Ma Teresa Pereira

Synthesis of cyclometallated complexes of PdII. The X-ray crystal structure of di-μ-bromo-bis[N-(3,4-dimethoxybenzylidene)cyclohexylaminato-C6,N]dipalladium(II)

Abstract The structure of the cyclometallated bromo-brided palladium(II) dimer complex [P d{3,4-(MeO) 2 C 6 H 2 C(H)&.dbnd;N Cy}(Br)] 2 is described. This is the first example of a structurally characterised cyclometallated bromo-bridged dimer. Crystals were triclinic, space group P 1 with a = 788.7(2), b = 911.0(3), c = 1480.(4) pm, α = 96.94(2), β = 91.57(2), γ = 101.85(2)°, Z = 1, U = 1.0322(5) nm 3 , R = 0.0688, R w = 0.790, for 3280 independent reflections with F >4.0σ( F ). The structure is a centrosymmetric palladium dimer with two asymmetrically bridging bromine atoms and non-bonding Pd⋯Pd distance of 363.1(5) pm. The synthesis of the iodo-bridged analogue and the reactions of these two dimers and the chloro-bridged analogue with various tertiary phosphines are also described.

Cyclometallated complexes of PdII and MnI with N,N-terephthalylidenebis(cyclohexylamine)

Treatment of N,N-terephthalylidenebis(cyclohexylamine), 1,4-(CyNCH)2C6H4 (Cy = cyclohexyl) with palladium(II) acetate in glacial acetic acid gave the monocyclometallated dimer complex [{Pd[4-(CHO)C6H3CHNCy](O2CMe)}2] (1) which was shown to have a free formyl group on each phenyl ring by IR and 1H and 13C-{1H} NMR spectroscopy. Treatment of 1,4-(CyNCH)2C6H4 with [MnMe(CO)5] in octane gave the doubly cyclometallated complex [(OC)4MnN(Cy)C(H)CC6H2C(H)N(Cy)Mn(CO)4] (2). Reaction of 1 with aqueous sodium chloride, bromide or iodide gave the monocyclometallated dimer complexes [{Pd[4-(CHO)C6H3C(H)NCy](X)}2] [X = Cl (3), Br (4), or I (5)]. Complexes 1, 3 and 4 react with amines to give the corresponding cyclometallated dimer complexes [Pd{4-(CyNCH)C6H3C(H)NCy}(O2CMe)]2 (6) and [{Pd[4-(CyN=CH)C6H3C(H)=NR](X)}2] [X = Cl (7), X = Br (8) R = Cy; X = Cl, R = 2,4,6-Me3C6H2 (9)] with an uncoordinated C=N group on each phenyl ring. Treatment of 3, 4 or 5 with thallium acetylacetonate gave the cyclometallated monomer compound [Pd{4-(CHO)C6H3C(H)=NCy}-(CH3COCHCOCH3)] (10) with a chelating 2,4-pentanedionate group. Treatment of 3, 4 or 5 with tertiary phosphines in a dimer/ phosphine 1:2 or 1:4 molar ratio afforded the cyclometallated [Pd{4-(CHO)C6H3C(H)=NCy}(X)(L)] (11–18) and noncyclometallated [Pd{4-(CHO)C6H3C(H)=NCy}(X)(L)2] (25–31) (X=Cl, Br, or I; L=PPh3, PPh2Et, PPhEt2, or PPh2Me). Reaction of 11–13 with cyclohexylamine (L=PPh3) gave the non-cyclometallated compounds [Pd{4-(CyN=CH)C6H3C-(H)=NCy}(X)(PPh3)(NH2Cy)] (19–21) with two uncoordinated C=N groups whereas reaction of 14–18 with cyclohexylamine (L = PPh2Et, PphEt2, or PPh2Me) gave the cyclometallated compounds [Pd{4-(CyN=CH)C6H3C(H)=NCy}(X)(L)] (22–24). Compounds 25 and 29 gave [Pd{4-(CyN=CH)C6H3C)(H)=NCy}(Cl)(L)2] (32,33) (L= PPh3, or PPh2Et) when treated with cyclohexylamine. IR and 1H, 13C and 31P NMR data are discussed.

