Reaction of bis(bis(trimethylsilyl)amido)mercury(II) with 3,3′-disubstituted binaphthols: Cyclization via an intramolecular electrophilic aromatic substitution reaction

Reaction of the mercury(II) amide Hg[N(SiMe₃)₃]₂ with 3,3′-disubstituted binaphthols (HO)₂C₂₀H₁₀(R)₂-3,3′ (R = SiMe₃, SiMe₂Ph, SiMePh₂, SiPh₃) in a 2:1 stoichiometric ratio furnishes four hexacyclic 1,7-disilylsubstituted derivatives of peri-xanthenoxanthene (PXX). Reaction of these two reagents in a 1:1 ratio results in a mixture of the hexacyclic products as well as the related pentacyclic species which contain one hydroxyl group and only one C-O-C ring fusion. The structures of three of the hexacyclic products (R = SiMe₃, SiMe₂Ph, SiMePh₂) and one of the pentacyclic products (R = SiMe₃) have been obtained. The reaction of Hg[N(SiMe₃)₃]₂ with the 3,3′-disubstituted binaphthols proceeds via an intramolecular electrophilic aromatic substitution reaction and several intermediates in this process have been detected using NMR (¹H and ¹⁹⁹Hg) spectroscopy.     

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L = 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L¹ (5,7-dimethyl-3-(2′,3′,5′-tri-O-benzoyl-β-d-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L² (5,7-dimethyl-3-β-d-ribofuranosyl-s-triazolo[4,3-a]pyrimidine) and L³ (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L¹)](NO₃)₂, [Pd(bpy)(L¹)](NO₃)₂, cis-Pd(L³)₂Cl₂, [Pd₂(L³)₂Cl₄] · H₂O, cis-Pd(L²)₂Cl₂ and [Pt₃(L¹)₂Cl₆] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd₂(L³)₂Cl₄] · H₂O complex was established by X-ray crystallography. The two L³ ligands are found in a head to tail orientation, with a Pd?Pd distance of 3.1254(17) Å. L¹ coordinates to Pd(II) through N8 and N1 forming polymeric structures. L² coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L² does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond.     

Preparation of trihydridostannyl complexes of rhenium stabilised by isocyanide ligands

Mixed-ligand complexes [ReBr(CO)₂(CNR)_nL_3−n] (1-4) [R = 4-CH₃OC₆H₄, 4-CH₃C₆H₄, C(CH₃)₃; L = P(OEt)₃, PPh(OEt)₂; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)₄L] and [ReBr(CO)₃L₂] to react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)₂(CNR)_nL_3−n] with SnCl₂ · 2H₂O yielded the trichlorostannyl derivatives [Re(SnCl₃)(CO)₂(CNR)_nL_3−n] (5-8). Trihydridestannyl complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) were prepared by allowing trichlorostannyl compounds 5-8 to react with NaBH₄ in ethanol. The trimethylstannyl derivative [Re(SnMe₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] (13b) was also prepared by treating [Re(SnCl₃)(CO)₂(CNC₆H₄-4-CH₃){PPh(OEt)₂}₂] with an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH₃)(CO)₂(CNR)_nL_3−n] (9-12) with CO₂ (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)O)₂(μ-OH)}(CO)₂(CNR)_nL_3−n]₂ (14, 15). The complexes were characterised spectroscopically (IR, ¹H, ³¹P, ¹³C, ¹¹⁹Sn NMR) and by X-ray crystal structure determination of [Re(SnH₃)(CO)₂{CNC(CH₃)₃}{PPh(OEt)₂}₂] (10b).     

