Axial Chloride Research Articles

Theoretical and experimental studies of phenol oxidation by ruthenium complex with N,N,N-tris(benzimidazol-2yl-methyl)amine.

The ruthenium complex with (N,N,N-tris(benzimidazol-2yl-methyl)amine, L(1)) was prepared, and characterized. Fukui data were used to localize the reactive sites on the ligand. The structural and electronic properties of the complex were analyzed by DFT in different oxidation states in order to evaluate its oxidant properties for phenol oxidation. The results show that the hard Ru(IV) cation bonds preferentially with a hard base (Namine = amine nitrogen, or axial chloride ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole nitrogen or axial triphenyl phosphine). Furthermore, the Jahn-Teller effect causes an elongation of the axial bond in the octahedral structure. The bonding nature and the orbital contribution to the electronic transitions of the complex were studied. The experimental UV-visible bands were interpreted by using TD-DFT studies. The complex oxidizes phenol to benzoquinone in the presence of H2O2 and the intermediate was detected by HPLC and (13)C NMR. A possible mechanism and rate law are proposed for the oxidation. The adduct formation of phenol with [Ru(O)L(1)](2+) or [Ru(OH)L(1)](+) is theoretically analyzed to show that [Ru(OH)L(1)-OPh](+) could produce the phenol radical.

Structural study of a manganese(II) 'picket-fence' porphyrin complex.

'Picket-fence' porphyrin compounds are used in the investigation of interactions of hemes with dioxygen, carbon monoxide, nitric monoxide and imidazole ligands. (Cryptand-222)potassium chlorido[meso-tetra(α,α,α,α-o-pivalamidophenyl)porphyrinato]manganese tetrahydrofuran monosolvate (cryptand-222 is 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane), [K(C18H36N2O6)][Mn(C64H64N8O4)Cl]·C4H8O or [K(222)][Mn(TpivPP)Cl]·THF [systematic name for TpivPP: 5,10,15,20-tetrakis(2-tert-butanamidophenyl)porphyrin], is a five-coordinate high-spin manganese(II) picket-fence porphyrin complex. It crystallizes with a potassium cation chelated inside a cryptand-222 molecule; the average K-O and K-N distances are 2.83 (4) and 2.995 (13) Å, respectively. All four protecting tert-butyl pickets of the porphyrin are ordered. The porphyrin plane is nearly planar, as indicated by the atomic displacements and the dihedral angles between the mean planes of the pyrrole rings and the 24-atom mean plane. The axial chloride ligand is located inside the molecular cavity on the hindered porphyrin side and the Mn-Cl bond is tilted slightly off the normal to the porphyrin plane by 3.68 (2)°. The out-of-plane displacement of the metal centre relative to the 24-atom mean plane (Δ24) is 0.7013 (4) Å, indicating a noticeable porphyrin core doming.

Ambient Stable Trigonal Bipyramidal Copper(III) Complexes Equipped with an Exchangeable Axial Ligand.

A stable trigonal bipyramidal copper(III) complex, [PPN][Cu((TMS)PS3)Cl] (1, wherein PPN represents bis(triphenylphosphine)iminium), was synthesized from CuCl2/PPNCl via intramolecular copper(II) disproportionation. Under ambient conditions, the axial chloride of 1 is exchangeable in solution thus making 1 serve as an intermediate to prepare trigonal bipyramidal copper(III) derivatives, e.g., [PPN][Cu((TMS)PS3)(N3)] (2) and [Cu((TMS)PS3)(DABCO)] (3). Diamagnetic complexes 1-3 were fully characterized by X-ray crystallography, NMR, UV-vis, and Cu K-edge absorption spectroscopy. A series of UV-vis titrations were performed to investigate the relative ligand affinity toward the [Cu((TMS)PS3)] moiety, verifying the 1:1 binding equilibrium between various ligands. Compared to known copper(III) compounds, Cu K-edge absorptions of 1-3 possess lower pre-edge energy and higher shakedown transition energy, which, respectively, attribute to the electron donation from (TMS)PS3(3-) ligand and their trigonal ligand field.

