²J_AB= 19.5 Hz, ³J_AX= 7.0 Hz, ³J_BX

1.6 Hz), 3.73 (s, 3 H, CO₂Me), 3.75 (s, 3 H, CO₂Me), 4.19 (X part

of an ABX system, 1 H, H⁷), 6.21 (t, 1 H, para-Xy, ³J_HH= 7 Hz),

6.72 (d, 1 H, meta-Xy^b, ³J_HH= 8 Hz), 6.73 (d, 1 H, meta-Xy^b,

³J_HH= 8 Hz), 6.99 (d, 2 H, meta-Xy^a, ³J_HH= 7 Hz), 7.16 (dd, 1

H, para-Xy, ³J_HH= 7 Hz, ³J_HH= 8 Hz), 7.33 (m, 1 H, H^{3 or 5}),

7.49 (m, 2 H, H⁴þ H^{3 or 5}), 8.34 (d, 1 H, H⁶, Ar, ³J_HH= 8 Hz).

¹³C{¹H} NMR (75 MHz, CDCl₃, 25 °C): δ 18.6 (Me, Xy^a), 19.09

(Me, Xy^b), 19.10 (Me, Xy^b), 31.7 (C¹¹), 46.6 (C⁷), 51.4 (CO₂Me),

52.3 (CO₂Me), 113.0 (C¹⁰), 119.2 (C^{3 or 5}), 123.4 (CH, para-Xy),

125.98 (C, ortho-Xy^b), 126.01 (C, ortho-Xy^b), 126.8 (C, ipso-

Xy^a), 127.46 (C, meta-Xy^a), 127.51 (C, meta-Xy^aþ meta-Xy^b),

127.7 (C²), 129.0 (C^{3 or 5}), 129.1 (CH, para-Xy), 131.6 (C⁴), 134.5

(C, ortho-Xy^a), 141.4 (CtN), 146.2 (C⁶), 148.9 (C¹), 151.6 (C,

ipso-Xy^b), 165.8 (CO₂Me), 166.7 (CdN), 174.6 (CO₂Me), 177.1

(C⁹), 184.9 (C⁸). IR (cm^-1): ν(CtN), 2181, ν(CdN), 1618. Anal.

Calcd for C₃₃H₃₁N₃O₅Pd: C, 60.42; H, 4.76; N, 6.40. Found: C,

60.12; H, 4.73; N, 6.37.

Synthesis of [Pd{C,N,O-{C(dNXy)C₆H₄{NC(Me)dC{C-

(CO₂Me)dCHCO₂Me)}C(O)Me}-2}(CNXy)] (8). To a solu-

tion of 7Z (400 mg, 0.60 mmol) in MeCN (16 mL) was added

AgClO₄(125 mg, 0.60 mmol). A suspension immediately

formed, which was stirred in the dark for 20 min and filtered

through a short pad of Celite. The solution was concentrated

under vacuum (2 mL), a solution of XyNC (158 mg, 1.20 mmol)

in MeCN (5 mL) was added, and the mixture was stirred at room

temperature for 1 h and concentrated under vacuum to dryness.

The residue was stirred with Et₂O (80 mL), the suspension was

filtered, and the solution was concentrated under vacuum to

dryness. The solid residue was recrystallized from CH₂Cl₂(ca.

0.75 mL) and n-pentane (20 mL), washed with n-pentane (3 ꢀ 3

mL), and dried by suction to give orange 8 as a 10:1 mixture of

two isomers, which could not be resolved after recrystallization.

Yield: 361 mg, 88%. Mp: 184 °C. ¹H NMR (400 MHz, CDCl₃,

25 °C, two isomers: ^M= major, ^m= minor, M:m = 10:1): δ 1.84

(s, 3 H, Me^{11, M}), 2.10 (s, 3 H, Me^{11, m}), 2.20 (s, 3 H, Me^{8, M}), 2.22

(s,9H,Me,Xy^aþ Xy^b),2.26(s,3H,Me,Xy^b), 2.43 (s, 3 H, Me^{8, m}),

3.78 (s, 3 H, Me^{14 or 17, M}), 3.80 (s, 3 H, Me^{14 or 17, m}), 3.86 (s,

3 H, Me^{14 or 17, m}), 3.87 (s, 3 H, Me^{14 or 17, M}), 6.14 (s, 1 H, H^{15, m}),

Synthesis of [Pd{C,N,O-{C(dNHXy)C₆H₄{NC(Me)dCH-

{C(CO₂Me)dCH CO₂Me)}C(Me)O}-2}(CNXy)]OTf (10). To

a solution of 8 (24 mg, 0.04 mmol) in CH₂Cl₂(3 mL) was added

HOTf (3 μL, 0.04 mmol). The reaction mixture was stirred for

30 min and concentrated under vacuum to 0.5 mL, and Et₂O

(20 mL) was added. The suspension was filtered, and the solid

collected was washed with Et₂O (2 ꢀ 2 mL) and dried first by

suction and then in a vacuum oven at 70 °C overnight to give

10 0.5H₂O as an orange-red solid. Yield: 21 mg, 70%. Mp:

204 °C. H NMR (400 MHz, CDCl₃, 25 °C): δ 1.86 (s, 3 H,

Me¹¹), 2.21 (s, 6 H, Me, Xy^a), 2.22 (s, 3 H, Me, Xy^b), 2.48 (s, 3 H,

Me, Me⁸), 2.51 (s, 3 H, Me, Xy^b), 3.79 (s, 3 H, Me^{14 or 17}), 3.89 (s,

3 H, Me^{14 or 17}), 6.67 (t, 1 H, para-Xy^b, ³J_HH= 8 Hz), 6.89 (d, 1

H, meta-Xy^b, ³J_HH= 8 Hz), 7.01 (d, 1 H, H³or 6 ³J_HH= 8 Hz),

6.29 (t, 1 H, para-Xy^{b, m}, ³J_HH= 8 Hz), 6.30 (t, 1 H, para-Xy^{b, M}

7.08 (d, 2 H, meta-Xy^a), 7.11 (m, 1 H, H^{4 or 5}), 7.13 (s, 1H, H¹⁵),

³J_HH= 8 Hz), 6.71 (d, 1 H, meta-Xy^{b, Mþm}, ³J_HH= 8 Hz), 6.74

7.25 (t, 1 H, para-Xy^a, J_HH= 8 Hz), 7.45 (dt, 1 H, H^{4 or 5}

(d, 1 H, meta-Xy^{b, Mþm}, ³J_HH= 8 Hz), 6.92 (t, 1 H, H^{4, M}, ³J_HH

³J_HH= 8 Hz, ⁴J_HH= 1 Hz), 8.21 (dd, 1 H, H^{3 or 6}, ³J_HH= 8 Hz,

⁴J_HH= 1 Hz), 12.31 (s br, 1 H, NHXy^b). ¹³C{¹H} NMR

8 Hz), 6.94 (t, 1 H, H^{4, m}, J_HH= 8 Hz), 6.99 (d, 2 H, meta-

Article

Organometallics, Vol. 29, No. 21, 2010 5699

Table 1. Crystal Data and Structure Refinement of Complexes 2, 3, and 5a

formula

731.44

100(2)

triclinic

7.3382(4)

9.4824(6)

11.2464(7)

100.191(2)

97.345(2)

107.542(2)

720.59(8)

₃₀H₃₈N₄O₄Pd₂

C₂₄H₂₂N₂O₄Pd₂

615.24

100(2)

orthorhombic

Fdd2

16.1086(12

24.6965(19)

10.4757(8)

4167.5(5)

1.961

1.762

2432

C₄₈H₄₁ClN₂O₂P₂Pd

881.62

100(2)

monoclinic

P2₁/n

9.2515(6))

29.745(2)

14.9909(11)

100.395(2)

4057.6(5)

1.443

0.645

1808

temperature (K)

cryst syst

space group

a (A)

b (A)

c (A)

