Small Bite Angle Research Articles

Molecular structure and vibrational spectra of bis- N,N'-diethyldithiocarbamate compounds with closed-shell metal ions

The molecular structures of isolated M(Et 2dtc) 2 (M is Zn I I, Cd I I, Hg I I, Pb I I; Et 2dtc is (C 2H 5) 2NC(S)S −) have been examined by the PM3 and MMP2 methods. The compounds have a compressed tetrahedral (different from the solid state for Zn, Cd, Hg) or pyramidal helical (the same as in the solid state for Pb) MS 4 group. These structures are attributed to the presence of highly strained 4-membered rings MS 2C and small bite angles. The pyramidal structure of the Pb(Et 2dtc) 2 compound suggests that the Pb I I s 2 lone pair is stereochemically active. Raman spectra recorded in the solid state and in solution (CHCl 3 or CH 2C1 2) were compared in an attempt to trace the changes that occur in the metal coordination sphere upon dissolution. The band splittings in the solid-state Raman spectra of Zn(Et 2dtc) 2 and Cd(Et 2dtc) 2 were attributed to the intermolecular couplings in the dimeric structures: these splittings disappear in the solution spectra. In agreement with its monomeric solid-state structure, the solid state and solution spectra of Pb(Et 2dtc) 2 were coincident.

An NMR and single-crystal X-ray diffraction structural study of Ru II [12]aneS 4 polypyridyl complexes

The synthesis of a series of Ru II complexes with the thioether ligand [12]aneS 4 (1,4,7,10-tetrathiocyclododecane) and various polypyridyl ligands was carried out using [Ru(DMSO) 4CL 2] (DMSO- = dimethylsulphoxide) as a starting material. The first synthetic step involved the introduction of the thioether ligand and the isolation of the compound [Ru([12]aneS 4)Cl 2]. The polypyridyl ligands were then exchanged to give a series of complexes [Ru([12]aneS 4)(X)] 2+ [X = 1,10 phenanthroline (phen), 2,2′-bipyridyl (bpy) and 4,7′-diphenyl-1, 10-phenanthroline (dip)]. Crystal structures of the metal complexes [Ru([12]aneS 4)(bpy)]Cl 2·4H 2O, [Ru([12]aneS 4)(phen)]Cl 2·4.25H 2O and [Ru([12]aneS 4)(dip)]Cl 2·2H 2O all show the Ru centre in a distorted cis-octahedral environment, in which the equatorial coordination plane is formed by two S-donor atoms of the macrocyclic ligand [12]aneS 4 and two N-donor atoms of a polypyridyl ligand : bpy, phen or dip. The hexa coordination is completed via the remaining sulfur atoms of the macrocycle. The distortion of the octahedral geometry is associated with the small cavity size of macrocyclic ligand and small bite angle of the bidentate polypyridyl ligands [77.9(3)° bpy, 79.6(3) phen and 77.4(4)° dip]. The small cavity size of [12]aneS 4 precludes the sulfur atoms of the macrocycle achieving axial positions of an ideal octahedron leading to angles, S axRuS ax, of 162.5(2), 161.9(1) and 162.0(1)° for the bpy, phen and dip complexes respectively. A 1H and 13C NMR study of the complexes [Ru([12]aneS 4)(phen)] 2+, [Ru([12]aneS 4)(bpy)] 2+ and [Ru([12]aneS 4)(dip)] 2+ was carried out. The 1H spectra exhibit broad lines for the H-2 and H-9 protons of the polypyridyl ligand and the CH 2 protons of the [12]aneS 4 ligand. A variable temperature study indicated that exchange processes were taking place in solution, most probably involving cleavage of the RuN bond as a result of the strain on the octahedral environment of the small cavity size of the [12]aneS 4 macrocycle.