Crystal structure of tetra-kis-(μ-n-butyrato-κ(2) O:O')bis-[chlorido-rhenium(III)](Re-Re).

With an inversion center at the mid-point of the two ReIII atoms, the title compound, [Re2Cl2{O2C(CH2)2CH3}4], exhibits a paddle-wheel or lantern-type structure with four n-butyrate groups bridging two ReIII atoms in a syn–syn fashion. The axial chloride ligands together with the Re—Re quadruple bond [2.2330 (3) Å] complete an essentially octa­hedral geometry around each ReIII atom. There is little distortion, with an Re—Re—Cl bond angle of 176.18 (3)° and typical cis-O—Re—O bond angles ranging from 89.39 (11) to 90.68 (11)°. There are two mol­ecules in the unit cell, and no significant inter­molecular inter­actions were noticed between mol­ecules in the crystal.

Chlorido(2,3,7,8,12,13,17,18-octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl

The previous structure determination of the title compound, [Fe(C36H44N4)Cl], was of a monoclinic polymorph [Senge (2005). Acta Cryst. E61, m399-m400]. The crystal structure of a new triclinic polymorph has been determined based on single-crystal X-ray diffraction data collected at 100 K. The asymmetric unit contains one molecule of the high-spin square-pyramidal iron(III) porphyrinate. The structure exhibits distinct nonstatistical alternative positions for most atoms and was consequently modeled as a whole-molecule disorder. The compound is characterized by an average Fe-N bond length of 2.065 (2) Å, an Fe-Cl bond length of 2.225 (4) Å, and the iron(III) cation displaced by 0.494 (4) Å from the plane of the 24-atom porphyrinate core, essentially the same as in the previously determined polymorph. Common features of the porphyrin plane-plane stacking involve two types of synthons, each of which can be further stabilized with additional H···Cl interactions to the axial chloride ligand, exhibiting concerted interactions of H atoms from the ethyl groups with the π-cloud electron density of adjacent molecules; the shortest methylene H-atom contacts are in the range 2.75-2.91 Å, resulting in plane-plane separations of 3.407 (4) and 3.416 (4) Å, and the shortest methyl H-atom contacts are 2.56-2.95 Å, resulting in plane-plane separations of 4.900 (5) and 4.909 (5) Å in the monoclinic polymorph. The plane-to-plane stacking synthons in the triclinic polymorph are similar, but at greater distances; the shortest methylene H-atom contacts are 2.86-2.94 Å, resulting in plane-plane separations of 3.45 (2) and 3.45 (3) Å, and the shortest methyl H-atom contacts are 2.89-3.20 Å, resulting in plane-plane separations of 5.081 (13) and 5.134 (13) Å, consistent with the density of the triclinic polymorph being 1.5% lower, suggesting lesser packing efficiency and lower stability in the triclinic polymorph. The major molecular differences found in the polymorphs is in three different orientations of the ethyl-group side chains on the periphery of the porphyrin core.

Visible Light-Driven Hydrogen Evolution from Water Catalyzed by A Molecular Cobalt Complex

An approximately planar tetradentate polypyridine ligand, 8-(1″,10″-phenanthrol-2″-yl)-2-(pyrid-2'-yl)quinoline (ppq), has been prepared by two sequential Friedländer condensations. The ligand readily accommodates Co(II) bearing two axial chlorides, and the resulting complex is reasonably soluble in water. In DMF the complex shows three well-behaved redox waves in the window of 0 to -1.4 V (vs SHE). However in pH 7 buffer the third wave is obscured by a catalytic current at -0.95 V, indicating hydrogen production that appears to involve a proton-coupled electron-transfer event. The complex [Co(ppq)Cl2] (6) in pH 4 aqueous solution, together with [Ru(bpy)3]Cl2 and ascorbic acid as a sacrificial electron donor, in the presence of blue light (λmax = 469 nm) produces hydrogen with an initial TOF = 586 h(-1).

