Samuel Castro-Juiz

Influence of phenyl ring substituents in the cyclometallation of Schiff base ligands: crystal and molecular structures of [Pd-{3,4-(OCH2O)C6H2C(H)N(Cy)-C2,N}(μ-O2CMe)]2 and [Pd-{3,4-(OCH2CH2O)C6H2C(H)N(Cy)-C6,N}(μ-O2CMe)]2

Abstract Reaction of Pd(OAc)2 with the Schiff base ligands 3,4-{O(CH2)nO}C6H3C(H)NR (n=1, 2; R=Cy, 3,4-(OCH2O)C6H3CH2-) leads to dinuclear cyclometallated products in which each palladium atom is C,N bonded to a deprotonated organic ligand, and to two acetate groups which bridge both metal centers. Treatment of 3,4-{O(CH2)2O}C6H3C(H)NCH2CH2NMe2 with [PtMe2(COD)] gives mononuclear compounds with the ligand as terdentate through the [C, N, N] atoms. The regioselectivity of the cyclometallation processes is discussed by 1H-NMR spectroscopy and X-ray diffraction studies.

Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: synthesis, characterization and reactivity. Crystal and molecular structures of [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)] and [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{μ-Ph2P(CH2)4PPh2}][CF3SO3]2

Treatment of the Schiff base 2-ClC6H4C(H)NCH2CH2SMe, 1, with palladium(II) acetate in dry toluene gave the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}(O2CMe)], 2. Reaction of 2 with aqueous sodium chloride gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)], 3, after a metathesis reaction. The X-ray crystal structure of 3 was determined and shows that the palladium atom is bonded to four different donor atoms: C, N, S and Cl. Treatment of 3 with triphenylphosphine in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)(PPh3)] with cleavage of the Pd–S bond. However, treatment of 3 with silver triflate and triphenylphosphine gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}(PPh3)][CF3SO3], 10, in which the Pd–S bond is retained. Reaction of 3 with the diphosphines dppm, dppb or dppf in a 2 : 1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC6H3C(H)NCH2CH2SMe](Cl)}2{μ-Ph2P(CH2)nPPh2}], (n=1, 5; n=4, 6), and [{Pd[2-ClC6H3C(H)NCH2CH2SMe](Cl)}2(μ-Ph2PC5H4FeC5H4PPh2)], 7. Treatment of 3 with dppb in a 2 : 1 molar ratio and AgCF3SO3 gave the dinuclear cyclometallated complex [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{μ-Ph2P(CH2)4PPh2}][CF3SO3]2, 11, which was characterized by X-ray crystal structure analysis. Reaction of 3 with dppe in a 1 : 1 molar ratio and sodium perchlorate gave the mononuclear complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}{Ph2P(CH2)2PPh2-P,P}][ClO4], 8. Treatment of 3 with bis(2-diphenylphosphinoethyl)phenylphosphine in a 1 : 1 molar ratio, followed by treatment with sodium perchlorate gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4], 9, in which the triphosphine is bonded to the palladium atom through the three phosphorus atoms.

Synthesis and reactivity of novel cyclometallated complexes derived from [C,N,O] terdentate ligands. Crystal structure of [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}(PPh3)]

Treatment of the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)N[2-(OH)C6H4], a, and 2,3,4-(MeO)3C6H2C(H)N[2-(OH)-4-MeC6H4], b, with palladium(II) acetate in toluene gave the cyclometallated complexes [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}]n, 1a, and [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]}]n, 1b, respectively, as air stable solids, with the [C,N,O] ligand terdentate after deprotonation of the –OH group. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}(PPh3)], 2a, and [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]}(PPh3)], 2b, with cleavage of the polynuclear structure. The molecular structure of 2a has been determined by X-ray crystallography. Treatment of 1a and 1b with the diphosphines dppm, dppp, dppb, dpppe and dppf in a 1∶2 molar ratio afforded the dinuclear cyclometallated complexes [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]})2{μ-PPh2(CH2)nPPh2}] (3a: n = 1; 4a: n = 3; 5a: n = 4; 6a: n = 5), [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]})2(μ-PPh2C5H4FeC5H4PPh2)], 7a, [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]})2{μ-PPh2(CH2)nPPh2}] (3b: n = 3; 4b: n = 4) and [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]})2(μ-PPh2C5H4FeC5H4PPh2)], 5b, as air stable solids. Treatment of 1a and 1b with an excess of mono- or diphosphine did not produce cleavage of the Pd–Ochelating bond.

