Selenium Ligands Research Articles

Synthesis and spectroscopic studies of palladium and platinum complexes of methylene-backboned dithio-, diseleno- and ditelluro-ether ligands, RECH2ER (R = Me or Ph; E = S, Se or Te)

The complexes [ML2Cl2](M = Pd or Pt; L = PhSCH2SPh, MeSCH2SMe, PhSeCH2SePh or MeSeCH2SeMe), which are square planar with monodentate sulfur or selenium ligands, have been prepared. In the solid state, on the basis of IR and Raman data, the palladium complexes are trans and the platinum cis, whilst in solution multinuclear NMR spectroscopy (1H, 195Pt-{1H}, and 77Se-{1H}) reveal that both cis and trans isomers and meso and DLenantiomers are present, the isomer populations varying with L and M in a systematic way. The complexes [ML2Cl2] are stable in solution for L = PhSCH2SPh, but the other complexes lose L to precipitate polymeric [(MLCl2)n] complexes. The ditelluroethers, MeTeCH2TeMe and PhTeCH2TePh, form only the latter type of complex. The crystal structure of trans-[Pd(PhSCH2SPh)2Cl2] has been determined and contains a trans square-planar palladium atom with one co-ordinated and one free sulfur atom associated with each dithioether ligand [Pd–Cl 2.292(1) and Pd–S 2.329(1)A].

Gold complexes with selenium ligands. Part 7. Synthesis and crystal structures of oligonuclear gold(I)-selenolate complexes

Cationic and neutral Oligonuclear organophosphinegold(I) complexes with organic selenolate ligands SeR [R = Ph, CH2Ph, C6H4NH2– 4, C6H4Cl – 4 or C10H7, (naphthyl)] have been prepared and characterized by spectroscopic methods. Additionally, X-ray crystal structure analyses have been performed for [(AuPPh3)2(SeCH2Ph)]SbF6, the mixed cationic-neutral complex [(AuPPh3)2(SeC10H7)]SbF6·[Au(PPh3)(SeC10H7)] and for [(AuSePh)2(dppe)][dppe = 1,2-bis(diphenylphosphino)ethane]. The Au–Se bond lengths lie in the range 2.41 2 A(neutral complexes) to 2.465 A(cationic complexes). All crystal structures show distortions of the co-ordination geometry at selenium and reveal short Au ⋯ Au contacts. The molecular structure of [(AuPPh3)2(SeCH2Ph)]SbF6 represents the first example of a cationic alkylselenolate-gold complex. The complex [(AuPPh3)2(SeC10H7)]SbF6·[Au(PPh3)(SeC10H7)] exhibits an unexpected structure: the cationic and the corresponding neutral selenolate complex are linked by intermolecular Au ⋯ Au interactions, thus forming a trinuclear selenolate complex. The complex [(AuSePh)2(dppe)] is the first structurally characterized gold-organoselenolate complex with a bridging diphosphine ligand.

Trinuclear and tetranuclear iron/ruthenium carbonyl clusters stabilized by bridging selenium ligands

At room temperature, Fe 2(CO) 6(μ-Se 2) reacts with Ru 3(CO) 12 to form Fe 2Ru 3(CO) 17(μ 4-Se)(μ 3-Se), and with Ru(CO) 4(C 2H 2) to form Fe 2Ru(CO) 9(μ 3-Se) 2. The latter reacts with Fe(CO) 5 under visible light irradiation to give Fe 3Ru(CO) 11(μ 4-Se) 2, and with Ru(CO) 4(C 2H 4) to form Fe 2Ru 2(CO) 11(μ 4-Se) 2. Visible light irradiation of a solution containing Fe 3(CO) 9(μ 3-Se) 2 and Fe(CO) 5 yields Fe 4(CO) 11(μ 4-Se) 2. A solution containing Fe 3(CO) 9(μ 3-Se) 2 and Ru(CO) 4(C 2H 4) at room temperature with stirring yielded Fe 3Ru(CO) 11(μ 4-Se) 2.

