Methyleneimine CH2dNH as a Unidentate Ligand in Rhenium Complexes This work was supported by MIUR (Rome)—Programmi di Ricerca Scientifica di Rilevante Interesse Nazionale, Cofinanziamento 2000–2001. We thank Daniela Baldan for technical assistance (original) (raw)
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Journal of Organometallic Chemistry, 2007
The reaction of the labile compound [Re 2 (CO) 8 (CH 3 CN) 2 ] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re 2 (CO) 8 (C 14 H 10 N 4 )] (1 and 2), and the complex [Re 2 (CO) 8 (C 14 H 10 N 4 )Re 2 (CO) 8 ] (3). In 1, the ligand is r,r 0 -N,N 0 -coordinated to a Re(CO) 3 fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b] = 7 in solution, detected by 1 H NMR (À50°C, CD 3 COCD 3 ), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO) 3 fragments through two (r,r 0 -N,N 0 ) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re 2 (CO) 6 (C 14 H 10 N 4 ) 2 ] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand r,r 0 -N,N 0 -coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.
Biochemical and Biophysical Research Communications, 2010
A series of pyridine-and bipyridine-containing leucotriarylmethane ligands has been successfully synthesised and incorporated into tricarbonyl rhenium(I) diimine complexes. The X-ray crystal structures of two of the complexes have also been determined. The photoreactivity, photophysical and electrochemical properties of these ligands and their rhenium complexes were investigated. The photo-ionisation of the leucotriarylmethanes in the free ligands and their metal complexes and the subsequent change in absorption properties were also studied. Additionally, the electrochemistry of these ligands and complexes were investigated.
Polynuclear Re IV M II (M II = first-row transition-metal ion) complexes are usually obtained from an halide-based rhenium(IV) precursor acting as ligand against a 3d transition metal ion. This synthetic strategy seems not to proceed as expected when [ReBr 4 (mal)] 2and Fe 2+ are considered. Indeed, the reaction of (PPh 4 ) 2 [ReBr 4 (mal)] with Fe(ClO 4 ) 2 ·6H 2 O in the presence of 2,9-dimethyl-1,10-phenanthroline (dmphen) in acetonitrile unexpectedly afforded the complex (Hdmphen)(H 2 dmphen) 0.5 [Re IV Br 4 (mal)]. The metal ion is observed in a slight distorted octahedral coordination environment in which malonato exhibits a boat conformation. Protonation of two dmphen provides the charge to balance the anionic complex. One of them is resolved as monoprotonated, the other one beingobserved as diprotonated but located on a two-fold symmetry axis of the space group.The crystallographic structure shows several non-covalent interactions, namely, - stacking and different H-bonds connecting water molecules of crystallization. Theoretical Density Functional (DFT) studies on geometry and electronic properties were performed employing B3LYP and PBE1PBE. The general trends observed in the crystallographic data are well reproduced in the calculations. Calculated bond lengths and angles reasonably match the values obtained from the X-ray diffraction study. Time-dependent DFT (TD-DFT) calculations helped us in assigning the origin of all absorption bandsexperimentally observed.
Synthesis and structural studies on bivalent metal complexes of benzenesulphonylhydrazine
Transition Metal Chemistry, 1987
Benzenesulphonylhydrazine (HB) reacts with bivalent metal ions either in the keto-or enol forms. The complexes have been characterized by spectral (u.v., i.r., n.m.r.,), magnetic and thermal (d.t.a., d.t.g, t.g., d.s.c.) measurements. I.r. spectra suggest that HB is monodentate coordinating via NH or NH2, depending on the medium of the reaction. The participation of the O:S:O group in bonding via bridge-formation in a polymeric chain is also considered. The substitution of ethanol in the Co u complex, [(CoBzEtOH),], by H20, pyridine or acetonitrile was also investigated.
