The two enantiomers of chiral phosphonate 4-phenyldinaphtho2,1-d:1',2'-f1,3,2dioxaphosphepine 4-oxide, O=PPh(BINOL), were synthesized from the proper 1,1'-bi-2-naphtol (BINOL) enantiomer and ...characterized. The structure of the (
)-enantiomer was elucidated by means of single-crystal X-ray diffraction. The reaction with anhydrous ZnBr
afforded complexes having the general formula ZnBr
{O=PPh(BINOL)}
that showed intense fluorescence centered in the near-UV region rationalized on the basis of TD-DFT calculations. The corresponding Mn(II) complexes with the general formula MnX
{O=PPh(BINOL)}
(X = Cl, Br) exhibited dual emission upon excitation with UV light, with the relative intensity of the bands dependent upon the choice of the halide. The highest energy transition is comparable with that of the Zn(II) complex, while the lowest energy emission falls in the red region of the spectrum and is characterized by lifetimes in the hundreds of microseconds range. Although the emission at lower energy can also be achieved by direct excitation of the metal center, the luminescence decay curves suggest that the band in the red range is possibly derived from BINOL-centered excited states populated by intersystem crossing.
Diiron μ-aminocarbyne complexes Fe
Cp
(NCMe)(CO)(μ-CO){μ-CN(Me)(R)}CF
SO
(R = Xyl,
; R = Me,
; R = Cy,
; R = CH
Ph,
), freshly prepared from tricarbonyl precursors
, reacted with NaOCN (in acetone) ...and NBu
SCN (in dichloromethane) to give Fe
Cp
(k
-NCO)(CO)(μ-CO){μ-CN(Me)(R)} (R = Xyl,
; Me,
; Cy,
) and Fe
Cp
(k
-NCS)(CO)(μ-CO){μ-CN(Me)(CH
Ph)},
in 67-81% yields via substitution of the acetonitrile ligand. The reaction of
with KSeCN in THF at reflux temperature led to the cyanide complexes Fe
Cp
(CN)(CO)(μ-CO){μ-CNMe(R)},
-
(45-67%). When the reaction of
with KSeCN was performed in acetone at room temperature, subsequent careful chromatography allowed the separation of moderate amounts of Fe
Cp
(k
-SeCN)(CO)(μ-CO){μ-CN(Me)(Xyl)},
, and Fe
Cp
(k
-NCSe)(CO)(μ-CO){μ-CN(Me)(Xyl)},
. All products were fully characterized by elemental analysis, IR, and multinuclear NMR spectroscopy; moreover, the molecular structure of
was ascertained by single crystal X-ray diffraction. DFT calculations were carried out to shed light on the coordination mode and stability of the {NC
-} fragment.
A series of 2,3-dicarboxylato-5-acetyl-4-aminoselenophenes, 5a–j, was obtained via the uncommon assembly of building blocks on a diiron platform, starting from commercial Fe2Cp2(CO)4 through the ...stepwise formation of diiron complexes 2a–dCF3SO3, 3a–d, and 4a–j. The selenophene-substituted bridging alkylidene ligand in 4a–j is removed from coordination upon treatment with water in air under mild conditions (ambient temperature in most cases), affording 5a–j in good to excellent yields. This process is highly selective and is accompanied by the disruption of the organometallic scaffold: cyclopentadiene (CpH) and lepidocrocite (γ-FeO(OH)) were identified by NMR and Raman analyses at the end of one representative reaction. The straightforward cleavage of the linkage between a bridging Fischer alkylidene and two (or more) metal centers, as observed here, is an unprecedented reaction in organometallic chemistry: in the present case, the carbene function is converted to a ketone which is incorporated into the organic product. DFT calculations and electrochemical experiments were carried out to give insight into the release of the selenophene-alkylidene ligand. Compounds 5a–j were fully characterized by elemental analysis, mass spectrometry, IR, and multinuclear NMR spectroscopy and by X-ray diffraction and cyclic voltammetry in one case.
The homoleptic cationic complex formed by reacting suitable manganese(II) salts with 2,2′-bipyridine-1,1′-dioxide (bipyO2) has been subjected to several studies in the past because of its peculiar ...absorption and electrochemical features. Here, the first single-crystal X-ray structure determination of a Mn(bipyO2)32+ salt is reported, where the charge of the cation is balanced by perchlorate anions. The hydrated salt Mn(bipyO2)3(ClO4)2 crystallizes in the monoclinic system (P21/n space group) and the asymmetric unit contains three cationic complexes and six perchlorate anions. The environment of the manganese(II) ions is best described as octahedral, with scarce variations among the three cations in the asymmetric unit. The bipyO2 ligands exhibit κ2 coordination mode, forming seven-membered metallacycles. The X-ray outcomes have been used as the starting point for DFT and TDDFT calculations, aimed to elucidate the charge transfer origin of the noticeable absorption in the visible range. The MLCT nature is confirmed by the hole and electron distributions associated with the spin-allowed transitions. DFT calculations on the related manganese(III) complex indicate that the geometry of Mn(bipyO2)32+ changes only slightly upon oxidation, in agreement with the reversible electrochemical behaviour experimentally observed.
