M. Teresa Pereira

Synthesis of complexes of platinum (II) with C,N,N′-terdentate Schiff base donor ligands. Crystal and molecular structure of [Pt{3-Me-4-MeOC6H2C(H)NCH2CH2NMe2}(Me)]

Abstract Treatment of the potentially terdentate ligands C6RxH5−xC(H)N–CH2CH2NMe2 [R: a (x=2), 2,4-(MeO)2; b (x=2), 3,4-(MeO)2; c (x=2), 3-Me-4-MeO; d (x=3), 2,3,4-(MeO)3; e (x=2), 4,5-(OCH2O); f (x=1), 2-NO2] with [PtMe2(COD)] gave the platinated compounds [Pt{C6RxH4−xC(H)NCH2CH2–NMe2}(Me)] with two fused five-membered rings at platinum. The crystal and molecular structure of [Pt{3-Me-4-MeOC6H2C(H)NCH2CH2NMe2}(Me)] has been determined by X-ray crystallography. The reactivity of these complexes was tested by the reactions of [Pt{2,4-(MeO)2C6H2C(H)NCH2CH2NMe2}–(Me)] with tertiary phosphines and diphosphines. In the latter case, dinuclear and mononuclear platinum complexes were synthesized, with bridging or chelating diphosphine ligands, respectively, depending on the complex/diphosphine molar ratio used. The reaction of the related potentially hexadentate ligand 1,4-[Me2NCH2CH2N(H)C]2C6H4 with [PtMe2(COD)] gave the metallated compound [(Me)Pt{Me2NCH2CH2N(H)C}C6H2{C(H)N–CH2CH2NMe2}Pt(Me)] with five fused rings.

Reactivity of functionalised cyclometallated complexes of palladium(II). Crystal and molecular structure of [Pd{3-(CHO)C6H3C(H)NCy}(Br)(PEtPh2)]

Abstract Treatment of the cyclometallated complexes [{Pd[3-(CHO)C 6 H 3 C(H)NCy}(X)} 2 ] [X=Cl ( 1 ), Br ( 2 ), I ( 3 )] with tertiary monophosphines in a complex/phosphine 1:2 or 1:4 molar ratio afforded the halide-bridged cleaved [Pd{3-(CHO)C 6 H 3 C(H)NCy}(X)(L)] ( 6 – 17 ) and non-cyclometallated complexes [Pd{3-(CHO)C 6 H 3 C(H)NCy}(X)(L) 2 ] ( 18 – 23 ) (X=Cl, Br or I; L=PPh 3 , PEtPh 2 , PEt 2 Ph or PMePh 2 ), respectively. Reaction of 6 – 17 with cyclohexylamine in a complex/amine 1:1 or 1:2 molar ratio gave [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(L)] ( 24 – 28 ) and the non-cyclometallated [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(L)(NH 2 Cy)] ( 29 – 32 ) complexes, respectively. Compounds 18 , 19 and 22 gave [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(PR 3 ) 2 ] ( 33 – 35 ) with two uncoordinated CN groups, when treated with cyclohexylamine. Other reaction routes are also discussed. The complexes were characterised by their elemental analysis (C, H, N) and by IR and 31 P{ 1 H} and 1 H-NMR data, and [Pd{3-(CHO)(C 6 H 3 C(H)NCy}(Br)(PEtPh 2 )] ( 12 ) was characterised crystallographically.

Sterically controlled reactivity of palladium(ii) tetranuclear cyclometallated complexes. Crystal and molecular structure of the novel tetranuclear compound [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(µ-Cl)(Cl)(PPh3)]2Electronic supplementary information (ESI) available: 1H and 31P NMR data for compounds 1–15 and 17. See http://www.rsc.org/suppdata/nj/b1/b111671a/

The reaction of the Schiff base ligands 1,3-[CN(H)CH2C4H7O]2C6H4 (1) and 1,4-[CN(H)CH2C4H7O]2C6H4 (14) with palladium(II) acetate in toluene gave the acetato-bridged cyclometallated compounds [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(μ-AcO)2]2 (2) and [(μ-AcO)Pd{1,4-[C(H)NCH2C4H7O]2C6H2}Pd(μ-AcO)]n (15). Reaction of 2 and 15 with aqueous sodium chloride gave the chloro-bridged cyclometallated compounds [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(μ-Cl)2]2 (3) and [(μ-Cl)Pd{1,4-[C(H)NCH2C4H7O]2C6H2}Pd(μ-Cl)]n (16), respectively, after a metathesis reaction. Reaction of 3 with triphenylphosphine in a 1∶2 molar ratio gave the tetranuclear complex [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(μ-Cl)(Cl)(PPh3)]2 (4), where only one of the bridging PdCl2Pd moieties was cleaved, and which was characterized by X-ray crystal structure analysis. However, reaction of 16 with PPh3 gave the dinuclear complex [(PPh3)(Cl)Pd{1,4-[C(H)NCH2C4H7O]2C6H2}Pd(PPh3)(Cl)] (17) after a full bridge-splitting reaction. Similarly, treatment of 3 with PMe2Ph, pyridine and thallium acetylacetonate produced the dinuclear complexes 5, 6 and 7, respectively. Treatment of 4 with pyridine in a 1∶2 molar ratio, and with 4,4′-dipyridyl in an 1∶1 molar ratio, gave the di- and tetranuclear complexes 12 and 13, respectively. Reaction of 3 with the tertiary diphosphine cis-Ph2PCHCHPPh2 in a 1∶2 molar ratio yielded the tetranuclear complex [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(μ-Cl)(Ph2PCHCHPPh2-P,P)][Cl]2 (8) after selective splitting of one of the PdCl2Pd bridging moieties. However, reaction of 3 with cis-Ph2PCHCHPPh2 and Ph2P(CH2)2PPh2 in 1∶4 molar ratios gave the dinuclear complexes 9 and 10, respectively. Reaction of 3 with the diphosphine Ph2PC5H4FeC5H4PPh2 in a 1∶2 molar ratio yielded the trinuclear complex [Pd2{1,3-[C(H)NCH2C4H7O]2C6H2}(μ-Ph2PC5H4FeC5H4PPh2)] (11), with the diphosphine bridging the two palladium atoms of the dicyclometallated moiety.