Polychlorinated Biaryl Heterocycles as Potential Ligands. Reactions between Octachloro-1,10-phenanthroline and -2,2′-bipyridine with Copper(I) and Other Metal Ions

Perchlorinated derivatives of the common o-diimine chelate ligands 2,2′-bipyridine and 1,10- phenanthroline were synthesized and tested for their coordination behavior towards metal ions. Octachloro-1,10-phenanthroline (ocp) was obtained via chlorination with PCl5 under pressure (300°C, 18 h). It fails to form stable complexes with e.g. Fe2+, Mn2+, Ru2+, Ni2+. Zn2+ or Cd2+, but yields complex cations [M(ocp)2]+ with M = Cu, Ag. The crystal structure analy­sis of the red tetrafluoroborate of the copper(I) complex cation reveals a distorted tetrahedral coordination at the metal with a slight tendency towards the trigonal-pyramidal arrangement; two essentially planar ligands with small bite angles intersect at almost right angle. Relative to conventional bis(1,10-phenanthroline)copper(I) complexes with similar structures. [Cu(ocp)2]+ has oxidation and reduction potentials shifted positively by about 1 V which leaves the energy of the main MLCT absorption features little changed. Attempts to synthesize RuCl2(ocp)2 in DMF produced as substituted product a symmetrical bis(dimethylamino)-hexachloro-1,10-phenanthroline which can be oxidized electrochemically in two steps. In contrast to ocp, octachloro-2,2′-bipyridine (ocb) showed no detectable complexation with Cu+ and a very neg­ative reduction potential, most probably due to its inability to exhibit a low-energy coplanar conformation.

Rhenium(V) Oxo Complexes of Novel N(2)S(2) Dithiourea (DTU) Chelate Ligands: Synthesis and Structural Characterization.

The compounds RNHC(=S)NH(CH(2))(n)()NHC(=S)NHR were prepared in a search for new, relatively small N(2)S(2) ligands. These dithiourea (DTU) ligands are the first chelates containing two potentially bidentate thiourea moieties. A one-step reaction of 1,3-diaminopropane (1) with aryl or alkyl isothiocyanates or of 1,2-diaminoethane (2) with phenyl isothiocyanate afforded the target ligands in excellent yields (95-98%). The Re(V)=O complexes of RNHC(=S)NH(CH(2))(3)NHC(=S)NHR ligands were obtained through ligand exchange reactions with Re(V) precursors. The chemistry required neither protection of the sulfur atoms for ligand synthesis nor deprotection prior to metal complexation. The structure of (1-phenyl-3-(3-phenylthioureido)propyl]thioureato)oxorhenium(V) (7a), determined by X-ray diffraction methods, revealed the expected pseudo-square-pyramidal geometry with an N(2)S(2) basal and an apical oxo donor set. Both coordinated N's (N(c)) were deprotonated. One uncoordinated N (N(u)) was deprotonated, producing a neutral complex containing an unexpected new type of dianionic, four-membered N,S chelate. In the crystal, the N(u) atoms, N(3)H and N(4), of one complex each formed an H-bond with N(4) and N(3)H, respectively, of a symmetry-related complex. The N(c)-C-S bond angles (106.1(6) and 101.5(6) degrees ) were severely distorted from the 120 degrees expected for an sp(2)-hybridized C. However, these small bite angles and the large N-Re-N bond angle (86.1(3) degrees ) allowed for the formation of two four-membered chelate rings with normal Re-N and Re-S bond distances. Attempts to prepare complexes with the PhNHC(=S)NH(CH(2))(2)NHC(=S)NHPh ligand were unsuccessful. These results suggest that a central five-membered chelate ring is too small to accommodate bidentate coordination of both thiourea moieties. NMR studies in methanol established that the neutral complex with one uncoordinated N deprotonated was the favored form in neutral and basic solutions. However, under acidic conditions, a cationic form with both uncoordinated N's protonated was favored.