The tetrafluoroborate salt of the cationic Cu(I) complex Cu(CHpz3)(PPh3)+, where CHpz3 is the tridentate N-donor ligand tris(pyrazol-1-yl)methane and PPh3 is triphenylphosphine, was synthesized ...through a displacement reaction on the acetonitrile complex Cu(NCCH3)4BF4. The compound crystallizes in the monoclinic P21/c space group. The single-crystal X-ray diffraction revealed that the copper(I) centre is tetracoordinated, with a disposition of the donor atoms surrounding the metal centre quite far from the ideal tetrahedral geometry, as confirmed by continuous shape measures and by the τ4 parameter. The intermolecular interactions at the solid state were investigated through the Hirshfeld surface analysis, which highlighted the presence of several non-classical hydrogen bonds involving the tetrafluoroborate anion. The electronic structure of the crystal was modelled using plane-wave DFT methods. The computed band gap is around 2.8 eV and separates a metal-centred valence band from a ligand-centred conduction band. NMR spectroscopy indicated the fluxional behaviour of the complex in CDCl3 solution. The geometry of the compound in the presence of chloroform as implicit solvent was simulated by means of DFT calculations, together with possible mechanisms related to the fluxionality. The reversible dissociation of one of the pyrazole rings from the Cu(I) coordination sphere resulted in an accessible process.
A series of diiron/tetrairon compounds containing a S- or a Se-function (
-
,
-
,
-
,
), and the monoiron FeCp(CO){SeC
(NMe
)C
HC
(Me)} (
) were prepared from the diiron μ-vinyliminium precursors Fe
...Cp
(CO)( μ-CO){ μ-η
: η
-C
(R')C
HC
N(Me)(R)}CF
SO
(R = R' = Me,
; R = 2,6-C
H
Me
= Xyl, R' = Ph,
; R = Xyl, R' = CH
OH,
), via treatment with S
or gray selenium. The new compounds were characterized by elemental analysis, IR and multinuclear NMR spectroscopy, and structural aspects were further elucidated by DFT calculations. The unprecedented metallacyclic structure of
was ascertained by single crystal X-ray diffraction. The air-stable compounds (
,
-
,
-
,
) display fair to good stability in aqueous media, and thus were assessed for their cytotoxic activity towards A2780, A2780cisR, and HEK-293 cell lines. Cyclic voltammetry, ROS production and NADH oxidation studies were carried out on selected compounds to give insights into their mode of action.
The diazoalkane complexes Ru(η5-C5Me5)(N2CAr1Ar2){P(OR)3}LBPh4 (1–4) R = Me, L = P(OMe)3 (1); R = Et, L = P(OEt)3 (2); R = Me, L = PPh3 (3); R = Et, L = PPh3 (4); Ar1 = Ar2 = Ph (a); Ar1 = ...Ph, Ar2 = p-tolyl (b); Ar1Ar2 = C12H8 (c); Ar1 = Ph, Ar2 = PhC(O) (d) and Ru(η5-C5Me5){N2C(C12H8)}{PPh(OEt)2}(PPh3)BPh4 (5c) were prepared by allowing chloro-compounds RuCl(η5-C5Me5)P(OR)3L to react with the diazoalkane Ar1Ar2CN2 in the presence of NaBPh4. Treatment of complexes 1–4 with H2O afforded 1,2-diazene derivatives Ru(η5-C5Me5)(η2-NHNH){P(OR)3}LBPh4 (6–9) and ketone Ar1Ar2CO. A reaction path involving nucleophilic attack by H2O on the coordinated diazoalkane is proposed and supported by density functional theory calculations. The complexes were characterized spectroscopically (IR and 1H, 31P, 13C, 15N NMR) and by X-ray crystal structure determination of Ru(η5-C5Me5)(N2CC12H8){P(OEt)3}2BPh4 (2c) and Ru(η5-C5Me5)(η2-NHNH){P(OEt)3}2BPh4 (7).
The preparation and oxidation with Pb(OAc)4 of both mono- and bis(hydrazine) complexes of iridium(III) are described.
Display omitted
•Preparation of half-sandwich mono- and bis(hydrazine) complexes ...of iridium.•Oxidation of hydrazine complexes gives mono- and bis(aryldiazene) derivatives.•Insertion of aryldiazonium cations into the IrH bonds of dihydride.
