Kenneth W. Muir

Chiral Schiff base complexes of copper (II), vanadium (IV) and nickel (II) as oxidation catalysts. X-ray crystal structures of [Cu (R-salpn) (OH2)] and [Cu (±-busalcx)]

Abstract Several new complexes of chiral and achiral tetradentate Schiff bases with copper (II), nickel (II) and oxovanadyl (IV) ions have been synthesised and characterised and the structures of [Cu ( R -salpn) (OH 2 )] and [Cu (±-busalcx)] have been elucidated by X-ray analysis. [Cu ( R -salpn) (OH 2 )] is essentially square pyramidal with an unusually long bond [2.494 (4) A] from Cu to the oxygen of the apical water molecule. Molecules are linked by hydrogen bonding between the coordinated water and the salpn oxygens of neighbouring molecules. A long contact between a salpn CH 2 hydrogen and a neighbouring copper atom [H(3B). . .Cu = 2.966 (1) A] might be regarded as a CH···Cu hydrogen bond and completes a pseudo-octahedral coordination about copper. [Cu (±-busalcx)] displays tetrahedrally-distorted planar coordination about the copper atom and has no significant intermolecular contacts. The copper, nickel and vanadyl complexes were screened as homogeneous catalysts for the oxidation by Bu t OOH or H 2 O 2 of PhMeS to PhMeSO. All of them are active catalysts but of the chiral complexes only [Cu ( R , R -busalcx)] produced a reasonable enantiomeric excess (14%). Supporting the complexes on silica improved the enantioselectivity of the less sterically hindered [Cu ( R -salpn) (OH 2 )] ( from 2 to 10%), but diminished that of the more hindered [Cu ( R , R -busalcx)], probably by slowing the reaction to such an extent that the uncatalysed oxidation could compete effectively. Finally [Cu (salen)], [Cu ( R -salpn)] and [Ni ( R -salpn)] were synthesised in the pores of zeolites X and Y. These were shown to be active heterogeneous catalysts for the sulfide to sulfoxide oxidations, but no significant e.e. resulted from the use of the chiral catalysts.

ATM polymorphisms as risk factors for prostate cancer development

The risk of prostate cancer is known to be elevated in carriers of germline mutations in BRCA2, and possibly also in carriers of BRCA1 and CHEK2 mutations. These genes are components of the ATM-dependent DNA damage signalling pathways. To evaluate the hypothesis that variants in ATM itself might be associated with prostate cancer risk, we genotyped five ATM variants in DNA from 637 prostate cancer patients and 445 controls with no family history of cancer. No significant differences in the frequency of the variant alleles at 5557G>A (D1853N), 5558A>T (D1853V), ivs38-8t>c and ivs38-15g>c were found between the cases and controls. The 3161G (P1054R) variant allele was, however, significantly associated with an increased risk of developing prostate cancer (any G vs CC OR 2.13, 95% CI 1.17–3.87, P=0.016). A lymphoblastoid cell line carrying both the 3161G and the 2572C (858L) variant in the homozygote state shows a cell cycle progression profile after exposure to ionising radiation that is significantly different to that seen in cell lines carrying a wild-type ATM gene. These results provide evidence that the presence of common variants in the ATM gene, may confer an altered cellular phenotype, and that the ATM 3161C>G variant might be associated with prostate cancer risk.

The trans-influence of ligands in platinum(II) complexes. The significance of the bond length data

Abstract Bond lengths in electroneutral, monomeric chloroplatinum(II) complexes containing carbon-donor ligands indicate that there is a correlation between the extent of platinumcarbon multiple bonding and the length of the PtCl (trans to C) bond. A qualitative model is suggested to account for the trans-influence of both σ-donor and π-acceptor ligands on PtCl bonds.

An electron-rich olefin as a source of co-ordinated carbene; synthesis of trans-PtCl2[C(NPhCH2)2]PEt3

Interaction of the appropriate electron-rich olefin and chloride bridged PtII dimer has yielded the unreactive trans-PtII carbene complex (I) which is belived to isomerise thermally to the cis-isomer; the structure of the trans-complex is established inter alia by a single crystal X-ray analysis.