Synthesis, structural characterisation and nuclear magetic resonance studies of cobalt complexes of pyridonate ligands

A series of heteroleptic cobalt(II) complexes of diimine and pyridonate ligands have been synthesized from cobalt(II) acetate, with the general stoichiometric formula [Co(xhp)2L][xhp = 6-methyl-(mhp), 6-chloro-(chp), 6-bromo-(bhp) or 6-fluoro-2-pyridonate (fhp); L = 2,2′-bipyridyl (bipy), 4,4′-dimethyl-2,2′-bipyridyl (dmbipy), 1,10-phenanthroline (phen) or di-2-pyridylamine (Hdpa)]. Four have been characterised by X-ray crystallography. The compounds [Co(mhp)2(phen)], [Co(chp)2(Hdpa)]·H2O and [Co(bhp)2(dmbipy)] crystallise as mononuclear species containing six-co-ordinate cobalt sites. The co-ordination geometry of the metal is distorted due to the small bite angle of the chelating xhp ligands. The fourth complex, [{Co(µ-fhp)-(fhp)(dmbipy)}2], crystallises as a dinuclear unit with the cobalt atoms bridged by the exocyclic O atom of one fhp ligand. The Co ⋯ Co distance is 3.208(6)A. A fifth complex, [{Co(µ-bhp)(O2CMe)(dmbipy)}2], has been characterised in which two cobalt atoms are bridged by the O atom from a bhp ligand, giving a Co ⋯ Co separation of 3.158(4)A. The NMR studies of the complexes [Co(xhp)2(dmbipy)] revealed large paramagnetic shifts, especially for the 6,6′-protons of the dmbipy unit. The magnitude of the shift varies depending on the pyridonate ligand used, with the largest shifts found for fhp and the smallest for mhp. This shift correlates with the basicity of the N-donor atom of the xhp ligands and hence with the co-ordinative ability of the pyridonate ligands. The synthesis of 6-fluoro-2-pyridone (Hfhp) is reported for the first time.

Structural comparison to the molybdenum site of nitrogenase. Synthesis and crystal structure of binuclear oxomolybdenum(V) complex with both o‐mercaptophenolate and alkoxide ligands

AbstractComplex (n‐Bu4N)[Mo2O2(OMe)(mp)3] [1, mp = (o‐OC6H4S)2−] was synthesized by the reaction of MoOCl3(THF)2 and Na2mp in EtOH and crystallized in monoclinic space group P21/n with crystal data: a = 13.910(3), b = 23.554(3), c=12.558(2) Å, β = 105.20(2)˙. Z = 4, Do = 1.455g/ cm3, final R = 0.077 for 5325 reflections [I>3s̀(I)]. The two [Mo(O)mp]+ moieties are bridged by one 1,2‐bidentate ligand mp2− with exceedingly small bite angle (69.0˙) and bite distance · (2.70Å) and by a methoxy group. The structure can be interpreted as two distorted octahedra around the Mo atoms sharing a face. Attempts have been made to provide structural informations for the syntheses of modelling compounds of FeMoco by comparing the Mo—O and Mo—S bond distances of o‐mercaptophenolate ligated compounds to those of the molybdenum site of nitrogenase.

Pyridine‐2‐thiolato Complexes of VII, VIII, and VIV with Unusual Structural Features

One of the extremely rare thiolatovanadium(II) complexes, [V(tmeda)(pyt)2] (1) is formed in the reaction of sodium pyridine-2-thiolate [Na(pyt)] with [VCl2(tmeda)2]. The octahedral structure of 1 is distorted because of the small bite angle of the pyt− ligand. In both dinuclear complexes [Na(thf)2V(pyt)4] and [V2O2(pyt)4] (2) the pyt− ligand has an unusual μ-η1:η2 bonding mode, but in 2 the pyt− bridge is unsymmetric.