Cyclometallated complexes of palladium(II) with a C, N, N′ terdentate Schiff base donor ligand. Oxidative addition of an arylchlorine bond to palladium(O)

Treatment of N-(2-chlorobenzylidene)-N,N′-dimethylethylenediamine, 2-ClC6H4C(H)NCH2CH2NMe2, with tris(dibenzylideneacetone)dipalladium(0) in chloroform gave the oxidative addition cyclometallated product [Pd{C6H4C(H)NCH2CH2NMe2}(Cl)] (1) with the palladium atom bonded to a C,N,N′ terdentate donor ligand. Treatment of 1 with tertiary monophosphines gave the cyclometallated complexes [Pd{C6H4C(H)NCH2CH2NMe2}(Cl)(L)](2: L  PPh3; 3: L  PEtPh2; 4: L  PEt2Ph; 5: L  PEt3), where the phosphine ligand is either trans to the phenyl carbon atom (2, 3) or trans to the imine nitrogen atom (4, 5). Treatment of 1 with silver perchlorate followed by reaction with tertiary monophosphines gave the cyclometallated complexes [Pd{C6H4C(H)NCH2CH2NMe2}(L)][ClO4] (6: L  PPh3; 7: L  PEtPh2; 8: L  PEt2Ph; 9: L  PEt3). Reaction of 1 with thallium acetylacetonate gave the cyclometallated complex [Pd{C6H4C(H)NCH2CH2NMe2}(H3CCOCHCOCH3)] (10). Treatment of 1 with ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C6H4C(H)NCH2CH2NMe2](Cl)}2(LL)(11: LL = trans-Ph2PCHCHPPh2; 12: LL  Ph2P(CH2)3PPh2;13: LL  Ph2P(CH2)4PPh2), where the phosphorus atom is trans to the phenyl carbon atom. Treatment of 1 with silver perchlorate followed by ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C6H4C(H)NCH2CH2NMe2]}2 (LL)][ClO4]2 [14: LL=trans-Ph2PCHCHPPh2; 15: LL  Ph2P(CH2)3PPh2; 16: LL  Ph2P(CH2)4PPh2)]. Reaction of 1 with ditertiary diphosphines in a complex 1/diphosphine 1:1 molar ratio, and silver perchlorate as appropriate, gave the cyclometallated complexes [Pd{C6H4C(H)NCH2CH2NMe2}(Ph2P(CH2)2PPh2-P,P)][ClO4] (17), [Pd{C6H4C(H)NCH2CH2NMe2}(Ph2P(CH2)3PPh2-P,P)][ClO4] (18), [Pd{C6H4C(H)NCH2CH2NMe2}(cis-Ph2PCHCHPPh2-P,P)][Cl] (19) and [Pd{C6H4C-(H)NCH2CH2NMe2}(Cl)(Ph2P(CH2)4PPh2-P,P)] (20).

Cyclometallated complexes of bis(N-benzylidene)-1,4-phenylenediamines. Synthesis and crystal structure of [1,4-{Pd[2,3,4-(MeO)3C6HC(H)=N](Br)}2C6H4]2: a novel tetranuclear cyclometallated palladium(II) complex