R (deg)

β (deg)

γ (deg)

volume (A )

_calcd(Mg m^-3

)

1.686

1.290

370

μ(Mo KR) (mm^-1

F(000)

)

cryst size (mm)

θ range (deg)

no. of reflns coll

0.28 ꢀ 0.16 ꢀ 0.13

1.88 to 28.16

8237

0.32 ꢀ 0.18 ꢀ 0.14

2.46 to 28.43

6504

0.18 ꢀ 0.12 ꢀ 0.07

1.94 to 28.23

46 741

no. of indep reflns/R_int

transmissn

restraints/params

goodness-of-fit on F²

R₁(I > 2σ(I))

3211/0.0130

0.8502-0.7140

0/185

1.188

0.0180

2184/0.0127

0.7905/0.6872

1/147

1.168

0.0158

9435/0.0265

0.9563-0.8928

0/507

1.107

0.0350

wR₂(all reflns)

largest diff

0.0483

0.351/-0.774

0.0412

0.304/-0.647

0.0868

0.886/-0.295

-3

peak/hole (e A

)

Table 2. Crystal Data and Structure Refinement of Complexes 6b, 6c, and 6e

formula

438.79

100(2)

monoclinic

P2₁/c

15.3130(11)

7.7347(5)

15.3771(11)

98.874(2)

1799.5(2)

1.620

1.049

888

₂₁H₂₀N₂O₂Pd

C₃₀H₂₆NO₂PPd

569.89

100(2)

orthorhombic

Pca2(1)

28.719(4)

10.7837(14)

8.0015(11)

2478.1(6)

1.528

C₁₂H₁₄N₂O₂Pd

324.65

100(2)

orthorhombic

P2(1)2(1)2(1)

4.5852(3)

14.8783(11)

16.8496(12)

temperature (K)

cryst syst

space group

a (A)

b (A)

c (A)

R (deg)

β (deg)

γ (deg)

volume (A )

1149.48(14)

1.876

1.605

648

_calcd(Mg m^-3

)

μ(Mo KR) (mm^-1

F(000)

)

0.842

1160

cryst size (mm)

θ range (deg)

no. of rflns coll

0.18 ꢀ 0.14 ꢀ 0.10

2.68 to 28.22

20 006

0.18 ꢀ 0.06 ꢀ 0.05

1.89 to 28.22

15 175

0.20 ꢀ 0.07 ꢀ 0.03

1.83 to 28.16

13 219

no. of indep rflns/R_int

transmissn

restraints/params

goodness-of-fit on F²

R₁(I > 2σ(I))

4168/0.0190

0.9024-0.8337

0/239

1.087

0.0218

5483/0.0681

0.9591-0.8632

9/318

1.044

0.0570

2652/0.0463

0.9534-0.7397

6/168

1.128

0.0371

wR₂(all reflns)

largest diff

0.0520

0.389/-0.306

0.1071

0.837/-1.012

0.0862

1.764/-0.648

-3

peak/hole (e A

)

(100 MHz, CDCl₃, 25 °C): δ 18.4 (Me, Xy^a), 18.9 (Me, Xy^b), 19.0

H, 4.42; N, 4.98; S, 3.80. Found: C, 51.26; H, 4.38; N, 5.05; S, 3.76.

Crystals suitable for an X-ray diffraction study were obtained by

slow diffusion of n-hexane into a solution of 10 in CH₂Cl₂.

(Me, Xy^b), 22.6 (Me⁸), 26.4 (Me¹¹), 52.1 (Me¹⁴

¹⁷), 53.2

(Me^{14 or 17}), 109.2 (C⁹), 120.3 (q, ¹J_CF= 320.1 Hz, CF₃) 122.1

(C^{3 or 6}), 125.3(C^{4 or 5}), 125.5 (CtNoripso-C, Xy^a), 125.9 (C^{3 or 6}),

128.0 (meta-CH, Xy^a), 128.2 (meta-CH,Xy^b), 128.3 (meta-CH,

Xy^b), 129.7 (para-CH, Xy^b), 130.3 (para-CH, Xy^a), 132.1 (C¹⁵),

131.5 (C¹⁵), 134.52 (ortho-C, Xy^b), 134.53 (ortho-C, Xy^b), 134.7

(ortho-C, Xy^a), 135.8 (C⁴or C⁵), 136.7 (C¹or C²), 137.9 (br s,

C),140.8 (ipso-C, Xy^b), 143.2 (C¹²), 158.4 (C^{1 or 2}), 164.0 (C⁷),

165.2 (C^{13 or 16}), 167.0 (C^{13 or 16}), 181.7 (C¹⁰), 216.2 (CNHXy^b).

IR (cm^-1): ν(NH) 3144, ν(CtN), 2195, ν_asym(CO₂), 1722;

ν(CdN), 1634. Anal. Calcd for C₃₆H₃₇F₃N₃O_8.5PdS: C, 51.28;

Synthesis of [Pd{C,N,O-{C(dNXy)C₆H₄{N(dmoc)}-2](CNXy)]

Hpic (11). To a solution of 9 (60 mg, 0.09 mmol) in CHCl₃

(10 mL) was added picric acid (Hpic = HOC₆H₃(NO₂)₃-2,4,6,

22 mg, 0.10 mmol). The reaction mixture was stirred at room

temperature for 3 h and filtered through a short pad of Celite.

The solution was concentrated under vacuum to 1 mL, and Et₂O

(20 mL) was added. The suspension was concentrated under

vacuum to half its volume and filtered. The solid collected was

washed with Et₂O (3 ꢀ 1.5 mL), recrystallized from CH₂Cl₂and

5700 Organometallics, Vol. 29, No. 21, 2010

Table 3. Crystal Data and Structure Refinement of Complexes 7Z, 7E, and 10

Vicente et al.

7E CH₂Cl₂

formula

C₂₃H₃₄IN₃O₅Pd

665.83

100(2)

orthorhombic

Pca2(1)

16.4206(6)

8.4472(3)

38.9101(15)

5397.1(3)

1.639

C₂₄H₃₆Cl₂IN₃O₅Pd

750.76

100(2)

monoclinic

P2(1)/c

12.4477(7)

15.4666(9)

15.6410(9)

94.502(2)

3002.0(3)

1.661

1.861

1496

C₃₆H₃₆F₃N₃O₈PdS

834.14

100(2)

triclinic

8.3200(8)

14.7538(13)

15.9658(15)

112.747(2)

91.600(4)

100.430(4)

1767.1(3)

temperature (K)

cryst syst

space group

a (A)

b (A)

c (A)

R (deg)

β (deg)

γ (deg)

volume (A )

_calcd(Mg m^-3

)

1.568

0.657

852

μ(Mo KR) (mm^-1

F(000)

)

1.867

2656

cryst size (mm)

θ range (deg)

no. of reflns coll

0.32 ꢀ 0.18 ꢀ 0.17

2.41 to 28.18

59 032

0.21 ꢀ 0.18 ꢀ 0.03

1.64 to 28.16

33 737

0.23 ꢀ 0.11 ꢀ 0.05

2.44 to 28.64

21 896

no. of indep reflns/R_int

transmissn

restraints/params

goodness-of-fit on F²

R₁(I > 2σ(I))

12 520/0.0203

0.7419-0.6451

2/619

1.105

0.0230

6943/0.0481

0.9463-0.7378

7/335

1.060

0.0433

8292/0.0410

0.9679/0.8029

2/472

1.185

0.0587

wR₂(all reflns)

largest diff

0.0568

0.797/-0.649

0.0955

1.667/-1.477

0.1204

1.248/-1.676

-3

peak/hole (e A

)

Et₂O, and dried in a vacuum oven at 75 °C for 5 h to give

For complexes 3, 6c, 6e, and 7Z, the absolute structure parameter is

0.04(3), 0.01(4), 0.01(5), and 0.602(11), respectively.⁴⁶Complexes 2,

5a, 6b, 7E, and 10 crystallize in centrosymmetric space groups. For

complex 7Zthe structure was refined as a racemic twin. One methyl is

disordered over two positions (ca. 57:43%). For complexes 7E and

10, the CHCl₃and one of the xylyl groups, respectively, are

disordered over two sites (ca. 64:36% and 56:44%, respectively).

