Rhenium complexes of di-2-pyridyl ketone, 2-benzoylpyridine and 2-hydroxybenzophenone: A structural and theoretical study (original) (raw)
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Rhenium Tricarbonyl Complexes of Azodicarboxylate Ligands
Molecules
The excellent π-accepting azodicarboxylic esters adcOR (R = Et, iPr, tBu, Bn (CH2-C6H5) and Ph) and the piperidinyl amide derivative adcpip were used as bridging chelate ligands in dinuclear Re(CO)3 complexes [{Re(CO)3Cl}2(µ-adcOR)] and [{Re(CO)3Cl}2(µ-adcpip)]. From the adcpip ligand the mononuclear derivatives [Re(CO)3Cl(adcpip)] and [Re(CO)3(PPh3)(µ-adcpip)]Cl were also obtained. Optimised geometries from density functional theory (DFT) calculations show syn and anti isomers for the dinuclear fac-Re(CO)3 complexes at slightly different energies but they were not distinguishable from experimental IR or UV–Vis absorption spectroscopy. The electrochemistry of the adc complexes showed reduction potentials slightly below 0.0 V vs. the ferrocene/ferrocenium couple. Attempts to generate the radicals [{Re(CO)3Cl}2(µ-adcOR)]•− failed as they are inherently unstable, losing very probably first the Cl− coligand and then rapidly cleaving one [Re(CO)3] fragment. Consequently, we found signals...
Organometallics, 1994
Reduction of Re(O)I(RC*R)2 (2) or [Re(O)(RC*R)212 by two electrons gives Re(0)-(RC=CR)zNa (R = Me, l a ; Et, lb; Ph, IC). Compounds 1 are unusual oxo complexes, being highly nucleophilic and strongly reducing. X-ray structures of la-crypt and lc92MeCN reveal Re(O)(RC=CR)2 units, as isolated anions in the former but, in the latter, connected via Na-0-Na bridges into centrosymmetric dimers. The acetylene ligands lie in a plane that is roughly perpendicular to the Re-0 bond, but the C=C vectors are splayed rather than parallel. The bond lengths and angles about rhenium are quite similar in the two structures, and quite close to the values found for 2 in which the splaying occurs to accommodate the iodide ligand. Reduction of 2a to la-crypt causes a lengthening of the R e 0 bond from 1.697(3) to 1.745(7) A and a drop in Y&O from 975 to 869 cm-l, both indicative of a decrease in the Re-0 bond order. The Re-C distances and C e C stretching frequencies both decrease on reduction, indicating increased Re acetylene back-bonding in 1. Effective core potential calculations on Re(O)(HC=CH)2-(A), Re(O)H(HC=CH)2 (B), Re(0)Cb-(C), and Re(O)FS (D) have been performed with excellent agreement between the calculated structures and experimental crystallographic data (A and B are models for 1 and 2). The Re-0 bonds in the high-oxidation-state oxo complexes C and D follow the classical Ballhausen-Gray picture, with little mixing between the Re-0 orbitals and orbitals on other ligands. In contrast, the frontier molecular orbitals in A and B exhibit significant delocalization over the rhenium, the oxygen, and the acetylene ligands. In A, the HOMO is an orbital largely Re d X y in character, accounting for the high nucleophilicity at rhenium in 1. The second-highest molecular orbital, only 0.8 eV below the HOMO, has significant Re-0 a-antibonding and Re-acetylene aback bonding character, which provides a rationalization for the reduced Re-0 bond order and strong back-bonding observed. There is also a ligand-based nonbonding orbital delocalized over the oxo and the acetylene ligands, as observed in other three-coordinate compounds involving acetylenes. Connections between the calculated electronic structure and the chemistry of 1 are emphasized.
KIMIKA
A number of transition metal complexes have been investigated as potential electrocatalystsfor C02 reduction. Among these are rhenium monometallic complexes, which have shownunique activity towards C02 reduction. Further development of multimetallic systems,capable of storing multiple equivalents of electrons has shown some potential in increasingthe selectivity of the C02 conversion processes toward highly reduced products. This studyreports the synthesis and characterization of novel polynuclear rhenium(I) complexes whererhenium is incorporated to the bridging ligand tppq (2,3,7,8-tetra-2-pyridylpyrazino[2,3-g]quinoxaline), which is capable of attaching up to four metal centers. The resultingcomplexes were characterized using different spectroscopic techniques (infrared, UV-Vis,emission) and cyclic voltammetry. The results suggest that the synthetic procedure adoptedwas successful.
