Desmond Cunningham

A method for the prediction of the crystal structure of ionic organic compounds—the crystal structures of o-toluidinium chloride and bromide and polymorphism of bicifadine hydrochloride

The crystal structures of o-toluidinium chloride (1), o-toluidinium bromide (2) and two polymorphs of bicifadine hydrochloride (3) have been determined. The polymorphs of 3 differ in their molecular conformation and in their mode of packing. Crystallisation studies and quantum mechanical calculations show that the more readily crystallisable polymorph grows from the thermodynamically most stable conformer. On heating, conversion to the second polymorph takes place just below the melting point. The crystal structures of 1, 2 and the first polymorph of 3 have been successfully predicted using a procedure that is suitable for simple ionic organics.

Divalent metal phenylphosphonates and phenylarsonates

Abstract Phenylphosphonates and phenylarsonates of divalent magnesium, manganese, iron, cobalt, nickel, zinc and cadmium having compositions MPhRO3·H2O (M = all metals when R = P; M = all metals except iron and copper when R = As) and MPhRO3 (M = metal; R = P and As) have been isolated and characterized. Structures are suggested for the complexes based on infrared and electronic spectra, magnetic and X-ray diffraction data.

A reinvestigation of the reaction of [Fe2(η-C5H5)2(CO)4-n(CNR)n] (n = 1 or 2) with strong alkylating agents

Abstract The reaction of [Fe 2 (η-C 5 H 5 ) 2 (CO) 3 (CNR)] with R′OSO 2 CF 3 (R,R′  Me or Et) gives a mixture of cis and trans -[Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (μ-CO)μ-CN(R′)R]SO 3 CF 3 . When R  R′  Me the isomer ratio is variable, but the cis always predominates and is the only product when R ≠ R′. The complexes [Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (CNR) 2 ] react with R′OSO 2 CF 3 and the more reactive alkyl halides R′X to give a mixture of cis - [Fe 2 (η-C 5 H 5 ) 2 (CO)(CNR)(μ-CO)ν-CN(R′)R]X and cis -[Fe 2 (η-C 5 H 5 ) 2 (CO) 2 μ-CN(R′)R 2 ][X] 2 . In both series of cations the presence of μ-CN(R′)R ligands give rise to isomers that differ in respect of orientation about the CN bond. The cations are not fluxional and do not undergo cis - trans interconversion, bridge-terminal ligand exchange, or rotation about the μ-CN(R′)R double bond. The structure of the cations in the [Fe 2 (η-C 5 H 5 ) 2 (CO)(CNMe)(μ-CO)(μ-CNMe 2 )]BPh 4 and [Fe 2 (η-C 5 H 4 Me) 2 (CO) 2 (μ-CNMe 2 ) 2 ][SO 3 CF 3 ] 2 salts were confirmed as cis by X-ray diffraction studies. Their dimensions are similar to those previously found in cis - [Fe 2 (η-C 5 H 4 Me) 2 (CO) 2 (μ-CO)(μ-CNMe 2 )]I, but with variations due to the differing acceptor and donor abilities of the various ligands. Infrared and NMR spectra of the complexes are reported and discussed.

Transition-metal Schiff-base complexes as ligands in tin chemistry. Part 7. Reactions of organotin(IV) Lewis acids with [M(L)]2 [M=Ni, Cu and Zn; H2L=N,N′-bis(3-methoxysalicylidene)benzene-1,3-diamine and its -1,4-diamine analog]

