Mononuclear and heterobimetallic palladium(II) and platinum(II) complexes containing the mixed ligands <Emphasis Type="Italic">N</Emphasis>-(2-pyridyl or 2-pyrimidyl) acetamide and tertiary diphosphine

Palladium(II) and platinum(II) complexes containing mixed ligands N-(2-pyridyl)acetamide (AH) or N-(2-pyrimidyl)acetamide (BH) and the diphosphines Ph₂P(CH₂) _n PPh₂, (n = 1, 2 or 3) have been prepared. The prepared complexes [Pd(A)₂(diphos)] or [Pd(B)₂(diphos)] have been used effectively to prepare bimetallic complexes of the type [(diphos)Pd(μ-L)₂M′Cl₂] where M′ = Co, Cu, Mn, Ni, Pd, Pt or SnCl₂; L = A or B. The prepared complexes were characterized by elemental analysis magnetic susceptibility, i.r. and UV–Vis spectral data. ³¹P–{¹H}-n.m.r. data have been applied to characterize the produced linkage isomers.     

Activation of 1, 2‐Dihydrodisilanes at Platinum(0) Phosphine Complexes: Syntheses and Structures of Bissilyl Platinum(II) Complexes

The bissilyl complexes 3 – 6 were synthesized by reactions of the platinum(0) complexes [Pt(η²‐C₂H₄)(diphos)] ( 1 : diphos = dppe; 2 : diphos = dcpe) with the disilanes 1, 1,2, 2‐tetramethyldisilane and 1, 1,2, 2‐tetraphenyldisilane via Si–Si bond activation. The molecular structures of 4 and 5 in the solid state are reported. The reaction of 2 with HPh₂SiSiPh₂H led to the immediate formation of the hydrido disilanyl complex [Pt(H)(SiPh₂SiPh₂H)(dcpe)] ( 7 ), which converts slowly into the bissilyl complex [Pt(SiHPh₂)₂(dcpe)] ( 6 ). The latter was reported before to be a η²‐disilene complex.     

Square‐Planar Carbonylchlororhodium(I) Complexes Containing trans‐Spanning Diphosphine Ligands as Catalysts for the Carbonylation of Methanol

The rhodium(I) complexes trans‐[Rh(diphos)(CO)Cl] 7 (diphos=pbpb), 8 (diphos=nbpb), and 9 (diphos=cbpb) were synthesized (Scheme 4) and used as catalysts for the carbonylation of MeOH to AcOH (Scheme 1). The trans coordination imposed by the rigid C‐spacer framework of the diphos ligands pbpb, nbpb, and cbpb, demonstrated by ³¹P‐NMR and IR spectroscopy of 7 – 9 and unambiguously confirmed by single‐crystal X‐ray structure analysis of 7 , improved the thermal stability of the rhodium(I) system under carbonylation conditions and, hence, the catalytic performance of the complexes. For the catalytic carbonylation of MeOH, the active catalyst could be prepared in situ from the mixture of [Rh(CO)₂Cl]₂ and the corresponding diphos ligand pbpb, nbpb, or cbpb, giving the same results as carbonylation in the presence of the isolated complexes 7, 8 or 9 (see Table). The highest activity was observed for complex 7 (or the mixture [Rh(CO)₂Cl]₂/pbpb, the catalytic turnover number (TON) being 950 after 15 min (170°, 22 bar).     

Complexes of metallons with phosphorus or arsenic containing ligands. II. complexes ortho-carboxyphenyltertiaryarsines with mercury (II) halides

Ortho-carboxyphenyl-dimethylarsine (CPDMA), ortho-carboxpyhenyldiphenylarsine (CPDPA) and ortho-carboxyphenyldi(p-tolyl)arsine (CPDTA) react with mercury(II) halides to yield complexes having the formula HgX₂L where X is Cl, Br or I and L is ligand. In view of infrared spectral data these complexes have been classified into two classes: (a) those in which the carboxyl group of the ligand remains free (ligand being monodentate), and (b) those in which the ligand acts as a bidentate group. The complex Hg(Cl₂) · CPDPA is the only example of type (a) and has been assigned a dimeric halogen bridged structure. The remaining eight complexes are assumed to be monomeric. A tetrahedral structure is proposed for all the nine complexes.     

