Palladium(II)‐ und Platin(II)‐Komplexe mit dem Antimalariamittel Mefloquin als Liganden

Metal Complexes of Biologically Important Ligands. CXXVI. Palladium(II) and Platinum(II) Complexes with the Antimalarial Drug Mefloquine as Ligand The coordination sites of the antimalarial drug mefloquine (L) were studied. Reactions of the chloro bridged complexes (allyl)Pd(μ‐Cl)₂Pd(allyl) and (R₃P)(Cl)M(μ‐Cl)₂M(Cl)(PR₃) (M = Pd, Pt) with racemic mefloquine give the compounds (allyl)(Cl)Pd(L) ( 1 ), Cl₂(Et₃P)Pt(L) ( 2 ) and Cl₂(Et₃P)Pd(L) ( 3 ) with coordination of the piperidine N atom of mefloquine. In the presence of NaOMe the N,O‐chelate complexes Cl(Et₃P)Pt(L–H⁺) ( 4 ) and Cl(R₃P)Pd(L–H⁺) ( 5 , 6 , R = Et, nBu) were obtained. Protection of the piperidine N atom of mefloquine by protonation allows the synthesis of the complexes Cl₂(Et₃P)Pt(L + H⁺) ( 7 ) in which mefloquine is coordinated via the quinoline N atom. The structures of 2 , 3 and 4 were determined by X‐ray diffraction analysis. In the crystal of 4 pairs of enantiomers are found which are linked by two hydrogen bridges between the amine group and the chloro ligand.     

σ–π Continuum in Indole–Palladium(II) Complexes

The intrinsic features of (hetero‐arene)–metal interactions have been elusive mainly because the systematic structure analysis of non‐anchored hetero‐arene–metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non‐anchored indole–palladium(II) complexes. It was revealed that there is a σ–π continuum for the indole–metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland‐intermediate‐type σ‐mode in light of the seemingly strong electron‐donating ability of indole. Several factors which affect the σ‐ or π‐character of indole–metal interactions are discussed.     

π–π Dimerization of a mono(pyridyl–imine) platinum(II) chelate

The cation of the title complex salt, chlorido{2,2‐dimethyl‐N‐[(E)‐1‐(pyridin‐2‐yl)ethylidene]propane‐1,3‐diamine}platinum(II) tetrafluoridoborate, [PtCl(C₁₂H₁₉N₃)]BF₄, exhibits a nominally square‐planar Pt^II ion coordinated to a chloride ion [Pt—Cl = 2.3046 (9) Å] and three unique N‐atom types, viz. pyridine, imine and amine, of the tridentate Schiff base ligand formed by the 1:1 condensation of 1‐(pyridin‐2‐yl)ethanone and 2,2‐dimethylpropane‐1,3‐diamine. The cations are π‐stacked in inversion‐related pairs (dimers), with a mean plane separation of 3.426 Å, an intradimer Pt...Pt separation of 5.0785 (6) Å and a lateral shift of 3.676 Å. The centroid (Cg) of the pyridine ring is positioned approximately over the Pt^II ion of the neighbouring cation (Pt...Cg = 3.503 Å).     

Reaction of a Metallamacrocycle Leading to a Mercury(II)⋅⋅⋅Palladium(II)⋅⋅⋅Mercury(II) Interaction

All wrapped up : The reaction of a 22‐membered macrocycle derived from bis(o‐formylphenyl)mercury and 1,2‐phenylenediamine with palladium(II) results in cleavage of the macrocycle and concomitant formation of a trimetallic complex (see picture; phenyl rings truncated for clarity). The nature of the Hg^II???Pd^II???Hg^II interaction was investigated by theoretical studies.