Synthesis, characterization and in vitro cytotoxicity of the first palladium(II) oxalato complexes involving adenine-based ligands

The first [Pd(Lⁿ)₂(ox)] xH₂O oxalato(ox) complexes involving 2-chloro-N6-(benzyl)-9-isopropyladenine (L¹; complex 1), 2-chloro-N6-(4-methoxybenzyl)-9-isopropyladenine (L²; 2), 2-chloro-N6-(2,3-dimethoxybenzyl)-9-isopropyladenine (L³; 3), 2-chloro-N6-(2,4-dimethoxybenzyl)-9-isopropyladenine (L⁴; 4), and 2-chloro-N6-(4-methylbenzyl)-9-isopropyladenine (L⁵; 5) have been synthesized by the reactions of potassium bis(oxalato)palladate(II) dihydrate, [K₂Pd(ox)₂]·2H₂O, with the mentioned organic compounds (H₂ox = oxalic acid; x = 0 for 1-3 and 5 or 2 for 4). Elemental analyses (C, H, N), FTIR, Raman and NMR (¹H, ¹³C, ¹⁵N) spectroscopies, conductivity measurements and thermal studies (thermogravimetric and differential thermal analyses, TG/DTA) have been used to characterize the prepared complexes. The molecular structures of [Pd(L²)₂(ox)] (2) and [Pd(L⁵)₂(ox)]·L⁵·Me₂CO (5·L⁵·Me₂CO) have been determined by a single crystal X-ray analysis. The geometry of these complexes is slightly distorted square-planar with two appropriate Lⁿ (n = 2 or 5) molecules mutually arranged in the head-to-head (2) or head-to-tail (5) orientation. The Lⁿ ligands are coordinated to the central Pd(II) ion via the N7 atoms. The same conclusions regarding the binding properties of L¹-L⁵ ligands can be made based on multinuclear NMR spectra. In vitro cytotoxicity of the complexes 1-5 has been evaluated against human chronic myelogenous leukaemia (K562) and human breast adenocarcinoma (MCF7) cancer cell lines. Significant cytotoxicity has been determined for the complexes 3 (IC₅₀ = 6.2 μM) and 5 (IC₅₀ = 6.8 μM) on the MCF7 cell line, which is even better than that found for the well-known and widely-used platinum-bearing antineoplastic drugs, i.e. oxaliplatin and cisplatin.     

Reactions of phosphine-nitrile ligands: the formation of phosphine-amine and phosphine-imidate complexes of tungsten carbonyl from 3(diphenylphosphino)propionitrile and 3(diphenylphosphino)2-methylpropionitrile

Reactions of W(CO)₆ and NaBH₄ with the phosphine-nitrile ligands Ph₂PCH₂CH₂CN or Ph₂PCH₂CH(CH₃)CN in hot ethanol or propanol for limited reaction times provide mixtures of the corresponding phosphine-imidate and phosphine-amine complexes of the stoichiometry (CO)₄WL. Longer reaction times provide, in high yield, only the phosphine-amine complexes. Proton-decoupled carbon-13 NMR data from (CO)₄W[Ph₂PCH₂CH(CH₃)CH₂NH₂] are consistent with a locked, six-membered chelate ring in which the methyl group occupies an equatorial position. The NH and NH₂ donor groups in the W(CO)₄L complexes are displaced upon reaction with PhP(CH₃)₂ providing mixtures of cis and trans (CO)₄WLL′ complexes.     

Lanthanide complexes of a cross-bridged cyclam ligand: Isolation and structural characterization of unusual trinuclear μ3-imido Yb(III) cluster cations and a mixed valence Yb(II/III) salt containing an Yb(II) anion

The reaction of the cross-bridged cyclam ligand H₂CBC with divalent ytterbium precursors, Yb[N(SiMe₃)₂]₂[L]₂ (L = THF or Et₂O) or Yb(C₅Me₅)₂(OEt₂) afforded polymeric [Yb(CBC)]_n (1), as the primary product. In addition, the Yb[N(SiMe₃)₂]₂[L]₂ reactions also afforded a small amount of an unusual mixed valence salt containing a trinuclear Yb(III) cluster cation featuring a triply bridging NH group and a mononuclear Yb(II) anion, {[Yb(CBC)]₃[μ³-NH]}⁺ {Yb[N(SiMe₃)₂]₃}⁻ (2). A related cluster containing an iodide counterion, {[Yb(CBC)]₃[μ³-NH]}⁺ I⁻ (3), was also isolated in one case. The structures of salts 2 and 3 were determined by X-ray crystallography. Reaction of [Yb(CBC)]_n with p-tolyldisulfide, (C₆H₄MeS)₂, produced burgundy crystals of [Yb(CBC)(S-p-C₆H₄Me)]_n (4). The ¹H NMR spectra of 2 suggests that the trinuclear cation remains intact in THF-d₈ solution.     

