Preparations, structures, and electrochemical studies of aryldiazene complexes of rhenium: syntheses of the first heterobinuclear and heterotrinuclear derivatives with bis(diazene) or bis(diazenido) bridging ligands.

The mono- and binuclear aryldiazene complexes [Re(C6H5N=NH)(CO)5-nPn]BY4 (1-5) and [(Re(CO)5-nPn)2-(mu-HN=NAr-ArN=NH)](BY4)2 (6-12) [P = P(OEt)3, PPh(OEt)2, PPh2OEt; n = 1-4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H4; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)5-nPn with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; 1H, 31P, 13C, and 15N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C6H5N=NH)(CO)(P(OEt)3)4]BPh4 (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, alpha = 90.33(5) degrees, beta = 91.2(1) degrees, gamma = 89.71(9) degrees, and Z = 2. The "diazene-diazonium" complexes [M(CO)3P2(HN=NAr-ArN identical to N)](BF4)2 (13-15, 17) [M = Re, Mn; P = PPh2OEt, PPh2OMe, PPh3; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4'-HN=NC6H4-C6H4N identical to N)](BF4)2 (16b) were synthesized by allowing the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P'4 and M2'H(CO)5-nP"n afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2HP'4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2'(CO)5-nP"n](BPh4)2 (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh2OEt, PPh2OMe; P',P" = P(OEt)3, PPh(OEt)2; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4; n = 1, 2]. The heterotrinuclear complexes [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)M(P(OEt)3)4(mu-4,4'-HN=NC6H4- C6H4N=NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(mu-4,4'-N2C6H4-C6H4N2)Fe(P(OEt)3)4]BPh4 (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)Fe(4- CH3C6H4CN)(P(OEt)3)4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N2)Fe(CO)2(P(OPh)3)2](BPh4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)3(PPh2OEt)2(4,4'-HN=NC6H4-C6H4N identical to N)]+ with the FeH2(CO)2(P(OPh)3)2 hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and (Mn(CO)2P2)2(mu-4,4'-N2C6H4-C6H4N2) (P = PPh2OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.

Diazo complexes of rhenium: preparations and crystal structures of the bis(dinitrogen), [Re(N2)2(PPh(OEt)2)4][BPh4] and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)(PPh(OEt)2)3][BPh4] derivatives.

Depending on experimental conditions and the nature of the hydrazine, the reactions of ReCl3P3 [P = PPh(OEt)2] with RNHNH2 (R = H, CH3, tBu) afford the bis(dinitrogen) [Re(N2)2P4]+ (2+), dinitrogen ReClN2P4 (3), and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)P3]+ (1+) derivatives. In contrast, reactions of ReCl3P3 [P = PPh(OEt)2, PPh2OEt] with arylhydrazines ArNHNH2 (Ar = Ph, p-tolyl) give the aryldiazenido cations [ReCl(ArN2)(ArNHNH2)P3]+ (4+) and [ReCl(ArN2)P4]+ (7+) and the bis(aryldiazenido) cations [Re(ArN2)2P3]+ (5+, 6+). These complexes were characterized spectroscopically (IR; 1H and 31P NMR), and the BPh4 complexes 1, 2, and 7 were characterized crystallographically. The methyldiazenido derivative [ReCl(CH3N2)(CH3NHNH2)(PPh(OEt)2)3][BPh4] (1) crystallizes in space group P1 with a = 15.396(5) A, b = 16.986(5) A, c = 11.560(5) A, alpha = 93.96(5) degrees, beta = 93.99(5) degrees, gamma = 93.09(5) degrees, and Z = 2 and contains a singly bent CH3N2, group bonded to an octahedral central metal. One methylhydrazine ligand, one Cl- trans to the CH3N2, and three PPh(OEt)2 ligands complete the coordination. The complex [Re(N2)2(PPh(OEt)2)4][BPh4] (2) crystallizes in space group Pbaa with a = 23.008(5) A, b = 23.367(5) A, c = 12.863(3) A, and Z = 4. The structure displays octahedral coordination with two end-on N2 ligands in mutually trans positions. [ReCl(PhN2)(PPh(OEt)2)4][BPh4] (7) crystallizes in space group P2(1)/n with a = 19.613(5) A, b = 20.101(5) A, c = 19.918(5) A, beta = 115.12(2) degrees, and Z = 4. The structure shows a singly bent phenyldiazenido group trans to the Cl- ligand in an octahedral environment. The dinitrogen complex ReClN2P4 (3) reacts with CF3SO3CH3 to give the unstable methyldiazenido derivative [ReCl(CH3N2)P4][BPh4]. Reaction of the methylhydrazine complex [ReCl(CH3N2)(CH3NHNH2)P3][BPh4] (1) with Pb(OAc)4 at -30 degrees C results in selective oxidation of the hydrazine, affording the corresponding methyldiazene derivative [ReCl(CH3N=NH)(CH3N2)P3][BPh4] (8). In contrast, treatment with Pb(OAc)4 of the related arylhydrazines [ReCl(ArN2)(ArNHNH2)P3][BPh4] (4) [P = PPh(OEt)2] gives the bis(aryldiazenido) complexes [Re(ArN2)2P3][BPh4] (5). Possible protonation reactions of Brønsted acids HX with all diazenides, 1, 4, 5, 6, and 8, were investigated and found to proceed only in the cases of the bis(aryldiazenido) complexes 5 and 6, affording, with HCl, the octahedral [ReCl(ArN=NH)(ArN2)P3][BPh4] or [ReCl(Ar(H)NN)(ArN2)P3][BPh4] (10) (Ar = Ph; P = PPh2OEt) derivative.