Abstract Treatment of 1,4-{2,3,4-(MeO)3C6H2C(H)=N-}2C6H, (a) or 1,4-{4,5-(OCH2O)C6H 3C(H)=N-}2-C6H4 (b) with palladium(II) acetate gave the cyclometallated acetato-bridged complexes [1,4-{ Pd [2,3,4-(MeO) 3 C 6 HC(H)=N ](O2CMe)}2C6H4]n (1a) and [1,4- Pd[4,5-(OCH 2 O)C 6 H 2 C(H)=N ](O2CMe)}2-C6H4]n (1b). These were converted into the analogous halide-bridged complexes by treatment with NaX (2a, 2b X = Cl; 3a, 3b X = Br). Reaction of a or b with PdCl2 also affords the chloro-bridged complexes 2a and 2b, which reacted with LiBr to give the bromo-bridged complexes 3a and 3b. The structure of 3a is described. This is the first example of a structurally characterized tetranuclear cyclometallated bromo-bridged palladium(II) complex. Crystals are triclinic, space group P 1 , with a 1109.1(4), b 1181.5(4), c 1481.5(5) pm, α 77.33(3), β 80.04(3), γ 82.50(3), U 1.857(1) nm3, Z = 1, R = 0.0558 and RW = 0.0610, for 3871 independent reflections with I > 2.0σ-(I). The structure is a centrosymmetric tetranuclear palladium(II) dimer with symmetrically bridging bromine atoms and non-bonding Pd ⋯ Pd distance of 366.2(5) pm.

Cyclometallation&—III. Regioselectivity in Pd(II) Cyclometallated complexes

Abstract Cyclometallated complexes derived from organic ligands where two initial metallation sites are present have been synthesized. The preferred palladation position is discussed on the basis of electronic and steric effects, and the regioselectivity of the cyclometallation is characterized by means of IR and 1 H NMR spectroscopy. The spectral studies show that the less favored position is not attached to the metal atom. Acetato- and halogeno-bridged dimers, as well as phosphine monomers derived from the latter, have been obtained and studied by spectroscopical methods.

Novel structures of cyclometallated complexes of palladium(II) derived from terdentate ligands. Crystal and molecular structure of [Pd{C6H4C(H)NCH2CH2CH2NMe2}(X)] (X=Cl, Br, I)

Abstract Treatment of N-(2-chlorobenzylidene)-N,N-dimethyl-1,3-propanediamine (1) and N-(2-bromo-3,4-(MeO)2-benzylidene)-N,N-dimethyl-1,3-propanediamine (20) with tris(dibenzylideneacetone)dipalladium(0) in toluene gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)NCH2CH2CH2NMe2}(Cl)] (2) and [Pd{3,4-(MeO)2C6H2C(H)NCH2CH2CH2NMe2}(Br)] (21), respectively, via oxidative addition reaction with the ligand as a C,N,N terdentate ligand. Reaction of 2 with sodium bromide or iodide in an acetone–water mixture gave the cyclometallated analogues of 2, [Pd{C6H4C(H)NCH2CH2CH2NMe2}(Br)] (3) and [Pd{C6H4C(H)NCH2CH2CH2NMe2}(I)] (4), by halogen exchange. The X-ray crystal structures of 2, 3 and 4 were determined and discussed. Treatment of 2, 3, 4 and 21 with tertiary monophosphines in acetone gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)NCH2CH2CH2NMe2}(L)(X)] (6: L=PPh3, X=Cl; 7: L=PPh3, X=Br; 8: L=PPh3, X=I; 9: L=PMePh2, X=Cl; 10: L=PMe2Ph, X=Cl) and [Pd{3,4-(MeO)2C6H2C(H)NCH2CH2CH2NMe2}(L)(Br)] (22: L=PPh3; 23: L=PMePh2; 24: L=PMe2Ph). A fluxional behaviour due to an uncoordinated CH2CH2CH2NMe2 could be determined by variable temperature NMR spectroscopy. Treatment of 2, 3 and 4 with silver trifluoromethanesulfonate followed by reaction with triphenylphosphine gave the mononuclear complex [Pd{C6H4C(H)NCH2CH2CH2NMe2}(PPh3)][F3CSO3] (11) where the Pd–NMe2 bond was retained. Reaction of 2, 3 and 4 with ditertiary diphosphines in a cyclometallated complex–diphosphine 2:1 molar ratio gave the binuclear complexes [{Pd[C6H4C(H)NCH2CH2CH2NMe2](X)}2(μ-L–L)][L–L=PPh2(CH2)4PPh2(dppb) (13, X=Cl; 14, X=Br; 15, X=I; L–L=PPh2(CH2)5PPh2(dpppe): 16, X=Cl; 17, X=Br; 18, X=I) with palladium–NMe2 bond cleavage. Treatment of 2, 3 and 4 with ditertiary diphosphines, in a cyclometallated complex–diphosphine 2:1, molar ratio and AgSO3CF3 gave the binuclear cyclometallated complexes [{Pd[C6H4C(H)NCH2CH2CH2NMe2]}2(μ-L–L)][F3CSO3]2 (11: L–L=PPh2(CH2)4PPh2(dppb), X=Cl; 12: L–L=PPh2(CH2)5PPh2 (dpppe), X=Cl). Reaction of 2 with the ditertiary diphosphine cis-dppe in a cyclometallated complex–diphosphine 1:1 molar ratio followed by treatment with sodium perchlorate gave the mononuclear cyclometallated complex [Pd{C6H4C(H)NCH2CH2CH2NMe2}(cis-PPh2CHCHPPh2–P,P)][ClO4] (19).