Synthesis and solution behavior of mononuclear palladium(II) and platinum(II) complexes containing pyridine-2-thiolate as a ligand. Crystal structure of chloro(pyridine-2-thiolato)- (triphenylphosphine)palladium(II)

Various types of mononuclear pyridine-2-thiolato (pyS) complexes [M(pyS) 2(PPh 3) 2], [MCl(pyS)(PPh 3)], [M(pyS) 2(PPh 3)] (M=Pd(II), Pt(II)) and [PdCl(pyS)(PPh 3) 2]·CH 2Cl 2, and the complex of pyridine-2-thiol [PdCl 2(pySH)(PPh 3)] have been prepared. The solution behavior of these complexes has been examined by 1H and 31P{ 1H} NMR measurements as well as the determination of the molecular weights. The coordination modes of the pyS ligand in the complexes, including chelation, S-unidentate, and the fast exchange between them, have been elucidated. The crystal structure of [PdCl(pyS)(PPh 3)] has been determined. The complex crystallizes in the triclinic space group P1, Z=2, a=12.969(6), b=10.246(5), c=9.493(3) Å, α=114.53(3), β=72.57(3), γ=105.71(3)°. The structure has been determined using conventional heavy atom methods, final R w=0.067 based on 2546 significant ( I>;3σ( I)) reflections. The Pd atom is four-coordinated by the Cl, P, S and N donor atoms, constituting a square-planar, trans-(P,N) structure; the pyS ligand is chelated with a small bite angle. In the crystals, there are two independent molecules, the structures of which differ from one another in the disposition of the pyridine ring folded in opposite directions on the plane defined by the Pd, Cl, P and S atoms.

Influence of ligands and anions on the insertion of alkenes into palladium-acyl and palladium-carbomethoxy bonds in the neutral complex (dppp)Pd(C(O)CH 3)Cl and the ionic complexes [(PP)PdR(L)] +SO 3CF 3− (PP = dppe, dppp, dppb; R  C(O)CH 3, L  CH 3CN, PPh 3; R  C(O)OCH 3, L  PPh 3)

Insertions of alkenes in Pd-acetyl bonds of (dppp)Pd(C(O)CH 3)Cl and [(PP)Pd(C(O)CH 3)L)] + SO 3CF 3 − (PP = dppe, dppp, dppb; L  CH 3CN, PPh 3) have been studied as a function of the ligand, the anion and the alkene. The neutral acetyl complex (dppp)Pd(C(O)CH 3)Cl underwent insertion only with norbornadiene and norbornene, while the ionic acetyl complexes [(PP)Pd(C(O)CH 3)(L)] + SO 3CF 3 − (PP = dppe, dppp, dppb) reacted with norbornadiene, norbornene, styrene, cis-stilbene, 1-pentene, 3,3-dimethyl-1-butene, vinyltrimethylsilane, methyl vinyl ketone, methyl acrylate, diethyl fumarate, and diethyl maleate. The insertion was observed to give an intermediate in which there was intramolecular coordination of the ketone oxygen atom to the palladium centre. In monosubstituted alkenes the acetyl group migrates to the unsubstituted carbon atom. The insertion products underwent β-elimination to give ( trans) unsaturated ketones and a palladium hydride. The rate of this elimination was higher for complexes containing ligands LL with smaller bite angles (dppe > dppp), and the rate of insertion showed the reverse order. The carbomethoxy complexes [(PP)Pd(C(O)OCH 3)(PPh 3)] + SO 3CF 3 − (PP = dppe, dppp, dppb) were prepared from (PP)Pd(SO 3CF 3) 2 with CO, CH 3OH and PPh 3. The carbomethoxy complex reacted with norbornadiene to give a carbomethoxy oxgyen-coordinated intermediate. The carbomethoxy complexes were less reactive than the analogous acetyl complexes towards alkenes.

