Metal clusters as organometallic synthons

My PhD project is focussed on the synthesis, the characterization and the study of the properties of palladium and platinum trinuclear and hexanuclear clusters, and on the evaluation of the possibility to insert these units in oligomeric, polymeric or dendrimeric macromolecular systems. The project includes the synthesis and the spectroscopic, electrochemical and spectroelectrochemical characterization of new trinuclear palladium clusters sharing the general formula [Pd3(μ-PBut2)3(L)2L']n+ and the functionalization of the known platinum clusters [Pt3(μ-PBut2)3(CO)2H] and [Pt6(μ-PBut2)4(CO)6](CF3SO3)2 with conjugated organic and organometallic ligands able to connect more cluster units. The electrochemical and spectroelectrochemical properties of the new compounds obtained in these studies are also investigated

Synthesis and characterization of non-bridging mono- and bis-σ-η1-alkynyl derivatives of the phosphido-bridged hexaplatinum core [Pt6(μ-PBut2)4(CO)4]2+

Several mono- or bis-alkynyl derivatives of general formula Pt6(μ-PBut2)4(CO)4X(CC–R), Pt6(μ-PBut2)4(CO)4(CC–R)2 or Pt6(μ-PBut2)4(CO)4(CC–R)(CC–R′) were obtained under Sonogashira type conditions. The new clusters have been characterized with microanalysis and using IR and multinuclear NMR spectroscopy. The crystal and molecular structures of Pt6(μ-PBut2)4(CO)4(CC–R)2 (R = H, C6H4-4-n-C5H11) are presented and electrochemical and spectroelectrochemical studies of some representative compounds are also reported

Reversible MRI abnormalities in mesial temporal lobe epilepsy: a case report

The question regarding the existence of abnormalities in the neuroimaging exams immediately after status epilecticus or epileptic seizures, but showing complete reversibility after a proper antiepileptic therapy, has long been debated. The first reports attempting to demonstrate their existence date back to the 1980s, and relied upon computed tomography as the imaging method of choice. After the introduction of MRI, a more appropriate characterization of these abnormalities was obtained along with the description of their most frequent features: (a) T2 signal hyperintensity in the white matter and, occasionally, (b) reduced apparent diffusion coefficient (ADC) and increased signal in DWI sequences.The MRI abnormalities induced by epileptic activity pose a broad differential diagnosis including infections, inflammatory autoimmune encephalopathies, neoplasms. It remains a diagnosis of exclusion and requires proper diagnostic iter in order to reduce the risk of misdiagnosis and unnecessary intervention.In this case report, a thorough presentation will be outlined about MRI alterations in the left mesial temporal lobe, which resulted completely reversible after a proper antiepileptic therapy

Operationalizing mild cognitive impairment criteria in small vessel disease: The VMCI-Tuscany Study

Introduction Mild cognitive impairment (MCI) prodromic of vascular dementia is expected to have a multidomain profile. Methods In a sample of cerebral small vessel disease (SVD) patients, we assessed MCI subtypes distributions according to different operationalization of Winblad criteria and compared the neuroimaging features of single versus multidomain MCI. We applied three MCI diagnostic scenarios in which the cutoffs for objective impairment and the number of considered neuropsychological tests varied. Results Passing from a liberal to more conservative diagnostic scenarios, of 153 patients, 5% were no longer classified as MCI, amnestic multidomain frequency decreased, and nonamnestic single domain increased. Considering neuroimaging features, severe medial temporal lobe atrophy was more frequent in multidomain compared with single domain. Discussion Operationalizing MCI criteria changes the relative frequency of MCI subtypes. Nonamnestic single domain MCI may be a previously nonrecognized type of MCI associated with SVD

Synthesis and Spectroscopic and Spectroelectrochemical Characterization of a New Family of 44e- Tris-Phosphido Bridged Palladium Triangles.