Dinuclear complexes [M(3MeO-sal- m -phen)(H 2 O)] 2 [M=Cu, Ni and Zn; 3MeO–H 2 sal- m -phen= N,N ′-bis(3-methoxysalicylidene)benzene-1,3-diamine] and [M(3MeO-sal- p -phen)(H 2 O)] 2 [M=Cu, Ni and Zn; 3MeO–H 2 sal- p -phen= N,N ′-bis(3-methoxysalicylidene)benzene-1,4-diamine] were synthesised and reacted with diorganotin(IV) dihalides, dinitrates and dithiocyanates. Only in the case of those reactions involving [M(3MeO-sal- m -phen)(H 2 O)] 2 with M=Ni or Zn were adducts obtained as the sole products of reaction; the adducts were all tetranuclear complexes. The tetranuclear adduct {(SnBu n 2 ).[Ni(3MeO-sal- m -phen)(NCS) 2 ]} 2 · 6MeCN results from salicylaldimine ligands, related by a 2-fold axis, adopting bridging roles by co-ordinating to each of the symmetry related nickel atoms through phenolic oxygen and imine nitrogen atoms, while their phenolic and methoxy oxygen atoms form donor bonds to the tin atoms of symmetry related dibutyltin cations. The salicylaldimine ligands, related by inversion, adopt the same bridging role towards the nickel atoms in the adduct {[SnBz 2 (NO 3 )]·[Ni(3MeO-sal- m -phen)(NO 3 )]} 2 .6MeCN (Bz=benzyl), but as a result of the bidentate role of the nitrate co-ordinated to nickel, the arrangement of the phenolic and methoxy oxygens is such that each tin is co-ordinated quite strongly by a bidentate nitrate, a methoxy and two phenolic oxygen atoms while a second methoxy oxygen provides a weak Sn–O interaction, thus resulting in pseudo eight co-ordinate tin. 119 Sn Mossbauer parameters indicate that all of the adducts of di- and triorganotin halides are organotin aqua adducts with the donor water engaged in hydrogen bonding with Schiff-base oxygen atoms.

α-Keto amides as precursors to heterocycles—generation and cycloaddition reactions of piperazin-5-one nitrones

alpha-Keto amides 10a,b, formed from reaction of pyruvic or benzoylformic acid with allyl amine are found to present as single rotameric forms whilst their tertiary amido analogues 10c, d present as two rotamers in solution at rt. The hydroxyimino derivatives 8 share the conformational characteristics of their parents. The geometrical make-up of the new alpha-amidooximes is seen to depend on the structure of the starting acid and on the degree of substitution of the amido group. The oxime 8a derived from pyruvic acid and allyl amine is formed solely as the (E)-isomer whilst its tertiary amido analogue 8c is formed as both (E)- and (Z)-isomers. Oximes derived from benzoylformic acid have the opposite selectivity with both geometrical isomers forming from the secondary amide 8b and only the (Z)-isomer from the tertiary amide 8d. With the exception of 8b all oximes were configurationally stable with (Z)-isomers reacting to form isoxazolopyrrolidinones 11--compounds with a relatively rare bicyclic nucleus and (E)-isomers cyclising to piperazin-5-one nitrones 1--ketopiperazine N-oxides have to date only appeared once in the literature. New nitrones were trapped with phenyl vinyl sulfone, dimethyl acetylenedicarboxylate and methyl propiolate yielding isoxazolidine and isoxazoline fused piperazinones 13, 15, 21 and 22. Cycloadducts from dimethyl acetylenedicarboxylate and 8a, b are thermally labile and their rearrangement provides a novel route to pyrrolopiperazinones 16. The structure of a representative isoxazolopyrrolidinone, 11c, and a 2,3-dihydroisoxazoline fused piperazinone, 21b, are unambiguously solved following x-ray structural analysis.

Transition metal Schiff-base complexes as ligands in tin chemistry: IV. Reactions of triphenyltin chloride with divalent metal salicylaldimine complexes and the molecular structures of [SnPh3Cl · H2O][Ni(3-MeOsal1,3pn) · H2O] (1:1) and [SnPh3Cl · H2O]Ni(3-MeOsal1,3pren) (1:1) [H23-MeOsal1,3pn N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine]

