Comparative structural studies of the first row early transition metal(III) chloride tetrahydrofuran solvates

Two compounds of empirical formula MCl₃- (THF)₃, M = V and Cr, have been characterized by single crystal X-ray studies. The VCl₃(THF)₃ molecule, which has a mer octahedral stereochemistry, crystallizes in the monoclinic space group P2₁/c with a= 8.847(2),b= 12.861(5),c= 15.134(3) Å, β = 91.94(2)°, V = 1721(1) ų and Z = 4. The V-Ci(1) and V-CI(2) distances have a mean value of 2.330 [3] Å while V-CI(3) = 2.297(2) Å, The VO(1) and VO(2) distances have a mean value of 2.061[8] Å while V-O(3) = 2.102(3) Å cis ClVCl angles average 92.0[5]° and cis OVO angles average 86.2[2]° . The isostmctural complex, CrCl₃(THF)₃, has a crystal structure made up of discrete octahedral mer-CrCl₃(THF)₃ molecules with the following unit cell dimensions (space group P2₁/c): a = 8.715(1), b= 12.786(3), c = 15.122(3) Å, β = 92.15(1)°, V = 1684(1) ų and Z = 4. The CrCl(1) and CrCl(2) distances have a mean value of 2.310131 Å while CrCl(3) = 2.283(2) Å. The CrO(1) and CrO(2) distances have a mean value of 2.0101171 Å while CrO(3) = 2.077(4) Å. cis ClCrCl angles average 90.9[4]° and cis OCrO angles average 86.1 [2]°. The structures of these two octahedral complexes and those previously reported for ScCl₃(THF)₃ and TiCl₃(THF)₃ are compared and certain general trends are discussed.     

X-ray structure of a mono(1-methylthyminato) complex of cisplatin,chloro-(1-methylthyminato-N3)-cis-diammineplatinum(II) monohydrate

The crystal structure of chloro-(1-methyltyminato- N3)-cis-diammineplatinum(II) monohydrate, cis- (NH₃)₂Pt(C₆H₇N₂O₂)Cl·H₂O, is reported. The compound crystallizes in space group P$\text{1}$ with a = 6.911(2) Å, b = 8.598(3) Å, c = 11.464(4) Å, α = 100.13(3)°, β = 120.03(3)°, γ = 93.16(3)°, Z = 2. The structure was refined to R = 0.048 and R_w = 0.057. The compound contains the deprotonated 1-methylthymine ligand coordinated to Pt through N3 (1.973(10) Å). This distance represents the shortest Pt-N3(pyrimidine-2.4-dione) bond reported so far. The two PtNH₃ bond lengths differ significantly: PtNH₃ (trans to Cl) is longer (2.052(10) Å) than PtNH₃ (trans to N3 of 1-MeT) (2.002(11) Å). The PtCl distance (2.326(3) Å) is normal, as is the large dihedral angle between the Pt coordination plane and the nucleobase (76.5°).     

Oxo-bridged Ta(+3) dimers, (TaCl2L2)2(μ-O)(μ-SR2), revisited. Structural differences between isoelectronic μ-O and μ-OH complexes

The compounds Ta₂Cl₄(dmpe)₂(μ-Me₂S)(μ-O) (1) and Ta₂Cl₄(py)₄(μ-THT)(μ-O) (2) where dmpe = Me₂PCH₂CH₂PMe₂ and THT = tetrahydrothiophene, have been prepared and structurally characterized. They are authentic examples of μ-O bridged Ta^IIITa^III edge-sharing bioctahedral complexes. Their structures are virtually identical with respect to all of the bonds that they have in common. However, the structure of 1 differs significantly in its TaTa, TaO and one type of TaCl distance from the previously reported Ta₂Cl₄(dmpe)₂(μ-Me₂S)(μ-O)·HCl (3). These differences show that in 3 there is a μ-OH group hydrogen bonded to a Cl⁻ ion. The structural differences attendant upon the μ-OH ⇌ μ-O change are of general interest and are discussed. The crystallographic data for the new compounds are as follows: 1: monoclinic (P2₁/c) with a = 10.412(2), b = 14.749(2), c = 22.177(3) Å, β = 99.25(1)°, V = 3361(1) ų and Z = 4. 2: monoclinic (P2₁/a) with a = 18.238(4), b = 10.402(3), c = 19.070(2) Å, β = 95.37(2), V = 3602(2) ų and Z = 4.     

