Developing five-membered heterocycle substituted phosphinous acids as ligands for palladium-catalyzed Suzuki-Miyaura and Catellani reactions.

A new category of secondary phosphine oxides (SPOs) (5a-5j) with/without benzo-fused five-membered heterocyclic substituents were prepared. These new compounds are air- and moisture-stable ligands and have the advantage of long-term storage. Some of the ligands as well as ligand coordinated palladium complexes (6f' and 6f'') and platinum complexes (7b_trans & 7i_trans) were prepared and their structures were determined using single crystal X-ray diffraction methods.

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions.

A series of general and selective Pd(II)-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO) ligated palladium complex (6) as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields.

Density functional studies on diimine chelated palladium complex catalyzed Suzuki-Miyaura cross-coupling reaction: the impact of Lewis base employed in transmetallation process.

The transmetallation processes of disubstituted diimine (RN=CH-CH=NR) chelated palladium complexes catalyzed Suzuki-Miyaura cross-coupling reactions of phenyl chloride (PhCl) and phenylboronic acid [B(OH)(2)Ph] in the presence of diverse Lewis bases (OH(-), F(-), O(t)Bu(-), CO(3)(2-) and PO(4)(3-)) were studied by DFT methods with the B3LYP functional. Activation strain model has also been employed to investigate the extent of deformation of the reactants including the catalyst in the transition state. The transmetallation processes for all the cases are exothermic.

Bis[1,3(η)-all-yl][μ-2(η)-1,3-bis-(di-phenyl-phosphino)-2,4-diphenyl-cyclo-buta-1,3-diene-1:3κP:P']dichlorido-1κCl,3κCl-[2(η)-isopropyl-cyclo-penta-dien-yl]-2-cobalt(I)-1,3-dipalladium(II) dichloro-methane solvate.

In the title complex, [CoPd(2)(C(3)H(5))(2)(C(8)H(11))Cl(2)(C(40)H(30)P(2))]·CH(2)Cl(2), the Co(I) atom is sandwiched between the cyclo-penta-dienyl and cyclo-butadiene rings. The two diphenyl-phosphine substituents of the cyclo-butadiene ring are situated opposite to each other and bind two Pd(II) atoms, which are additionally coordinated by a chloride ion and the three C atoms of an allyl ligand, forming a distorted planar coordination environment. The Cl atoms of the dichloro-methane solvent mol-ecule (equal occupancies) and one C atom and its attached H atom of each of the allyl ligands (occupancies 0.

{μ-2-[(Benzothia-zol-2-yl-2κN)hydrazonomethyl-2κN]-6-methoxy-phenolato-1:2κO,O:O}{2-[(benzo-thia-zol-2-yl-1κN)hydrazonomethyl-1κN]-6-methoxy-phenolato-1κO}(methanol-2κO)(nitrato-2κO)dicopper(II) nitrate.

The title complex, [Cu(2)(C(15)H(12)N(3)O(2)S)(2)(NO(3))(CH(3)OH)]NO(3), has two Cu(II) centres coordinated by two deprotonated 2-[(benzothia-zol-2-yl)hydrazonometh-yl]-6-methoxy-phenol ligands, a methanol mol-ecule and a nitrate ion. Both Cu(II) centres are penta-coordinated in a distorted square-pyramidal fashion. The crystal structure is stabilized by N-H⋯O and O-H⋯O hydrogen bonds.

Density functional studies on palladium-catalyzed Suzuki-Miyaura cross-coupling reactions assisted by N- or P-chelating ligands.

DFT studies with the B3LYP functional have been carried out on the Suzuki-Miyaura cross-coupling reactions of phenyl chloride and phenylboronic acid catalyzed by palladium complexes with N- or P-chelating ligands. The full catalytic cycle, from the addition of reactants to the catalyst to the release of the cross-coupled product from the complexed intermediate, has been examined. The stages within the cycle, such as oxidative addition, transmetalation, and reductive elimination, were validated by linking the mechanistically relevant intermediates and transition states.

Oxygen insertion in a carbon-phosphorus bond of the phenylethynyl-di-(tert-butyl)-phosphine bridged dicobalt complex: exploring the nature of oxygen migration using DFT.

In the process of isolation under aerobic conditions phenylethynyl-di-(tert-butyl)-phosphine bridged dicobalt complex [(micro-PPh(2)CH(2)PPh(2))Co2(CO)4(micro,eta-PhC[triple bond]CP(t-Bu)2)] 4a underwent a partial oxidation. The identity of the oxidized product, [(micro-PPh(2)CH(2)PPh(2))Co2(CO)4(micro,eta-PhC[triple bond]C-O-P([double bond]O)(t-Bu)2)] 5, was established by spectroscopic means as well as the single-crystal X-ray diffraction method. This is the first crystallographic evidence that unambiguously supports the formation of an organometallic version of a phosphinate ester.

Experimental and DFT study of the tautomeric behavior of cobalt-containing secondary phosphine oxides.

New cobalt-containing secondary phosphine oxides [(mu-PPh(2)CH(2)PPh(2))Co(2)(CO)(4){mu,eta-PhC[triple chemical bond]CP(==O)(H)(R)}] (8 a: R=tBu; 8 b: R=Ph) were prepared by reaction of secondary phosphine oxides PhC[triple chemical bond]CP- (==O)(H)(R) (6 a: R=tBu; 6 b: R=Ph) with dppm-bridged dicobalt complex [(mu-PPh(2)CH(2)PPh(2))Co(2)(CO)(6)] (2). The molecular structures of 8 a and 8 b were determined by single-crystal X-ray diffraction. Although palladium-catalyzed Heck reactions employing 8 b as ligand gave satisfying results, 8 a performed poorly in the same reaction.

Density functional studies of dicobalt octacarbonyl-mediated azobenzene formation from 4-ethynylaniline.

Two adiabatic potential-energy surfaces are employed for probing the processes of [Co2(CO)8]-mediated C6H5N=NC6H5 formation from NH2C6H5. Elementary steps, including oxidative addition of the coordinated amine proton to the cobalt center, reductive elimination of H2, CO association, and the coupling process of the diamino fragments, are modeled and examined by using DFT methods at the B3 LYP/631 LAN level. The formation of C6H5N=NC6H5 from NH2C6H5 through reductive coupling is a thermodynamically unfavorable process.

Preparation and NMR studies of cobalt-containing diphosphine ligand chelated W, Ru, Au and Pd complexes: Suzuki cross-coupling reactions and carbonylation catalyzed by the Pd complex.

Treatment of a cobalt-containing diphosphine ligand, [[mu-P,P-PPh2CH2PPh2]Co2(CO)4[mu-PPh2C[triple bond]CPPh2]] 1 with metal complexes W(CO)6, Ru3(CO)12, AuCl(tht)(tht = tetrahydrothiophene) and (COD)PdCl2(COD = 1,5-cycloctadiene) gave 1-chelated metal complexes [(1)W(CO)4], [(mu-1)Ru3(CO)10] 4, [(1)(AuCl)2] 5 and [(1)PdCl2] 6, respectively. All these compounds were characterized by spectroscopic means whereas 3, 4 and 6 were also studied by X-ray diffraction. These compounds display chelating and bridging modes of metal-phosphine complexation.