Further details on crystal data, data collection, and refinements are

summarized in the Supporting Information.

11 0.5CH₂Cl₂as a deep yellow solid. Yield: 77 mg (91%). Mp:

170 °C (dec). ¹H NMR (300 MHz, CDCl₃, 25 °C): δ 2.16 (s, 3 H,

Me, Xy^b), 2.18 (s, 3 H, Me, Xy^b), 2.24 (s, 6 H, Me, Xy^a), 2.99,

3.25 (2 H, C¹¹H₂, part AB of an ABX system, ²J_AB= 19.8 Hz,

³J_AX= 7 Hz, ²J_BX= 0 Hz), 3.72 (s, 3 H, CO₂Me), 3.73 (s, 3 H,

CO₂Me), 4.17 (d, 1 H, H⁷, part X of an ABX system), 2.5-3.2 (v

br, OH), 6.21 (t, 1 H, para-Xy^b, J_HH= 8 Hz), 6.71 (d, 1 H,

meta-Xy^b, ³J_HH= 8 Hz), 6.74 (d, 1 H, meta-Xy^b, ³J_HH= 7 Hz),

6.96 (d, 2 H, meta-Xy^a, ³J_HH= 8 Hz), 7.14 (t, 1 H, para-Xy^a,

³J_HH= 8 Hz), 7.34 (ddd, 1 H, H^{4 or 5}, Ar, ⁴J_HH= 1 Hz, ³J_HH

8 Hz), 7.47 (m, 1 H, H^{3 or 6}, Ar), 7.51 (td, 1 H, H^{4 or 5}, Ar, ⁴J_HH

Results and Discussion

1 Hz, ³J_HH= 8 Hz), 8.36 (dd, 1 H, H^{3 or 6}, Ar, ⁴J_HH= 1 Hz,

³J_HH= 8 Hz), 8.87 (br s, 2 H, Ar, pic). ¹³C{¹H} NMR (75 MHz,

CDCl₃, 25 °C): δ 14.0 (Me, Xy^a), 15.2 (Me, Xy^b), 31.7 (C¹¹), 46.5

(C⁷),51.5(CO₂Me), 52.4 (CO₂Me), 113.2 (C^{9 or 10}), 119.3 (C^{3,4,5 or 6}),

123.7 (CH, para-Xy^b), 126.1 (CH, picrate), 126.30 (C, ortho-

Xy^b), 126.33 (C, ortho-Xy^b), 126.7 (br, C, CtN or ipso-Xy^a),

127.5 (C, meta-Xy^a), 127.6 (C, meta-Xy^b), 127.8 (C^{3 or 6}), 129.2

(C^{4 or 5}þ para-Xy^a), 131.9 (C^{3,4,5 or 6}), 134.5 (ortho-Xy^a), 141.1

(br, ortho-C, picrate), 146.2 (C^{1 or 2}), 148.5 (C^{1 or 2}), 151.0 (ipso-

Xy^b), 165.8 (CO₂Me), 167.8 (CdNHXy), 174.4 (CO₂Me), 177.1

(C^{9 or 10}), 184.7 (C⁸). IR (cm^-1): ν(CtN), 2187; ν(CdO), 1743;

ν(CdN), 1689. Anal. Calcd for C_39.5H₃₅ClN₆O₁₂Pd: C, 51.15;

H, 3.80; N, 9.06. Found: C, 51.13; H, 3.43; N, 9.43.

Synthesis. We have recently reported the synthesis of com-

plexes [PdI{C₆H₄{NHC(Me)CHC(O)Me}-2}(N^∧N)] [N^∧N=

tbbpy (A), tmeda (A⁰); Scheme 1] and their reaction with

TlOTf to give [Pd{C,C-C₆H₄{NHdC(Me)CHC(O)Me}-2}-

(N^∧N)]OTf [N^∧N = tbbpy (B), tmeda (B⁰)].⁸When these aryl

palladium complexes were reacted with isocyanides [RNC, R =

^tBu, C₆H₃Me₂-2,6 (Xy)] under different reaction conditions,

insertion of the isocyanide into the Pd-C_arylbond led to a variety

of complexes including bridging iminoacyl, C,N,O-pincer, and

1,2-dihydroquinazolin-4-yl derivatives. These results prompted

us to study the reactivity of the same starting materials toward

CO and alkynes.

X-ray Crystallography. Complexes 2, 3, 5a, 6b, 6c, 6e, 7Z, 7E,

and 10 were measured on a Bruker Smart APEX machine. Data were

collected using monochromated Mo KR radiation in ω scan mode.

Absorption corrections were applied on the basis of multiscans

(program SADABS). The structures were solved by direct methods.

All were refined anisotropically on F². Restraints to local aromatic

ring symmetry or light atom displacement factor components were

applied in some cases. The NH and NH₂hydrogens were refined

freely with DFIX and SADI, respectively; the ordered methyl groups

were refined using rigid groups (AFIX137), and the other hydrogens

were refined using a riding model. For clarity, solvent contents are

omitted here, but are defined in Tables 1-3. Figures 1-7 show the

ellipsoid representations of the structures. Figures 8-11 illustrate

some hydrogen bond interactions. Special features and exceptions:

After bubbling CO through a solution of A or A⁰in a small

volume of CH₂Cl₂for 5 min and keeping the reaction mix-

ture under CO atmosphere for 16-18 h, a color change from

yellow to orange was observed. Addition of cold Et₂O caused

the precipitation of the benzoyl complexes [PdI{C(O)-

C₆H₄{NHC(Me)CHC(O)Me}-2}(N^∧N)] [N^∧N = Bubpy

(1a), tmeda (1b)], resulting from the insertion of CO into

the Pd-C_arylbond, which were isolated in more than 80%

yield. Complex 1b needs to be precipitated and stored under

CO atmosphere because otherwise it undergoes CO deinser-

tion even in the solid state (at an approximate rate of 8%

mol h^-1or 3.5% mol min^-1at 70 or 100 °C, respectively, by

TGA). The process is faster in solution (CDCl₃, 35% mol h^-1

at room temperature, by ¹H NMR). 1a is rather more stable;

it can be stored indefinitely in the solid state and decomposes

(46) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876.

