Structural and Dynamic Studies on Amido-Bridged Rhodium and Iridium Complexes

Tejel, Cristina; Ciriano, Miguel A.; Bordonaba, Marta; López, José A.; Lahoz, Fernando J.; Oro, Luis A.

doi:10.1002/1521-3765(20020715)8:14<3128::aid-chem3128>3.0.co;2-f

Cited by 25 publications

(18 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To fully understand the NMR spectra of complexes 8 – 10 one has to consider the known butterfly‐like motion associated with dinuclear amido‐bridged d 8 complexes, which consists of a four‐membered metallacycle inversion, which is very fast on the NMR time scale. This dynamic process produces averaged NMR signals that reflect a planar “RhNRhN” core, a situation that has only been found for two diarylamido‐bridged rhodium complexes of the type [{Rh(μ‐NAr 2 )(cod)} 2 ] (Ar=phenyl, p ‐tolyl), because it is the most stable situation in terms of the avoidance of steric contacts between the sterically demanding aryl amido and COD ligands 39…”

Section: Resultsmentioning

confidence: 99%

“…This dynamic process produces averaged NMR signals that reflect a planar "RhNRhN" core, a situation that has only been found for two diarylamido-bridged rhodium complexes of the type [{RhA C H T U N G T R E N N U N G (m-NAr 2 )A C H T U N G T R E N N U N G (cod)} 2 ] (Ar= phenyl, p-tolyl), because it is the most stable situation in terms of the avoidance of steric contacts between the sterically demanding aryl amido and COD ligands. [39] Further addition of two extra molar equivalents of the respective phosphanes afforded tetraphosphane complexes (13)), which were isolated as brown-reddish solids in fairly good yields (Scheme 3). The NMR spectra of 11-13 Ir (1)ÀCl (1) 2.4344 (11) Ir (2)ÀCl (2) 2.4565(10) Ir (1)ÀN (1) 2.060 (3) Ir (2)ÀN (1) 2.053 (3) Ir (1)ÀN(2) 2.059 (3) Ir (2)ÀN (2) 2.062(4) Ir(1)À-M (1) 2.045 (4) Ir (2)-ÀM (3) 2.040(4) Ir (1)ÀM (2) 2.055(4) Ir(2)ÀM(4) 2.035(5) C(1)ÀC (2) 1.392(6) C(9)ÀC(10) 1.401(6) C(5)ÀC (6) 1.394 (6) C (13)ÀC (14) 1.396 (6) Ir (1)ÀIr (2) 2.6544(2) Cl(1)-Ir(1)-N (1) 87.13 (10) Cl (2)-Ir(2)-N(1) 87.56(10) Cl(1)-Ir(1)-N(2) 87.85 (11) Cl (2)-Ir(2)-N(2) 89.74(11) N(1)-Ir(1)-N(2) 78.88 (14) N(1)-Ir(2)-N(2) 78.97 (14) (15) [a] M(1), M(2), M(3), and M(4) represent the midpoints of the C(1)À C(2), C(5)ÀC(6), C(9)ÀC(10), and C(13)ÀC (14) olefinic bonds, respectively.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Terminal and Bridging Parent Amido 1,5‐Cyclooctadiene Complexes of Rhodium and Iridium

