Synthesis and reactions of [M(CO)4(Ph2PSiMe3)X] complexes (M = Mn,Re; X = Halogen)

The silylphosphine ligand Ph₂PSiMe₃ reacts readily with a slurry of [Re(CO)₅X] (X  Cl, Br) in polar and in non-polar solvents to yield soluble cis-[Re(CO)₄- (Ph₂PSiMe₃)X] (Ia, X  Cl;Ib, X  Br) via CO substitution. Compound I is readily hydrolyzed by water or silica gel to cis-[Re(CO)₄(Ph₂PH)X]. Compound Ib reacts with [Re(CO)₅Br] to yield [Re₂(CO)₈(μ-PPh₂)- (μ-Br)] (II), and with [Mn(CO)₅Br] to yield [MnRe- (CO)₈(μ-PPh₂)(μ-Br)] (III).The reaction of Ph₂PSiMe₃ with [Mn(CO)₅X] (X=Cl,Br,I) is highly dependent upon reaction conditions.In polar and in non-polar solvents, an excess of ligand gives mainly cis-[Mn(CO)₄(Ph₂PSiMe₃)X] (IVa, X  Cl;IVb, X  Br;IVc, X I). With ligand: [Mn(CO)₅X] reacting ratios in the range 0.5–1.0:1, the products from the three respective halomanganese complexes in THF were: (a) mainly [Mn₂(CO)₈(μ- PPh₂)(μ-Cl) (Va); (b) both [Mn(CO)₄(Ph₂PSiMe₃)Br] and [Mn₂(CO)₈(μ-PPh₂)(μ-Br)] (Vb); and (c) exclusively [Mn(CO)₄(Ph₂PSiMe₃)I]. The compounds IVa-c are stable in solution at ambient temperatures and are readily hydrolyzed by water or methanol to [Mn(CO)₄(Ph₂PH)X]. Compound IVb reacts at room temperature with [Mn(CO)₅Cl] to yield only [Mn₂- (CO)₈(μ-PPh₂)(μ-Br)] (Vb); compound IVc reacts in hot toluene with [Mn(CO)₅Cl] to yield mainly [Mn₂(CO)₈(μ-PPh₂)(μ-I)] (Vc), together with a small amount of the chloro-bridged analog.The dinuclear species II, III and Va-c appear to be formed mainly via an intermolecular elimination of Me₃SiX from the appropriate [M(CO)₄(Ph₂PSiMe₃)X] and metalpentacarbonylhalide (chloride or bromide) complexes.     

Tris(pentachlorophenyl) gold(III) complexes

By reaction of Tl(C₆Cl₅)₂Cl with Au(C₆Cl₅)(tht) (tht = tetrahydrothiophen) or [N(PPh₃)₂] [Au(C₆- Cl₅)Cl] the gold(III) complexes [Au(C₆Cl₅)₃(tht)] or [N(PPh₃)₂][Au(C₆Cl₅)₃Cl] respectively, can be prepared. They are the first tris(pentachlorophenyl)- gold(III) complexes to be reported. The ready displacement of tht by other neutral or anionic ligands leads to the synthesis of Au(C₆Cl₅)₃(Ph₂PCH₂PPh₂) or Q[Au(C₆Cl₅)₃X] (Q=N(PPh₃)₂, PPh₃Me or PPh₂Me₂; X=C₆F₅, SCN, Br or I).     

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4−n] (n=3 and 4) and [Cd2Cl2(SC{O}Me)4]

We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)_nCl_4−n]²⁻ (n=3, 4) and [Cd₂Cl₂(SC{O}Me)₄]²⁻. Complexes of the formula [Ph₄P]₂[M(SC{O}Me)₄] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph₄PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1<2<3 as observed from the SMS angles in the crystal structures. The tendency of monoanionic complexes [Ph₄P][M(SC{O}Me)₃] to react with 1 mole equivalent of Ph₄PCl resulted in complexes of the type [Ph₄P]₂[M(SC{O}Me)₃Cl] (M=Cd(II) (4) or Hg(II) (5)). In the structures of 4 and 5, three sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the metal centers. However, in a 4:2:2 or 2:1:2 molar reaction of Me{O}CS⁻ with CdCl₂ and Ph₄PCl in aqueous medium resulted in a chloro bridged dimer, [Ph₄P]₂[Cd₂(μ-Cl)₂(SC{O}Me)₄] (6) as determined by X-ray crystallography.     