Reactions of Nb2Cl6(SMe2)3 and Ta2Cl6(SMe2)3 with compounds containing NN single bonds

Ta₂Cl₆(SMe₂)₃ reacts with PhHNNHPh to afford Ta₂Cl₄(μ-Cl)₂(μ-PhN)(PhNH₂)₃ (1) a compound with a Ta^IVTa^IV single bond, with a length of 2.644(1) Å. The compound crystallizes in space group Pnma with unit cell dimensions a = 22.960(8), b = 16.875(4), c = 6.367(3) Å, V = 2467(1) ų, and Z = 4. The reaction of Nb₂Cl₆(SMe₂)₃ with PhHCNNCHPh, merely on mixing at room temperature produced Nb₂Cl₆(SMe₂) [PhHC(N)PhHCNHNCHPh]·C₇H₈ (2) as large red crystals in ca. 50% yield. The molecule consists of two Nb^IV atoms, one six-coordinate and the other seven-coordinate, united by three bridging atoms (Cl, Cl, N) and a NbNb bond of length 2.681(1) Å. The way in which the tridentate triazo ligand is generated is completely obscure. Crystallographic data for 2: space group P2₁/n with a = 11.393(3), b = 11.988(3), c = 27.233(7) Å, β = 100.75(2)°, V = 3654(3) Å, and Z = 4.     

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

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

The synthesis and molecular structure of diiodooctacarbonyldiosmium(I), [Os2(CO)8I2]

The compound, diiodooctacarbonyldiosmium(I), [Os₂(CO)₈I₂], has been prepared by a route involving only atmospheric pressures. Its structure has been determined by X-ray crystallography. The crystals are tetragonal with a = 11.791(2), c = 23.583(4) Å, Z = 8, D_c = 3.48 Mg m⁻³. A total of 1637 reflections were collected out to θ = 25° on a CAD4 diffractometer in ω—2θ mode using Mo Kα (λ = 0.7107 Å) radiation. Lp and empirical absorption corrections were applied. The structure was solved in the space group I4₁cd using conventional heavy atom methods and refined to R = 0.0477 [R_w = 0.0424, w = (σ²F)⁻¹]. The molecule of [Os₂(CO)₈l₂] has two crystallographically equivalent halves joined by a single OsOs bond of length 2.947(3) )Å. There are no bridging ligands. The geometry about each osmium is pseudo-octahedral and the iodine atoms occupy equatorial positions with an OsI distance of 2.767(3) Å. The equatorial ligands on one osmium atom are staggered with respect to the equatorial ligands on the other osmium atom.     

Crystal structure of [chloro(diethyldithiocarbamato)butyl phenyl]tin(IV)

The crystal structure of the title compound, SnCl(C₆H₅)(C₄H₉)[S₂CN(C₂H₅)₂], was determined and refined to an R factor of 3.2% for 4876 reflections. The molecule contains five-coordinate tin in a distorted trigonal bipyramidal arrangement with the tin atom lying 0.20 Å below the equatorial plane formed by one of the sulphur atoms, S(1), and the donor carbons of the butyl and phenyl groups. The chlorine and the other sulphur atom, S(2), occupy axial sites, making a S(2)SnCl angle of 156.85(1)°. The SnS(2) bond is markedly elongated (2.764(1) Å) compared to the SnCl bond (2.449(1) Å) and the SnS(1) bond (2.454(1) Å). The structure resembles those of analogues such as (C₆H₅)₂Sn(glygly) in having both hydrocarbon ligands located in the equatorial plane. Crystal data: space group P$\text{1}$: a = 8.291(2) Å, b = 14.726(3) Å, c = 9.509(2) Å, α = 96.24(2)°, β = 107.02(3)°, γ = 116.70(2)°, Z = 2, R = 3.2% for 4876 independent reflections.     