Transition Metal Chemistry, 2019
Rhenium(I) and (VII) complexes with cyclohex-1-enylolonium cation and bridging pyridyl derivatives are reported. Additionally, the CO-bridged pyridyl and their related compounds have shown interesting behaviour in their reactivity towards compounds containing two amino groups. The unusual cationic compound: (2,6-diaza-cyclohex-1-enylolonium)2-aza-benzoate (H 2 den), was isolated from the reaction mixture of 1,2-di(pyridin-2-yl)ethane-1,2-dione with propane-1,3-diamine in methanol. The latter ligand: H 2 den, was used in the synthesis of rhenium(I) complex in its reaction with [Re(CO) 5 Cl] that gave rise to novel rhenium(I) complex fac-[Re(CO) 3 (Hhdm)] (1). The surprising aspect in the formation of (1) is the modification of H 2 den which was stabilized into a coordinated six-membered pyrimidine ring, 1,4,5,6-tetrahydropyrimidin-2-yl) di(pyridin-2-yl)methanol (H 2 hdm) chelate. The derived ligand acts as a tridentate monoanionic N 2 ,O-donor ligand towards the fac-[Re(CO) 3 ] + core. Surprisingly, the 2-aza-benzoate counter-ion that was present in the used ligand is not displayed in the crystal structure of complex 1, and might have been stabilized into 2-aza-benzoic acid (picolinic acid). The reaction of the potential tridentate N 2 ,O-donor ligand 2,2′-dipyridylketone (dpk) with trans-[ReOI 2 (OEt)(PPh 3) 2 ] led to the isolation of [ReO 3 (dpk•OH)] (2). The ligand H 2 den and the rhenium complexes were spectroscopically characterized, and the structures of H 2 den, 1 and 2 were established by X-ray diffraction.
Organometallics, 1995
Reaction of Re(C0)3(PPh3)&1 with MeC(CH2PPh2)3 (triphos) gives (triphos)Re(CO)zCl(l) which is converted to the hydride (triphos)Re(CO)aH (2) by treatment with LiAlh. An X-ray diffraction analysis of 2 shows that the rhenium atom is octahedrally coordinated by triphos, which occupies a triangular face of the coordination polyhedron, by two carbonyl groups and by a terminal hydride ligand. Treatment of 2 with Me30BF4 results in the evolution of methane and formation of the unsaturated complex [(triphos)Re(C0)2lBF4 (4) which is stabilized by a n agostic interaction between the rhenium center and a phenyl C-H bond of triphos. The q2-H2 complex [(triphos)Re(CO)2(Hz)IBF4 (3) is obtained either by protonation of 2 or by addition of H2 to the agostic complex 4. The presence of a n intact dihydrogen ligand in 3 is unambiguosly shown by 'H NMR spectroscopy [TI,,, = 8.6 ms (CD2C12, 300 MHz,-58 "C); JHD of 30.8 Hz for the monodeuteriated isotopomer [(triphos)Re(C0)2(HD)]-BF4 (3-ddI. Vinylidene derivatives of the formula [(triphos)Re(CO)~({C=C(H)R}lBP~ (R = Ph, 8; C02Et, 9; CsH13, 10) are obtained by reaction of either the q2-H2 complex 3 or the agostic complex 4 with terminal alkynes in the presence of N a B P b. The preference for the coordination of neutral groups a t rhenium in the [(triphos)Re(CO)zl+ fragment follows the order N2 C-H(agostic, < H2 < H C W R < CH3CN < CO. All the reactions described have been carried out in tetrahydrofuran or dichloromethane. formation of linear carbon chains C, (n = 1-5) between
Journal of Organometallic Chemistry, 2005
The complexes [ReCl 2 {N 2 C(O)Ph}(Hpz)(PPh 3 ) 2 ] (1) (Hpz = pyrazole), [ReCl 2 {N 2 C(O)Ph}(Hpz) 2 (PPh 3 )] (2), [ReCl 2 (HCpz 3 )-(PPh 3 )][BF 4 ] (3) and [ReCl 2 (3,5-Me 2 Hpz) 3 (PPh 3 )]Cl (4) were obtained by treatment of the chelate [ReCl 2 {g 2 -N,O-N 2 C(O)Ph}(PPh 3 ) 2 ] (0) with hydrotris(1-pyrazolyl)methane HCpz 3 (1,3), pyrazole Hpz , hydrotris(3,5-dimethyl-1-pyrazolyl)methane HC(3,5-Me 2 pz) 3 (4) or dimethylpyrazole 3,5-Me 2 Hpz (4). Rupture of a C(sp 3 )-N bond in HCpz 3 or HC(3,5-Me 2 pz) 3 , promoted by the Re centre, has occurred in the formation of 1 or 4, respectively. All compounds have been characterized by elemental analyses, IR and NMR spectroscopy, FAB-MS spectrometry, cyclic voltammetry and, for 1 AE CH 2 Cl 2 and 3, also by single crystal X-ray analysis. The electrochemical E L Lever parameter has been estimated, for the first time, for the HCpz 3 and the benzoyldiazenide NNC(O)Ph ligands.