     

Ligandverhalten von P‐funktionellen Organozinnhalogeniden: Nickel(II)‐, Palladium(II)‐ und Platin(II)‐halogenid‐Komplexe mit Me2(Cl)SnCH2CH2PPh2

Ligand Behaviour of P‐functional Organotin Halides: Nickel(II), Palladium(II), and Platinum(II) Complexes with Me₂(Cl)SnCH₂CH₂PPh₂ Me₂(Cl)SnCH₂CH₂PPh₂ ( 1 ) reacts with Ni^II, Pd^II, and Pt^II halides in molar ratio 2 : 1 forming the complexes [MX₂{PPh₂CH₂CH₂Sn(Cl)Me₂}₂] (M = Ni, Pd, Pt; X = Cl, Br) ( 3 – 6 , 9 , 10 ) ( 7 , 8 : M = Ni; Br instead of Cl). The nickel complexes were isolated and characterized both as the planar ( 3 , 5 , 7 ) and the tetrahedral ( 4 , 6 , 8 ) isomer. Crystal structure analyses and NMR data indicate for the planar nickel complexes 3 , 5 , 7 and [MCl₂{PPh₂CH₂CH₂Sn(Cl)Me₂}₂] ( 9 : M = Pd; 10 : M = Pt) the existence of intra and intermolecular M–Hal…Sn bridges. In a ligand : metal molar ratio of 3 : 1 the complexes [M^éCl{PPh₂CH₂CH₂Sn^⊖Cl₂Me₂}{PPh₂CH₂CH₂Sn(Cl)Me₂}₂] ( 11 : M = Pd; 12 : M = Pt) are formed which represent intramolecular ion pairs. By dehalogenation of [PdCl₂{PPh₂CH₂CH₂Sn(Cl)Me₂}₂] ( 9 ) with sodium amalgam and graphite potassium (C₈K), respectively, the palladacycles cis‐[Pd{PPh₂CH₂CH₂SnMe₂}₂] ( 13 ) and trans‐[Pd(Cl)PPh₂CH₂CH₂SnMe₂{PPh₂CH₂CH₂Sn(Cl)Me₂}] ( 14 ) are formed. From the compounds 1 , 3 , 9 , 11 , and 12 the crystal structures are determined. All compounds are characterized by ¹H, ³¹P, and ¹¹⁹Sn NMR spectroscopy.     

Hydrogen‐bonding and π–π stacking interactions in aquachloridobis(1,10‐phenanthroline)cobalt(II) chloride dichloridobis(1,10‐phenanthroline)cobalt(II) hexahydrate

The title compound, [CoCl(C₁₂H₈N₂)₂(H₂O)]Cl·[CoCl₂(C₁₂H₈N₂)₂]·6H₂O, is the first example of a new 1:1 cocrystal of the octahedral [CoCl₂(phen)₂] and [CoCl(phen)₂(H₂O)]⁺·Cl⁻ complexes (phen is 1,10‐phenanthroline). The latter form heterochiral dimers held by strong π–π stacking interactions via their phenathroline ligands, which confirms that π stacking is an important and reliable synthon in supramolecular design. In addition, the crystal structure is networked by H₂O...H₂O, H₂O...Cl⁻ and H₂O...Cl hydrogen bonds, which interconnect the different units of the cobalt complexes.     

Isolation of a Cationic Platinum(II) σ‐Silane Complex

The platinum complex [Pt(I^tBuⁱPr′)(I^tBuⁱPr)][BAr^F] interacts with tertiary silanes to form stable (<0 °C) mononuclear Pt^II σ‐SiH complexes [Pt(I^tBuⁱPr′)(I^tBuⁱPr)(η¹‐HSiR₃)][BAr^F]. These compounds have been fully characterized, including X‐ray diffraction methods, as the first examples for platinum. DFT calculations (including electronic topological analysis) support the interpretation of the coordination as an unusual η¹‐SiH. However, the energies required for achieving a η²‐SiH mode are rather low, and is consistent with the propensity of these derivatives to undergo Si?H cleavage leading to the more stable silyl species [Pt(SiR₃)(I^tBuⁱPr)₂][BAr^F] at room temperature.