Palladium−Duphos Structural and Enantioselective Hydroarylation Chemistry

A series of Pd(II) complexes of 1,2-bis((2R,5R)-2,5-dimethylphospholano)benzene (MeDuphos; 1) have been prepared, and the solid-state structures for five of these, PdBr(p-CN-C6H4)(1), PdX(C6F5)(1) (X = Br, I), Pd(OAc)2(1), and [Pd(CH3CN)2(1)](PF6), have been determined by X-ray diffraction. Several of these complexes are catalyst precursors for the enantioselective hydroarylation of norbornene with PhX (X = Br, I, OTf). The maximum ee, 75%, is higher than the corresponding values previously reported for bidentate phosphine auxiliaries. NOESY NMR results show how complexed 1 interacts with the aryl ligand in PdBr(p-CN-C6H4)(1)

Conformational Changes and Anion−Cation Interactions in Palladium-Cyclometalated BINAP and Chiraphos Cationic Complexes. A Structural Study via NMR and X-ray Methods

The cyclometalated Pd complexes [Pd{(A or B)C6H3CHN(p-CH3C6H4)}(BINAP)](X) (8−13; X = PF6-, BArF-, CF3SO3-, A, B = meta or para ring substituent), [Pd{(C6H4CH(CH3)N(CH3)2)}{(S)- or (R)-BINAP)}](CF3SO3) (14a,b), and [Pd{(C6H4CH(CH3)N(CH3)2)}{(S,S)- or (R,R)-Chiraphos)}](CF3SO3) (15a,b) have been prepared, and five of these have been studied by X-ray diffraction. NMR Overhauser measurements reveal that the chiral cyclometalated amine chelate senses the change in the chirality, for both the BINAP and the Chiraphos auxiliaries, and responds by a conformational adjustment of the ring. 1H,19F-HOESY data for both 14 and 15 suggest differences between the diastereomers 14a,b (and 15a,b). PGSE diffusion data for these salts are reported

Conformational Changes and Anion−Cation Interactions in Palladium-Cyclometalated BINAP and Chiraphos Cationic Complexes. A Structural Study via NMR and X-ray Methods

The cyclometalated Pd complexes [Pd{(A or B)C6H3CHN(p-CH3C6H4)}(BINAP)](X) (8−13; X = PF6-, BArF-, CF3SO3-, A, B = meta or para ring substituent), [Pd{(C6H4CH(CH3)N(CH3)2)}{(S)- or (R)-BINAP)}](CF3SO3) (14a,b), and [Pd{(C6H4CH(CH3)N(CH3)2)}{(S,S)- or (R,R)-Chiraphos)}](CF3SO3) (15a,b) have been prepared, and five of these have been studied by X-ray diffraction. NMR Overhauser measurements reveal that the chiral cyclometalated amine chelate senses the change in the chirality, for both the BINAP and the Chiraphos auxiliaries, and responds by a conformational adjustment of the ring. 1H,19F-HOESY data for both 14 and 15 suggest differences between the diastereomers 14a,b (and 15a,b). PGSE diffusion data for these salts are reported

A New P,S-Chiral Auxiliary Derived from Thioglucose. X-ray Structure of a Palladium 1,3-Diphenylallyl Complex with a Strongly Rotated Allyl Ligand

The new ferrocene-based P,S-chiral auxiliary 1, derived from thioglucose, has been prepared and used in the palladium-catalyzed enantioselective allylic alkylation reaction. The X-ray structure of the allyl cationic complex [Pd(η3-PhCHCHCHPh)(1)]CF3SO3 (2) reveals a markedly rotated 1,3-diphenylallyl ligand such that the terminal allyl carbon C(3), trans to the phosphorus donor, is ca. 0.85(3) Å below the coordination plane. This distortion is pertinent to the Pd(0) transition state complex expected in the allylic alkylation reaction

Conformational Changes and Anion−Cation Interactions in Palladium-Cyclometalated BINAP and Chiraphos Cationic Complexes. A Structural Study via NMR and X-ray Methods

The cyclometalated Pd complexes [Pd{(A or B)C6H3CHN(p-CH3C6H4)}(BINAP)](X) (8−13; X = PF6-, BArF-, CF3SO3-, A, B = meta or para ring substituent), [Pd{(C6H4CH(CH3)N(CH3)2)}{(S)- or (R)-BINAP)}](CF3SO3) (14a,b), and [Pd{(C6H4CH(CH3)N(CH3)2)}{(S,S)- or (R,R)-Chiraphos)}](CF3SO3) (15a,b) have been prepared, and five of these have been studied by X-ray diffraction. NMR Overhauser measurements reveal that the chiral cyclometalated amine chelate senses the change in the chirality, for both the BINAP and the Chiraphos auxiliaries, and responds by a conformational adjustment of the ring. 1H,19F-HOESY data for both 14 and 15 suggest differences between the diastereomers 14a,b (and 15a,b). PGSE diffusion data for these salts are reported