Reaction of hexanuclear niobium and tantalum halide clusters with mercury(II) halides. II. Semiconducting compounds with [Ta6Cl12]3+ unit

A series of paramagnetic clusters of the composition [(Ta₆Cl₁₂)Cl(H₂O)₅][HgX₄] · 9H₂)O (X = Cl, Br, I) has been prepared by the reaction of [Ta₆Cl₁₂]³⁺ methanol-water solutions with HgX₂ and NaX halides. The structure of [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O has been solved by X-ray diffraction in the cubic space group Fd 3m. Crystal data: a = 20.036(2) Å, V = 8043.0(1) ų, Z = 8, R = 0.048 (R_w = 0.051). The structure is composed of an octahedral [(Ta₆Cl₁₂)Cl(H₂O)₅]²⁺ cluster cation, tetrahedral [HgBr₄]²⁻ anion and crystal water molecules. The 2mm symmetry of the octahedron is reduced by the statistical distribution of the five water molecules, O(1), and chlorine, Cl(2), at the terminal coordination sites. Thus, the distances Ta-O(1) and Ta-Cl(2) are averaged to the value of 2.32(2) Å. The Ta-Ta and Ta-Cl(1) bond distances are 2.911(1) Å and 2.440(3) Å, respectively, whereas the Hg-Br bond distance is 2.564(3) Å. The cluster [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O is semiconducting with two levels governing conductivity with respective activation energies, E_al = 0.24 eV and E_a2 = 0.17 eV.     

Reaction of hexanuclear niobium and tantalum halide clusters with mercury(II) halides. II. Semiconducting compounds with [Ta6Cl12] unit

A series of paramagnetic clusters of the composition [(Ta₆Cl₁₂)Cl(H₂O)₅][HgX₄] · 9H₂)O (X = Cl, Br, I) has been prepared by the reaction of [Ta₆Cl₁₂]³⁺ methanol-water solutions with HgX₂ and NaX halides. The structure of [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O has been solved by X-ray diffraction in the cubic space group Fd 3m. Crystal data: a = 20.036(2) Å, V = 8043.0(1) ų, Z = 8, R = 0.048 (R_w = 0.051). The structure is composed of an octahedral [(Ta₆Cl₁₂)Cl(H₂O)₅]²⁺ cluster cation, tetrahedral [HgBr₄]²⁻ anion and crystal water molecules. The 2mm symmetry of the octahedron is reduced by the statistical distribution of the five water molecules, O(1), and chlorine, Cl(2), at the terminal coordination sites. Thus, the distances Ta-O(1) and Ta-Cl(2) are averaged to the value of 2.32(2) Å. The Ta-Ta and Ta-Cl(1) bond distances are 2.911(1) Å and 2.440(3) Å, respectively, whereas the Hg-Br bond distance is 2.564(3) Å. The cluster [(Ta₆Cl₁₂)Cl(H₂O)₅][HgBr₄] · 9H₂O is semiconducting with two levels governing conductivity with respective activation energies, E_al = 0.24 eV and E_a2 = 0.17 eV.     

Organic chemistry of subvalent transition metal complexes: XI. Oxidative additions of nickel(0) complexes to carbon-carbon bonds in alkynes: Nickelirenes and nickeloles as catalytic carriers in the oligomerization of alkynes

The formation of 2,3,4,5-tetraphenylnickelole-bis(triphenylphosphine) (IIIa) and 2,3,4,5-tetraphenylnickelole-bis(1,2-diphenylphosphino)ethane (IIIb), either from (E,E)-1,2,3,4-tetraphenyl-1,3-butadien-1,4-ylidenedilithium (I) and the corresponding nickel(II) chloride-phosphine complexes (II) or from the reduction of η⁴-tetraphenylcyclobutadienenickel(II) bromide dimer (XII) in the presence of phosphines, proceeds in good yields. Nickelole IIIa displays physical and chemical properties consistent with its structure and is a catalyst for the trimerization of diphenylacetylene. Nickelole IIIb is a highly associated structure but in its chemical response to alkynes, HOAc, O₂, Br₂, NaAlEt₂H₂ and heat displays the properties of a nickelole, rather than a cyclobutadienenickel(0) complex. Attempts to generate IIIb photochemically from η⁴-1,5-cyclooctadiene(η⁴-tetraphenylcyclopentadienone)nickel and diphos failed, but it was shown that structural types, such as η⁴-tetraphenyl-cyclopentadienone(diphos)nickel (a model for the structure suggested by Hoberg and Richter for IIIb), are unstable.Oligomerizations of diphenylacetylene by bis(1,5-cyclooctadiene)nickel were retarded by conducting the reaction in THF or in the presence of diphos. This retardation permitted the interception of products (cis-stilbene and (E,E)-1,2,3,4-tetraphenyl-1,3-butadiene) diagnostic for the intermediacy of nickelirenes and nickeloles. Deuterium labeling verified the presence of carbon-nickel bonds. These trapping experiments, together with findings on the thermal behavior of nickeloles, are combined into a comprehensive view of the cyclotrimerization, cyclotetramerization and linear polymerization of alkynes by nickel(0).     

