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[Ag(OTf)L] complexes (L = RR′Se) were prepared, structurally characterized and tested for their in vitro antiproliferative activity.

This chapter highlights recent insights of pincer chemistry, regarding pincer chalcogenones and their metal complexes. Due to the diversity of the proligands and the quite large number of pincer–metal complexes, only compounds with heavier chalcogens (S, Se) in the pincer ligand are considered. Classical, symmetric proligands which can afford anionic pincer ligands or can behave as neutral pincer ligands resulting in metal complexes with fused 5- or 6-membered metallacycles are discussed, emphasizing general and specific methods of synthesis as well as their structural characteristics and reactivity. The ligands considered in this chapter are those based on a phenylene/heterophenylene (substituted pyridine or phosphinine) unit or a 5-membered cyclic fragment (e.g., indenyl, pyrrole, and related rings) as the central core, substituted with two side arms containing EZ groups. A particular designation of such ligands is used to show not only the donor atoms, but also the atoms to which the donors are bound and the size of the fused metallacycles formed by complexation, e.g., [(EZ)/X/(ZE]-5,5 (E = S, Se; Z = C, P; X = C, N). Applications of selected metal complexes in catalysis, biology, and materials science are briefly mentioned.

The reaction between CdCl2 and PPh2{C6H4 [CH2N(CH2CH2)2O]-2} (1) in a 1:1 molar ratio resulted in the cadmium(II) complex CdCl2[PPh2{C6H4[CH2N(CH2CH2)2O]-2}] (2). The complex 2 was characterized in solution by NMR spectroscopy (1H, 13C, and 31P). Single-crystal X-ray diffraction studies revealed no intramolecular N→P interaction in 1. The phosphane ligand behaves as a P,N chelating moiety in the cadmium complex 2, thus resulting in a species containing distorted tetrahedral environments around cadmium and phosphorus. Short intermolecular interactions CH‧‧‧π aryl and CH‧‧‧O in 1 and CH‧‧‧π aryl and CH‧‧‧Cl in 2 resulted in supramolecular networks.

The diorganotin(IV) compound Ph2Sn(S2CNMe2)(NCS) (3) was obtained by reacting either Ph2Sn(SCN)2 (1) or Ph2Sn(S2CNMe2)Cl (2) with sodium dimethyldithiocarbamate, in a 1:1 molar ratio, in CH2Cl2. Multinuclear (1H, 13C and 119Sn) NMR spectroscopy and mass spectrometry were used to characterize the new complex. Single-crystal X-ray diffraction studies revealed a bidentate behaviour of the dithiocarbamato ligand and a monodentate coordination of the NCS moiety through its nitrogen atom, thus resulting in a pentacoordinated C2SnS2N core. A 3D supramolecular network built through weak intermolecular S∙∙∙S and S∙∙∙H interactions was evidenced in the crystal of 3.

Hypercoordinated triaryltelluronium compounds of type [{2-(Me2NCH2)C6H4}3Te]+L [L = (SPMe2)2N (1), (OPPh2)2N (2), (SPPh2)2N (3), (SPPh2){OP(OEt)2}N (4), (SPPh2)(O2SMe)N (5) and {SP(OEt)2}(O2SC6H4Cl-4)N (6)] were prepared by salt metathesis reactions between [{2-(Me2NCH2)C6H4}3Te]Cl•H2O and the potassium salts of the corresponding organophosphorus ligands in a 1:1 molar ratio. Multinuclear NMR spectroscopy, mass spectrometry, molar conductivity and IR spectroscopy were used to characterize the new complexes. The 1H NMR spectra suggest for all compounds the intramolecular coordination of the nitrogen atoms from the pendant arms to tellurium in solution. For compound 3 single-crystal X-ray diffraction studies revealed strong N→Te intramolecular interactions in solid state, which result in hypercoordinated triaryltelluronium(IV) cations (14‒Te‒6 species) with a distorted octahedral coordination geometry around tellurium. Weak S⋅⋅⋅H interactions between anions and cations resulted in a 2D supramolecular network.

The compound [2,6-(Me2NCH2)2C6H3]Hg(OAc) (1) was prepared by direct mercuration of 1,3-(Me2NCH2)2C6H4 with Hg(OAc)2. Treatment of 1 with excess of LiCl resulted in isolation of the chloride [2,6-(Me2NCH2)2C6H3]HgCl (2) in a good yield. The IR spectroscopy confirms the presence of the acetate group in 1. Both compounds 1 and 2 were characterized by solution multinuclear (1H, 13C and 199Hg) NMR spectroscopy and mass spectrometry. Their crystal and molecular structures were established by single-crystal X-ray diffraction. Different intermolecular interactions, i.e. Hg···Hg, O···Hg and C‒H···π (Arcentroid), were found for both compounds in solid state resulting in dimer or chain polymer associations.

The new diorganodiselenides [2,6-{E(CH2CH2)2NCH2}2C6H3]2Se2 (E = MeN, O) with N,C,N pincer groups were oxidized with SO2Cl2 to the corresponding organoselenium(II) chlorides of type [2,6-{E(CH2CH2)2NCH2}2C6H3]SeCl. The new chlorides, as well as the related [2,6-(Me2NCH2)2C6H3]SeCl, transfer easily the chlorine atom to [AuCl(tht)] (tht = tetrahydrothiophene), thus forming ionic species based on the organoselenium cations [2,6-{E(CH2CH2)2NCH2}2C6H3Se]+ or [2,6-(Me2NCH2)2C6H3Se]+ and the [AuCl2]− anion. The reaction between [2,6-(Me2NCH2)2C6H3]2Se2 and [(C6F5)Au(tht)] resulted in an ionic species as well, i.e. [2,6-(Me2NCH2)2C6H3Se]+[Au(C6F5)2]−. The room temperature 1H NMR spectra suggest a fast dynamic behavior in solution for all species, except the ionic [2,6-{O(CH2CH2)2NCH2}2C6H3Se]+Cl− and [2,6-(Me2NCH2)2C6H3Se]+[Au(C6F5)2]−, for which the 1H NMR resonances in the aliphatic region suggest that both N→Se intramolecular interactions are preserved in solution. The solid state structures of {[2,6-{O(CH2CH2)2NCH2}2C6H3Se]+Cl−}·H2O, [2,6-(Me2NCH2)2C6H3Se]+[AuCl2]− and [2,6-(Me2NCH2)2C6H3Se]+[Au(C6F5)2]− were established by single-crystal X-ray diffraction.

