Nigel P. C. Walker

Preparation of the bis(trimethylsilyl)amido lanthanide chlorides [{Ln[N(SiMe3)2]2(µ-Cl)(thf)}2](thf = tetrahydrofuran), and the crystal and molecular structures of the gadolinium and ytterbium complexes

Reaction of LnCl3 with 2 equivalents of LiL [L = N(SiMe3)2] in tetrahydrofuran (thf) at –5 °C yields [{LnL2Cl(thf)}2] for Ln = Eu, Gd, or Yb or [YL2Cl(thf)2] for Ln = Y. X-Ray crystal structure analysis of the compounds of Gd and Yb confirms the formation of halide-bridged dimers. In the M2Cl2 bridging unit the M–Cl bond lengths differ slightly and the angle at the metal (ca. 74°) is much smaller than at chlorine (ca. 106°). The metal co-ordination geometries are irregular but can be best described as distorted trigonal bipyramidal with the bridging chlorines spanning one axial and one equatorial site. The bond lengths M–Cl and M–N indicate a Gd–Yb radius difference of ca. 0.07 A, but the M–O distances differ by 0.093 A. Variable-temperature n.m.r. studies of [{EuL2Cl(thf)}2] and [{YbL2Cl(thf)}2] show that there is free rotation about Ln–N and Ln–O bonds at room temperature. These rotations are frozen out at low temperatures to give a solution structure having higher symmetry (C2h) than that found in the crystal.

Triosmium clusters with ligands derived from αβ-unsaturated ketones. X-ray crystal structures of [Os3H(CO)10(cis-MeCCHCOMe)] and [Os3H(OH)(CO)9(PMe2Ph)]

The compounds [Os3H2(CO)10] and [Os3(CO)10(MeCN)2] both react with the enones RCHCHCOMe (R = H, Me, or Ph) by metallation at the vinylic C–H groups to give compounds of type [Os3H(CO)10-(RC4H4O)], certain of which were also obtained from [Os3H2(CO)10] and CHCCOMe. Three isomers of [Os3H(CO)10(C4H5O)] were isolated, containing CH2CCOMe and cis- and trans-CHCHCOMe respectively. The most stable isomer, [Os3H(CO)10(cis-CHCHCOMe)], is decarbonylated at 130 °C to give [Os3H(CO)9(cis-CHCHCOMe)] and contains a linear Os3 chain and a terminal hydride replaceable by Cl from CCl4. The substituted compounds [Os3H(CO)10(cis-RCCHCOMe)](R = Me or Ph) have a different structure; crystals of the compound with R = Me are monoclinic, space group C2/c, with a= 17.377(2), b= 14.293(2), c= 16.476(2)A, β= 91.79(3)°, and Z= 8. The structure was solved via the heavy-atom method and refined to R= 0.034 using 2 906 diffractometer data with l 1.5σ(l). The structure is based on that of [Os3(CO)12] with a chelating MeCCHCOMe ligand occupying an axial and an equatorial site. The bridging hydride is not replaced by Cl in CCl4 solution. Unable to obtain good crystals of [Os3H(CO)10(cis-CHCHCOMe)], [Os3H2(CO)9(PMe2Ph)] was treated with CH2CHCOMe in an attempt to obtain a PMe2Ph-substituted derivative but instead [Os3H(OH)(CO)9(PMe2Ph)], was obtained, the crystals of which are monoclinic, space group P21/n, with a= 17.535(2), b= 9.500(1), c= 14.326(2)A, β= 101.86(1)°, and Z= 4. The structure was solved by the heavy-atom method and refined to R= 0.041 using 3 474 diffractometer data with l 1.5σ(l).

Lanthanide thiolate complexes; synthesis of [Ln{N(SiMe3)2}(µ-SBut)]2(Ln = Eu, Gd, Y) and the X-ray crystal structure of the Gd complex

The lanthanide thiolate complexes [LnL2(µ-SBut)]2[L = N(SiMe3)2; Ln = Eu, Gd, Y] have been prepared by reaction of [LnL2Cl(THF)]2(Ln = Eu, Gd; THF = tetrahydrofuran) or LnL2(THF)2(Ln = Y) with LiSBut; the crystal structure of [GdL2(µ-SBut)]2 is reported.