[Angiodysplasia of the right colon and aortic stenosis. A case report]. / Angiodisplasia del colon destro e stenosi aortica. Descrizione di un caso.

We report the case of a female patient who came to our observation for a severe enterorrhage. Following colonoscopic examination and color-Doppler M-B Mode echocardiography we made the following diagnosis: "angiodysplasia of the right colon in females with aortic stenosis". It was possible to ascertain whether there were similar lesions in other parts of the gastro-intestinal tract because the patient opposed firmly. In agreement with other authors, we believe that colonoscopic examination is the appropriate method to diagnose gastro-intestinal angiodysplasia. The advanced age and the clinical conditions of the patient did not allow surgical treatment, so we treated her with antihaemorrhagic drugs and elevated doses of ascorbic acid (4 g/die). The disappearance of enterorrhagies, the rapid clinical recovery and the normalization of red blood cell (RBC) count allowed us to discontinue antihaemorrhagic treatment and to continue the administration of elevated doses of ascorbic acid. Eight days later, the patient was discharged in good clinical condition and ascorbic acid was prescribed to be continued at home. A good clinical and haemodynamic balance was observed at the six-month follow-up. In conclusion we think that the clinical case we observed, characterized by the association angiodysplasia of the right colon-aortic stenosis, may be included in the diction Heyde's syndrome. In aging patients with severe concomitant diseases, ineligible for surgical interventions, the enterorrhage caused by a non complicated angiodysplastic lesion of the gastro-intestinal tract may benefit from the acute administration of ascorbic acid as the therapeutic agent of first choice capable to loose and/or stop the haemorragic complication and, in chronic administration, to reduce the number of relapses.

Left ventricular performance after intravenous infusion of captopril in patients with congestive heart failure.

BACKGROUND: Although oral administration of captopril, an angiotensin-converting enzyme inhibitor, is effective for the treatment of congestive heart failure (CHF), the effect of its intravenous (iv) administration is not well known. METHODS AND RESULTS: Ten patients (age range 48-72 years), with CHF belonging to the second and third NYHA class, were given an iv bolus of 25 mg of captopril. Before and 30 minutes after the infusion of captopril, a number of parameters of the left ventricular function were evaluated by echocardiography IREX 3 M-B Mode. Eight patients showed a significant improvement of left ventricular performance indices. In fact, the ejection fraction (13.8%, p < 0.05), the cardiac output (24%, p < 0.001), the circumferential shortness fraction (29.9%, p < 0.05), and the fraction shortening (16.0%, p < 0.005) increased significantly, whereas the end-systolic diameter (21%, p < 0.001), the endsystolic stress (23.8%, p < 0.01) and the left ventricle ejection time (4.8%, p < 0.05) decreased significantly. Systolic and diastolic blood pressure values also underwent a significant reduction by 17% and 11% (p < 0.01 and p < 0.05 respectively). No evident correlation between the improvement of the left ventricular function and the basal renin rates was noticed. CONCLUSIONS: A significant improvement of parietal kinesis was observed especially in those segments which showed movement abnormalities (hypokinesia and akinesia) and in many cases this was detected by M-B Mode echocardiography. Our findings may be the result of the following factors: 1) reduction of parietal stress; 2) increased district coronary flow; 3) inhibition of tissue renin-angiotensin-aldosterone system; and 4) "scavenging" action exerted by the SH group of captopril.

