Preparation and characterisation of cobalt (l) acyl compounds

The new cobalt (l) acyl compounds, [Co(PMe₃)(CO)₃(COMe)] 1, [Co(PPhMe₂)(CO)₃(COMe)] 2, [Co(P(4-Me-C₆H₄)₃)(CO)₃(COMe)] 3 and [Co(P(4-F-C₆H₄)₃)(CO)₃(COMe)] 4, have been prepared from [Na(Co(CO)₄)]. The compound [Co(PCy₃)(CO)₃(COMe)] 5 has been prepared from [Co(PCy₃)(CO)₃(Me)] 6. The crystal structures of 5 and 6 are reported.     

The first rare earth organometallic complex of 1,4,7-trithiacyclononane: a precursor to unique cationic ethylene and alpha-olefin polymerisation catalysts supported by an all-sulfur donor ligand

[Sc([9]aneS3)(CH2SiMe3)3], the first rare earth organometallic complex of 1,4,7-trithiacyclonane, is a precursor to ethylene and alpha-olefin polymerisation catalysts upon activation with BAr(F)3 or [CPh3][BAr(F)4](Ar(F) = C6F5); these are the first cationic rare earth organometallic catalysts supported by an all-sulfur donor ligand.     

Triplet-Triplet Absorption Spectroscopy of Some Highly Dipolar Unsaturated Nitro Compounds

The triplet-triplet absorption spectra of p-N, N-dimethylnitroaniline, 4-nitro-p-terphenyl, 1-amino-4-nitrofluorene, 5-nitroacenaphthene, trans-1-(4-methoxy-phenyl)-2-nitroethylene (MeONS), and trans-1-(4-dimethylaminophenyl)-2-nitroethylene (DANS) in EPA glass at 77 K are reported, together with molar extinction coefficients and PPP-SCF-MO-CI calculations. The two nitrostyrenes, MeONS and DANS, have been examined in fluid media at room temperature using nanosecond laser photolysis, and their triplet lifetimes found to increase substantially with increase in solvent polarity and charge-transfer character of the compound. This is interpreted in terms of the diradical/zwitterionic nature of the triplet state affecting the T₁–S₀ energy gap at the 90° twisted configuration of the olefinic linkage. The decrease in both the triplet yield and the fluorescence yield of DANS with increase in solvent polarity is explained by the intervention of an internal conversion process involving a rotation of the dimethylamino group in the lowest singlet excited state.     

The (p, 2p) reaction on 2H, 3He and 4He

The (p, 2p) cross sections on ²H, ³He and ⁴He were measured at 65, 85 and 100 MeV. The experimental data show rather strong energy and target mass dependence, particularly for ⁴He.     

Co-existence of long- and short-range magnetic correlations in holmium-erbium superlattices

The effect of competing crystal-field anisotropies on magnetic order has been investigated in a series of Ho/Er superlattices using a combination of x-ray and neutron scattering techniques. For temperatures in the interval T_N(Er)≤T≤T_N(Ho) the Ho basal-plane order propagates coherently through the paramagnetic Er over a typical length scale of 1000 Å. At low temperatures the Ho moments retain their bulk-like helical configuration, whereas the magnetic structure in the Er blocks has both basal-plane and c-axis components. Below T_N(Er), the coherence length of the basal-plane order decreases on cooling, while the longitudinal component of the Er moments fails to order across the Ho block. It is argued that these results require an extension of current models of indirect exchange in superlattices to explicitly include the superlattice band structure.     

Complexes of 1,2-bis(aryl-imino)acenaphthene (Ar-BIAN) ligands with some heavy p-block elements

The new Ar-BIAN complexes [(mes-BIAN)InCl(3)(THF)] (1), [(mes-BIAN)(2)Tl][PF(6)] (2), [(dipp-BIAN)SnCl(4)] (3), [(dipp-BIAN)SbCl(3)] (4), [(dipp-BIAN)BiCl(3)] (5) and [(mes-BIAN)BiCl(3)] (6) have been prepared by treatment of the neutral mes- and dipp-substituted BIAN ligands with the p-block reagents InCl(3), TlPF(6), SnCl(4), SbCl(3), and BiCl(3). The molecular structures of complexes 1-6 have been determined by single-crystal X-ray diffraction methods. However, only the atom connectivity was established for 5.     

B(C6F5)3 adducts of transition metal acyl compounds

The transition metal acyl compounds [Co(L)(CO)3(COMe)] (L = PMe3, PPhMe2, P(4-Me-C6H4)3, PPh3 and P(4-F-C6H4)3), [Mn(CO)5(COMe)] and [Mo(PPh3)(eta(5)-C5H5)(CO)2(COMe)] react with B(C6F5)3 to form the adducts [Co(L)(CO)3(C{OB(C6F5)3}Me)] (L = PMe3, 1, PPhMe2, 2, P(4-Me-C6H4)3, 3, PPh3, 4, P(4-F-C6H4)3), 5, [Mn(CO)5(C{OB(C6F5)3}Me)] 6 and [Mo(eta(5)-C5H5)(PPh3)(CO)2(C{OB(C6F5)3}Me)], 7. Addition of B(C6F5)3 to a cooled solution of [Mo(eta(5)-C5H5)(CO)3(Me)], under an atmosphere of CO gave [Mo(eta(5)-C5H5)(CO)3(C{OB(C6F5)3}Me)] 8. In the presence of adventitious water, the compound [Co{HOB(C6F5)3}2{OP(4-F-C6H4)3}2] 9, was formed from [Co(P(4-F-C6H4)3)(CO)3(C{OB(C6F5)3}Me)]. The compounds 4 and 9 have been structurally characterised. The use of B(C6F5)3 as a catalyst for the CO-induced migratory-insertion reaction in the transition metal alkyl compounds [Co(PPh3)(CO)3(Me)], [Mn(CO)5(Me)], [Mo(eta(5)-C5H5)(CO)3(Me)] and [Fe(eta(5)-C5H5)(CO)2(Me)] has been investigated.     

Controlling the oxidation state of arsenic in cyclic arsenic cations

Reduction of AsCl3 with SnCl2, followed by treatment of the "AsCl" with a 1,4-diimine results in electron transfer and formation of an arsenic(III) salt, while treatment of this arsenic(I) reagent or AsI3 with an alpha,alpha'-diiminopyridine ligand forms an arsenic(I) salt.     

Cooperative AND receptor for ion-pairs

A novel heteroditopic calix[4]diquinone receptor capable of binding an anion and cation simultaneously in a cooperative fashion is shown only to recognise halide anions in the presence of a suitable cobound cationic guest species, and displays affinity for certain ion-pairs where no affinity for either of the free ions is observed.     

An N,N'-chelated phosphenium cation supported by a beta-diketiminate ligand

The first example of a phosphenium cation supported by N,N'-chelation of a beta-diketiminate ligand has been prepared and structurally characterized.