Application of the hydro(solvento)thermal technique to the synthesis of metal carbonyl chalcogenide clusters. 2. Synthesis and x-ray structures of [[Fe4Te4(CO)10]2(Te2)]2- and [[Fe2Se(CO)6]2(Se2)]2-

The hydrothermal reaction of Fe(CO)[sub 5] with Na[sub 2]Te[sub 2] in the presence of Ph[sub 4]PCl at 110[degrees]C forms (Ph[sub 4]P)[sub 2][[l brace]Fe[sub 4]Te[sub 4](CO)[sub 10][r brace][sub 2](Te[sub 2])] (I) while the reaction of Fe(CO)[sub 5] with Na[sub 2]Se[sub 2] in superheated methanol at 80[degrees]C results in (Ph[sub 4]P)[sub 2][[l brace]Fe[sub 2]Se(CO)[sub 6][r brace][sub 2](Se[sub 2])] (II). The structures of (I) and (II) were determined by X-ray single-crystal analysis. (I) crystallizes in the space group P[bar 1], and (II) in the space group P2[sub 1]/n. The [[l brace]Fe[sub 4]Te[sub 4](CO)[sub 10][r brace][sub 2](Te[sub 2])][sup 2[minus]] anion in (I) forms a ditelluride, Te[sub 2][sup 2[minus]], bridged double cubane-like structure with eight iron atoms in two Fe[sub 4]Te[sub 4] cubes being octahedrally-coordinated by briding tellurium ligands and terminal CO groups. The [[l brace]Fe[sub 2]Se(CO)[sub 6][r brace][sub 2](Se[sub 2])][sup 2[minus]] molecule in (II) adopts a double butterfly' conformation caused by an intramolecular Se-Se linkage between two Fe[sub 2]Se[sub 2](CO)[sub 6] units. All iron atoms in this structure have a distorted octahedral geometry achieved by selenium ligands, CO groups, and a Fe-Fe single bond. The average Fe-Te bond distance is 2.619(4) [Angstrom], and Fe-Se = 2.386(17) [Angstrom]. 30 refs., 4 figs., 5 tabs.

Gold complexes with selenium ligands, I. Preparation and crystal structures of phenylselenolato‐gold(I) complexes

Abstract(Triphenylphosphine)phenylselenolatogold(I), Ph3PAuSePh (1), and the corresponding dppm derivative, [(dppm)(AuSePh)2] (3), are prepared from Me3SiSePh and the appropriate (phosphine)chlorogold(I) complex. The reaction between Ph3PAuCl, Ph2Se2 and AgSbF6 leads to the salt [(Ph3PAu)2SePh]+SbF−6 (2), with a bridging PhSe ligand. X‐ray structure analyses of 1 and 2 confirm the expected linear geometry at gold and reveal short Au‐Au contacts; both compounds may thus be regarded as loose dimers.

ESR spectroscopy of Co2+ impurities in Cd2P2S6 and Cd2P2Se6

The ESR spectra of Co2+ impurities in Cd2P2S6 and Cd2P2Se6 are reported. The Co2+ ion is an S=3/2 ion and substitutes for Cd2+ (S=0) ions in the Cd2P2X6 crystal. The spin Hamiltonian parameters g and A were determined using an effective spin=1/2. For Cd2P2S6, g/sub ///=4.86, A/sub ///=440 MHz, gperpendicular to =4,01 and Aperpendicular to =346 MHz. For Cd2P2Se6, g/sub ///=4.98, A/sub ///=565 MHz, gperpendicular to =3.85 and Aperpendicular to =250 MHz. From the temperature dependence of the linewidth, the zero-field splitting, 2D, for Co2+ doped into Cd2P2S6 is estimated to be 127 cm-1. The individual hyperfine lines of Co2+ doped into Cd2P2Se6 show superhyperfine structure due to 77Se(I=1/2, 7.58% natural abundance). This additional splitting is consistent with some covalent bonding between the Co2+ and its six selenium ligands.

