Multinuclear NMR, X-ray, and DFT Studies on RhCl(diene)(phosphoramidite) Complexes

NMR, X-ray, and DFT studies on several [RhCl(diene)(phosphoramidite)] complexes suggest that both electronic and steric effects affect the nature of the olefin, chloride, and P-donor bonding. The X-ray study of [RhCl(1,5-COD)(phosphoramidite)] (phosphoramidite = (Binol)PN(CH(CH3)Ph)2) reveals an intramolecular selectivity in the back-bonding in which the C−C bond of the olefin trans to the Cl ligand is preferentially elongated. Two types of dynamic processes have been detected at ambient temperature in CD2Cl2 solution using 2-D NOESY methods: presumed phosphoramidite dissociation and diolefin rotation. The former is observed with both 1,5-COD and NBD. The latter is more selective in that the intramolecular dynamics for the NBD analogues are relatively fast, but those for the 1,5-COD compounds, barely detectable. DFT calculations suggest that the diolefin rotation proceeds over a tetrahedral transition state and that there is a smaller energy barrier for the NBD complexes relative to the analogous 1,5-COD species. Two bis phosphoramidite salts of the form [Rh(1,5-COD)(phosphoramidite)2]BF4 are reported

Structure, Bonding, and Dynamics of Several Palladium η³-Allyl Carbene Complexes

A series of Pd-allyl carbene complexes, [PdX(η3-C3H5)(IPr)], 1 (X = a, Cl−, b, Br−, c, I−, d, N3−, e, NCO−, f, SCN−, g, CN−, h, OAc−, i, OTf−, j, 4-Me-pyridine), have been studied by one- and two-dimensional NMR techniques. 13C, 1H, and phase-sensitive NOE NMR studies on these relatively simple complexes reveal that (a) the trans influence of the carbene carbon in 1 seems to be smaller than that found for PPh3 and other P-donor ligands, (b) the selective η3−η1 opening of the allyl is under electronic control, and (c) the rates of η3−η1 allyl isomerization depend on the X ligand. The solid-state structure of 1c is reported, as well as selected 15N chemical shift data for the coordinated carbene ligand

Structure, Bonding, and Dynamics of Several Palladium η³-Allyl Carbene Complexes

A series of Pd-allyl carbene complexes, [PdX(η3-C3H5)(IPr)], 1 (X = a, Cl−, b, Br−, c, I−, d, N3−, e, NCO−, f, SCN−, g, CN−, h, OAc−, i, OTf−, j, 4-Me-pyridine), have been studied by one- and two-dimensional NMR techniques. 13C, 1H, and phase-sensitive NOE NMR studies on these relatively simple complexes reveal that (a) the trans influence of the carbene carbon in 1 seems to be smaller than that found for PPh3 and other P-donor ligands, (b) the selective η3−η1 opening of the allyl is under electronic control, and (c) the rates of η3−η1 allyl isomerization depend on the X ligand. The solid-state structure of 1c is reported, as well as selected 15N chemical shift data for the coordinated carbene ligand

Multinuclear NMR, X-ray, and DFT Studies on RhCl(diene)(phosphoramidite) Complexes

NMR, X-ray, and DFT studies on several [RhCl(diene)(phosphoramidite)] complexes suggest that both electronic and steric effects affect the nature of the olefin, chloride, and P-donor bonding. The X-ray study of [RhCl(1,5-COD)(phosphoramidite)] (phosphoramidite = (Binol)PN(CH(CH3)Ph)2) reveals an intramolecular selectivity in the back-bonding in which the C−C bond of the olefin trans to the Cl ligand is preferentially elongated. Two types of dynamic processes have been detected at ambient temperature in CD2Cl2 solution using 2-D NOESY methods: presumed phosphoramidite dissociation and diolefin rotation. The former is observed with both 1,5-COD and NBD. The latter is more selective in that the intramolecular dynamics for the NBD analogues are relatively fast, but those for the 1,5-COD compounds, barely detectable. DFT calculations suggest that the diolefin rotation proceeds over a tetrahedral transition state and that there is a smaller energy barrier for the NBD complexes relative to the analogous 1,5-COD species. Two bis phosphoramidite salts of the form [Rh(1,5-COD)(phosphoramidite)2]BF4 are reported

Palladium-Allyl Phosphoramidite Complexes: Solid-State Structures and Solution Dynamics

Several mono-phosphoramidite and bis-phosphoramidite 2-methallyl and 1,3-diphenylallyl allyl complexes of Pd(II) have been prepared. The solid-state structure for one of these has been determined. The mono-phosphoramidite chloro-allyl complexes of Pd(II) exist in two isomeric forms in solution. 1H,1H NMR exchange spectroscopy reveals that the dinuclear species [Pd(μ-Cl)(η3-CH2C(Me)CH2)]2 is involved in the interconversion between the two isomers. There is evidence to suggest that phosphoramidite dissociation is not responsible for this exchange. The cationic η3-2-methallyl bis-phosphoramidite Pd complexes reveal nonequivalent 31P resonances, as a consequence of slow allyl dynamics and in agreement with the preliminary X-ray structure

Palladium-Allyl Phosphoramidite Complexes: Solid-State Structures and Solution Dynamics

Several mono-phosphoramidite and bis-phosphoramidite 2-methallyl and 1,3-diphenylallyl allyl complexes of Pd(II) have been prepared. The solid-state structure for one of these has been determined. The mono-phosphoramidite chloro-allyl complexes of Pd(II) exist in two isomeric forms in solution. 1H,1H NMR exchange spectroscopy reveals that the dinuclear species [Pd(μ-Cl)(η3-CH2C(Me)CH2)]2 is involved in the interconversion between the two isomers. There is evidence to suggest that phosphoramidite dissociation is not responsible for this exchange. The cationic η3-2-methallyl bis-phosphoramidite Pd complexes reveal nonequivalent 31P resonances, as a consequence of slow allyl dynamics and in agreement with the preliminary X-ray structure

Weak η²-Olefin Bonding in Palladium and Platinum Allyl Cationic Complexes Containing Chiral Monodentate Ligands with α-Phenyl Methyl Amine Side Chains

Detailed NMR studies on a series of Pd and Pt allyl complexes containing phosphoramidite ligands with NCH(CH3)Ph side chains are reported. When a coordination position becomes available, e.g., via abstraction of a chloride ligand, one double bond of the phenyl group of the side chain complexes to the metal, affording an η2-olefin structure. These allyl complexes exhibit a number of dynamic processes, and these have been elucidated via low-temperature NMR studies combined with 2D NOESY methods. DFT calculations confirm the ability of the amine side chain to coordinate to the metal almost without distortion, leading to a weak η2-arene−Pd bonding interaction (∼13 kcal mol−1). The latter result is supported by the NMR studies