[Role of MB-mode transthoracic echography in the early diagnosis of acute pulmonary embolism]. / Ruolo dell'ecografia transtoracica M-B mode nella diagnosi precoce di embolia polmonare acuta.

The aim of the present study was to evaluate whether transthoracic ecocardiography M-B mode was a sensitive and/or specific test for the early diagnosis of acute pulmonary embolism (PEA). For this purpose, we studied 7 patients with PEA as a complication of: deep leg venous thrombosis (3 cases), complicated bone fractures (2 cases), meniscectomy (1 case) and postpartum (1 case). The patients (3 males and 4 females), mean age of 46 +/- 7 years, did not have any previous earlier heart and/or pulmonary diseases. The diagnosis of PEA was made on the basis of clinical criteria, ecg and laboratory tests. Ecocardiography was performed using an IREX 3 M-B mode equipment; the measurements for the calculation of the indexes were made utilizing a short axis parasternal window. The parameters studied were: RVEDD/LVEDD ratio, LVDI Okubo index and the TR grade. Data were analyzed employing the paired Student's t test. In all patients was observed a statistically significant enlargement on the right heart cavities; while only in 3 of them was it possible to observe a slight reduction of the left ventricular cavities. In conclusion, the ecocardiographic exam was is a sensitive test for the diagnosis of PEA. Particularly, the RVEDD/LVEDD ratio gave an early and quantitative indication of the obstruction severity. Indeed, the morphological alteration of the right cavities became evident when the embolic obstruction was of at least 30%. Hence, we suggest that the standard ecocardiography M-B. mode may be regarded has a rapid diagnostic tool for the diagnosis of PEA.

Preparation and characterization of a pentaammineruthenium(III) derivative of horse heart ferricytochrome c.

A stable complex between pentaammineruthenium(III) and histidine-33 in horse heart ferricytochrome c is formed in the reaction between aquopentaammineruthenium(II) and the protein at pH 7. HPLC of the tryptic hydrolysate of the modified protein was employed to identify the pentaammineruthenium binding site. Spectroscopic measurements show that the integrity of the native structure in the vicinity of the heme c group is maintained in the ruthenium-modified protein. The reduction potentials are: heme c (Fe3+/2+), 0.26 V; Ru(NH3)5(His-33)3+/2+, 0.15 V (vs. normal hydrogen electrode).

Conformational studies on sequential polypeptides. Part V. Synthesis and characterization of (Pro-Leu-Gly)10, (Pro-LeuqGly)n and (Leu-Pro-Gly)n.

Syntheses of (Pro-Leu-Gly)n and (Leu-Pro-Gly)n, two synthetic polytripeptide analogues of the non-polar regions of collagen, via the corresponding tripeptide p-nitrophenyl-esters are described. The sequential polypeptide (Pro-Leu-Gly)10 was also obtained by solid-phase synthesis. In the following paper, conformational investigations on these polymers, both in solution and in solid state, will be described.

Conformational studies on sequential polypeptides Part VI. Structural investigations on (Pro-Leu-Gly)10, (Pro-Leu-Gly)n and (Leu-Pro-Gly)n.

The conformational properties of (Pro-Leu-Gly)10, (Pro-Leu-Gly)n and (Leu-Pro-Gly)n were investigated both in solution and in solid state. By circular dichroism studies it was possible to demonstrate the formation of an ordered collagen-like structure for (Pro-Leu-Gly)n in hexafluroisopropanol-water mixtures and in ethylene glycol; (Leu-Pro-Gly)n assumes an ordered conformation only in ethylene glycol; (Pro-Leu-Gly)10 is unordered under all the conditions studied. X-ray diffraction patterns indicated that (Pro-Leu-Gly)n and (Leu-Pro-Gly)n assume a triple helical structure in solid state. In addition, the investigation of (Pro-Leu-Gly)n strongly suggests that this type of structure is a single chain triple helix. The X-ray patterns of (Pro-Leu-Gly)10 do not allow us to ascertain a collagen or polyproline II-like structure for this decatripeptide.