Reactions of S4N4 with phosphineiridium(I) complexes. Synthesis and crystal structures of [(dppen)2Ir(S2N2)](BPh4) · 0.5CH3COCH3 and (dppen)2Ir(S2N2)[W(CO)5](BPh4) · 0.5CH2Cl2

The iridium(I) complexes [(diphos)₂Ir(CO)](Bph₄) react with S₄N₄ to give the octahedral derivatives [(diphos)₂Ir(S₂N₂)](BPh₄), (diphos = bis(diphenylphosphino)ethylene, dppen, (1); diphos = bis(diphenylphosphino_methane, dppm, (2). Reaction of 1 with W(CO)₆ gave the carbonyl derivative (dppen)₂Ir(S₂N₂)[W(CO)₅](BPh₄), 3). The crystal structures of 1 and 3 have been determined by X-ray diffraction. In both compounds the iridium atom shows a distorted octahedral geometry, being surrounded by two bidentate phosphine ligands and by the sulfur and a nitrogen atom of the open-chain disulfur dinitride ligand. In 3 the nitrogen atom of the S₂N₂ group which is not coordinated to the iridium atom is linked to the tungsten atom of a W(CO)₅ residue. The ³¹P NMR spectra of 1 and 3 are indicative of a rigid structure in solution at room temperature.     

Structural, theoretical and multinuclear NMR study of mercury(II) complexes with a new ambidentate phosphorus ylide

The reaction of the new ambidentate ylide, Ph₃PCHCOCH₂COOC₂H₅ (EAPPY), with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as the solvent leads to binuclear complexes of the type [EAPPY·HgX₂]₂ (X = Cl (1), Br (2) and I (3)). Single crystal X-ray analysis reveals the presence of a centrosymmetric dimeric structure containing the ylide and HgX₂ (X = Br or I)_. The IR and NMR data of the product [(EAPPY)·HgCl₂]₂ (1), formed by the reaction of mercury(II) chloride with the same ylide, are similar to those of 2 and 3. Analytical data indicate a 1:1 stoichiometry between the ylide and Hg(II) halide in each of the three products. Theoretical studies indicate that the nature of the R group in ylides of the type Ph₃PCHCOR has a weak effect on the Hg-C(ylide) bond length in binuclear Hg₂L₂I₄ complexes.     

Infrared and Raman spectra of ethylene trithiocarbonate complexes of some Zn(II), Cd(II) and Hg(II) halides

Coordination compounds of ethylene trithiocarbonate (ETTC) with some Zn(II), Cd(II) and Hg(II) halides have been prepared, characterized and their infrared and Raman spectra recorded. The i.r. spectra in the range 4000-400 cm⁻¹ suggest that the organic ligand is bonded to the metal ions through its exocyclic sulphur atom, whereas the far-i.r. and Raman spectra show that the complexes of the type HgX₂(ETTC) (X = Cl, Br or I) possess a trans dimeric halogen-bridged structure. The Cd(II) and Zn(II) species are of the type MX₂(ETTC)₂ and they possess a pseudotetrahedral structure of C_2υ symmetry.     

Studies of radioactivity and heavy metals in phosphate fertilizer

The extraction of mercury(II) from chloride and thiocyanate solutions has been studied by tracer techniques using bis(2-ethylhexyl) sulphoxide (B2EHSO) in benzene as an extractant. These extraction data have been analyzed theoretically by taking into account complexation of the metal in the aqueous phase by inorganic ligands and plausible complexation in the organic phase. The results demonstrate that Hg(II) is extracted as HgX₂ and HgX₂·nB2EHSO (where X=Cl^– or SCN^– andn=1 or 2). The effect of the foreign ions on the extraction of Hg(II) has also been investigated.     

Molecular weight determination of coordination and organometallic oligomers by T1 and NOE constant measurements: concepts and challenges

This paper describes how to determine molecular weights of coordination and organometallic polymers (or rather oligomers) in solution using spin-lattice relaxation time (T₁) and Nuclear Overhauser Enhancement constant (η_NOE) measurements. The methodology is explained using simple organometallic-complexes such as M(CN-t-Bu)₄⁺ complexes (M = Cu, Ag). Very good results are obtained for oligomers that exhibit a rigid structure. Conversely, very poor results are extracted when the materials show flexible chains in the backbone. The typical examples for rigid and flexible oligomers are the {Ag(dmb)₂⁺}_n (dmb = 1,8-diisocyano-p-menthane), and {Pd₂(dmb)₂(diphos)²⁺}_n (diphos = dppa, dppb, dpppent, and dpph) as well as {Pd₂(diphos)₂(dmb)²⁺}_n (diphos = dppe, dppr, and dppp R ; R = O(CH₂)₂O-naphthyl), respectively.     