Anion and Solvent Induced Chirality Inversion in Macrocyclic Lanthanide Complexes

A series of the lanthanide(III) or yttrium(III) complexes of the type [LnL(NO3)(H2O)2](NO3)2, [LnL(NO3)(H2O)](NO3)2, [LnL(H2O)2](NO3)3, and [LnLCl(H2O)2]Cl2 where L is an all-R or all-S enantiomer (L(R) or L(S)) of the chiral hexaaza macrocycle, 2(R),7(R),18(R),23(R)- or 2(S),7(S),18(S),23(S)-1,8,15,17,24,31-hexaazatricyclo[25.3.1.1.0.0]-dotriaconta-10,12,14,26,28,30-hexaene, and Ln(III) = Sm(III), Tb(III), Ho(III), Er(III), Tm(III), Yb(III), Lu(III), or Y(III), have been synthesized and structurally characterized. The crystal structure of the free macrocycle shows a highly twisted molecule, preorganized for the formation of helical complexes. The crystal structures of the lanthanide(III) complexes show two different diastereomeric forms of the macrocycle with different configurations at the stereogenic amine nitrogen atoms: (RRRR) or (RSRS) (denoted as L(RI) and L(RII), respectively). The L(RI) diastereomeric form of the nitrate derivatives [LnL(NO3)(H2O)](NO3)2 (Ln = Ho, Er) and [LnL(H2O)2](NO3)3 (Ln = Tm, Yb, Lu) convert slowly to the L(RII) form in methanol or acetonitrile solutions, while this process is not observed for the L(RI) diastereomers of analogous chloride derivatives [LnL(H2O)2]Cl3 (Ln = Tm, Yb, Lu). On the other hand, the L(RI) → L(RII) conversion for these Tm(III), Yb(III), and Lu(III) chloride derivatives can be triggered by the addition of external nitrate anions. The circular dichroism (CD) and (1)H NMR data indicate initial fast exchange of axial chloride for axial nitrate ligand, followed by slow chirality inversion of the equatorial macrocyclic ligand.

2-[(Diphenylphosphino)methyl]-6-methylpyridine (PN) coordination chemistry at triosmium clusters: Regiospecific ligand activation and DFT evaluation of the isomeric Os3(CO)10(PN) clusters

The reaction of 2-[(diphenylphosphino)methyl]-6-methylpyridine (PN) with Os3(CO)12−n(MeCN)n [where n = 0 (1), 1 (2), 2 (3)] has been investigated. Os3(CO)12 reacts with PN in the presence of Me3NO to afford the clusters Os3(CO)11(κ1-PN) (4) and 1,2-Os3(CO)10(κ1-PN)2 (5). X-ray diffraction analyses confirm the equatorial coordination of the phosphine(s) in 4 and 5, with the two phosphines in the latter cluster exhibiting a 1,2-trans orientation about the Os–Os vector that contains the two ligands. Treatment of the MeCN-substituted cluster Os3(CO)11(MeCN) and PN (1:1 ratio) in CH2Cl2 gives clusters 4 and 5, in addition to HOs3(η1-Cl)(CO)10(κ1-PN) (6) as a result of competitive activation of the reaction solvent. Cluster 6 contains 48e and the diffraction structure reveals the presence of axial chloride and equatorial phosphine ligands which are located on adjacent osmium atoms. The bridging hydride ligand in 6 spans the Cl,P-substituted Os–Os vector. The reaction of Os3(CO)10(MeCN)2 with PN furnishes 5, 6, and 1,1-Os3(CO)10(κ2-PN) (7) in yields that are dependent on the reagent stoichiometry and reaction solvent. The solid-state structure of 7 confirms the chelation of the PN ligand to a single osmium atom via the pyridine and phosphine moieties at axial and equatorial sites, respectively. The bonding in 7 relative to other possible stereoisomers has been explored by DFT calculations, and the diffraction structure is computed as the thermodynamically most stable form of this cluster. Cluster 4 is photosensitive and CO loss gives 7, in addition to the formation of the dihydride H2Os3(CO)8[μ-CH(NC5H3)CH2PPh2] (8), whose origin derives from the double metalation of the C-6 methyl group of the PN ligand in 7. Photolysis of 7 yields 8 without detectable observation of the expected intermediate hydride HOs3(CO)9[μ-CH2(NC5H3)CH2PPh2]. The PN ligand in 7 undergoes P–C bond activation in toluene at 110 °C to afford the 50e cluster Os3(CO)9(μ-C6H4)(μ-PPh) (9), which contains face-capping benzyne and phosphinidene moieties. The bonding between the benzyne moiety and the opened Os3 frame in 9 has been examined computationally, and these data are discussed relative to σ and π bonding contributions from the metalated aryl ring to the cluster polyhedron.