Triangular clusters containing a [M3(μ-PR2)3]+ core are very common in platinum chemistry but were virtually unknown for M = Pd. Herein we describe the synthesis and characterization of several palladium derivatives belonging to this class. The trinuclear monohalide clusters {Pd3}(CO)2X [{Pd3} = Pd3(μ-PBut2)3; X = Br, I] were prepared by reacting [nBu4N]X or KX with the dinuclear complex [Pd(PBut2H)(μ-PBut2)]2 and H2O under an atmosphere of CO. The reaction of {Pd3}(CO)2I with CNBut leads to the substitution of all the terminal ligands to afford the symmetrical cluster [{Pd3}(CNBut)3]I. The latter reacts with TlPF6 (excess) or AgCF3SO3 (1:1 ratio) to give anion metathesis, whereas the addition of a second equivalent of Ag+ causes cluster oxidation to the thermally stable paramagnetic 43e− dication [{Pd3}(CNBut)3]2+. The cationic clusters [{Pd3}(CO)2(L)]PF6 (L = NCCH3, Py or CO) were obtained by reacting {Pd3}(CO)2I with TlPF6, under nitrogen in acetonitrile or in pyridine or under 1 atm of carbon monoxide in THF. Finally, {Pd3}(CO)2Cl was achieved by the reaction of [{Pd3}(CO)3]PF6 with [(PPh3)2N]Cl. All clusters have been obtained in good yields and purity and have been characterized by microanalysis and IR and multinuclear NMR spectroscopy. Single crystal X-ray diffraction studies on {Pd3}(CO)2Br and [{Pd3(CNBut)3]CF3SO3 are also reported. The cyclovoltammetric profile exhibited by the palladium clusters prepared in this work is characterized by the presence of two monoelectronic oxidation processes whose reversibility and potentials depend on the nature of the ligands. Moreover, the UV−vis and IR spectroelectrochemical analysis of {Pd3(CO)2I, [{Pd3}(CO)3]PF6 and [{Pd3}(CNBut)3]PF6 allowed the spectroscopical characterization of some electrogenerated oxidized species and provided some detail for the redox-coupled reactions of metastable products

Reversible MRI abnormalities in mesial temporal lobe epilepsy: a case report

The question regarding  the existence of abnormalities in the neuroimaging exams immediately after status epilecticus or epileptic seizures, but showing complete reversibility after a proper antiepileptic therapy, has long been debated. The first reports attempting to demonstrate their existence date back to the 1980s, and relied upon computed tomography as the imaging method of choice. After the introduction of MRI, a more appropriate characterization of these abnormalities was obtained along with the description of their most frequent features: (a) T2 signal hyperintensity in the white matter and, occasionally, (b) reduced apparent diffusion coefficient (ADC) and increased signal in DWI sequences. The MRI abnormalities induced by epileptic activity pose a broad differential diagnosis including infections, inflammatory autoimmune encephalopathies, neoplasms. It remains a diagnosis of exclusion and requires proper diagnostic iter in order to reduce the risk of misdiagnosis and unnecessary intervention. In this case report, a thorough presentation will be outlined about MRI alterations in the left mesial temporal lobe, which resulted completely reversible after a proper antiepileptic therapy

A Case of 22q11 Deletion Syndrome (22q11DS) with a Panayiotopoulos Epileptic Pattern: Are Additional Copy-Number Variations a Possible Second Hit in Modulating the 22q11DS Phenotype?