3,5-diacetyl-1,2,4-triazol bis(4N-substituted thiosemicarbazone) palladium(II) complexes: synthesis, structure, antiproliferative activity and low toxicity on normal kidney cells

Treatment of ⁴N-monosubstituted bis(thiosemicarbazone) ligands of 3,5-diacetyl-1,2,4-triazol series with lithium tetrachloridopalladate gave the dinuclear complexes of general formula [Pd(μ-H₃L^1-5)]₂, but using dichloridobistriphenylphosphinepalladium(II) salt, the first mononuclear bis(thiosemicarbazone)-palladium-triphenylphosphine complexes of the 3,5-diacetyl-1,2,4-triazol series, [Pd(H₃L^1-5)PPh₃], have been obtained. All the compounds have been characterized by elemental analysis and by IR and NMR spectroscopy, and the crystal and molecular structures of dinuclear complexes [Pd(μ-H₃L³)]₂ and [Pd(μ-H₃L⁵)]₂ as well as mononuclear complexes [Pd(H₃L¹)PPh₃], [Pd(H₃L²)PPh₃], [Pd(H₃L³)PPh₃] and [Pd(H₃L⁴)PPh₃] have been determined by X-ray crystallography. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, A2780 and A2780cisR human cancer cell lines. Subsequent toxicity study, on normal renal LLC-PK1 cells, shows that all compounds investigated exhibit very low toxicity on kidney cells with respect to cisplatin.     

Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes has been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn NMR, ESI-MS (electrospray ionization mass spectrometry), IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The structures of four di-n-butyltin(IV) complexes, viz., ⁿBu₂Sn(L³)₂ (3), ⁿBu₂Sn(L⁴)₂ (4), ⁿBu₂Sn(L⁵)₂ (5) and ⁿBu₂Sn(L⁷)₂ · 0.5C₆H₆ (7) (LH = 5-[(E)-2-(aryl)-1-diazenyl)quinolin-8-ol) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom. These complexes retain their solid-state structure in non-coordinating solvent as evidenced by ¹¹⁹Sn and ¹³C NMR spectroscopic results. The in vitro cytotoxicity of di-n-butyltin(IV) complexes (3-8) is reported against seven well characterized human tumour cell lines. The basicity of the two quinolinolato donor N and O atoms of the ligands are discussed in relation to the cytotoxicity data.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

Properties of homo- and heteronuclear mixed biscarbene complexes with conjugated bithiophene units

The syntheses and structures of homo- and heteronuclear biscarbene complexes with bithiophene spacers were investigated. The complexes were synthesized by lithiation of bithiophene followed by metallation using combinations of the metal precursors MnMeCp(CO)₃, W(CO)₆, Mo(CO)₆ and Cr(CO)₆, after which the reaction was quenched with triethyloxonium tetrafluoroborate. This classical Fischer method yielded monocarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₃S], ([ML_n] = Cr(CO)₅1a, W(CO)₅2a or MnMeCp(CO)₂3a), homonuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)ML_n], ([ML_n] = Cr(CO)₅1b, W(CO)₅2b or MnMeCp(CO)₂3b) and heteronuclear biscarbene complexes, [ML_nC(OEt)C₄H₂S-C₄H₂SC(OEt)M′L_n] (1d: [ML_n] = Cr(CO)₅ and [M′L_n] = W(CO)₅; 1e: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Cr(CO)₅; 1f: [ML_n] = Cr(CO)₅ and [M′] = Mo(CO)₅); 2d: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = W(CO)₅; 3c: [ML_n] = MnMeCp(CO)₂ and [M′L_n] = Mo(CO)₅). Electron density calculations with the gaussian03 software package of 1e revealed a polar rod with the negative pole towards the chromium carbene side, whereas the biscarbenes 1d and 1b showed very little polarity. By-products resulting from activation of the carbene moieties in homonuclear biscarbene complexes included (i) ester-type complexes of the form [ML_nC(OEt)C₄H₂S-C₄H₂SC(O)OEt], ([ML_n] = Cr(CO)₅1c or W(CO)₅2c), formed in situ in the reaction of 1b and 2b, (ii) the organic bis-ester compound [EtOC(O)C₄H₂S-C₄H₂SC(O)OEt] 4, where both metal moieties had been substituted by oxygen and (iii) the carbon-carbon coupled dimeric bithienyl compound [C₄H₃S-C₄H₂SC(O)C(O)C₄H₂S-C₄H₃S] 5. By-products obtained from heteronuclear biscarbene reactions contain the former diketo compound (or a derivative) as spacer between two metal carbonyl fragments and have the general formula [ML_nC(OEt)C₄H₂S-C₄H₂SCR-CR′C₄H₂S-C₄H₂SC(OEt)ML_n] (5a: [M] = Cr(CO)₅, R = OH, R′ = OEt; 5b: [M] = W(CO)₅, R = R′ = O; 5c: [M] = Mo(CO)₅, R = R′ = O). Reaction of 1d, 1e and 1f with hex-3-yne resulted in the formation of benzannulated products 6a, 6b and 6c. All novel complexes were fully characterized using various spectroscopic techniques. The crystal structures of 1b, 2a and 5 are reported.     