Triply bridged (O,O′,S)-binuclear oxomolybdenum(V) complexes containing o-mercaptophenol ligands

Complexes [A][Mo 2O 2(μ-O)mp 3Na(EtOH) 3] (A = Et 4N (1a); A = nBu 4N (1b)) and (n-Bu 4N) [Mo 2O 2(μ-OEt)mp 3] (2) have been obtained by the reaction of MoOCl 3(THF) 2 and Na 2mp (H 2mp = o-mercaptophenol) in appropriate solvents. Both (1b) and (2) crystallize in monoclinic space group P2 1/n. Cell parameters for (1b): a = 12.776(3), b = 14.154(5), c = 26.281(7) Å, β = 95.50(2)°, V = 4730.5 Å 3, Z = 4, D calc = 1.427 g/cm 3; for (2): a = 12.617(5), b = 23.817(18), c = 14.228(7) Å, β = 105.79(4)°, V = 4114.1 Å 3, Z = 4, D calc = 1.427 g/cm 3. The structures were solved by direct methods from 3348 (1b) or 1583 (2) unique reflections with I > 3σ (I) to final convergence factors of R(R w) 0.070(0.070) for (1b) and 0.090(0.099) for (2). The two [Mo(O)mp] + units are triply bridged by one doubly bridging mp 2− ligand with exceedingly small bite angles (68.85°) and bite distances (2.70 Å) and an inorganic oxygen atom for (1b) or an ethoxy group for (2). The molybdenum(V) atoms are in an environment of O 4S 2, forming a distorted octahedron with the terminal oxo groups cis to each other. Information concerning the possible origin of oxygen atoms in MoFepr is derived from the structural data of these two complexes. 1H NMR and CV measurements were also studied.

Synthesis and characterization of 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (L) derivatives of mononuclear manganese(I) and Group 6 metal(0) carbonyl complexes. Crystal and molecular structures of [M(CO)4L](M = Cr or Mo)

Treatment of [M(CO)6](M = Cr, Mo or W) or [MnBr(CO)5] with 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (L) in refluxing tetrahydrofuran or toluene (M = Cr or W) gives, respectively, [M(CO)4L] and [MnBr(CO)3L]. Infrared and 1H NMR spectra indicate that the tetradentate heterocycle acts only as a monochelate ligand forming mononuclear complexes. The crystal structures of [M(CO)4L](M = Cr or Mo) have been determined by X-ray diffraction. Crystals are isotypic, monoclinic, space group P21/c, with Z= 4 in unit cells of dimensions a= 8.0790(1), b= 19.5539(2), c= 12.5186(1)A, β= 91.598(1)°(M = Cr) and a= 8.081(1), b= 19.793(2), c= 12.607(6)A, β= 91.62(3)°(M = Mo). The structures have been solved by Patterson methods and DIRDIF. Final conventional agreement factors were R= 0.043, R′= 0.038 for M = Cr and R= 0.051, R′= 0.038 for M = Mo. The structures consist of distorted octahedral arrangements with four carbonyl groups and two nitrogen atoms of the ligand L around each metal atom, and the unco-ordinated nitrogen atom of the pyrazolyl group twisted by almost 180° with respect to the corresponding one in the co-ordinated ring. The ligand, which is almost planar, forms a monochelate ring with small bite angles N–M–N 75.2(1) and 71.0(3)° for Cr and Mo respectively. Deviation from the linearity of the mutually trans-carbonyl groups is revealed by the C–M–C bond angles of 166.7(2)(M = Cr) and 167.0(6)°(M = Mo) with slighter distortions of the mutually cis-carbonyl groups [range 84(1)–87(1)°]. Cyclic voltammetric studies in CH2Cl2 show single non-reversible redox waves in accord with the observed energies of the metal-to-ligand charge transfer absorptions in the electronic spectra.

