Showing papers in "Journal of The Chemical Society-dalton Transactions in 1977"
TL;DR: In this paper, a computer simulation of the metal-ion binding to low-molecular-weight ligands in human blood plasma was performed, and the results showed that ternary zinc citrate complexes were more important than binary complexes.
Abstract: An investigation by computer simulation into the nature of the metal-ion binding to low-molecular-weight ligands in human blood plasma is described. Although the absolute concentrations of the metal-complex species are controlled by protein binding, the percentage distribution of transition-metal ions amongstthe low-molecular-weight ligands is not. Hence errors arising from the omission of protein–metal equilibria are successfully by-passed. The distribution of Ca2+, Mg2+, Mn2+, Fe3+, Cu2+, Zn2+, and Pb2+ amongst 5 000 complexes formed with 40 ligands has been computed. In order to cope with multicomponent systems of such a large size, a computer program has been developed. Ternary complexes account for the larger percentage of CuII and FeII species, all the former involving histidinate and all the latter, citrate. Binary complexes are favoured by CaII, MgII, and MnII. Zinc(II) and PbII form both binary and ternary complexes amongst the predominant species. In contrast with earlier work, ternary zinc citrate complexes are found to be important.
294 citations
TL;DR: A series of subvalent Group 4B metal amides of general formula M(NR1R2) have been prepared from the appropriate lithium amide and metal(II) halide as mentioned in this paper.
Abstract: A series of subvalent Group 4B metal amides of general formula M(NR1R2)2[(i) R1= SiMe3, R2= But; M = Ge, Sn, or Pb; (ii) R1= R2= SiMe3; M = Ge, Sn, or Pb; and (iii) R1= R2= GeMe3, SiEt3, or GePh3; M = Ge or Sn] has been prepared from the appropriate lithium amide and metal(II) halide. Under ambient conditions, the amides are pale yellow to red, thermochromic, diamagnetic, low-melting solids or liquids, and are soluble in hydrocarbons (C6H6 or C6H12) in which they are diamagnetic monomers. The lower homologues give parent molecular ions as the highest m/e species. Infrared spectra show a band at 380–430 cm–1[νasym(MN2)], and 1H or 13C n.m.r. spectra are consistent with the bent-singlet formulation. In the visible region the compounds exhibit a band (364–495 nm) of moderate intensity (Iµ= 600–2 050 dm3 mol–1 cm–1 in n-C6H14) indicative of an allowed electronic transition. Photolysis of each diamide in n-hexane in the cavity of an e.s.r. spectrometer affords (a) the persistent (t½ 5 min—3 months at 25° C) metal-centred radical Ṁ(NR1R2)3[(i) R1= SiMe3, R2= But, M = Ge or Sn; (ii) R1= R2= SiMe3 or GeMe3, M = Ge or Sn; or (iii) R1= R2= GeEt3, M = Sn], (b) a lead mirror (for the lead amides), or (c) no sign of reaction (for the more bulky diamides). E.s.r. parameters have been derived from the isotropic spectra.
210 citations
TL;DR: The electron-rich olefin [:graphic omitted]R]2(LR2; R = Me or Et) provides a ready source of various thermally stable neutral mono-and bis-(carbene) complexes of Fe, Ru, Co, and Ni.
Abstract: The electron-rich olefin [:[graphic omitted]R]2(LR2; R = Me or Et) provrdes a ready source of various thermally stable neutral mono- and bis-(carbene) complexes of Fe, Ru, Co, and Ni and, with greater difficulty, of MnI. Noteworthy is the range of co-ordination numbers, formal metal oxidation states, and geometries (tetrahedral, square planar, trigonal bipyramidal, or octahedral) of the complexes. Amongst the 29 new complexes are the novel neutral bis(carbene) specres [Fe(LMe)2(NO)2], [Co(CO)(LEt)2(NO)], trans-[Fe(CO)3(LMe)2], [Ni(CO)2(LEt)2], [Fe(CO)2l2(LMe)2], and [Ni(LMe)2(NO3)2]; the last is the only diamagnetic nickel(II) dinitrate. Infrared spectra show that ν(CO) is low compared with analogous (e.g. phosphine) complexes: ν(CN2) is in the range 1 480–1 540 cm–1, the upper end being characteristic of the higher-oxidation state metal complexes. This trend is also observed in 13C n.m.r. chemical shifts when Ccarb. moves to higher field (Ccarb. is generally 200–230 p.p.m. downfield from SiMe4); [Ru3(CO)11 LEt] shows only one CO resonance, an indication of fluxionality, whereas [Fe2(CO)(µ-CO)2(η-C5H5)LEt] exists at 25 °C in solution as a mixture of cis and trans isomers.
140 citations
TL;DR: The mechanism of these reactions and their relevance to the action of nitrogenase is discussed in this article. But the mechanism is not discussed in detail in this paper, as discussed in Section 2.1.
Abstract: Treatment of trans-[M(N2)2(dppe)2](A)(dppe = Ph2PCH2CH2PPh2, M = Mo or W) with H2SO4 gives [M(HSO4)-(NNH2)(dppe)2][HSO4] and no ammonia or hydrazine. However, the complexes cis-[M(N2)2(PMe2Ph)4](B) and trans-[M(N2)2(PMePh2)4](C)(M = Mo or W) react with H2SO4 in methanol at 20 °C to give ammonia (ca. 1.9 NH3 per W atom and ca. 0.7 NH3 per Mo atom), together with a little hydrazine for (B; M = W) but not for (B; M = Mo). Treatment of (B; M = Mo and W) with a variety of other acids gives ammonia, but less effectively than with H2SO4. Anhydrous HBF4 also gives ammonia from (B; M = Mo or W), but (A; M = Mo or W) gives only trans-[MF(NNH2)(dppe)2][BF4]. Ammonia (1.6 NH3 per W atom) is also obtained when (B; M = W) but not (B; M = Mo) is treated with methanol alone, either at reflux or on irradiation at 20 °C for several hours. The mechanism of these reactions and their relevance to the action of nitrogenase is discussed.
