Organometallic compounds containing a guanidinium group. Phenylmercury(II) derivatives of creatine and creatinine
Abstract: Phenylmercury(II) replaces a proton of creatine, H2NC+(NH2)NMeCH2C02-, in basic solution to form the zwitterionic
complex PhHgNHC+(NH2)NMeCH2CO2-. Creatine and creatinine (C4H7N30) react with PhHg((OH)N03)I/2 in aqueous ethanol to form a 2:l complex [(PhHg)2(C4H6N30][N03] which exists in two crystalline forms. Creatinine forms a 1:l
complex [PhHg(C4H7N30)][N03].1/2H20 at pH 1.4 on reaction with PhHg((OH)N03)l/2 in the presence of nitric acid.
The 1:l and 2:l complexes may be interconverted. Creatinine hydronitrate, [H2NCNMeCH2CONH][NO3], and the PhHg(II) complexes of creatinine have similar infrared (including deuterated derivatives) and 1H NMR spectra, consistent with retention of the creatinine ring and presence of a guanidinium group in the complexes. An X-ray structural analysis of one crystalline form of the 2:l complex shows bonding of PhHg(II) groups to the exocyclic and ring nitrogens of creatinine to form the cation
[PhHgNHCNMeCH2CONHgPh]+.
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TL;DR: The effects of a metal center on the oxidation of guanidine should provide an interesting comparison with the biological aerobic oxidation of arginine catalyzed by NOS.
Abstract: The guanidine moiety of arginine is involved in the active sites of a variety of enzymes, such as nitric oxide synthase (NOS) and NiFe hydrogenase. In this paper we aim to investigate the effects of a metal center on the oxidation of guanidine, which should provide an interesting comparison with the biological aerobic oxidation of arginine catalyzed by NOS. We studied the oxidation of an osmium(III) guanidine complex, mer-[Os(L){N(H)C(NH2)2}(CN)3]−, (OsG, HL = 2-(2-hydroxyphenyl)benzoxazole) by m-chloroperbenzoic acid (m-CPBA), which is potentially an O atom transfer reagent, and by (NH4)2[CeIV(NO3)6], which is a one-electron oxidant. With m-CPBA, mer-[Os(NO)(L)(CN)3]− (mer-OsNO) is the product, while with CeIV, mer-[OsVI(N)(L)(CN)3]− (mer-OsN) is formed instead. The crystal structures of mer-OsNO and mer-OsN were determined by X-ray crystallography. The mechanisms for the oxidation of OsG by m-CPBA and CeIV are proposed.
12 citations
TL;DR: In this article, a tetrahedral geometry for the Cu(II) adduct with neutral creatinine was obtained and IR evidence suggests that the adduct is tetrahedrahedral.
Abstract: A Cu(II) complex of creatinine (creat) was prepared, with formula Cu(creat)2Cl2, as well as a Cu(I) creatinine complex, Cu(creat H_1)(EtNH2).H2O(EtNH2 = ethylamine). The Cu(II) adduct is complexed with neutral creatinine and IR evidence suggests a tetrahedral geometry for the complex with bonding to the ring amino nitrogen atom. Diamagnetic Cu(creat H_1)(EtNH2).H2O, formed from a redox reaction between Cu(II) and creatinine, is composed of Cu(I) atoms bonded to the deprotonated ring amino nitrogen, with the exocyclic carbonyl group hydrogen bonded to coordinated ethylamine molecules.
11 citations
Patent•
09 May 1996TL;DR: In this paper, a method for the detection of hydrogen peroxide in biological fluids or an aqueous solution which involves contacting the solution with an oxidation-reduction indicator and a transition metal complex is presented.
Abstract: The present invention is a method for the detection of hydrogen peroxide in biological fluids or an aqueous solution which involves contacting the solution with an oxidation-reduction indicator and a transition metal complex. The transition metal complex is either a creatinine coordinated with iron or a guanidine coordinated with iron.
10 citations
TL;DR: It is concluded that direct CMP-crea interligand interactions are missing in the Cu-CMP-Crea complex due to the inappropriate correspondence between the donor and/or acceptor H-bonding properties of these ligands.
9 citations
TL;DR: In this article, the formation constants of binary and ternary mixed-ligand metal complexes were determined by pH-metric titrations at 25 −±−0.1°C and at a constant ionic strength I −= 0.1 −M (KNO3), respectively.
Abstract: Ternary mixed‐ligand metal complexes [M(L1)(L2)2](H2O) n , where M = Co(II), Ni(II), or Cu(II), L1 = the dianion of succinic, malic, or tartaric acid, and L2 = creatinine, were synthesized and characterized using microchemical and thermal analyses, molar conductance, infrared, and electronic spectral measurements. A square–planar structure is suggested for the Co(II) and Cu(II) ternary complexes, whereas Ni(II) ternary complexes have tetrahedral stereochemistry. Formation constants of the binary and ternary complexes in such systems were determined by pH‐metric titrations at 25 ± 0.1 °C and at a constant ionic strength I = 0.1 M (KNO3). The stability of the various complexes was discussed in terms of the nature of both the ligands and metal ions. The thermodynamic functions (ΔH, ΔG o, and ΔS o) associated with the complex formation of [Cu(II) + aliphatic acids + creatinine] were also determined and examined.
8 citations
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