Conversion of C[triple bond]C to CO in alkynyl-metal complexes: oxidation of carbon chains capped by carbon-tricobalt clusters.

Treatment of Co(3)(mu(3)-CC[triple bond]CR)(mu-dppm)(CO)(7) with O(2) (air) in the presence of [FcH]PF(6) afforded Co(3){mu(3)-CC(O)R}(mu-dppm)(CO)(7) by the formal conversion -C[triple bond]C- + O-O --> >C-O + C[triple bond]O. In this way, complexes with R = Ph, Fc, and W(CO)(3)Cp, bis-clusters {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(O)(C[triple bond]C)C[triple bond]]}, {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(O)(C[triple bond]C)(x)C(O)C[triple bond, length as m-dash]]} (x = 1, 2), and {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]CC(O)C[triple bond, length as m-dash]CC(6)H(4)C[triple bond]CC(O)C[triple bond]]}, and heterometallic bis-clusters {Co(3)(mu-dppm)(CO)(7)}{mu(3):mu(3)-[[triple bond]CC(O)C[triple bond]CC[triple bond]]}{M(3)(mu-H)(3)(CO)(9)} (M = Ru, Os) have been prepared. Single-crystal XRD structure determinations of several products are reported together with that of precursor {Co(3)(mu-dppm)(CO)(7)}(2){mu(3):mu(3)-[[triple bond]C(C[triple bond]C)(2)C(6)H(4)(C[triple bond]C)(2)C[triple bond]]}.

A novel methodology for the synthesis of complexes containing long carbon chains linking metal centres: molecular structures of [Ru(dppe)Cp*]2(mu-C14) and [Co3(mu-dppm)(CO)7]2(mu3:mu3-C16).

Elimination of AuX(PR3)(X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp2)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C(n) chains (n up to 16).

Kinetic investigations of the mechanism of the rate-determining step of the Na+,K+-ATPase pump cycle.

The kinetics of the E(2) --> E(1) conformational change of unphosphorylated Na(+),K(+)-ATPase from rabbit kidney were investigated via the stopped-flow technique using the fluorescent label RH421 (pH 7.4, 24 degrees C). The enzyme was preequilibrated in a solution containing 25 mM histidine and 0.1 mM EDTA to initially stabilize the E(2) conformation. On mixing enzyme with NaCl alone, tris-ATP alone, or NaCl and tris-ATP simultaneously, a fluorescence decrease was observed. The reciprocal relaxation time, 1/tau, of the fluorescent transient was found to increase with increasing NaCl concentration and reached a saturating value in the presence of 1 mM tris-ATP of 54 (+/-3) s(-1). The experimental behavior could be described by a binding of Na(+) to the enzyme in the E(2) state with a dissociation constant of 31 (+/-7) mM, which induces a subsequent rate-limiting conformational change to the E(1) state. Similar behavior, but with a decreased saturating value of 1/tau, was found when NaCl was replaced by choline chloride. Experiments performed with enzyme from shark rectal gland showed similar effects, but with a lower amplitude of the fluorescence change and a higher saturating value of 1/tau for both the NaCl and choline chloride titrations. The results suggest that Na(+) ions or salt in general play a regulatory role, similar to ATP, in enhancing the rate of the rate-limiting E(2) --> E(1) conformational transition by interaction with the E(2) state.

X-ray crystal structure of (eta(5)-pentaphenylcyclopentadienyl)[1-(eta(5/6)-phenyl)-2,3,4,5-tetraphenylcyclopentadienyl]iron(II), [Fe(eta(5)-C(5)Ph(5))[(eta(5/6)-C(6)H(5))C(5)Ph(4)]], a linkage isomer of decaphenylferrocene.

Very dark blue prismatic crystals of [Fe(eta(5)-C(5)Ph(5))[(eta(5/6)-C(6)H(5))(C(5)Ph(4))]], the linkage isomer of decaphenylferrocene, were grown from (3:1 v/v) hexane/ethyl acetate and characterized by single-crystal X-ray diffraction (space group P2(1)/n, R1(F) 0.0404). The iron atom is coordinated to two C(5)Ph(5) ligands: one with an eta(5)-C(5)-configuration and the other with a coordinated arene configuration. The phenyl groups of the (eta(5)-C(5)Ph(5)) ligand are oriented in a "paddle-wheel" arrangement about the C(5) ring, with which four of them make an average angle of approximately 53 degrees, the other, an angle of approximately 42 degrees. The coordinated C(6)H(5) ring of the other ligand is inclined at only approximately 5 degrees to the uncoordinated C(5) ring, with which three of the other four phenyl rings make an average angle of approximately 64 degrees, and the other (opposite the coordinated arene ring), an angle of 38 degrees.

Mechanism of the rate-determining step of the Na(+),K(+)-ATPase pump cycle.

The kinetics of the E(2) --> E(1) conformational change of unphosphorylated Na(+),K(+)-ATPase from rabbit kidney and shark rectal gland were investigated via the stopped-flow technique using the fluorescent label RH421 (pH 7.4, 24 degrees C). The enzyme was pre-equilibrated in a solution containing 25 mM histidine and 0.1 mM EDTA to stabilize initially the E(2) conformation. When rabbit kidney enzyme was mixed with NaCl alone, tris ATP alone or NaCl, and tris ATP simultaneously, a fluorescence decrease was observed. The reciprocal relaxation time, 1/tau, of the fluorescent transient was found to increase with increasing NaCl concentration and reached a saturating value in the presence of 1 mM tris ATP of 54 +/- 3 s(-1) in the case of rabbit kidney enzyme. The experimental behavior could be described by a binding of Na(+) to the enzyme in the E(2) state with a dissociation constant of 31 +/- 7 mM, which induces a subsequent rate-limiting conformational change to the E(1) state. Similar behavior, but with a decreased saturating value of 1/tau, was found when NaCl was replaced by choline chloride. Analogous experiments performed with enzyme from shark rectal gland showed similar effects, but with a significantly lower amplitude of the fluorescence change and a higher saturating value of 1/tau for both the NaCl and choline chloride titrations. The results suggest that Na(+) ions or salt in general play a regulatory role, similar to that of ATP, in enhancing the rate of the rate-limiting E(2) --> E(1) conformational transition by interaction with the E(2) state.