Cyclometallated complexes of palladium(II) with 1-methyl-2-phenylimidazole and tertiary diphosphines. Crystal and molecular structure of [Pd[o-C6H4C=NC(H)=C(H)NMe](Ph2PCH(Me)PPh2-P,P)][PF6]

Abstract Treatment of Pd(AcO) 2 with 1-methyl-2-phenylimidazole, and subsequent treatment with sodium chloride or sodium bromide gave the corresponding halide-bridged cyclometallated complexes [Pd o -C 6 H 4 C=NC(H)=C(H)NMe( μ -X)] 2 ( 2 , X = Cl; 3 , X = Br). Complexes 2 and 3 react with tertiary diphosphines in a 1:1 molar ratio to give dinuclear cyclometallated compounds with bridging diphosphine and halogen ligands [Pd o -C 6 H 4 C=NC(H)=C(H)NMe( μ -L-L)( μ -X)]X ( 4–9 ) or with only bridging diphosphine ligands [Pd o -C 6 H 4 C=NC(H)=C(H)NMe( μ -L-L)(X) 2 ] ( 10–17 ), [X = Cl, Br; L-L = Ph 2 PCH 2 PPh 2 (dppm), Ph 2 PC(=CH 2 )PPh 2 (vdpp), Ph 2 PCH(CH 3 )PPh 2 (1,1-dppe), trans -Ph 2 P(CH=CH)PPh 2 ( trans -dppe), Ph 2 P(CH 2 ) 2 PPh 2 (dppe), Ph 2 P(CH 2 ) 3 PPh 2 (dppp), Ph 2 P(CH 2 ) 4 PPh 2 (dppb), as appropriate]. When the reaction is carried out in a 1:2 molar ratio and in the presence of NH 4 PF 6 or NaClO 4 , mononuclear cyclometallated compounds with a chelating diphosphine ligand are obtained [Pd o -C 6 H 4 C=NC(H)=C(H)NMe(L-L-P,P)][Y] ( 18–27 ) [Y = PF 6 , ClO 4 ; L-L = Ph 2 PCH 2 PPh 2 (dppm), Ph 2 PC(=CH 2 )PPh 2 (vdpp), Ph 2 PCH(CH 3 )PPh 2 (1,1-dppe), Ph 2 PN(CH 3 )PPh 2 (dppma), cis -Ph 2 P(CH=CH)PPh 2 ( cis -dppe), Ph 2 P(CH 2 ) 2 PPh 2 (dppe), Ph 2 P(CH 2 )PPh 2 (dppp), Ph 2 P(CH 2 ) 4 PPh 2 (dppb)]. Compounds 18–22 and 25–27 could also be obtained by reaction of complexes 4–17 with the appropriate diphosphine and NH 4 PF 6 or NaClO 4 . The diphosphines dppma and cis -dppe failed to behave as bridging ligands and only gave mononuclear compounds. The complexes were characterized by their elemental analysis (C, H, N) and by IR and 31 P- 1 H and 1 H NMR data. The X-ray crystal structure of complex 22 is described.