The First Crystal and Molecular Structure of asyn-Acetato-Bridged Dinuclear Cyclometallated Complex [Pd{2,3,4-(MeO)3C6HC(H)=NCH2CH2OH}(μ-OAc)]2

Treatment of the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)=NR (R = CH2CH2OH, 1; R = Me, 17; R = Et, 18; R = Pr, 19; R = tBu, 20) with palladium(II) acetate in toluene gave the dinuclear cyclometallated complexes [Pd{2,3,4-(MeO)3C6HC(H)=NR}(μ-O2CMe)]2 (R = CH2CH2OH, 2; R = Me, 21; R = Et, 22; R = Pr, 23; R = tBu, 24), with the ligand bonded to the palladium atom through the imine nitrogen and the C6 carbon atoms. The 1H and 13C{1H} NMR spectra of the complexes showed the presence of the anti and syn isomers in solution. The anti/syn ratio varies with the solvent and the nature of the imine nitrogen substituent R. Complex 24 with the bulky tBu group showed a 28:1 ratio in chloroform whilst the less bulky substituted complexes showed lower ratios. The X-ray crystal structure of the syn isomer of complex 2 is described. Reaction of the acetato-bridged complex 2 with PPh3 gave the mononuclear complex 4, in a bridge-splitting reaction. Reaction of 2 with the diphosphanes dppm, dppp and dppb in a 1:1 molar ratio gave the dinuclear cyclometallated complexes 5, 6 and 7, respectively. Treatment of 2 with an aqueous solution of sodium chloride gave the chloro-bridged complex 3. Treatment of the cyclometallated chloro-bridged complex 3 with PPh3 in acetone yielded the mononuclear complex 8, and reaction of 3 with silver triflate gave the cyclometallated complex 9, with the palladium atom bonded to four different atoms C, N, O and P. Treatment of 3 with the tertiary diphosphanes dppp, dppb and dppf, in a 1:1 molar ratio gave the dinuclear complexes 10, 11 and 12, respectively, with terminal chloride ligands. However, reaction of 3 with the small “bite” diphosphane dppm gave 13, with a bridging chloride ligand. Reaction of 11 with silver triflate in acetone gave the new dinuclear complex 14, with the Schiff base ligand as [C,N,O] terdentate. Reaction of 3 with the diphosphane dppe in a 1:2 molar ratio, and silver perchlorate, gave the mononuclear complex 15. Treatment of 3 with the triphosphane bis(2-diphenylphosphanylethyl)phenylphosphane in a 1:2 molar ratio, followed by treatment with sodium perchlorate, gave 16, in which the palladium atom was bonded to the triphosphane through the three phosphorus atoms. The X-ray crystal structures of complexes 8, 9, 15 and 16 are also reported. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Polynuclear cyclometallated palladium(II) complexes. Crystal and molecular structures of [(PPh3)(Cl)PdN(Cy)C(H)C6H2C(H)N(Cy) Pd(Cl)(PPh3)] and [{PdN(Cy)C(H)C6H2C(H)N(Cy)Pd}{Ph2PC(H)C(H)PPh2-P,P}2][ClO4]2