Group 6 metal carbonyl complexes of 1,5-diselena[5]ferrocenophane: Synthesis, characterization, crystallographic and electrochemical study

The group 6 metal complexes of 1,5-diselena[5]ferrocenophane (L) have been prepared and characterized. The structures of [M(CO)₄L] (M = Cr, Mo) show that L adopts the unusual meso-2 conformation. E_1/2 of the 1,1′-ferrocenylene group in three complexes is much more positive than that of the “free” ligand L due to the electron donation from L to the M(CO)₄ fragment.     

Synthesis of fac-[Os(CO)3(L)Me2] (L = THF or MeCN) and some reactions with PPh3 and trityl salts

The reaction of cis-[Os(CO)₄Me₂] with Me₃NO in the THF or MeCN yields the complexes fac-[Os(CO)₃(L)Me₂] (where L = THF or MeCN). Whereas the THF complex is unstable and only characterised spectroscopically, fac-[Os(CO)₃(MeCN)Me₂] has been isolated as a white solid and fully characterized by both analytical and spectroscopic methods. These complexes fac-[Os(CO)₃(L)Me₂] are shown to be useful intermediates. Thus, reaction with PPh₃ gives fac-[Os(CO)₃(PPh₃)Me₂] in good yield.Reactions of fac-[Os(CO)₃(L)Me₂] (L = CO or MeCN) with CPh₃PF₆ or B(C₆F₅)₃ have been investigated. Whereas cis-[Os(CO)₄Me₂] showed no reaction with either CPh₃PF₆ or B(C₆F₅)₃, the reaction of fac-[Os(CO)₃(MeCN)Me₂] with CPh₃PF₆ in CH₂Cl₂ occurred over 16 h at room temperature to give an unstable cationic product and CPh₃Me. The reaction was monitored by both IR and NMR spectroscopies. When this reaction of fac-[Os(CO)₃(MeCN)Me₂] was carried out in the presence of a trapping ligand such as MeCN, the stable cationic product [Os(CO)₃(MeCN)₂Me]⁺ could be isolated and identified spectroscopically.     

Synthesis and characterization of the first zinc(II) complexes involving kinetin and its derivatives: X-ray structures of 2-chloro-N6-furfuryl-9-isopropyladenine and [Zn(kinetin)2Cl2]·CH3OH