Hydrothermal synthesis and solid-state structure of Tc2(μ-O2CCH3)4Cl2

Tc2(μ-O2CCH3)4Cl2 is a key starting material for further explorations of dinuclear technetium(III) chemistry and is obtained in 70% yield from readily available starting materials via hydrothermal techniques. Its single crystal X-ray structure reveals the familiar paddle-wheel motif of four bridging acetate groups spanning a short Tc–Tc bond (2.1758(3)Å), augmented by axial chlorides at a Tc–Cl separation of 2.5078(4)Å. The Tc–Tc quadruple bond length is slightly shorter than the one found in the pivalate derivative, Tc2(O2CCMe3)4Cl2 (2.192(1)Å), and slightly longer than found in [Tc2(O2CCH3)4](TcO4)2 (2.149(1)Å), the only other structurally characterized members of the small family of Tc2(O2CR)4X2 dimers.

Systematic differences in electrochemical reduction of the structurally characterized anti-cancer platinum(IV) complexes [Pt{((p-HC6F4)NCH2)2}-(pyridine)2Cl2], [Pt{((p-HC6F4)NCH2)2}(pyridine)2(OH)2], and [Pt{((p-HC6F4)NCH2)2}(pyridine)2(OH)Cl

The putative platinum(IV) anticancer drugs, [Pt{((R)NCH2)2}(py)2XY] (X,Y=Cl, R=p-HC6F4 (1a), C6F5 (1b); X,Y=OH, R=p-HC6F4 (2); X=Cl, Y=OH, R=p-HC6F4 (3), py = pyridine) have been prepared by oxidation of the PtII anticancer drugs [Pt{((R)NCH2)2}(py)2] (R=p-HC6F4 (4a) or C6F5 (4b)) with PhICl2 (1a,b), H2O2 (2) and PhICl2/Bu4NOH (3). NMR spectroscopy and the X-ray crystal structures of 1b, 2 and 3 show that they have octahedral stereochemistry with the X,Y ligands in the trans-position. The net two electron electrochemical reduction of 1a, 2 and 3 has been studied by voltammetric, spectroelectrochemical and bulk electrolysis techniques in acetonitrile. NMR and other data reveal that reduction of 1a gives pure 4a via the elimination of both axial chloride ligands. In the case of 2, one end of the diamide ligand is protonated and the resulting –NH(p-HC6F4) group dissociated giving a [Pt{N(p-HC6F4)CH2CH2NH(p-HC6F4)}] arrangement, one pyridine ligand is lost and a hydroxide ion retained in the coordination sphere. Intriguingly, in the case of reduction of 3, a 50% mixture of the reduction products of pure 1a and 2 is formed. The relative ease of reduction is 1>3>2. Testing of 1a, 2 and 3 against L1210 and L1210(DDP) (DDP = cis-diamine-dichloroplatinum(II)) mouse leukaemia cells shows all to be cytotoxic with IC50 values of 1.0–3.5μM. 2 and 3 are active in vivo against AHDJ/PC6 tumor line when delivered in peanut oil despite being hard to reduce electrochemically, and notably are more active than 4a delivered in this medium whilst comparable with 4a delivered in saline/Tween.

