Mono- and dinuclear palladium(II) compounds containing N,S donor ligands (original) (raw)
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Polyhedron, 2002
Treatment of the Schiff base ligands 2-ClC 6 H 4 C(H) NCH 2 (C 4 H 7 O) (a) and 3,4-(MeO) 2 C 6 H 3 C(H) NCH 2 (C 4 H 7 O) (b) with palladium(II) acetate in toluene or glacial acetic acid gave the dinuclear cyclometallated complexes [Pd{2-ClC 6 H 3 C-(H) NCH 2 (C 4 H 7 O)}(m-OAc)] 2 (1a) and [Pd{3,4-(MeO) 2 C 6 H 2 C(H) NCH 2 (C 4 H 7 O)}(m-OAc)] 2 (1b) with the ligand bonded to the palladium atom through the imine nitrogen and the C6 carbon atom. The 1 H and 13 C-{ 1 H} NMR spectra of the complexes show the occurrence in solution of three pairs of enantiomers. The acetato-bridged cyclometallated complex [Pd{3,4-(MeO) 2 C 6 H 2 C(H) NCH 2 (C 4 H 7 O)}(m-OAc)] 2 (1c) was prepared from the enantiopure ligand (R)-3,4-(MeO) 2 C 6 H 3 (H) NCH 2 (C 4 H 7 O) (c). The NMR spectra of 1c showed the existence of only two diastereomers in the solution. The reaction of 1a and 1b with aqueous sodium chloride gave the chloro-bridged complexes [Pd{2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}(m-Cl)] 2 (2a) and [Pd{3,4-(MeO) 2 C 6 H 2 C(H) NCH 2 (C 4 H 7 O)}(m-Cl)] 2 (2b) after a metathesis reaction. The reaction of 2a with PPh 3 in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}(Cl)(PPh 3)] (3a) in a bridge-splitting reaction. Treatment of 3a with silver triflate gave the cyclometallated complex [Pd{2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}(PPh 3)][CF 3 SO 3 ] (4a) in which the palladium atom is bonded to four different atoms C, N, O and P. When complex 2a was reacted with silver triflate in acetone complex [Pd{2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}((CH 3) 2 CO)][CF 3 SO 3 ] (5a) was obtained with the ligand as [C,N,O] coordinated. The reaction of complexes 2a and 2b with the diphosphine dppp in a complex-phosphine 1:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)](Cl)} 2 (m-Ph 2 P(CH 2) 3 PPh 2)] (8a) and [{Pd[3,4-(MeO) 2 C 6 H 2 C-(H) NCH 2 (C 4 H 7 O)](Cl)} 2 (m-Ph 2 P(CH 2) 3 PPh 2)] (5b) with the diphosphine bridging the two palladium atoms. Reaction of complexes 2a and 2b with the phosphines dppp and cis-dppe in a 1:2 molar ratio gave the mononuclear complexes [Pd{2-ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}{Ph 2 P(CH 2) 3 Ph 2-P,P}][ClO 4 ] (6a), [Pd{3,4-(MeO) 2 C 6 H 2 C(H) NCH 2 (C 4 H 7 O)}{Ph 2 P(CH 2) 3 Ph 2-P,P}][ClO 4 ] (3b) and [Pd{2-ClC 6 H 2 C(H) NCH 2 (C 4 H 7 O)}(cis-Ph 2 PCH CHPh 2-P,P)][Cl] (4b). The treatment of 2a with the triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio, followed by treatment with sodium perchlorate gave [Pd{3,4-(MeO) 2 ClC 6 H 3 C(H) NCH 2 (C 4 H 7 O)}{(PPh 2 CH 2 CH 2) 2 PPh-P,P,P}][ClO 4 ] (7a) in which the palladium atom is bonded to the triphosphine through the three phosphorus atoms and to the Schiff base ligand through one carbon atom and the imine nitrogen.
Organometallics, 2008
Synthesis and Coordination Properties of Chelating Dithiophenolate Ligands
Inorganic Chemistry, 2009
Chelating 3,3′-R 1 -5,5′-R 2 -2,2′-dithiobiphenyl ligands (R 1 ) R 2 ) Cl, 4a; R 1 ) R 2 ) t Bu, 4b; R 1 ) allyl, R 2 ) H, 4c) and the 2,2′-methylenedibenzenethiol ligand (4d) were synthesized from the corresponding diols (1a-1d) via a three-step procedure involving a Miyazaki-Newman-Kwart rearrangement. Zinc complexes and a tin complex (for 4c) have been prepared to explore their coordination potential, and the substitution pattern, as well as the chelate ring size, is shown to severely effect their ligating properties. Four of the complexes have been characterized crystallographically in the solid state, and the nuclearity of the zinc complexes in solution has been studied by diffusion-ordered NMR spectroscopy. Depending on the ligand, zinc complexes [(4)Zn(4,4′-t Bu-bipyridine)] n (5a-d) are monomeric (n ) 1; 4b, 4c), monomeric in solution and dimeric in the solid state (n ) 1, 2; 4a), or dimeric overall (n ) 2; 4d). The tin complex (4c)SnPh 2 (6c) was additionally synthesized to prove the coordinating abilities of the allyl substituted ligand 4c.