A series of the first zinc(II) complexes of the general composition [Zn(Lⁿ)₂Cl₂]·xSolv (1-5) involving kinetin [N6-furfuryladenine, L¹, xSolv = CH₃OH, complex 1] and its derivatives, i.e. N6-(5-methylfurfuryl)adenine (L², xSolv = 2H₂O, 2), 2-chloro-N6-furfuryladenine (L³, 3), 2-chloro-N6-(5-methylfurfuryl)adenine (L⁴, 4) and 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵, 5), as N-donor ligands has been synthesized. The complexes have been fully characterized by elemental analyses (C, H, N), FTIR, Raman, ¹H and ¹³C NMR spectroscopy, conductivity measurements, thermogravimetric (TG) and differential thermal (DTA) analyses. Single crystal X-ray analysis determined the molecular structures of 2-chloro-N6-furfuryl-9-isopropyladenine (L⁵) and the complex [Zn(L¹)₂Cl₂]·CH₃OH. The Zn(II) ion is tetrahedrally coordinated by two chlorido ligands and two molecules of the L¹ organic compound. The two ligands L¹ are coordinated to the central Zn(II) ion via the N7 atoms. This conclusion can also be drawn from multinuclear NMR spectroscopic experiments.     

Structural models for [M(CO)3(H2O)3]+ (M=Tc,Re): fully aqueous synthesis of technetium and rhenium tricarbonyl complexes of tripodal oxygen donor ligands

The reaction of [M(H₂O)₃(CO)₃]⁺ (M=Tc, Re) with Na[CpCo[PO(OR)₂]₃] (NaL_OR; R=Me, Et) in water produced the compounds M(CO)₃(L_OR), all of which were yellow solids, in yields varying from 55 to 89%. The two compounds M(CO)₃(L_OEt) were structurally characterized by single crystal X-ray crystallography. In both cases, the ligand L_OEt was bound to the metal center in a tridentate fashion utilizing an {OOO} donor set. The ligands L_OR can be used as models for facially coordinated triaqua groups owing to their position in the spectrochemical series. Therefore, these four compounds, M(CO)₃(L_OR), can be considered structural models for [M(H₂O)₃(CO)₃]⁺. Crystal data for Tc(CO)₃(L_OEt) are as follows: molecular formula C₂₀H₃₅CoO₁₂P₃Tc, MW=717.32, monoclinic, a=11.5661(11) Å, b=18.671(2) Å, c=13.7852(13) Å, β=92.770(2)°, V=2973.5(5) Å³, space group P2₁/n, Z=4, final R₁=0.0669, wR₂=0.1361. Crystal data for Re(CO)₃(L_OEt) are as follows: molecular formula C₂₀H₃₅CoO₁₂P₃Re, MW=805.52, monoclinic, a=11.5113(7) Å, b=18.6022(12) Å, c=13.7397(8) Å, β=92.7580(10)°, V=2938.7(3) Å³, space group P2₁/n, Z=4, final R₁=0.0384, wR₂=0.0760.     

Solution-phase disproportionation equilibria for monosubstituted Pentakis- (arylisocyanide)cobalt(I) complexes by proton-NMR studies

Equilibrium constants, K_dis, for the solvent- dependent, solution-phase disproportionation equilibria of monosubstituted pentakis(arlisocyanide)cobalt(I) complexes: 2[Co(CNR)₄L]⁺?[Co(CNR)₃L₂]⁺ + [Co(CNR)₅]⁺, K_dis = $\text{[Co(CNR)}{}_3\text{L}{}_2\text{][Co(CNR)}{}_5\text{]}\text{[Co(CNR)}{}_4\text{L]}{}^2$ are measured by planimeter-integration of proton- NMR spectra at ambient temperature. The complexes, [Co(CNR)₄L]ClO₄, R = 2,6-Me₂C₆H₃, L = P(C₆H₅)₃, P(C₆H₄Cl-p)₃, P(OC₆H₅)₃, P(OC₆H₄Cl-p)₃; R = o-MeC₆H₄, L = P(C₆H₄Cl-p)₃, P(OC₆H₅)₃, P(OC₆H₄Cl-p)₃; R = 2,4,6-Me₃C₆H₂, L = P(C₆H₅)₃; R = 2,6-Et₂C₆H₃, L = P(C₆H₅)₃; are investigated in the deuterated solvents, CDCl₃, CD₃CN, (CD₃)₂CO, C₅D₅N, CD₃NO₂, and (CD₃)₂SO. Disproportionation seems to occur in all [Co(CNR)₄L]⁺, but NMR study is facilitated by utilizing equivalent alkyl protons (i.e., Me-groups) on the RNC ligands.Correlation of K_dis values with steric-hindrance of the RNC in sets of complexes with the same P-ligand is evident in all solvents: K_dis decreases with increased steric-hindrance in RNC. The K_dis values for complexes with the same RNC and analogous triarylphosphine, triarylphosphite ligands (i.e., PR₃, P(OR)₃, same R) are approximately equal. The K_dis values for complexes of P-ligands with Cl-substituent are significantly larger than K_dis values for complexes with the corresponding unsubstituted P-ligands (e.g., [Co(CNR)₄P(C₆H₄Clp)₃]ClO₄vs. [Co(CNR)₄P(C₆H₅)₃]ClO₄) in (CD₃)₂CO and C₅D₅N solution, but are smaller in CDCl₃ and CD₃CN, and approximately equal in CD₃NO₂ and (CD₃)₂SO. Properties of the solvents are also considered.     

