Clifton E. F. Rickard

Synthesis and Structural Analysis of a Helical Coordination Polymer Formed by the Self-Assembly of a 2,2′-Bipyridine-Based exo-Ditopic Macrocyclic Ligand and Silver Cations

The overall topology of coordination polymers can be controlled by means of the coordination preferences of the metal center and the structure of the bridging ligand. This is demonstrated here by the synthesis of a single-stranded helical coordination polymer by the self-assembly of the exo-ditopic ligand 1 and silver ions.

132,173-cyclopheophorbide enol, the first porphyrin isolated from a sponge

Abstract 132,173-Cyclopheophorbide enol (1) a non-metalated chlorophyll A derivative has been isolated from Darwinella oxeata (Bergquist) and its structure determined by physical and X-ray measurements.

Designing ligands to achieve robust oxidation catalysts. Iron based systems

Abstract Nitrile solvents containing α-CH substituents are catalytically oxidized by the tetraamido-N-FeIII-aqua complex, 3, with t-butyl hydroperoxide. Every observable product resulting from 3 has been characterized. An FeIV–cyano complex, 5, is the major inorganic product; the cyano ligand emanates from the solvent–substrate. A new type of ligand oxidative degradation giving 6 proceeds to ca. 10% of the iron macrocycle; its characterization indicates how the already robust macrocycle should be redesigned to further improve its oxidative stability. Such improvement has led to long-lived catalysts for hydrogen peroxide oxidation in water from neutral to basic pH at room temperature. Download : Download full-size image

Ruthenium-catalysed ortho vinylation of aromatic ketones with alkynes; unexpected cyclopentaannulation

Abstract Ruthenium-catalysed coupling of aromatic ketones with alkynylsilanes yielded in most cases ortho vinylation adducts in high yield. The predominant stereochemistry of the newly introduced double bond was E in all but a few cases. In contrast, 1-acetylnaphthalene underwent a one-pot insertion–cyclisation sequence yielding cyclopenta[ a ]naphthalene derivatives. A bis acetylene gave both mono and bis insertion products.

Reaction between the thiocarbonyl complex, Os(CS)(CO)(PPh3)3, and propyne: crystal structure of a new sulfur-substituted osmabenzene

Abstract Reaction between Os(CS)(CO)(PPh 3 ) 3 and propyne gives a complex mixture of products from which can be isolated the simple oxidative addition product Os(CCMe)H(CS)(CO)(PPh 3 ) 2 ( 1 ) and the osmabenzene Os(η 2 -C[S]CMeCHCHC Me)(CO)(PPh 3 ) 2 ( 2 ), where the two propyne molecules in the osmabenzene ring have linked tail-to-tail. Treatment of 1 with HCl gives, as the ultimate product, the propenylthioacyl complex, Os(η 2 -C[S]CHCHMe)Cl(CO)(PPh 3 ) 2 ( 3 ). The crystal structures of compounds 1 – 3 have been determined.

Design and synthesis of cobalt(III) nitrogen mustard complexes as hypoxia selective cytotoxins. The X-ray crystal structure of bis(3-chloropentane-2,4-dionato)(RS-N,N′-bis(2-chloroethyl)ethylenediamine)cobalt(III) perchlorate, [Co(Clacac)2(bce)]ClO4

The design, synthesis and biological evaluation of [Co(Meacac)2(dce)]+, a cobalt(III) nitrogen mustard complex that is effective as a hypoxia selective cytotoxin for potential anti-cancer use, is reported.