Binuclear vanadium complexes containing sulfur and selenium ligands: The reactions of the half-sandwich compounds CpV(CO) 4 and Cp ★V(CO) 4 with dichalcogenides E 2R 2 (E = S, Se; R = Me, Ph). The X-ray crystallographic structures of Cp ★2V 2(CO) 4(μ-SR) 2 (R = Me, Ph; Cp ★ = C 5Me 5)

Both the photo-induced reaction of CpV(CO) 4 ( 1) and Cp ★V(CO) 4 ( 1 ★) (Cp = C 5H 5, Cp ★ = C 5Me 5) with diorganochalcogenides, E 2R 2 (E = S, Se; R = Me, Ph) at room temperature in THF solution and the thermal reaction of the kinetically labile derivatives CpV(CO) 3(SMe 2) ( 7) and Cp ★V(CO) 3(SMe 2) ( 7 ★) with E 2R 2 in solution lead to binuclear, diamagnetic complexes Cp 2- and Cp 2 ★-V 2(CO) 4(μ-ER) 2 ( 8, R = Me and 9, R = Ph). In the presence of excess E 2R 2, further decarbonylation takes place to give paramagnetic Cp 2- and Cp 2 ★-V 2(μ-ER) 4 ( 10, R = Me and 11, R = Ph). With H 2S, both 1 ★ and 7 ★ can be converted into a labile intermediate Cp ★ 2V 2(CO) 4(μ-S) 2 ( 12 ★) which tends to lose the CO ligands. No carbonyl-containing intermediates were observed in the reactions of 1 ★ and 7 ★ with excess sulfur or selenium to give Cp ★ 2V 2E 5 (E = S ( 2a ★) and Se ( 2b ★)) and Cp ★ 2V 2E 4 (E = S, 3a ★ and Se, 3b ★), respectively. The carbonylvanadium complexes were characterized by their 1H, 13C and 51V NMR spectra. X-Ray crystallographic structure analyses carried out for Cp ★ 2V 2(CO) 4(μ-SMe) 2 ( 8a ★) and Cp ★ 2V 2(CO) 4(μ-SPh) 2 ( 9a ★) revealed a bent V 2(μ-SR) 2 core. The Cp ★ ligands are arranged cis to each other, and the organo substituents occupy the exo/ exo positions. The vanadium-vanadium distance is 3.083(1) Å in 8a ★ and 3.070(1) Å in 9a ★.

Cobalt(III) complexes of neutral selenium and tellurium donor ligands: synthesis and nuclear magnetic resonance studies

The first examples of diseleno- and ditelluro-ether complexes of cobalt(III), [Co(MeSeCH2CH2SeMe)2X2]BPh4(X = Cl, Br, or I) and [Co{o-C6H4(TeMe)2}2X2]BPh4(X = Br or I), have been prepared by air oxidation of mixtures of anhydrous CoX2, ligand, and NaBPh4 in nitromethane. The complexes have been characterised by u.v.–visible and multinuclear n.m.r. (59Co, 77Se-{1H}, and 125Te-{1H}) spectroscopy. The iodo complexes are trans isomers, but both cis and trans forms are present with the other halides.

Selenium‐77 NMR of coordination compounds with unsaturated selenium ligands and/or selenium (II) central ions

Abstract77Se NMR spectra of coordination compounds containing unsaturated dithio, thioseleno or diseleno ligands are reported. NiII, ZnII, SeII and TeII were used as central ions. The shielding of the Se donor atoms of the same ligands depends on the central ion, following the series SeII < ZnII < TeII < NiII. The greater is the concentration of selenium atoms in the coordination sphere of identical central ions, the more their signals are shifted to lower field. Comparisons are made between mixed ligand complexes and the corresponding selenium containing parent compounds.The chemical shifts found for the selenium donor atoms in the planar NiII complex {Ni[Se2 CC(CN)2]2}2‐ and the octahedral NiIV complex {Ni[Se2CC(CN)2]3}2‐ differ by 265 ppm. The most downfield shifts of all the investigated compounds were found for donor atoms in 1,2‐diselenolene compounds.