Half-sandwich Ru[9]aneS3 complexes structurally similar to antitumor-active organometallic piano-stool compounds: Preparation, structural characterization and in vitro cytotoxic activity

The preparation, structural characterization, and chemical behavior in aqueous solution of a series of new Ru[9]aneS₃ half-sandwich complexes of the type [Ru([9]aneS₃)Cl(NN)][CF₃SO₃] and [Ru([9]aneS₃)(dmso-S)(NN)][CF₃SO₃]₂ (5–15, NN = substituted bpy or 2 × 1-methylimidazole) are described. The X-ray structures of [Ru([9]aneS₃)Cl(3,3′-H₂dcbpy)][CF₃SO₃] (9) (3,3′-H₂dcbpy = 3,3′-dicarboxy-2,2′-bipyridine), [Ru([9]aneS₃)Cl(4,4′-dmobpy)][CF₃SO₃] (13) (4,4′-dmobpy = 4,4′-dimethoxy-2,2′-bipyridine), and [Ru([9]aneS₃)Cl(1-MeIm)₂][CF₃SO₃] (15) (1-MeIm = 1-methylimidazole) were also determined. The new compounds are structurally similar to anticancer-active organometallic half-sandwich complexes of formula [Ru(η⁶-arene)Cl(NN)][PF₆]. Three chloro compounds (5, 9, 15) were tested in vitro for cytotoxic activity against two human cancer cell lines in comparison with the previously described [Ru([9]aneS₃)Cl(en)][CF₃SO₃] (1, en = ethylenediamine), [Ru([9]aneS₃)Cl(bpy)][CF₃SO₃] (2), and with their common dmso precursor [Ru([9]aneS₃)Cl(dmso-S)₂][CF₃SO₃] (3). Only the ethylenediamine complex 1 showed some antiproliferative activity, ca. one order of magnitude lower than the reference organometallic half-sandwich compound RM175 that contains biphenyl instead of [9]aneS₃. This compound was further tested against a panel of human cancer cell lines (including one resistant to cisplatin).     

Salts of cationic platinum dithiolenes with anionic platinum complexes: structural characterization of [Pt(Me2pipdt)2][Pt(SCN)4] (Me2pipdt = N,N-dimethyl-piperazine-2,3-dithione)

[Pt(Me₂pipdt)₂](BF₄)₂ salts [Me₂pipdt = N,N^′-dimethyl-piperazine-2,3-dithione] bearing cationic dithiolene complexes react with (Bu₄N)₂[Pt(X)₄] (X = SCN, CN) to form [Pt(Me₂pipdt)₂][Pt(SCN)₄ ] (1) and [Pt(Me₂pipdt)₂][Pt(CN)₄] (2) salts by metathesis. Black crystals of 1 have been structurally characterized showing that the two metals lie on inversion centers and exhibit a square planar coordination. The Pt-S bond distances in the anion complex (2.324(2) Å) are longer than in the cation complex (2.280(2) Å) whereas the C-S bond distances are shorter in SCN⁻ (average 1.669 Å) than in Me₂pipdt (average 1.694 Å). The chelating Me₂Pipdt ligand is found disordered in the λ/δ conformations with site occupancies of 50/50, respectively. The cation and anion complexes run parallel to a.     

Phosphorus-31 and cadmium-113 NMR studies of some cadmium(II) complexes containing tricyclohexylphosphine and tributylphosphine

Phosphorus-31 and cadmium-113 NMR spectroscopy has been used to study the interaction between tertiary phosphines (P(c-C₆H₁₁)₃ and PBu₃) and Cd(O₃SCF₃)₂, Cd(ClO₄)₂, Cd(CF₃COO)₂ and Cd(SCN)₂ salts in solution. the NMR data imply the formation in solution of novel 1:1 adducts CdX₂(phos) (X = O₃SCF₃, ClO₄, CF₃COO, phos = P(c-C₆H₁₁)₃, PBu₃) in which there is substantial interaction between the anions and cadmium. Data are also presented for mixed phosphine complexes CdX₂[P(c-C₆H₁₁)₃][PBu₃] (X = O₃SCF₃, ClO₄, NO₃, CF₃COO, CH₃COO, Cl, Br, I, SCN). The two bond coupling constants ²J(P′P) of these mixed phosphine complexes decrease as the coordination ability of the anion increases and cover the narrow range from 95 Hz to 66 Hz.     