Conformational Changes and Anion−Cation Interactions in Palladium-Cyclometalated BINAP and Chiraphos Cationic Complexes. A Structural Study via NMR and X-ray Methods

The cyclometalated Pd complexes [Pd{(A or B)C6H3CHN(p-CH3C6H4)}(BINAP)](X) (8−13; X = PF6-, BArF-, CF3SO3-, A, B = meta or para ring substituent), [Pd{(C6H4CH(CH3)N(CH3)2)}{(S)- or (R)-BINAP)}](CF3SO3) (14a,b), and [Pd{(C6H4CH(CH3)N(CH3)2)}{(S,S)- or (R,R)-Chiraphos)}](CF3SO3) (15a,b) have been prepared, and five of these have been studied by X-ray diffraction. NMR Overhauser measurements reveal that the chiral cyclometalated amine chelate senses the change in the chirality, for both the BINAP and the Chiraphos auxiliaries, and responds by a conformational adjustment of the ring. 1H,19F-HOESY data for both 14 and 15 suggest differences between the diastereomers 14a,b (and 15a,b). PGSE diffusion data for these salts are reported

Chemistry of Ruthenium(II) Alkyl Binap Complexes: Novel Bonding, Cyclometalation, and P−C Bond Splitting

Reactions of the bis-isopropyl and bis-cyclohexyl alkyl Binap ligands, 8 and 9, respectively, with [RuCl2(η6-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(η6-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 η6-arene ligand (via Ru−C protonation)

Conformational Changes and Anion−Cation Interactions in Palladium-Cyclometalated BINAP and Chiraphos Cationic Complexes. A Structural Study via NMR and X-ray Methods

The cyclometalated Pd complexes [Pd{(A or B)C6H3CHN(p-CH3C6H4)}(BINAP)](X) (8−13; X = PF6-, BArF-, CF3SO3-, A, B = meta or para ring substituent), [Pd{(C6H4CH(CH3)N(CH3)2)}{(S)- or (R)-BINAP)}](CF3SO3) (14a,b), and [Pd{(C6H4CH(CH3)N(CH3)2)}{(S,S)- or (R,R)-Chiraphos)}](CF3SO3) (15a,b) have been prepared, and five of these have been studied by X-ray diffraction. NMR Overhauser measurements reveal that the chiral cyclometalated amine chelate senses the change in the chirality, for both the BINAP and the Chiraphos auxiliaries, and responds by a conformational adjustment of the ring. 1H,19F-HOESY data for both 14 and 15 suggest differences between the diastereomers 14a,b (and 15a,b). PGSE diffusion data for these salts are reported

Contributions to the Enantioselective Heck Reaction Using MeO−Biphep Ligands. The Case Against Dibenzylidene Acetone

It is shown that the Pd-catalyzed enantioselective Heck reaction of p-XC6H4OTf, X = OMe, H, CO2Me, with dihydrofuran gives higher enantioselectivities when the chelating diphosphine MeO−Biphep, 1a, is replaced with its disubstituted analogue 3,5-di-tert-butyl MeO−Biphep, 1b. The phenylation of 5-methyl-2,3-dihydrofuran produces a new dihydrofuran containing a quaternary stereogenic center (ee, >98% with 1b, ca. 20% with 1a). Catalytic results for the reaction of phenyl triflate with dhf, together with stoichiometric oxidative addition reactions of aryl halides on Pd complexes of 1, show that the use of Pd(dba)(1), dba = dibenzylidene acetone, slows the oxidative addition relative to the reaction in which the Pd(0) precursor is generated from PdCl2(1) + NaBH4. The solid-state structures for two PdI(aryl)(1a), 3, derivatives, aryl = p-MeOOC−C6H4(3a) and C6F5 (3b) are reported

⁷Li PGSE Diffusion Measurements on LiPPh₂: A Solvent Dependence of the Structure

The first application of 7Li pulsed-gradient spin−echo (PGSE) diffusion methods to structural lithium chemistry is reported. The data, which provide quantitative diffusion constants at 155 K, lead to a new method of estimating solvent viscosity at this temperature and clearly show a solvent dependence for the structure of LiPPh2. In THF, LiPPh2 exists as a mononuclear solvated species, whereas in Et2O, a dinuclear structure is found. D values for the model compound PHPh2 in THF have been measured