Synthesis and characterization of trans-[Os(en)2py(H)]2+ and related studies.

trans-[Os(en)(2)pyH](Otf)(2), 2, is recovered from an acidic solution of trans-[Os(en)(2)py(H(2))](OTf)(2), 1, which has been subjected to one electron oxidation. The structures of both 1 and 2 have been determined by single crystal X-ray analysis. In cyclic voltammetry, 2 shows a one electron oxidation wave at 0.

Cooperative ligation, back-bonding, and possible pyridine-pyridine interactions in tetrapyridine-vanadium(II): a visible and X-ray spectroscopic study.

The binding of pyridine by V(II) in aqueous solution shows evidence for the late onset of cooperativity. The K(1) governing formation of [V(py)](2+) (lambda(max) = 404 nm, epsilon(max) = 1.43 +/- 0.

Inner-Sphere Cluster Formation by [Ru(NH(3))(5)H(2)O](3+) or [Os(NH(3))(5)H(2)O](3+) in Combination with [M(CN)(6)](4)(-) (M = Fe, Ru, or Os).

When the cations [M'(NH(3))(5)H(2)O](3+) or [M'(NH(3))(5)H(2)O](2+) (M' = Ru, Os) are added in excess of the co-reactants [M(CN)(6)](4)(-) (M = Fe, Ru, Os), inner-sphere binding ends abruptly at the 4:1 ratio. The [M(CN)(6)](4)(-) --> [M'(NH(3))(5)](3+) charge transfer (CT) absorption shifts slightly to higher energy as the cations accumulate in the cluster, and there is a progressive decrease in intensity per additional oscillator introduced. The absorption bands and the electrochemical properties reveal the presence of isomeric forms in complexes of order 2 and above.

Kinetic Effects in Outer Sphere Ion Clusters: Interactions of [Ru(NH(3))(5)H(2)O](3+) with [Ru(CN)(6)](4)(-), [Fe(CN)(6)](4)(-), [Os(CN)(6)](4)(-) and [Co(CN)(6)](3-).

A study of the kinetics of substitution in [Ru(NH(3))(5)H(2)O](3+) by the nucleophiles [Fe(CN)(6)](4)(-), [Ru(CN)(6)](4)(-), [Os(CN)(6)](4)(-), and [Co(CN)(6)](3)(-) in the absence of indifferent electrolyte shows that k for substitution (in every case first order in cation concentration) increases as the ratio of the concentration of the nucleophile to the aquo ion increases, and then it abruptly becomes independent of this ratio. When the reaction medium is 1.5 x 10(-)(2) M H(+) (chosen to eliminate catalysis by the formation of [Ru(NH(3))(5)H(2)O](2+) when [Fe(CN)(6)](4)(-) is the nucleophile), the critical values of R are ca.

Oxygen versus Nitrogen Bonding of Carboxamides to Pentaammineruthenium(II/III).

Reversible linkage isomerizations are identified for monodentate carboxamides on pentaammineruthenium(II) and -(III). The equilibrium between O-bonded and N-bonded amides is pH and oxidation-state dependent. When both O- and N-bound amides are neutral uncharged ligands (pH < 7, Ru(II); pH < 2, Ru(III)), the O-bonded isomers are thermodynamically more stable for both oxidation states.

Models for Arginine-Metal Binding. Synthesis of Guanidine and Urea Ligands through Amination and Hydration of a Cyanamide Ligand Bound to Platinum(II), Osmium(III), and Cobalt(III).

Dimethylcyanamide (N identical withCNMe(2)) has been coordinated to both hard and soft electrophiles ((NH(3))(5)Co(3+), (NH(3))(5)Os(3+), (dien)Pt(2+)) which activate ( approximately x10(6)) the nitrile toward attack by nucleophiles such as ammonia and hydroxide. Amination with liquid ammonia gave a rare coordinated guanidine (N,N-dimethylguanidine) ligand, which NMR spectra and X-ray crystal structures show to be charge neutral rather than anionic. Crystals of [(NH(3))(5)CoNH=C(NH(2))NMe(2)](S(2)O(6))(3/2).

Osmium Complexes of 1,4,7-Triazacyclononane (tacn) and 1,4,7-Trimethyl-1,4,7-triazacyclononane (Me(3)tacn) and the X-ray Crystal Structure of [(Me(3)tacn)Os(eta(6)-C(6)H(5)BPh(3))]BPh(4).CH(3)CN.

The complexes of osmium with tacn (1,4,7-triazacyclononane) and Me(3)tacn (1,4,7-trimethyl-1,4,7-triazacyclononane), [LOs (eta(6)-C(6)H(6))](PF(6))(2) (L = tacn) and LOsCl(3) (L = tacn, Me(3)tacn), have been prepared by substitution of L on [Os(eta(6)-C(6)H(6))Cl(2)](2) or [Os(2)Cl(8)](2)(-), respectively. Reaction of LOsCl(3) with neat triflic acid leads to partial replacement of chloride and formation of the binuclear Os(III)-Os(III) complexes [LOs(&mgr;-Cl(3))OsL](PF(6))(3) (L = tacn, Me(3)tacn). The binuclear nature was established by NMR spectroscopy and elemental analysis and, for L = tacn, a partially refined X-ray crystal structure which shows the Os-Os separation to be 2.