Article

Organometallics, Vol. 29, No. 21, 2010 5701

Scheme 1

after adding water and filtering. The mother liquor was

shown to contain the byproduct [tmedaH₂](OTf)₂(¹H

NMR and elemental analysis). A search of the Cambridge

Crystallographic Database reveals that among the very small

number of dinuclear complexes with bridging tmeda ligands

previously characterized by X-ray diffraction, only one is of

palladium;⁴¹a few derivatives of representative (Li, Be, Al,

Ga, Zn, Sn) and transition (Mn, Co) metals are also

known.³⁴

Various attempts to isolate the monomeric carbonyl com-

plex C by using different solvents (acetone, CH₂Cl₂) and

longer reaction times led always to 2 þ C mixtures in which

we could identify C by both NMR and IR spectroscopy.⁴⁷

The best C:2 molar ratio (2.3:1) was achieved after 24 h of

stirring B in acetone under a CO atmosphere. The carbonyl

complex formed also when CO was bubbled through CH₂Cl₂

solutions of 6f or 6g. However, all attempts to isolate it failed

since in the absence of a CO atmosphere it is unstable and

decomposes readily to give 3. We have also obtained 3 by

reacting 2 with HOTf, but it was best prepared (90% isolated

yield) by reacting B with CO (15 min of bubbling and 1 h of

stirring under CO atmosphere) and 1 equiv of HOTf in

acetone, where 3 precipitates and [tmedaH₂](OTf)₂remains

dissolved. Among the many acyl complexes of Pd previously

known, some of them reported by us,^{1,3,5,9,11,14,15}none bears,

as 3, a symmetric double acyl bridge. Of the few similar iso-

lated complexes (Al,³⁹Ga,³⁶Re,^37,48Ru,³⁸or Ir³⁵), six X-ray

crystal structures have been reported, only three of them

corresponding to benzoyl derivatives.³⁴

Since demetalation of organometallic palladium com-

plexes has opened the way to interesting organic products re-

sulting from different coupling processes,^{3,5,6,9,10,12-14,17,24}

we heated complex 3 in toluene with the hope of obtaining

2-methyl-3-acetyl-4-oxo-1H-1,4-dihydroquinoline. How-

ever, after 24 h of heating at 120 °C in a Carius tube, not only

depalladation but also decarbonylation occurred to give the

previously known⁴⁹indole derivative 2-methyl-3-acetyl-1H-

indole, which was isolated in 50% yield and identified by its

NMR and mass spectra.⁵⁰The same compound was ob-

tained when the complex homologue of B with N^∧N =

^tBubpy⁸(Scheme 1) was refluxed in toluene for 10 h.

Complex 3 is far more reactive than its homologous

iminobenzoyl derivative [{Pd₂{C,N,O-{C(dNXy)C₆H₄-

{NC(Me)CHC(O)Me}-2}₂],⁸in which the iminoacyl bridges

do not split unless it is refluxed in CHCl₃with phosphine or

isocyanide ligands for more than 9 h, and it does not react

with (PPN)Cl under the same reaction conditions. However,

when a suspension of 3 in CH₂Cl₂was treated with

(Bu₄N)OH (1:1), a solution formed from which the dinuclear

complex Bu₄N[{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-

2}₂(μ-OH)] (4) was isolated in 69% yield. The same complex

was isolated, though in lower yield, when 3 was reacted with

in solution at room temperature at an approximate rate of

5% mol h^-1. CO deinsertion in acyl or benzoyl metal

complexes, achieved by thermal or photochemical means,

was reported³²long ago to afford aryl or perfluoroalkyl com-

plexes that were not accessible through more conventional ways.

Additionally, CO-releasing molecules (CORMs) are species of

increasing interest since the versatile properties of CO and its

participation in important biological processes have been re-

cently recognized. In fact, mammals produce CO at a 1-6 μmol

kg^-1day^-1rate, which has been shown to have antioxidative,

vasodilator, anti-inflammatory, antiapoptotic, and antiproli-

ferative effects.³⁰

When CO was bubbled through a suspension of [Pd{C,C-

C₆H₄{NHdC(Me)CHC(O)Me}-2}(tmeda)]OTf⁸(B, Scheme 1)

in acetone, a mixture formed containing [{Pd{C,N,O-{C-

(O)C₆H₄{NC(Me)CHC(O)Me}-2}₂(μ-tmeda)] (2), the car-

bonyl complex [{Pd{C,N,O-{C(O)C₆H₄{NC(Me)CHC(O)-

Me}-2}(CO)] (C), and the dinuclear benzoyl-C,N,O-pincer

complex [Pd₂{μ-O,C,N,O⁰-{OdCC₆H₄{NC(Me)CHC(O)-

Me}-2}₂}] (3). Complex 2 probably forms through (1) the

cleavage of the CH-Pd bond in B and CO coordination to

give I (Scheme 1), (2) migratory insertion of CO followed by

coordination of NH and O and monocoordination of tmeda

to afford II, (3) formation of the dinuclear complex III and

tmeda, and (4) deprotonation of III by tmeda to give 2. This

complex could be better obtained when the same reaction

was carried out in the presence of 1 equiv of tmeda, which

prevents the formation of the carbonyl complex C. In this

case, the solution initially formed converted gradually into a

suspension from which complex 2 was isolated in 76% yield

(47) ¹H NMR (200 MHz, CDCl₃, TMS, 25 °C): δ 2.03 (s, 3 H,

C(O)Me), 2.34 (s, 3 H, MeCN), 5.10 (s, 1 H, CH), 6.88 (t, 1 H, ³J_HH= 7

Hz), 7.14-7.43 (various m obscured by the resonances of 2 in the same

region). IR (cm^-1): ν(CtO) 2107, ν(CdO) 1680.

(48) Lippmann, E.; Robl, C.; Berke, H.; Kaesz, H. D.; Beck, W.

Chem. Ber. 1993, 126, 933.

(49) Sakamoto, T.; Nagano, T.; Kondo, Y.; Yamanaka, H. Synthesis

1990, 215.

(50) ¹H NMR (400 MHz, CDCl₃): δ 2.67 (s, 3 H, Me), 2.75 (s, 3H,

Me), 7.19-7.27 (m, 2H), 7.33 (d, 1H, J_HH= 7.6 Hz), 8.02 (d, 1 H,

³J_HH= 7.6 Hz), 8.86 (s br, 1H, NH). ¹³C{¹H} NMR(75 MHz, CDCl₃): δ

15.5 (Me), 31.3 (Me), 110.8 (CH), 114.6 (C), 120.8 (CH), 122.0 (CH),

122.4 (CH) 126.9 (C), 134.5 (C), 143.7 (C), 194.8 (C(O)Me). EI-MS [m/z,

%]: [M^þ] 173.1, 41; [M^þ- Me] 158.0, 100.

5702 Organometallics, Vol. 29, No. 21, 2010

Vicente et al.

(Bu₄N)F in an attempt to obtain the corresponding fluoro

complex. All attempts to grow single crystals of 4 by the

liquid diffusion method failed, and when we used CH₂Cl₂

and Et₂O, a few crystals of Bu₄N[Pd{C,N,O-{C(O)C₆H₄-

{NC(Me)CHC(O)Me}-2}}Cl] (homologue of complexes 5,

see below) grew instead, probably arising from the presence

of traces of HCl in the chlorinated solvent. Although the

atomic connectivity in the anion could be unambiguously

established, the structure could not be refined because of

disorder in the cation. However, we succeeded with one of its

homologues (5a, see below).

Scheme 2

In most complexes bearing the Pd(II)₂(μ-OH) moiety both

metal atoms are additionally connected by a second bridging

ligand. Only two complexes similar to 4 have been charac-

terized by X-ray diffraction, namely, [{PdMe(1,5-cycloocta-

diene)}₂(μ-OH)]SbF₆⁵¹and [{Pd{bis(2-pyridylmethyl)amine}}₂-

(μ-OH)](OTf)₃.⁵²Crystals of the former were obtained from

the decomposition of [Pd(Me)(OH)(1,5-cyclooctadiene)],

and its synthesis could not be reproduced. The tricationic

derivative, which bears, like 4, a pincer ligand, formed in low

yield by reacting [{Pd(Me){bis(2-pyridylmethyl)amine}]OTf

with B(C₆F₅)₃in CF₃CH₂OH/CH₂Cl₂.

In contrast with the fluoro complex mentioned above, the

homologous chloro derivatives Q[Pd{C,N,O-{C(O)C₆H₄-

{NC(Me)CHC(O)Me}-2}}Cl] (Q = PPN (5a), NMe₄(5b))

are stable and could be isolated in good yield from the re-

actions of 3 with the appropriate chlorides. An attempt to

prepare the bromo complex by reacting 5b with NaBr (1:5, in

acetone, 3 h at room temperature) failed, and the starting

material was quantitatively recovered.

