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Biomedical subjects

Michael C Jennings

Publications and source records attributed to Michael C Jennings.

29 records · Page 2Linked to original sources
PubMed2003

Oxidative addition of Ph2TeCl2 to a dimethylplatinum(II) complex: effects of secondary bonding in the platinum-tellurium products.

In the first example of oxidative addition of tellurium-halide bonds to a transition-metal complex, Ph(2)TeCl(2) reacts with [PtMe(2)(bu(2)bpy)], 1, bu(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, to give an organoplatinum(IV) complex that can be formulated as an ionic diphenyl telluride complex [PtClMe(2)(TePh(2))(bu(2)bpy)]Cl or as a neutral chlorodiphenyltelluryl complex [PtClMe(2)(TePh(2)Cl)(bu(2)bpy)]; the complex contains an unusually long Te...Cl bond length of 3.43 A. The weakly bound chloride ligand is easily removed by reaction with AgO(3)SCF(3) to give the cationic complex [PtClMe(2)(TePh(2))(bu(2)bpy)](CF(3)SO(3)) in which the triflate anion is not coordinated to tellurium. This complex reacts with a second 1 equiv of AgO(3)SCF(3) to give the aqua complex [PtMe(2)(OH(2))(TePh(2)..O(3)SCF(3))(bu(2)bpy)](CF(3)SO(3)), in which a triflate anion forms secondary bonds with both the aqua and TePh(2) ligands. In these platinum(IV) complexes, the magnitude of the coupling constant (1)J(PtTe) is strongly influenced by the presence of the weakly bonded Te...X groups.

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PubMed2003

Self-assembly in palladium(II) and platinum(II) chemistry: the biomimetic approach.

The self-assembly of complex cationic structures by combination of cis-blocked square planar palladium(II) or platinum(II) units with bis(pyridyl) ligands having bridging amide units has been investigated. The reactions have yielded dimers, molecular triangles, and polymers depending primarily on the geometry of the bis(pyridyl) ligand. In many cases, the molecular units are further organized in the solid state through hydrogen bonding between amide units or between amide units and anions. The molecular triangle [Pt(3)(bu(2)bipy)(3)(mu-1)(3)](6+), M = Pd or Pt, bu(2)bipy = 4,4'-di-tert-butyl-2,2'-bipyridine, and 1 = N-(4-pyridinyl)isonicotinamide, stacks to give dimers by intertriangle NH.OC hydrogen bonding. The binuclear ring complexes [[Pd(LL)(mu-2)](2)](CF(3)SO(3))(4), LL = dppm = Ph(2)PCH(2)PPh(2) or dppp = Ph(2)P(CH(2))(3)PPh(2) and 2 = NC(5)H(4)-3-CH(2)NHCOCONHCH(2)-3-C(5)H(4)N, form transannular hydrogen bonds between the bridging ligands. The complexes [[Pd(LL)(mu-3)](2)](CF(3)SO(3))(4), LL = dppm or dppp, L = PPh(3), and 3 = N,N'-bis(pyridin-3-yl)-pyridine-2,6-dicarboxamide, and [[Pd(LL)(mu-4)](2)](CF(3)SO(3))(4), LL = dppm, dppp, or bu(2)bipy, L = PPh(3), and 4 = N,N'-bis(pyridin-4-yl)-pyridine-2,6-dicarboxamide, are suggested to exist as U-shaped or square dimers, respectively. The ligands N,N'-bis(pyridin-3-yl)isophthalamide, 5, or N,N'-bis(pyridin-4-yl)isophthalamide, 6, give the complexes [[Pd(LL)(mu-5)](2)](CF(3)SO(3))(4) or [[Pd(LL)(mu-6)](2)](CF(3)SO(3))(4), but when LL = dppm or dppp, the zigzag polymers [[Pd(LL)(mu-6)](x)](CF(3)SO(3))(2)(x) are formed. When LL = dppp, a structure determination shows formation of a laminated sheet structure by hydrogen bonding between amide NH groups and triflate anions of the type NH-OSO-HN.

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PubMed2002

Self-assembly of polymer and sheet structures in palladium(II) complexes containing carboxylic acid substituents.