Synthesis and 31P NMR spectra of some platinum(II) complexes of the phospha-alkene, (mesityl)P=CPh2: Crystal and molecular structure of cis-[PtCl2(PEt3)(C6H2Me3P=CPh2)]·CHCl3

Abstract Syntheses of the phospha-alkene complexes cis - and trans -[PtCl 2 (PEt 3 )(mesityl)P=CPh 2 ], and cis - [PtX 2 {(Mesityl)P=CPh 2 } 2 ](X=Cl, I, Me) complexes are reported. 31 P NMR spectra indicate that bonding of the phospha-alkene to the metal is via the phosphorus lone pair and this is confirmed by a single crystal X-ray diffraction study of cis -[PtCl 2 (PEt 3 ){(mesityl)P=CPh 2 }]CHCl 3 .

The first synthetic studies on pestalotiopsin A. A stereocontrolled approach to the functionalised bicyclic coreElectronic supplementary information (ESI) available: crystal structure analysis of 18a. See http://www.rsc.org/suppdata/ob/b2/b209066j/

Pestalotiopsin A is a structurally unique, caryophyllene-type sesquiterpene which has shown immunosuppressive activity and cytotoxicity in preliminary assays. A stereocontrolled approach to the functionalised 2-oxabicyclo[3.2.0]-heptane core of pestalotiopsin A is described. This constitutes the first synthetic studies on pestalotiopsin A. Our approach includes a samarium(II)-mediated 4-exo-trig cyclisation and a trans-lactonisation process triggered by the addition of alkylytterbium reagents to a cyclobutanone intermediate. Further manipulation provides access to advanced intermediates which are excellent precursors for the future construction of the final ring of the target.

Dinuclear molybdenum thiolato-bridged compounds: syntheses, reactivities and electrochemical studies of site–substrate interactions

Abstract The synthesis, reactivity, structures and electrochemistry of dimolybdenum complexes jointly stabilized by cyclopentadienyl and bridging thiolate ligands are reviewed. The complexes involved are principally those of molybdenum(II) and molybdenum(III) and they contain from one to four thiolate bridges. It is shown that their reactivity can be controlled by varying the electronic and steric properties of the ancillary ligands and that they provide bimetallic sites for the activation and transformation of various substrates.

Electrochemical Cleavage of NdN Bonds at a Mo2(μ-SMe)3 Site Relevant to the Biological Reduction of Dinitrogen at a Bimetallic Sulfur Centre

The reduction of diazene complexes [Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(2)-H-N=N-R)](+) (R=Ph (3 a); Me (3 b)) and of the hydrazido(2-) derivative [Mo(2)Cp(2)(mu-SMe)(3)[mu-eta(1)-N=N(Me)H]](+) (1 b) has been studied by cyclic voltammetry, controlled-potential electrolysis, and coulometry in THF. The electrochemical reduction of 3 a in the presence of acid leads to cleavage of the N=N bond and produces aniline and either the amido complex [Mo(2)Cp(2)(mu-SMe)(3)(mu-NH(2))] 4 or the ammine complex [Mo(2)Cp(2)(mu-SMe)(3)(NH(3))(X)] 5, depending on the initial concentration of acid (HX=HTsO or CF(3)CO(2)H). The N=N bond of the methyldiazene analogue 3 b is not cleaved under the same conditions. The ability of 3 a but not 3 b to undergo reductive cleavage of the N=N bond is attributed to electronic control of the strength of the Mo-N(R) bond by the R group. The electrochemical reduction of the methylhydrazido(2-) compound 1 b in the presence of HX also results in cleavage of the N=N bond, with formation of methylamine, 4 (or 5) and the methyldiazenido complex [Mo(2)Cp(2)(mu-SMe)(3)(mu-eta(1)-N=N-Me)]. Formation of the last of these complexes indicates that two mechanisms (N=N bond cleavage and possibly H(2) production) are operative. A pathway for the reduction of N(2) at a dinuclear site of FeMoco is proposed on the basis of these results.