Synthesis and crystal structure of (pipzH2)2Mo2Cl8·4H2O (pipz = piperazine)

The title compound (pipzH₂)₂Mo₂Cl₈·4H₂O (pipz = piperazine),was isolated from the solution of (morphH)₂Mo₂Cl₆(H₂O)₂ in HCl 1:1 by addition of (pipzH₂)Cl₂. This reaction indicates the reversibility of the substitution of chloride ions in Mo₂Cl₈^4? by water molecules. (pipzH₂)₂Mo₂Cl₈·4H₂O crystallizes in the Pbca space group, with a = 15.154(2), b = 13.170(2), c = 12.208(2) Å and Z = 4. The structure was solved by the Patterson method and refined to the unweighted and weighted residuals of 0.050 and 0.048. The crystal structure is built form Mo₂Cl₈^4?, (pipzH₂)²⁺ and H₂O. The MoMo distance of 2.129(3) Å is the shortest one found in all structurally-characterised Mo₂X₈^4? (X = Cl, Br) anions. Four independent MoCl distances are 2.456(3), 2.445(3), 2.463(4) and 2.455(4) Å. The (pipzH₂²⁺ exists in a usual chair conformation. There is a network of hydrogen bonds of the type NH?Cl, NH?O, OH?Cl and OH?O between the ions and water molecules.     

Structural chemistry of actinide compounds with different coordination numbers: The crystal and molecular structures of tetrachlorotris(N,N-diethylpropionamide)thorium(IV) and tetra-N-thiocyanato tetrakis(N,N-dimethylpropionamide)thorium(IV)

The crystal and molecular structures of ThCl₄(depa)₃ (1) (depa = N,N-diethylpropionamide) and Th(NCS)₄(dmpa)₄ (2) (dmpa = N,N-dimethylpropionamide) have been determined from three-dimensional X-ray diffraction data. The compounds crystallize in space group P2₁/n (1) and P2₁/a (2), with a = 18.107(5), b = 10.347(3), c = 17.867(5) Å, β = 108.5(1)°, Z = 4 (1) and a = 22.759(6), b = 13.763(4), c = 11.910(3) Å, β = 91.4(1)° and Z = 4 (2). Full matrix least-squares refinement of both structures gave for (1) with 3126 intensity data R = 0.046 and Rw 0.046 and for (2) with 3480 intensity data R = 0.050, Rw 0.054. The different steric constraints imposed by the ligand give rise to different coordination numbers. In (1) the coordination polyhedron about the seven co-ordinate thorium atom is a pentagonal bipyramid with two chlorine atoms in the axial positions, an unusual geometry for Th(IV) species. The average bonding distances are ThO = 2.340(9), ThCl_eq = 2.754(3) and ThCl_ax = 2.692(3) Å.In (2) the less hindering dmpa ligand favours the presence of four of them in the metal coordination sphere in a distorted square antiprismatic coordination geometry. ThO and ThN average 2.37(1) and 2.49(2) Å respectively.     

Caffeine complexes of platinum(II): crystal structure of cis-[Pt(C8H10N4O2)2Cl2]·0.4H2O

The preparations are reported of cis[Pt(caffeine)₂Cl₂]·0.4H₂O, Pd(caffeine)₂Cl₂, the methanol adduct of the previously known compound K[Pt(caffeine)Cl₃], and Pt(caffeine)(cytidine)Cl₂. Crystals of [Pt(caffeine)₂Cl₂]·0.4H₂O are tetragonal P4₂/n with a = 13.156(2) 0?, c = 12.734(2) 0?, Z = 4. The structure was refined on 945 reflections to R = 0.025. The molecule is cis with a crystallographic two-fold axis bisecting the ClPtCl and NPtN angles. The Pt is square planar with PtN and PtCl bonds of 2.029(5) Å and 2.271(2) Å respectively. There is a 5.4° dihedral angle between the imidazole and pyrimidine rings, and the imidazole ring is rotated away from the coordination plane by 86.4°. Symmetry related caffeine units pack parallel to each other with an inter-ring separation of 3.45 Å.     