115 citations
TL;DR: In this paper, the tris solvent complexes were obtained from the acetone solvent complexes (IVa; M = Rh, Ir, s = Me2CO, MeOH, or CH2Cl2) and the dicationic RhIII and IrIIIη6-arene complexes [M(C5Me5)(arene)][PF6] were obtained.
Abstract: The tris(solvent) complexes [M(C5H5)(S)3][PF6]2(M = Rh, Ir; s = Me2CN, Me2SO, or pyridine) were prepared and characterised; evidence for less stable solvent complexes (M = Rh, Ir; s = Me2CO, MeOH, or CH2Cl2) was obtained. The dicationic RhIII and IrIIIη6-arene complexes [M(C5Me5)(arene)][PF6]2(M = Rh: arene = benzene, toluene, m-xylene, mesitylene, fluorene, or indole; M = Ir, arene = toluene, m-xylene, naphthalene, phenanthrene, indene, indole, or fluorene) were synthesised from the acetone solvent complexes (IVa; M = Rh)(IVa: M = Ir). Both the naphthalene- and phenanthrene-iridium complexes were very labile, but showed no evidence of fluxional behaviour; phenanthrene is bonded by the terminal 6-membered ring. Reaction of (IVa) with indene gave the η5-indenyl complex, [Rh(C5Me5)(C9H7)][PF6], which was protonated, with rearrangement, to the η5-indene complex. Similar reversible protonation–deprotonation reactions occurred for the iridium complexes, [Ir(C5Me5)(η6-C9H8)]2+⇌[Ir(C5Me5)(η5-C9H7)]++ H+. The iridium (but not the rhodium)-indole complex [Ir(C5Me5)(η6-C8H6NH)]2+ also underwent reversible deprotonation to the η5-indolyl complex [Ir(C5Me5)(η5-C8H6N)]+. From exchange studies with CF3CO2D on [Ir(C5Me5)(η6-C7H8)]2+ it is concluded that protonation/deprotonation is fast and that the rate-determming step in the overall reaction is the movement of the metal from the 5- to the 6-membered ring and vice versa. The η6-fluorene-rhodium complex is very labile but the iridium analogue is deprotonated by base to give a fluorenyl complex of undetermined structure. An order of stability of η5- and η6-arenes bonded to RhIII and IrIII is given.
115 citations
TL;DR: In pure hydroxyapatite, the O-H stretching and librational modes give rise to i.r. bands at 3 573 and 631 cm-1 as discussed by the authors.
Abstract: In pure hydroxyapatite the O–H stretching and librational modes give rise to i.r. bands at 3 573 and 631 cm–1. On introduction of F, the band at 631 cm–1 shifts to higher wavenumbers, ultimately to 641 and 647 cm–1, and decreases in intensity. This shift can be correlated with the number n of OH groups in the chain sections between F which have the generalised form ⋯ F HO (HO)n HO:OH (OH)n OH F ⋯. The ‘tail-to-tail’ configuration, ⋯ HO:OH ⋯, gives rise to bands at 680 (bending) and 3 643 cm–1(stretching). The OH bonded to one F gives rise to bands at 720 and 3 546 cm–1. If OH is dispersed in a chain composed mainly of F, the configuration ⋯ F OH F ⋯, the O–H stretching and bending bands lie at 3 540 and 747 cm–1 respectively.
103 citations
TL;DR: The reaction of [NiL4] with CO2 in toluene affords complexes of formula [Ni(CO2)L2], via the [Ni[CO2] species as discussed by the authors.
Abstract: The reaction of [NiL4](L = PEt3 or PBun3) with CO2 in toluene affords complexes of formula [Ni(CO2)L2], via the [Ni(CO2)L3] species. The reaction of [Ni(CO2){P(C6H11)3}2]·0.75C6H5Me with O2 to give (peroxocarbonato)-bis( tricyclohexylphosphine)nickel(II) is also reported.
85 citations
TL;DR: In this article, the interaction of chlorohydridotris(triphenylphosphine)ruthenium(II) with NaOH or KOH in tetrahydrofuran, acetone, or t-butyl alcohol leads, depending on conditions, to red, five-coordinate complexes RuH(OH)(PPh3)2(sol)(sol = thf or H2O) secondly to hydroxo-bridged dimers, and thirdly to a tetranuclear complex of stoicheiometry Ru4H4(OH
Abstract: The interaction of chlorohydridotris(triphenylphosphine)ruthenium(II) with NaOH or KOH in tetrahydrofuran, acetone, or t-butyl alcohol leads, depending on conditions, first to red, five-co-ordinate complexes RuH(OH)(PPh3)2(sol)(sol = thf or H2O) secondly to hydroxo-bridged dimers, (PPh3)2H(sol)Ru(µ-OH)2Ru(sol)H(PPh3)2(sol = Me2CO, H2O, or ButOH) and thirdly to a tetranuclear complex of stoicheiometry Ru4H4(OH)2(PPh2)2(CO)2(PPh3)6(Me2CO)2.Interaction of dichlorotris(triphenylphosphine)ruthenium(II) with KOH gives similar compounds, RuCl(OH)(PPh3)2(sol)2 and {RuCl(OH)(PPh3)2(sol)}2(sol = H2O or thf) as well as {RuH(OH)(PPh3)2(thf)}2.The interaction of RuHCl(PPh3)3 with sodium methoxide gives rise to two compounds that are formulated, respectively as having Ru–CHO and Ru–OCH2 groups, The mechanism of decarbonylation of alcohols is discussed and the compounds RuH2(CO)(PPh3)2·ROH (R = Me or Et) are synthesised.I.r. and 1H and 31P n.m.r. spectra of the various complexes are given and structures for the compounds proposed on this basis.