Several homo- and heteroleptic diorganotin(IV) dithiocarbamato halides of type RR'Sn(S2CNR″2)Cl [R = R' = Me, R'' = Me (1), Et (2); R = R' = nBu, R'' = Me (3), Et (4); R = 2-(Me2NCH2)C6H4, R' = Me, R'' = Me (5), Et (6)] and pseudo-halides of type RR'Sn(S2CNR″2)(NCS) [R = R' = Me, R'' = Me (7), Et (8); R = R' = nBu, R'' = Me (9), Et (10); R = 2-(Me2NCH2)C6H4, R' = Me, R'' = Me (11), Et (12); R' = nBu, R'' = Et (13), R' = 2-(Me2NCH2)C6H4, R'' = Me (14), Et (15)] were prepared by salt metathesis reactions, starting from either RR'SnCl2 or RR'Sn(NCS)2. In all compounds the dithiocarbamato ligand acts as a bidentate moiety. For the compounds 11–15, as well as for the species 5 and 6, of type RR'Sn(S2CNR″2)Cl, bearing aromatic groups with pendant arms attached to tin, the NMR spectra gave no clear evidence for a N→Sn coordination in solution at room temperature. The molecular structures determined by single-crystal X-ray diffraction for compounds 12 and 14, with one or two 2-(Me2NCH2)C6H4 groups, respectively, revealed the existence of intramolecular N→Sn interactions in solid state. The IR spectra suggest an isothiocyanato behavior of the NCS group in solid state in all cases, while the 119Sn NMR spectra gave no clear evidence for such a behavior in solution, as no 14N-119Sn couplings were observed. The single-crystal X-ray diffraction studies revealed molecular species for 7, 8 and 12, while 14 is a ionic compound with [{2-(Me2NCH2)C6H4}2Sn(S2CNMe2)]+ cations and SCN− anions.

Heteroleptic triorganotelluronium chlorides of the type [RPh2Te]+Cl− (1) and [R2PhTe]+Cl− (4) [R = 2-(Me2NCH2)C6H4] were obtained by reacting Ph2TeCl2 with RLi in 1 : 1 and 1 : 2 molar ratios. The reaction of TeCl4 with RLi (a 1 : 3 molar ratio) afforded a mixture of [R3Te]+Cl− (7) and [R2Te(OH)]+Cl− (10) after separation by column chromatography. Halogen exchange reactions using KX resulted in the corresponding [RPh2Te]+X− [X = Br (2), I (3)], [R2PhTe]+X− [X = Br (5), I (6)] and [R3Te]+X− [X = Br (8), I (9)]. The compounds were characterized by multinuclear NMR spectroscopy and mass spectrometry. The NMR spectra are similar for each series of triorganotelluronium halides (1–3, 4–6 and 7–9, respectively) and no clear evidence for N→Te interactions in solution could be concluded at room temperature, except in the case of compounds 4–6 for which the 1H resonance of the CH2N protons in the pendant arms appears as an AB spin system. For compounds 7 and 10 the low temperature 1H and 13C NMR spectra are consistent with intramolecularly coordinated pendant arms. The solid state structures for compounds 1, 1·0.5CH2Cl2, 3, 4·H2O, 5·H2O, 6, 7·H2O and 10 were determined by single-crystal X-ray diffraction. For all compounds the nitrogen atom of a pendant arm is involved in an intramolecular N→Te interaction in the range 2.571(3)–2.839(8) A. This results in hypercoordinated triorganotelluronium(IV) cations with different distorted coordination geometries: “see saw” in 1–3, square pyramidal in 4–6 and 10, and octahedral in 7. Further secondary interactions between cations, anions and water molecules were observed in the crystals of these species, resulting in different supramolecular associations.

The triarylphosphanes P(C6H4CH2NEt2-2)nPh3-n [n = 1 (1), 2 (2)] were obtained by reacting Ph2PCl or PhPCl2 with [2-(Et2NCH2)C6H4]Li in a 1:1 and a 1:2 molar ratio, respectively. Further oxidation with elemental sulfur or elemental selenium powder resulted in the triorganophosphane chalcogenides EP(C6H4CH2NEt2-2)nPh3-n [E = S, n = 1 (3), 2 (5); E = Se; n = 1 (4), 2 (6)]. The copper(I) complexes [CuCl{P(C6H4CH2NEt2-2)nPh3-n}] [n = 1 (7), 2 (8)] were prepared by the reactions between the triarylphosphanes 1 and 2 with CuCl in a 1:1 molar ratio. The new species were investigated in solution by NMR spectroscopy. The single crystal X-ray diffraction studies revealed a monomeric structure for the triorganophosphane sulphides 3 and 5, while the copper(I) complexes 7 and 8 form dimers by bridging chlorine atoms. In both copper complexes the phosphane ligands behave as C,N chelating moieties. For compound 8 the two C6H4CH2NEt2-2 groups are equivalent in solution, while in solid state only for one of them the N→Cu intramolecular interaction was observed.

