Synthesis, characterization and catalytic/antibacterial activity studies of ɳ⁵₋ cyclopentadienyl dicarbonyl ruthenium(II) amine complexes.
The reaction of (η⁵-C₅H₅)Ru(CO)₂I and AgBF₄ in the ratio of 1:1 in methylene chloride afforded the iodo-bridged ruthenium complex, [(η⁵-C₅H₅)Ru(CO)₂]₂I. Two polymorphs, I and II, of the complex [(η⁵-C₅H₅)Ru(CO)₂]₂I were isolated. Polymorph I crystallized in the monoclinic P2/c space group with a = 12.0982(5) Å, b = 9.7923(4) Å, c = 15.5321(6) Å, β = 102.9880(10)°, while polymorph II crystallized in the monoclinic P2₁/c with a = 7.00560(10) Å, b = 14.1446(3) Å, c = 18.2226(3) Å, β = 96.2390(10)°. The reaction of (η⁵-C₅H₅)Ru(CO)₂I and a slight excess of AgBF₄ in methylene chloride afforded the Lewis acid, [CpRu(CO)₂]⁺BF₄, which was subsequently reacted with slight excesses of 1-alkanamines, RNH₂, in dry dichloromethane affording the new water-soluble 1-alkanaminedicarbonyl(η⁵-cyclopentadienyl)ruthenium(II) tetrafluoroborate complexes, [CpRu(CO)₂NH₂R]⁺BF₄⁻ (Cp = η⁵-C₅H₅; R = CH₃, C₂H₅, C₃H₇, C₄H₉, C₅H₁₁ and C₆H₁₃). Complexes of the type, [CpRu(CO)₂L]⁺BF₄⁻, (L = C₆H₁₁NH₂, C₆H₅CH₂NH₂, C₆H₅CH(CH₃)NH₂, (CH₃)₂CHNH₂, CH₂CHCH₂NH₂, NH₂CH₂(C₆H₄)OCH₃, NH₂CH₂C₆H₄CN, NH₂(CH₃)₃C₆H₂) were also synthesized by the reaction of the Lewis acid, [CpRu(CO)₂]⁺BF₄, with the ligands, L. The reaction of (η⁵-C₅(CH₃)₅)Ru(CO)₂I and a slight excess of AgBF₄ in methylene chloride afforded the Lewis acid, [Cp*Ru(CO)₂]⁺BF₄ (Cp* = η⁵-C₅(CH₃)₅), which was subsequently reacted with slight excesses of 1-alkanamine, RNH₂ (R = CH₃, C₂H₅, C₃H₇, C₄H₉, C₅H₁₁), in dry dichloromethane affording the new water-soluble complex salts, [Cp*Ru(CO)₂NH₂R]⁺BF₄⁻ The α,αʹ-diaminoalkane-bridged diruthenium complex salts [Rp₂NH₂(CH₂))nNH₂]Y₂ (Rp = CpRu(CO)₂, where Cp =η⁵-C₅H₅; n = 2, 3, 4 and 6; Y = BF₄ or SO₃CF₃) were synthesized by the reaction of the acetonitrile complexes, [RpNCCH₃]Y and NH₂(CH₂)nNH₂ (n = 2, 3,4 and 6) in the ratio of 2:1. All the complexes synthesized in this study are new and were fully characterized by IR, NMR, elemental analysis and melting point. The crystal structures of 12 complexes were determined; they all feature a “pseudo-octahedral three-legged piano stool” structure in which the ruthenium centre was coordinated through a sigma bond to the amine N atom and two carbonyl ligands at the base of the stool and the cyclopentadienyl ring as the apex of the stool. Antimicrobial susceptibility tests were done for the α,αʹ-diaminoalkane-bridged diruthenium compounds, and some mononuclear complexes, [CpRu(CO)₂L]⁺BF₄⁻. Good antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as mycobacterium, was achieved. Furthermore, the complexes synthesized showed excellent catalytic activity in the oxidation of styrene to form benzaldehyde in very good yield.