Chloro complexes IrCl2(η5-C5Me5)P(OR)3 (1) (RMe, Et) were prepared by reacting dimer IrCl2(η5-C5Me5)2 with phosphites in alcohol. Treatment of 1 with R1NHNH2 gave monohydrazine complexes IrCl(η5-C5Me5)(R1NHNH2){P(OR)3}BPh4 (2, 3, 4) R1H (2), Me (3), Ph (4). Bis(hydrazine) complexes Ir(η5-C5Me5)(R1NHNH2)2{P(OR)3}(BPh4)2 (5, 6) were prepared by reacting chloro complexes first with AgOTf and then with an excess of hydrazine. Oxidation with Pb(OAc)4 at −40°C of both mono- and bis(hydrazine) complexes afforded phenyldiazene derivatives IrCl(η5-C5Me5)(PhNNH){P(OR)3}BPh4 (7) and Ir(η5-C5Me5)(PhNNH)2{P(OR)3}(BPh4)2 (9). Bis(aryldiazene) Ir(η5-C5Me5)(PhNNH)2{P(OR)3}(BPh4)2 (9, 10) were also prepared by allowing hydride IrH2(η5-C5Me5)P(OR)3 (8) to react with aryldiazonium cations ArN2BF4. The complexes were characterised spectroscopically and by X-ray crystal structure determination of IrCl(η5-C5Me5)(NH2NH2){P(OEt)3}BPh4 (2b) and IrCl(η5-C5Me5)(CH3NHNH2){P(OEt)3}BPh4 (3b).
The reaction of Pt6(CO)6(SnCl2)2(SnCl3)44– (1) with CO under atmospheric pressure resulted in the new Pt6(CO)8(SnCl2)(SnCl3)44– (2) cluster by the addition of two CO ligands and the elimination of a ...stannylene SnCl2 group. In turn, 2 reacted with 2 equivalents of PPh3 under a CO atmosphere to afford Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)22– (3) by elimination of two stannyl SnCl3– ligands. Conversely, the reaction of 2 with 2 equivalents of PPh3 under a N2 atmosphere resulted in a species tentatively formulated as Pt6(CO)5(SnCl2)2(SnCl3)2(PPh3)22– (4–5CO) on the basis of 13C NMR, 31P NMR spectroscopy and ESI‐MS studies. Compounds 2–4 were spectroscopically characterized by IR spectroscopy and multinuclear (13C and 31P) variable‐temperature NMR spectroscopy. The crystal structures of 2 and 3 were determined by means of single‐crystal X‐ray diffraction, and their bonding was computationally investigated by DFT calculations. The possible structure of 4–5CO was predicted by means of DFT methods.
The stepwise addition of CO and PPh3 to Pt6(CO)6(SnCl2)2(SnCl3)44– results in the new Pt6(CO)8(SnCl2)(SnCl3)44– and Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)22– bimetallic clusters. These clusters show perfect segregation of the two metals and are composed of a zero‐valent Pt6 core decorated on the surface by CO, PPh3, SnCl2, and SnCl3– ligands.
The reaction of Pt 15 (CO) 30 2− with increasing amounts of SnCl 2 affords Pt 8 (CO) 10 (SnCl 2 ) 4 2− ( 2 ), Pt 10 (CO) 14 {Cl 2 Sn(OH)SnCl 2 } 2 2− ( 5 ), Pt 6 (CO) 6 (SnCl 2 ) 2 (SnCl 3 ) 4 4− ...( 3 ), Pt 9 (CO) 8 (SnCl 2 ) 3 (SnCl 3 ) 2 (Cl 2 SnOCOSnCl 2 ) 4− ( 4 ) and Pt 5 (CO) 5 {Cl 2 Sn(OR)SnCl 2 } 3 3− (R = H, Me, Et, and i Pr) ( 1-R ). 1-R and 2 have been previously described, whereas 3–5 are herein reported for the first time. The species 1–3 are the main products of the reaction under different experimental conditions, whereas 4 and 5 are by-products of the synthesis of 3 and 2 , respectively. From a structural point of view, the clusters 1–5 all show a perfect segregation of the two metals, which are composed of a low valent Pt core decorated on the surface by Sn( ii ) fragments such as SnCl 2 , SnCl 3 − , Cl 2 Sn(OH)SnCl 2 − and Cl 2 SnOCOSnCl 2 2− . These fragments behave as two electron donor ligands via each Sn-atom (and also the C-atom in the case of Cl 2 SnOCOSnCl 2 2− ). The Cl 2 SnOCOSnCl 2 2− ligand is rather unique and may be viewed as a bis-stannyl-carboxylate, a carbon dioxide μ 3 :k 3 - C , O , O ′-CO 2 or a carbonite ion CO 2 2− stabilized by coordination to metal atoms. Compounds 1–5 have been fully characterised via IR spectroscopy, X-ray crystallography and DFT calculations.
PDF