83 citations
TL;DR: In this paper, the structural identity of tris(bicyclo-[2.1]heptene)platinum has been established by analysis of single-crystal X-ray data recorded on a four-circle diffractometer both at room temperature and at 190 K.
Abstract: Reaction of [Pt(1,5-C8H12)Cl2] with Li2(C8H8) in diethyl ether in the presence of excess of 1,5-C8H12 gives the white crystalline complex [Pt(1,5-C8H12)2] in good yield. A similar reaction of [Pd(1,5-C8H12)Cl2] in the presence of propene affords [Pd(1.5-C8H12)2]. stable below ambient temperatures. The reaction of [M(1,5-C8H12)Cl2](M = Pd or Pt) with Li2(C8H8) and excess of bicyclo[2.2.1]heptene gives, respectively, tris(bicyclo[2.2.1]heptene)- palladium and -platinum. These complexes are also obtained by displacement of cyclo-octa-1,5-diene from [M(1,5-C8H12)2](M = Pd or Pt) by bicyclo[2.2.1]heptene. Related displacement reactions with trans-cyclo-octene and ethylene afford, respectively, tris(trans-cyclo-octene)palladium, tris(trans-cyclo-octene)platinum. tris(ethylene)palladium, and tris(ethylene)platinum. The ethylene complexes are highly volatile, and can be isolated as crystalline species, although they readily deposit the metals. The structural identity of tris(bicyclo-[2.2.1]heptene)platinum has been established by analysis of single-crystal X-ray data recorded on a four-circle diffractometer both at room temperature and at 190 K. The complex is orthorhombic, space group P212121. Z= 4, a= 5.717(1), b= 10.735(4), c= 28.749(12)A, at 300 K: at 190 K a= 5.598(6), b= 10.775(16), c= 28.562(40)A. Full-matrix least-squares refinement, using 1 781 reflections, has converged to R 0.056 (R′ 0.066)(190 K data). The molecule has a trigonal-planar structure in which the maximum deviation from planarity is 0.03 A.
82 citations
TL;DR: Stereoselectivity is significant in the non-protonated ternary complex, that with ligands of opposite chirality being more stable, and may be explained by simple electrostatic interactions.
Abstract: Formation constants of the parent and ternary complexes of general formula [CuII(D/L-HisO)(L-A)](HisO = histidinate; HA = phenylalanine, tryptophan, valine, proline, methionine, leucine, serine, threonine, 2,4-diaminobutyric acid, ornithine, lysine, arginine, glutamic acid, aspartic acid, glycylvaline, glycylphenylalanine, or valyl-L-valine) have been measured potentiometrically at 25.0 °C and I= 0.10 mol dm–3(K[NO3]). The ternary systems of CuII and the substituted histidines N3-benzyl-L-histidine and NαN3-dibenzyl-L-histidine with D- and L-tryptophan, phenylalanine, valine, and glutamic acid have also been studied. The ternary complexes containing tryptophan and phenylalanine are unusually stable, complexes containing ligands of opposite chirality being significantly more stable than those with ligands of the same chirality. With ornithine, lysine, and arginine, stereoselectivity is significant in monoprotonated ternary complexes, those with ligands of the same chirality being more stable. This stereoselectivity is at a maximum at ca. pH 6 and vanishes when the proton is ionized. With aspartic acid, stereoselectivity is significant in the non-protonated ternary complex, that with ligands of opposite chirality being more stable. The stereoselectivity found may be explained by simple electrostatic interactions.
69 citations
TL;DR: In this paper, the structures of three square-planar rhodium complexes were determined by a three-dimensional X-ray study from diffractometer data (Mo-Kα radiation) using Patterson and Fourier methods and refined by full-matrix least squares to R 0.048 (1), 0.039 (2), and 0.022 (3) for 1 603, 1 327, and 4 586 independent observations respectively.