A series of complexes trans-[PdCl(2)L(2)] has been prepared by the reaction of [PdCl(2)(PhCN)(2)] and/or Na(2)[PdCl(4)] with L = pyridine or quinoline ligands having one or two carboxylic acid groups. These complexes can form 1-D polymers through O-H.O hydrogen bonding between the carboxylic acid groups, as demonstrated by structure determinations of [PdCl(2)(NC(5)H(4)-4-COOH)(2)], [PdCl(2)(NC(5)H(4)-3-COOH)(2)], and [PdCl(2)(2-Ph-NC(9)H(5)-4-COOH)(2)]. In some cases, solvation breaks down the O-H.O hydrogen-bonded structures, as in the structures of [PdCl(2)(NC(5)H(4)-3-COOH)(2)].2DMSO and [PdCl(2)(2-Ph-NC(9)H(5)-4-COOH)(2)].4DMF, while pyridine-2-carboxylic acid underwent deprotonation to give the chelate complex [Pd(NC(5)H(4)-2-C(O)O)(2)]. The complexes trans-[PdCl(2)L(2)], L = pyridine-3,5-dicarboxylic acid or 2,6-dimethyl pyridine-3,5-dicarboxylic acid, self-assembled to give 2-D sheet structures, with hydrogen bonding between the carboxylic acid groups mediated by solvate methanol or water molecules. In the cationic complexes [PdL'(2)L(2)](2+) (L'(2) = Ph(2)PCH(2)PPh(2), Ph(2)P(CH(2))(3)PPh(2); L = pyridine carboxylic acid; anions X(-) = CF(3)SO(3)(-)), hydrogen bonding between the carboxylic acid groups and anions or solvate acetone molecules occurred, and only in one case was a polymeric complex formed by self-assembly.

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PubMed2002

Coordination polymers of gold(I) with dithiolate and diphosphine ligands.

The first neutral, hybrid organic-inorganic coordination polymers with linear gold(I) centres in the backbone have the formula [X(OCH2CH2O2CCH2SAu)2(mu-dppee)]n, X = 1,4-C6H4 or C10H6, dppee = trans-bis(diphenylphospino)ethylene, are easily formed by self-assembly during crystallization from macrocyclic isomers (n = 1), and form sheet structures anchored by secondary Au...S and S...S interactions in the solid state.

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PubMed2002

Supramolecular gold(I) thiobarbiturate chemistry: combining aurophilicity and hydrogen bonding to make polymers, sheets, and networks.

The cooperative forces of aurophilic and hydrogen bonding have been used in the self-assembly of phosphine or diphosphine complexes of gold(I) with the thiolate ligands derived from 2-thiobarbituric acid, SC(4)H(4)N(2)O(2), by single or double deprotonation. The reaction of the corresponding gold(I) trifluoroacetate complex with SC(4)H(4)N(2)O(2) gave the complexes [Au(SC(4)H(3)N(2)O(2))(PPh(3))], 1, [(AuSC(4)H(3)N(2)O(2))(2)(micro-LL)], with LL = Ph(2)PCH(2)PPh(2), 2a, Ph(2)P(CH(2))(3)PPh(2), 2b, or Ph(2)PCH=CHPPh(2), 2c, or the cyclic complex [Au(2)(micro-SC(4)H(2)N(2)O(2))(micro-Ph(2)PCH(2)CH(2)PPh(2))], 3. In the case with LL = Ph(2)P(CH(2))(6)PPh(2), the reaction led to loss of the diphosphine ligand to give [Au(6)(SC(4)H(3)N(2)O(2))(6)], 4, a hexagold(I) cluster complex in which each gold(I) center has trigonal AuS(2)N coordination. Structure determinations show that 1 has no aurophilic bonding, 2b, 3, and 4 have intramolecular aurophilic bonding, and 2c has intermolecular aurophilic bonding that contributes to the supramolecular structure. All the complexes undergo supramolecular association through strong NH...O and/or OH...N hydrogen bonding, and complex 3 also takes part in CH...O hydrogen bonding. The supramolecular association leads to formation of interesting polymer, sheet, or network structures, and 4 has a highly porous and stable lattice structure.

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PubMed2002

Molecular triangle of palladium(II) and its anion binding properties.

The ligand 4(3H)-pyrimidone (Hpm) forms the complexes trans-[PdCl(2)(Hpm)(2)] and [Pd(PP)(Hpm)(2)](CF(3)SO(3))(2) (PP = Ph(2)PCH(2)PPh(2) or Ph(2)P(CH(2))(3)PPh(2)), with the neutral ligand (Hpm), and a bowl-like molecular triangle, [(Pd(bu(2)bipy)(mu-pm))(3)](3+) (bu(2)bipy = 4,4'-di-tert-butyl-2,2'-bipyridine), with the deprotonated ligand (pm). This triangular complex acts as a host for binding of several anionic guests.

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PubMed2002

Gold(I) macrocycles and topologically chiral [2]catenanes.

