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Bimetallic cyclometallated palladium(II) complexes readily react with silver perchlorate and tertiary diphosphines to give dipalladium compounds with terdentate [C,N,S] thiosemicarbazones, and with bridging and chelating [P,P] ligands, of the type [Pd(Ph2PCH2PPh2-P,P){Pd[4-MeOC6H3C(Me)NNC(S)NHMe](Ph2PCH2PPh2)-P,S}] [ClO4]2, 1a. The crystal structures of complexes [PdCl2{Pd[2-MeOC6H3C(Me)NNC(S)NHMe](Ph2PC(CH2)2PPh2)-P,S}] and [Pd(Ph2PCH2PPh2-P,P){Pd[3-MeOC6H3C(Me)NNC(S)NHMe](Ph2PC(CH2)2P-Ph2)-P,S}]-[ClO4]2, 6 and 4a, respectively, are the first reported examples of palladacycles with the diphosphine Ph2PC(CH2)2PPh2, bis(diphenylphosphine)cyclopropane (dcpc), in the bridging mode. The short-bite diphosphines produce strained four-membered rings at the metal; the structures for 1a and 4a show the P–C–P carbon atom puckered away from the metal coordination plane.

Reaction of the thiosemicarbazones 3-FC6H4C(Me)NN(H) C(S)NHME a, 4-FC6H4C(Me)NN(H)C(S)NHEt b, and 2-BrC 6H4C(Me)NN(H)C(S)NHPh c, with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complexes [Pd{3-FC6H3C(Me)NNC(S)NHMe}] 4 1a, [Pd{4-FC6H3C(Me)NNC-(S)NHEt}]4 1b, and [Pd{2-BrC6H3C(Me)NNC(S)NHPh}]4 1c. Reaction of 1a-c with the diphosphines Ph2P(CH2) nPPh2 dppm (n = 1), dppe (n = 2), dppp (n = 3), dppb (n = 4) or Ph2PCHCHPPh2 trans-dppe, in a 1:2 molar ratio gave the dinuclear phosphine-bridged complexes [(Pd{XC6H 3C(Me)NNC(S)NHR})2(μ-Ph2P(CH 2)nPPh2)] 2a-c, 3a-c, 4a-c, 5a-c (n = 1-4) and [(Pd{XC6H3C(Me)NNC(S)NHR})2(μ-Ph 2PCHCH-PPh2)] 6a-c. Treatment of 1a-c with PPh 2CH2PPh2, dppm, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{XC6H3C(Me)NNC(S) NHR}-(Ph2PCH2PPh2-P)] 7a-c; however, the diphosphines with n ≥ 2 failed to give the analogous reaction. The molecular structures of 1a, 1b and 3c have been determined by X-ray diffraction analysis and the intra- and intermolecular interactions are discussed. © 2011 Elsevier Ltd. All rights reserved.

Treatment of bimetallic palladacycles with silver perchlorate, followed by reaction with tertiary diphosphanes or diphenyl-2-pyridylphosphane gave novel dipalladium compounds with chelating [C,N,S], bridging [P,P], and chelating [P,P] or [P,N] ligands, as appropriate. The short-chain diphenyl-2- pyridylphosphane ligand forms stable four-membered P-N chelates, which display S-Pd-P and N-Pd-P trans geometries. The Pd-Cl bonds are nonreactive towards displacement by the [P,P] or [P,N] ligands, even in the case of strong chelating diphosphanes. New bimetallic palladacycles with bridging [P,P] and chelating [P,P], [P,N], and [C,N,S] donors are reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA.