Abstract: The complexes [RhCl(N2)(PPri3)2](1), [RhCl(O2)(PPri3)2](2), [RhCl(C2H4)(PPri3)2](3), and [RhCl(CO)-(PPri3)2](4) have been prepared. The crystal structures of (1)–(3) have been determined by a three-dimensional X-ray study from diffractometer data (Mo-Kα radiation). Crystals of the three complexes are monoclinic, space group P21/c, with the following unit-cell dimensions: (1), a= 8.156(1), b= 8.935(2), c= 16.695(5)A, β= 93.5(1)°, Z= 2; (2), a= 8.184(3), b= 9.001(4), c= 16.401(7)A, β= 93.1(1)°, Z= 2; (3), a 16.316(3), b= 9.164(2), c= 16.544(3)A, β= 93.8(1)°, Z= 4. The structures have been solved by Patterson and Fourier methods and refined by full-matrix least squares to R 0.048 (1), 0.039 (2), and 0.022 (3) for 1 603, 1 327, and 4 586 independent observations respectively. The three complexes show similar molecular structures: the rhodium atom displays square-planar co-ordination with the two phosphines in trans positions and the N2, O2, and C2H4 ligands bonded side-on to the metal atom. The molecules of (1) and (2) lie on crystallographic centres of symmetry with a consequent disordered disposition of the chlorine atoms and N2 or O2 ligands. Short N–N [0.83(2)A] and O–O [ 1.03(1)A], and long Rh–N [2.51(1)A] and Rh–O [2.28(1), 2.28(1)A] bond distances are observed, which are scarcely significant because of the disorder. Infrared spectra are in accord, with weak Rh–N2 and Rh–O2 interactions, on the basis of the relatively high values of the N–N and O–O stretching frequencies. The 1H n.m.r. spectrum of C2H4 in (3) shows that the ethylene co-ordination is similar to that of other square-planar rhodium complexes. The C–C [1.319(4)A] and Rh–C [2.116(2), 2.128(2)A] distances are also close to those observed in other square-planar complexes. The three complexes represent the first case of a homogeneous series containing the three ligands N2, O2, and C2H4 and the first example of four-co-ordinate complexes containing ‘side-on’ dinitrogen and dioxygen.
TL;DR: Cyclohexadiene reacts with [Os3(CO)10H2] under moderate conditions to give [Os( CO)10(C6H8] as discussed by the authors.
Abstract: Cyclohexadiene reacts with [Os3(CO)10H2] under moderate conditions to give [Os(CO)10(C6H8)]. Some reactions of this compound with alcohols, thiols, amines, halogen and organic acids, ethylenes, and acetylenes have been examined, and it is shown that cyclohexa-1,3-diene is a very good ‘leaving group’ and provides a convenient route to a number of triangulo-Os3 cluster compounds.
TL;DR: In this paper, the crystal and molecular structures of [La{N(SiMe3)2}3(PPh3O)](1) and [La2{NSiMe 3]4(O2)(PPh 3O)2] have been determined by single-crystal X-ray diffraction methods from data measured on a manual diffractometer and refined by least-squares to R 0.116 for 2 770 observed reflections for (1).
Abstract: The preparation, properties, and n.m.r. spectra of 1 : 1 triphenylphosphine oxide adducts of [M{N(SiMe3)2}3](M = La Eu, or Lu) and dimeric peroxo-species [M2{N(SiMe3)2}4(O2)(PPh3O)2](M = La, Pr, Sm, Eu, or Lu) are described. The crystal and molecular structures of [La{N(SiMe3)2}3(PPh3O)](1) and [La2{N(SiMe3)2}4(O2)(PPh3O)2](2) have been determined bysingle-crystal X-ray diffraction methods from data measured on a manual diffractometer and refined by least-squares to R 0.116 for 2 770 observed reflections for (1) and to R 0.113 for 2 153 data for (2). Both species crystallise in space group P with cell parameters: (1); a= 19.92, b= 12.64, c= 12.48 A, α= 120.5, β= 87.3, γ= 102.7°, Z= 2; (2); a= 13.55, b= 18.54, c= 12.54 Aα= 90.8, β= 121.7, γ= 115.3°, Z= 1. Complex (1) is monomeric and the lanthanum atom has slightly distorted LaN3O tetrahedral geometry. The La–O–P unit is almost linear, with La–O 2.39(2)A; La–N distances are 2.38(2)–2.41(2)A. Complex (2) is a peroxo-bridged centrosymmetric dimer in which the peroxo-function acts as a symmetrical doubly bidentate bridge linking two La{N(SiMe3)2}2(PPh3O) units. The metal atom can again be considered to have distorted tetrahedral co-ordination if the O2 function is assumed to occupy one co-ordination site. The La–O(O2) distances are both 2.33(3)A, whilst La–O(PPh3O) is 2.42(2) and La–N 2.37(2) and 2.49(3)A. The O–O separation is 1.65(4)A, but this may be artificially lengthened by the effects of crystal decomposition.
TL;DR: In this paper, the temperature-dependent 1H and 13C n.m. spectra of the complexes [Pd(η3-all)(η4-diene)]-[PF6][all = C3H5, 1 -MeC3H4, 2-MeC 3 H4 or 2-PhC3 H4, diene = cycle-octatetraene (cot), hexamethylbicyclohexa[2.0]diene (hmdb), hexa-1,5 diene ∼
Abstract: The syntheses, and the temperature-dependent 1H and 13C n.m.r. spectra of the complexes [Pd(η3-all)(η4-diene)]-[PF6][all = C3H5, 1 -MeC3H4, 2-MeC3 H4, or 2-PhC3H4, diene = cycle-octatetraene (cot) : all = 2-MeC3H4, diene = cycle-octa-1.5-diene (cod), hexamethylbicyclohexa[2.2.0]diene (hmdb), hexa-1,5-diene, or cyclo-heptatriene], [Pt(η3-2-MeC3H4)Cl]2, and [Pt(η3-2-MeC3H4)(η4-diene)][PF6][diene = cot or cod] are reported. The platinum complexes are rigid at low temperatures but undergo η3→η1→η3 exchange on heating. The palladium complexes exhibit different behaviour; for the cot complexes the observations are consistent with a higher temperature exchange process involving solvent, [Pd(all)(cot)]++ s ⇌ cot +[Pd(all)(s)2]+, and a lower energy process which could not be frozen out and which is interpreted in terms of a solvated five-co-ordinate intermediate undergoing pseudorotation in which the two halves of the cot are made equivalent. The η-arene complexes [M(2-MeC3H4)(hmb)][PF6](M = Pd or Pt, hmb = hexamethylbenzene) have been prepared and their structures are discussed on the basis of their n.m.r. spectra. A stability sequence towards solvation by acetone for the palladium complexes is, cot ∼ cod > hmdb > hexa-1,5 diene ∼ cht ∼ hmb; the Pt complexes are less stable than their Pd analogues.