The diorganoselenide [Me2C(OH)CH2]2Se (1) was prepared by reacting the in situ obtained Na2Se with 1‐chloro‑2‐methyl‐2‐propanol. Reactions of 1 and [2-(Me2NCH2)C6H4]2Se (2) with appropriate silver(I) salts in 1:1 molar ratio resulted in metal complexes of type [Ag(X)Se{CH2C(OH)Me2}2] [X = OSO2CF3 (OTf) (3), OClO3 (4)] and [Ag(X)Se{C6H4(CH2NMe2)-2}2] [X = OSO2CF3 (5), ONO2 (6)], respectively. The ligand 1 and the silver complexes were investigated by appropriate spectroscopic methods, both in solution and in solid state: multinuclear NMR (1H, 13C, 19F, 77Se), ESI+ mass spectrometry, IR spectroscopy and molar conductivity. The metal complexes behave as 1:1 electrolytes in 10−3 MeOH solutions, while in solid state the anionic ligands behave as monodentate moieties. Complexes 4 and 5 were investigated by single‐crystal X‐ray diffraction. The crystal of 4 contains two similar independent molecules, 4a and 4b, for which was observed the migration of one OH hydrogen from ligand 1 to the OClO3 group, thus resulting in [Ag(HClO4)Se{OCCH2Me2}{(OH)CCH2Me2}], where ligand 1 behaves as an O,Se monometallic biconective moiety. In 5 the ligand 2 acts as a N,Se,N monometallic triconective moiety. In both compounds Ag(I) is surrounded by the donor atoms in a trigonal pyramidal coordination geometry. Strong Se→Ag intermolecular interactions in 4 resulted in 1D coordination polymers built by 4a and 4b molecules, respectively, while in the crystal of 5 no interaction between heavy atoms was observed. Supramolecular networks based on H‧‧‧O contacts are formed in both compounds.

New diorganobismuth(III) bromides of type [RN(CH2C6H4)2]BiBr [R = C6H5CH2 (1), C6H5CH2CH2 (2), and CH3OCH2CH2 (3)], based on the heterocyclic butterfly-like tetrahydro-dibenzo[c,f][1,5]azabismocine framework, were prepared starting from the corresponding RN(CH2C6H4Br-2)2 in a succession of reactions including ortho-lithiation and treatment of the dilithio derivative with BiBr3 in a 1 : 1 molar ratio. Further exchange reactions between bromides and appropriate metal halides or ammonium fluoride resulted in the formation of [RN(CH2C6H4)2]BiX [X = Cl and I for R = C6H5CH2 (4 and 5) and C6H5CH2CH2 (6 and 7) and X = F (8), Cl (9), and I (10) for R = CH3OCH2CH2]. All ten compounds were structurally characterized in solution by NMR and in the solid state by single-crystal X-ray diffraction. Strong transannular N→Bi interactions were observed in all the investigated diorganobismuth(III) halides, thus giving rise to hypervalent 10–Bi–4 species in 1, 2, 4–7 and 12–Bi–5 species in 3, 8–10, where the oxygen atom in the pendant arm is intramolecularly coordinated to bismuth. The molecules are associated in dimeric units by strong Bi⋯π arene interactions in 3, 4, and 10 (approx. 3.50 A) and by Bi⋯X interactions in 1, 5, and 7. Bromide 1, chloride 4, and iodide 5 are isostructural, but stronger polarization of the Bi–Cl bond favors Bi⋯π arene interaction in 4 over Bi⋯halide interactions, as observed in 1 and 5. In the isostructural series [RN(CH2C6H4)2]BiX (R = CH3OCH2CH2), Bi⋯oxygen interactions compensate the electron deficiency at bismuth in fluoride 8 and chloride 9, whereas the coordination sphere of bismuth is completed by a combination of Bi⋯π arene and Bi⋯halide interactions in bromide 3 and only by Bi⋯π arene interactions in iodide 10. Moreover, weak H⋯π arene and H⋯X intermolecular interactions, mainly of dispersion type, contribute to supramolecular networks in all three series of compounds.

Diorganodichalcogenides of type [2-(C6H5O)C6H4]2E2 [E S (1), Se (2), Te (3)] were prepared and structurally characterized by multinuclear NMR (1H, 13C, 77Se or 125Te, as appropriate) and ESI+ mass spectrometry. The oxidation reaction of the diorganodichalcogenides 2 and 3 with SO2Cl2 under anhydrous conditions led to the phenoxaselenine 10,10-dichloride (5) and to the organotellurium trichloride, [2-(C6H5O)C6H4]TeCl3 (4), respectively. Further hydrolysis with a KOH solution led to a mixture of phenoxachalcogenine 10-oxide [chalcogen = Se (7), Te (8)] and phenoxachalcogenine [chalcogen = Se (9), Te (10)] in each case. The crystal and molecular structures of compounds 2–5 and 7 were determined by single-crystal X-ray diffraction.

Cobalt(II) complexes of type [Co{(XPR2)(O2SR′)N}2] [X = S; R = Ph; R′ = Me (1), Ph (2), C6H4CH3-4 (3); X = O; R = Ph, R′ = Ph (4), R = OEt, R′ = C6H4CH3-4 (5)] were prepared by salt metathesis reactions between CoCl2·6H2O and the potassium salt of the appropriate organophosphorus acid in a 1:2 M ratio. All compounds were characterized by UV–Vis spectroscopy in CH2Cl2 solutions, mass spectrometry, infrared spectroscopy and room temperature magnetic susceptibility. For compounds 1 and 5 electronic spectra were recorded in dimethylformamide (dmfa) as well. While the electronic spectra suggest a monomeric structure in CH2Cl2 solutions with a tetrahedral environment about cobalt(II), for compound 3 in solid state a dinuclear structure was determined by single-crystal X-ray diffraction, with two bridging S,O,O-bimetallic triconnective and two S,O-monometallic biconnective [(SPPh2)(O2SC6H4CH3-4)N]− ligand units. From a CH2Cl2 solution of 1 crystals of the oxidation product [Co(OH){(SPPh2)(O2SMe)N}2] (6) were isolated after standing for several weeks in open atmosphere. Compound 4 in dimethylformamide decomposed and formed the octahedral species [Co(O2PPh2)2(HO2PPh2)2(dmfa)2] (7) (dmfa = dimethylformamide). The redox behavior of 1 was investigated by cyclic voltammetry in CH2Cl2 solution.