"22q11 deletion syndrome" (22q11DS) is a rare genetic syndrome, in which most patients share the same deletion, but their clinical features may vary a great deal. The genetic mechanisms underlying the variable expressivity and reduced penetrance of 22q11DS still have to be fully elucidated. Epilepsy has been reported in about 15.2% of the patients; however, few studies have focused on this topic, and in most cases, a detailed epileptic profile is missing. Since only a minority of patients experience epileptic seizures, 22q11deletion can be considered a predisposing factor, which is not sufficient "per se" to cause epilepsy; to date, no candidate gene for epilepsy has been identified in the deleted region. We report on a 6-year-old girl with 22q11DS presenting a form of epilepsy that can be classified as "Panayiotopoulos syndrome." Array CGH revealed an additional microduplication of 172 kb in 2q37, harboring three genes. One of these, DGKD (diacylglycerol kinase delta), is interrupted by the distal breakpoint of the duplication. DGKD encodes a cytoplasmic enzyme that phosphorylates diacylglycerol to produce phosphatidic acid. This is an important second messenger in a pathway of lipid signaling that has been implicated in epilepsy and other neurological diseases. Disruption of DGKD by a t(X;2) has been previously reported in a patient with epilepsy. The 2q37 microduplication was inherited from her mother, who never experienced epileptic seizures, thus this imbalance is not "per se" sufficient to cause epilepsy. It can be hypothesized that the epileptic phenotype is provoked by the simultaneous presence of 22q11.2 deletion and 2q37 duplication. It has been shown that rare additional copy-number variations (CNVs) outside the 22q11.2 region may modulate the risk of congenital heart defects. It is possible that also for the epileptic phenotype, the additional CNVs may represent an important modifying factor underlying the variable expressivity and incomplete penetrance in the 22q11DS

Synthesis and Electrochemical Characterization of Hexanuclear Platinum Bis-Pseudohalides

The hexanuclear phosphido-bridged dication [Pt6(mu-PBu(t)2)4(CO)6](2+), (1)(2+), reacts under mild conditions with pseudo-halide anions (CN(-), NCO(-), NCS(-)) to afford the corresponding neutral bis-substituted clusters Pt6(mu-PBu(t)2)4(CO)4X2 (2, X = CN; 3, X = SCN; 4, X = NCO). The reaction with sodium azide affords 4, which may arise from the formation of the intermediate bis-azido derivative Pt6(mu-PBu(t)2)4(CO)4(N3)2, 5, and CO. These react rapidly with each other affording 4 and N2. Cluster 5 was alternatively prepared as a stable compound by reacting with NaN3 the neutral cluster Pt6(mu-PBu(t)2)4(CO)4(OTf)2, 14, which contains two weakly bonded triflate anions. As expected, 5 reacts with carbon monoxide (1 atm) affording cluster 4 instantaneously and quantitatively. The new pseudo-halide clusters 2-5, which are interesting potential precursors of cluster-containing molecular frameworks, have been characterized by IR and multinuclear NMR spectroscopy. The solid state structures of clusters 2-4 have also been studied by single-crystal X-ray diffractometry. The main features of the molecular structures remain similar to those of many related congeners described previously; in addition, an interesting reversible phase transition was observed in the crystal structure of cluster 3. As their known congeners, the clusters undergo two reversible one-electron reductions and an irreversible oxidation. An excellent linear correlation was found between the redox potentials of the cathodic processes and Lever's ligand parameter EL

Synthesis and Spectroscopic and Spectroelectrochemical Characterization of a New Family of 44e^– Tris-Phosphido-Bridged Palladium Triangles

