Francesco Demartin

Preparation and characterization of palladium(II) and platinum(II) complexes with bis(pyrazolyl)alkanes. crystal and molecular structures of [Pd2(pz)22][BF4]2 and of [PdCl2{(CH3)2C(pz)2}] (pzH = pyrazole), a new example of a Pd⋯HC agostic interaction

Abstract Neutral and cationic complexes of general formulae (LL)MCl 2 (M = Pd, (LL) = CH 2 (pz) 2 ( 1 ); CH 2 (3,5-Me 2 pz) 2 ( 2 ); (CH 3 ) 2 C(pz) 2 ( 3 ); M = Pt, (LL) = CH 2 (pz) 2 ( 4 ); CH 2 (3,5-Me 2 pz) 2 ( 5 ) and (LL) 2 M] 2+ (M = Pd, (LL) = CH 2 (pz) 2 ( 6 ); CH 2 (3,5-Me 2 pz) 2 ( 7 ); (CH 3 ) 2 C(pz) 2 ( 8 ); M = Pt, (LL) = CH 2 (pz) 2 ( 9 ); CH 2 (3,5-Me 2 pz) 2 ( 10 ) have been prepared and characterized by IR and 1 H NMR spectroscopy. The structures of 3 and 6 have been determined by X-ray diffraction; in both complexes the bis-(pyrazolyl)alkanes act as chelating ligands but the coordination around the palladium atom in the complex 6 is strictly square-planar whereas in 3 it is a slightly distorted towards pyramidal, with a significant Pd⋯HC agostic interaction. The six-membered rings in both the complexes adopt a boat-type conformations.

Palladium(II) and platinum(II) derivatives with chiral 2,2′-bipyridines. X-ray structure of C18H15ClN2Pd; C- and N-intramolecular coordination in a six-membered metallacycle

Abstract The reactions of (+)-( S )-5-s,butyl-2,2′-bipyridine (LH) and 6-(1-methylbenzyl)-2,2′-bipyridine (L′H) with Na 2 [PdCl 4 ] and K 2 [PtCl 4 ] give the 1 : 1 adducts (LH)MCl 2 (M = Pd, 1 ; M = Pt, 2 ) and the metallated species (L′)MCl (M = Pd, 3 ; M = Pt, 4 ), respectively. In complexes 3 and 4 , the deprotonated bipyridine behaves as a tridentate ligand; there is coordination to the metal through the two nitrogen atoms and the ortho -carbon atom of the phenyl ring to give a six-membered metallacycle. The X-ray structure of complex 3 shows that the coordination around the palladium atom is distorted towards tetrahedral from the usual square-planar geometry.

Chiral atropisomeric five-membered biheteroaromatic diphosphines: New ligands of the bibenzimidazole and biindole series

Abstract Two new chiral atropisomeric biheteroaromatic diphosphines are described: 2,2′-bis(diphenylphosphino)-1,1′-bibenzimidazole (3a) and 3,3′-dimethyl-1,1′-bis(diphenylphosphino)-2,2′-biindole (4a). Structural characterization is given and configurational stability at room temperature demonstrated. The oxidation potential was recognized as a good tool to evaluate the electronic availability of the phosphorus atom in the series of biheteroaromatic diphosphines. Its value increases parallel to the electronic demand of the heterocyclic system and also depends on the position of the diphenylphosphino group.

From red to near infra-red OLEDs: the remarkable effect of changing from X = –Cl to –NCS in a cyclometallated [Pt(N∧C∧N)X] complex {N∧C∧N = 5-mesityl-1,3-di-(2-pyridyl)benzene}

[PtL(6)X] {X = Cl or NCS and L(6) = 5-mesityl-1,3-di(2-pyridyl)-benzene} display similar luminescence in solution but, in the solid state, the packing of the molecules is different, with short PtPt interactions for X = NCS, leading to a red-shifted emission band. The effect has been used to generate OLEDs that emit squarely in the NIR region (855 nm).

