Synthesis of Neutral (PdII, PtII), Cationic (PdII), and Water-Induced Anionic (PdII) Complexes Containing New Mesocyclic Thioether−Aminophosphonite Ligands and Their Application in the Suzuki Cross-Coupling Reaction

P-Cl bond-induced lactamization of 2(2'-hydroxyl)phenyloxazoline to form a cyclic phosphinite, 3-(2-chloroethyl)-2-phenyl-2H-benzo[e][1,3,2]oxaza-phosphinin-4(3H)-one: synthesis, structural studies and transition metal complexes

The equimolar reaction between 2(2'-hydroxy)phenyloxazoline (1) and PPhCl2 in the presence of triethylamine afforded an unexpected cyclic product, phenyl-benzo-oxazaphosphininone (2), instead of a simple phosphinite derivative A. A similar reaction between 1 and PPhCl2 in 2 : 1 ratio also yielded the same product 2, but with one equivalent of 2(2'-hydroxy)phenyloxazoline (1) left unreacted. The formation of the cyclic product 2 is due to the P-Cl bond induced oxazoline ring opening followed by the formation of a six-membered γ-lactam type product, 3-(2-chloroethyl)-2-phenyl-2H-benzo[e][1,3,2]oxazaphosphinin-4(3H)-one (2 also referred to as L). The reactions of 2 with H2O2, elemental sulphur or elemental selenium yielded the corresponding chalcogenides, LE (3, E = O; 4, E = S; 5, E = Se) in quantitative yield. Treatment of 2 with [Ru(η(6)-Cymene)Cl2]2, [Pd(COD)Cl2] and [Pd(η(3)-C3H5)Cl]2 resulted in the formation of [RuCl2(η(6)-cymene)(L)] (6), [PdCl2{L}2] (7), and [Pd(η(3)-C3H5)Cl(L)] (8), respectively. The compound 2 obtained in the 2 : 1 reaction when treated with [Pd(η(3)-C3H5)Cl]2 gave the same palladium complex 8 (referred to as 9a), but co-crystallized with bis(oxazolyl)palladacycle (9b) as confirmed by single crystal X-ray analysis.

Structure and properties of metal complexes of a pyridine based oxazolidinone synthesized by atmospheric CO2 fixation

Copper, platinum and palladium complexes of an oxazolidinone ligand show potential in catalysis or cytotoxicity, depending on the metal incorporated.

Synthesis, transition metal chemistry and catalytic reactions of ferrocenylbis(phosphonite), [Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2]

The new metalloligand ferrocenylbis(phosphonite), [Fe(C5H4PR2)2 (R = OC6H3(OMe-o)(C3H5-p))], (2), is synthesized by the reaction of bis(dichlorophosphino)ferrocene Fe(C5H4PCl2)2 (1) with 4-allyl-2-methoxyphenol. The reactions of 2 with H2O2 and elemental sulfur or selenium afforded bischalcogenides, [Fe{C5H4P(E)(OC6H3(OMe-o)(C3H5-p))2}2] (3, E = O; 4, E = S; 5, E = Se), in good yield. The bis(phosphonite) reacts with group 6 metal carbonyls and group 10 metal dichloride precursors to produce the chelate complexes [{M(CO)4}Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2}] (6, M = Mo; 7, M = W) and [(MCl2)Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2] (8, M = Pd; 9, M = Pt). The palladium(ii) complex [(PdCl2)Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2] (8) is an efficient catalyst for the Suzuki-Miyaura cross-coupling reactions (TON up to 1.5 × 10(5)). The reaction of 2 with one equivalent of [RuCl2(η(6)-p-cymene)]2 yielded the binuclear complex [{Ru2Cl4(η(6)-p-cymene)2}Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2] (12) in good yield. Treatment of 2 with copper chloride in a 1 : 1 or 1 : 2 molar ratio resulted in the formation of a binuclear complex, [{(CuCl)Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2}2] (13), whereas a similar reaction of 2 with CuBr and CuI in a 1:2 or 1:2.5 molar ratio yielded the novel butterfly-like deca-nuclear complexes [Cu5(μ-X)5{Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2}2]2 (14, X = Br; 15, X = I). The reaction of 2 with two equivalents of [AuCl(SMe2)] afforded the digold complex [(AuCl)2Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2] (16), with the ligand exhibiting bridged-bidentate mode of coordination. Additionally, some complexes were studied by cyclic voltammetry. The crystal structures of complexes 8, 9, 12, 15 and 16 were determined using X-ray diffraction studies.

Bi-, tetra-, and hexanuclear AuI and binuclear AgI complexes and AgI coordination polymers containing phenylaminobis(phosphonite), PhN{P(OC6H4OMe-o)2}2, and pyridyl ligands