New cationic monocarbonyls of manganese(I) with nitriles and isonitriles

Summary Monocarbonyls of manganese(I) with two chelating diphosphinestrans-[Mn(CO)(diphos)₂(L)]A, [diphos = 1,2-bis(diphenylphosphino)ethane, dppe, or bis(diphenylphosphino)methane, dppm; L=nitriles, NCR (NCMe, NCEt, NCPh, or NCCH₂Ph), dinitriles, NCGCN (NCCH₂CN, NCCH₂CH₂CN, oro-(NC)₂C₆H₄), isonitriles, CNR, (CNPh, or CNBu^t); A = C1O ₄ ^– or PF ₆ ^– ],trans-[(Mn(CO)(dppm)₂)₂(-NCCH₂CH₂CN)](ClO₄)₂ and the monocarbonyl with one diphosphine,mer-[Mn(CO)(dppe)(CNBu^t)₃]ClO₄, have been prepared fromtrans-[Mn(CO)(diphos)₂Br].In this paper we have adopted the convention that gives positive shift to signals at higher frequency of ext. H₃PO₄.     

A Neutral Tetraphosphacyclobutadiene Ligand in Cobalt(I) Complexes

The unusual reactivity of the newly synthesized β‐diketiminato cobalt(I) complexes, [(L^DepCo)₂] ( 2 a , L^Dep=CH[C(Me)N(2,6‐Et₂C₆H₃)]₂) and [L^DippCo ? toluene] ( 2 b , L^Dipp=CH[CHN(2,6‐ⁱPr₂C₆H₃)]₂), toward white phosphorus was investigated, affording the first cobalt(I) complexes [(L^DepCo)₂(μ₂:η⁴,η⁴‐P₄)] ( 3 a ) and [(L^DippCo)₂(μ₂:η⁴,η⁴‐P₄)] ( 3 b ) bearing the neutral cyclo‐P₄ ligand with a rectangular‐planar structure. The redox chemistry of 3 a and 3 b was studied by cyclic voltammetry and their chemical reduction with one molar equivalent of potassium graphite led to the isolation of [(L^DepCo)₂(μ₂:η⁴,η⁴‐P₄)][K(dme)₄] ( 4 a ) and [(L^DippCo)₂(μ₂:η⁴,η⁴‐P₄)][K(dme)₄] ( 4 b ). Unexpectedly, the monoanionic Co₂P₄ core in 4 a and 4 b , respectively, contains the two‐electron‐reduced cyclo‐P₄^2? ligand with a square‐planar structure and mixed‐valent cobalt(I,II) sites. The electronic structures of 3 a , 3 b , 4 a , and 4 b were elucidated by NMR and EPR spectroscopy as well as magnetic measurements and are in agreement with results of broken‐symmetry DFT calculations.     

The synthesis and structural characterisation of the mercury (II) halide complexes of the phosphorus ylide carbethoxymethylenetriphenylphosphorane

The reaction of the ylide carbethoxymethylenetriphenylphosphorane (EPPY), Ph₃PCHCOOEt, with mercury (II) halides has been investigated. The resulting dimeric mercury (II)-ylide complexes are isostructural and of the form [(EPPY)(HgX₂)]₂ where X is either bromine (1), chlorine (2), or iodine (3). These complexes have been characterised by spectroscopic techniques and X-ray diffraction. The ylide ligands have been shown to be C-coordinated to the mercury (II) atom.     

Ab Initio Calculations of Hydroxoplatinum Compounds: II. Binuclear Platinum(IV) Superoxo Complexes

The structural and spectral data have been obtained by ab initio methods for the [(OH)₄Pt(μ-O₂)(μ- OH)Pt(OH)₄]^2?, [(OH)₄Pt(μ-O₂)(μ-OH)Pt(OH)₄(OH)]^3?, [(OH)₅Pt(μ-O₂)Pt(OH)₅]^3?, and [(H₂O)(OH)₄Pt(μ- O₂)Pt(OH)₄(H₂O)]- clusters, corresponding to binuclear platinum(IV) superoxo complexes with one and two bridges. The data obtained are in good agreement with experimental data and make it possible to judge the structure of available complexes.     