The acyl bridges in 3 were also split by reacting it with

different neutral ligands, under very mild reaction condi-

tions, in stoichiometric amounts (^tBuNC, XyNC, PPh₃) or in

excess (NH₂Me, NH₃, MeCN, dmso) to give [{Pd{C,N,

O-{C(O)C₆H₄{NC(Me)CHC(O)Me}-2}L] (L = CN^tBu (6a),

CNXy (6b), PPh₃(6c), NH₃(6d), NH₂Me (6e), MeCN (6f),

dmso (6g)) (70-90% isolated yields). They are stable in the

solid state, but when we attempted to grow single crystals of

6f, complex 3 crystallized instead. As far as we are aware,

complexes 2-6 are the first complexes of any metal bearing

an acyl-pincer ligand.

We are also interested in studying the insertion reactions of

alkynes into Pd-C_arylbonds, to which field we have made

some contributions.^{3-6,11,12,17-19}Attempts to react the palla-

dium complex A or A⁰with PhCtCPh under different reac-

tion conditions (1:1 or with excess alkyne, in the presence or

not of TlOTf) failed at room temperature or, upon refluxing

in CHCl₃, gave mixtures, which we could not separate.

However, the reaction of A⁰with dimethylacetylenedicar-

boxylate (DMAD, 1:1, 10 h at room temperature in CHCl₃)

allowed us to isolate the complex resulting from the insertion

of the alkyne into the activated CH bond of the β-enaminone

ligand, affording (Z)-[PdI{C₆H₄{NHC(Me)C{C(CO₂Me)d

CH(CO₂Me)}{C(O)Me}-2}}(tmeda)] (7Z, Scheme 2) instead

of the product of insertion into the Pd-C bond. The yield

was very good, but 7Z formed along with traces of its E

isomer, which we could not remove after repeated recrystal-

lizations or by chromatography. Heating the reaction mix-

ture in toluene gave a mixture of [PdI₂(tmeda)], Pd metal,

and 7E. This complex could be isolated from the mixture in

36% yield. According to NMR data, complex 7E forms as a

mixture of two conformers (see the NMR Spectra section).

Attempts to react DMAD with complex A under various

reaction conditions produced mixtures of oily materials,

from which we could not isolate any pure species even after

repeated recrystallization or chromatography. However,

their H NMR spectra show the homologues of 7 to form

along with some impurities and also that the Z isomer, which

forms first, transforms into the E isomer much faster than in

the case of 7.

The insertion of dimethylacetylenedicarboxylate into ali-

phatic C(sp²)-H bonds has been previously found to occur

in β-enaminones, affording the corresponding esters instead

of the expected [4þ2] cycloaddition products.⁴³More re-

cently this reaction, which is said to take several days at room

temperature, has proved to be general.⁴²We found the

reaction of DMAD with the β-enaminone MeC(O)CHdC-

(Me)NHPh (1:1, in CHCl₃at room temperature) to be less

stereospecific and much slower than that with A⁰. Conver-

sion of only 30%, 50%, or 60% of the starting products was

achieved after 12, 24, or 48 h, respectively, giving mixtures

with Z:E = 10-15:1 molar ratios. Z to E conversion is very

slow, and even after 4 days refluxing in chloroform a Z:E =

1:5 molar ratio is attained.

Complex 7E reacted with AgClO₄and XyNC to give the

pincer complex [Pd{C,N,O-{C(dNXy)C₆H₄{NC(Me)C{C-

(CO₂Me)dCHCO₂Me)}C(O)Me}-2}(CNXy)] (8; Scheme 2)

in excellent yield. The reaction was carried out in MeCN in

two steps. The iodo ligand was first removed with AgClO₄,

and then addition of 2 equiv of XyNC afforded complex 8. In

this second step, the replaced tmeda ligand deprotonates the

NH group, favoring the N-coordination of the resulting

imino ligand, while the insertion of XyNC leaves a free

coordination position that allows the coordination of the

carbonyl oxygen atom, giving a C,N,O-pincer complex. This

process is similar to that giving C from B (Scheme 1) and has

also been observed to occur upon the insertion of XyNC.⁸

An attempt to grow single crystals of 8 produced instead,

very slowly, crystals that IR, NMR spectra, and elemental

(51) Klein, A.; Dogan, A.; Feth, M.; Bertagnolli, H. Inorg. Chim.

Acta 2003, 343, 189.

(52) Cao, L.; Jennings, M. C.; Puddephatt, R. J. Dalton Trans. 2009,

5171.

Article

Organometallics, Vol. 29, No. 21, 2010 5703

Scheme 3

Scheme 4

Scheme 5

afford the acetato complex Y, (3) isomerization of Y to form

the pincer complex Y⁰, (4) deprotonation of the NdC(Me)

methyl group by the acetate counterion to give acetic acid and

complex Z, and (5) cyclization to afford 9 through the

hydrocarbonation of the CdCH₂olefinic bond. In the mother

liquor where 9 formed, trace amounts of 8E were observed,

which suggests that only the main isomer 8Z is responsible for

the formation of 9, in agreement with the proposed reaction

pathway (Scheme 3), which would not apply to the E isomer.

To check this proposal, we carried out a reaction by bubbling

dry air through an irradiated solution of 8 in CHCl₃and

collected the effluents in a trap cooled with liquid nitrogen.

Under these reaction conditions the conversion 8 f 9 is much

faster and a 63% or 90% yield was achieved after 10 or 18 h,

respectively. In the effluent the presence of AcOH was de-

tected by IR (two absorptions at 1714 and 1758 cm^-1) and ¹H

NMR (δ 2.10 ppm) spectroscopies.

analyses proved to be of [Pd{C,N,O-[C(dNXy)C₆H₄{N-

(dmoc)}-2](CNXy)] 2CHCl₃(9; Scheme 3), where the imino

substituent dmoc is the cycle 1,2-di(methoxycarbonyl)-3-

oxocyclopent-1-en-4-yl. The conversion of 8 into 9 needs

sunlight or visible-light lamp irradiation, occurs in CHCl₃or

CH₂Cl₂but not in toluene, and is accompanied by some

decomposition to Pd(0). Under these conditions, the best

yield (82%) was obtained after 150 h since decomposition

increased when the reaction time was further extended.

Scheme 3 shows our proposal for the reaction pathway of

this process, which involves (1) formation of an 1,2-dioxe-

tane (X) through the formal [2þ2] cycloaddition of singlet

dioxygen (¹O₂),⁵³(2) O-O and C-C bond cleavage⁵⁴to

Complex 9 is the first complex of any metal with this

ligand. We have reported a similar photooxygenation reac-

tion involving the transformation of an acetylacetonato into

an acetato ligand (Scheme 4).⁵⁵However, these results differ

in that, in the present case, replacement of the acetato ligand

€

(53) Adam, W.; Reinhardt, D.; Saha-Moller, C. R. Analyst 1996, 121,

1527. Mayer, A.; Neuenhofer, S. Angew. Chem., Int. Ed. Engl. 1994, 33,

1044.

(54) Matsumoto, M.; Tanimura, M.; Akimoto, T.; Watanabe, N.;

Ijuin, H. K. Tetrahedron Lett. 2008, 49, 4170.

5704 Organometallics, Vol. 29, No. 21, 2010

Vicente et al.

to give the pincer complex Y⁰is preferred to the formation of

the acetato-bridged complex obtained when the cleaved

ligand is acetylacetonato.

By reacting complex 8 or 9 with the stoichiometric amount

of triflic or picric acid, complex Pd{C,N,O-{C(dNHXy)C₆

H₄{NC(Me)C{C(CO₂Me)dCHCO₂Me)}C(O)Me}-2}(CN-

Xy)]OTf (10) or [Pd{C,N,O-{C(dNXy)C₆H₄{N(dmoc)}-2]-

(CNXy)] Hpic (11, Scheme 5, Hpic = picric acid) was ob-

tained, respectively. Complexes 10 and 11 were prepared

with the purpose of measuring their X-ray crystal structures,

which we could not get for their precursors. We succeeded

with complex 10. In the case of 11 the connectivity of the

atoms could be located (see SI), in spite of the refinement

being far from satisfactory, which can be attributed to low

diffraction, the presence of a very badly disordered triflic

acid (possibly over three positions), and a region of disor-

dered solvent (probably dichloromethane), which could not

be modelled. NMR studies prove their structures in solution,

showing that while 10 is a cationic complex in which the

imino N atom is protonated, in agreement with the X-ray

diffraction study, 11 behaves as an adduct formed between 9

and picric acid through a hydrogen bond (see NMR Spectra

section).