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen: LIII. 125Te- und 77Se-Kernresonanzspektren von Übergangsmetall-komplexen mit “nackten” Tellur- bzw. Selen-Brückenliganden

125Te and 77Se NMR spectroscopy of transition metal complexes containing “naked” tellurium or selenium as a bridging ligand allow the nature of differently bound tellurium or selenium ligands to be determined, as well as the detection of neighbouring hydrido ligands by analyzing the 1H- 125Te( 77Se) couplings. A correla-tion of structural features with chemical shifts of these heteronuclei is not possible owing to the dominant paramagnetic term of the chemical shift.

Co-ordination chemistry of higher oxidation states. Part 18. Bidentate selenoether complexes of the tetravalent platinum metals. Crystal and molecular structure of [Pt{o-C6H4(SeMe)2}Cl4

Osmium(IV) complexes [Os(L–L)Cl4][L–L =e.g. MeSe(CH2)nSeMe (n= 2 or 3) or PhSeCH2CH2SePh] have been prepared from [OsCl6]2– and L–L in 2-methoxyethanol. The same ligands and iridium trichloride produce polymeric [{Ir(L–L)Cl3}n], which are converted into [NMe4][Ir(L–L)Cl4] by excess [NMe4]Cl. These IrIII anions are oxidised by chlorine in CCl4 to red-brown IrIV complexes [Ir(L–L)Cl4]. Halogen (X2) oxidation of [Pt(L–L)X2](X = Cl or Br) produces stable [Pt(L–L)X4]. Complexes trans[M(Me2Se)2Cl4](M = Pt, lr, or Os) are also described. Ruthenium(III) complexes, [AsPh4][Ru(MeSeCH2CH2SeMe)Cl4], [{Ru(MeSeCH2CH2SeMe)Cl3}n], and [{Ru2(MeSeCH2CH2SeMe)3Cl6}n] have been prepared, but these, the RhIII analogues, and [Pd(L–L)Cl2] cannot be oxidised to the tetravalent state. The complexes have been characterised by analysis, i.r., u.v.-visible, 1H, 77Se, and 195Pt n.m.r. spectroscopy and magnetic measurements as appropriate. The 77Se n.m.r. spectra of the [Ir(L–L)Cl4]–, [Pt(L–L)X4], [Pt(Me2Se)X5]– and (prepared in situ)[Pd(Me2Se)X5]–(X = Cl or Br) complexes have been recorded and the values of δ(Se) and 1J(PtSe) discussed. The structure of [Pt{o-C6H4(SeMe)2}Cl4] has been determined by a single-crystal X-ray study and shown to be monoclinic, space group P21/n, with a= 7.926(5), b= 14.545(3), c= 12.307(4)A, β= 99.88(4)°, and z= 4. The structure was refined to R= 0.052 from 1 927 reflections. The structure contains discrete six-co-ordinate Pt and the selenium ligand adopts the meso conformation, Pt–Cl 2.299(4)–2.344(4), Pt–Se 2.432(2) and 2.441(1)A.

Dynamic nuclear magnetic resonance study of Group 6 metal pentacarbonyl complexes. Pyramidal inversion and 1,2-metal shifts in the complexes [M(CO)5(Me2CCH2EECH2)](M = Cr, Mo, or W; E = S or Se)

Mononuclear complexes of the type [M(CO)5(Me2[graphic omitted]H2)], where M = Cr, Mo, or W and E = S or Se, have been prepared. Detailed variable-temperature n.m.r. studies have established the existence of pyramidal inversion about the co-ordinated sulphur or selenium ligand atom and an intramolecular 1,2-metal shift between adjacent chalcogen ligand atoms. The energy barriers associated with both rate processes have been evaluated by dynamic n.m.r. methods. The metal pentacarbonyl complexes of naphtho[l,8-cd]-dithiole and -thiaselenole, [M (CO)5(C10H6EE′)](M = W, E = E′= S; M = Cr, E = S, E′= Se) have also been prepared but no fluxionality was evident.