TL;DR: In this article, a complex of Ph2P[CH2]2PPh2 with co-ordinated diene has been obtained, and the corresponding rhodium(III) complexes.
Abstract: Reactions of [Rh2(cod)2Cl2](cod = cyclo-octa-1,5-diene) with CO and PXPh2(X = Et or Cl), Ph2P[CH2]nPPh2(n= 1–4), 4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxoiane (bdmo), cis-Ph2PCH:CHPPh2, Ph2As[CH2]2AsPh2, (Ph2PCH2)3CMe, or P(CH2CH2PPh2)2Ph, give trans-[Rh(CO)Cl(PXPh2)2], [{Rh(CO)Cl(Ph2P[CH2]nPPh2)}m](m= 1, n= 2; m= 2, n= 1, 3, or 4). or related complexes. Under different conditions, a complex of Ph2P[CH2]2PPh2 with co-ordinated diene has been obtained. An excess of Ph2P[CH2]nPPh2 gives [{Rh(Ph2P[CH2]nPPh2)2}Cl](n= 2) or [{Rh(CO)(Ph2P[CH2]nPPh2)2}Cl](n= 3 or 4). Reactions of these complexes of RhI with Cl2, HCl, or Mel normally give the corresponding rhodium(III) complexes. Assignments of i.r. and 31P n.m.r. spectral parameters have been made by internal comparisons or by comparison with the bromo-complexes, prepared by halogen-exchange reactions.
TL;DR: In this article, the results of 13C n.m.r. and Raman studies are reported for [AuCl(CO), [PtX3(CO)] and [PdX3[CO] together with assignments.
Abstract: Detailed i.r. and Raman studies are reported for [AuCl(CO)], [PtX3(CO)]–(X = Cl, Br, or I), [PdX3(CO)]–, cis-[PtX2(CO)2], cis-[RhX2(CO)2]–(X = Cl or Br), and cis-[IrCl2(CO)2]– together with assignments. Skeletal stretching wavenumbers are reported for cis-[PtX2(CO)(PMe3)](X = Cl, Br, or I), trans-[PtX(CO)(PMe3)2]+, trans-[RhX(CO)(PMe3)2](X = Cl or Br), and [RhCl3(CO)(PMe3)2]. The results of 13C n.m.r. studies on the carbony complexes are reported together with those from 1H n.m.r. and 1H-{31p} and 1H-{195Pt} INDOR spectroscopy on the phosphine-containing complexes. The 195Pt chemical shifts of [PtX3(CO)]– from direct measurements are reported. The results are discussed with the assistance of stretching force constants for some of the simpler complexes.
TL;DR: In this article, the stability constants of ZnII, PbII, and CdII with 12- to 15-membered macrocyclic tetra-amines were determined.
Abstract: Polarographic methods have been used to determine the equilibria and kinetics of reaction of ZnII, PbII, and CdII with 12- to 15-membered macrocyclic tetra-amines including 1,4,7,10-tetra-azacyclododecane (L1), 1,4,7,10-tetra-azacyclotridecane (L2), 1,4,8,11-tetra-azacyclotetradecane (L3), and 1,4,8,12-tetra-azacyciopentadecane (L4) in acetate buffer solutions. Unlike the copper(II) system. the stability constants of the zinc complexes hardly change with macrocyclic ring size : log KZnL= 16.2, 15.6, 15.5, and 15.0 for L1, L2, L3, and L4, respectively (I0.20 mol dm–3 and 25 °C). The much larger CdII and PbII form complexes only with L1: log KCdL 14.3 and log KPbL, 15.9. The 103–105 times greater stabilities of the macrocyclic complexes compared with the related complexes of linear terra-amines are all due to favourable entropy changes, regardless of the metal-ion size. The rate law for complex formation in acetate buffers is d[ML]/dt=kH[M(O2CMe)+][HL+]+k2H[M(O2CMe)+][H2L2+] for all the metal ions. A comparison with reactions of CuII and L1–L4 shows that the values of kH parallel the well established rates of water exchange of the aquametal ions.
TL;DR: In this article, the structural identity of [Pt3(ButNC)6] has been established by analysis of single-crystal X-ray data recorded at room temperature on a four-circle diffractometer.
Abstract: Reaction of t-butyl isocyanide with bis(cyclo-octa-1,5-diene)platinum gives the orange crystalline complex [Pt3(ButNC)6] in essentially quantitative yield. Methyl, ethyl, and cyclohexyl isocyanides react with [Pt(1,5-C8H12)2] in a similar manner to give [Pt3(RNC)6](R = Me, Et, or C6H11). The structural identity of [Pt3(ButNC)6] has been established by analysis of single-crystal X-ray data recorded at room temperature on a four-circle diffractometer. The complex is monoclinic, space group P21/n, Z= 4, a= 18.213(7), b= 11.811 (5), c= 21.996(6)A, β= 110·21(3)°. Using 3 543 reflections, the refinement has converged to R 0.057 (R′0.070). The molecule contains an essentially equilateral triangle of platinum atoms each of which carries a terminal isocyanide ligand, with the remaining three isocyanide groups bridging the sides of the triangle. The former are effectively linear and the latter bent [CNC(mean) 132.7°]. The platinum atoms and the six attached carbon atoms are effectively coplanar with maximum deviation 0.08 A. Hydrogen-1 and 13C n.m.r. studies between room temperature and 120 °C reveal that [Pt3(ButNC)6] undergoes dynamic behaviour via an intermolecular process involving terminal and bridge isocyanide site exchange catalysed by free ligand.