Treatment of 4-MeOC6H4C(Me)═NN(H)C(═S)NHMe (1), with potassium tetrachloropalladate gave the tetranuclear compound [Pd{4-MeOC6H3C(Me)═NN═C(S)NHMe}]4 (2), with the ligand as terdendate [C,N,S]. Reaction of 2 with the diphosphines Ph2PCH2PPh2 (dppm), Ph2PC(═CH2)PPh2 (vdpp), and Ph2PC(CH2)2PPh2 (dpcp) gave the mononuclear complexes [Pd{4-MeOC6H3C(Me)═NN═C(S)NHMe}(L)] (L = dppm-P, 3; dpcp-P, 4; vdpp-P, 5) with the diphosphine ligand binding in a monodentate fashion. Compounds 3−5 may bond systematically to a second metal atom, palladium or platinum, through the noncoordinated phosphorus atom and the sulfur atom of the thiosemicarbazone moiety to give the dinuclear compounds 6−10, thus behaving as bidentate P,S-palladacycle metaloligands. All the compounds have been characterized by elemental analysis, and by IR and NMR spectroscopy; and the crystal and molecular structures of 1, 2, 6−10 have been determined by X-ray crystallography. Inter- and intramolecular hydrogen bonding in the solid results in crystal se...

The reaction of the tetranuclear halide-bridged complexes 1−2(a−d) with Ph2PCH2PPh2 (dppm) or Ph2PC( CH2)PPh2 (vdpp) in 1:2 molar ratio and NH4PF6 afforded the novel tetarnuclear palladacycles 3−6 (a, c, d) as 1:2 electrolytes with bridging diphosphine and halogen ligands. The structure of 4a has been determined by X-ray diffraction analysis, and represents the first example of a tetranuclear palladacycle with bridging dppm and halogen ligands. Reaction of 1−2(a−d) with (Ph2PCH2CH2)2PPh (triphos) in 1:2 molar ratio gave 7(a−d) bearing two pentacoordinated palladium atoms. The structure of 7a, as determined by X-ray diffraction analysis, shows the distorted square pyramidal geometry around the metal centers. Treatment of 1−2(a−d) with dppm, vdpp or Ph2PN(Me)PPh2 (dppma) in 1:4 molar ratio gave the dinuclear palladacycles 8−10(a−d) with a chelating diphosphine ligand at each metal center; further treatment of 9(a−c) with the nucleophiles pyrrolidine, piperidine, morpholine or 4-methyl-piperidine gave the Michael addition derivatives 11−12(a−c), 13b, 13c and 14c, promoted by the withdrawing effect of the palladacycle which activates the C CH2 double bond.

The reaction of 1-(2,5-dimethylbenzylidene)-3-ethylthiosemicarbazone and palladium acetate in acetic acid yields a trinuclear cyclometallated palladium(II) compound. Each thiosemicarbazone ligand is tridentate with the metal bonded to the carbon atom from the 2-methyl group, to the azomethine nitrogen and to the sulfur atom, which bridges to an adjacent palladium center. The crystal structure confirms the presence of a non-planar hexagonal metallated ring plus a central six-membered palladium–sulfur core within the trimer, which also displays a rather deep intramolecular cavity.

Treatment of thiosemicarbazones (OC4H3)C(Me)= NN(H)C(=S)NHR (R: Me, a; Et, b) with [cis-PtMe2(cod)] afforded the tetranuclear compounds [Pt{(OC4H2)C(Me)=NN=C(S)NHR}] 4 (R: Me, 1a; Et, 1b). The reaction of la and lb with triphenylphosphine in 1:4 molar ratio gave rise to the mononuclear compounds [Pt{(OC4H2)C(Me)=NN=C(S)NHR)(PPh3)] (2a, 2b). Treatment of la and lb with large-bite diphosphines Ph2P(CH 2)nPPh2 (n = 2, dppe; n = 3, dppp; n = 4, dppb) afforded the dinuclear compounds [{Pt[(OC4H2)C(Me) = NN=C(S)NHR]}2{μ-Ph2P(CH2) nPPh2}], (3a-5a, 3b-5b), with the diphosphine in a bridging mode. Similar reactions with the short-bite diphosphines Ph 2PCH2PPh2 (dppm) and Ph2PC(=CH 2)PPh2 (vdpp) yielded the mononuclear compounds [Pt {(OC4H2)C(Me)=NN=C(S)NHR}-(Ph2PCH 2PPh2-P)] (6a, 6b) and [Pt{(OC4H 2)C(Me)=NN=C(S)NHR}(Ph2P-C(= CH2)PPh 2-P)] (7a, 7b) with the diphosphine in a monodentate coordination. Treatment of la and lb with [W(CO)5(Ph2CH 2PPh2)] gave the novel heterodinuclear species [{Pt[(OC4H2)C(Me)=NN= C(S)NHR]}[W(CO)5(Ph 2CH2PPh2-P)}] (8a, 8b), which could also be synthesized by reaction of 6a and 6b with [W(CO)5(THF)], 1H, 31P-{1H} and 13C-{1H} NMR and IR data are given. The crystal structure of compound 3b has been determined by X-ray crystallography. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.