Penta(methoxycarbonyl)cyclopentadienyl-substituted germanium(II) and tin(II) compounds. X-ray crystal structure of bis[penta(methoxycarbonyl)cyclopentadienyl]tin(II)

Abstract Reaction of decamethyl-germanocene or -stannocene with equimolar amounts of penta(methoxycarbonyl)cyclopentadiene leads to the ionic compounds pentamethylcyclopentadienylgermanium-penta(methoxycarbonyl)cyclopentadienide (3) and pentamethylcyclopentadienyltin-penta(methoxycarbonyl)cyclopentadienide (4), in which pentamethylcyclopentadienyl-germanium and -tin cations are present together with the penta(methoxy)cyclopentadienide anion. A molar ratio of 1 2 yields the covalent bis[penta(methoxycarbonyl)cyclopentadienyl]-germanium(II) (5) or -tin(II) (6). Crystals of the tin compound 6 are orthorhombic, space group P21212 with a 15.656(2), b 15.424(2), c 7.033(1) A and Z = 2. The structure of 6 was solved via the heavy-atom method and refined to R = 0.037 using 1098 diffractometer data with I ⩾ 1.5σ(I). The tin atom, which lies on the two-fold axis, has four-fold oxygen coordination from carbonyl oxygen atoms of two methoxy carbonyl groups on each of two ligands, with SnO distances of 2.240(9) and 2.271(9) A. The compounds 5 and 6 are fluxional in solution.

Reaction of trithiazyl trichloride, (NSCl)3, with triphenylphosphine or triphenylphosphine metal complexes. X-Ray crystal structure of aminotriphenylphosphonium chloride–dichloromethane (1/1), [Ph3PNH2]Cl·CH2Cl2

The reaction between (NSCl)3 and [RuCl2(PPh3)3] gives [RuCl3(NS)(PPh3)2] together with [Ph3PNH2]Cl·CH2Cl2(2)(characterised by X-ray crystallography, 31P n.m.r. and i.r. spectroscopy) and Ph3PNH (4). Reaction between (NSCl)3 and PPh3 also gives (2) and (4); a mechanism for this reaction is proposed. Reactions of (NSCl)3 with [RhCl(PPh3)3], trans-[Rh(CO)Cl(PPh3)2], or [Rh(NO)(PPh3)3] were investigated by 31P n.m.r. and contrary to several previous reports do not give thionitrosyl complexes but rather result in the formation of (2) and (4) or in the oxidation of the material to [Rh(CO)Cl3(PPh3)2]. The existence of any rhodium phosphine thionitrosyls is thus cast into doubt.

Metallation of 2-ethenylpyridine at triosmium clusters: X-ray crystal structures of the open trinuclear clusters [Os3H(CO)9L(NC5H4CHCH)](L = CO or PMe2Ph)

The compounds [Os3H2(CO)10] and [Os3(CO)10(MeCN)2] each react with 2-ethenylpyridine (NC5H4CHCH2) with C–H bond cleavage at the terminal carbon atom to give [Os3H(CO)10-(NC5H4CHCH)], (1). An analogous compound [Os3H(CO)9(PMe2Ph)(NC5H4CHCH)], (2), is formed similarly from [Os3H2(CO)9(PMe2Ph)]. Single-crystal X-ray structures of compounds (1) and (2) are reported. In these clusters the metal triangles have opened out with Os–Os–Os angles of 160.0(1) and 160.4(1)° in (1) and (2) respectively. Each of the compounds contains a terminal hydride ligand replaceable by Cl in carbon tetrachloride and has a five-electron donor NC5H4CHCH ligand chelating at a terminal Os atom of the Os3 chain with a η2-alkene co-ordination at the central Os atom. 2-Ethynylpyridine (NC5H4CCH) reacts with [Os3H2(CO)10] to give compound (1) and an isomer in which the alkene is trans rather than cis and in which the 2-pyridyl group is non-co-ordinated.