Studies of copper(II) and nickel(II) complexation by bis(1,4,7-triazacyclononane) ligands containing alkene and alkyne bridging groups

The copper(II) and nickel(II) complexes of three new 1,2-bis(1,4,7-triazacyclononane) ligands containing unsaturated four carbon bridging groups is studied by continuous variation UV-Vis spectroscopic and pH potentiometric equilibrium experiments. The cis-butene-2 (L_C) linked ligand may form monomeric MN₆-type complexes while the trans-butene-2 (L_T) and butyne-2 (L_Y) ligands are prevented by their stereochemistry from forming monomeric complexes and form oligomeric complexes. It is determined that the stability of the CuL_C²⁺ complex is not appreciably different from the oligomeric complexes of L_T and L_Y. Single-crystal X-ray structure determinations are made on three square pyramidal Cu₂L⁴⁺ complexes: [Cu₂L_CCl₄] (1), [Cu₂L_YCl₄] (2), and [Cu₂L_T(NO₃)₂(H₂O)₂](NO₃)₂ (3). The structure of [Ni₂(L_C)₂](ClO₄)₄ · 2H₂O (4) is a binuclear dimer that contains two nickel(II) ions sandwiched between two ligands, indicating that bis([9]aneN₃) ligands with four linker atom chains may form either monomeric or oligomeric structures.     

Reactivity of [MO] (M = Tc, Re) core towards 2-mercapto-1,3-azole ligands. Formation of a new organometallic complex of Re(IV) and X-ray crystal structures

Imidazole-2-thiol derivatives H₂L^1-3 (H₂L¹ = 1H-benzoimidazole-2-thiol, H₂L² = 5-methyl-1H-benzoimidazole-2-thiol, and H₂L³ = 1H-imidazole-2-thiol) act as neutral monodentate ligands in a number of technetium and rhenium complexes. Disubstituted M(V) (M = Tc, Re) complexes of the type [AsPh₄]{[MOCl₂(H₂Lⁿ)₂(H₂O)]Cl₂} are formed when [MOCl₄]⁻ react with H₂L^1-3 in 1:2 stoichiometric ratio. Single crystal X-ray structure determinations were carried out on [AsPh₄]{[TcOCl₂(H₂L¹)₂(H₂O)]Cl₂}. The coordination sphere is pseudo-octahedral in which the sulfur atoms of two ligands sit in the equatorial plane and a water molecule is in trans to the TcO multiple bond. All the complexes react with an excess of the corresponding ligand to form tetrasubstituted cationic species {[MO(H₂Lⁿ)₄]Cl₃}. These complexes can be also isolated by reaction of [MOCl₄]⁻ with an excess of ligand. No complex is obtained with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵). Ligand exchange reactions of [ReOCl₃(PPh₃)₂] with HL^4,5 have also been investigated. Treating the oxo-precursor with HL⁴ no product is isolated, while with HL⁵ the chelate oxo-compound [ReOCl₂(L⁵)(PPh₃)] is formed as two isomers. An interesting organometallic complex of Re(IV) [ReCl₃(L^5∗)(PPh₃)₂] is obtained when a slight excess of HL⁵ reacts with [ReOCl₃(PPh₃)₂] in refluxing benzene solution and in air. Geometry about the Re atom is approximately octahedral in which the equatorial plane contains three Cl atoms and the carbon atom of the benzoxazole ligand anion, the apical positions are occupied by two PPh₃. The reaction with O-ethyl S-hydrogen p-tolyl carbonothioimidate HL⁶ which contains the same heteroatoms of HL⁵ does not form an organometallic species, but forms the chelate oxo-Re(V) complex [ReOCl₂(L⁶)(PPh₃)]. The solid-state structure has been authenticated by X-ray crystallography.     

