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The coordination properties of the beta-keto phosphine ligands R(2)PCH(2)C(O)Ph (, R = i-Pr; , R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)(2)PNHC(O)Me () and of Ph(2)PNHC(O)Me () have been examined towards Ni(ii) complexes. Comparisons are made between systems in which the PCH(2) function of the ketophosphine has been replaced with an isoelectronic PNH group in amide-derived ligands, or the PCH functionality of phosphinoenolates with a PN group in phosphinoiminolate complexes. Furthermore, ligands and reacted with [(eta(5)-C(5)H(5))CoI(2)(CO)] to afford the phosphine mono-adducts [(eta(5)-C(5)H(5))CoI(2){Ph(2)PCH(2)C(O)Ph}] () and [(eta(5)-C(5)H(5))CoI(2){Ph(2)PNHC(O)Me}] (), respectively, which upon reaction with excess NEt(3) yielded the phosphinoenolate complex [(eta(5)-C(5)H(5))[upper bond 1 start]CoI{Ph(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}] () and the phosphinoiminolate complex [(eta(5)-C(5)H(5))[upper bond 1 start]CoI{Ph(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}] (), respectively. The complexes cis-[[upper bond 1 start]Ni{(i-Pr)(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}(2)] () and cis-[[upper bond 1 start]Ni{Ph(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}(2)] () were obtained similarly from NiCl(2) and (3) and (4), respectively, in the presence of a base. The phosphinoenolate complex [[upper bond 1 start]Ni{(i-Pr)(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}(2)] () exists in ethanol as a mixture of the cis and trans isomers, in contrast to cis-[[upper bond 1 start]Ni{(Ph(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}(2)], and the solid-state structure of the trans isomer of was established by X-ray diffraction. The structures of the ligand (3) and of the complexes , in .3/2CH(2)Cl(2), , and have also been determined by X-ray diffraction and are compared with those of related complexes. Complexes , and contain a five-membered heteroatomic metallocyclic moiety, which is constituted by five different chemical elements. The structural consequences of the steric bulk of the P substituents and of the electronic characteristics of the P,O chelates are discussed.

The ligand (i-Pr)2PCH2(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO2CF3) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes (P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)2PCH2(oxazoline)}]2(OTf)2 (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]2 to be characterized by X-ray crystallography.

The zwitterionic N,N‘-dialkyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium derivatives [C6H2(NHCH2CH2X)2(O)2] (X = NMe2, 9; X = NHEt, 10; X = OMe, 11), previously prepared from 4,6-diaminoresorcinol by a transamination reaction, and 12 (X = N(CH2CH2)2O) behave as tridentate ligands when reacted with [Ni(acac)2] to form the corresponding octahedral Ni(II) 2:1 complexes (13−16), respectively. In contrast, ligand 9 reacted | with NiCl2·6H2O in a tandemlike manner to afford the stabilized Ni(II) zwitterionic organometalate 1:1 complex (17). The bonding parameters | of complexes 13·H2O·CH2Cl2 and 17, determined by X-ray diffraction, and the conformation of the ligands around the nickel center as well as the supramolecular arrangements are discussed and compared with those of their previously reported Zn(II) analogues. Complexes 13−17 were tested in catalytic ethylene oligomerization with MAO and AlEtCl2 as cocatalysts. Complex 17 yielded the highest turnover frequencies, with values up to 20 300 and 48 200...

The initial CO-ethylene or CO-methyl acrylate insertion steps into the Pd-Me bond of methylpalladium(II) complexes with (phosphinomethyl)oxazoline ligands, leading to metallacycles, have been fully characterized, including by X-ray diffraction.

Strontium hexamethyldisilazide, combined with a chiral bis(sulfonamide) ligand, was found to be very effective for the catalytic asymmetric Michael addition of malonate to chalcone derivatives.

A novel catalyst system based on a chiral strontium complex which promotes the catalytic asymmetric Michael addition reactions of malonates to enones has been developed. The conjugate addition reactions proceeded smoothly in the presence of 5 mol % of the chiral strontium catalyst, at room temperature, to afford the desired adducts in high yields and excellent enantioselectivities. This method provides an efficient approach to the preparation of building blocks possessing various functional groups and possible sites for further functionalization.