Mena

Jaseer

Garcı́a-Orduña

et al. 2013

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

The ready availability of rare parent amido d(8) complexes of the type [{M(μ-NH2)(cod)}2] (M=Rh (1), Ir (2); cod=1,5-cyclooctadiene) through the direct use of gaseous ammonia has allowed the study of their reactivity. Both complexes 1 and 2 exchanged the di-olefines by carbon monoxide to give the dinuclear tetracarbonyl derivatives [{M(μ-NH2)(CO)2}2 ] (M=Rh or Ir). The diiridium(I) complex 2 reacted with chloroalkanes such as CH2Cl2 or CHCl3, giving the diiridium(II) products [(Cl)(cod)Ir(μ-NH2)2Ir(cod)(R)] (R=CH2Cl or CHCl2) as a result of a two-center oxidative addition and concomitant metal-metal bond formation. However, reaction with ClCH2CH2Cl afforded the symmetrical adduct [{Ir(μ-NH2)(Cl)(cod)}2] upon release of ethylene. We found that the rhodium complex 1 exchanged the di-olefines stepwise upon addition of selected phosphanes (PPh3, PMePh2, PMe2Ph) without splitting of the amido bridges, allowing the detection of mixed COD/phosphane dinuclear complexes [(cod)Rh(μ-NH2)2Rh(PR3)2], and finally the isolation of the respective tetraphosphanes [{Rh(μ-NH2)(PR3)2}2]. On the other hand, the iridium complex 2 reacted with PMe2 Ph by splitting the amido bridges and leading to the very rare terminal amido complex [Ir(cod)(NH2)(PMePh2)2]. This compound was found to be very reactive towards traces of water, giving the more stable terminal hydroxo complex [Ir(cod)(OH)(PMePh2)2]. The heterocyclic carbene IPr (IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) also split the amido bridges in complexes 1 and 2, allowing in the case of iridium to characterize in situ the terminal amido complex [Ir(cod)(IPr)(NH2)]. However, when rhodium was involved, the known hydroxo complex [Rh(cod)(IPr)(OH)] was isolated as final product. On the other hand, we tested complexes 1 and 2 as catalysts in the transfer hydrogenation of acetophenone with iPrOH without the use of any base or in the presence of Cs2CO3, finding that the iridium complex 2 is more active than the rhodium analogue 1.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Terminal and Bridging Parent Amido 1,5‐Cyclooctadiene Complexes of Rhodium and Iridium

Mena

Jaseer

Garcı́a-Orduña

et al. 2013

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…On the other hand, the pattern of the 1 H and 13 C{ 1 H} NMR spectra of both cod complexes 3 and 4 at room temperature were similar to each other, indicating a dynamic motion which could not be frozen at À90 8C in [D 8 ]toluene. The D 2h symmetry detected, in contrast to the expected C 2v symmetry observed in the solid state, responded to a four-membered "MNMN" metallacycle inversion, [10] which is fast on the NMR time scale therefore producing averaged NMR signals that reflected a planar conformation.…”

mentioning

confidence: 91%

“…Ct represents the midpoints of the olefinic bonds. (2), mean Rh-Ct 2.003(5); N1-Rh1-N2 76.64 (9), N1-Rh2-N2 76.95 (10). Ct represents the midpoints of olefinic bonds.…”

mentioning

confidence: 99%

Direct Access to Parent Amido Complexes of Rhodium and Iridium through NH Activation of Ammonia