Inorganica Chimica Acta, 2003
The ligand (2-pyridinecarboxaldehyde) benzoylhydrazone (HNN?O) has been reacted with [Rh 2 (m-Cl) 2 (CO) 4 ] in diethyl ether, isolating the carbonyl complex [Rh(k 2 -HNN?)(CO)Cl] (1), where the neutral ligand coordinates the metal through the nitrogen atoms, the amidic oxygen been excluded by the coordination sphere. Repeated attempts aimed to force the ligand to an anionic tridentate coordination, both by prior deprotonation of the free ligand or deprotonation of 1, have resulted in extensive deposition of metallic rhodium. The reaction between HNN?O and [Rh 2 (m-Cl) 2 (CO) 4 ] in basic media and in the presence of PPh 3 , has led to the isolation of the complex [Rh(k 2 -N?O)(PPh 3 )(CO)] ×/1/2CH 2 Cl 2 (2), where the anionic ligand is N?O bidentate. Compound 1 has been reacted with an excess of MeI in CH 2 Cl 2 or THF, isolating [Rh(k 2 -HNN?)(CH 3 CO)ClI] (4) and [Rh(k 2 -HNN?)(CH 3 CO)(THF)ClI] (5), respectively. Although the oxidative addition step is practically instantaneous in both cases, the migratory insertion step results faster in THF, as established by liquid film IR spectroscopy. Compound 2 has been reacted with MeI in THF isolating the complex [Rh(k 2 -N?O)(PPh 3 )(CO)(Me)I] (6), which, however, does not transform into the corresponding acyl complex. The crystal structure of complex 2 ×/1/4CH 2 Cl 2 has been solved. #
Rhenium complexes of tris(pyrazolyl)methanes and sulfonate derivative
Dalton Transactions, 2006
The trioxo [ReO 3 {SO 3 C(pz) 3 }] (1) (pz = pyrazolyl) and oxo [ReOCl{SO 3 C(pz) 3 }(PPh 3 )]Cl compounds with tris(pyrazolyl)methanesulfonate were obtained by treatment of Re 2 O 7 or [ReOCl 3 (PPh 3 ) 2 ], respectively, with Li[SO 3 C(pz) 3 ], whereas [ReCl 3 {HC(pz) 3 }] (3), [ReCl 3 {HC(3,5-Me 2 pz) 3 }] (4) and [ReCl 4 {g 2 -HC(pz) 3 }] (5) were prepared by reaction of [ReOCl 3 (PPh 3 ) 2 ] (3,4) or [ReCl 4 (NCMe) 2 ] with hydrotris(pyrazolyl)methane HC(pz) 3 (3,5) or hydrotris(3,5-dimethyl-1pyrazolyl)methane HC(3,5-Me 2 pz) 3 (4). [ReO{SO 3 C(pz) 3 }{OC(CH 3 ) 2 pz}][ReO 4 ] 6, with a chelated pyrazolyl-alkoxide, was derived from an unprecedented ketone-pyrazolyl coupling on reaction of crude 1 with acetone. The compounds have been characterized by elemental analyses, IR and NMR spectroscopies, FAB-MS spectrometry and cyclic voltammetry and, in the case of 5 and 6, also by single-crystal X-ray diffraction. The electrochemical E L Lever parameter has been estimated, for the first time, for the SO 3 C(pz) 3 − and oxo ligands allowing the measurement of their electron-donor character and comparison with other ligands. Compounds 1, 2 and 6 appear to be the first tris(pyrazolyl)methanesulfonate complexes of rhenium to be reported.
Journal of Organometallic Chemistry, 2006
Sodium dihydrobis(2-mercaptothiazolyl)borate, Na[H 2 B(tiaz) 2 ], reacts with (NEt 4 ) 2 [Re(CO) 3 Br 3 ] in water to afford fac-[Re{j 3 -H(l-H)B(tiaz) 2 }(CO) 3 ] (1). In a similar manner, treatment of the same Re(I) starting material with bis(2-mercaptoimidazolyl)methane, H 2 C(tim Me ) 2 , yields fac-[ReBr{j 2 -H 2 C(tim Me ) 2 }(CO) 3 ] (2). The organometallic complexes 1 and 2 have been characterized by IR, 1 H and 13 C NMR spectroscopy, and also by X-ray crystallographic analysis. X-ray diffraction analysis revealed the presence of a short B-HÁ Á ÁRe interaction in the case of 1, and the absence of C-HÁ Á ÁRe interactions in the crystal structure of 2. For both compounds the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. The three remaining coordination positions are occupied by the two thione sulfur atoms from the anchor ligands, and by an agostic hydride (1) or a bromide ligand (2). Compound 1 is highly stable either in the solid state or in solution. In particular, its B-HÁ Á ÁRe interaction is retained in solution, even in coordinating solvents, namely acetonitrile, dimethylsulfoxide and tetrahydrofuran. Unlike 1, compound 2 is only moderately stable in acetonitrile, undergoing a slow release of the bis(2-mercaptoimidazolyl)methane.
Journal of Chemical Crystallography, 2010
The molecular and crystal structures of (E)-4-O 2 NC 6 H 4 NHN=CMeCH 2 CO 2 R 1 (4: R 1 = Me; 5: R 1 = Et) and (E)-PhNHN=CPhCH 2 CONHPh (6) are reported from data collected at 120(2) K. The major intermolecular interactions in both 4 and 5 involve the hydazonyl NH and the carbonyl oxygen, with formation of symmetric dimers. Due to 4 and 5 each having different sets of additional intermolecular interactions, different supramolecular arrays are produced: molecules of 4 are linked into a three-dimension structure, while zigzag chains of molecules of 5 are obtained. Chains of molecules of 6, prepared from PhNHNH 2 and PhCOCH 2 CONHPh, are obtained from intermolecular hydrogen bonds involving amido NH and carbonyl oxygen moieties. Further interactions, C-H-p(arene), C-H-O and p-p stacking interactions in 6 produces a three dimensional array. Compound 4 crystallizes in the triclinic space group P-1 with a = 7.7027(2) Ǻ , b = 7.8103(2) Ǻ , c = 11.1761(3) Ǻ , a = 77.054(2)°, b = 79.425(2)°, c = 81.097(2)°. Compound 5 crystallizes in the triclinic space group P-1 with a = 5.6323(2)Ǻ , b = 9.9695(3)Ǻ , c = 11.0286(4)Ǻ , a = 91.859(2)°, b = 102.034(2)°, c = 98.898(3)°. Compound 6 crystallizes in the monoclinic space group P21/c with a = 10.4255(8)Ǻ , b = 10.4255(8)Ǻ , c = 9.3368(5)Ǻ , b = 113.780(4)°.