Synthesis and characterization of iron and ruthenium complexes bearing P-N ligands based on 8-hydroxyquinoline

The synthesis of bidentate aminophosphine ligands (PN^quin) based on 8-hydroxyquinoline is described. These ligands react with cis-Fe(CO)₄Br₂ to give selectively octahedral complexes of the type cis,cis-Fe(PN^quin)(CO)₂Br₂. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis configuration. The reaction of [RuCp(CH₃CN)₃]PF₆ with PN^quin ligands affords the halfsandwich complexes [RuCp(PN^quin)(CH₃CN)]PF₆ in high isolated yields. Likewise, treatment of [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ with PN^quin in the presence of AgCF₃SO₃ affords halfsandwich complexes of the type [Ru(η⁶-p-cymene)(PN^quin)Cl]CF₃SO₃. All ligands and complexes are characterized by NMR and IR spectroscopy. The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric structures and conformers of Fe(PN^quin-Ph)(CO)₂Br₂ is studied by means of DFT calculations.     

New ruthenium(II) precursors with the tetradentate sulfur macrocycles tetrathiacyclododecane ([12]aneS4) and tetrathiacyclohexadecane ([16]aneS4) for the construction of metal-mediated supramolecular assemblies

The preparation and structural characterization of several new Ru(II) complexes in which four coordination positions are occupied by the sulfur atoms of a macrocycle, either 1,4,7,10-tetrathiacyclododecane ([12]aneS4) or 1,5,9,13-tetrathiacyclohexadecane ([16]aneS4), and the two others by relatively labile ligands (Cl⁻, , H₂O, dmso-S), are described:cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a), cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b), cis-[Ru([16]aneS4)Cl₂] (4), and trans-[Ru([16]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (5).The complexes of the larger [16]aneS4 macrocycle have a flexible coordination geometry, either cis or trans, that makes them unsuited for being used as precursors in metal-driven self-assembly processes.On the contrary, the [12]aneS4 complexes cis-[Ru([12]aneS4)(dmso-S)Cl]Cl (1) and, above all, its chlorido free derivatives cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a) and cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b) are potential precursors of the geometrically stable 90° bis-acceptor fragment cis-[Ru([12]aneS4)]²⁺.Preliminary results of their reactivity towards the linear linker pyrazine (pyz) showed that the nature of the isolated product depends on that of the counter-anion.When treated with pyz 2b afforded the dinuclear complex [{Ru([12]aneS4)(ONO₂)}₂(μ-pyz)](NO₃)₂ (8), while 2a gave the molecular triangle [{cis-Ru([12]aneS4)(μ-pyz)}₃](CF₃SO₃)₆ (9), both in low yields.The X-ray structures of compounds 2a, 2b, 4, 5, [{Ru([12]aneS4)Cl}₂(μ-pyz)]Cl₂ (7), 9, and of the sandwich complex[Ru([12]aneS3-S)₂](CF₃SO₃)₂ (3), in which only three sulfur atoms of each macrocycle are bound to ruthenium, are also described.     