TL;DR: The electron-rich olefin this paper was shown to be in an approximately octahedral environment, with the mutually-trans CO ligands having Cr-C bond lengths of 190 A compared to 182 A of those cis; the CC bond length is 134 A and there is probably little interaction with the Cr atom.
Abstract: The electron-rich olefin [:[graphic omitted]R]2, LR2, (R = Me or Et), reacts thermally with (a)[Cr(CO)6], forming [Cr(CO)5LR][(1) or (2)] or cis-[Cr(CO)4(LR2),][(3) or (4)] or(b)[Cr(η-C6H6)(CO)3], yielding [Cr(η-C6H6)(CO)2LMe], (5): [Cr(CO)5LMe], (1), forms the mixed ligand complexes cis-[Cr(AsPh3)(CO)4LMe], (6) or cis-[Cr(CO)4{C(OMe)Me}LMe], (7), upon treatment with AsPh3, or LiMe and then MeOSO2F, respectively The related olefins [:[graphic omitted]Me]2(L′Me2) and [:C(NMe2)2]2(tdae) do not afford carbene complexes with Cr0 From [M(CO)4(bhd)](M = Cr, MO, or W; bhd = bicyclo[221]hepta-2,5-dtene) each of the three olefins readily affords heteroatom-donor-olefln species [M(CO)4(olefin-NN″)] For M = MO, the latter is transformed thermally into the N′N″-carbenemolybdenum complexes, only for olefin = LMe2, but not for L′Me2 or tdae Attempted in situ syntheses of metal complexes of LH2 or LH–LEt[from HC(OMe)2NMe2, and H2NCH2CH2NH2 or H2NCH2CH2NHEt, and a MO0 or RhI reagent] lead instead to 2-imidazoline [N[graphic omitted]H2](R = H or Et)N-bonded complexes of Mo0 and RhI Carbon-13 nmr (but also ir and 1H nmr) spectra are diagnostic for differentiating the type of complex (carbene, olefln-N,N″, or imidazoline) and its stereochemistry The crystal and molecular structure of [Cr(CO)4(LMe-NN″)] shows the metal to be in an approximately octahedral environment: the mutually-trans CO ligands are bent away from the olefin fragment and have Cr–C bond lengths of 190 A compared to 182 A of those cis; the CC bond length is 134 A and there is probably little interaction with the Cr atom, the distance of closest approach being ca 30 A
TL;DR: In this article, an X-ray crystal-structure determination at −40 °C was performed, showing that the complex consists of discrete centrosymmetric units containing a square plane of copper atoms with the methylene carbons lying in the same plane and bridging the edges.
Abstract: Interaction of Li(CH2SiMe3) with Cul gives [{Cu(CH2SiMe3)}4] a thermally stable, light-petroleum-soluble, colourless copper(I) alkyl, which by cryoscopy is a tetramer in benzene and a hexamer in cyclohexane. An X-ray crystal-structure determination at –40 °C shows that the complex consists of discrete centrosymmetric units containing a square plane of copper atoms with the methylene carbons lying in the same plane and bridging the edges. Crystals are monoclinic with a= 6.355(4), b= 12.636(7), c= 17.938(11)A, β= 90.84(5)°, space group P21/c. Relevant distances and angles are: Cu–Cu 2.417 and Cu–C (mean) 2.02 A; Cu–Cu–Cu 89.8, 90.2, Cu–C–Cu (mean) 73.5, and C–Cu–C (mean) 163.5°. Decomposition (thermal or photochemical) occurs via a homolytic path. Reactions with some organic halides (C3H5Br, Phl, SiMe3Cl, or PhCH2Br) are outlined, showing for the most part simple metathetical X–CH2SiMe3 exchanae, but less readily than with alkyls of Li or Mg. Addition of Li(CH2SiMe3) appears to yield Li[Cu(CH2SiMe3)2].
TL;DR: In this paper, it was shown that the trans-carbonyl complex of Ph2P[CH2]2PPh2 is [Ir(CO)Cl(diphosphine)] 2 ].
Abstract: Diphosphines Ph2P[CH2]nPPh2(n= 1–4) form novel trans-carbonyl complexes of IrI of stoicheiometry[{Ir(CO)Cl(diphosphine)}m] in which the diphosphine (n= 1,3, or 4) bridges the metal atoms. Contrary to a previous postulate, the complex of Ph2P[CH2]2PPh2 is [Ir(CO){Ph2P(CH2)2PPh2}2][Ir(CO)2Cl2]. The diphosphine complexes of PdII and PtII, some of which are described for the first time, are each of cis geometry. In each case Ph2P[CH2]2PPh2 chelates the metal and the complex is mononuclear, but Ph2P[CH2]4PPh2 bridges metal atoms of trinuclesr complexes. The diphosphine Ph2P[CH2]3PPh2 chelates PdII but forms a bridaed complex of PtII. Bridging by a diphosphine ligand occurs when the angle PMP which would be sub-tended by a chelating ligand exceeds 90°.
TL;DR: The reactivity of dinitrogen in its complexes decreases along the third transition series in the order W > Re > Os. as mentioned in this paper showed that in [OsCl2(N2)(PMe2Ph)4] dinitrogens are inactive even to acid chlorides.
