Paul P. M. De Lange

CC coupling and CH activation occurring in reactions of FeRu(CO)6(iPr-Pyca) (ipr-PycaC5H4N-2-CHN-iPr) with activated alkynes RCCR′ (RR′C(O)OMe; RH, R′C(O)Me)

Abstract Reaction of FeRu(CO)6(iPr-Pyca) (5) with the alkynes RCCC(O)OMe (RC(O)OMe (a); RH (b)) leads to the formation of FeRu(CO)5(iPr-Pyca)(μ-η1,η3-MeOC(O)CC(R)C(O)) (RC(O)OMe (6a); RH (6b)). In the case of the monosubstituted alkyne HCCC(O)OMe (b) the CC coupling reaction between the alkyne and the carbonyl ligand proved to be highly regioselective. However, in contrast to literature reports, the CC coupling exclusively takes place at the unsubstituted alkyne C atom, which indicates that substituent effects are dominant. An X-ray single crystal structure of complex 6a has been determined. Red crystals of 6a are monoclinic, space group P21/n, Z = 4, with unit cell dimensions a = 9.277(2), b = 20.112(4), c = 15.964(2) A and β = 99.267(15)°. The structure refinement converged to R = 0.040 for 4123 observed reflections. Thermal conversion of the complexes 6a, b leads to the formation of FeRu(CO)5(C5H4N-2-CHNC(Me)2)(μ,η2-RCCHR′) (RR′C(O)OMe (7a); RH, R′C(O)OMe (7b); RC(O)OMe, R′H (7b′)) in which, as a result of H migration of the isopropyl H atom from the iPr-Pyca ligand to the alkyne, a μ,η2-vinyl fragment is present which is σ-bonded to Ru and η2-bonded to Fe. The former imine C atom is σ-bonded to the Fe centre. The conversion of 6b leads to an unseparable mixture of the complexes 7b and 7b′ suggesting that during the H migration reaction the alkyne C atoms may change their positions and are both capable of abstracting a proton from the iPr-Pyca ligand. Given the fact that the formation of 7b is strongly favoured over the formation of 7b′ substituent effects appear to be important in determining the product distribution of the H migration reaction.

Structure of Six-Dimensional Microstate Geometries

A bstractWe investigate the structure of smooth and horizonless microstate geometries in six dimensions, in the spirit of the five-dimensional analysis of Gibbons and Warner [arXiv:1305.0957]. In six dimensions, which is the natural setting for horizonless geometries with the charges of the D1-D5-P black hole, the natural black objects are strings and there are no Chern-Simons terms for the tensor gauge fields. However, we still find that the same reasoning applies: in absence of horizons, there can be no smooth stationary solutions without non-trivial topology. We use topological arguments to describe the Smarr formula in various examples: the uplift of the five-dimensional minimal supergravity microstates to six dimensions, the two-charge D1-D5 microstates, and the non-extremal JMaRT solution. We also discuss D1-D5-P superstrata and confirm that the Smarr formula gives the same result as for the D1-D5 supertubes which are topologically equivalent.

1,3-Dipolar cycloaddition to the CXM fragment 13. Regioselectivity in the reactions of mononuclear iminoketone complexes Fe(CO)3(tBu-NC(H)C(R)O) (R Ph, Me) with the asymmetric alkyne methyl propynoate

Abstract The reaction of complexes Fe(CO) 3 ( t Bu-NC(H)C(R)O) ( 6a : R  Ph, 6b : R  Me) with one equivalent of methyl propynoate (MP) under an atmosphere of CO, at −30°C (R  Ph) or −50°C (R  Me) results in formation of the Fe(CO) 3 (butenolide) complexes ( 9a,b ), which have been characterized spectroscopically (IR, 1 H, 13 C NMR) and by elemental analysis. The spectroscopic properties indicate that one of the possible regio-isomers is exclusively formed. INEPT and 2D heteronuclear correlation NMR techniques show that in the regio-isomer obtained the former ketone carbon atom is CC bonded to the carbon atom that in the alkyne bore the electron-withdrawing ester group. When the complexes Fe(CO) 3 ( t Bu-NC(H)C(R)O) ( 6a,b ) are treated with two equivalents of MP at −30°C in the absence of CO, the tricyclic complexes 12a,b are formed in moderate yield. The molecular structure of complex 12b has been determined by a single-crystal X-ray diffraction study. It contains three five-membered rings, with the two fused metallacycles sharing three common carbon atoms with the third, a γ-lactone ring, thus forming the tricyclic moiety. The coordination geometry around the central iron atom is distorted octahedral, with the dianionic tridentate ligand occupying three facial positions. The fact that complexes 12 can also be obtained in high yield by irradiation of the corresponding Fe(CO) 3 (butenolide) ( 9 ) in the presence of an excess of MP strongly supports the proposed reaction mechanism in which the second alkyne is initially π-coordinated and subsequently coupled with the π-coordinated double bond of the butenolide heterocycle.