William Errington

Biotransformation of αβ-unsaturated carbonyl compounds: sulfides, sulfoxides, sulfones, nitriles and esters by yeast species: carbonyl group and carbon–carbon double bond reduction

The reduction of αβ-unsaturated ketones with γ-sulfide, sulfoxide, sulfone, nitrile and ester functions has been investigated. Both CO and CC reduction was observed. In the sulfur series, CO bond reduction was always observed, but significant CC bond reduction was observed only with the sulfide. The unsaturated nitriles gave the corresponding alcohol as the major bioreduction product, with smaller but significant amounts of fully reduced product. A similar result was obtained with the ester substrate. Relative and absolute configurations of bioreduction products were determined. A comparison was made between reductions catalysed by bakers yeast (Saccharomyces cerevisiae) and by other yeasts (Zygosaccharomyces rouxii, Pichia capsulata, P. farinosa, Candida chalmersi and C. diddensiae). The tendency of Z. rouxii to give products enantiomeric with those obtained using S. cerevisiae was noted. The relationship between substrate structure and the stereochemistry of CC double bond reduction is discussed.

Synthesis and properties of some gallium amidine complexes [GaXyL3–y][X = Me, Et or Cl; L = RNCR′NR (R, R′= H, alkyl or aryl); y= 0–2]. Crystal structures of [GaMe2(PhNCPhNPh)] and [GaMe(PhNCPhNPh)2]

The amidinato compounds [GaMe2L][L = RNCR′NR (R,R′= H, alkyl or aryl)], [GaMe(PhNCPhNPh)2], [GaEt(PhNCMeNPh)2] and [Ga(PhNCRNPh)3](R = Me or Ph) have been isolated from the reaction of the appropriate gallium trialkyl with 1, 2 and 3 mol of amidine RNCR′N(H)R, respectively. The chloro derivatives [GaCl3{RNCR′N(H)R}](R = Ph or p-ClC6H4; R′= Me) and [GaCl2(p-ClC6H4NCMeNC6H4Cl-p)] have also been prepared. The compounds have been fully characterised, and mass spectrometric data indicate that the volatile dimethylgallium derivatives exist as either monomers or dimers in the gas phase. X-Ray crystallographic studies on [GaMe2(PhNCPhNPh)] and [GaMe(PhNCPhNPh)2] revealed monomeric structures and the presence of chelating amidinate ligands, with distorted tetrahedral and trigonal-bipyramidal co-ordination respectively at the metal centres. Cleavage of the Ga–Me bond occurs on photolysis in the presence of a spin-trapping agent, and thermal decomposition of the solids leads to the formation of gallium nitride.

Pyridyl-, bipyridyl-, and terpyridyl-functionalised azamacrocycles

Abstract A series of azamacrocycles which have been N-functionalised with pendent pyridylmethyl-(pyCH2-), bipyridylmethyl-(bipyCH2-) and terpyridylmethyl- (terpyCH2-) arms have been synthesised and characterised, and some of their coordination chemistry with transition metal ions is reported. By attaching the pendent-arms at the 5- rather than the 6-position of the py, bipy and terpy, new ligands are generated which can be used to form polynuclear metal complexes in a controlled and systematic fashion. Fluorescent pH and transition metal ion sensors have been developed by reacting the azamacrocyclic N-pendent bipyCH2 arm(s) with cis-[Ru(bipy)2Cl2], to give macrocycles with up to four attached [Ru(bipy)3]2+ groups. That based on 1,4,7-triazacyclononane (9N3), with three attached [Ru(bipy)3]2+ groups, has a first photo excited state pKa of 7.1, and is a useful fluorescent sensor for physiological pH at below micromolar concentrations. The analogous derivative of cyclam (1,4,8,11-tetraazacyclotetradecane) ca...

Crown thioether chemistry of Tin(IV) : formation and crystal and molecular structures of 3SnCl4.2[9]aneS3 and 2SnCl4.[18]aneS6.MeCN ([9]aneS3 = 1,4,7-trithiacyclononane; [18]aneS6 = 1,4,7,10,13,16-hexathiacyclooctadecane)