Novel fluxional rearrangements in binuclear platinum complexes; intermetallic ligand atom switching

The binuclear complexes of the type (±)-[(Me3PtX)2MeE(CHR)nEMe](E = S or Se; X = Cl, Br, or I; R = H or Me; n= 0 or 1) have been shown to exhibit a remarkable series of fluxional phenomena over a range of temperatures; most notable of these is an intermetallic commutation by the two donor atoms of the bidentate sulphur and selenium ligands.

Synthesis of a Δ4‐1,4,2λ5‐Selenazaphospholine, the First Selenophosphorane

A phosphorus atom with three oxygen, one carbon, and one selenium ligand is to be found in the spiro compound (3). This species is the first representative of the selenophosphoranes proposed on several occasions as intermediates.

Complexes of 1,2-bis(isopropylseleno)ethane with chromium, molybdenum, and tungsten carbonyl complexes: a conformational study of a chelated selenium ligand by nuclear magnetic resonance

The preparation and temperature-dependent 1H n.m.r. spectra are reported for new chelated complexes [LM(CO)4][L = 1,2-bis(isopropylseleno)ethane; M = Cr, Mo, or W]. The well resolved n.m.r. spectra are interpreted by considering total inversion of the five-membered chelate-ring system but without invoking true inversion about the ligand donor atoms.

New Fe(III) complexes with sulfur and selenium ligands

FeL 3 complexes, where L = dithiobenzoate C 6H 5-CSS, dithiophenylacetate C 6H 5-CH 2-CSS, or diethyldiselenocarbamate (C 2H 5) 2N-CSe 2, are deeply colored nonelectrolyte inner complexes containing pseudooctahedral [Fe(III)S 6] or [Fe(III)Se 6] chromophores. They all exhibit low-spin magnetic behaviour, with only a small lower-symmetry splitting of the octahedral 2T 2g groundstate, contrarily to the doublet-sextet equilibria known of other [Fe(III)S 6] chromophores like Fe(III) dithiocarbamates. The low-spin behaviour is produced here by the relatively high ligand-field strength of dithiocarboxylates, respectively by the pronounced nephelauxetic effect of selenium ligands, both effects favoring magnetic crossover to the spin-paired d 5 groundstate. Diselenocarbomates dsc forms with iron(III) also a pentacoordinated species Fe dsc 2Cl, whose existence and properties stress the close similarity between dithio- and diselenocarbamato complexes. Mössbauer spectra of iron(II) dithiocarboxylates exhibit rather large quadrupole splitting of the order of 1·8 mm/ sec.

Complexes of 1,2-bis(isopropylseleno)ethane with nickel(II) halides and thiocyanate

The synthesis of the high-spin nickel(II) complexes L2NiX2 is described, where L is the bidentate selenium ligand 1,2-bis(isopropylseleno)ethane and X is Cl or Br. These pale-green complexes are considered to have a six-co-ordinate molecular structure on the basis of conductimetric, magnetic, and spectroscopic evidence. They react with the stoicheiometric amount of potassium thiocyanate to give a bright green, paramagnetic, square-planar isothiocyanato-complex LNi(SCN)2; this, when heated in isopropyl alcohol under reflux affords a yellow complex LNi2(SCN)4 which is probably polymeric. With an excess of potassium thiocyanate the chloro-complex yields the pale blue compound K4Ni(SCN)6,2EtOH.

Complexes of 1,2-bis(isopropylseleno)ethane with palladium(II) and platinum(II) halides

The new bidentate selenium ligand, 1,2-bis(isopropylseleno)ethane, has been prepared, and its diamagnetic 1 : 1 complexes with palladium(II) and platinum(II) chlorides and bromides investigated. These complexes crystallise as monomers from acetone, and dimers from chloroform. On dimerisation, the monomeric bidentate chelated form undergoes rearrangement to give a selenium–ligand bridged system.Infrared, n.m.r. ultraviolet, and visible spectra are reported, and the structures of the complexes considered.