Dicarbonylrhodium Complexes Research Articles

Bis(amidinato)germylenerhodium Complexes: Synthesis, Structure, and Density Functional Theory Calculations

The first monogermylenerhodium complexes stabilized by bulky amidinato ligands on the divalent germanium center have been synthesized and characterized by NMR spectroscopy and X-ray crystallography. Their stability strongly depends on the steric hindrance of the amidinato ligand. With trimethysilyl groups on the nitrogen atoms of the amidinato ligand, only the germylene oxide rhodium complex could be obtained; by contrast, with t-Bu groups, the germylenerhodium complex was isolated. In both cases, the formation of amidinatorhodium complexes was observed. The donating ability of the germylene ligand has been assessed from the CO stretching frequency of the corresponding dicarbonylrhodium complex and was confirmed by density functional theory calculations.

η5-1,2,3-Trisilacyclopentadienyl - A Ligand for Transition Metal Complexes: Rhodium Half-Sandwich and Ruthenium Sandwich

The lithium salt of 1,2,3-trisilacyclopentadienide [eta(5)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)](-) 1(-)*[Li(+)(thf)] reacted with an equivalent amount of Rh(CO)(2)(acac) in toluene to form the half-sandwich (trisilacyclopentadienyl)dicarbonylrhodium complex [eta(5)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)]Rh(CO)(2) 2. Pi-electron delocalization in the trisilacyclopentadienyl ring in 2 was manifested in the shielding of the ring atoms upon complexation, as well as by the observation of (1)J(Rh-C) and (1)J(Rh-Si) coupling constants. In the solid state, cyclic delocalization in 2 was seen in the diagnostic eta(5)-coordination of the heavy cyclopentadienyl ring to the Rh center and the remarkable flattening of the Si(3)C(2) five-membered ring. Reaction of 1(-)*[Li(+)(thf)] with 0.25 equiv of [Cp*RuCl](4) (Cp* = eta(5)-C(5)Me(5)) resulted in the formation of the sandwich complex Cp*Ru[eta(5)-((t)Bu(2)MeSi)(3)Si(3)C(2)Et(2)] 3 as the heavy analogue of ruthenocene.

New dicarbonyl- o-semiquinonato rhodium complexes

Two novel dicarbonyl rhodium complexes with 3,6-di- tert-butyl- o-semiquinones containing back bonded –OCH 3 and –F substituents were synthesized and characterized. The number of analogous dicarbonyl- o-semiquinonato rhodium complexes is discussed from the viewpoint of the phenomenon of “bending crystals”.

Thermodynamic properties of dicarbonyl rhodium o-semiquinonate complex whose crystals display photomechanical properties

In an adiabatic low-pressure calorimeter, the temperature dependence of the standard molar heat capacity of paramagnetic dicarbonyl rhodium complex with o-semiquinone (CO) 2Rh(SQ) has been determined in the range from T = (6 to 355) K mainly with an accuracy of about 0.3%. Over the ranges from T = (205 to 234) K, T = (266 to 315) K and T = (316 to 345) K physical transformations have been revealed and their enthalpies and entropies have been estimated. The experimental data were used to calculate the thermodynamic functions C p , m ∘ / R , Δ 0 T H m ∘ / ( R · K ) , Δ 0 T S m ∘ / R and Φ m ∘ = Δ 0 T S m ∘ - Δ 0 T H m ∘ / T (where R is the universal gas constant) between T = (0 and 355) K. The fractal dimension D in the heat capacity function of the fractal variant of Debye heat capacity theory has been evaluated.

Catalytic activity of dicarbonylrhodium complexes of aminobenzoic acid ligands on carbonylation of alcohol

Rhodium(I) complexes of the type, [Rh(CO) 2ClL] ( 1), where L=2-aminobenzoic acid ( a), 3-aminobenzoic acid ( b) and 4-aminobenzoic acid ( c), have been synthesised. Oxidative addition (OA) of complexes 1 with electrophiles like RI (R=CH 3, C 2H 5) produce Rh(III) complexes of the type [Rh(CO)(COCH 3)IClL] ( 2) and [Rh(CO)(COC 2H 5)IClL] ( 3). The OA reactions of complexes 1 with RI follow a two stage kinetics and the observed rate constants are in the order 1 b > 1 c > 1 a irrespective of stages. The complexes 1 show higher catalytic activity for carbonylation of methanol and ethanol than that of the well known species [Rh(CO) 2I 2] −.