Metal-penicillamine interactions. Part 1. Preparation and crystal structure of a 1:1 complex of mercuric chloride with d-penicillamine, 2[μ3-Cl){HgSC(CH3)2CH(NH3)COO}3·3(μ2-Cl)· 2(H3O)·(H2O·Cl)3

A 1:1 complex of mercuric chloride with D-peniccillamine has been isolated and characterised as 2[(μ₃-Cl){HgSC(CH₃)₂CH(NH₃)COO}3]·3(μ₂-Cl)·2(H₃O)·(H₂O·Cl)₃. The compound crystallises in cubic space group P4₁32, with a = 18.679(5) Å and Z = 4. The structure, refined to R_F = 0.086 for 443 observed Mo-Kα diffractometer data, features a triply bridging chloride ion linking three equivalent [HgSC(CH₃)₂CH(NH₃)COO]⁺ units [Hg-Cl = 2.37(1) Å, Hg-Cl-Hg′ = 98.5(9)°]. The carboxylate groups of a pair of adjacent penicillamine ligands are strongly linked via a symmetrical O?H?O hydrogen bond of length 2.24(8) Å, and neighboring pyramidal trinuclear [μ₃-Cl){HgSC(CH₃)₂CH(NH₃)-COO}₃]²⁺ moieties are further connected by symmetrical chloride bridges [Hg-Cl = 3.06(2) Å; HgClHg′' = 79.6(7)°] to form a three-dimensional network. The voids in the lattice are filled by hydronium ions and novel planar cyclic hydrogen-bonded (H₂O·Cl^?)₃ rings of edge O-H?Cl = 2.46(4) Å.     

Monomeric molybdenum(V) complexes. 4. The structure of tetraphenylarsonium oxodichloro(N-2-oxophenylsalicylideniminato)molybdate(V), [Ph4As] [MoOCl2(SalphO)]

The structure of [Ph₄As] [MoOCl₂(SalphO)], where SalphO is N-2-oxophenylsalicylideniminate dianion, has been determined by X-ray crystallography. The complex crystallizes in the monoclinic space group P2₁/n with a = 11.829(2), b = 16.149(3), c = 17.410(3) Å, β = 97.485(15)° and Z = 4. The calculated and observed densities and 1.566 and 1.573(10) g cm^?3, respectively. Block-diagonal least-squares refinement of the structure using 4722 independent reflections with I ? 3σ(I) converged at R = 0.0345 and R_w = 0.0484. The crystal contains [Ph₄As]⁺ cations and [MoOCl₂(SalphO)]^? anions. The Mo atom in the anion is in a distorted octahedral coordination environment. A planar terdentate Schiff base ligand occupies meridional positions with the N atom trans to the terminal oxo group (O_t). Two Cl atoms are cis to the O_t atom. The Mo atom is displaced by 0.33 Å from the equatorial plane toward the O_t atom. The MoO_t distance is 1.673(3) Å. The MoN bond trans to the O_t atom is 2.298(4) Å. The two MoCl bond lengths are 2.371(1) and 2.408(1) Å. The difference of 0.037 Å is significant (30 σ). Preparations of the title complex and the related complexes are also described.     

Synthesis and crystal and molecular structure of a methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate complex

