Eduardo Gayoso

Cyclometallation&—III. Regioselectivity in Pd(II) Cyclometallated complexes

Abstract Cyclometallated complexes derived from organic ligands where two initial metallation sites are present have been synthesized. The preferred palladation position is discussed on the basis of electronic and steric effects, and the regioselectivity of the cyclometallation is characterized by means of IR and 1 H NMR spectroscopy. The spectral studies show that the less favored position is not attached to the metal atom. Acetato- and halogeno-bridged dimers, as well as phosphine monomers derived from the latter, have been obtained and studied by spectroscopical methods.

Cyclometallation, part II. I.r. and1H N.m.r. studies of palladium(II) compounds with substitutedN-(benzylidene)amines

SummaryNew cyclometallated complexes of palladium containing substitutedN-(benzylidene)amines have been prepared and characterized. Palladium(II) acetate is used to make the acetato-bridged dimers, which undergo metathetical reactions to give the halo-bridged dimers. These when treated with PPh3 or P(C6H11)3 in a 1∶2 molar ratio yield the phosphine monomers. I.r. and1H n.m.r. studies show that palladium is coordinated through nitrogen, and also reveal the disposition of the halogen and phosphine ligands in the monomeric complexes.

Cyclometallated compounds of manganese(I) with 1-methylphenylimidazoles

Cyclometallated complexes of magnanese(I) with 1-methylphenylimidazoles have been prepared. IR and 1H NMR spectroscopic studies show they are octahedral complexes in which the imidazole ligand is bound to the metal through the nitrogen and phenyl C(6) atoms. When the imidazole ligand with two phenyl groups at the C(2′) and C(4′) atoms is used, both possible cyclometallated compounds are obtained.

Synthesis of cyclometallated compounds of N-(3-methoxy)benzylidenecyclohexylamine. Crystal structure of the novel cyclometallated bipalladium(II) complex [(mbcy-C6,N)Pd{μ-Ph2PC(CH2)PPh2}(μ-Cl)Pd(mbcy-C6,N)]Cl·4CHCl3

Abstract The reaction of palladium(II) acctate with N -(3-methoxy)benzylidenecyclohexylamine (Hmbcy) in glacial acetic acid yields the acetato-bridged complex 1 . From this the halide-bridged dimers 2 and 3 are synthesized. Treatment of 2 and 3 with bis(diphenylphosphino)methane (dppm) or 1,1-bis (diphenylphosphino)ethene (vdpp) in a 1:1 molar ratio gives the dinuclear specics 4 , 5 and 8 with the two palladium atoms bridged by a diphosphine and a halogen atom. Conductivity measurements show that they are 1:1 electrolytes. Treatment of 2 and 3 with dppm or vdpp and NaClO 4 or NH 4 PF 6 yields the mononuclear species 6 , 7 and 9 with the diphosphine as a chelating ligand. These complexex are also 1:1 electrolytes. The complexes have been characterized by IR, 31 P{ 1 H} and 1 H NMR spectroscopies. The crystal structure of the novel bipalladium(II) complex 8 has been determined: P 2 1 / n ; a =1166.7(3), b =2314.2(4), c =2603.3(5) pm, β=100.76(4)° and Z =4.

Novel cyclopalladated ferrocenyl Schiff base compounds with bridging and chelating diphosphines. Crystal and molecular structure of [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)N-2,4,6-Me3C6H2]}{Ph2P(CH2)nPPh2P,P}][PF6] (n=1, 2)

Abstract The reaction of the ferrocenylimine (η5-C5H5)Fe(η5-C5H4)C(H)NR (R=2,4,6-Me3C6H2) (a), with Pd(AcO)2 or with Li2[PdCl4] leads to the heterotetrametallic compounds [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)NR}(μ-O2CMe)]2 (1) and [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)NR}(μ-Cl)]2 (2), respectively. Compound 2 may also be obtained by treatment of 1 with aqueous sodium chloride. Compound 2 reacts with tertiary diphosphines in 1:1 or 1:2 molar ratio to give [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)NR]Cl}2{μ-Ph2P(CH2)nPPh2}] (n=1, 3; n=2, 4; n=3, 5; n=4, 6), [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)NR]Cl}2(μ-Ph2PC5H4FeC5H4PPh2)] (7), and [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)NR}{Ph2P(CH2)nPPh2P,P}][PF6] (n=1, 8; n=2, 9; n=3, 10; n=4, 11), [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)NR}(Ph2PC5H4FeC5H4PPh2P,P)][PF6] (12), respectively. The crystal structures of compounds 8 and 9 have been determined by X-ray crystallography.