Cobalt(ii) complexes of the type [CoCl(2)(P,N)], where P,N represents a heterobidentate phosphino- or phosphinito-oxazoline-type ligand, have been synthesised and characterised by infrared spectroscopy and elemental analysis. Their molecular structures were established by single-crystal X-ray diffraction in the solid state. Whereas the phosphino-oxazoline complex [CoCl(2){Ph(2)PCH(2)ox(Me2)}] (Ph(2)PCH(2)ox(Me2) = 2-[(diphenylphosphanyl)-methyl]-4,4-dimethyl-4,5-dihydro-oxazole) () and the phosphinito-oxazoline complexes [CoCl(2){Ph(2)POCH(2)ox(Me2)}] (Ph(2)POCH(2)ox(Me2) = 1-[4,4-dimethyl-2{1-oxy(diphenylphosphino)-1-methyl}]-4,5-dihydro-oxazole) () and [CoCl(2){Ph(2)POCMe(2)ox(Me2)}] (Ph(2)POCMe(2)ox(Me2) = 1-[4,4-dimethyl-2- [1-oxy(diphenylphosphino)-1-methylethyl]]-4,5-dihydrooxazole) () are mononuclear, the phosphino-oxazoline complexes [CoCl(2){micro-i-Pr(2)PCH(2)ox}](2) (i-Pr(2)PCH(2)ox = 2-[(diisopropyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) () and [CoCl(2){micro-Ph(2)PCH(2)ox}](2) (Ph(2)PCH(2)ox = 2-[(diphenyl-phosphanyl)-methyl]-4,5-dihydro-oxazole) () are dinuclear compounds and contain two bridging phosphino-oxazoline ligands which form a 10-membered ring. In the course of this work, the zwitterionic complex [CoCl(3){Ph(2)PCH(2)C(O)OCH(2)CMe(2)NH(3)] () was obtained and characterised by X-ray diffraction in which the oxazoline ring has been opened. Air-oxidation of the phosphine function of the mononuclear P,N chelate complex yielded the blue N,O-bridged, centrosymmetric dinuclear complex [[upper bond 1 start]CoCl(2){micro-OPPh(2)CH(2)[lower bond 1 start]C[double bond, length as m-dash]N[upper bond 1 end]CMe(2)CH(2)O[lower bond 1 end]}](2) () which contains a 12-membered ring. All these complexes are paramagnetic and their magnetic moments in solution were measured by the Evans method. Complexes were evaluated in the catalytic oligomerisation of ethylene with AlEtCl(2) or methylaluminoxane (MAO) as cocatalysts and provided moderate activities. In the presence of AlEtCl(2) (6-14 equiv.), the selectivities for ethylene dimers were higher than 92% and complex showed the highest turnover frequency with 14 equiv. of AlEtCl(2). When MAO was used as cocatalyst, the catalytic activities were similar to those with AlEtCl(2) but significant amounts of C(6)-C(12) oligomers were produced.

Three new palladium complexes containing a difunctional P,N-chelate, namely tris(chloro{[1-methyl-1-(6-methyl-2-pyridyl)ethoxy]diphenylphospine-kappa(2)N,P}methylpalladium(II)chloroform solvate, 3[Pd(CH(3))Cl(C(21)H(22)NOP)].CHCl(3), (III), dichloro[2-(2,6-dimethylphenyl)-6-(diphenylphosphinomethyl)pyridine-kappa(2)N,P]palladium(II), [PdCl(2)(C(26)H(24)NP)], (IV), and chloro[2-(2,6-dimethylphenyl)-6-(diphenylphosphinomethyl)pyridine-kappa(2)N,P]methylpalladium(II), [Pd(CH(3))Cl(C(26)H(24)NP)], (V), are reported. Geometric data and the conformations of the ligands around the metal centers, as well as slight distortions of the Pd coordination environments from idealized square-planar geometry, are discussed and compared with the situations in related compounds. Non-conventional hydrogen-bond interactions (C-H...Cl) have been found in all three complexes. Compound (III) is the first six-membered chloro-methyl-phosphinite P,N-type Pd(II) complex to be structurally characterized.

Strontium hexamethyldisilazide, combined with a chiral bis(sulfonamide) ligand, was found to be very effective for the catalytic asymmetric Michael addition of malonate to chalcone derivatives.

A novel catalyst system based on a chiral strontium complex which promotes the catalytic asymmetric Michael addition reactions of malonates to enones has been developed. The conjugate addition reactions proceeded smoothly in the presence of 5 mol % of the chiral strontium catalyst, at room temperature, to afford the desired adducts in high yields and excellent enantioselectivities. This method provides an efficient approach to the preparation of building blocks possessing various functional groups and possible sites for further functionalization.

The phosphinito-oxazoline ligand 4,4-dimethyl-2-[methoxy(diphenylphosphine)]-4,5-dihydrooxazole (2a) and the phosphonite-oxazoline ligand 4,4-dimethyl-2-[methoxy(6H-dibenz[c,e][1,2]oxaphosphorin)]-4,5-dihydrooxazole (8a) were prepared by deprotonation of (4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol (1a) and reaction with the corresponding P-Cl function, similar to the ligands 2b (4,4-dimethyl-2-[1-oxy(diphenylphosphine)-1-methylethyl]-4,5-dihydrooxazole) and 8b (4,4-dimethyl-2-[1-oxy(6H-dibenz[c,e][1,2]oxaphosphorin)-1-methylethyl]-4,5-dihydrooxazole) reported previously. These ligands react with [PdClX(COD)] to give complexes of the type [PdClX(P,N)] (3a P,N = 2a, X = Cl; 4a P,N = 2a, X = Me; 4b P,N = 2b , X = Me; 9a P,N = 8a, X = Cl; 9b P,N = 8b, X = Cl; 10a P,N = 8a, X = Me; 10b P,N = 8b, X = Me). Complexes 4a,b and 10a,b reacted with AgCF(3)SO(3) to yield [PdMe(P,N)OSO(2)CF(3)] 5a,b and 11a,b, respectively. From the stepwise insertion reaction of CO and ethylene into the Pd-C bond of 5a and 11a,b, the alkyl ketone chelate complexes [Pd{CH(2)CH(2)C(O)Me}(P,N)]CF(3)SO(3) 7a and 14a,b respectively, have been isolated and spectroscopically characterized. Complexes 3a.CH(2)Cl(2), 5a, 9b, 10a,b, [PdMe(H(2)O)(P,N)]CF(3)SO(3) 12b, (P,N = 8b) and 14a,b have also been characterized by X-ray crystallography and the structures of 14a,b represent still rare examples of structurally characterized CO/ethylene coupling products.