Bis-Methyl N,N-diethylcarbamylmethylenephosphonato dysprosium thiocyanate, Dy[O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂]₂(NCS) was prepared from the combination of ethanolic solutions of Dy(NCS)₃·xH₂O and (CH₃O)₂P(O)CH₂C(O)N(C₂H₅)₂. The complex was characterized by infrared and NMR spectroscopy, and single crystal X-ray diffraction methods. The crystal structure was determined at 25 °C from 3727 independent reflections by using a standard automated diffractometer. The complex was found to crystallize in the monoclinic space group P2₁/c with a = 13.282(4) Å, b = 19.168(5) Å, c = 9.648(2) Å, β = 90.09(2)°, Z = 4, V = 2456.4 ų and ?_cald = 1.72 g cm^?3. The structure was solved by standard heavy atom techniques, and blocked least-squares refinement converged with R_f = 4.7% and R_wF = 4.9%. The Dy atom is seven coordinate and bonded in a bidentate fashion to two anionic phosphonate ligands [O₂P(OCH₃)CH₂C(O)N(C₂H₅)₂^?] through the carbonyl oxygen atoms and one of two phosphonate oxygen atoms. In addition, each Dy atom is coordinated to two phosphonate oxygen atoms from two neighboring complexes and to the nitrogen atom of a thiocyanate ion. This coordination scheme gives rise to a two-dimensional polymeric structure. Some important bond distances include DyNCS 2.433(8) Å, DyO(carbonyl)_avg 2.39(2) Å, DyO(equat. phosphoryl)_avg 2.303(8) Å, DyO(axial phosphoryl)_avg 2.25(2), PO(phosphoryl)_avg 1.493(3) Å and CO(carbonyl)_avg 1.25(1) Å.     

Synthesis and x-ray structure of a Hg(II) complex with adenine N(1)-oxide. A model for mercury binding to DNA

The synthesis and crystal structure of the adenine N(1)-oxide complex with mercury(II) chloride, (C₅H₅N₅O)HgCl₂ are reported. Crystals of the coordination compound belong to the monoclinic system, space group P2₁/n with the following primary crystallographic data: a = 6.685(1) Å, b = 11.798(2) Å, c = 10.155(1) Å, β = 100.22(1)°, V = 906.04 ų, Z = 4. The structure was elucidated by conventional Patterson and Fourier methods and refined by the full matrix least-squares technique on the basis of 1977 observed reflections to an R value of 0.074. The basic unit of the structure is a dimer, with a centre of symmetry, consisting of two HgCl₂ moieties and two adenine N(1)-oxide ligands. A polymeric structure results from the bridging interactions of chloride ions. Adenine N(1)-oxide acts as a bidentate bridging ligand, coordinating through N(7) and O(1). The coordination geometry around the mercury ion is a distorted square pyramid with N(7) and three chlorines (two of which are centro-symmetrically related) forming the square plane and O(1) occupying the axial position. Hg also interacts indirectly with N(6) through a Cl

HN hydrogen bond. Principal intracomplex geometrical parameters are as follows: HgN(7) = 2.61(1) Å, HgO(1) = 2.55(1) Å, HgCl(1) = 2.330(3) Å, HgCl(2) = 2.318(3) Å, HgCl(2′) = 3.347(3) Å. The cis angles range from 77.5° to 107.9° and the two trans angles are 155.5° and 163.1°. The centro-symmetrically related bases overlap partially and pack at a distance of 3.2 Å. The glide-related bases are linked by a hydrogen bond, N(9)H

O(1) and are inclined to one another by 109.7°. The results are compared with those derived from spectroscopic and other physicochemical studies on metal interaction with adenine N(1)-oxide. Based on the present structural observations and earlier experimental results a possible mechanism is proposed for mercury interaction with DNA.     

Preparation,properties and crystal structures of nickel(II) complexes with acyclic schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane or 3,3′-diamino-N-methyl-dipropylamine

Nickel(II) complexes with the compartmental Schiff bases derived from 2,6-diformyl-4-chlorophenol and 1,5-diamino-3-thiapentane (H₂L¹) or 3,3′-diamino-N-methyl-dipropylamine (H₂L²) were synthesized, and the crystal structures of [Ni(L¹)- (py)₂] and [Ni(L²)(dmf)]·H₂0 were determined by X-ray crystallography.Ni(L¹)(py)₂ is monoclinic, space group C2/c, with a= 18.457(6), b = 11.116(7), c= 16.098(6) Å, and β = 115.79(5)°; D_c = 1.49 g cm⁻³ for Z = 4. The structure was refined to the final R of 6.9%. The molecule has C₂ symmetry. The nickel atom is six-coordinated octahedral. Selected bond lengths are: NiO 2.04(1) Å, NiN (L¹) 2.08(1) Å, NiN(py) 2.17(1) Å.[Ni(L²)(dmf)]·H₂O is monoclinic, space group P2₁/n, with a = 17.329(6), b = 13.322(7), c = 12.476(7) Å and β = 95.43(5)°; D_c = 1.45 g cm⁻³ for Z = 4. The structure was refined to the final R of 5.1%. The nickel atom is bonded in the octahedral geometry to the bianionic pentadentate ligand L² and to one molecule of dimethylformamide. Selected bond lengths are: NiO (charged) 2.063(3) Å (mean value), NiO (neutral) 2.120(3) Å, NiN (planar) 2.050(3) Å (mean value), NiN (tetrahedral) 2.177(3) Å.     