Synthesis and chemistry of tris(2-pyridyl)phosphine and bis(2-pyridyl)phenylphosphine complexes of mercury(II) X (X = Br,Cl) and X-ray crystal structural determination of [HgBr2(PPh(2-py)2)2]

Mercury(II) halide complexes [HgX₂(P(2-py)₃)₂] (X?=?Br (1), Cl (2)) and [HgX₂(PPh(2-py)₂)₂] (X?=?Br (3), Cl (4)) containing P(2-py)₃ and PPh(2-py)₂ ligands (P(2-py)₃ is tris(2-pyridyl)phosphine and PPh(2-py)₂ is bis(2-pyridyl)phenylphosphine) were synthesized in nearly quantitative yield by reaction of corresponding mercury(II) halide and appropriate ligands. The synthesized complexes are fully characterized by elemental analysis, melting point determination, IR, ¹H, and ³¹P-NMR spectroscopies. Furthermore, the crystal structure of [HgBr₂(PPh(2-py)₂)₂] determined by X-ray diffraction is also reported.     

Neutral and cationic dicarbonyl complexes of manganese (I) with diphosphines

The reaction of BrMn(CO)₅ with dppm in refluxing toluene gives the neutral compunds cis-cis-BrMn(CO)₂(dppm)₂ which has been shown by ³¹P NMR spectroscopy to have one dppm monodentate and the other bidendate. This complex reacts with TIPF₆ in dichloromethane solution to give the salt cis-[Mn(CO)₂-(dppm)₂]PF₆ or, if the reaction is carried out in the presence of CO, the salt mer-[Mn(CO)₃(dppm)₂]PF₆ which also has one monodentate dppm (by ³¹P NMR). The cationic complex cis-[Mn(CO)₂(dppm)₂]⁺ isomerizes to the transisomer when irradiated with UV light, while heating of the latter gives back the cis-isomer. The perchlorate salts of the cation cis-[Mn(CO)₂(dppm)₂⁺ can be prepared by reacting fac-O₃ClOMn(CO)₃(dppm) withdppm in refluxing toluene, and trans-[Mn(CO)₂(diphos)(diphos)′]⁺, diphos or diphos′ being dppm or dppe, by treating the fac-O₃ClMn(CO)₃(diphos) with dppm or dppe under UV irradiation.     

Structural,theoretical and multinuclear NMR study of mercury(II) complexes of phosphorus ylides: Mono and binuclear complexes

Reaction of phosphorus ylide Ph₃PCHC(O)C₆H₄Cl (Y₁) with HgX₂ (X = Cl, Br and I) and ylide (p-tolyl)₃PCHC(O)CH₃ (Y₂) with HgI₂ in equimolar ratios using methanol as solvent leads to binuclear products. The bridge-splitting reaction of binuclear complex [(Y₁) · HgCl₂]₂ by DMSO yields a mononuclear complex containing DMSO as ligand. O-coordination of DMSO is revealed by single crystal X-ray analysis in mononuclear complex of [(Y₁) · HgCl₂ · DMSO]. C-coordination of ylides is confirmed by X-ray structure of binuclear complex [(Y₂) · HgI₂]₂. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. Theoretical studies on mercury(II) complexes of Y₁ show that formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is more favorable than that of binuclear complexes.     

Cyclometalated Iridium Bipyridine Complexes with Peripheral Antimony Substituents

As part of our ongoing efforts in the development of main group Lewis acids as anion receptors, we have investigated the synthesis of cyclometalated bipyridine iridium(III) complex decorated by antimony moieties. Reaction of 4-(diphenylstibino)-2,2'-bipyridine ( L ) with [(ppy)₂Ir(μ-Cl)]₂ afforded the corresponding tris-chelate iridium complex [(ppy)₂Ir L ]⁺ ([ 1 ]⁺), which was isolated as a hexafluorophosphate salt ([ 1 ][PF₆]). Reaction of [ 1 ][PF₆] with excess PhICl₂ in DMSO induced the conversion of the diphenylantimony moiety of [ 1 ]⁺ into an anionic diphenyltrichloroantimonate leading to a zwitterionic complex referred to as 2 -Cl. Complexes [ 1 ][PF₆] and 2 -Cl were characterized by NMR and the structure of 2 -Cl confirmed using X-ray diffraction. DFT calculations and electrochemical measurments show that the electron-rich diphenyltrichloroantimonate moiety in 2 -Cl cathodically shifts the Ir(III/IV) redox couple. Luminescence measurements also show that 2 -Cl is less emissive than [ 1 ]⁺.