Spectroscopic and reactivity comparison of pentacyanonitrosylruthenate(2-) with pentacyanonitrosylferrate(2-), nitroprusside

Lithium penta(cyano-¹³C)nitrosylruthenate (2-), Li₂[Ru(¹³CN)₅NO], in which the anion is the ruthenium analogue of the nitroprusside ion, has been synthesized at 90% isotopic enrichment, and characterized spectroscopically. Despite the very high level of ¹³C enrichment, no two-bond coupling ²J(¹³C_ax-Ru¹³C_eq) was detected in the high-frequency ¹³C NMR spectrum of Li₂[Ru(¹³CN)₅NO], nor was any such coupling observed in Li₄[Ru(¹³CN)₅(¹⁵NO₂)] although both two-bond couplings to ¹⁵N, ²J(¹³C_ax-Ru¹⁵NO₂) and ²J(¹³C_eqRu¹⁵N) were observed. Li₂[Ru(¹³CN)₅(¹⁴NO)] reacted with excess of Li[¹⁵NO₂] to yield Li₄[Ru(¹³CN)₅(¹⁵NO₂)] only: no Li₂[Ru(¹³CN)₅(¹⁵NO)] was observed. Li₄[Ru(¹³CN)₅(¹⁴NO₂)] however showed no exchange with Li[¹⁵NO₂]. While [Ru(CN)₅NO]²⁻ reacted with both OH⁻ and SH⁻ in reactions similar to those of [Fe(CN)₅NO]²⁻, no reactions were detected between [Ru(CN)₅NO]²⁻ and piperidine, [CH(CN)₂]⁻, [CH(COCH₃)₂]⁻, MeS⁻, or [S₂O₄]²⁻, all of which are known to react readily with [Fe(CN)₅NO]²⁻     

Preparation of planar chiral ferrocenes containing a fluorous alcohol function

Ferrocene reacts with hexafluoroacetone trihydrate in refluxing octane to afford >80% yields of [CpFe(η⁵-C₅H₄C(CF₃)₂OH)] (X-ray), carrying out the reactions at 180 °C gives an additional 5% yield of [Fe(η⁵-C₅H₄C(CF₃)₂OH)₂] (X-ray).The mono alcohol is lithiated with Bu^tOK/BuⁿLi/TMEDA affording partial conversion to mixtures of [CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(X)] and [Fe(η⁵-C₅H₄X)(1,2-η⁵-C₅H₃C(CF₃)₂OH)(X)] (X = SMe, CPh₂OH) upon reaction with Me₂S₂ or OCPh₂.For X = CPh₂OH both structures are crystallographically characterised.Enantiopure [CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(SMe)] can be prepared from (R)-[CpFe(η⁵-C₅H₄S(O)C₆H₄Me)] via [CpFe(1,2-η⁵-C₅H₃S(O)C₆H₄Me)(C(CF₃)₂OH)] (X-ray) or [CpFe(1,2-η⁵-C₅H₃S(O)C₆H₄Me)(SMe)].Related procedures allow the preparation of [CpFe(1,2-η⁵-C₅H₃CPh₂OH)(Y)] (Y = SMe, CHO (X-ray), C(CF₃)₂OH) and[CpFe(1,2-η⁵-C₅H₃C(CF₃)₂OH)(CHO)].     

The first pincer-aryl [M-(NCN)] complexes {M = Pd(II); Pt(II)} with chiral pyridine donors: Synthesis and catalytic activity in C-C bond formation

The first chiral bis(pyridine) N-C(H)-N pincer ligand, (5S,7S)-1,3-bis(6,6-dimethyl-5,6,7,8-tetrahydro-5,7-methanquinolin-2-yl)benzene (HL) has been synthesized and characterized by a thorough ¹H NMR analysis. Reaction of HL with K₂[PtCl₄] in acetic acid gives [Pt(L)Cl] (1), where L acts as a tridentate N-C-N pincer ligand. The analogous palladium(II) derivatives [Pd(L)Cl] (2), and [Pd(L)(OAc)] (3), were first prepared through a transmetalation reaction between Pd(OAc)₂ and the organomercury compound [Hg(L)Cl] (4). The structures of compounds 1 (Pt) and 2 (Pd), as determined by X-ray diffraction, are reported and compared. Compound 2 can also be obtained from Na₂[PdCl₄] and HL in refluxing acetic acid, i.e., under the same conditions used for compound 1. Apparently, this is the first palladium pincer derivative of a 1,3-bis(pyridyl)benzene ligand synthesized by direct C-H activation.The neutral complexes 1-3 are catalysts of modest activity, but devoid of enantioselectivity in the Heck reaction between iodobenzene and methyl acrylate and in the aldol condensation of benzaldehyde with methyl isocyanoacetate.     