Reactions of co-ordinated ligands. Part 24. The reaction of bis-(but-2-yne)carbonyl(η-cyclopentadienyl or η5-indenyl)molybdenum tetrafluoroborate with acetonitrile and phosphines; crystal structures of but-2-ynecarbonyl(η5-indenyl)(triethylphosphine)molybdenum tetrafluoroborate and but-2-yne(η5-indenyl)bis(trimethylphosphine)molybdenum tetrafluoroborate

Reaction of the compounds [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] with refluxing acetonitrile in the presence of the respective acetylene affords the compounds [Mo(NCMe)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] where R = R1= Me; R = But, R1= H; R = Ph, R1= Me; R = Pr1, R1= H. Treatment of [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] at room temperature in methylene chloride with PEt3, PPh3, or P(C6H11)3 gives the monoacetylene compounds [Mo(CO)L(RC2R1)(η-C5H5 or η5-C9H7)][BF4][L = PEt3, PPh3, P(C6H11)3; R = R1= Me; R = But, R1= H; R = Pri, R1= H; R = Ph, R1= Me; or R = R1= C6H4Me-4]. Reaction of the acetonitrile complexes with the phosphines PEt3, PMe3, PMePh2, Ph2PCHCHPPh2, (Ph2PCH2)2, or (Me2PCH2)2 results in the displacement of both the acetonitrile and one acetylene ligand to form complexes of the type [MoL2(RC2R1)-(η-C5H5 or η-5-C9H7)][BF4]. X-Ray single-crystal crystallographic studies were carried out on the compounds [Mo(CO)(PEt3)(MeC2Me)(η5-C9H7)][BF4] and [Mo(PMe3)2(MeC2Me)(η5-C9H7)][BF4]. Crystals of the former are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 9.158(2), b= 14.726(2), c= 16.581(3)A, and β= 94.12(2)°. Crystals of the latter complex are also monoclinic, space group P21, Z= 2, in a unit cell of dimensions a= 8.661 (2), b= 10.293(2), c= 13.580(2)A, and β= 106.42(2)°. The structures have been refined to R 0.041 (R′ 0.045) and R 0.039 (R′ 0.048) for 4 329 and 2 052 respective reflections with I > 3σ(I). The molybdenum co-ordination in each cation may be described in terms of a pseudo-octahedral structure. The but-2-yne ligand adopts a similar conformation in both complexes lying approximately coplanar with either the Mo–CO or Mo–PMe3 bond. Variable-temperature 1H and 13C n.m.r. data are interpreted in terms of rotation of the acetylene. Examination of the 13C chemical shifts of the acetylene contact carbons suggests that in these complexes the acetylene ligand can act as a four-electron donor.

PALLADIUM(II) AND PLATINUM(II) COMPLEXES FORMED FROM C6H4-1,3-(CH2PCY2)2 (CY = CYCLOHEXYL) ; CRYSTAL AND MOLECULAR STRUCTURES OF PDXC6H3-2,6-(CH2PCY2) 2, X = CL AND BR

The reaction of C6H4-1,3-(CH2PCy2)2 (Cy = cyclohexyl) with [PdCl2(NCPh)2] gave mainly [PdCl2C6H4-1,3-(CH2PCy2)2]n which was converted into [PdClC6H3-2,6-(CH2PCy2)2] on prolonged reflux, whereas C6H4-1,3-(CH2PCy2)2 reacted with [PdBr2(PPh3)2] to give mainly [PdBrC6H3-2,6-(CH2PCy2)2]. Only [PtCl2C6H4-1,3-(CH2PCy2)2]n was formed in the analogous reaction with [PtCl2(NCPh)2]. X-ray analysis showed that [PdClC6H3-2,6-(CH2PCy2)2] and [PdBrC6H3-2,6-(CH2PCy2)2] are isostructural. Both molecules display a conformation of the terdentate PCP ligand that is different from that recently reported for several related molecules. It is concluded that the conformation adopted by C6H3-2,6-(CH2PR2)2 ligands appears to be dominated by the steric demand of the phosphorus substituents.