Co-ordination chemistry of higher oxidation states. Part 13. Synthesis and properties of alkali-metal hydroxo-oxo-osmate(VIII) compounds and the molecular structure of Cs[O4Os(µ-OH)OsO4]

The reaction of concentrated aqueous solutions of caesium or rubidium hydroxide with osmium tetraoxide, in various ratios produced the osmates(VIII), M2[OsO4(OH)2], M[OsO4(OH)], and M[O4Os(OH)OsO4](M = Rb or Cs). Potassium and sodium hydroxide produced only K2[OsO4(OH)2] and Na2[OsO4(OH)2]·2H2O, respectively. Vibrational spectra show the [OsO4(OH)2]2- ions to have cis-octahedral structures. The structure of the title complex was established by a single-crystal X-ray study and shown to be monoclinic, space group Cc, with a= 14.304(4), b= 5.798(1), c= 10.527 (4)A, β= 109.92(3)°, and Z= 4. The structure was refined to R= 0.059 from 710 reflections. The anion contains distorted trigonal-bipyramidal co-ordination (O5) about the osmium atoms, which are linked via a single bent hydroxo-bridge Os–O (H)–Os, 133(1)°. The terminal OsO bonds lie in the range 1.62(4)—1.77(3)A and Os–OH 2.21 (2) and 2.22(2)A. Vibrational spectra are reported for M[OsO4(OH)], M[O4Os(OH)OsO4](M = Cs or Rb), and for barium and strontium osmates(VIII), and possible structures proposed.

Structural studies of arylazo and arylimino compounds. 15N NMR and X-ray crystallographic studies of azo–hydrazo tautomerism

15 N NMR measurements on several diarylazo, arylhydrazonopyrazolone, diarylazomethine and arylaminomethylidenepyrazolone compounds are reported. The presence of hydrazo tautomers is recognised by NOE experiments. The crystal structures of 4-(2,6-dibromo-4-methylphenylazo)-3-hydroxy-N,N-diethylaniline (12) and 4-(2-bromophenylhydrazono)-3-methyl-phenyl-1H-pyrazol-5(4H)-one (15) have been determined from X-ray diffraction data. Both of these molecules contain a six-membered [graphic omitted] ring as a result of intramolecular hydrogen bonding. Whereas (12) exists as the azo-phenol tautomer, the pyrazolone (15) is in the hydrazo-ketone form. The implication of these results for copper-assisted nucleophilic substitution of the halogen in these aryl bromides is discussed.

Tributyltin(IV) penta(methoxycarbonyl)cyclopentadienides [SnBu3L2]+-[C5(CO2Me)5]–. X-Ray crystal structure of the diaquatributyltin(IV) salt, [SnBu3(OH2)2][C5(CO2Me)5], and electron spin resonance spectrum of the radical C5(CO2Me)5

The ionic penta(methoxycarbonyl)cyclopentadienide salts of the diligated tributyltin(IV) cation, [SnBu3L2][C5(CO2Me)5][L = H2O, OP(NMe2)3, or HCONMe2], have been isolated, and the crystal structure of the diaqua compound has been determined. The cation and anion have approximate C3v and D5h symmetry respectively, and, in the anion, the methoxycarbonyl groups are twisted out of the plane of the ring by between 29.2 and 53.2°. If 1,2,3,4,5-penta-(methoxycarbonyl)cyclopentadiene, or its dehydrodimer, (MeO2C)5C5C5(CO2Me)5, is photolysed, the e.s.r, spectrum of the persistent radical C5(CO2Me)5˙ is observed, a(H)= 0.61 G.

The X-ray crystal structure and magnetic properties of a binuclear copper (II) complex of 2-α-hydroxybenzylbenzimidazole and its anion {[Cu2(C14H12N2O)2(C14H11N2O)2] (ClO4)2•5C2H5OH}

Abstract The preparation, crystal structure and diamagnetism of Cu2(HOBB)2 (OBB)2(ClO4)2·5C2H5OH where HOBB is 2-α-hydroxybenzylbenzimidazole and OBB its deprotonated form are reported. The crystals are triclinic P 1 with a = 19.380(4), b = 21.345(6), c = 9.484(3) A, α = 102.52(2), β = 103.93(2), γ = 105.76(2)°, Z = 2. The structure was refined with 6593 reflections [I⩾2σ(I)] to R = 0.059. The molecule contains bridging OBB and non-bridging HOBB resulting in a geometry around each copper ion that is distorted square pyramidal with apical hydroxyl groups. An interesting feature of the molecule is that both of the apical hydroxyl groups lie on the same side of the plane defined by the Cu2O2core.