Synthesis of (NBu4)2[Pd2(μ-Br)2(C6X5)2Br2] (X=F,Cl), new and more versatile precursors of pentahalophenyl derivatives of palladium(II)

The title compounds (1, X=F; 2, X=Cl) were obtained in quantitative yield by refluxing together (NBu₄)₂[Pd₂(μ-Br)₂(C₆X₅)₄] and (NBu₄)₂[Pd₂(μ-Br)₂Br₄]. Treatment of 1 or 2 with AgClO₄ (Pd:Ag= 1:1) gave solutions which behaved as containing ‘Pd(C₆X₅)Br’. 1, 2 and the ‘Pd(C₆X₅)Br’ solutions were checked as precursors of mono-pentahalophenyl derivatives, yielding a variety of complexes [Pd(C₆X₅)Br(L-L)] (L-L=bipy, tmen, dpe, COD), [Pd(C₆X₅)BrL₂] (L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃), [Pd₂(μ-Br)₂(C₆X₅)₂L₂] (X=F, L=AsPh₃; X=Cl, L=SbPh₃) and (NBu₄)[Pd(C₆X₅)Br₂L] (X=F, L= py, AsPh₃, SbPh₃; X=Cl, L=p-TolNH₂, py, PPh₃, AsPh₃, SbPh₃). The solutions of ‘Pd(C₆X₅)Br’ proved to be the best general precursors of complexes [Pd(C₆X₅)BrL₂] although complexes with OPPh₃ could not be obtained.     

Hydrido-derivatives of [Ir4(CO)10(diphosphine)]: X-ray analyses of [Ir4H(CO)9(μ-Ph2PH(CH3)PPh2)] and [Ir4 H(CO)9(μ-Ph2P(CH2)nPPh2)] (n = 2, 3)

Some novel hydrido-anions of general formula [Ir₄H(CO)₉(μ-L-L)]⁻ (L-L = Ph₂PCH(CH₃)PPh₂, Ph₂P(CH₂)₂PPh₂, Ph₂P(CH₂)₃PPh₂ and Ph₂AsCH₂AsPh₂) have been obtained by the reaction of [Ir₄(CO)₁₀(μ-L-L)] with the base 1,8-diazabicyclo[5.4.0]undec-7-ene in wet dichloromethane. According to IR and ¹H, ³¹P and ¹³C NMR data at low temperature, these anionic derivatives display a single conformation in solution: three edge-bridging COs around the triangular basal face and both the hydride and the bidentate ligands located in axial positions relative to this face. The structures of four compounds were established by X-ray diffraction studies, which confirmed the configuration proposed on the basis of spectroscopic data.     

Cationic induced assembly of two 2D zinc-terephthalate polymeric networks

Based on templates of [Ph₃PCH₂Ph]Cl and [Ph₄P]Cl ([Ph₃PCH₂Ph] = benzyltriphenylphosphonium, [Ph₄] = tetraphenylphosphonium), the hydrothermal reactions of zinc acetate dihydrate, H₂tp (tp = terephthalate) and water give rise to two new zinc-terephthalate coordination polymers, [Ph₃PCH₂Ph][Zn(tp)Cl] (1) and [Ph₄P][Zn(tp)(H₂O)₂·0.5tp] (2). X-ray single-crystal structural analysis reveals that both 1 (C₃₃H₂₆ClO₄PZn) and 2 (C₃₆H₃₀O₈PZn) crystallize in the 2D non-interpenetrating layered supramolecular networks with guest organophosphonium cations. Due to template effect of different guest cations, 1 presents an interesting 2D smectite-like lamellar framework that formed by the 4-linked (4,4) anionic zinc-terephthalate polymeric network and the interlayer [Ph₃PCH₂Ph]⁺ exchangeable cations, while 2 shows a 2D 3-linked (6,3) H-bonded anionic zinc-terephthalate polymeric brickwall network with encapsulated guest [Ph₄P]⁺ cations. Both compounds are stable up to about 300 °C, and exhibit intense fluorescent emission band at 446 nm (λ_exc = 328 nm) for 1 and 420 nm (λ_exc = 340 nm) for 2 in the solid state at room temperature.     