Electronic structure of a heterotetranuclear Cu 12Fe II2 complex bridged by π-accepting 2,2′-bipyrimidine. Close-lying but orthogonal frontier orbitals

The new complex 1 contains two 1,1′-bis(diphenylphosphino)ferrocene-coordinated copper(I) centers which are connected by the D 2 h -symmetric π acceptor 2,2′-bipyrimidine. Cyclic voltammetry and ESR reveal a ferrocene-based HOMO and a bpym-centered LUMO. There is no detectable HOMO/LUMO absorption band because of orthogonality between the two types of orbitals. The lack of strong solid-state MLCT luminescence is an indirect consequence of the small bite angle of the bis(diphenylphosphino)ferrocene ligand, which cannot induce strong distortion at the copper center.

An oxo-bridged binuclear vanadium(III) 2,2'-bipyridine complex and its vanadium(IV) and vanadium(V) oxidation products

Vanadium(III) in water reacts with 2,2′-bipyridine to form an oxo-bridged binuclear complex that crystallizes as [{VCl-(bpy)]O],Cl·3HO in the orthorhombic space group Pbcn with unit cell dimensions a = 18.820 (8) A, b = 9.507 (2) A, c = 25.792 (6) A, V = 4614.8 A, and Z = 8. The complex in its crystalline form has a magnetic moment per vanadium of 3.176 ± 0.002 µ, an unusually high value, considering all available evidence supports the III oxidation state. Aerial oxidation yields an oxovanadium(IV) complex that crystallizes from an aqueous acetone perchlorate solution as [VOCl(bpy)]ClOin the monoclinic space group P2/c with a = 12.960 (3) A, b = 12.310 (4) A, c = 13.642 (3) A, β = 105.78 (2)°, V = 2094.4 A, and Z = 4. Further oxidation in aqueous tetrahydrofuran produces crystals of [VO(bpy)]Cl·4HO with the triclinic space group Pl with a = 1 1.527 (5) A, b = 15.102 (5) A, c = 6.738 (3) A, ± = 97.33 (4)A, ² = 97.26 (4)°, γ = 101.31 (3)°, V= 1126.9 A, and Z = 2. The structures of the first and third complexes were refined by a full-matrix least-squares procedure, and a blocked-matrix procedure was employed for the refinement of the vanadyl complex. Refinement on 2364 statistically significant reflections yielded final R = 0.063 and R= 0.071 for the oxo-bridged complex; on 2402 reflections, R = 0.065 and R= 0.071 for the vanadyl complex; and on 2212 reflections, R = 0.076 and R= 0.084 for the dioxovanadium(V) complex. The coordination geometries show similar distortions from a regular octahedral structure dictated by repulsions between the two anionic ligands, the small bite angle of the chelates, and the effects of trans ligands on the coordinate bond lengths. The binuclear complex has a Caxis relating the two units, which are twisted 61.6° relative to each other. The V-O-V group is close to linear with a bond angle of 173.5 (4)°.

Synthese und Kristallstruktur des Amidinatokomplexes Ph-C(NSiMe3)2TeCl3 / Synthesis and Crystal Structure of the Amidinato Complex Ph —C(NSiMe3)2TeCl3

Abstract The title com pound has been prepared by the reaction o f N ,N ,N '-tris(trimethylsilyl)-benzamidine with tellurium tetrachloride in CH2Cl2 solution. The complex was characterized by an X-ray structure determination. Crystal data: space group P 1̄ , Z = 2, (2428 observed independent reflexions, R = 0.031). Lattice dimensions (19 °C): a = 946.7(1), b = 1031.5(1), c = 1337.1(1) pm; α = 67.411(8)°, β = 68.508(9)°, γ = 67.195(8)°. Ph-C(NSiMe3)2TeCl3 forms monomeric molecules, in which the tellurium atom is ϕ-octahedrally surrounded by three chlorine atoms and by the two nitrogen atoms of the amidinato chelate (bond lengths Te -N = 209.6 and 219.2 pm). The lone pair at the tellurium (IV) center and the small bite angle of the ligand cause a strong distortion of the octahedral geometry.