(1-Phenyl-3-methyl-4-acetylpyrazolon-5-ato)rhodium(I) complexes, synthesis, structural and spectroscopical characterization: Reactivity of diolefin- and dicarbonyl-rhodium complexes toward N-, P- and O-donors

Novel complexes of rhodium(I) [Rh(diolefin)(Q″)] (where HQ″=1-phenyl-3-methyl-4-acetylpyrazol-5-one and diolefin=cycloocta-1,5-diene (COD), bicyclo[2.2.1]hepta-2,5-diene (NBD) or 1,5-hexadiene (HEX)) were synthesized and characterized by analytical and spectral data. [Rh(COD)(Q″)] interacts with 4,5-dimethyl-1,10-phenanthroline (Me 2Phen) and 2,2′-bipyridil (Bipy) yielding the cationic derivatives [Rh(COD)(Me 2Phen)](Q″)(H 2O), [Rh(COD)(Bipy)](Q″)(H 2O) upon displacement of the (Q″) − donor from the coordination sphere of the metal center. Whereas [Rh(COD)(Q″)] interacts with 2-benzoylpyridine (Bzpy) yielding the 1:1 adduct [Rh(COD)(Bzpy)(Q″)] in which Bzpy acts as N-monodentate donor. On the other hand the monodentate P-donors triphenylphosphine, triphenylphosphite, tricyclohexylphosphine and the bidentate bis(diphenylphosphino)ethane (DPPE) displace the COD ligand from [Rh(COD)(Q″)] giving the neutral derivatives [Rh(PR 3) 2(Q″)] (PR 3=PPh 3, or P(OPh) 3) and [Rh(DPPE)(Q″)](H 2O). HQ″ reacts with the dinuclear [Rh(CO) 2Cl] 2. The tetradentate cycloocto-tetraene (COT) reacts with [Rh(CO) 2(Q″)] yielding the derivative [Rh(CO) 2(HQ″)Cl] in which HQ″ acts as neutral monodentate O-donor ligand. Whereas in presence of NEt 3 HQ″ reacts with [Rh(CO) 2Cl] 2 yielding [Rh(CO) 2(Q″)]. In this complex, one molecule of CO can be replaced by one mole of Phen and Bipy or by two moles of PPh 3 and AsPh 3 yielding the derivatives [Rh(CO)(L) n (Q″)]·x(H 2O) (L=Me 2Phen or Bipy, n=1; L=PPh 3 or AsPh 3, n=2) whereas one mole of DPPE displaces both the molecules of CO, yielding [Rh(DPPE)(Q″)] yielding the derivative [Rh(COT)(Q″)]. The X-ray crystal structure determination of [Rh(COD)(Q″)] establishes that the rhodium atom is in a square planar configuration with two adjacent sites occupied by the (Q″) − ligand in the O 2-bidentate form (Rh–O distances=2.054(2) and 2.061(2) Å). The COD ring has a twisted boat conformation with Rh–C distances in the range 2.101(3)–2.110(3) Å. Comparison was made with structural data reported for several related tetracoordinated (COD)Rh(I) adducts.

Synthesis of µ-carbene and µ-carbyne complexes of rhodium and cobalt from substituted diazirines. Crystal structures of [Rh2(η5-C5Me5)2(CO)2{µ-C(C6H4F-4)(OMe)}] and [Rh2(η5-C5Me5)2(µ-CO)(µ-C6H4Me-4)][BPh4

The reaction of aryl(methoxy)diazirines with [M2(η5-C5Me5)2(µ-CO)2](M = Rh or Co) affords the µ-carbene complexes [M2(η5-C5Me5)(CO)2{µ-CR(OMe)}](R = aryl) in excellent yield. The carbonyl groups are terminal in the rhodium complexes, as demonstrated conclusively in an X-ray diffraction study, but bridging for the cobalt complex. Thermolysis of the rhodium complexes results in loss of CO and the formation of [Rh2(η5-C5Me5)2(µ-CO){µ-CR(OMe)}]. Protonation of either the mono- or di-carbonyl rhodium complex with HBF4 led to the formation of a stable cationic carbyne complex, [Rh2(η5-C5Me5)2(µ-CO)(µ-CR)][BF4]; the structure of the related [BPh4]– salt was established in a diffraction study. Dynamic processes in the complexes were investigated by variable-temperature NMR spectroscopy.