Influence on reactivity of chloro ligand substitution in mononuclear cationic Pd(II) and Pt(II) triphos complexes: X-ray structure of the nitrate derivatives

The substitution of chloro ligand in [M(triphos)Cl]Cl complexes [M=Pd (1), Pt (2); triphos=Ph₂PC₂H₄P(Ph)C₂H₄PPh₂] by reaction with 1 equiv. of KX resulted in the formation of the ionic complexes [M(triphos)X]Cl [X=I, M=Pd (3), Pt (4); X=CN, M=Pd (5), Pt (6)]. Methanolic solutions of silver nitrate in excess displace the chloro ligand and counterion of 1 and 2, giving rise to the formation of the crystalline complexes [M(triphos)(ONO₂)](NO₃) [M=Pd (7), Pt (8)] suitable for X-ray diffraction studies. The complexes show a distorted square-planar environment around the metal, there being three coordination sites occupied by phosphorus atoms from the triphos and the fourth by the oxygen atom from a nitrate acting as monodentate ligand. A second NO₃ ⁻ is acting as counterion with D_3h symmetry. The use of a high excess of SnCl₂ in the presence of 1 equiv. of PPh₃ enabled the formation of complexes [M(triphos)(PPh₃)](SnCl₃)₂ [M=Pd (9), Pt (10)]. These complexes, in addition to [M(triphos)X]X [X=Br, M=Pd (1a), Pt (2a); X=I, M=Pd (1b), Pt (2b)], were synthesised and all Pt(II) complexes characterised by microanalysis. Mass spectrometry, IR spectroscopy, NMR spectroscopy and conductivity measurements were also used for characterisation. The structure and reactivity studies in solution were carried out by ³¹P{¹H} NMR. The trends in chemical shifts δ (P) and ¹J(¹⁹⁵Pt, ³¹P) coupling constants were used to establish a sequence in the X ligand exchange reactions. While [Pd(triphos)I]I (1b) undergoes a ring-opening reaction by titration with AuI, the analogous Pt(II) complex (2b) does not react. The formation of new five-coordinate Pd(II) and Pt(II) complexes was observed by titration of 5–8 with potassium cyanide.     

Adducts from mercury(I) and mercury(II) compounds with Bispyrazolylalkanes.X-Ray crystal structure of Bis(3,5-dimethylpyrazol-l-yl)methane(dicyano)-mercury(II)

The 1:1 adducts between thebis(3,5-dimethylpyrazol-1-yl)methane (L′-L′) or 2,2′-bis(pyrazol- 1-yl)propane (L″L″) ligand and HgX₂ (with X = Cl, CN or CO₂CF₃) have been obtained as well as [(L′L′)₂]Hg(ClO₄)₂ and the mercury(I) derivative (ligand)₂Hg₂(ClO₄)₂. The adducts have been characterized from analytical and spectral data (IR, proton and ¹³C NMR). Four-coordinated mercury is present in (L′L′)Hg(CN)₂, in which the metal-(NN)₂C ring adopts an asymmetric boat form. The molecular parameters are significantly different for the two independent molecules, the CHgC angles and the two Hg-N distances being 163.1(9)°and 2.55(1) plus 2.70(1) Å in the one case, and 148.2(8)° and 2.40(1) plus 2.51(1) Å, in the other; correspondingly the N-Hg-N angle, the ‘bite’ of the ligand, ranges from 79.0(5)° to 71.7(4)°, a value outside the range previously reported.     

Synthesis and spectroscopic studies of antimony pentachloride complexes with neutral oxygen, sulfur and selenium ligands

The compounds [SbCl₅(R₃EY)] (R = Me or Ph; E = P or As; Y = O or S) have been prepared from SbCl₅ and the appropriate ligand in CH₂Cl₂ or CCl₄ solutions, and characterised by analysis, IR, ¹H, ³¹P{¹H}, ¹²¹Sb NMR spectroscopy and conductance measurements. The [SbCl₅(μ-L-L)SbCl₅] L-L = Ph₂P(O)CH₂P(O)Ph₂, Ph₂P(O)(CH₂)₂P(O)Ph₂, Ph₂P(S)CH₂P(S)Ph₂, Ph₂As(O)CH₂As(O)Ph₂, and o-C₆H₄(P(O)Ph₂)₂ have been synthesised and similarly characterised. The unstable [SbCl₅(R₃PSe)] have been prepared at low temperatures and characterised by IR spectroscopy. In solution in chlorocarbons they decompose rapidly to Se and R₃PCl₂. The reactions of R₃SbS with SbCl₅ produced R₃SbCl₂.     