Molybdenum tricarbonyl complexes of tricyclic trisaminomethane derivatives; synthesis and structural studies

Reactions of the trisaminomethanes, 1 (R = H) and 2 (R = Me), with cycloheptatrienyl molybdenum tricarbonyl afforded their respective molybdenum tricarbonyl complexes; 3 and 4. Structures of these products have been determined by X-ray diffraction studies. Complex 3 crystallizes in the monoclinic space group P2 1/ m with a = 7.7364(6), b = 12.505(1), c = 7.774(1) Å, β = 107.70(1)°, Z = 2, μ(Mo- K α) = 0.90 mm −1. Its molybdenum coordination sphere features unusually small ligand bite angles (NMoN) of 57.7(1)–58.0(1)°. The unique bridgehead methinyl hydrogen was not located, but its existence has been confirmed by IR and solid-state NMR spectroscopy. Complex 4 crystallizes in the orthorhombic space group Pcmn with a = 7.7537(2), b = 12.3176(4), c = 15.6563(7) Å, Z = 4, μ(Mo- K α) = 0.87 mm −1. Similarly, pinched NMON angles of 58.8(1)° are observed. Significantly, the methyl to bridgehead carbon bond is shortened by 0.04 Å relative to the free ligand value, consistent with a reduced negative hyperconjugation upon complexation.

Convenient synthesis, properties and the structure of tetramethylammonium tris(pyrimidine-2-thiolato)ferrate(II): an iron complex with three stable four-membered N,S-chelate rings

Reaction of iron(II) chloride with sodium pyrimidine-2-thiolate in ethanol or methanol followed by addition of R 4NBr affords (R 4N)[Fe(SC 4H 3N 2) 3] (R = Me, Et) in high yields. (Me 4N)[Fe(SC 4H 3N 2) 3] crystallizes in the triclinic space group P 1 with a = 7.163(2), b = 10.002(3), c = 15.456(3) Å, α = 103.23(1)°, β = 91.25(1)°, γ = 92.09(1)° and Z = 2. The structure was refined to R = 2.9% on the basis of 5663 unique data ( F o 2>2.5σ( F o 2)). The octahedral geometry about iron is highly distorted due to the presence of three four-membered chelate rings with an exceptionally small bite angle of ca. 67°. Average FeN and FeS distance are 2.163 and 2.529 Å respectively. The complex is isolated as the mer isomer. Mössbauer studies in polycrystalline state together with UVVis and magnetic susceptibility measurement in acetonitrile solution demonstrate that the iron is in +2 oxidation state with a high-spin electronic configuration.

PH-Functional Methylenebisphosphanes RR′P-CH2-PRH (R′= R, H) - Reactive Bridging Ligands with A Small Bite Angle

Abstract PH-functional methylenbisphosphanes RR′P-CH2-PRH (R′=R, H) are versatile ligands in coordination chemistry. They may oxidatively add with their PH-bonds to transition metals in low oxidation numbers and form cluster compounds with P-C-P-bridges. P-C-P-bond cleavage reactions afford phosphinidenes ⟨PR⟩(through a formal 1,2-hydrogen shift from phosphorus to the CH2-group, RR′P-CH2-PRH → RR′P-CH3 + ⟨PR⟩) which are incorporated into the oligometallic cluster framework formed.

Synthesis and characterisation of [Ag 2Pt 4(μ-S) 4(PPh 3) 8](BF 4) 2 · 0.25CHCl 3

[Pt 2(μ 2-S) 2(PPh 3) 4] functions effectively as a bridging bidentate ligand towards Ag + to form [Ag 2Pt 4(μ 3-S) 4(PPh 3) 8] 2+. A single crystal X-ray crystallographic anaylsis of the BF 4 − salt has demonstrated that both Ag + ions are linearly coordinated to the sulphur atoms, but the small bite angle of the [Pt 2(μ-S) 2(PPh 3) 4] ligand leads to an Ag…Ag contact distance of only 2.815(4) Å.