The design and synthesis of a new type of topologically chiral [2]catenane is reported. The compounds are formed easily by self-assembly on reaction of the oligomeric digold(I) diacetylide precursor complex [[4-BrC(6)H(4)CH(4-C(6)H(4)OCH(2)CCAu)(2)](n)] with diphosphine ligands. Reactions with the diphosphines PP = bis(diphenylphosphinophoshino)acetylene, trans-1,2-bis(diphenylphosphino)ethylene, bis(diphenylphosphino)ethane, and 1,1'-bis(diphenylphosphino)ferrocene yield simple ring complexes [4-BrC(6)H(4)CH(4-C(6)H(4)OCH(2)CCAu)(2)(mu-PP)] as the only products, since the spacer groups in the diphosphines are not long enough or are too bulky to allow catenane formation. Reaction with PP = bis(diphenylphosphino)propane or bis(diphenylphosphino)butane gave [2]catenane complexes [[4-BrC(6)H(4)CH(4-C(6)H(4)OCH(2)CCAu)(2)(mu-PP)](2)], whose structures are confirmed crystallographically. The macrocyclic ring compounds have C(s) symmetry but, as a result of the presence of the unsymmetrical "hinge group" 4-BrC(6)H(4)CH, the [2]catenanes have C(2) symmetry and so are topologically chiral. In favorable cases, the formation of the [2]catenane can be proved by NMR spectroscopy since catenane formation leads to nonequivalence of most ring atoms. The formation of the [2]catenanes was successfully predicted based on the conformation of the precursor bis(phenol), and it is argued that the methods used should be more generally applicable to the synthesis of functionally substituted supermolecules of interest for application in molecular devices.

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PubMed2002

Self-assembly of gold(I) rings and reversible formation of organometallic [2]catenanes.

The reaction of the digold(I) diacetylide [(AuCCCH2OC6H4)2CMe2] with diphosphane ligands can lead to formation of either macrocyclic ring complexes or [2]catenanes by self-assembly. This gives an easy route to rare organometallic [2]catenanes, and the effect of the diphosphane ligand on the selectivity of self-assembly is studied. With diphosphane ligands Ph2P(CH2)xPPh2, the simple ring complex [Au2[(CCCH2OC6H4)2CMe2](Ph2P(CH2)xPPh2)] is formed selectively when x = 2, but the [2]catenanes [Au2[(CCCH2OC6H4)2CMe2](Ph2P(CH2)xPPh2)]2 are formed when x = 4 or 5. When x = 3, a mixture of the simple ring and [2]catenane is formed, along with the "double-ring" complex, [Au4[(CCCH2OC6H4)2CMe2]2(Ph2P(CH2)3PPh2)2] and a "hexamer" Au2[(CCCH2OC6H4)2CMe2](Ph2P(CH2)3PPh2)]6] whose structure is not determined. A study of the equilibria between these complexes by solution NMR techniques gives insight into the energetics and mechanism of [2]catenane formation. When the oligomer [(AuCCCH2OC6H4)2CMe2] was treated with a mixture of two diphosphane ligands, or when two [2]catenane complexes [[Au2[(CCCH2OC6H4)2CMe2](diphosphane)]2] were allowed to equilibrate, only the symmetrical [2]catenanes were formed. The diphosphanes Ph2PCCPPh2, trans-[Ph2PCH=CHPPh2] and (Ph2PC5H4)2Fe give the corresponding ring complexes [Au2[(CCCH2OC6H4)2CMe2](diphosphane)], and the chiral, unsymmetrical diacetylide [Au2[(CCCH2OC6H4C(Me)(CH2CMe2)C6H3OCH2CC)] gives macrocyclic ring complexes with all diphosphane ligands Ph2P(CH2)xPPh2 (x = 2-5).

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PubMed2002

Alternating right- and left-handed helical loops in a self-assembled polymer: direct observation of ring-opening polymerization of a macrocyclic gold complex.

Reaction of the ligand NN'-bis(pyridin-3-yl)-1,3-benzenedicarboxamide (1) with the diphosphanedigold(I) complex [(mu-PP)(AuO2CCF3)2] occurred by displacement of the trifluoroacetate ligands by the pyridyl groups of 1, and crystallization gave the macrocyclic complex [Au2(mu-PP)(mu-1)](CF3CO2)2 (2b), when PP = trans-[Ph2PCH=CHPPh2] but the polymer [(Au2(mu-PP)(mu-1)]x](CF3CO2)2x (3), when PP= Ph2PCH2CH2PPh2. The polymer 3 contains a series of helical turns connected by linear chain sections. and the helices have alternating right- and left-handed conformations. The polymer 3 dissolves to give an equilibrium mixture of the macrocyclic ring complex [Au2(mu-PP)(mu-1)](CF3CO2)2 (2a), and ring-opened oligomers, thus giving insight into the mechanism of the ring-opening polymerization reaction.

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