Strain in organometallics II: controlling the properties of tetra-coordinated iridium complexes using diastereomers of a bis(tropp) ligand system

The tetra-chelating ligands 1,2-bis[(5H-dibenzo[a,d]cyclohepten-5-yl)phenylphosphanyl]-ethane, bis(tropp^Ph)ethane, and 1,3-bis[(5H-dibenzo[a,d]cyclohepten-5-yl)phenylphosphanyl]-propane, bis(tropp^Ph)propane, were synthesised. For the binding of transition metals, these ligands offer two olefin moieties and two phosphorus centres and form mixtures of diastereomers with a R,S-configuration at the phosphorus centres (meso), or a R,R(S,S)-configuration (rac), respectively. meso/rac-bis(tropp^Ph)ethane was separated by fractional crystallisation and reacted with [Ir(cod)₂]OTf (cod=cylcooctadiene, OTf⁻=CF₃SO₃ ⁻) to give the penta-coordinated complex-cations meso/rac-[Ir(bis(tropp^Ph)ethane)(cod)]⁺, where the bis(tropp^Ph)ethane serves as tridentate ligand merely. One olefin unit remains non-bonded, however, a slow intra-molecular exchange between this olefin and the coordinated olefin unit was established (meso-[Ir(bis(tropp^Ph)ethane)(cod)]⁺: k<0.5 s⁻¹; rac-[Ir(bis(tropp^Ph)ethane)(cod)]⁺: k≈35 s⁻¹). The ligand meso/rac-bis(tropp^Ph)propane reacts with [Ir(cod)₂]OTf to give the corresponding complexes containing the tetra-coordinated 16-electron complex-cations meso/rac-[Ir(bis(tropp^Ph)propane)]⁺. The diastereomers were separated by fractional crystallisation. The complex rac-[Ir(bis(tropp^Ph)propane)]⁺ is reduced at relatively low potentials (E¹_1/2=−0.95 V, E²_1/2=−1.33 V versus Ag/AgCl) to give the neutral 17-electron complex [Ir(bis(tropp^Ph)propane)]⁰ and the 18-electron anionic iridate [Ir(bis(tropp^Ph)propane)]⁻, respectively. With acetonitrile, [Ir(bis(tropp^Ph)propane)]⁺ reacts to give the penta-coordinated complex rac-[Ir(MeCN)(bis(tropp^Ph)propane)]⁺ (K=45 M⁻¹, k_f=6×10³ M⁻¹ s⁻¹, k_d=1×10² s⁻¹) and with chloride to yield the relatively stable complex rac-[Ir(Cl)(bis(tropp^Ph)propane)] (k_d<0.5 s⁻¹). Compared to the rac-isomer, the meso-[Ir(bis(tropp^Ph)propane)]⁺ shows significantly cathodically shifted reduction potentials (E¹_1/2=−1.25 V, E²_1/2=−1.64 V versus Ag/AgCl), an acetonitrile complex could not be detected, and the chloro-complex, meso-[Ir(Cl)(bis(tropp^Ph)propane)], is much more labile (k_d≈20′000 s⁻¹). meso-[Ir(bis(tropp^Ph)propane)]⁺ reacts with one equivalent H₂ to give the trans-dihydride complex-cation, meso-[Ir(H)₂(bis(tropp^Ph)propane)]⁺, while the rac-isomer, rac-[Ir(bis(tropp^Ph)propane)]+, reacts with two equivalents H₂ to give rac-{Ir(H)₂(OTf)[(tropp^Ph)(H₂tropp^Ph)propane]}, a cis-dihydride complex containing a hydrogenated 10,11-dihydro-5H-dibenzo[a,d]cycloheptene unit, H₂tropp^Ph. The triflate anion in this complex is rather firmly bound and dissociates only slowly (k=29 s⁻¹). All differences between the different stereoisomers are attributed to the fact that the ligand backbone in the meso-isomer, meso-[Ir(bis(tropp^Ph)propane)]⁺, enforces a planar coordination sphere at the metal. On the contrary, already in the tetra-coordinated rac-[Ir(bis(tropp^Ph)propane)]⁺, the metal has a tetrahedrally distorted coordination sphere which does not impede the reduction to the d⁹-Ir(0) and d¹⁰-Ir(−1) complexes and allows more easily a distortion towards a trigonal bipyramidal (tbp) or octahedral structure for penta- or hexa-coordinated complexes, respectively. A comparison of the NMR data for iridium bonded olefins in equatorial or axial positions in tbp structures shows that the latter experience only modest metal-to-ligand back-donation, while the olefins in the equatorial positions have a high degree of metallacyclopropane character.     