Figure 1. Thermal ellipsoid representation plot (50% probabil-

ity) of complex 2. Selected bond lengths (A) and angles (deg):

Pd(1)-C(1) 1.9594(17), Pd(1)-N(1) 2.0296(13), Pd(1)-O(1)

2.1197(12), Pd(1)-N(2) 2.1428(14), C(1)-C(2) 1.500(2), C(2)-

C(3) 1.405(2), N(1)-C(3) 1.412(2), N(1)-C(8) 1.334(2), C(8)-

C(9) 1.403(2), C(9)-C(10) 1.398(2), O(1)-C(10) 1.278(2), O(2)-

C(1) 1.213(2); C(1)-Pd(1)-N(1) 83.18(6), N(1)-Pd(1)-O(1)

91.87(5), C(1)-Pd(1)-N(2) 94.74(6), O(1)-Pd(1)-N(2) 90.26(5).

X-ray Crystal Structures. The crystal structures of com-

plexes 2 (Figure 1), 3 (Figure 2), 5a (Figure 3), 6b (Figure 4),

6c, 6e, 7Z (Figure 5), 7E (Figure 6), and 10 (Figure 7) have

been determined by X-ray diffraction. The figures corre-

sponding to the structures of 6c and 6e are included in the

Supporting Information. In all of them, the palladium atom

is in a distorted square, perfectly planar, environment.

Complexes 2 and 6 and the anion in 5a, bearing the same

C,N,O-acyl-pincer ligand, display many commonalities.

Thus, the C-Pd-N bond angle in the five-membered ring

is always narrower (83.18(16)-84.67(18)°) than the N-

Pd-O angle (89.65(6)-95.47(15)°) in the more flexible six-

membered ring. The C-C, C-N, and C-O bond distances

within the pincer skeleton are very similar, but the Pd-N one

is sensitive to the nature of the ligand in trans position, sug-

gesting the trans influence to decrease in the series PPh₃>

XyNC > tmeda ≈ NH₃> Cl > O (μ-acyl). The Pd(1)-C(1)

bond distance (1.923(2)-1.9646(18) A) is somewhat shorter

than that found in other palladium complexes having, trans

to the benzoyl group, other ligands of low trans influence (Cl,

I, N, or O donor, 1.959-2.011 A),³⁴probably because of the

Figure 2. Thermal ellipsoid representation plot (50% probabil-

ity) of complex 3. Selected bond lengths (A) and angles (deg):

pincer nature of our complexes. The Pd-N_tmedabond dis-

tance in 2 (2.0296(13) A) is shorter than that found in the

only other palladium complex bearing a bridging tmeda

ligand⁴¹(2.1428(14) vs 2.228(13) A) because of the greater

trans influence of P- with respect to N-donor ligands. The

acetyl PdO(1)dC(10) bond distances in 2, 3, 5a, 6b, 6c, 6e,

and 10 (1.284(6)-1.262(6) A) and the benzoyl PdO(2)dC(1)

distance in 3 (1.240(3) A) are longer than the benzoyl

Pd(1)-C(1) 1.923(2), Pd(1)-N(1) 2.0095(17), Pd(1)-O(1)

2.0812(17), Pd(1)-O(2)#1 2.0535(14), C(1)-C(2) 1.480(3), C(2)-

C(3) 1.406(3), N(1)-C(3) 1.413(3), N(1)-C(8) 1.333(3), C(8)-

C(9) 1.411(3), C(9)-C(10) 1.393(3), O(1)-C(10) 1.274(3), O(2)-

C(1) 1.240(3); C(1)-Pd(1)-N(1) 84.07(8), C(1)-Pd(1)-O(2)#1

97.47(7), N(1)-Pd(1)-O(1) 94.83(7), O(2)#1-Pd(1)-O(1)

83.90(6),C(1)-O(2)-Pd(1)#1 132.87(14), O(2)-C(1)-Pd(1)

129.14(17).

PdC(1)dO(2) lengths (1.210(2)-1.220(7) A) because of the

weakening of the CdO bond caused by coordination in the

former complexes. In 3, the Pd(1)-O(1) bond distance

molecule of the alkyne into the C(sp²)-H bond of the

β-ketoiminato ligand. The palladium atom is in a distorted

square-planar environment with narrow N-Pd-N angles

(84.13(15)-84.75(10)°) caused by the small bite of the tmeda

ligand. The bond distances and angles in 7E and the two

different molecules present in the asymmetric unit of 7Z are

not significantly different with the exception of the Pd-I

bond distance, which is somewhat shorter in 7E (2.5793(4) vs

(2.0812(17) A) is longer than Pd(1)-O(02A) (2.0535(14) A)

because of the greater trans influence of C- than N-donor

ligands.

The crystal structures of complexes 7Z and 7E show that

the reaction between [PdI{C₆H₄{NHC(Me)CHC(O)Me}-

2}(tmeda)]⁸and DMAD produces the insertion of one

2.5828(3) and 2.5844(3) A). The longer Pd-N bond dis-

tances trans to aryl (7Z: Pd(1)-N(1) 2.186(2), Pd(2)-N(4)

(55) Vicente, J.; Arcas, A.; Bautista, D.; Shul’pin, G. B. J. Chem. Soc.,

Dalton Trans. 1994, 1505.

Article

Organometallics, Vol. 29, No. 21, 2010 5705

Figure 5. Thermal ellipsoid representation plot (50% probability)

Figure 3. Thermal ellipsoid representation plot (50% probabil-

ity) of the anion in complex 5a. Selected bond lengths (A) and

of complex 7Z. Selected bond lengths (A) and angles (deg): Pd(1)-

C(11) 1.995(3), Pd(1)-N(2) 2.124(2), Pd(1)-N(1), 2.186(2), Pd-

(1)-I(1) 2.5828(3), N(3)-C(17) 1.332(4), O(1)-C(19) 1.243(4),

C(17)-C(18) 1.411(4), C(18)-C(22), 1.491(5), C(22)-C(25)

1.332(5); C(11)-Pd(1)-N(2) 91.93(10), N(2)-Pd(1)-N(1)

84.38(9), C(11)-Pd(1)-I(1) 89.11(8), N(1)-Pd(1)-I(1) 94.59(7),

C(25)-C(22)-C(18) 120.4(3), C(25)-C(22)-C(23) 121.4(3), C-

(18)-C(22)-C(23) 117.7(3), C(22)-C(25)-C(26) 124.7(3).

angles(deg):Pd(1)-C(1) 1.948(2), Pd(1)-N(1) 2.0210(18), Pd(1)-

O(1) 2.1464(15), Pd(1)-Cl(1)2.3245(6), C(1)-C(2) 1.518(3),

C(2)-C(3) 1.403(3), N(1)-C(3) 1.411(3), N(1)-C(8) 1.337(3),

C(8)-C(9) 1.401(3), C(9)-C(10) 1.408(3), O(1)-C(10) 1.269(3),

O(2)-C(1) 1.211(3); C(1)-Pd(1)-N(1) 84.12(8), N(1)-Pd(1)-

O(1) 89.65(6), C(1)-Pd(1)-Cl(1) 95.29(7), O(1)-Pd(1)-Cl(1)

90.94(4).