The crystal and molecular structures of dioxo mo(VI) complexes of tripodal,tetradentate N,S-donor ligands

The crystal and molecular structures of the complexes MoO₂((SCH₂CH₂)₂NCH₂CH₂SCH₃), I and MoO₂((SCH₂CH₂)₂NCH₂CH₂N(CH₃)₂), II, have been determined from X-ray intensity data collected by counter methods. Compound I crystallizes in two forms, Ia and Ib. In form Ia the space group is P2₁/n with cell parameters a = 7.235(2), b = 7.717(2), c = 24.527(6) Å, β = 119.86(2)°, V = 1188(1) ų, Z = 4. In form Ib the space group is P2₁/c with cell parameters a = 14.945(5), b = 11.925(5), c = 14.878(4) Å, β = 114.51(2)°, V = 2413(3) ų, Z = 8. The molecules of I in Ia and Ib are very similar having an octahedral structure with cis oxo groups, trans thiolates (cis to both oxo groups) and N and thioether sulfur atoms trans to oxo groups. Average ditances are MoO = 1.70, MoS (thiolate) = 2.40, MoN = 2.40 and MoS (thioether) = 2.79 Å. Molecule II crystallizes in space group P2₁2₁2₁ with a = 7.188(1), b = 22.708(8), c = 7.746(2) Å, V = 1246(1) ų and Z = 4. The coordination about Mo is octahedral with cis oxo groups, trans thiolates and N atoms trans to oxo. Distances in the first coordination sphere are MoO = 1.705(2), 1.699(2), MoS = 2.420(1), 2.409(1) and MoN = 2.372(2), 2.510(2) Å. The conformational features of the complexes are discussed. Complex I displays MoO and MoS distances which are very similar to those found by EXAFS in sulfite oxidase. This similarity is discussed.     

Synthesis and characterization of two isomers of Os3(CO)10(C5H4N-2-C(H)NR) and the conversion to ortho-metallated HOs3(C5H3N-2-C(H)NR)(CO)9. Part III. X-ray Structure of HOs3(C5H3N-2-C(H)Ni-Pr)(CO)9