Reactions of tin(IV) chloride with selected thiacrown ligands in acetonitrile have been studied. With [9]aneS3(1,4,7-trithiacyclononane) the yellow compound 3SnCl4·2[9]aneS3 has been isolated and structurally characterised by X-ray diffraction: orthorhombic, space group Pbca, a= 11.245(5)A, b= 12.927(6)A. c= 23.779(10)A, Z= 4, at 230(2) K. The structure consists of six-co-ordinate [SnCl3([9]aneS3)]+ cations and [SnCl6]2– anions in the ratio 2 : 1. In the cation the thiacrown is chelated facially to a SnCl3 unit with Sn–Cl 2.369(4)(mean), Sn–S 2.637(4)A(mean). The [SnCl6]2– counter anions exhibit a regular octahedral geometry with Sn–Cl 2.448(4)(mean)A. The reaction with [18]aneS6(1,4,7,10,13,16-hexathiacyclooctadecane) provides yellow crystals of the adduct 2SnCl4·[18]aneS6·MeCN the structure of which has also been determined by X-ray diffraction; monoclinic, space group C2, a= 16.901 (5), b= 12.968(5), c= 7.284(3)A, β= 100.50(3)°, Z= 2, at 240(2) K. The structure consists of two SnCl4 units located at opposite ends of the ring cavity with one above and the other below the ring plane. Each tin atom is six-co-ordinate and is attached to the ring via cis chelation of two sulfur atoms.

CROWN ETHER COMPLEXATION OF Hg(II): SYNTHESIS AND CRYSTAL STRUCTURE OF [(HgCl2)2(DIBENZO-24-CROWN-8)]

T h e dinuclear c o m p o u n d [(HgCI2)2(dibenzo-24-crown-8)] has been isolated as co lour less , b lock crys ta ls and s tructural ly characterised by X-ray diffraction s tudies . T h e structure is cen t rosymmet r i c and cons i s t s of a core C I H g ^ C I ) ; H g C I unit entrapped within the r ing cavity wi th each metal centre directly bonded to three of the c rown oxygen a toms . H g C I , e r m i n a i 2 . 3 0 6 ( 4 ) Ä , H g C l b r i d « i n g 2 . 3 2 6 ( 4 ) , 3 . 1 8 9 ( 3 ) Ä and H g O c r o w „ 2 . 6 4 0 ( 9 ) 2 . 7 7 2 ( 8 ) A . In troduc t ion . C r o w n ether complexa t ion of mercury(Il) halides and pseudoha l ides has been ex tens ive ly reported in the li terature. For 18-membered-r ing O-donor and N-donor macrocycles (L), the p roduc t s are neutral , m o n o m e r i c complexes , LHgX 2 , in which the metal centre adopts a h igh co-ordinat ion n u m b e r , e .g. L = 18c r o w n 6 , X = CI, B r , 2 1 / SCN; 4 L = d i b e n z o l 8 c r o w n 6 , X = CI, I, CN; 6 L = the pentaoxo-aza coronand 1 ,4 ,7 ,10 ,13-pentaoxo-16-azacylcooctadecane and its N-methy l der ivat ive, X = CI. 7 In the case of the hexaaza ligand [18]aneN 6 , by way of contrast , the ionic product [LHg][HgCLi] is observed . 8 C r o w n th ioe ther complexa t ion of mercury(II) to give binuclear complexes with exocycl ic pos i t ion ing of metal centres wi th reduced ligand dentici ty has also been reported, e.g. [ (HgBr 2 ) 2 (18-S-6) f and [ (HgBr : ) 2 (24-S-8) ] . ° Herein we report the synthes is and structure of the 2:1 adduct of Hg(II) chlor ide with d ibenzo-24c rown-8 (L). Mater ia l s and Methods . Manipu la t ions were performed us ing standard Schlenk techniques . HgCI 2 and d ibenzo-24-crown-8 were used direct ly as obta ined commerc ia l ly (Aldrich) . The IR spectra were recorded as N u j o l mu l l s placed be tween Csl plates us ing a Perk in-Elmer 5 8 0 B instrument and the H (250 M H z ) N M R spec t ra w e r e recorded us ing a Bruker A C 2 5 0 spect rometer . | (HgCl2)2(dibenzo-24-cro>vn-8) | . A solution of d ibenzo-24-c rown-8 (0 .20 g, 0 .44 m m o l ) in to luene (15 cm ) w a s added d ropwise to a solut ion of H g C l · (0 .24 g, 0 .88 m m o l ) in to luene (15 cm) and the mix ture heated at 50 ° C for 3 hrs . T h e resul t ing solut ion w a s f i l tered whilst still hot , concentrated (ca. 50 % by vo lume) and then cooled to room tempera tu re to p rov ide a whi te solid, which was washed with n -hexane ( 3 x 1 0 c m ) , and p u m p e d to d ryness in vacuo fo r several hours . Recrystall isation f rom toluene a f forded colourless block crystals sui table for X-ray d i f f rac t ion s tudies . Yield 0 .29 g, 66 %. (Found: C, 29 .11 ; H, 3.41 % . Calcu la ted for C ^ H ^ O s H g C U : C , 29 .07 ; H, 3 . 2 5 % ) . IR: v J e m 1 (Nujo l ) : 1597m, 1525w, 1504s, 1485m, 1457s, 1375s, 1322s, 1272m, 1251s, 1208s, 1119s, 1105s, 1058s, 1044s, 1030s, 932s , 9 1 6 m , 8 6 6 m , 843w, 7 7 7 m , 742s , 6 0 5 w , 5 0 1 m ( l igand) . N M R ( d , M e C N ) , δ Η ; 6 .90-6 .99 (8H, m, aromatic) , 4 .13 -4 .16 (8H, t, C H , ) , 3 . 85 -3 .88 ( 8 H , t , C H 2 ) , 3 .70 (8H, s, C H : ) . X R a y Crys ta l l ography . Data were collected us ing a S iemens S M A R T C C D area-detector diffractometer. Absorp t ion correc t ions were appl ied us ing S A D A B S . The structure was solved by direct m e t h o d s and refined by fullmatr ix leas t -squares on F for all data using S H E L X L 97. Crys ta l Data: H g C I . O s C ^ , Μ = 991 .48 , triclinic, a = 8 .0709(8) , b = 8 .5276(8) , c = 12 .0572(9) Α, α = 101.379(3) , β = 107.864(3) , γ = 1 0 3 . 9 8 9 ( 3 ) ° , U = 732 .56(11) Α , Τ = 180(2) Κ, space g r o u p P l , Ζ = 1, μ ( Μ ο Κ ) = 2 .626 mm , 3665 ref lec t ions measured , 2509 unique (Rint = 0 .0312) . T h e final values of R l [1 > 2cy(I)J and w R 2 are 0 .0613 and 0 .1742 respectively. The highest residual e lect ron-densi ty peaks (max 6 .84 e . A J ) and bigges t holes ( -2 .53 e.A) are located close to the Hg a tom. 1 d i b e n z o 2 4 c r o w n 8 = 6 ,7 ,9 ,10 ,12 ,13 ,20 ,21 ,23 ,24 ,26 ,27dodecahydrod ibenzo[0 ,n ] [ 1 ,4 ,7 ,10,13,16,19,22]octaoxycyclote t racosine. A u t h o r to w h o m co r re spondence should be directed: e-mail < m s r e p @ s n o w . w a r w i c k . a c . u k >