Abstract: The reactions of [M(N2)2(dppe)2][M = MO or W; dppe = 1,2-bis(diphenylphosphino)ethane] with alkyl bromides, acyl chlorides, or aroyl chlorides, under irradiation, lead to organohydrazido(2–)- and organodiazenido-complexes. Complexes [ReCl(N2)(PMe2Ph)4] and [ReCl(N2)(py)(PMe2Ph)3](py = pyridine) can be acylated but not alkylated at the dinitrogen, but in [OsCl2(N2)(PMe2Ph)4] dinitrogen is inactive even to acid chlorides. The reactivity of dinitrogen in its complexes decreases along the third Transition Series in the order W > Re > Os.
TL;DR: In this article, the crystal and molecular structure of uranyl diperchlorate heptahydrate, UO2[ClO4]2·7H2O, has been determined by single-crystal X-ray methods.
Abstract: The crystal and molecular structure of uranyl diperchlorate heptahydrate, UO2[ClO4]2·7H2O, has been determined by single-crystal X-ray methods. The crystals are orthorhombic, space group Pca21, with unit-cell dimensions a= 9.302(4), b= 14.692(6), and c= 10.842(5)A, Z= 4. 493 Reflections have been measured by a diffractometer and the structure solved by heavy-atom methods to R 0.046. The crystal contains [UO2(OH2)5]2+,2[ClO4]–, and 2H2O in each asymmetric unit, held together by hydrogen bonds. The uranium has pentagonal-bipyramidal co-ordination with U–O(uranyl) of 1.71 A(average), U–O(aqua) of 2.45 A(average), and O ⋯ O contacts of 2.88 A.
TL;DR: In this paper, the thermal decomposition of complexes cis-PtR2L2 [R = Ph or C6H4Me-4; L2=(PPh3)2, {P(C6H 4Me)-4}2, Ph2PCH2PPh2.
Abstract: The thermal decompositions of complexes cis-[PtR2L2][R = Ph or C6H4Me-4; L2=(PPh3)2, {P(C6H4Me-4)3}2, (PMePh2)2, Ph2PCH2PPh2, Ph2PCH2CH2PPh2, or Me2PCH2CH2PMe2] in toluene solution have been investigated. Their stability to thermolysis varies markedly with L2, and only complexes of monotertiary phosphines are labile at 60 °C. Reaction occurs via primary concerted unimolecular reductive elimination of biaryl, and conforms to a first-order kinetic rate law. Concurrent but independent secondary decomposition of [PtL2] generates both arene and biaryl as minor products. The elimination of 4,4′-bitolyl from cis-[Pt(C6H4Me-4)2(PPh3)2] exhibits a pronounced negative entropy of activation, suggestive of a conformationally restricted transition state. The inclusion of free PPh3 suppresses secondary processes and accelerates primary decay. Although itself inert under these conditions, [PtR2(Ph2PCH2PPh2)] also eliminates biaryl in a concerted and kinetically first-order manner when allowed to react in the presence of 10 equivs. of Ph2PCH2PPh2. These observations provide further evidence for the facilitation of reductive elimination by added nucleophiles.
TL;DR: In this article, the diamine chelate ring is discussed in relation to the coordination number of the metal ion (M = VIV, FeIII, CoII, CoIII, NiII, or CuII).
Abstract: The circular dichroism (c.d.) spectra of some transition-metal complexes of quadridentate Schiff bases derived from the condensation of 2 mol of salicylaldehyde with optically active (+)-(S)-propylene-1,2-diamine, (+)-(SS)-butane-2,3-diamine, trans-(+)-(SS)-cyclohexane-1,2-diamine, (+)-(S)-1 -phenylethylenediamine, and (–)-(SS)-1,2-diphenylethylenediamine are reported. The conformational behaviour of the diamine chelate ring is discussed in relation to the co-ordination number of the metal ion (M = VIV, FeIII, CoII, CoIII, NiII, or CuII). The assignment of the SS absolute configuration to (–)-1,2-diphenylethylenediamine has been confirmed. The anomalies in the c.d. spectra of metal complexes of Schiff bases containing this diamine are discussed.
TL;DR: The structures of the title compounds have been determined as mentioned in this paper, and three compounds are isomorphous, monoclinic, space group C2/c, Z= 8, with the following cell constants and R values: [graphic omitted] In the dimeric structures Ph2I(µ-X)2Iph2 mean bond lengths are I−C 2.09, i−Cl 3.25, and I−I 3.44 A, The I−X bonds are each 0.77 A longer than in the corresponding IX gas, indicating
Abstract: The structures of the title compounds have been determined. The three compounds are isomorphous, monoclinic, space group C2/c, Z= 8, with the following cell constants and R values: [graphic omitted] In the dimeric structures Ph2I(µ-X)2Iph2 mean bond lengths are I–C 2.09, i–Cl 3.09, I–Br 3.25, and I–I 3.44 A, The I–X bonds are each 0.77 A longer than in the corresponding IX gas, indicating bond orders of about 0.35. The bonding is interpreted in terms of secondary bonds (I ⋯ X). holding [Ph2I]+ and X– units together.
TL;DR: In this article, the 1H and 31P n.r.m. and vibrational spectra of PtI and PtII complexes are analyzed and strongly support the assigned structure rather than the halogenide-bridged structure proposed earlier.