Os₃(CO)₁₀(MeCN)₂ reacts at room temperature in MeCN or toluene with R-Pyca2 to yield two isomers of Os₃(CO)₁₀(R-Pyca) that differ in the bonding of the R-Pyca ligand to the Os₃(CO)₁₀ unit. In all cases Os₃(CO)₁₀(R-Pyca(4e)) (isomer A; 4a: R = c-Pr, 4b: R = i-Pr, 4c: R = neo-Pent, 4d: R = t-Bu), containing a chelating 4e donating R-Pyca ligand and three OsS bonds, could be isolated. In the case of R = c-Pr and R = i-Pr Os₃(CO)₁₀(R-Pyca(6e)) (isomer B; 5a: R = c-Pr, 5b: R = i-Pr), in which only two OsS bonds are present and the R-Pyca ligand is bonded as a 6e donating ligand bridging two non-bonded Os atoms, could be isolated as a minor product.At 70 °C Os₃(CO)₁₀(R-Pyca(4e)) (4b and 4d) loses one carbonyl and the pyridine moiety of the R-Pyca ligand is ortho-metallated to form HOs₃(C₅H₃N-2-C(H)NR)(CO)₉ (6b: R = i-Pr and 6d: R = t-Bu). Under the same conditions Os₃(CO)₁₀(i-Pr-Pyca(6e)) (5b) reacts to Os₂(CO)₆(6e)) (7b) containing a bridging 6e donating ligands. The latter two reactions were followed with FT-IR spectroscopy in a high temperature IR cell.The structure of the complexes in solution have been studied by ¹H and ¹C NMR and IR spectroscopy. The stoichiometries of 4a and 5a were determined by FAB-mass spectrometry while an exact mass determination was carried out for 4a.The crystal structure of 6b has been determined. Crystal of 6b are monoclinic, space group P2₁/n, with a = 7.808(2),b = 17.613(3),c = 16.400(8)Å, β = 94.09(3)° and Z = 4. The structure was refined to R = 0.039. The molecule contains a triangular array of osmium atoms [Os(1)Os(2) = 2.898(2)Å, Os(1)Os(3) = 2.886(2)Åand Os(2)O(3) = 2.911(2)Å] and nine terminally bonded carbonyl ligands. The C₅H₃N-2-C(H)N-i-Pr ligand is chelate bonded to Os(2) with the pyridine and imine nitrogens atoms axially and equatorially coordinated respectively [Os(2)N(1) = 2.00(2)Åand Os(2)N(2) = 2.11(2)Å]. The i-Pr-Pyca ligand is ortho-metallated at C(1) and forms a four membered ring containing Os(2), Os(3), C(1) and N(1), the Os(3)C(1) distance being 2.12(2)Å. The hydride, which could not be located unequivocally from a difference Fourier map is proposed to bridge the Os(2)(3) bond on the basis of stereochemical considerations.     

The phenomenon of conglomerate crystallization. XV. Spontaneous resolution in coordination compounds. XIII. The crystallization behaviour and the crystal and molecular structure of Δ(λδ)-cis-Rh(en)2(NO2)2]Cl

The title compound, I, crystallizes in the monoclinic space group P2₁ with cell constants: a = 6.599(3), b = 11.121(2), c = 8.375(1) Å and β = 106.35(2)°; V = 589.74 ų and D(calc; Z = 2) = 1.974 g cm⁻³. The compound is isomorphous and isostructural with its Co analogue. A total of 2982 data were collected over the range of 4°  20  70°; of these, 2537 (independent and with I ⩾ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ = 16.6 cm⁻¹) and the relative transmission coefficients ranged from 1.000 to 0.9504. Refinement was carried out for both enantiomeric configurations and the crystal used was found to contain cations with Δ(λδ) absolute configuration. The final R(F) and R_w(F) residuals were, respectively 0.0220 and 0.0239 for (−−−; i.e.Δ(λδ)) and 0.0231 AND 0.0317 FOR (+++; i.e.Λ(δλ)). Thus, the former was selected as correct for our specimen.In the case of I, as well as in the Co derivative [cis-Co(en)₂(NO₂)₂]Cl (II), the conformation of one of the rings is opposite that expected for the lowest energy conformation, which in the current case should be Δ(λλ)).The RhN(NO)₂ distances are 2.020(2) and 2.010(2) Å, while the RhN(amine) distances, trans to the NO₂ ligands are 2.085(2) and 2.093(1) Å, values distinctly longer than the other two RhN distances (2.064(1) and 2.068(1) Å). The latter are the RhN distances to the terminalNH₂ ligands located trans to each other. Thus, we observe a trans effect, which is more pronounced in I than in II, and which is of comparable magnitude to that observed in the case of the trien derivative, [cis-α-Rh(trien)(NO₂)₂]Cl(III).Parallel with an increase in metalN distances in going from [cis-α-Co(trien)NO₂)₂]Cl·H₂) (IV) to (III) is an increase in the torsional angles of the outer rings (NCCN) of about 10°. Comparison of these parameters in I and II reveal that this change is not so marked for this pair since in I they are −54.9° and 52.8° while in II they are 50.2° and −48.1°; i.e. a change of only 4°. This important difference between trien and en derivatives is caused by the presence of the central five-membered ring, which for compounds III and IV remains largely unchanged, except for the metalN distances.The NO bond lengths are 1.244(3), 1.220)(2), 1.237(2) and 1.211(2) Å, which are similar to those found for the analogous Co isomer. The CN bond lengths are 1.492(3), 1.474(2), 1.486(2) and 1.475(2) Å, while the CC bonds are 1.509(3) and 1.524(3) Å. These values are also comparable with those obtained for the Co isomer and, in fact, the pattern of the bonds is nearly identical in both, including the common feature of having a longer CC bond for the en ring with the conformation opposite that expected.As was the case with the Co analogue, the Cl⁻ anion is associated with the hydrogens of the secondary nitrogen (trans to the −NO₂) ligands, the Cl…H7 distance being 2.18(3) Å and the <Cl…H7N2 = 163°.     