Several new diorganobismuth(III) compounds based on a butterfly-like tetrahydro-dibenzo[c,f][1,5] thiabismocine heterocyclic framework were prepared and structurally characterized. The reaction between the dilithio derivative of bis(2-bromobenzyl)sulfane with BiBr3 in a 1:1 M ratio resulted in the formation of [(C6H4CH2)2S]BiBr (1). Further exchange reactions of 1 with KI, AgNO3 and AgOSO2CF3, respectively, afforded the hypervalent species [(C6H4CH2)2S]BiX [X = I (2), ONO2 (3) and OSO2CF3 (4)]. The new species were characterized by 1H and 13C NMR, FT IR spectroscopy and mass spectrometry. The crystal and molecular structures of compounds 1–4 were determined by single-crystal X-ray diffraction. In all compounds the sulfur atom is strongly intramolecularly coordinated to bismuth, thus resulting in hypervalent species 10-Bi-4 (for 1 and 2) and 12-Bi-5 (for 3 and 4). Intermolecular interactions (X…Hmethylene in 1 and 2, Bi…Cg in 3 and Bi…O in 4) led to polymeric chains in the crystals. DFT calculations were carried out on [(C6H4CH2)2S]BiCl and 1–4 in order to better understand the S→Bi intramolecular coordination.

Triorganotelluronium complexes of type [{2-(Me2NCH2)C6H4}nPh3-nTe]L [(L = S2PMe2, n = 3 (1), 1 (2); L = (EPPh2)2N, E = S, n = 3 (3); E = Se, n = 3 (4), 2 (5), 1 (6) and L = (SPPh2)(O2SC6H4CH3-4)N, n = 3 (7), 2 (8), 1 (9)] were obtained by salt metathesis reactions between triaryltelluronium halides of type [{2-(Me2NCH2)C6H4}nPh3-nTe]X (X = Cl, Br) and the alkali metal salt of the corresponding organophosphorus acid in a 1:1 molar ratio. The new ionic species were characterized by multinuclear NMR spectroscopy and mass spectrometry. The NMR spectra show similar resonances for each series of triorganotelluronium complexes (1 and 2, 3–6 and 7–9). The 1H NMR spectra suggest intramolecularly coordinated pendant arms in solution for compounds bearing two or three 2-(Me2NCH2)C6H4 groups. Single-crystal X-ray diffraction studies revealed strong N→Te intramolecular interactions in compounds 2, 4, 6 and 7, which result in hypercoordinated triorganotelluronium(IV) cations with different distorted coordination geometries. Further secondary bonding interactions (S⋅⋅⋅Te in 2 and Se⋅⋅⋅Te in 6) lead to cation–anion associations, while H⋅⋅⋅E (E = S, Se) contacts between cations and anions resulted in different supramolecular networks in 2, 4 and 6 and in discrete cation–anion pairs in 7.

New diorganopnicogen(III) compounds of type [CH3OCH2CH2N(CH2C6H4)2]ML (M = Sb, L = ONO2 (3), OSO2CF3 (4); M = Bi, L = ONO2 (5), OSO2CF3 (6), OSO2C6H4(CHCH2)-4 (7) based on a heterocyclic butterfly-like tetrahydro-dibenzo[c,f][1,5]azastibocine/azabismocine skeleton were prepared by ligand exchange reactions between [CH3OCH2CH2N(CH2C6H4)2]MX (M = Sb, X = Cl (1); M = Bi, X = Br (2) and the appropriate silver salt. The new compounds 1 and 3–7 were structurally characterized by NMR and IR spectroscopy. For compounds 5, 7‧CHCl3 and the hydrolysis product [{CH3OCH2CH2N(CH2C6H4)2}BiOH2][CF3SO3] (6h) the crystal and molecular structures were determined by single-crystal X-ray diffraction. Strong transannular N→Bi interactions accompanied by strong MeO→Bi intramolecular interactions result in hypercoordinated species: 14‒Bi‒6 in 5, with a unisobidentate ONO2 ligand, and 12‒Bi‒5 in the cation of 6h and in 7‧CHCl3, with a monodentate OSO2C6H4(CHCH2)-4 ligand. The molecules are associated in dimeric units by Bi⋯π arene interactions (approx. 3.50 A). Weak H⋯O (in 5), H⋯π arene (in 7‧CHCl3), H⋯π arene, H⋯O and H⋯F (in 6h) intermolecular interactions contribute to supramolecular networks in all three compounds.

Group 12 metal complexes of type [MCl2(PPhxR3−x)] [R = C6H4(CH2NMe2)-2, M = Zn, x = 0 (1), 1 (2), 2 (3), M = Cd, x = 0 (4), 1 (5), 2 (6), M = Hg, x = 1 (7), 2 (8)] were prepared by complexation reactions between the metal dichlorides MCl2 (M = Zn, Cd, Hg) and the corresponding triarylphosphane in a 1:1 molar ratio. The solution behaviour of the metal complexes 1 – 8 was investigated by 1H and 31P NMR spectroscopy. The molecular structures of the metal complexes 3, 5, 6·CH2Cl2, 7 and 8 were determined by single-crystal X-ray diffraction. In all complexes the phosphane ligand acts as a P,N monometallic biconnective moiety towards the metal centre. In 6·CH2Cl2 dimeric units are formed through Cd∙∙∙Cl secondary interactions. In all complexes weak Cl∙∙∙H contacts result in supramolecular assemblies with different degrees of association.