Abstract: Bis-µ-[bis(diphenylphosphino)methane]-bis(chloroplatinum)(Pt–Pt), [{PtCl(dppm)}2](dppm = Ph2PCH2PPh2), is obtained by treatment of the platinum(II) complex [PtCl2(dppm)] with Na[BH4]–MeOH followed by HCl–C6H6. The corresponding dimeric bromo- and iodo-complexes of PtI are obtained from the chloro-complex by halide exchange. The 1H and 31P n.m.r. and vibrational spectra of these complexes are analysed and strongly support the assigned structure rather than the halogenide-bridged structure proposed earlier. Bands assigned to ν(Pt–Pt) are present in the Raman spectra.
TL;DR: In this article, the He(I) and He(II) photoelectron spectra of [M(η-C8H8)2] have been recorded and the bonding in these molecules is discussed and it is proposed that the major stabilizing interaction is between the ring e2π and the metal 6d orbitals.
Abstract: The He(I) and He(II) photoelectron spectra of [M(η-C8H8)2](M = Th and U) have been recorded. Ionization of 5f electrons is identified and their relative cross-section is shown to increase when the ionizing radiation is changed from He(I) to He(II). The bonding in these molecules is discussed and it is proposed that the major stabilizing interaction is between the ring e2(π) and the metal 6d orbitals. Significant f-orbital covalency is also demonstrated.
TL;DR: Extended-Huckel molecular-orbital calculations are reported for the icosahedrel platinaboranes and carbaboranes [B11{Pt(PH3)2}H11]2] as discussed by the authors.
Abstract: Extended-Huckel molecular-orbital calculations are reported for the icosahedrel platinaboranes and carbaboranes [B11{Pt(PH3)2}H11]2–, [B10C{Pt(PH3)2}H11]–, and B9C2[Pt(PH3)2]H11. The failure of the polyhedral skeletal electron-counting rules when applied to carbaplatinaboranes is discussed, and attributed to the unequal bonding capabilities of the platinum 5dxz and 5dyz orbitals in the Pt(PH3)2 fragment. The conformations of icosahedral carbaplatinaboranes are rationalised on the basis of the symmetry characteristics of the lowest-unoccupied orbital of thecarbaboraneand the highest-occupied orbital ofthe metal-phosphine moiety. Analogous d8 metal compounds are predicted to be stable and expected to have conformations which are complementary to those observed for d10 metal compounds.
TL;DR: In this paper, the dihedral angles between the carbene ligand and the coordination planes are ca 45° 45° a σ σ involved, which is a strong σ-acceptance for carbene-Moo complexes.
Abstract: Carbene–Moo complexes are obtained by the thermal reaction of an electron-rich olefin [graphic omitted]R]2, LR2, with (a)[Mo(CO)6]{yielding [Mo(CO)5LR] or cis-[Mo(CO)4(LR)2](R = Me, Et, or PhCH2)(the tricarbene complex is unstable)}, and (b)[Mo(CO)2(C5H5-η)NO]{yielding [Mo(CO)(C5H5-η(LR)NO](R = Me or p-tol)}. By contrast, with [Mo(CO)3(C5H5-η)H] or [{Mo(CO)3(C5H5-η)}2], the olefin reacts as a reducing agent, yielding the amidinium molybdate(0) complexes [HLR]+[Mo(CO)3(C5H5-η)]– or [LR2]2+[Mo(CO)3(C5H5-η)]–2(R = Me). The six-membered chelate olefin [C[graphic omitted]Me]2, L′Me2, behaves qualitatively in a similar fashion, but is less reactive, dicarbene–Moo complexes not being accessible. The cis-dicarbene–Moo complexes are isomerised photochemically to the trans-complexes, but the former are thermodynamically the more stable. Reaction of [Mo(CO)5LEt] with LMe2 yields cis-[Mo(CO)4(LEt)(LMe)], whereas [Mo(CO)5LMe)] with LEt2 affords also cis-[Mo(CO)4(LMe)2] and cis-[Mo(CO)4(LEt)2]. The redistribution reaction cis-[Mo(CO)4(LR)2]+[Mo(CO)6]⇌ 2[Mo(CO)5LR](R = Me or Et) is reversible. Other reactions of monocarbene complexes give cis-[Mo(CO)4(LR)Q][Q = C5H5N, PPh3, or P(C6H11)3, fac-[Mo(CO)3(LR)Q′2][Q′2={P(OMe)3}2 or diphos], or cis-[Mo(CO)4{C(OMe)Me}LR]. ν(CN2) is at 1 510—1 480 cm–1 for the carbene–Moo complexes, but at 1 700–1 640 cm–1 for the amidinium cations, and ν(CO) values are very low; 1H n.m.r. spectra provide information on conformational aspects; ΔG‡ for Mo–Ccarb rotation in cis-[Mo(CO)4(LR)2] is ca. 10 kcal mol–1. 13C Chemical shifts for Ccarb. and CO are comparable (but are distinguished by 1H decoupling and 1H off-resonance studies). Both are in the range 230–210 p.p.m. upfield from SiMe4, whereas for [HLMe]+ or [LMe2]2+ there is a further 50–60 p.p.m. upfield shift for δ[Ccarbonium ion]. A single-crystal X-ray analysis of (4)cis-[Mo(CO)4(LMe)2] shows octahedral Mo, with MO–CO mutually-trans bond lengths longer by 0.048(2)A than MO–CO trans to carbene [2.024(3) and 2.032(3)A]; Mo–Ccarb[2.293(3)A] is appropriate for single bonds. The dihedral angles between the carbene ligand planes and the co-ordination planes in which they are involved are ca. 45°, which is sterically the preferred conformation. It is concluded that the carbene ligand is a strong σ-donor but a poor π-acceptor.