Figure 4. Thermal ellipsoid representation plot (50% probabil-

ity) of complex 6b. Selected bond lengths (A) and angles (deg):

Figure 6. Thermal ellipsoid representation plot (50% probabi-

lity) of complex 7E. Selected bond lengths (A) and angles (deg):

Pd(1)-C(1) 1.9646(18), Pd(1)-N(1) 2.0422(14), Pd(1)-O(1)

2.1228(12), Pd(1)-C(13) 1.9543(17), C(1)-C(2) 1.500(2), C(2)-

C(3) 1.401(2), N(1)-C(3) 1.417(2), N(1)-C(8) 1.334(2), C(8)-

C(9) 1.404(2), C(9)-C(10) 1.403(2), O(1)-C(10) 1.275(2),

O(2)-C(1) 1.210(2); C(1)-Pd(1)-N(1) 83.89(6), N(1)-Pd(1)-

O(1) 91.96(5), C(13)-Pd(1)-C(1) 91.02(7), C(13)-Pd(1)-O(1)

93.28(6).

Pd(1)-C(11) 2.004(4), Pd(1)-N(1) 2.182(4), Pd(1)-N(2)

2.111(3), Pd(1)-I(1) 2.5793(4), N(3)-C(12) 1.429(5), N(3)-

C(17) 1.344(5), O(1)-C(19) 1.239(5), C(17)-C(18) 1.385(6),

C(18)-C(19) 1.454(6), C(18)-C(22) 1.493(6), C(22)-C(23)

1.521(6), C(22)-C(25) 1.322(6), C(25)-C(26) 1.473(7); C(11)-

Pd(1)-N(2) 92.21(15), N(2)-Pd(1)-N(1) 84.13(15), C(11)-

Pd(1)-I(1) 88.08(11), N(1)-Pd(1)-I(1) 95.63(10), C(25)-C(22)-

C(18) 125.1(4),C(25)-C(22)-C(23) 115.9(4),C(18)-C(22)-C(23)

119.0(4), C(22)-C(25)-C(26) 125.5(4).

2.173(2); 7E: Pd(1)-N(1) 2.182(4) A) compared to those

trans to iodo (7Z: Pd(1)-N(2) 2.124(2), Pd(2)-N(5)

2.132(3); 7E: Pd(1)-N(2) 2.111(3) A) are attributable to

the greater trans influence of the aryl ligand.

Nonclassical C-H O, C-H Cl, or C-H I hydro-

3 3 3

gen bonds are also observed. Thus, in 5a two C-H Cl

3 3 3

In the crystal structure of 10 the bond distances and angles

within the five- and six-membered rings constituting the

pincer fragment are almost equal to those in the complex [Pd-

{C,N,O-{C(dNHXy)C₆H₄{NC(Me)CHC(Me)O}-2}(CNXy)]-

OTf previously reported by us,⁸while the structural para-

meters regarding the alkenyl fragment do not differ signifi-

cantly from those found in complexes 7E and 7Z.

interactions make the molecules arrange into chains parallel

to the a axis (Figure 8). Classical N-H O hydrogen bonds

3 3 3

are observed in complexes 7Z and 7E (intramolecular,

Figures 9 and 10, respectively). In 7Z the two independent

molecules in the asymmetric unit are connected by two

C-H O interactions, giving dimers; additionally, two

3 3 3

C-H I interactions connect one of the two independent

5706 Organometallics, Vol. 29, No. 21, 2010

Vicente et al.

Figure 9. Intramolecular N-H O and C-H O interac-

3 3 3 3 3 3

tions in 7Z.

Figure 7. Thermal ellipsoid representation plot (50% probabi-

lity) of complex 10. Selected bond lengths (A) and angles (deg):

Pd(1)-C(1) 1.965(4), Pd(1)-C(31) 1.967(4), Pd(1)-N(3)

2.005(3), Pd(1)-O(1) 2.037(3), O(1)-C(19) 1.279(4), C(1)-

N(1) 1.295(5), C(31)-N(2) 1.154(5), C(1)-C(11) 1.471(5), C(11)-

C(12) 1.401(5), C(12)-N(3) 1.418(5), N(3)-C(17) 1.341(5),

C(17)-C(18) 1.417(5), C(18)-C(19) 1.394(5), C(18)-C(22)

1.508(5), C(22)-C(23) 1.516(5), C(22)-C(25) 1.319(6), C(25)-

C(26) 1.493(6), C(23)-O(2) 1.197(5), C(23)-O(3) 1.325(5), O(3)-

C(24) 1.444(5), C(26)-O(4) 1.195(5); C(1)-Pd(1)-C(31)

98.34(16), C(1)-Pd(1)-N(3) 82.63(14), C(31)-Pd(1)-O(1)

87.82(13), N(3)-Pd(1)-O(1) 91.63(12).

Figure 10. Chains along the c axis in 7E resulting from

C-H I interactions.

3 3 3

nation of the enamine NH group in complexes 1 and the

coordination to palladium of both nitrogen and oxygen

atoms to give the pincer derivatives 2-6 cause the deshield-

ing of the MeCN (Me⁸) and CH (C⁹) carbon nuclei (Me:

21.2 (1a), 21.0 (1b), 24.2-25.5 (2-6); CH: 96.5 (1a), 99.7

(1b), 102.2-103.9 (2-6); CN: 160.6 (1a), 160.0 (1b),

162.2-164.2 (2-6) ppm) and the shielding of the benzoyl

carbon (C¹²: 224.1 (1a), 222.3 (1b), 211.5-217.4 (2-6) ppm).

This can be attributable to an electronic flow from the

nitrogen to the oxygen caused by deprotonation and coordi-

nation of nitrogen and oxygen to palladium. However, other

effects regarding the displacement of the iodo and nitrogen

donor ligands cannot be ruled out. The ArC(O)Pd resonance

in complexes 1-6 is 30-40 ppm deshielded with respect to the

homologous ArC(NR)Pd one in related iminoacyl derivatives

because of the greater electronegativity of the oxygen atom.⁸

The NMR show also the ¹H, ¹³C, and ³¹P resonances expected

for the remaining ligands or cations except that of the μ-OH

proton, which is not observed in the ¹H NMR spectrum of 4,

probably because of its participation in hydrogen bonds. The

spectra of complexes 2 and 3 measured in d₆-dmso are

Figure 8. C-H Cl interactions in 5a resulting in chains

3 3 3

parallel to the a axis.

molecules with its homologues to give chains along the b axis,

which, along with other C-H O interactions, result in a

3 3 3

rather complex three-dimensional packing. In 7E C-H

interactions arrange the molecules into chains along the

3 3 3

c axis (Figure 10). In complex 10 the xylyliminium moiety

participates in N-H O and C-H F hydrogen bonds

with the oxygen and fluorine atoms of two different triflate

3 3 3

anions, giving rise to dimers (Figure 11).

NMR Spectra. The MeCN (Me⁸), MeC(O) (Me¹¹), and

CH (H⁹) (Scheme 1) resonances in the ¹H NMR spectra of

benzoyl complexes appear in the same ranges (1.91-2.36,

1.74-2.25, and 4.79-5.31 ppm, respectively) regardless of

the monocoordinated (1) or pincer (2-6) nature of the

benzoyl ligand. The ¹³C NMR spectra show that deproto-

Article

Organometallics, Vol. 29, No. 21, 2010 5707

proton resonance but a broad resonance at around 4.5 ppm,

too far from that expected for the NHXy proton (12.31 ppm

in 10 or 9-12.5 ppm in similar complexes^7,8). This complex

decomposes in solution and in the solid state. Thus, during

the acquisition time for the ¹³C NMR spectrum, it partly

decomposes back to 9 and its elemental analysis shows triflic

acid loss. These data suggest that this species is probably an

adduct formed through a TfOH N(Xy)dC (9 HOTf)

3 3 3

hydrogen bond between 9 and triflic acid. The picrate

complex 11 seems to be similar to 9 HOTf, although the

corresponding hydrogen bond seems to be stronger because

the complex is stable in solution and in the solid state. Thus,

the CdNXy carbon resonance of 11 (167.8 ppm) appears

almost at the same chemical shift as in its parent complex 9

(166.7 ppm). In addition, because of the picH N(Xy)dC

3 3 3

hydrogen bond, the OH proton resonance of Hpic (11.94

ppm in CHCl₃) is shown in 11 as a very wide resonance at

around 3 ppm (1 H).