This chapter emphasizes aspects related to the role of organochalcogen (Se, Te) compounds with single E‒O and/or double E=O (E=Se, Te) bonds in organic synthesis, as reagents, intermediates, or catalysts, and it gives a larger extent mainly to data reported in the field during the last ten years. For each of these two heavier chalcogens the material is structured according to the oxidation state of the chalcogen and, for the same oxidation state, in sections dedicated to a particular type of compounds. Functionalization or cyclization reactions in which the organochalcogen compounds take part as nucleophiles, electrophiles or radicals, employed in various synthetic transformations, are discussed and, where available, the mechanistic aspects are outlined. New chiral species and new strategies were developed during last years in order to increase the yield, the reaction rate and the stereoselectivity in specific organic transformations, i.e. addition, oxidation, elimination, cyclization or rearrangement reactions. A notably attention was devoted to easily accessible and environmental friendly catalysts, re-usable and “green” solvents, as well as waste-free procedures.

Bis(2-acetylphenyl)dichalcogenides of type [2-(O=CMe)C6H4]2E2 (E=S, Se, Te) were prepared by the hydrolysis of [2-{(CH2O)2C(CH3)}C6H4]2E2. In their reaction with benzylamine these species yield an air-sensitive condensation product, which undergoes a fast, unexpected oxidative intramolecular cyclization. This process proved to be a very convenient way to prepare 3-amino substituted benzo[b]chalcogenophenes. By contrast, the reaction between [2-(O=CMe)C6H4]TeCl and benzylamine resulted in the condensation product [2-(C6H4CH2N=CMe)C6H4]TeCl.

Tri- and diorganotin(IV) pseudohalides of type [2-(Me2NCH2)C6H4]R2Sn(NCE) [E = S, R = Me (1); E = Se, R = Me (2), Ph (3)] and respectively [2-(Me2NCH2)C6H4]RSn(NCE)2 [E = S, R = nBu (4), Ph (5), 2-(Me2NCH2)C6H4 (6); E = Se; R = 2-(Me2NCH2)C6H4 (7)] were obtained by reacting the appropriate organotin(IV) chlorides and alkali metal pseudohalides in stoichiometric amounts. The new species were characterized by multinuclear NMR (1H, 13C, 119Sn and 77Se where appropriate), IR spectroscopy and mass spectrometry. Both the 119Sn NMR and the X-ray diffraction studies evidenced the formation of Sn–NCE bonds in these compounds. For compounds 1–4, 6 and 7 the single-crystal X-ray diffraction studies revealed intramolecular Me2N→Sn interactions and the formation of hypervalent species 10-Sn-5 in compounds 1–3 and 12-Sn-6 in 4, 6 and 7, respectively. Compounds 1–3 are monomeric species, with monodentate isochalcogenocyanato ligands, while in 4 one of the NCE− ligands behave as a bridging moiety, thus resulting in dimeric associations. Short π CHγ-CH2⋯Cg and respectively Cg⋯Cg intermolecular contacts resulted in polymeric chains of dimmers in 4 and 3D supramolecular networks in 6 and 7, respectively. The reactions of [2-(Me2NCH2)C6H4]RSnCl2 and MECN in an 1:1 molar ratio resulted in the formation of a mixture of [2-(Me2NCH2)C6H4]RSnCl2, [2-(Me2NCH2)C6H4]RSn(NCE)2 and [2-(Me2NCH2)C6H4]RSnCl(NCE) [E = S, R = Ph (8), 2-(Me2NCH2)C6H4 (9); E = Se, R = 2-(Me2NCH2)C6H4 (10)].

Heteroleptic zinc and cadmium complexes of the type [{

Heteroleptic zinc and cadmium complexes of the type [{Me2N^E^OR2}M-Nu]n (M = Zn, Cd; E = S, Se; R = CH3, CF3; Nu = N(SiMe3)2, I, Cl; n = 1–2) were prepared by reacting the alcohol proteo-ligands {Me2N^E^OR2}H with [M(N(SiMe3)2)2] (M = Zn, Cd) or [XMN(SiMe3)2] (M = Zn, X = Cl; M = Cd, X = I) in an equimolar ratio. These group 12 metal complexes were characterised in solution by multinuclear NMR spectroscopy and their solid-state structures were determined by X-ray diffractometry. The ligands {Me2N^E^O(CH3)2}− bearing CH3 groups in α position to the alkoxide behave as κ2-O,E-bidentate moieties (E = S, Se) and form centro-symmetric dinuclear O-bridged heteroleptic alkoxo–amido complexes both with zinc and cadmium, with four-coordinate metal centres resting in tetrahedral environments. By contrast, complexes supported by the CF3-substituted {Me2N^E^O(CF3)2}− crystallise as tetrahedral mononuclear species, with tridentate κ3-N,O,E-coordinated ligands. These structural differences resulting from changes in the ligand skeleton and in the electron-donating properties of the alkoxide were also observed in solution. Attempts to prepare congeneric heteroleptic mercury complexes from [Hg(N(SiMe3)2)2] unexpectedly only afforded homoleptic bis(alkoxide)s such as [{Me2N^S^O(CF3)2}2Hg]. Owing to the strong Hg–C bond, treatment of [PhHgN(SiMe3)2] with {Me2N^S^O(CF3)2}H afforded the heteroleptic, T-shaped [{Me2N^S^O(CF3)2}HgPh] mercuric alkoxide upon elimination of hexamethyldisilazane. [{Me2N^S^O(CF3)2}2Hg] and [{Me2N^S^O(CF3)2}HgPh] constitute very rare examples of structurally characterised mercuric alkoxides.

The lead(II) chloride [{N^NiPr}PbCl] (1), where {N^N}− is a bulky, monoanionic, bidentate iminoanilide ligand, was synthesised by salt metathesis between [{N^NiPr}Li] and PbCl2. The complex was characterised by X-ray diffraction crystallography and 207Pb nuclear magnetic resonance (NMR) spectroscopy. It exists in the molecular solid state as a monometallic three-coordinate species, with two independent, similar but not identical molecules per asymmetric unit. The differences between the first coordination sphere of 1 and that of Fulton’s structurally related β-diketiminato complex [{N^NiPr}PbCl] are illustrated. The synthesis of 1 offers a convenient handle in the still underdeveloped organometallic and inorganic chemistry of lead(II), as exemplified by the synthesis of the alkyl complex [{N^NiPr}PbCH(CH3)2] (3). The iodo complex [{N^NiPr}PbI] (2) was also synthesised, but, unlike 1, it showed limited stability in solution.