Polyhedron, 1997
Under mild conditions [ReX(CO),(THF),] reacts with pyrazolylmethylpyridines to form the complexes fat-[ReX(CO),(BPz)] and fat-[ReX(CO),(BMPz)] (X = Cl, Br, or I; BPz = 2,6-bis(pyrazol-l-ylmethyl)pyridine ; BMPz = 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine) that involve BPz and BMPz acting as non-fluxional bidentate chelate ligands. Under more severe reaction conditions fuc-[ReX(CO),(BPz)] is converted to@-[Re(CO),(BPz)]X (X = Cl, Br, or I). Trimethylplatinum(IV)iodide reacts with BPz to form fuc-[PtMe,(BPz)]I. The crystal structure offac-[ReI(CO)3(BMPz)] confirms the bidentate chelate bonding of BMPz with a N-Re-N angle of 85.8". 0 1997 Elsevier Science Ltd Keywords: rhenium; platinum; pyridine; pyrazol-1-yl.
Journal of the Brazilian …, 2006
Dois novos complexos zwitteriônicos de oxorrênio(V), [ReOCl 2 (Hdhp)(PPh 3)] (1) e [ReOBr 2 (Hdhp)(PPh 3)] (2) (H 2 dhp = 2,3-dihidroxipiridina), foram sintetizados e caracterizados por espectroscopia de absorção no infravermelho, ressonância magnética nuclear de 1 H e 31 P, análise elementar e determinação da estrutura cristalina e molecular por difração de raios X em monocristais. Os complexos apresentam geometria de coordenação octaédrica bastante distorcida, com os dois ligantes haletos arranjados em posições cis equatoriais, o ligante trifenilfosfina em posição trans a um dos haletos e o ligante Hdhpcoordenado de forma bidentada através de seus átomos de oxigênio, sendo um em posição trans ao ligante oxo e o outro em posição trans com relação ao outro haleto. Este ligante tem seu átomo de nitrogênio protonado. Os compostos 1 e 2 apresentam empacotamento cristalino bastante diferente, influenciado em ambos os casos por ligações de hidrogênio intermoleculares dos tipos N-H⋅⋅⋅X (X = Cl, Br) e N-H⋅⋅⋅O. Two novel zwitterionic oxorhenium(V) complexes, [ReOCl 2 (Hdhp)(PPh 3)] (1) and [ReOBr 2 (Hdhp)(PPh 3)] (2) (H 2 dhp = 2,3-dihydroxypyridine), were synthesized and characterized by infrared spectroscopy, 1 H and 31 P nuclear magnetic resonance, elemental analysis and crystal and molecular structure determination by X-ray diffraction on single crystals. Both complexes show distorted octahedral coordination geometry, with the halide ligands arranged in equatorial cis positions, the triphenylphosphine ligand in a trans position to one of the halides and the Hdhpligand coordinated in a bidentate form through its oxygen atoms, one in trans position to the oxo-ligand and the other in trans position to the second halide. The nitrogen atom of this ligand is protonated. Compounds 1 and 2 show quite different crystal packing, both influenced by hydrogen bonds of the types N-H⋅⋅⋅X (X = Cl, Br) and N-H⋅⋅⋅O.