Simple synthesis of L- and D-vinylglycine (2-aminobut-3-enoic acid) and related amino acids

A three-step synthesis of vinylglycine 1 has been developed using a readily available starting material (but-3-enenitrile 2), based on the Neber rearrangement of the corresponding N-chloroimidate, and using cheap, convenient reagents. Also described is a convenient optical resolution of the N-tert-butoxycarbonyl derivative by papain-catalysed enantioselective esterification in a two-phase system. From the optically active amino acid, related amino acids obtained via epoxidation, dihydroxylation and cyclopropanation have been prepared. The related β, γ-unsaturated amino acids (E)-2-aminopent-3-enoic acid 20 and (E)-2-amino-3-methylpent-3-enoic acid 22 have been synthesised using the same approach.

Stereochemical control of cis- and trans-TiCl2 groups in six-coordinate complexes [(L)TiCl2] (L2– = N2O2-donor Schiff base) and reactions with trimethylaluminium to form cationic aluminium species

The first example of a cis-configuration of the TiCl2 group in a six-coordinate titanium complex [(L)TiCl2], involving a tetradentate N2O2-donor Schiff base ligand (L2–), is reported, and reactions of such complexes with trimethyl aluminium have been shown to generate cationic aluminium species.

fac-Triaquatrichloroindium(III)

The structure of the title compound, [InCl 3 (H 2 O) 3 ], features In atoms in a distorted fac-octahedral geometry and involves a three-dimensional network of intermolecular hydrogen bonding. It is the first structurally characterized example of a discrete Iris-hydrate of a Group 13 M III halide (M = B, Al, Ga or In).

Halide-abstraction reactions of tin(IV) andlanthanide(III) chlorides in tetrahydrofuran: crystal andmolecular structures of[LnCl2(thf)5][SnCl5(thf)] where Ln = Ce, Gd or Yb