The reactions between the diorganobismuth(III) bromides [RCH2N(CH2C6H4)2]BiBr [R = C6H5 (1), C6H5CH2 (2)] and appropriate silver salts resulted in new diorganobismuth(III) compounds of the general formula [RCH2N(CH2C6H4)2]BiX [R = C6H5, X = ONO2 (3), OSO2CF3 (4), OSO2C6H4 (CHCH2)-4 (5); R = C6H5CH2, X = ONO2 (6)], based on a butterfly-like tetrahydro-dibenzo[c,f][1,5]azabismocine heterocyclic framework. The new species were structurally characterized in solution by 1H, 13C{H} and 19F{H} NMR and in the solid state by IR spectroscopy and single-crystal X-ray diffraction. The nitrogen atom is intramolecularly coordinated to bismuth, thus resulting in hypercoordinated species of type 12-Bi-5 (3 and 6) and 10-Bi-4 (4 and 5). In addition, compound 4 shows bismuth⋯π arene and compounds 3 and 6 bismuth⋯oxygen intermolecular interactions, thus leading to dimers in the solid state. These compounds were investigated as catalysts for the oxidation of thiophenol to diphenyl disulfide by using air as an oxidizing agent, both in cyclohexane and in an ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide), at temperatures below 100 °C, affording high reaction rates (TON 34.8, with 100% conversion after 5 h) and a total selectivity to the targeted product.

Ligands of type [R2C(OH)CH2](2-Me2NCH2C6H4)E [R = Me, E = S (1), Se (2), Te (3); R = Ph, E = S (4), Se (5)] were obtained in the reactions of (2-Me2NCH2C6H4)ELi and the corresponding R2C(OH)CH2Cl (R = Me, Ph) reagent. The reactions between the ligands 1–3 and 5 with AgOTf (OTf = OSO2CF3), in a 1:1 M ratio, resulted in the silver(I) complexes [AgOTf{E[CH2C(OH)R2](C6H4CH2NMe2-2)}] [R = Me, E = S (6), Se (7), Te (8); R = Ph, E = Se (9)]. The new compounds 1–9 were investigated by solution NMR spectroscopy (1H, 19F, 77Se, 125Te, as appropriate). The ligands 1–5 were investigated also by 13C NMR. The IR spectra and the molar conductivity of the silver(I) complexes suggested a covalent nature of the Ag–OTf bond, while their ESI + MS spectra suggest the formation of dimeric species. Single crystal X-ray diffraction studies revealed a monomeric structure with intramolecular N⋯H–O hydrogen bonding for compound 5, while for the complex 6 dimeric associations formed by bridging ligands were found.

Several copper(I) complexes of type [CuXPPhn(C6H4CH2NMe2-2)3−n] [X = Cl, n = 1 (2), 2 (3); X = I, n = 0 (4), 1 (5), 2 (6)] were prepared by reacting CuX with the appropriate triarylphosphane in a 1:1 molar ratio. The ionic species [Cu(MeCN)2PPh2{C6H4CH2N(CH2CH2)2O-2}]+PF6− (7) was obtained in the reaction between [Cu(MeCN)4]PF6 and PPh2{C6H4CH2N(CH2CH2)2O-2} (1). All compounds were characterized by NMR spectroscopy (1H and 31P) and mass spectrometry. For compound 7 the 19F NMR spectrum was also recorded. Single-crystal X-ray diffraction studies put in evidence a P,N monometallic biconnective coordination behavior of the ligand in compounds 3, 6·0.5CH2Cl2 and 7·CH2Cl2, while in compound 4 a P,N,N monometallic triconnective behavior was observed. In species 2 the unit cell contains two independent molecules; in one of them the PN2 ligand behaves P,N,N-monometallic triconnective, while in the other as a P,N-monometallic biconnective moiety. The N→Cu intramolecular coordination induces planar chirality to the metal center and, as a consequence, the crystal contains both R and S isomers.

New organoselenium( II )halidesofthetype[RSe] + X − [R = 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 ;X=Cl( 2 ), Br ( 3 ), I ( 4 )] were prepared by cleavage of the Se – Se bond in R 2 Se 2 ( 1 )withSO 2 Cl 2 followed by halogen exchange when organo- selenium chloride was treated with NaBr or KI. The reaction between 2 and R ’ 2 MCl n resulted in new ionic [RSe] + [R ’ 2 MCl n +1 ] − [R ’ =2-(Me 2 NCH 2 )C 6 H 4 , n =1,M=Sb( 5 ), Bi ( 6 ); R ’ =Ph,M=Sb, n =1( 7 )or n =3( 8 )] species. All new compounds were investigated in solution by multinuclear NMR spectroscopy ( 1 H, 13 C, 77 Se, 2D experiments) and mass spectrometry. The ionic nature of 2 and the antimonates species was con fi rmed by conductivity studies. The molecular structures of [{2,6-(Me 2 NCH 2 ) 2 C 6 H 3 }Se] + Cl − · n H 2 O( 2 ·H 2 Oand 2 ·2H 2 O) and [{2,6-(Me 2 NCH 2 ) 2 C 6 H 3 }Se] + [Ph 2 SbCl 4 ] − ( 8 ), respectively, were established by single-crystal X-ray di ff raction, pointing out that the ionic nature of the se compounds is also preserved in the solid state, with both nitrogen atoms strongly trans coordinated to the selenium atom of the cation. Theoretical calculations carried out at the DFT level were exploite d to investigate the nature of the bonding in compounds 2 – 4 and the free cation [RSe] + ( 2a ). A topological analysis based on the theory of Atoms-In-Molecules (AIM) and Electron Localization Function (ELF) jointly to a Natural Bond Orbital (NBO) approach was used to shed light on the e ff ect of the nature of the halogen specie s X on the bonding within the 3c-4e N – Se – Nmoiety