Redox chemosensors: coordination chemistry towards CuII, ZnII, CdII, HgII, and PbII of 1-aza-4,10-dithia-7-oxacyclododecane ([12]aneNS2O) and its N-ferrocenylmethyl derivativeElectronic supplementary information (ESI) available: synthetic details including analytical and spectroscopic data for the isolated complexes. Ortep views of the coordination sphere around the metal centres in 1, 2 and 5. See http://www.rsc.org/suppdata/dt/b2/b210806m/

The coordination chemistry of the mixed donor 12-membered macrocyclic ligand 1-aza-4,10-dithia-7-oxacyclododecane ([12]aneNS2O) with CuII, ZnII, CdII, HgII, and PbII has been investigated both in water solution and in the solid state. The protonation constant for [12]aneNS2O and stability constants with the aforementioned metal ions have been determined potentiometrically and compared with those reported for other mixed N/S/O-donor tetradentate 12-membered macrocycles. The measured values are consistent with trends observed previously for aza macrocycles as secondary N-donors are replaced by O- and S-donors. In particular our results show that HgII in water has the highest affinity for [12]aneNS2O followed by CuII, CdII, PbII, and ZnII. For each considered metal ion, 1 ∶ 1 complexes of [12]aneNS2O have been isolated in the solid state; those of CuII, HgII, and CdII have also been characterised by X-ray crystallography. In the cases of copper(II) and cadmium(II) complexes the ligand adopts a folded [2424] conformation, whereas a more planar [3333] conformation is observed in the case of the mercury(II) complex. The macrocycle [12]aneNS2O and its structural analogue [12]aneNS3 have then been used as receptor units in the design and synthesis of the new ferrocene-containing redox-active ionophores N-ferrocenylmethyl 1-aza-4,10-dithia-7-oxacyclododecane (L1) and N-ferrocenylmethyl 1-aza-4,10,7-trithiacyclododecane (L2). Electrochemical studies carried out in MeCN in the presence of increasing amounts of CuII, ZnII, CdII, HgII, and PbII showed that the wave corresponding to the Fc/Fc+ couple of the uncomplexed ionophores L1 and L2 is gradually replaced by a new reversible wave at more positive potentials and corresponding to the Fc/Fc+ couple of the complexed ionophores. The maximum shift of the ferrocene oxidation wave was found for L1 in the presence of ZnII (230 mV) and PbII (220 mV), whereas for L2 a selective sensing response for CuII over the other guest metal cations was observed with an oxidation peak shift of 230 mV.

Investigation of the reactivity of palladium(0) complexes with nitroso compounds: relevance to the palladiumphenanthroline-catalysed carbonylation reactions of nitroarenes

Abstract The electron transfer reaction between palladium(0) complexes and RNO compounds afforded different palladium species depending on the aromatic or aliphatic nature of R. When R=Ph a paramagnetic palladium complex 1 was isolated, whereas if R=Bu t the palladium enolate complex 2 was the unexpected reaction product. Complex 1 reacted with methanol and CO to yield Pd(phen){C(O)OCH 3 } 2 3 , which was characterised by single-crystal X-ray structure determination. Compound 3 is a probable intermediate in the reductive carbonylation reaction of organic nitro compounds catalysed by palladium complexes. Nitrobenzene is in fact carbonylated to PhNHCO 2 Me, by using 3 as a very efficient catalyst.

Cyclometallation of indole derivatives: cyclopalladation of gramine and 1-methyl gramine and CO insertion

Abstract Li 2 PdCl 4 , in methanol, with gramine 1 and 1-methyl gramine 2 gave the dimeric complexes 1a and 2a with chlorine bridges and having the indole nucleus metallated at position 2. The corresponding bromo derivatives 1b and 2b were isolated from the reactions of Pd(OAc) 2 with 1 and 2 , followed by treatment with LiBr. Complexes 1a,b and 2a,b gave the monomeric, cyclometallated derivatives 3a-d by reaction with PPh 3 in methylene chloride. When the cyclopalladation of 1-methyl gramine 1 was attempted by reacting PdCl 2 , PPh 3 and 2 in methanol in the presence of AcOna, an unexpected compound 4 was obtained. A structural determination of 4 showed it consisted of the known [Pd(PPh 3 )Cl 3 ] − anion packed with the dimethyl-bis(3-methylene-1-methyl indole) ammonium cation. When compounds 1a and 2a were reacted with carbon monoxide at atmospheric pressure in methanol or ethanol and in the presence of Net 3 , the corresponding 2-carboalkoxy indole derivatives 5 and 6 were isolated in high yields.