IR Spectra. The expected ν_NHband is not observed in the

spectra of complexes 1a, 1b, 7Z, and 7E probably because of

the participation of the NH group in N-H O hydrogen

3 3 3

bonds, as shown in the crystal structures of 7Z and 7E. Bands

assigned to ν_CdO(acyl) in complexes 1-6 and to ν_asym(CO₂)

in complexes 7 and 8 are observed in the 1620-1670 and

1715-1730 cm^-1regions, respectively. A ν(OH) band at

2925 cm^-1in the IR spectrum of 11 compared to that at 3101

cm^-1in the spectrum of Hpic (both measured in hexachlor-

obutadiene mull on KBr plates) supports the existence in 11

Figure 11. N-H O and C-H F bonds in 10 resulting in

3 3 3 3 3 3

dimers.

identical to those of complex 6g, showing that both dinuclear

complexes dissolve in dmso upon bridge splitting and solvent

coordination.

While a unique set of resonances is present in the ¹H NMR

spectrum of 7Z, duplication is observed in that of 7E at room

temperature, indicating the presence of two isomers in solu-

tion, in 1.2:1 molar ratio. We think that in the E isomer the

close vicinity of Me⁸and Me¹¹to both CO₂Me groups pre-

vents the free rotation around the C⁹-C¹²bond (Scheme 2),

giving rise to two conformers. The activation energy for this

rotation is overcome at 90 °C, at which temperature the ¹H

NMR spectrum of 7E gives a single set of resonances. The

homologous resonances show only very small differences

within the two conformers in the ¹³C NMR spectrum of 7E at

room temperature, indicating their close similarity and

making it impossible to assign unequivocally some of them.

Most ¹H NMR and ¹³C NMR resonances are also similar to

those in the Z isomer; the main differences are those of the C⁹

and H¹⁵nuclei (Scheme 2) (C⁹: 104.5 (7Z), 101.3, 101.5 (7E);

H¹⁵: 6.15 (7Z), 7.06, 7.11 (7E) ppm).

of the picH N(Xy)dC hydrogen bond mentioned above.

3 3 3

The spectra show also the expected bands attributable to the

different ligands or counterions. A band at 1101 cm^-1in the

spectrum of 6g, assignable to the SdO stretching mode, is

indicative of S-coordination of the dmso ligand.⁴⁵

Conclusion

Carbon monoxide and dimethylacetylenedicarboxylate re-

act differently toward aryl palladium(II) complexes contain-

ing an ortho β-enaminone substituent. While the first inserts

into the Pd-C bond, affording benzoyl complexes, the second

inserts into the C-H bond of the ortho substituent. Two types

of complexes derived from the insertion of CO have been

prepared, those with the benzoyl ligand acting as monocoor-

dinate, which slowly lose CO, and stable C,N,O-pincer com-

plexes that result from deprotonation of the NH group in the

benzoyl ligand. Some of these complexes are of unusual types.

The insertion of the alkyne affords mainly the Z isomer, which

isomerizes upon heating to the E isomer and transforms by

reaction with Ag^þand an isocyanide into a pincer complex,

which, in turn, is photooxygenated by atmospheric oxygen to

afford a new pincer complex after AcOH loss.

The NMR spectra of complex 8 show also the presence of

two isomers in solution, in 1:10 molar ratio, which must be

the E and Z isomers because only one conformer is possible

for each isomer. The major and minor isomers show the H¹⁵

resonance (Scheme 2) at 7.07 and 6.14 ppm, respectively,

which suggests the major isomer of 8 to be 8E by comparison

with the homologous resonance in 7E (7.06, 7.11 ppm) and

7Z (6.15 ppm). In both isomers of 8 and in 9, the two halves

of the Xy^bgroup are inequivalent because of restricted

rotation around the N-Xy bond, while the Xy^agroup

rotates freely, as we have previously observed in similar com-

plexes.⁸The NMR spectra of complex 9 are in agreement

with the X-ray diffraction study.

ꢀ

Acknowledgment. We thank Ministerio de Educacion

y Ciencia (Spain), FEDER (CTQ2007-60808/BQU), and

ꢀ

Fundacion Seneca (04539/GERM/06 and 03059/PI/05)

for financial support and for grants to A.J.M.M. and A.

A.L., respectively.

When complex 8 is protonated with triflic acid, the result-

ing complex 10 shows a new NH proton resonance at 12.31

ppm and a highly deshielded CdNHXy carbon nucleus

(216.2 vs 178.2 ppm in 8; in complexes related to 10, it is

observed at 190-200 ppm^7,8). However, complex 9 reacts

with triflic acid to afford a complex of which the ¹H NMR

spectrum does not show the expected highly deshielded NH

Supporting Information Available: Listing of all refined and

calculated atomic coordinates, anisotropic thermal parameters,

bond lengths and angles, thermal ellipsoid representation plots,

and hydrogen bonds of complexes 6c and 6e and CIF files for

complexes 2, 3, 5a, 6b, 6c, 6e, 7Z, 7E, and 10. This material is

available free of charge via the Internet at http://pubs.acs.org.

Products guided by the article

Product name:[PdI(C(O)C₆H₄(NHC(Me)CHC(O)Me)-2)(N,N,N',N'-tetramethylethylenediamine)]

Cas No:1242099-50-8

R&D Labs maybe for 1242099-50-8

Nanjing Fubang Chemical Co.,Ltd

Contact:+86-25-83179199

Address:5F,Tianzheng international plaza,No399 Zhongyang Road ,Nanjing China
JIANGXI XINXIN CHEMICAL CO., LTD.

Contact:86-15957176628

Address:INDUSTRY ROAD 1, INDUSTRIAL PARK, HEKOU TOWN,YANSHAN COUNTY, JIANGXI PROVINCE, CHINA
Chen jie

Contact:027-87677569

Address:Room 2203, yujingmingmen Buidling One, xiongchu Road, wuhan city, hubei province, China
Yangling Ciyuan biotech Co., Ltd.

Contact:86-15802970736

Address:2-1804, International Park Mansion, No.2, South Fengdeng Road, Lianhu District
Pale Palm Imex

Contact:+36(21)2523420

Address:Head office: 1102 Budapest, SZENT LASZLO TER 24/B. 1/1., HUNGARY / CHINA

Relevant to this article

Organocatalyzed cyclopropanation of α-substituted α,β-unsaturated aldehydes: Enantioselective synthesis of cyclopropanes bearing a chiral quaternary center

Doi:10.1002/chem.201000334
(2010)
Scope and limitations of palladium-catalyzed cross-coupling reactions with organogold compounds

Doi:10.1002/adsc.201000159
(2010)
Assembly/disassembly of drug conjugates using imide ligation

Doi:10.1021/ol101049g
(2010)
A colorimetric and fluorescent chemosensor for copper ions in aqueous media and its application in living cells

Doi:10.1039/c0nj00168f
(2010)
2′-O-lysylaminohexyladenosine modified oligonucleotides

Doi:10.1007/s00706-010-0318-0
(2010)
Doi:10.1007/BF00903182
(1960)

Article Doi

Reactivity of ortho-β-enaminone-phenyl palladium complexes. Insertion of CO into the Pd-C bond to give the first acyl C,N,O-pincer complexes. sequential insertion of dimethylacetylenedicarboxylate into the enaminone C-H bond and of isocyanide into the Pd-

DOI: 10.1021/om1005403

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om1005403

Full text of DOI:10.1021/om1005403

Products guided by the article

R&D Labs maybe for 1242099-50-8

Relevant to this article

Hot Product