Several families of heteroleptic tetrelenes of general formulae M(E^R(NMe2))[N(SiMe3)2] and M(O^E^R(NMe2))[N(SiMe3)2] (where E = S, Se; M = Ge, Sn, Pb; R(NMe2) = 2-(Me2NCH2)C6H4] supported by organochalcogenolato ligands have been prepared and fully characterised. The coordination chemistry of these ligands containing both hard (N, O) and soft (S, Se) atoms onto metals of varying size, polarisability, electropositivity and electrostatic surface potential has been explored. In the molecular solid-state, the complexes M(E^R(NMe2))[N(SiMe3)2] are monomeric, although an occurrence of weak PbSe intermolecular interactions yielding a bimolecular species has been identified in the case of the plumbylene Pb[SeC6H4(CH2NMe2)-2][N(SiMe3)2]. On the other hand, all complexes M(O^E^R(NMe2))[N(SiMe3)2] form centro-symmetric bimetallic dimers with O-bridging atoms. Multinuclear ((29)Si, (77)Se, (119)Sn, (207)Pb) NMR spectroscopy and crystallographic studies reveal that the metal preferably remains 3-coordinated in all these heteroleptic complexes with absence of coordination of N and S/Se atoms, unless severe depletion of electronic density onto the metal is enforced. Coordination of these heteroelements can thus be achieved either through replacement of α-CH3 substituents (as in the ligand 2-(Me2NCH2)C6H4SeCH2C(Me)2O(-)) by electron-withdrawing α-CF3 moieties (as in the ligand 2-(Me2NCH2)C6H4SeCH2C(CF3)2O(-)), or else with recourse to the use of a cationizing agent leading to the formation of the ion pair [{2-(Me2NCH2)C6H4SeCH2C(Me)2O}Pb](+)·[H2N{B(C6F5)3}2](-) where the cationic metal complex is associated to a weakly-coordinating anion. The data collated herein provide compelling evidence that the coordination chemistry of divalent tetrel elements with ligands featuring both hard and soft donors cannot be reliably anticipated by sole use of general concepts such as the HSAB theory. The related metal complexes containing the rigid 8-(NMe2)naphthalen-1-yl group are also discussed.

The reaction between the organopnicogen(III) chlorides R2MCl and RMCl2 [M = Sb, Bi; R = 2-(Me2NCH2)C6H4] and alkali metal pseudohalides in a 1:1 and a 1:2 molar ratio, respectively, resulted in the formation of hypervalent species of type R2MX (M = Sb, X = NCO (1), NCS (2) and SeCN (3), M = Bi, X = NCO (4) and SeCN (5), and RMX2 (M = Sb, X = NCO (6) and NCS (7), M = Bi, X = NCO (8), NCS (9) and SeCN (10). The new species were characterized by multinuclear NMR (1H, 13C, 77Se where appropriate), IR spectroscopy and mass spectrometry. The molecular structures of compounds 2–5 and 7 were determined by single-crystal X-ray diffraction. In all five compounds the nitrogen atoms in the pendant arms are involved in intramolecular coordination to metal, thus resulting in a distorted square pyramidal coordination geometry (12-M-5 hypervalent species) in case of 2–5 and a distorted trigonal pyramidal coordination geometry in case of 7 (10-Sb-4 hypervalent species). The intramolecular N → M coordination determines a chiral pattern of the investigated compounds. Bi⋯Phcentroid intermolecular interactions led to dimers in case of compound 4. In all species weak CH⋯Phcentroid intermolecular contacts led to polymeric associations, e.g. polymeric chains in case of compounds 2, 3, 5 and 7 and a 2D layer structure built by chains of dimers in case of compound 4. DFT calculations and FTIR data allowed us to assign the coordination pattern of the pseudohalide ligand in the other species.

New enantiopure ligands containing two (–)-5,6-pinenebipyridine units connected by a bridge situated in position 6′ of the bipyridines have been prepared. The chemically addressable groups of the bridging (hydroxyl or keto) can be covalently bound to various supports in order to heterogenize the ligand.

Hypervalent diorganoselenium(II) compounds of type 1-{2-[(2-(3,5-dimethyl-4,5-dihydro-1H-pyrazol-1-yl)ethyl)selanyl]phenyl}-N,N-dialkylmethanamine, [2-(R2NCH2)C6H4][(3,5-dmpz)CH2CH2]Se, [R = Me (1), Et (2), dmpz = dimethylpyrazole] were obtained by reacting 1-(2-bromoethyl)-3,5-dimethyl-1H-pyrazole [(3,5-dmpz)CH2CH2Br] with alkali metal aryl selenolates of type [2-(R2NCH2)C6H4]SeM (R = Me, M = Na; R = Et, M = Li) in a 1:1 molar ratio. The coordination ability of species 1, as well as that of bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]selane, [(3,5-dmpz)CH2CH2]2Se (3) toward several late transition metals (Pd, Au, Ag) was investigated by reacting the neutral ligands 1 and 3 with PdCl2, AuCl(tht) and AgOTf in a 1:1 molar ratio. The neutral ligands 1–3, as well as the gold(I), silver(I) and palladium(II) adducts [2-(Me2NCH2)C6H4][(3,5-dmpz)CH2CH2)]SeAuCl (4), [(3,5-dmpz)CH2CH2)]2SeAuCl (5), [2-(Me2NCH2)C6H4][(3,5-dmpz)CH2CH2)]SeAgOTf (6), [(3,5-dmpz)CH2CH2)]2SeAgOTf (7) and [(3,5-dmpz)CH2CH2)]2SePdCl2 (8) were characterized by NMR spectroscopy (1H, 13C, 77Se) and mass spectrometry. The reaction between 1 and PdCl2 in a 1:1 molar ratio resulted in the formation of a complex reaction mixture of which the species [2-(Me2NCH2)C6H4SePdCl]2 (9) and 1-(2-chloroethyl)-3,5-dimethyl-1H-pyrazole [(3,5-dmpz)CH2CH2Cl] were unambiguously identified. Single crystal X-ray diffraction studies revealed a monomeric structure with a distorted T-shaped coordination geometry of type (C,N)SeC for the neutral ligand 1 and supramolecular associations based on dimeric units in case of species 9 and 9·0.5CH2Cl2·0.5THF.