The reactions of phenylaminobis(phosphonite), PhN{P(OC6H4OMe-o)2}2 (1) (PNP), with [AuCl(SMe2)] in appropriate ratios, afford the bi- and mononuclear complexes, [(AuCl)2(micro-PNP)] (2) and [(AuCl)(PNP)]2 (3) in good yield. Treatment of 2 with 2 equiv of AgX (X = OTf or ClO4) followed by the addition of 1 or 2,2'-bipyridine affords [Au2(micro-PNP)2](OTf)2 (4) and [Au2(C10H8N2)2(micro-PNP)](ClO4)2 (5), respectively. Similarly, the macrocycles [Au4(C4H4N2)2(micro-PNP)2](ClO4)4 (6), [Au4(C10H8N2)2(micro-PNP)2](ClO4)4 (7), and [Au6(C3H3N3)2(micro-PNP)3](ClO4)6 (8) are obtained by treating 2 with pyrazine, 4,4'-bipyridine, or 1,3,5-triazine in the presence of AgClO 4. The reaction of 1 with AgOTf in a 1:2 molar ratio produces [Ag2(micro-OTf)2(micro-PNP)] (9). The displacement of triflate ions in 9 by 1 leads to a disubstituted derivative, [Ag2(micro-PNP)3](OTf)2 (10). The equimolar reaction of 1 with AgClO4 in THF affords [Ag2(C4H8O)2(micro-PNP)2](ClO4)2 (11). Treatment of 1 with AgClO4 followed by the addition of 2,2'-bipyridine affords a discrete binuclear complex, [Ag2(C10H8N2)2(micro-PNP)](ClO4)2 (12), whereas similar reactions with 4,4'-bipyridine or pyrazine produce one-dimensional zigzag Ag (I) coordination polymers, [Ag2(C10H8N2)(micro-ClO4)(ClO4)(micro-PNP)]n (13) and [Ag2(C4H4N2)(micro-ClO4)(ClO4)(micro-PNP)]n (14) in good yield. The nature of metal-metal interactions in compounds 2, 4, 5, and 12 was analyzed theoretically by performing HF and CC calculations. The structures of the complexes 2, 4, 5, 7, 9, 12, and 14 are confirmed by single crystal X-ray diffraction studies.

Highly air-stable anionic mononuclear and neutral binuclear palladium(II) complexes for C-C and C-N bond-forming reactions

The short-bite aminobis(phosphonite), PhN{P(-OC10H6(mu-S)C10H6O-)}2 (2), containing a mesocyclic thioether backbone is synthesized by either treating PhN(PCl2)2 with 2 equiv of thiobis(2,2'-naphthol) or reacting chlorophosphite (-OC10H6(mu-S)C10H6O-)PCl (1) with aniline in the presence of a base. Treatment of 2 with an equimolar amount of Pd(COD)Cl2 in the presence of H2O affords a P-N-P-bridged and P,S-metalated binuclear complex, [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2Pd2Cl2{P(-OC10H6(mu-S)C10H6O-)(O)-kappaP,kappaS}2] (3), whereas the same reaction with 2 equiv of Pd(COD)Cl2 in the presence of H2O and Et3N produces the mononuclear anionic complex [{(-OC10H6(mu-S)C10H6O-)P(O)-kappaP,kappaS}PdCl2](Et3NH) (5). By contrast, reaction of 2 with 2 equiv of Pd(COD)Cl2 and H2O in the absence of Et3N gives the hydrogen phosphonate coordinated complex [{(-OC10H6(mu-S)C10H6O-)P(OH)}PdCl2] (4) which converts to the anionic complex in solution or in the presence of a base. Compound 2 on treatment with Pt(COD)X2 (X = Cl or I) afforded P-coordinated four-membered chelate complexes [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2PtX2] (6 X = Cl, 7 X = I). The crystal structures of compounds 2, 3, 5, and 7 are reported. Compound 3 is the first example of a crystallographically characterized binuclear palladium complex containing a bidentate bridging ligand and its hydrolyzed fragments forming metallacycles containing a palladium-phosphorus sigma bond. All palladium complexes proved to be very good catalysts for the Suzuki-Miyaura and Mizoroki-Heck cross-coupling and amination reactions with excellent turnover numbers (TON up to 1.46 x 105 in the case of the Suzuki-Miyaura reaction).

Metal unsaturation and ligand hemilability in Suzuki coupling

The combinative and complementary use of a hemilabile difunctional ligand on a metal, notably palladium, that is coordinatively and electronically unsaturated has led to the isolation of a string of unexpected low-valent complexes that are structurally intriguing. The ligands of interest are primarily ferrocenes functionalized by [P,N] and [P,O] donors. The characterization of these active Suzuki catalysts, which support sp(2)-sp(2) couplings, give valuable insights into the key Suzuki intermediates such as those arising from the reductive elimination, transmetallation, and oxidative addition steps. In this Account, we shall review and discuss our recent results in relation to selected developments in other laboratories.

Copper(I) Complexes of Bis(2-(diphenylphosphino)phenyl) Ether: Synthesis, Reactivity, and Theoretical Calculations

The tricoordinated cationic Cu(I) complex [Cu(kappa2-P,P'-DPEphos)(kappa1-P-DPEphos)][BF4] (1) (DPEphos = bis(2-(diphenylphosphino)phenyl) ether) containing a dangling phosphorus center was synthesized from the reaction of [Cu(CH3CN)4][BF4] with DPEphos in a 1:2 molar ratio in dichloromethane. When complex 1 is treated with MnO2, elemental sulfur, or selenium, the uncoordinated phosphorus atom undergoes oxidation to form a P=E bond resulting in the formation of complexes of the type [Cu(kappa2-P,P'-DPEphos)(kappa2-P,E-DPEphos-E)][BF4] (2, E = O; 3, E = S; 4, E = Se) containing a Cu-E bond. The zigzag polymeric CuI complex [Cu(kappa2-P,P'-DPEphos)(micro-4,4'-bpy)]n[BF4]n (5) was prepared by the reaction of [Cu(CH3CN)4][BF4] with DPEphos and 4,4'-bipyridine in an equimolar ratio. The stereochemical influences of DPEphos on its coordination behavior are examined by density functional theory calculations.