Treatment of the thiosemicarbazones 2-ClC6H4C(Me){double bond, long}NN(H)C({double bond, long}S)NHR, (R: Me, a; Et, b) and 2-BrC6H4C(Me){double bond, long}NN(H)C({double bond, long}S)NHR (R: Me, c; Et, d) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complexes [Pd{2-XC6H3C(Me){double bond, long}NN{double bond, long}C(S)NHR}]4 (X/R: Cl/Me, 1a; Cl/Et, 1b; Br/Me, 1c; Br/Et, 1d). Reaction of 1a-1d with bis(diphenylphosphino)methane, Ph2PCH2PPh2, in a 1:4 molar ratio and concentrated hydrochloric acid gave the mononuclear complexes [Pd{2-XC6H3C(Me){double bond, long}NN(H)-C({double bond, long}S)NHR}(Ph2PCH2PPh2-P,P)](Cl) (2a-2d). Reaction of 1a-1d with bis(diphenylphosphino)methane, Ph2PCH2PPh2, in 1:2 and 1:4 molar ratios gave the dinuclear or mononuclear complexes [{Pd[2-XC6H3C(Me){double bond, long}NN{double bond, long}C(S)NHR]}2(μ-Ph2PCH2PPh2)] (3a-3d), and [Pd{2-XC6H3C(Me){double bond, long}NN{double bond, long}C(S)NHR}(Ph2PCH2PPh2-P)] (4a-4d), with bridging and chelating diphosphine, respectively. The molecular structures of complexes 1b, 1d, 4c and 4d have been determined by X-ray diffraction analysis. © 2006 Elsevier Ltd. All rights reserved.

The reaction of the thiosemicarbazone ligands 1-(COMe)-3-[C(H)=NN(H)C(=S) NHR]C 8 H 5 N, (R = H a, Me b, Et c) with potassium tetrachloropalladate in an ethanol/water mixture led to the new tetranuclear palladium(II) compounds [Pd{1-(COMe)-3-[C(H)=NN=C(S)NHR]C 8 H 4 N-k 3 C5,N,S}] 4 (R = H 1a, Me 1b, Et 1c) which contain six-membered metallacycles. The thiosemicarbazone ligands in these complexes are terdentate through the C, N, and S atoms and are deprotonated at the NH group. The Pd-S bond formed is sufficiently strong to undergo reactions with nucleophiles without bond cleavage. Reaction of 1a and 1b with 1,2-bis(diphenylphosphanyl)ethane (dppe) gave the dinuclear species [{Pd[1-(COMe)-3-{C(H)=NN=C(S)NHR}C 8 H 4 N]} 2 (μ-Ph 2 P(CH 2 ) 2 PPh 2 )] (R = H 2a, Me 2b). The molecular structure of complex 1b has been determined by X-ray diffraction analysis. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Treatment of the thiosemicarbazones 4-FC6H4C(Me) NN(H)C( S)NHR, (R = Me, a; Ph, b) and 2-ClC6H4C(Me) NN(H)C( S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC6H3C(Me) NN C(S)NHR}]4 (1a, 1b) and [Pd{2-ClC6H3C(Me) NN C(S)NHPh}]4 (1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC6H3C(Me) NN C(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC6H3C(Me) NN C(S)NHPh})2(μ-Ph2PCH CHPPh2)], (3a, 3b) and [(Pd{2-ClC6H3C(Me) NN C(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC6H3C(Me) NN C(S)NHPh})2(μ-PPh2CH CHPPh2)], (3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.