Control of the axial coordination of a surface-confined manganese(III) porphyrin complex

The organization and thermal lability of chloro(5,10,15,20-tetraphenylporphyrinato)manganese(III) (Cl-MnTPP) molecules on the Ag(111) surface have been investigated under ultra-high vacuum conditions, using scanning tunnelling microscopy, low energy electron diffraction and x-ray photoelectron spectroscopy. The findings reveal the epitaxial nature of the molecule–substrate interface, and moreover, offer a valuable insight into the latent coordination properties of surface-confined metalloporphyrins. The Cl-MnTPP molecules are found to self-assemble on the Ag(111) surface at room temperature, forming an ordered molecular overlayer described by a square unit cell. In accordance with the threefold symmetry of the Ag(111) surface, three rotationally equivalent domains of the molecular overlayer are observed. The primitive lattice vectors of the Cl-MnTPP overlayer show an azimuthal rotation of ±15° relative to those of the Ag(111) surface, while the principal molecular axes of the individual molecules are found to be aligned with the substrate and crystallographic directions. The axial chloride (Cl) ligand is found to be orientated away from the Ag(111) surface, whereby the average plane of the porphyrin macrocycle lies parallel to that of the substrate. When adsorbed on the Ag(111) surface, the Cl-MnTPP molecules display a latent thermal lability resulting in the dissociation of the axial Cl ligand at ∼423 K. The thermally induced dissociation of the Cl ligand leaves the porphyrin complex otherwise intact, giving rise to the coordinatively unsaturated Mn(III) derivative. Consistent with the surface conformation of the Cl-MnTPP precursor, the resulting (5,10,15,20-tetraphenylporphyrinato)manganese(III) (MnTPP) molecules display the same lattice structure and registry with the Ag(111) surface.

Numerical analysis on optical limiting performance of a series of phthalocyanines for nanosecond pulses

The optical limiting properties of a series of peripherally substituted phthalocyanines with different central metals and axial chloride ligand for nanosecond pulses have been studied by solving numerically the two-dimensional paraxial field equation together with the rate equations using the Crank–Nicholson method. It is shown that all of these compounds exhibit good optical limiting behaviour, and phthalocyanines with heavier central metals have better optical limiting performance due to the faster intersystem crossing caused by the enhanced spin–orbit coupling. The major mechanism of optical limiting for long pulses is the sequential (singlet–singlet)×(triplet–triplet) nonlinear absorption. Dynamics of populations is characterized mainly by the effective transfer time of the population from the ground state to the lowest triplet state. The long lifetime of the triplet state is important but not determinant. In addition, the performance of optical limiting strongly depends on the thickness and concentration of the absorber.

Trans-[RuII(dpp)Cl2]: A Convenient Reagent for the Preparation of Heteroleptic Ru(dpp) Complexes, Where dpp Is 2,9-Di(pyrid-2′-yl)-1,10-phenanthroline

The reaction of 2,9-di(pyrid-2'-yl)-1,10-phenanthroline (dpp) with [RuCl(3)·3H(2)O] or [Ru(DMSO)(4)Cl(2)] provides the reagent trans-[Ru(II)(dpp)Cl(2)] in yields of 98 and 89%, respectively. This reagent reacts with monodentate ligands L to replace the two axial chlorides, affording reasonable yields of a ruthenium(II) complex with dpp bound tetradentate in the equatorial plane. The photophysical and electrochemical properties of the tetradentate complexes are strongly influenced by the axial ligands with electron-donating character to stabilize the ruthenium(III) state, shifting the metal-to-ligand charge-transfer absorption to lower energy and decreasing the oxidation potential. When the precursor trans-[Ru(II)(dpp)Cl(2)] reacts with a bidentate (2,2'-bipyridine), tridentate (2,2';6,2''-terpyridine), or tetradentate (itself) ligand, a peripheral pyridine on dpp is displaced such that dpp binds as a tridentate. This situation is illustrated by an X-ray analysis of [Ru(dpp)(bpy)Cl](PF(6)).

