Biomedical subjects

Pablo Espinet

Publications and source records attributed to Pablo Espinet.

21 records · Page 2Linked to original sources

PubMed1997

Liquid-Crystalline Mono- and Dinuclear (Perhalophenyl)gold(I) Isocyanide Complexes.

Rodlike gold(I) and gold(III) complexes [AuR(C&tbd1;N(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)-p)] (m = 1, n = 10, R = C(6)F(5); m = 2, n = 4, 6, 8, 10, 12, R = C(6)F(5), C(6)F(4)Br-o, C(6)F(4)Br-p), [(&mgr;-4,4'-C(6)F(4)C(6)F(4)){AuC&tbd1;N(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] (m = 1, 2; n = 4, 6, 8, 10, 12), [AuRI(2)(C&tbd1;NC(6)H(4)C(6)H(4)OC(n)()H(2)(n)()(+1)-p)] (R = C(6)F(5), n = 8; R = C(6)F(4)Br-o, n = 10), and [(&mgr;-4,4'-C(6)F(4)C(6)F(4)){AuX(2)C&tbd1;N(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] (m = 1, 2; n = 4, 6, 8, 10, 12) have been prepared and their liquid crystal behavior has been studied. The gold(III) compounds are not mesomorphic, but all the perhalo-gold(I) derivatives described are liquid crystals except the phenyl isocyanide gold(I) derivative [Au(C(6)F(5))(C&tbd1;NC(6)H(4)OC(10)H(21)-p)]. The mononuclear derivatives show only a nematic (N) phase when the isocyanides have a short tail (n = 4), N and smectic A phases (S(A)) when the isocyanides have an intermediate tail (n = 6, 8), and only S(A) phases for longer chains. Their thermal stability is high, even in the isotropic state. The variation in transition temperatures is as follows: C(6)F(4)Br-p >/= C(6)F(5) > C(6)F(4)Br-o when n </= 6 and C(6)F(4)Br-p > C(6)F(4)Br-o > C(6)F(5) for n >/= 8. This behavior is understood on the basis of electronic and steric factors. The dinuclear compounds [(&mgr;-4,4'-C(6)F(4)C(6)F(4)){AuC&tbd1;N(C(6)H(4))(m)()OC(n)()H(2)(n)()(+1)}(2)] display only N mesophases and all the biphenylisocyanide derivatives and phenyl isocyanide compounds with n </= 6 undergo some decomposition upon reaching the clearing point to the isotropic state.

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PubMed1996

Palladium Complexes with the Tridentate Dianionic Ligand Pyridine-2,6-dicarboxylate, dipic. Crystal Structure of [Pd(dipic)(PBu(3))](2).

The reactions of [Pd(acac)(2)] or [Pd(OAc)(2)](3) with pyridine-2,6-dicarboxylic acid (H(2)dipic) in acetonitrile afford [Pd(dipic)(NCMe)] in high yield. This complex has been used as starting material in the preparation of a variety of neutral an anionic complexes. The dipicolinate anion behaves as a tridentate ligand in all cases, but two modes of coordination are found, depending on the ligand: as a pincer ligand O,N,O-bonded to the same palladium, giving mononuclear complexes, and as an O,N-chelate N,O'-bridging ligand in dinuclear complexes. An X-ray determination of the structure of a dimer, [Pd(dipic)(PBu(3))](2) (monoclinic, space group P2(1)/n, a = 18.144(4) Å, b = 13.191(2) Å, c = 19.571(3) Å, beta = 113.45(2) degrees, Z = 4, R = 0.050, R(w) = 0.054) shows that the ligand is coordinated to one palladium in a eta(2)-N,O chelate fashion and one oxygen atom of the other carboxylate group makes a bridge to the other palladium atom, in a novel bonding mode for the dipic ligand.

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PubMed1996

Oxidative Addition of Group 14 Element Hydrido Compounds to OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2): Synthesis and Characterization of the First Trihydrido-Silyl, Trihydrido-Germyl, and Trihydrido-Stannyl Derivatives of Osmium(IV).

The dihydrido-olefin complex OsH(2)(eta(2)-CH(2)=CHEt)(CO)(P(i)Pr(3))(2) (2) reacts with H(2)SiPh(2) to give OsH(3)(SiHPh(2))(CO)(P(i)Pr(3))(2) (3). The molecular structure of 3 has been determined by X-ray diffraction (monoclinic, space group P2(1)/c with a = 16.375(2) Å, b = 11.670(1) Å, c =18.806(2) Å, beta = 107.67(1) degrees, and Z = 4) together with ab initio calculations on the model compound OsH(3)(SiH(3))(CO)(PH(3))(2). The coordination geometry around the osmium center can be rationalized as a heavily distorted pentagonal bipyramid with one hydrido ligand and the carbonyl group in the axial positions. The two other hydrido ligands lie in the equatorial plane, one between the phosphine ligands and the other between the SiHPh(2) group and one of the phosphine ligands. Complex 3 can also be prepared by reaction of OsH(eta(2)-H(2)BH(2))(CO)(P(i)Pr(3))(2) (4) with H(2)SiPh(2). Similarly, the treatment of 4 with HSiPh(3) affords OsH(3)(SiPh(3))(CO)(P(i)Pr(3))(2) (5), while the addition of H(3)SiPh to 4 in methanol yields OsH(3){Si(OMe)(2)Ph}(CO)(P(i)Pr(3))(2) (6). Complex 2 also reacts with HGeR(3) and HSnR(3) to give OsH(3)(GeR(3))(CO)(P(i)Pr(3))(2) (GeR(3) = GeHPh(2) (7), GePh(3) (8), GeEt(3) (9)) and OsH(3)(SnR(3))(CO)(P(i)Pr(3))(2) (R = Ph (10), (n)Bu (11)), respectively. In solution, compounds 3 and 5-11 are fluxional and display similar (1)H and (31)P{(1)H} NMR spectra, suggesting that they possess a similar arrangement of ligands around the osmium atom.

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