Syntheses,structures and ligand dissociation kinetics of Vitamin B12 model compounds with exceptionally poor electron donating groups,LCo(DH)2CHX2 (X = Cl or Br)

The syntheses and ligand dissociation kinetics of vitamin B₁₂ model compounds LCo(DH)₂CHX₂ with X = Cl and Br and L = different neutral N- and P- ligands are reported together with the crystal structures of the CHCl₂ derivatives with L = py (1) and 1,5,6-trimethylbenzimidazole, Me₃Bzm (2). Compound 1 crystallizes in the space group P2₁/n with cell parameters a = 9.617(1), b = 12.601(2), c = 15.586(2) Å, β = 95.44(1)°; 2 crystallizes in the space group P1 with cell parameters a = 8.867(2), b = 10.719(2), c = 13.345(2) Å, α = 94.81(2), β = 90.89(1), γ = 105.63(2)°. The two structures were solved by Patterson and Fourier methods and refined by least-squares methods to final R values of 0.037 (1) and 0.036 (2), using 3474 (1) and 4435 (2) independent reflections.The axial NCoC fragment is characterized by CoN and CoC distances of 2.045(2) and 1.995(2) Å in 1 and 2.043(2) and 1.983(2) Å in 2, respectively. The CoC bond lengths have the smallest values so far reported in both py and Me₃Bzm alkylcobaloximes.The displacement of the L ligand followed SN1 LIM behaviour and the corresponding rate constants depend upon the nature of L and vary in CHCl₂ derivatives from 2.42 X 10⁻¹ s⁻¹ for 2-aminopyridine to 1.99 X 10⁻⁵ s⁻¹ for P(OMe)₃. For fewer CHBr₂ analogs the rate constants were smaller.Kinetic results confirm previous findings that the donating ability of CHBr₂ is less than that of CHCl₂, although the electronegativity of Cl and Br species would suggest an opposite trend. Some relationships between kinetic and structural properties are discussed.     

Haloalkyl complexes of the transition metals. Part 5. The synthesis and reactions of some new pentamethylcyclopentadienyl halomethyl and methoxymethyl complexes of molybdenum(II) and tungsten(II) and the X-ray crystal structure of the cationic ylide complex [η-C5Me5W(CO)3CH2PPh3]I

Synthetic routes are described for the new halo- methyl complexes of the type [η-C₅Me₅M(CO)₃- CH₂X]. The complexes where M = Mo, X = Cl or OMe and M = W, X = Cl, I, OMe have been fully characterized. Reaction of [η-C₅Me₅Mo(CO)₃CH₂Cl] with PPh₃ in methanol under reflux or acetonitrile at room temperature gives [η-C₅Me₅Mo(CO)₂(PPh₃)- Cl], whereas reaction of [η-C₅Me₅W(CO)₃CH₂I] with PPh₃ under similar conditions gives the cationic phosphorus ylide complex [η-C₅Me₅W(CO)₃CH₂- PPh₃]I. The structure of this ylide complex has been determined by X-ray crystallography. The complex crystallizes with half a molecule of CH₂Cl₂ in the monoclinic space group P2₁/n with a = 16.616- (8), b = 11.738(6), c = 18.126(9) Å, β = 101.74(2)° and Z = 4. The structure was solved and refined to R = 0.076. It confirms the formulation of the compound and the presence of the ylide ligand, WC_ylide 2.34(2) Å, PC_ylide 1.82(2) Å and the WC_ylideP angle of 119(1)°.