Synthesis, structure, and physical properties for a series of trigonal bipyramidal M(II)-Cl complexes with intramolecular hydrogen bonds.

A series of transition metal chloro complexes with the tetradentate tripodal tris(2-amino-oxazoline)amine ligand (TAO) have been synthesized and characterized. X-Ray structural analyses of these compounds demonstrate the formation of the mononuclear complexes [M(II)(TAO)(Cl)](+), where M(II) = Cr, Mn, Fe, Co, Ni, Cu and Zn. These complexes exhibit distorted trigonal-bipyramidal geometry, coordinating the metal through an apical tertiary amine, three equatorial imino nitrogen atoms, and an axial chloride anion. All the complexes possess an intramolecular hydrogen-bonding (H-bonding) network within the cavity occupied by the metal-bound chloride ion. The metal-chloride bond distances are atypically long, which is attributed to the effects of the H-bonding network. Nuclear magnetic resonance (NMR) spectroscopy of the Zn complex suggests that the solid-state structures are representative of that observed in solution, and that the H-bonding interactions persist as well. Additionally, density functional theory (DFT) calculations were carried out to probe the electronic structures of the complexes.

Substituent effects on geometric and electronic properties of iron tetraphenylporphyrin: a DFT investigation

To investigate the effects of the substituents, substituent positions and axial chloride ligand on the geometric and electronic properties of the iron tetraphenylporphyrin (FeTPP), a series of the substituented iron tetraphenylporphyrins and their chlorides, FeT(o/p-R)PP and FeT(o/p-R)PPCl (R = -H, -Cl, -NO(2), -OH, -OCH(3)), were systematically calculated without any symmetry constraint by using DFT method. For geometric structure, the substituent position and axial Cl ligand change the configuration of the iron porphyrin obviously. The ortho-substituents prefer making the phenyls perpendicular to the porphyrin ring; the axial chloride draws the central Fe ion ~0.500 Å out of the porphyrin plane toward the ligand. With regard to electronic properties, it is found that E(LUMO) could be related to the catalytic activity. The electron-withdrawing group always lowers the energies of both frontier orbitals, while the electron-donating one heightens them simultaneously, but they affect the E(HOMO) and E(LUMO) in the same sequence, -NO(2) < -Cl < -H < -OH < -OCH(3). The substituent effects on the central Fe ion were explored by calculating NBO charge distribution, spin density and natural electron configuration.

The synthesis, photophysical and thermal properties of novel 7-hydroxy-4-methylcoumarin tetrasubstituted metallophthalocyanines with axial chloride ligand

This work reports the synthesis of 7-hydroxy-4-methylcoumarin tetrasubstituted Ruthenium (III)( 4a), Indium (III)( 4b), Tin (IV)( 4c) phthalocyanines bearing axial chloride ligand for the first time. These new metallophthalocyanines show good solubility in many organic solvents. This study also investigates the photophysical (fluorescence quantum yield and lifetime) properties of compounds 4a, 4b and 4c. The fluorescence of these three metallophthalocyanines is effectively quenched by the addition of 1,4-benzoquinone (BQ). The thermal stability studies indicate that both 4a and 4b are stable up to 300 °C.

Factors That Regulate the Conformation of m‐Benziporphodimethene Complexes: Agostic Metal–Arene Interaction, Hydrogen Bonding, and η2,π Coordination