Journal of Thermal Analysis and Calorimetry, 2002
The dimeric compound [Pd(bzan)(μ-OOCCH3)]2 (1) (bzan=N-benzylideneaniline) reacts with KX, in methanol/acetone (2:1), affording the analogous dimeric pseudohalogen-bridged species [Pd(bzan)(μ-X)]2 [X=NCO(2),SCN(3), CN(4)]. The compounds were characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. IR data for 2–4 showed bands typical of coordinated pseudohalogen ligands clearly indicating the occurrence of the exchange reaction. Their thermal behaviour was investigated and suggested that their stability is influenced by the bridging ligand. The thermal stability decreased in the order[Pd(bzan)(μ-CN)]2>[Pd(bzan)(μ-SCN)]2>[Pd(bzan)(μ-OOCCH3)]2>[Pd(bzan)(μ-NCO)]2. X-ray results showed the formation of Pd° as final decomposition product.
Organometallic Complexes of Palladium(II) Derived from 2,6-Diacetylpyridine Dimethylketal
Organometallics, 2010
PdCl 2 reacts with 2,6-diacetylpyridine (dap) (1:1) in refluxing MeOH to give the pincer complex [Pd(O 1 ,N 1 ,C 1 -L)Cl] (1) and (QH) 2 [{PdCl 2 ( μ-Cl)}] 2 (2), where L is the monoanionic ligand resulting from deprotonation of the acetyl methyl group of the monoketal of dap and QH is C 5 H 3 NH{C-(OMe) 2 Me} 2 -2,6, the diketal of Hdap þ . Reaction of 2 with NEt 3 (1:2) in MeOH affords Q = C 5 H 3 N{C(OMe) 2 Me} 2 -2,6 (3). Complex 1 reacts with 2 equiv of RNC at 0°C to give trans-[Pd(C 1 -L)Cl(CNR) 2 ] (R = Xy = 2,6-dimethylphenyl (4a), t Bu (4b)) but at room temperature affords [Pd(O 2 , C 2 -L R )Cl(CNR)] (R = Xy (5a), t Bu (5b)). The ligand L R results from the insertion of one isocyanide into the Pd-C bond plus a tautomerization process from β-ketoimine to β-ketoenamine and coordinates in 5 through the carbonyl oxygen atom (O 2 ) and the inserted isocyanide carbon atom (C 2 ). The reaction of 1 with 1 equiv of RNC at 0°C leads to a mixture of [Pd(N 1 ,C 1 -L)Cl(CNR)] (R = Xy (6a), t Bu (6b); 85-90%), 1, and 4, but at room temperature gives the pincer complex [Pd(O 1 ,N 1 ,C 2 -L R )Cl] (R = Xy (7a), t Bu (7b)), resulting from insertion/tautomerization processes similar to that leading to 5. Complex 7 reacts at 0°C (1) with 2 equiv of RNC to give trans-[Pd(C 2 -L R )Cl(CNXy) 2 ] (R = Xy (8a), t Bu (8b)) or (2) with 1 equiv of t BuNC to afford 5b. The reaction of 1 (1) with [Tl(acac)] gives [Pd(N 1 ,C 1 -L)(acac)] (9); (2) with chelating ligands N ∧ N affords [Pd(C 1 -L)Cl(N ∧ N)] (N ∧ N = 2,2 0bipyridine = bpy (10), 4,4 0 -di-tert-butyl-2,2 0 -bipyridine = dbbpy (11)); (3) with 1 equiv of PPh 3 gives, in the same way as with isocyanides, an equilibrium mixture of [Pd(N 1 ,C 1 -L)Cl(PPh 3 )] (12), 1, and trans-[Pd(C 1 -L)Cl(PPh 3 ) 2 ] (13), which is the only product when 2 equiv of PPh 3 is added to the reaction mixture; and with excess PPh 3 affords the monoketal of dap, C 5 H 3 N{C(O)Me-2}{C(OMe) 2 Me-6} (14), and [Pd(PPh 3 ) 4 ]. The crystal structures of complexes 1, 2, 5b, 6a, and 7a have been determined. *Corresponding authors. E-mail: jvs1@um.es (J.V.); aurelia@um.es (A.A.). Web: http://www.um.es/gqo/.
Molecules
Three new palladium complexes ([Pd(DABA)Cl2], [Pd(CPDA)Cl2], and [Pd(HZPY)Cl2]) bearing dinitrogen ligands (DABA: 3,4-diaminobenzoic acid; CPDA: 4-chloro–o-phenylenediamine; HZPY: 2-hydraziniopyridine) were synthesized, characterized, and tested against breast cancer (MCF-7), prostate carcinoma cell line (PC3) and liver carcinoma cell line (HEPG2). [Pd(DABA)Cl2] complex exhibited the highest inhibition percentage, lying between 68–71%. The hydrolysis mechanism of each palladium complex, the key step preceding the binding to the biological target, as well as their photophysical properties were explored by means of DFT and TDDFT computations. Results indicate a faster hydrolysis process for the Pd(DABA)Cl2 complex. The computed activation energies for the first and second hydrolysis processes suggest that all the compounds could reach DNA in their monohydrated form.
Dalton Transactions, 2011
A new acetate-bridged dinuclear palladacycle with unsubstituted N-phenylpyrazole [{Pd(phpz)(m-AcO)} 2 ] 1 has been isolated and characterised, including an X-ray diffraction study. A survey of the Cambridge Structural Database (CSD) v. 5.31 looking for analogous dimeric CˆN cyclopalladated complexes has been done, exploring the incidence of cisoid/transoid arrangements, the preferred conformation of the eight-membered ring formed in the double bridge, the Pd-Pd distance and the main factors that affect it. The reaction of 1 with NBu 4 OH yielded [{Pd(phpz)(m-OH)} 2 ] 2 that has shown to be a complementary precursor of 1 in terms of acid/base reactivity. In this sense, both 1 and 2 are also well differentiated from halide precursors available to date. The preparation of selected complexes with potential applications in several fields,