Abstract Treatment of N , N -terephthalylidenebis(cyclohexylamine) ( L ) with palladium(II) acetate in toluene at room temperature gave the dicyclometallated acetato-bridged complex [(OAc)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(OAc)] n ( 1 ). Reaction of 1 with lithium chloride or bromide in acetone produced the chloro- or bromo-bridged complexes [(Cl)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(Cl)] n ( 2 ) and [(Br)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(Br)] n ( 3 ), respectively. Reaction of 2 with triphenylphosphine gave [(PPh 3 )(Cl)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(Cl)(PPh 3 )] ( 4 ). Treatment of 2 and 3 with bis(diphenylphosphino)methane and 1,5-bis(diphenylphosphino)pentane in a 1:1 molar ratio afforded [{(Cl)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(Cl)} 2 {μ-Ph 2 PCH 2 PPh 2 } 2 ] ( 5 ) and [{(Br)PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd(Br)} 2 {μ-Ph 2 P(CH 2 ) 5 PPh 2 } 2 ] ( 6 ), respectively. Reaction of 2 and 3 with bis(diphenylphosphino)methane or cis -1,5-bis(diphenylphosphino)ethene, in a 1:2 molar ratio, and sodium perchlorate, gave dinuclear cyclometallated compounds with two chelated phosphine ligands [{PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd}{Ph 2 PCH 2 PPh 2 - P , P } 2 ][ClO 4 ] 2 ( 7 ) and [{PdN(Cy)C(H)C 6 H 2 C(H)N(Cy)Pd}{Ph 2 PC(H)C(H)PPh 2 - P , P } 2 ][ClO 4 ] 2 ( 8 ). The compounds have been fully characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and complexes 4 and 8 by X-ray crystallography.

Directed regioselectivity in cyclometallated palladium(II) compounds of N-benzylidenebenzylamines. Crystal and molecular structure of [Pd{3,4-(OCH2O)C6H2C(H)NCH2[3,4-(OCH2O)C6H3]-C2,N}(μ-O2CMe)]2

Abstract The reaction of the Schiff base ligand 3,4-(OCH2O)C6H3C(H)NCH2[3,4-(OCH2O)C6H3] (a) with Pd(OAc)2 yields two endocyclic cyclometallated compounds: [Pd{3,4-(OCH2O)C6H2C(H)NCH2[3,4-(OCH2O)C6H3]-C2,N}(μ-O2CMe)]2 (C2,N-bonded) (1a), and [Pd{3,4-(OCH2O)C6H2C(H)NCH2[3,4-(OCH2O)C6H3]-C6,N}(μ-O2CMe)]2 (C6,N-bonded) (1b), which may be separated by fractional crystallization. The corresponding cyclopalladated dimers with bridging chloride ligands, 2a, 2b, have been prepared by a metathesis reaction with aqueous sodium chloride. Treatment of the latter compounds with tertiary phosphines in the appropriate molar ratio gave the mono and dinuclear compounds, 3a–8a and 3b–5b, respectively. The structure of compound 1a has been determined by X-ray diffraction analysis. The molecular configuration is a dimeric form of the anti isomer with the cyclopalladated moieties in an ‘open-book’ arrangement linked by two acetate bridging ligands.

Cyclopalladated compounds with bridging and chelating diphosphine ligands. Effect of ring size. Crystal and molecular structure of [{Pd[4-(COH)C6H3C(H)N(Cy)-C2,N](Cl)}2(μ-Ph2PCH2PPh2)]

Abstract Treatment of the chloro-bridged dinuclear compound [{Pd[4-(COH)C6H3C(H)N(Cy)-C2,N]}(μ-Cl)]2 (1) with tertiary diphosphines in 1:1 molar ratio gave [{Pd[4-(COH)C6H3C(H)N(Cy)-C2,N](Cl)}2(μ-Ph2PRPPh2)] (R: CH2, 2; CH2CH2, 3; (CH2)4, 4; (CH2)6, 5; Fe(C5H4)2, 6; trans-CHCH, 7; CC, 8) with the diphosphine in a bridging mode. When the reaction was carried out in a 1:2 molar ratio in the presence of NH4PF6, the compounds [Pd{4-(COH)C6H3C(H)NCy-C2,N}(Ph2PRPPh2-P,P)][PF6] (R: CH2, 9; CH2CH2, 10; (CH2)4, 11; (CH2)6, 12; Fe(C5H4)2, 13; 1,2-C6H4, 14; cis-CHCH, 15; NH, 16) with the diphosphine chelated to the palladium atom, were obtained. 1H, 31P–{1H} and 13C–{1H} NMR, IR and mass spectroscopic data are given. The crystal structure of compound 2 has been determined by X-ray crystallography.