221 research outputs found
Chemistry of ruthenium(II) alkyl binap complexes : novel bonding, cyclometalation, and P-C bond splitting
No full textReactions of the bis-isopropyl and bis-cyclohexyl alkyl Binap ligands, 8 and 9, respectively, with [RuCl2(eta(6)-p-cymene)](2) afford new dinuclear chloro-bridged Ru compounds which contain the Binap ligands as six- rather than four-electron donors. A backbone double bond proximate to one of the P-donors complexes the metal atom. NMR details of the olefin bonding plus isomerization reactions involving loss of the olefin complexation are reported. Reactions of 8 or 9 with [Ru(OAc)(2)(eta(6)-p-cymene)] result in slow P-C bond cleavage and cyclometalation, instead of affording the anticipated [Ru(OAc)(2)(Binap)] complex. The new cyclometalated complexes, 15 and 16, contain the complexed R2P-O(C=O)CH3 ligand and arise (presumably) via acetate attack at phosphorus with the electrons in the P-C bond moving to the ruthenium atom. The solid-state structure of one of these, the cyclohexyl analogue, 16, is reported and represents a rare structural example of a molecule with three different chelate ligands. The complexed R2P-O(C=O)CH3 ligand is readily hydrolyzed in wet triflic acid to afford the R2P(OH) donor and an eta(6)-arene ligand (via Ru-C protonation)
Phosphino-arene ruthenium complexes containing the phosphorus acid anion {P(=O)(OR)(2)} as P-donor
No full textThe cationic complex [Ru(OTf)(P(OH)Ph-2){Ph2P-(eta (6)-arene)}]OTf,2(2a=6'-diphenylphosphino-1'-naphthyl-eta (6)((1-6))-naphthalene, 2b = 6,6'-dimethoxy-2'-diphenylphosphino-eta (6)((1-6))-biphenyl), is shown to react with water/tert-butyl alcohol/THF mixtures to afford [Ru(P(=O)(OH)(2){Ph2P-(eta (6)-arene)}](2)(OTf)(2), 4. The solid-state structure of a derivative, [Ru{P(=O)(OH)(OMe)}{Ph2P-(naphthyl-eta (6)-naphthalene}](2)(OTf)(2), 6, is reported and found to possess extremely asymmetric eta (6)-arene bonding. Complexes 4 and 6, plus a mononuclear dimethoxy analogue, [Ru(P(=O)-(OMe)(2)(Ph2P-(naphthyl-eta (6)-naphthalene)](OTf), 8, represent the first examples of Ru-compounds that contain the phosphorus acid anion P(=O)(OR) 2 (R = H and/or Me) as an anionic P-donor ligand. PGSE diffusion measurements are shown to be helpful in distinguishing between dinuclear oxygen bridging species and their mononuclear analogues
Dialkyl effect on enantioselectivity: pi-stacking as a structural feature in P,N complexes of palladium(II)
No full textA phosphino,oxazoline P,N-bidentate ligand, 4, containing 3,5-di-tert-butylphenyl groups has been prepared. In the Heck arylation of dihydrofuran, 4 is shown to afford higher ee's than either 2 or 3, the unsubstituted and m-dimethylphenyl analogues, respectively. Several Pd(0) complexes of 4 are reported. The exchange dynamics of Pd(4)(dba) are shown to involve an interconversion of diastereomers via an intramolecular process. The X-ray structure for PdCl2(4), 8, was determined by X-ray diffraction methods. Comparison of data with PdCl2(2), 9, and PdCl2(3), 10, suggests that differing amounts of stacking influence the structures of these relatively simple Pd complexes, with 9 and 10 revealing the strongest, pi-pi interactions. An estimation of the van der Waals energies involved in the interaction supports a ca. 4 kcal/mol stabilization via pi-pi stacking
New chiral complexes of palladium(0) containing P,S- and P,P-bidentate ligands
No full textNew chiral complexes of Pd(O) containing either the bis(phosphine) (6,6'-dimethoxybiphenyl-2,2'-diyl)bis(3,5-di-tert -butylphenylphosphine) (MeO-BIPHEP, 1) or the phosphine-sulfur chelate (2,3,4,6-tetra-O-acetyl-1-{(2-diphenylphosphino)benzyl)thio) -beta-D-glucopyranose ((2-Ph2PC6H4CH2) -S-CHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O,2) have been prepared, and the solid-state structure of one of these, Pd(benzoquinone)(2), has been determined. These Pd(O) complexes reveal interesting solution dynamics, as shown by 2-dimensional exchange spectroscopy. For the MeO-BIPHEP derivatives, one can obtain useful structural insights based on the observed restricted rotation around the aryl(3,5-di-tert-butylphenl)P-C bonds
Binap and MeO-Biphep complexes of Ru(II) : dicationic ligands as 6e donors : unexpected cyclometallation in connection with P-C bond breaking
No full textA series of cationic and dicationic Ru-arene complexes with Binap (1a) and MeO-Biphep (1b) have been prepared. C-13 NMR studies are shown to be useful in connection with recognising the 6e-bonding mode of 1a and 1b in the dications [Ru(1a or 1b)(eta (6)-arene)](SbF6)(2) (8,9). Reaction of 8,9 with: (a) (Bu4N)(Ph3SiF2) leads to a cyclometallated product which arises via P-C bond breaking and P-F bond making; (b) methanol provides a straightforward synthesis of the corresponding hydrides. C-13 NMR p-cymene chemical shifts are reported
Piano-stool inversion in arene complexes of Ru(II) : modelling the transition state
No full textIn the solid-state, the [RuH(arene)(Binap)]CF3SO3, complexes, 1, arene = eta(6)-benzene and 2, arene = eta(6)-toluene, distort markedly from a classical three-legged piano-stool structure with the former having the P-Ru-P plane approximately perpendicular to the plane of the arene; this structure for 1 is what one would expect for a transition state leading from one diastereomer to another via inversion at ruthenium
Platinum induced C-H activation in aromatic aldehydes. Unusual J(Pt, H) coupling constants and structure of trans-dichloroquinoline-8-carboxaldehyde triethylphosphine platinum(II)
No full textThe role of pi-pi, stacking interactions in square planar palladium complexes. Combined quantum mechanics/molecular mechanics QM/MM studie
No full textDensity functional (DFT) studies and hybrid QM/MM-DFT calculations demonstrate the importance of pi-pi stacking interactions in determining the structural features of two exemplary d(8) palladium complexes, PdBr(p-NCC6H4)({S}-MeO-Biphep), 1, and PdBr(C6F5)-({S}-MeO-Biphep), 2. Despite the superficial similarity of the two compounds, the former shows marked distortions from square planar geometry, while the latter exhibits an almost ideal structure. Attractive pi-pi stacking interactions between two pairs of P-phenyl rings and the arene backbone of the MeO-Biphep are the main origin of the distortion in complex 1. The planar structure of complex 2 is preferred as a consequence of an additional stacking interaction between one P-phenyl ring and the pentafluorophenyl a-ligand. The artificial introduction of an analogous stacking interaction in complex 1 reestablishes an ideal square planar geometry, thus demonstrating that switching on/off specific pi-pi interactions distinctly alters the coordination geometry. These results reveal a previously unrecognized role for pi-pi stacking interactions in the stabilization of structural features in transition metal compounds. This suggests pi-pi stacking interactions as a potential new design principle in tailoring coordination compounds
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