Platinum(II) complexes of chelating and monodentate thiourea monoanions incorporating chiral, fluorescent or chromophoric groups

Abstract The reaction of cis-[PtCl2(PPh3)2] with trisubstituted thioureas [R1R2NC(S)NHR3] in refluxing methanol with triethylamine base, followed by addition of NaBPh4 gives the salts [Pt{SC(NR1R2)NR3}(PPh3)2]BPh4 in high yield; a range of thiourea substituents, including chiral, fluorescent and chromophoric groups can be incorporated. The azo dye-derived complex [Pt{SC(N(CH2CH2)2O)NC6H4NNC6H4NMe2}(PPh3)2]BPh4 has been characterised by a single-crystal X-ray diffraction study. The formation of a fluorescein-derivatised platinum–thiourea complex is also described. Reaction of cis-[PtCl2(PPh3)2] with PhNHC(S)NHPh or EtNHC(S)NHEt, triethylamine and NaBPh4 gives, respectively, [Pt{SC(NHPh)NPh}(PPh3)2]+ and the known cation [Pt{SC(NHEt)NEt}(PPh3)2]+, isolated as tetraphenylborate salts. Reaction of cis-[PtCl2(PPh3)2] with an excess of Na[MeNHC(S)NCN] in methanol gives the bis(thiourea monoanion) complex trans-[Pt{SC(NCN)NHMe}2(PPh3)2], characterised by NMR spectroscopy and an X-ray crystal structure determination. When cis-[PtCl2(PPh3)2] is reacted with 1 equiv. of Na[MeNHC(S)NCN] in methanol, with added NaBPh4, a mixture of isomers of the [Pt{SC(NHCN)NMe}(PPh3)2]+ cation is obtained.

Bromination and nitration reactions of metallated (Ru and Os) multiaromatic ligands and crystal structures of selected products

Abstract Three nitrogen-containing aromatic heterocycles, 2-(1′-naphthyl)pyridine, 2-phenylquinoline, and 2,3-diphenylquinoxaline, have been mercurated in the naphthyl or phenyl ring 2-position and then symmetrised to form the mercury compounds Ar2Hg (Ar=Nppy (3), Phqn (1) or Dpqx (5), respectively). These reagents are suitable for trans-metallation and reaction with MHCl(CO)(PPh3)3 affords the complexes M(η2-C,NAr)Cl(CO)(PPh3)2, (6, M=Ru, Ar=Nppy; 7, M=Os, Ar=Nppy; 8, M=Ru, Ar=Phqn; 9, M=Os, Ar=Phqn; 10, M=Ru, Ar=Dpqx; 11, M=Os, Ar=Dpqx) in which each product features an aryl ligand that forms a strongly chelated five-membered ring through coordination of the heterocyclic N atom. The chloride ligand in each of the complexes 6–11 can be replaced by dimethyl dithiocarbamate to give ultimately the mono-triphenylphosphine complexes, M(η2-Ar)(η2-S2CNMe2)(CO)(PPh3) (12, M=Ru, Ar=Nppy; 13, M=Os, Ar=Nppy; 14, M=Ru, Ar=Phqn; 15, M=Os, Ar=Phqn; 16, M=Ru, Ar=Dpqx; 17, M=Os, Ar=Dpqx). Similarly, compound 10 when treated with Na(acac) gives Ru(η2-Dpqx)(η2-acac)(CO)(PPh3) (18), while treatment with trifluoroacetic acid gives Ru(η2-Dpqx)(O2CCF3)(CO)(PPh3)2 (19). Many of these complexes were found to be very robust, making them suitable for electrophilic aromatic substitution reactions under harsh conditions. In each case, the presence of the metal had both an activating and a directing effect on the aryl ring to which it was bonded. Bromination or nitration reactions, both of which are not normally possible with organometallic substrates, were carried out successfully, giving rise to monobrominated or dinitrated products, respectively. The following compounds were characterised, M(η2-Ar-4-Br)Cl(CO)(PPh3)2 (20, M=Ru, Ar=Phqn; 21, M=Os, Ar=Phqn; 22, M=Ru, Ar=Dpqx; 24, M=Os, Ar=Dpqx), M(η2-Dpqx-4-Br)(η2-S2CNMe2)(CO)(PPh3) (23, M=Ru; 25, M=Os), Os(η2-Ar)Cl(CO)(PPh3)2 (26, Ar=Nppy-6,8-(NO2)2; 27, Ar=Phqn-4,6-(NO2)2). Crystal structures of compounds 7, 12, 15, 18, 19, 21, 23 and 25 have been determined.