The tungsten-tungsten triple bond. XV. Synthesis,structure and reactivity of 1,2-W2[CH(SiMe3)2]2(NMe2)4: the remarkable inertness of a sterically-encumbered tungsten-amido complex

Addition of 1,2-W₂Cl₂(NMe₂)₄(W≡W) to a toluene slurry of LiCH(SiMe₃)₂(2 equiv) results in the formation of 1,2-W₂[CH(SiMe₃)₂]₂(NMe₂)₄(W≡W) (I) in 79% isolated yield. Compound I has been characterized by ¹H and ¹³C NMR, IR, elemental analysis and single-crystal X-ray diffraction. The molecule exists exclusively in the gauche conformation in solution and in the solid state with WW = 2.320(1) Å. Compound I is very sterically encumbered as evidenced by: (1) large WWC angles, 110°, at the disyl ligand; (2) skewing of the NC₂ planes of the NMe₂ ligands off the WW vector; (3) anomalously large barriers to WNM₂ bond rotation in solution; (4) the inertness of I towards CO₂ and alcohols. However, compound I reacts with acetic anhydride to form 1,2-W₂[CH(SiMe₃)₂]₂(O₂CMe)₄(W≡W) (II) in 31% isolated yield. Compound II has been characterized by ¹H and ¹³C NMR, IR, and elemental analysis. The mechanistic implications of these studies with regard to alcoholysis and CO₂ insertion reactions of other 1,2-W₂R₂(NMe₂)₄ compounds are discussed. Crystal data for 1,2-W₂[CH(SiMe₃)₂]₂(NMe₂)₄ at −140°C: space group P2₁/n, a = 12.555(3), b = 18.699(5), c = 15.214(4) Å, β = 95.24(1)° and Z = 4.     

Bis(phosphine)-Pd(II) and -Pt(II) complexes containing chiral tetrazole-thiolato rings: Synthesis, structures, and reactivity toward some electrophiles

Bis(azido)bis(phosphine)-Pd(II) and -Pt(II) complexes, [M(N₃)₂L₂] {L = PMe₃, PEt₃, PMe₂Ph, dppe = 1,2-bis(diphenylphosphino)ethane}, underwent 1,3-dipolar cycloaddition with organic chiral isothiocyanates (R^∗-NCS: R^∗ = (S)-(+)-1-phenylethyl, (R)-(−)-1-phenylethyl, (±)-1-phenylethyl, (S)-(+)-1-indanyl) to give the corresponding tetrazole-thiolato Pd(II) and Pt(II) complexes, trans-[M{S[CN₄(R^∗)]}₂L₂] or [M{S[CN₄(R^∗)]}₂(dppe)]. Spectroscopic (IR and NMR) and X-ray structural analyses of the products showed that the absolute configuration of the starting organic isothiocyanates is retained throughout the reaction. Further treatments of the isolated tetrazole-thiolato complexes with electrophiles such as HCl or benzoyl chloride produced heterocyclic compounds containing a tetrazole thione or a tetrazolyl sulfide group. In addition, organic tetrazole thiones, [S = {CN₄H(R^∗)}] containing a chiral moiety, were prepared from NaN₃ and R^∗-NCS in the presence of water.     

Photochemical synthesis method of tungsten(II) complexes [WCl2(CO)3PPh3)2] and [WCl2(CO)2(dppe)]

The photochemical oxidation reaction of W(CO)₆ to [W(CO)₄Cl₂]₂ with CCl₄ was applied in the synthesis of [WCl₂(CO)₃(PPh₃)₂] and [WCl₂(CO)₂₋- (dppe)].