Synthesis and characterization of cyclometallated palladium(ii) complexes with Ph2PCH2PPh2 (dppm), trans-Ph2PCHCHPPh2 (trans-dppe), cis-Ph2PCHCHPPh2 (cis-dppe) and Ph2P(CH2)4PPh2 (dppb). The x-ray crystal structure of di-μ-bromo-bis[n-(4-methylbenzylidene)cyclohexylaminato-C6,N]dipalladium(II)

Abstract Treatment of the Schiff bases 4-MeC 6 H 4 C(H)NCy (a), 3-Me-4-MeOC 6 H 3 C(H)N-2′,4′-6′-Me 3 C 6 H 2 ( b ) or 2,4-Me 2 C 6 H 3 C(H)N-2′,4′,6′-Me 3 C 6 H 2 (c) with palladium(II) acetate gave the cyclometallated complexes 1a , 1b and 1c . These reacted with NaX to give the halide-bridged complexes 2a , 2b and 2c (X = Cl), 3a , 3b and 3c (X = Br) and 4c (X = I). Reaction of the halide-bridged dimers with Ph 2 PCH 2 PPh 2 (dppm), trans - Ph 2 PCHCHPPh 2 ( trans -dppe), cis -Ph 2 PCHCHPPh 2 ( cis -dppe) or Ph 2 P(CH 2 ) 4 PPh 2 (dppb), as appropriate in a dimer/diphosphine 1:1 or 1:2 molar ratio gave the dinuclear phosphine-bridged 4a , 5a , 4b , 5b , 5c – 7c and 8c – 10c and mononuclear 6a , 6b , 11c and 12c complexes, respectively. The structure of the bromo-bridged palladium(II) complex [ Pd{4-Me—C 6 H 3 C(H)N Cy}(Br)] 2 ( 3a ) has been determined by X-ray crystallography. The structure has two asymmetrically bridging bromine atoms and a non-bonding Pd ⋯ Pd distance of 341.8(2) pm.

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.

Functionalized palladium(II) cyclometallated complexes. Crystal and molecular structures of [Pd{3-(CHO)C6H3C(H)=NCy}(μ-O2CMe)]2 and [Pd(3-(CHO)C6H3C(H)=NCy}(Cl)(PR3)] (PR3 = PEtPh2, and PEt2Ph)

Abstract The crystal structure of the cyclometallated acetato-bridged complex [Pd{3-(CHO)C6H3C(H)NCy}(μ-O2CMe)]2, 1 is reported. Each palladium atom is C, N-bonded to the chelating Schiff base ligand. The molecular configuration corresponds to the anti isomer, with the cyclopalladated moieties in an ‘open-book’ disposition. Treatment of 1 with aqueous sodium chloride gave the chloro-bridged compound 2, which when treated with tertiary phosphines yielded complexes 3 and 4. The crystal structures of complexes [Pd{3-(CHO)C6H3C(H)NCy}(Cl)( PR3)] (PR3=PEtPh2, 3 and PEt2Ph, 4) are also reported. In both complexes the palladium atom is bonded in a slightly distorted square-planar coordination to a carbon and a nitrogen atom of the Schiff base, a chlorine atom and to the phosphorus atom of the phosphine ligand. The reaction of the chloro-bridged complex 2 with the tertiary diphosphines Ph2PCH2PPh2 (dppm) and Ph2P(CH2)2PPh2 (dppe) in a 1:2 molar ratio, and ammonium hexafluorophosphate, yielded the mononuclear cyclometallated complexes [Pd{3-(CHO)C6H3C(H)NCy}{Ph2PCH2PPh2-P,P}][PF6], 5 and [Pd{3-(CHO)C6H3C(H)NCy}{Ph2P(CH2)2PPh2-P,P}][PF6], 6, respectively.