Several organophosphorus acids of type [{XP(OEt)2}(O2SR)]NH [X = O, R = Me (1), Ph (2), C6H4CH3-4 (3); X = S, R = C6H4Cl-4 (4)] were obtained by a method based on the reaction between (EtO)2P(X)NHLi and the corresponding organosulfonyl chloride. They were subsequently deprotonated with KOBut. Salt metathesis reactions between PdCl2 and the corresponding potassium salts K[{XP(OEt)2}(O2SR)N] [X = O, R = Me (5), Ph (6), C6H4CH3-4 (7); X = S, R = C6H4Cl-4 (8)] in a 1:2 molar ratio resulted in palladium(II) complexes of type Pd[{XP(OEt)2}(O2SR)N]2 [X = O, R = Me (9), Ph (10), C6H4CH3-4 (11); X = S, R = C6H4Cl-4 (12)]. In a similar way was obtained the palladium(II) complex Pd[(SPPh2)(O2SPh)N]2 (13), using the appropriate reagents. All compounds were characterized by multinuclear NMR (1H, 13C, 31P) and infrared spectroscopy. The potassium salts and the palladium complexes were investigated also by mass spectrometry. Single-crystal X-ray diffraction studies revealed a layered supramolecular assembly in case of acid 1, a monomeric structure for compound 4, while in case of compound 2 dimeric associations are formed in the solid state by NH⋯OP hydrogen bonding. A trans-S,N-coordination pattern of the organophosphorus ligand was found in the palladium complex 12. Moreover, short Cl⋯H contacts result in a polymeric [Pd[{SP(OEt)2}(O2SC6H4Cl-4)N]2]n chain.

The new organophosphorus proligand (OPPh2)(O2SMe)NR (R = C6H3Pri 2–2,6) (3) was prepared as a white crystalline solid by reacting the lithiated compound Li[Ph2P(O)NR] with MeSO2Cl in a 1:1 molar ratio. The precursor Ph2P(O)NHR (1), as well as its thio analogue Ph2P(S)NHR (2), were obtained in the reaction between the lithiated amine RNHLi and the corresponding organophosphorus chloride. All compounds were characterized by multinuclear (1H, 13C, and 31P) NMR spectroscopy. The molecular structures of 1–3 were established by single-crystal X-ray diffraction. A zigzag polymeric chain is formed in the crystals of 1 and 2 by hydrogen N–H···X (X = O, S) bonding, while the crystal of 3 contains discrete monomeric units with a syn–syn conformation of the O˭P(C)2–N–S(C)(˭O)2 skeleton. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

The reaction between gold(I) and silver(I) starting materials with anionic organophosphorus ligands of type [(SPPh2)(O2SR)N]- resulted in new group 11 complexes of the type [Au{(SPPh2)(O2SR)N}(tht)] (tht = tetrahydrothiophene), [Au{(SPPh2)(O2SR)N}(PPh3)], PPN[Au{(SPPh2)(O2SR)N}2] [PPN = bis(triphenylphosphine)iminium], [Ag{(SPPh2)(O2SR)N}] and [Ag{(SPPh2)(O2SR)N}(PPh3)] (R = Me, Ph, C6H4CH3-4). The new derivatives were structurally characterized by 1H and 31P NMR spectroscopy, as well as infrared and mass spectrometry. Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(I) species [Au{(SPPh2)(O2SMe)N}(PPh3)] (4) and [Au{(SPPh2)(O2SC6H4Me-4)N}(PPh3)] (6), while a dimeric association was found for the silver(I) compound [Ag{(SPPh2)(O2SPh)N}(PPh3)]2·2CH2Cl2 (14·2CH2Cl2). The organophosphorus(V) ligand units have different coordination patterns, i.e. S-monometallic monoconnective in 4, S,O-monometallic biconnective in 6 and S,S,O-bimetallic triconnective in 14, respectively. © 2009 Elsevier B.V. All rights reserved., Financial support from the Ministry of Education and Research of Romania (CNCSIS, Research Project No. 1456/2007-2008) is greatly appreciated. A.P. is grateful for a research fellowship awarded by the ‘‘Babes-Bolyai” University, Cluj-Napoca, Romania.

Arylselenium(II) derivatives of dithiophosphorus ligands of type ArSeSP(S)R2 [Ar = Ph, R = Ph (1), OPri (2); 2-[MeN(CH2CH2)2NCH2]C6H4, R = Ph (3), OPri (4); 2-[O(CH2CH2)2NCH2]C6H4, R = OPri (6)] were prepared by redistribution reactions between Ar2Se2 and [R2P(S)S]2. The derivative [2-{O(CH2CH2)2NCH2}C6H4]SeSP(S)Ph2 (5) was obtained by the salt metathesis reaction between [2-{O(CH2CH2)2NCH2}C6H4]SeCl and NH4S2PPh2. The compounds were investigated by multinuclear (1H, 13C, 31P, 77Se) NMR and infrared spectroscopy. The crystal and molecular structures of 1, 3, 4 and 6 were determined by single-crystal X-ray diffraction. In compounds 3, 4 and 6 the N(1) atom is intramolecularly coordinated to the selenium center, resulting in a T-shaped geometry (hypervalent 10-Se-3 species). The dithiophosphorus ligands act as anisobidentate in 1 and monodentate in 3, 4 and 6. Supramolecular architectures based on intermolecular S⋯H and N⋯H contacts between molecular units are formed in the hypervalent derivatives 3 and 4, while in the compounds 1 and 6 the molecules are associated into polymeric chains through either Se⋯S or O⋯H contacts, with no further inter-chain interactions.