Synthesis,structure, and thermal behavior of discrete Co(II), Ag(I), and Pd(II) complexes with 2,3-bis(2-pyridyl)quinoxaline. Insight into coordination modes

The reactions of 2,3-bis(2-pyridyl)quinoxaline (bpq) with CoCl₂·6H₂O, Ag(CH₃CN)₄BF₄, and PdCl₂(C₆H₅CN)₂ produce [CoCl₂(bpq)]₂·2CHCl₃, [Ag(bpq)CH₃CN]₂(BF₄)₂·2CH₃CN, and [PdCl₂(bpq)], respectively. All the products are discrete 1:1 (metal:bpq) adducts, where the chelation mode of the bpq is dependent upon the metal atoms. The structure of [CoCl₂(bpq)]₂·2CHCl₃ is a centrosymmetric Cl-bridged four-membered dimer, [Co₂Cl₂], in which the bpq is bonded to the cobalt(II) atom in an anisobidentate mode with the nitrogen donors of pyridine and pyrazine rings. For [Ag(bpq)CH₃CN]₂(BF₄)₂·2CH₃CN, each bpq ligand connects two tetrahedral silver(I) ions in a tridentate mode, resulting in a cationic cyclic dimer. The structure of [PdCl₂(bpq)] approximates to a molecular rocking chair with an isobidentate bpq through the nitrogen donors of 2-pyridyl rings. The compounds exhibit significant and characteristic relationships between the structures and their thermal properties. For [CoCl₂(bpq)]₂·2CHCl₃, the solvate chloroform molecules are safely contained up to 144°C, but drastically evaporate above this temperature. The striking feature of [Ag(bpq)CH₃CN]₂(BF₄)₂·2CH₃CN is that the skeletal cyclic dimer is basically retained after dissociation of the coordinated acetonitriles in the solid state.     

One-dimensional silver(I) and mercury(II) complexes with 1,4-bis(1-benzyl-benzimidazol-2-yl)cyclohexane (N-BBzBimCH)

The crystal structures of four Ag(I) and Hg(II) complexes of the ligand 1,4-bis(1-benzyl-benzimidazol-2-yl)cyclohexane (N-BBzBimCH) have been described, that is, [Hg₂(N-BBzBimCH)Cl₄] (1), [Hg(N-BBzBimCH)Br₂] (2), [Ag(N-BBzBimCH)](NO₃)(H₂O) (3) and [Ag₂(N-BBzBimCH)(CF₃OCO)₂] (4). All these compounds show 1D polymeric structures in the solid state. In complexes 1 and 4, the chloride ions and the trifluoroacetate groups bridge the [Hg₂(N-BBzBimCH)Cl₂] and [Ag₂(N-BBzBimCH)] fragments, respectively, to generate 1D polymers. While the bromide ions in complex 2 and nitrate groups in complex 3 are only serving as terminal ligands to suffice the coordination geometry of the metal centers. In all cases, weak intermolecular interactions such as C-H?X (X = Cl, Br) contacts, hydrogen bonds, π-π interactions and C-H?π stacking play important roles to extend the 1D chain structures to 2D network. Solid state fluorescence of these compounds was also studied.