It has been established that halide abstraction from several nlanthanide(III) chlorides can be effected by tin ntetrachloride. Direct treatment (1∶1) of LnCl n 3 n where nLn = Ce, Gd or Yb with SnCl n 4 n in tetrahydrofuran n(thf) provided colourless compounds of the generic type nLnSnCl n 7 n(thf) n 6 n which have been identified nby X-ray crystallography as ionic salts n[trans-LnCl n 2 n(thf) n 5 n][SnCl n 5 n n(thf)]. The individual seven-co-ordinate cations feature a nregular pentagonal-bipyramidal metal geometry in which a ntrans-LnCl n 2 n unit is surrounded by five thf molecules narranged in an equatorial plane. These co-ordinated solvent molecules nadopt the familiar ‘propeller-like’ arrangement indicative nof a skew as opposed to envelope ligand conformation. For nLn = Ce, Ce–Cl 2.697(2), Ce–O mean 2.495(5) nA; for Ln = Gd, Gd–Cl 2.608(2), Gd–O nmean 2.415(4) A; for Ln = Yb, Yb–Cl n2.5375(13), Yb–O mean 2.346(4) A. The six-co-ordinate n[SnCl n 5 n(thf)] n - n anions common to the nseries show a two-fold axis of symmetry containing the metal atom, the noxygen (thf) atom and a chloride atom mutually trans to nthe latter. Bond distances for Ln = Ce, i.e. nSn–O 2.276(7), Sn–Cl mean 2.399(2) A, are typical nfor the series.

THE STRUCTURE OF [GaBr3 (Me3[9]aneN3)]: THE FIRST EXAMPLE OF A SIX CO-ORDINATE GALLIUM(III) BROMIDE COMPLEX

Reaction of equimolar quantities of gallium(lil) bromide and 1,4,7-tr imethyil ,4,7tr iazacyclononane (Me3[9]aneN3) in acetonitrile gives the neutral adduct [GaBr3(Me3[9]aneN3)]. A crystal structure determination (X-ray diffraction) confirms a halfsandwich topology in which the six co-ordinate metal centre adopts the expected facoctahedral geometry, following η 3 N-donor co-ordination of the azamacrocycle. Introduction. The co-ordination chemistry of the azamacrocycle 1,4,7-trimethyl-1,4,7tr iazacyclononane (Me3[9]aneN3) with a wide variety of transition metals and some of the heavier p-block metals has been investigated extensively by Wieghardt et al, A previous study of gall ium(ll l) chloride with Me3[9]aneN3 and [9]aneN3 produced the simple adducts LGaCI3 in non-aqueous media (without structural characterisation), whereas the reaction of gallium(lll) nitrate in aqueous solution with [9]aneN3 gave the structurally characterised dimer [( [9]aneN3)2Ga2^-0H)2^-CH3C02) ] l3H20. More recently the ligand 1,4,7-tris(2-amino-3,5-diferf-butylbenzyl)-1,4,7-triazacyclononane has been shown to complex gall ium(ll l) fluoride. Several six co-ordinate tris-pendant arm [9]aneN3 complexes of gallium(lll) have been reported of the type [(R3[9]aneN3)Ga] where R = -CH2C02; -CH2CH2S; -CH2P(Ph)02 and CH2C6H2(Me)20. From this laboratory we have reported the neutral 1:1 adducts [MCI3(Me3[9]aneN3)] featuring the Group 15 halides (M = As, Sb, Bi), together with the cationic species [AsCI2(Me3[9]aneN3)][^-CI)^-0)(AsCI2)2] and [SbCI2(Me3[9]aneN3)][SbCI6]. More recently we have isolated the Group 14 cationic species [MCI3(Me3[9]aneN3)] (M = Ge, Sn). Here we report the reaction of Me3[9]aneN3 with GaBr3 as part of our investigation of pblock main group metals with this classic η N-donor ligand. Materials and Methods. All manipulations were performed under a di-nitrogen and/or argon atmosphere using standard Schlenk, vacuum-line and glove box techniques. Acetonitrile was pre-dried over 4A molecular sieves and then freshly distilled over calcium hydride prior to use. The gal l ium(l l l ) bromide was obtained commercially (Aldrich Chemical Co.) and used without further purification. Me3[9]aneN3 was synthesised following the method reported by Wieghardt et a/. Caution: Solvation of GaBr3 is highly exothermic. [(Me3[9]aneN3)GaBr3]. A solution of Me3[9]aneN3 (0.20 g; 1.17 mmol) in acetonitrile (10 cm) was added dropwise to a chilled (-10 °C) and stirred solution of GaBr3 (0.36 g; 1.17 mmol) in acetoni t r i le (5 cm) / hexane (20 cm). The mixture was allowed to warm to room temperature and stirred for a further 3 hours. The solution was filtered and then concentrated and cooled to 0 °C to provide colourless needle crystals of the product. Yield: 0.38 g, 68 %. 5H(CD3CN), 3.55 (12H, s, backbone CH2), 3.12 (9H, S,N-CH3). X-ray crystallography. Crystal data and details of the structure refinement for the title compound are given in Table 1. Data were collected using a Siemens SMART CCD area-detector dif fractometer. A full hemisphere of reciprocal space was scanned by a combination of three sets of exposures; each set had a different φ angle for the crystal and each exposure of 10 s covered 0.3 ° in ω. The crystal to detector distance was 5.01 cm. Crystal decay was