Trifluoromethyl, difluorocarbene and tetrafluoroethylene complexes of iridium and the crystal structures of IrI(CH3)(CF3)(CO)(PPh3)2, Ir(CF3)(C2F4)(CO)(PPh3)2 and Ir(CF3)(CF2)(CO)(PPh3)2

Abstract A trifluoromethyl iridium(I) complex Ir(CF3)(CO)2(PPh3)2 (1 has been prepared by the reaction of Hg(CF3)2 with IrH(CO)2(PPh3)2, or by thermal decomposition of Ir(COCF3)(CO)2(PPh3)2 (3), which is produced from (CF3CO)2O and a reduced iridium(−I) species. Either the reaction of IrH(CO)(PPh3)3 with Hg(CF3)2 or the reversible thermal decarbonylation of 1 yields the coordinatively unsaturated complex Ir(CF3)(CO)(PPh3)2 (2). Derivatives Ir(CF3)L(CO)(PPh3)2 (L = C2F4 (4), L = C2H4 (5), L = O2 (6)) result from treatment of 1 with tetrafluoroethylene, or 2 with ethylene or oxygen, respectively. Both 1 and 2 undergo oxidative addition of Cl2, I2, HCl, H2 and CH3I to give trifluoromethyl iridium(III) complexes IrCl2(CF3)(CO)(PPh3)2 (7), IrI2 (CF3)(CO)(PPh3)2 (8), IrHCl(CF3)(CO)(PPh3)2 (9), cis-IrH2(CF3)(CO)(PPh3)2 (10) and IrI(CH3)(CF3)(CO)(PPh3)2 (11), respectively. The iodo ligand in 11 is labile and can be replaced by an acetonitrile ligand to yield [Ir(CH3)(CF3)(L)(CO)(PPh3)2]ClO4 (L = CH3CN (12)). This ligand can in turn be replaced by p-tolylisocyanide (L = CN-p-C6H4CH3 (13)) or Cl− to give IrCl(CH3)(CF3)(CO)(PPh3)2 (14). Complexes 1 and 9 each react with AlCl3 to give the difluoromethyl species IrCl2(CF2H)(CO)(PPh3)2 (15). A difluorocarbene iridium(I) complex, IrCl(CF2)(CO)(PPh3)2 (16), has been prepared by thermal decarbonylation of Ir(COCF2Cl)(CO)2(PPh3)2 (18), and a complex containing both CF3 and CF2 ligands, Ir(CF2)(CF3)(CO)(PPh3)2 (17), has been made by treatment of either IrCl(CO)(PPh3)2, 2 or 16 with Cd(CF3)2 · glyme. Both 16 and 17 are hydrolysed to give carbonyl species IrCl(CO)2(PPh3)2 and 1, respectively, while 16 reacts with t-butylamine to give an isocyanide complex, IrCl(CN-t-C4H9)(CO)(PPh3)2 (20). Addition of HCl to 16 or 17 produces 15 or 9, respectively. Complexes 4, 11 and 17 have been characterised by X-ray diffraction studies.

Coordinatively unsaturated σ-aryl complexes of ruthenium(II) and osmium(II)

Abstract The hydrido complexes MHCl(CO)(PPh3)3 (M = Ru, Os) react with the organomercury compounds R2Hg (R = phenyl, p-tolyl, o-tolyl, trans-β-styryl) to give the five-coordinate, σ aryl and alkenyl complexes MRCl(CO)(PPh3)2 in high yield. Bromide and iodide analogues of these compounds can be prepared through reaction with silver perchlorate followed by addition of excess bromide or iodide ions. The X-ray crystal structures of two of the complexes, Ru(p-tolyl)Cl(CO)(PPh3)2 and Ru(o-tolyl)Cl(CO)(PPh3)2, have been determined.