Cyclometallated complexes of Pd(II) with heterobidentate P, As and P, N coordinating ligands

Treatment of the choride-bridged dimer [Pd{4-(COH)C6H3C(H)/N(Cy)/C2 ,N }(m-Cl)]2 (1), with Ph2PCH2CH2AsPh2 (arphos) in 1:1 molar ratio in acetone gave the dinuclear complex [{Pd[4-(COH)C6H3C(H)/N(Cy)/C2 ,N ](Cl)}2(m-Ph2PCH2CH2AsPh2)] (2), with the arsinophosphine as a bridging ligand, and in 1:2 molar ratio in the presence of NH4PF6 gave the mononuclear compound [Pd{4-(COH)C6H3C(H)/N(Cy)/C2 ,N }(Ph2PCH2CH2AsPh2/P ,As )][PF6], (3), with the arsinophosphine chelated to the metal center. Reaction of 1 with Ph2PCH2CH2CH2NH2 in 1:2 molar ratio in acetone and NH4PF6 afforded [Pd{4-(COH)C6H3C(H)/ N(Cy)/C2 ,N }{Ph2PCH2CH2CH2N(/CMe2)/P ,N }][PF6 ]( 4), after intermolecular condensation between the aminophosphine and the solvent. Condensation was precluded by treatment in toluene to give the mononuclear compound [Pd{4-(COH)C6H3C(H)/ N(Cy)/C2 ,N }(Ph2PCH2CH2CH2NH2/P ,N )][PF6], (5). 1 H, 31 P{ 1 H} and 13 C{ 1 H}-NMR, IR and mass spectral data are given. The crystal structures of compounds 2 � /4 have been determined by X-Ray crystallography. # 2002 Elsevier Science B.V. All rights reserved.

A Highly Effective Strategy for Encapsulating Potassium Cations in Small Crown Ether Rings on a Dinuclear Palladium Complex

The potential of 15-crown-5 ethers to link large cations, such as potassium, is limited by the quasi-parallel arrangement of two oxygen donor moieties upon appropriate orientation of the corresponding ether-ring-containing molecules. Substrates bearing the two crown ethers that are capable of achieving such coordination are hitherto unknown. The synthesis and isolation of a tailor-made dinuclear palladacycle bearing 15-crown-5 ether rings on the metallated phenyls offers such a possibility, providing the adequate environment for the formation of the sandwiched [K(metallacycle-15-crown-5)2 ] moiety. This synthetic strategy also culminates in the isolation of the first palladacycle able to entrap a potassium cation through bonding to two 15-crown-5 ether rings in a single molecule.

Palladacycle catalysis: an innovation to the Suzuki-Miyaura cross-coupling reaction.

Herein we report a Suzuki-Miyaura type cross-coupling between an aryl halide and a functionalized boronic acid palladacycle in the absence of an external catalyst. This reaction is an unprecedented case of catalysis in palladium metallacycle chemistry.

From Chemical Serendipity to Translational Chemistry: New Findings in the Reactivity of Palladacycles

Abstract In the world of science, in particular the section concerning the field of chemistry, when the results encountered during the experiment do not meet our expectations, our shrewdness may play an important role to open up new unexplored fields that could be much more interesting than what we were seeking. In those cases, our research undergoes an unforeseen shift, delivering novel and challenging results that may altogether alter our point of view and our future work. We have then struck serendipity. Specifically, in our investigation linked to palladacycles we have found that the new trends in their reactivity, as well as in their structure, have been, in many cases, related to this experience, broadening our research scope within this field. Herein, we describe our most relevant findings, which have shed new light upon the reactivity of palladacycles, thus opening new routes that lead to novel unexpected structures.

Synthesis, coordination properties and DFT studies of novel trans-disubstituted hexaaza-macrocycles containing pyridine and/or ethyldioxolane arms

Abstract Novel trans-disubstituted hexaaza-macrocyclic ligands L1 and L2 were successfully prepared by the alkylation of the trans secondary amines presented in L with pyridine and ethyldioxolane groups, respectively. The coordination properties of compounds L1 and L2 towards different transition, post-transition and lanthanoid metal ions were explored. Colorless crystals of [NaL1]I and L2´Br2, suitable for X-ray diffraction, were obtained by slow evaporation of an acetonitrile solution of compounds L1 or L2, showing an anti conformation between the methyl groups and the pendant arms in trans positions. The [ML1]n+ (M = Ni2+, Cu2+, Zn2+) systems were investigated by DFT calculations (B3LYP model).