et al. 2011

Self Cite

View full text Add to dashboard Cite

Ammonia is a low-cost and potentially valuable building block for almost every nitrogen-containing compound required by industry. There is an obvious interest in utilizing this chemical as feedstock in catalytic organic transformations to produce higher-value products, an issue that has began to be explored with some degree of success.[1] However, most of late transition metal catalyzed reactions do not occur with ammonia. Several factors have been invoked to explain this lack of reactivity: [2] 1) The high strength of the NÀH bond of ammonia (107 kcal mol À1 ) makes its activation very difficult to achieve by metal centers; 2) the catalyst often deactivates through the formation of stable Werner ammine (M ! NH 3 ) adducts; and 3) the low acidity of ammonia prevents its participation in proton exchange reactions that could lead to NÀH activation.In order to achieve a metal-mediated functionalization of ammonia, an imperative requisite should be the formation of M À NH 2 bonds directly from ammonia (i.e. rather than leading to stable M ! NH 3 adducts).[3] So far, only few early examples involving interaction of NH 3 with iridium complexes followed an oxidative addition profile.[4] This concept was elegantly illustrated by Hartwig et al., who reported on the formal oxidative addition of ammonia to an electron-rich Ir I pincer system, leading to the first structurally characterized terminal amido hydrido Ir III complex. [5] In spite of the efficacy of this N À H activation, uptake and homolytic breakage of ammonia by late transition metal complexes still remains a difficult goal.[6] We assumed that a good approach to induce the formation of M À NH 2 bonds, circumventing the formation of Werner adducts, should rely on an appropriate design of organometallic precursors. Herein we report on a synthetic protocol that uses gaseous ammonia as "NH 2 " source to generate stable novel parent bridging and terminal amido Rh I and Ir I complexes under very mild conditions. We chose as metallic precursors dinuclear complexes bearing alkoxo-bridging ligands, well suited to induce NÀH activation. [7] In this way, treatment of the methoxo-bridged compounds [{M(m-OMe)(tfbb)} 2 ] (M = Rh, Ir; tfbb = tetrafluorobenzobarrelene) with gaseous ammonia in diethyl ether at atmospheric pressure rapidly afforded the parent amidobridged trinuclear complexes [{M(m 2 -NH 2 )(tfbb)} 3 ] (M = Rh (1), Ir (2)) which were isolated in good yields. On the other hand, reactions of the cod complexes [{M(m-OMe)(cod)} 2 ] (cod = 1,5-cycloctadiene) with gaseous ammonia yielded dinuclear amido-bridged complexes [{M(m-NH 2 )(cod)} 2 ] (M = Rh (3), Ir (4)) in excellent yields (Scheme 1). All the reactions leading to complexes 1-4 were found to be reversible. For example, monitoring by NMR spectroscopy the reaction of 3 with MeOH in a 1:1 ratio in [D 6 ]benzene showed upon 10 min, when the equilibrium was considered to be reached, the presence of unchanged 3, the original methoxo-bridged complex [{Rh(m-OMe)(cod)} 2 ] and the mixed amido-alkoxo species [{Rh(co...

show abstract

“…For 2, we were fortunate to obtain reliable X-ray diffraction data of a single crystal, [15] and the structure revealed a rhodium atom confined to an almost perfect tetrahedral with an overall C 3v symmetry resulting from its bonding to three equivalent phosphorus atoms of the tripodal PhBP 3 . The fourth site is represented by the imido ligand, having a Rh-N imido bond distance of 1.780 (2) , which is shorter by about 0.3 when compared to similar species having bridging amido or imido ligands, [10,13,16] but similar to that observed for [IrCp*NR]. [7] The short distance together with an almost linear Rh-N imido -C Ad angle [177.5 (2)8] are indicative of such ligands having a Rh=N multiple bond.…”

mentioning

confidence: 68%

Terminal Imido Rhodium Complexes

et al. 2014

Self Cite

View full text Add to dashboard Cite

Compounds of the late transition metals with M=X multiple bonds (X=CR2, NR, O) represent a synthetic challenge, partly overcome by preparative chemists, but with noticeable gaps in the second- and third-row elements. For example, there are no isolated examples of terminal imido rhodium complexes known to date. Described herein is the isolation, characterization, and some preliminary reactivity studies of the first rhodium complexes [Rh(PhBP3)(NR)] (PhBP3=PhB{CH2PPh2}3) with a multiple and terminal Rh=N bond. These imido compounds result from reactions of organic azides with the corresponding rhodium(I) complex having a labile ligand, and display a pseudo-tetrahedral core geometry with an almost linear Rh-N-C arrangement [177.5(2)°] and a short Rh-N bond [1.780(2) Å]. We also show that the Rh=N bond undergoes protonation at the nitrogen atom or addition of H2 , and also engages in nitrene-group transfer and cycloaddition reactions.

show abstract

Structural and Dynamic Studies on Amido-Bridged Rhodium and Iridium Complexes

Cited by 25 publications

References 6 publications

Terminal and Bridging Parent Amido 1,5‐Cyclooctadiene Complexes of Rhodium and Iridium

Terminal and Bridging Parent Amido 1,5‐Cyclooctadiene Complexes of Rhodium and Iridium

Direct Access to Parent Amido Complexes of Rhodium and Iridium through NH Activation of Ammonia

Terminal Imido Rhodium Complexes

Contact Info

Product

Resources

About