Rhodium(I)-Komplexe mit 2,5-Difurfurylpyrrol-Liganden / Rhodium(I) Complexes with 2,5-Difurfurylpyrrole Ligands

Abstract The 2.5-difurfurylpyrrole-O.N.O ligands 3a, b [R = CO2C2H5 (a). COCH, (b)] are obtained by reaction of the furanes l a , b with the 2,5-bis(chloromethyl)pyrrole 2 in the presence of SnCl4. Proton abstraction from 3a, b with NaH affords the sodium salts 4a-Na and 4b-Na. Exchange of the chlorine bridges in [μ-ClRh(Diol)]2 (5,5') (Diol = cyclooctadiene, norbornadiene) results in the formation of the 14-electron complexes (Diol)Rh(O.N.O) (6a,6'a). Addition of PPh3, yields the four-coordinated rhodium complexes (Diol)Rh(O.N.O)(PPh3) (7a,7'a). These compounds are also available in a reverse reaction sequence from 5,5', PPh3, and 4a-Na. The mononuclear rhodium complexes RhCl(Diol)(PPh3) (8,8') are isolated as intermediates. In 7a, 7'a the olefinic ligands are replaced by carbon monoxide to give the dicarbonyl rhodium complex (OC)2Rh(O.N.O)(PPh3) (9a) being detectable only in solution. The same result is achieved upon addition of CO to the compound (OC)Rh(O.N.O)(PPh,) (11a) which results bv the reaction of [μ-ClRh(CO)(PPh3)]2 (10) with 4a-Na. Oxidative addition of CH3I or H2 to 6a, 6 a, 7a, 7'a or 11a was not observed. 1H and 31P{1H} NMR investigations indicate that depending on the temperature the O.N.O ligand in the 14-electron rhodium complex 11a acts as tri- (11a-A), bi- (11a-B) and monodentate (IIa-C) ligands. respectively. 11a also reacts with PPh, to form the /ram-bis(phosphane)rhodium complex (PPh3)2Rh(CO)(O.N.O) (12a). 12a and the analogous complexes 12b and trans-(PMe3)2Rh(CO)(O,N.O) (14a) are obtained by action of ClRh(CO)L2 (13) (L = PPh3. PMe3) on 4a-Na and 4b-Na, respectively. The methylene bridges in the O.N.O ligand 3a are not oxidized, neither in the non-complexed (3a) nor in the complexed (12a) state. According to an X-ray structural analysis 14a crystallizes in the monoclinic space group P21/n with Z = 4. In 6a, 6'a, 7a, 7'a, 9a, 11a, 12a, b, and 14a the O.N.O ligand is always nitrogen bonded

Pentachlorothiophenolato- and diphenylpentachlorophenylphosphine complexes of rhodium(I) and platinum(II)

Pentachlorothiophenol reacts with [Fe(CO) 2(π-C 5H 5)] 2 to give [Fe(SC 6Cl 5)(CO) 2(π-C 5H 5)] and with the chloro-bridged complexes, [RhCl L 2] 2 ( L = CO; L 2 = cyclo-octa-1,5-diene, norbornadiene and dicyclopentadiene) in the presence of ethanol to give the thio-bridged complexes, [Rh(SC 6Cl 5) L 2] 2. Treatment of the dicarbonylrhodium complex with triphenylphosphine and diphenylpentachlorophenylphosphine affords the complexes R(SC 6Cl 5)(CO)(PPh 3) 2 and [Rh(SC 6Cl 5)(CO){P(C 6Cl 5)Ph 2} 2] respectively. However, the complexes [Rh(SC 6Cl 5) L 2] 2 ( L 2 = cyclo-octa-1,5- diene and norbornadiene) react with triphenylphosphite to afford [Rh(SC 6Cl 5){P(OPh) 3} 2] 2. Diphenylpentachlorophenylphosphine reacts with RhCl 3· xH 2O to give [RhCl{P(C 6Cl 5)Ph 2} 2] 2 and the reactions of the phospihnes, P(C 6Cl 5) 3, P(C 6Cl 5) 2Ph and P(C 6Cl 5)Ph 2 with various rhodium and platinum compounds have been studied. No complexes have been obtained with either P(C 6Cl 5) 3 or P(C 6Cl 5) 2Ph and displacement reactions indicate that the complexes, PtCl 2 L 2 increase in stability in the order of ligands ( L), As(C 6Cl 5)Ph 2 < P(C 6Cl 5Ph 2 < PPh 3.