Denticity

Abstract: Two families of molecular frameworks which grow as homochiral single crystals are described. Both consist of multiple interpenetration of the three-connected chiral (10,3)-a (Y*) network and result from the tridentate coordination of the 1,3,5-benzenetricarboxylate (btc) ligand to octahedral metal centers which act as linear connectors. The nature of the interpenetration is controlled by the auxiliary ligands bound in the equatorial plane of the metal center. Ethylene glycol (eg) binds in a unidentate fashion to form phase A which has 28% accessible solvent volume and contains four interpenetrating (10,3)-a networks. 1,2-Propanediol (1,2-pd) coordinates as a bidentate ligand to yield a phase B with a greatly enhanced 51% of solvent accessible volume, because only two (distorted) (10,3)-a‘ networks interpenetrate. Ligands in the void space and bound to the metal center can both be liberated thermally: the kinetics of this process allow isolation of microporous desolvated crystalline A and B. The porous ph...

Abstract: A wide variety of Platinum(II) complexes have been investigated for antitumor activity against Sarcoma 180 in Swiss white female mice. In general, only neutral complexes exhibit activity while charged species are inactive and relatively nontoxic. A series of complexes of the type cis -[PtA 2 X 2 ] (where A 2 is either two monodentate or one bidentate amine ligand and X 2 is either two monodentate or one bidentate anionic ligand) have been studied with A and X being systematically varied. This has resulted in the identification of at least ten potentially active antitumor drugs. Trans isomers are inactive in comparison with active cis complexes and the presence of cis -reactive ligands appears to be a necessary parameter for antitumor activity. Complexes with highly reactive ligands such as cis -[Pt(NH 3 ) 2 (H 3 O) 2 ] (NO 3 ) 2 are highly toxic. Palladium(II) complexes, which are analogs of the active Platinum(II) compounds, have been found to be inactive.

Abstract: Two ligands have been synthesized by derivatisation of cyanuric chloride: 6-(diethylamino)-2,4-disulfanyl-1,3,5-triazine (H2SSta) 1 and 6-(diethylamino)-2-hydroxo-4-sulfanyl-1,3,5-triazine (H2OSta) 2 have been characterised by X-ray crystallography, which shows intermolecular hydrogen bonding in the solid state, leading to dimers of 1 and ribbons of 2. On reaction with metal salts both ligands undergo oligomerisation reactions. Compound 1 reacts with nickel chloride to form a mononuclear complex, [Ni{(Sta)S(S2ta)}] 3. In 3 two triazine ligands have reacted, to form a tetradentate ligand in which two triazine rings are bridged by a sulfur group, with a co-ordinated disulfide group present on one ring and a co-ordinated thiolate on the second. Compound 2 reacts with cobalt(II) chloride to form a cage complex, [Co6NaO(OStaH)7{S(Ota)2}2(O2CPh)2(H2O)2] 4. This complicated structure contains two polydentate ligands formed by linking triazine groups through a bridging sulfur. The cage contains four cobalt(II) and two cobalt(III) sites which are assigned by bond length considerations. The compound [Co(OSta)3] 5 co-crystallises with 4, and its structure has also been determined.

Abstract: PdII complexes of donor-functionalized heterocyclic carbene ligands have been synthesized through a route involving carbene transfer from AgI carbene precursors. The Ag complexes undergo facile reaction with PdCl2(MeCN)2 to yield Pd(C∧OPh)2Cl2 (3a), Pd(C∧OOMe)2Cl2 (3b), and Pd(C∧N)2Cl2 (3c) (C∧OPh = 3-methyl-1-phenacylimidazolin-2-ylidene, C∧OOMe = 3-methyl-1-(methylacetyl)imidazolin-2-ylidene, C∧N = 3-methyl-1-picolylimidazolin-2-ylidene), from which [Pd(C∧OOMe)2(MeCN)2][BF4]2 (4b) and [Pd(C∧N)2][BF4]2 (4c) can be prepared by halide abstraction. When PdMeCl(cod) (cod = cyclooctadiene) is treated with the Ag complexes 2b and 2c, the Me−Pd carbene complexes [PdMe(C∧OOMe)Cl]2 (5b), PdMe(C∧N)Cl (5c), PdMe(C∧OOMe)2Cl (6b), and PdMe(C∧N)2Cl (6c) are obtained. The C∧OPh and C∧OOMe ligands are monodentate with a dangling functional moiety in all complexes, while the C∧N ligand exhibits both monodentate and chelating behavior. Several complexes give rise to highly active and very stable catalysts for Heck, Suzuki...

Abstract: Equilibrium constants in Cu-based atom transfer radical polymerization (ATRP) were determined for a wide range of ligands and initiators in acetonitrile at 22 °C. The ATRP equilibrium constants obtained vary over 7 orders of magnitude and strongly depend on the ligand and initiator structures. The activities of the CuI/ligand complexes are highest for tetradentate ligands, lower for tridentate ligands, and lowest for bidentate ligands. Complexes with tripodal and bridged ligands (Me6TREN and bridged cyclam) tend to be more active than those with the corresponding linear ligands. The equilibrium constants are largest for tertiary alkyl halides and smallest for primary alkyl halides. The activities of alkyl bromides are several times larger than those of the analogous alkyl chlorides. The equilibrium constants are largest for the nitrile derivatives, followed by those for the benzyl derivatives and the corresponding esters. Other equilibrium constants that are not readily measurable were extrapolated from t...