Group 12 and silver(I) tetramethyl-m-benziporphodimethene (TMBPDM) complexes with phenyl, methylbenzoate, or nitrophenyl groups as meso substituents were synthesized and fully characterized. The dimeric silver(I) complex displays an unusual η(2),π coordination from the β-pyrrolic C=C bond to the silver ion. All of the complexes displayed a close contact between the metal ion and the inner C(22)-H(22) on the m-phenylene ring. The downfield chemical shifts of H(22) and large coupling constants between Cd(II) and H(22) strongly support the presence of an agostic interaction between the metal ion and inner C(22)-H(22). Crystal structures revealed that the syn form is the predominant conformation for TMBPDM complexes. This is distinctively different from the exclusive anti conformation observed in m-benziporphyrin and tetraphenyl-m-benziporphodimethene (TPBPDM) complexes. Evidently, intramolecular hydrogen-bonding interactions between axial chloride and methyl groups stabilize syn conformations. Unlike the merely syn conformation observed in the solid-state structures of TMBPDM complexes that contain an axial chloride, in solution these complexes display highly solvent- and temperature-dependent syn/anti ratio changes. The observation of dynamic (1)H NMR spectroscopic scrambling between syn and anti conformations from the titration of chloride ion into the solution of the TMBPDM complex suggests that axial ligand exchange is a likely pathway for the conversion between syn and anti forms. Theoretical calculations revealed that intermolecular hydrogen-bonding interactions between the axial chloride and CHCl(3) stabilizes the anti conformation, which explains the increased ratio for the anti form when dichloromethane or chloroform was used as the solvent.

XAFS studies of Ni, Ta, and Nb chlorides in the ionic liquid 1-ethyl-3-methyl imidazolium chloride/aluminum chloride

The structures of anhydrous nickel, niobium, and tantalum chlorides have been investigated in situ in acidic and basic ionic liquids (ILs) of 1-methyl-3-ethylimidazolium chloride (EMIC)/AlCl3 with X-ray absorption spectroscopy (XAS). The coordination of NiCl2 changes from tetrahedral in basic solution to octahedral in acidic solution. The NiCl2 is a strong Lewis acid in that it can induce the AlCl3 to share its chlorides in the highly acidic IL, forming a structure with six near Cl− ions and eight further distant Al ions which share the chloride ions surrounding the Ni2+. When Nb2Cl10, a dimer, is added to the acidic or basic solution, the dimer breaks apart and forms two species. In the acid solution, two trigonal bipyramids are formed with five equal chloride distances, while in the basic solution, a square pyramid with four chlorides forming a square base and one shorter axial chloride bond. Ta2Cl10 is also a dimer and divides into half in the acidic solution and forms two trigonal bipyramids. In the basic solution, the dimer breaks apart but the species formed is sufficiently acidic that it attracts two additional chloride ions and forms a seven coordinated tantalum species.

Structural Studies of the Isomorphous MCl2(PMe3)4 (M = Mo, W) Complexes

The structure of WCl2(PMe3)4 has been determined in order to allow for a comparison with its molybdenum analogue. The complexes are isomorphous, and exhibit trans-pseudooctahedral coordination, with crystallographically imposed $$\overline{4}2m$$ (D2d) symmetry. A significant distortion occurs involving the PMe3 ligands, through which one opposing pair tilts upward toward one axial chloride ligand, while the other pair tilts in an opposite manner, by 9.33°. The complex crystallizes in the tetragonal space group $$I\overline{4}2m$$ , with a = b = 9.4987(4) A, c = 12.1058(5) A, V = 1092.25(8) A3, D calc = 1.700 at 150(1) K. For a better comparison, the structure of the molybdenum complex was redetermined, at a low temperature. Its space group is also $$I\overline{4}2m$$ with a = b = 9.5193(3) A, c = 12.1083(5) A, V = 1097.22 A3, D calc = 1.426 at 150(1) K. In accord with the larger cell volume, the molybdenum complex possesses slightly longer M–Cl and M–P bonds.

ChemInform Abstract: Synthesis of Axial Dialkoxy Phosphorus(V)porphyrin Derivatives - Novel Hypervalent Phosphorus Compounds.

Water-stable, axial dialkoxy hypervalent phosphorus(V)tetraphenylporphyrins have been synthesised in a novel fashion by efficient substitution of axial chloride ligands of dichlorophosphorus(V)-tetraphenylporphyrin.