Triangular clusters containing a [M₃(μ-PR₂)₃]⁺ core are very common in platinum chemistry but were virtually unknown for M = Pd. Herein we describe the synthesis and characterization of several palladium derivatives belonging to this class. The trinuclear monohalide clusters {Pd₃}­(CO)₂X [{Pd₃} = Pd₃(μ-PBu^<i>t</i>₂)₃; X = Br, I] were prepared by reacting [^<i>n</i>Bu₄N]­X or KX with the dinuclear complex [Pd­(PBu^<i>t</i>₂H)­(μ-PBu^<i>t</i>₂)]₂ and H₂O under an atmosphere of CO. The reaction of {Pd₃}­(CO)₂I with CNBu^<i>t</i> leads to the substitution of all the terminal ligands to afford the symmetrical cluster [{Pd₃}­(CNBu^<i>t</i>)₃]­I. The latter reacts with TlPF₆ (excess) or AgCF₃SO₃ (1:1 ratio) to give anion metathesis, whereas the addition of a second equivalent of Ag⁺ causes cluster oxidation to the thermally stable paramagnetic 43e^– dication [{Pd₃}­(CNBu^<i>t</i>)₃]²⁺. The cationic clusters [{Pd₃}­(CO)₂(L)]­PF₆ (L = NCCH₃, Py or CO) were obtained by reacting {Pd₃}­(CO)₂I with TlPF₆, under nitrogen in acetonitrile or in pyridine or under 1 atm of carbon monoxide in THF. Finally, {Pd₃}­(CO)₂Cl was achieved by the reaction of [{Pd₃}­(CO)₃]­PF₆ with [(PPh₃)₂N]­Cl. All clusters have been obtained in good yields and purity and have been characterized by microanalysis and IR and multinuclear NMR spectroscopy. Single crystal X-ray diffraction studies on {Pd₃}­(CO)₂Br and [{Pd₃}­(CNBu^<i>t</i>)₃]­CF₃SO₃ are also reported. The cyclovoltammetric profile exhibited by the palladium clusters prepared in this work is characterized by the presence of two monoelectronic oxidation processes whose reversibility and potentials depend on the nature of the ligands. Moreover, the UV–vis and IR spectroelectrochemical analysis of {Pd₃}­(CO)₂I, [{Pd₃}­(CO)₃]­PF₆ and [{Pd₃}­(CNBu^<i>t</i>)₃]­PF₆ allowed the spectroscopical characterization of some electrogenerated oxidized species and provided some detail for the redox-coupled reactions of metastable products

Synthesis and Spectroscopic and Spectroelectrochemical Characterization of a New Family of 44e^– Tris-Phosphido-Bridged Palladium Triangles

Triangular clusters containing a [M₃(μ-PR₂)₃]⁺ core are very common in platinum chemistry but were virtually unknown for M = Pd. Herein we describe the synthesis and characterization of several palladium derivatives belonging to this class. The trinuclear monohalide clusters {Pd₃}­(CO)₂X [{Pd₃} = Pd₃(μ-PBu^<i>t</i>₂)₃; X = Br, I] were prepared by reacting [^<i>n</i>Bu₄N]­X or KX with the dinuclear complex [Pd­(PBu^<i>t</i>₂H)­(μ-PBu^<i>t</i>₂)]₂ and H₂O under an atmosphere of CO. The reaction of {Pd₃}­(CO)₂I with CNBu^<i>t</i> leads to the substitution of all the terminal ligands to afford the symmetrical cluster [{Pd₃}­(CNBu^<i>t</i>)₃]­I. The latter reacts with TlPF₆ (excess) or AgCF₃SO₃ (1:1 ratio) to give anion metathesis, whereas the addition of a second equivalent of Ag⁺ causes cluster oxidation to the thermally stable paramagnetic 43e^– dication [{Pd₃}­(CNBu^<i>t</i>)₃]²⁺. The cationic clusters [{Pd₃}­(CO)₂(L)]­PF₆ (L = NCCH₃, Py or CO) were obtained by reacting {Pd₃}­(CO)₂I with TlPF₆, under nitrogen in acetonitrile or in pyridine or under 1 atm of carbon monoxide in THF. Finally, {Pd₃}­(CO)₂Cl was achieved by the reaction of [{Pd₃}­(CO)₃]­PF₆ with [(PPh₃)₂N]­Cl. All clusters have been obtained in good yields and purity and have been characterized by microanalysis and IR and multinuclear NMR spectroscopy. Single crystal X-ray diffraction studies on {Pd₃}­(CO)₂Br and [{Pd₃}­(CNBu^<i>t</i>)₃]­CF₃SO₃ are also reported. The cyclovoltammetric profile exhibited by the palladium clusters prepared in this work is characterized by the presence of two monoelectronic oxidation processes whose reversibility and potentials depend on the nature of the ligands. Moreover, the UV–vis and IR spectroelectrochemical analysis of {Pd₃}­(CO)₂I, [{Pd₃}­(CO)₃]­PF₆ and [{Pd₃}­(CNBu^<i>t</i>)₃]­PF₆ allowed the spectroscopical characterization of some electrogenerated oxidized species and provided some detail for the redox-coupled reactions of metastable products