Preparation and Characterization of Pd(II) Dimer and Monomer Complexes with N-Donor Ligands

Abstract The reaction of palladium acetate with Schiff base ligands in glacial acetic acid yields acetato-bridged complexes. From them halogeno-bridged dimers are obtained, which in turn give way to cyclometallated and non-cyclometallated monomers upon reaction of the former with triphenylphosphine in a 1:2 or 1:4 molar ratio, respectively. By IR, 31P-{1H} and 1H spectroscopic studies the preferred palladation site is determined as well as the position of the phosphine and halogen ligands in the monomer species. Conductivity measurements have been carried out with the two phosphine monomers to determine their non-electrolyte nature.

Cyclometallated Compounds of Pd(II) with Benzalazines

Abstract The synthesis of acetato and chloro bridged polymer cyclometallated compounds of Pd(II) with azines derived from 3, 4-dimethoxybenzaldehyde and 3, 4-methylenedioxobenzaldehyde is described. From the chloro bridged complexes the cyclometallated and non-cyclometallated monomers have been obtained by reaction of the former with triphenylphosphine. All the compounds have been fully characterized by elemental analyses as well as i. r. and 1H n.m.r. spectroscopy.

Cyclometallation, Palladium(II) Complexes with Schiff Base Ligands

Abstract A number of new cyclometallated complexes of palladium with Schiff bases have been synthesized and characterized. These ligands with palladium(II) acetate gave the acetato-bridged dimers. These were converted to the corresponding halooeno-bridged dimers by reaction with sodium chloride or sodium bromide. Reaction of the latter complexes with P(C6H5)3 in a 1:2 molar ratio afforded the cyclometal lated phosphine monomers. All the compounds prepared in this study are characterized by means of IR and 1H NMD spectroscopy.

Cyclometallated Compounds of Pd(II) with 1-Methylphenylimidazoles

Abstract The reaction of palladium(II) acetate or potassium tetrachloropalladate(II) with 1-methyl-4-phenylimidazole, 1-methyl-2,4-diphenylimidazole, 1-methyl-2,5-diphenylimidazole, 1-methyl-4,5-diphenylimidazole and 1-methyl-2,4,5-triphenylimidazole, whose derivatives are named a, b, c, d and e, respectively, gives cyclometallated acetato (1) and chloro (2) bridged dimeric complexes, which can be interconverted. By convenient metathesis reactions (1) and (2) give the bromo bridged dimeric complex (3). Complexes (2) and (3) react with excess triphenylphosphine to give the cyclometallated monomers (4) and (5) of formula LPd(X)PPh3 [(4), X = Cl; (5), X = Br; L = phenylimidazole-N,C]. Treatment of (2) with Tl(acac) yields monomeric products (6) of formula LPd(acac-O,O). The products obtained have been characterized by elemental analysis (C,H,N) and by IR and 1H NMR spectroscopies.

Synthesis and Structure of Di-[µ-acetato(O,O′)-ferrocenylmethyliden-2,4,6-trimethylaniline(N,C)-palladium(II)]

Reaction of Na2PdCl4 with N-ferrocenylmethylidene-2,4,6-trimethylaniline yields the dimeric, chloro-bridged Pd(II) complex [Pd{(C5H5)FeC5H3C(H)=N-2,4,6-(CH3)3C6H2}Cl]2. The title complex (1) is obtained by substitution of the chloro-bridges with acetate. 1 crystallizes in the orthorhombic space group Pbca with the lattice parameters a = 1346.4(4), b = 2876.6(2), c = 2472.8(5) pm and Z = 8. In the dimeric complex each Pd2+ cation exhibits a square-planar coordination by the N atom and an ortho-C atom of the cyclopentadienyl ring of the Schiffbase and two oxygen atoms of two different bridging acetato groups.