NMR and X-ray characterization of a platinum(II) complex with (−)sparteine

Intini, Francesco P.; Pacifico, Concetta; Pellicani, Raffaella Z.; Roca, Virginia; Natile, Giovanni

doi:10.1016/j.ica.2007.04.008

Cited by 8 publications

(2 citation statements)

References 31 publications

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“…While there are many examples of sparteine acting as an L 2 -type ligand to palladium (eq ), − the gray crystals obtained from mixing (−)-sparteine and Pd(OAc) 2 in acetone instead consist of (sparteinyl)Pd(μ-OC(CH 3 )O) 2 Pd(μ-OC(CH 3 )O) 2 Pd(sparteinyl) ( 4 ), the result of C−H activation at a bridgehead position of sparteine (crystal and refinement data are shown in Table ). The resulting trimetallic complex contains three palladium atoms (Figures and ), in an approximately linear arrangement (∠Pd1−Pd2−Pd3 = 176.03°; Pd−Pd ≈ 2.9 Å), each exhibiting square-planar geometry.…”

Section: Resultsmentioning

confidence: 99%

Robotic Lepidoptery: Structural Characterization of (mostly) Unexpected Palladium Complexes Obtained from High-Throughput Catalyst Screening

et al. 2009

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In the course of a high-throughput search for optimal combinations of bidentate ligands with Pd(II) carboxylates to generate oxidation catalysts, we obtained and crystallographically characterized a number of crystalline products. While some combinations afforded the anticipated (L-L)Pd(OC(O)R)2 structures (L-L = bipyridine, tmeda; R = CH3, CF3), many gave unusual oligometallic complexes resulting from reactions such as C−H activation (L-L = sparteine), P−C bond cleavage (L-L = 1,2-bis(diphenylphosphino)ethane, and C−C bond formation between solvent (acetone) and ligand (L-L = 1,4-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene). These findings illustrate potential pitfalls of screening procedures based on assuming uniform, in situ catalyst self-assembly.

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Section: Resultsmentioning

confidence: 99%

Robotic Lepidoptery: Structural Characterization of (mostly) Unexpected Palladium Complexes Obtained from High-Throughput Catalyst Screening

et al. 2009

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“…4c The first platinum complex of (-)-sparteine was structurally characterized only very recently, in 2008. 8 In order to further our understanding of the properties of transition metal sparteine complexes, we structurally characterized for the first time a rhodium complex of sparteine and also studied its dynamic behaviour in solution. [((-)-Sparteine)Rh(h 4 -COD)] + (1 + ; COD = 1,5-cyclooctadiene) was characterized using X-ray crystallography and multi-nuclear ( 1 H, 13 C) NMR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a rhodium-sparteine complex, [((−)-sparteine)Rh(η4-COD)]+: Crystal structure and DNMR/DFT studies on ligand-rotation dynamics

et al. 2010

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A cationic rhodium-sparteine complex, [((-)-sparteine)Rh(eta(4)-COD)](+) (1(+); COD = 1,5-cyclooctadiene) was obtained, isolated as its tetrafluoroborate salt (1BF(4)), and characterized using X-ray crystallography and multinuclear ((1)H, (13)C) NMR spectroscopy. This is the first structurally characterized sparteine complex of rhodium. The Rh-N bonds are unusually long (2.214(3) and 2.242(3) A), apparently due to steric repulsion between COD and sparteine. (1)H NMR exchange experiments (EXSY) demonstrate a dynamic process that results in an overall 180 degrees rotation of the COD methine protons in solution (CD(2)Cl(2)) with a first-order rate constant of 460 s(-1) at the coalescence temperature (314 K) and interpolated rate constant of 150 s(-1) at 298 K. Temperature-dependent NMR studies yield DeltaH(++) = 13.0 +/- 0.3 kcal mol(-1), DeltaS(++) = -5 +/- 1 cal mol(-1) K(-1), such that DeltaG(298)(++) = 14.3 +/- 0.3 kcal mol(-1). DFT studies (B3LYP) indicate that the loosely bound (-)-sparteine ligand rotates through a pseudo-tetrahedral transition state where both ligands are rotated approximately 90 degrees relative to each other. While both ligands remain bound (eta(4)-COD, kappa(2)-sparteine), bonding to sparteine is weakened much more than bonding to COD in the transition state. DFT computed DeltaG(298)(++) and DeltaS(++) values (15.55 kcal mol(-1) and -2.67 cal mol(-1) K(-1), respectively) agree very well with the experimental values. Attempts to find alternative mechanisms involving partial dechelation of COD and (-)-sparteine yielded slightly higher barriers along with positive DeltaS values for intermediate formation.

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Palladium Sparteine Dichloride

Sigman¹,

Liao²

2012

Encyclopedia of Reagents for Organic Synthesis

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NMR and X-ray characterization of a platinum(II) complex with (−)sparteine

Cited by 8 publications

References 31 publications

Robotic Lepidoptery: Structural Characterization of (mostly) Unexpected Palladium Complexes Obtained from High-Throughput Catalyst Screening

Robotic Lepidoptery: Structural Characterization of (mostly) Unexpected Palladium Complexes Obtained from High-Throughput Catalyst Screening

Characterization of a rhodium-sparteine complex, [((−)-sparteine)Rh(η4-COD)]+: Crystal structure and DNMR/DFT studies on ligand-rotation dynamics

Palladium Sparteine Dichloride

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