Charge transfer complexes of benzoxazole-2(3H)-thione and benzoxazole-2(3H)-selone with diiodine: X-ray crystal structure of benzoxazole-2(3H)-thione bis(diiodine)

Abstract Solids of stoichiometry 1·I2 (C7H5I2NOS; I), 1·2I2 (C7H5I4NOS; II), 2·I2 (C7H5I2NOSe; III) and 2·2I2 (C7H5I4NOSe; IV) have been obtained by reacting respectively benzoxazole-2(3H)-thione (1) and benzoxazole-2(3H)-selone (2) with molecular diiodine in a 1:1 or 1:2 molar ratio in CH2Cl2 solution. Crystals suitable for X-ray structure determination have been obtained only for II and contain units formed by one diiodine molecule bonded almost linearly [178.44(4)°] to the thionic sulphur atom of 1 and another diiodine molecule weakly interacting with the former. The FT-Raman spectrum in the characteristics v(I-I) region shows two bands for compound II at 176 and 159 cm−1, in accordance with the presence of two differently perturbed diiodine molecules [ I (1)– I (2) = 2.769(1) A , I (3)– I (4) = 2.729(1) A ] . The FT-IR and FT-Raman spectra of compounds I, III and IV are discussed in comparison with the spectrum of II and with those reported for similar charge transfer complexes.

Further investigations of the reactivity of η2-bonded nitroso complexes of platinum: the crystal structure of Pt(PPh3)2(PhNO)

The crystal structure of Pt(PPh3)2(PhNO) (I) has been determined. This is the first example of a structure determination for a monomeric complex of a metal in a low oxidation state and bearing an η2-bonded nitroso ligand. Compound I crystallizes in the monoclinic space group P21/c (no.14) with a 14.228(4), b 13.914(3), c 17.855(4) A, β 100.31 (2)°, V 3478(3) A3 and Z = 4. Final R and Rw indices are 0.026 and 0.030 for 3609 observed reflections (I ⩾ 3 σ(I)). The new complexes Pt(PPh3)2(RNO) (R = But (II), CF3 (III)) have been synthesized and their reactions with CO2, CS2, PhNCO, PhNCS, CO, alkenes and dimethyl acetylenedicarboxylate have been investigated and compared with those of the previously studied compound I. Preliminary observations on the synthesis and reactivity of Pd(PPh3)2(CF3NO) (IV) are also reported.

Ring-Opening of Lawesson’s Reagent: New Syntheses of Phosphono- and Amidophosphono-Dithioato Complexes − Structural and CP-MAS31P-NMR Characterization of [p-CH3OPh(X)PS2]2M (X = MeO,iPrNH; M = NiII, PdII, and PtII)

The opening of the P2S2 tetraatomic ring of Lawesson’s reagent (4) has proved versatile in synthesizing phosphono- and amidophosphono-dithioato mononuclear complexes [p-CH3OPh(X)PS2]2M [X = CH3O, iPrNH; M = NiII, PdII, PtII]. A one-step reaction of 4 with the appropriate metal salt in CH3OH, or in the presence of a stoichiometric amount of iPrNH2 in CHCl3, is used in the direct synthesis of the NiII and PdII complexes, but does not work in the PtII complexes. Alternatively, these syntheses can be carried out: i) by preparation and isolation of O-methyl(4-methoxyphenyl)phosphonodithioate (6) salts or isopropylamido(4-methoxyphenyl)- phosphonodithioate (7) salts by treating 4 with CH3O− in CH3OH or with iPrNH2, respectively; ii) by reaction of 6 or 7 with MCl2 or K2MCl4 [M = NiII, PdII, PtII] to give trans-bis[O-methyl(4-methoxyphenyl)phosphonodithioato]M and trans-bis[isopropylamido(4-methoxyphenyl)phosphonodithioato]M complexes. Following these routes, trans-bis[O-methyl(4-methoxyphenyl)phosphonodithioato]M [M = Ni (8a), Pd (8b), and Pt (8c)] and trans-bis[isopropylamido(4-methoxyphenyl)phosphonodithioato]M [M = Ni (9a), Pd (9b), and Pt (9c)] complexes have been synthesized and fully characterized by FAB mass, FT-IR, FT-Raman, UV/Vis, and CP-MAS 31P-NMR spectroscopy; the crystal structures of 7, 8b, 8c, and 9a are also reported.