The reaction of the thiosemicarbazones (η5-C5H5)Fe(η5-C5H4)C(H) NN(H)C( S)NHR (R = H, a; R = Me, b) with K2PdCl4 afforded octanuclear cyclometallated complexes [Pd{(η5-C5H5)Fe(η5-C5H3)C(H) NN C(S)NHR}]4 (R = H, 1a; R = Me, 1b). Reaction of complexes 1a and 1b with tertiary diphosphines in 1:2 molar ratio and subsequent recrystallization from CH2Cl2/n-C6H14 gave rise to tetranuclear complexes [{Pd[(η5-C5H5)Fe(η5-C5H4)C(H) NN C(S)NHR](Cl)}2(μ-Ph2P(CH2)nPPh2)] (R = H, n = 4, 2a; R = Me, n = 1, 2b; n = 4, 3b). Treatment of complexes 1a and 1b with tertiary monophosphines in 1:4 molar ratio and subsequent recrystallization from CH2Cl2/n-C6H14 gave rise to dinuclear complexes [Pd{(η5-C5H5)Fe(η5-C5H4)C(H) NN C(S)–NHR}(Cl)(P)] (R = H: P = PPh3, 3a; P = PPh2Et, 4a; P = P(C6D5)3, 5a; R = Me: P = PPh3, 4b; P = PPh2Et, 5b; P = P(C6D5)3, 6b). The crystal structures of 2a and 2b have been determined by X-ray crystallography.

Treatment of the thiosemicarbazone 2-FC6H4C(Me)= NN(H)C(=S)NHPh, a, with palladium(II) acetate in acetic acid, or with lithium tetrachloropalladate(II) in methanol, gave the tetranuclear cyclometallated complex [Pd{2-FC6H3C(Me)=NN= C(S)NHPh}]4 (1a). Reaction of 1a with the diphosphines Ph2P(CH2) 2PPh2 (dppe), Ph2PCH=CHPPh2 (trans-dpe) Ph2P(CH2)3Ph2 (dppp) or Ph2P(CH2)4Ph2 (dppb) in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{2-FC6H 3C(Me)=NN=C(S)NHPh})2(μ-Ph2P(CH 2)nPPh2)], (n = 2, 2a; 3, 4a; 4, 5a) and [(Pd{2-FC6H3C(Me)=NN=C(S)NHPh})2(μ-Ph 2PCH=CHPPh2)], (3a). The X-ray crystal structure of ligand a and of complex 2a are described. The structure of complex 2a shows the palladium atom is bonded to four different donor atoms: C, N, S and P. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

A soil-extracted fulvic acid of low concentration (10 and 30 mg l −1 ) was titrated potentiometrically in the presence of variable concentrations of KNO 3 (0.01, 0.05, 0.1 and 1.0 M) as background electrolyte in such a way that the carbon content in the medium was the same as that of dissolved organic carbon present in natural freshwater. The data were analyzed following the master curve approach and local isotherm approximation methods. The affinity distribution calculated by using the spherical double layer model at higher fulvic acid concentration and the cylindrical double layer model at lower fulvic acid concentration were coincident. An electrostatic discrete ligand model was used to fit data to the presence of two types of acidic sites the intrinsic constants of which were computed by using the geometries estimated in constructing the master curve to calculate the electrostatic term. The intrinsic constants obtained, coincide with the positions of the maxima in the affinity distribution.

The complexation equilibria of the amino acids l -serine and l -leucine with the ions Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ have been studied at 298 K and ionic strength I = 0.1 M in various ethanol-water media. The complexes found and their equilibrium constants are discussed in terms of the acid-base characteristics of the amino acids and the properties of the cations.

The stability constants of Ni(II) complexes containing alcoholamines were determined by potentiometric titration in aqueous solutions at several ionic strengths. The influence of temperature and ligand substituents are examined.