Abstract Unlike diorganotin(IV) dihalides, triphenyl- and tribenzyl-tin chlorides do not react with Schiff-base complexes M(SB) (M  Cu II , Ni II and Zn II ; SB  N , N ′-ethylenebis-salicylideneaminato and related salicylaldimine ligands). Triphenyltin chloride does however form 1:1 addition complexes with 3,3′-methoxy substituted salicylaldimines of Ni II and Cu II , but only in the presence of water. Each of these complexes contains the aquo adduct SnPh 3 Cl · H 2 O, with the donor water molecule engaged in hydrogen bonding interactions with the four oxygen atoms of the divalent metal salicyaldimine. These structural features were confirmed crystallographically for (SnPh 3 Cl · H 2 O)Ni(3-MeOsal1,3pn) (1:1) [H 2 3-MeOsal1,3pn  N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine]. In the case of [SnPh 3 Cl · H 2 O][Ni(3-MeOsal1,3pn) · H 2 O] (1:1) both the water molecule coordinated to nickel and the water molecule coordinated to tin engage in hydrogen bonding interactions with the Schiff-base oxygen atoms, thereby creating centrosymmetric hydrogen-bonded dimers.

Transition-metal Schiff-base complexes as ligands in tin chemistry. Part 3. An X-ray crystallographic and tin-119 Mössbauer spectroscopic study of adduct formation between tin(IV) Lewis acids and nickel 3-methoxysalicylaldimine complexes

1:1 Addition complexes of [NiIIL]·H2O [H2L =N,N′-bis(3-methoxysalicylidene)ethylenediamine (3MeO-H2salen), N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine (3MeO-H2salpn) or N,N′-bis(3-methoxysalicylidene)-o-phenylenediamine (3O-H2salphen)] with SnR2Cl2(R = Me or Ph), SnBunCl3, or SnCl4 have been found to be generally monoaqua adducts of the tin Lewis acids with the water engaged in hydrogen bonding with the methoxy and phenolic oxygen atoms of the Schiffbase ligand. Both water and methoxy oxygen atoms are involved in donor-bond formation to tin in the polymeric structures 2SnMe2Cl2·[Ni(3MeO-salen)]·H2O and SnMe2Cl2·[Ni(3MeO-salphen)]·H2O, each of which has two very different tin environments. The two octahedral tin sites in the structure of SnMe2Cl2·2[Ni(3MeO-salphen)·H2O] appear to result from two isomeric forms of the adduct co-existing in a lattice as a result of hydrogen-bonding interactions. Crystal-structure determinations revealed that the monoaqua adducts of dimethyltin dichloride which exist in the structures SnMe2Cl2·[Ni(3MeO-salen)]·H2O and SnMe2Cl2·[Ni(3MeO-salon)]·H2O differ in that, in the former tin is in a trigonal-bipyramidal environment, whereas in the latter it is in an octahedral environment as a result of an intermolecular Sn ⋯ Cl contact of 3.615 A.

Enzymatic generation of planar chirality in the (arene)tricarbonylchromium series

Abstract Hydrolysis using pig liver esterase of the meso diesters [ortho-C 6 H 6 (CH 2 CO 2 R) 2 ]-Cr(CO) 3 (R = Me,Et) yields the half ester in good yield and high enantiomeric excess.

Pyrimidine annelated heterocycles—synthesis and cycloaddition of the first pyrimido[1,4]diazepine N-oxides

5-Formyl- and 5-acetyl-4-(alkenylamino)pyrimidines 5 have been prepared as precursors to novel pyrimido[1,4]diazepine N-oxides 3. In addition to cyclisation to the targeted dipoles the substrates 5 have also been observed to form imidazopyrimidines 12 and 39via an intramolecular Michael addition; additionally 5b has been observed to form the pyrimidoazepinone 42. Aldonitrone 3a cycloadded readily to olefinic dipolarophiles; ketodipole 3b did not share this reactivity. Both dipoles reacted with acetylenic dipolarophiles but the ensuing cycloadducts 37 were unstable; facile ring contraction of their isoxazolopyrimidodiazepine skeletons to the pteridine nucleus is noted. The structure of 37c has been determined by X-ray crystallography.

Lipase-assisted preparation of enantiopure ferrocenyl sulfides possessing planar chirality and their use in the synthesis of chiral sulfoxides

Abstract Racemic 2-hydroxymethyl-1-phenylthioferrocene 5 and 2-hydroxymethyl-1-tert-butylthioferrocene 6 were subjected to kinetic resolution via acetylation catalysed by lipase from Candida antarctica (Novozym® 435) or Mucor miehei (Lipozyme® IM). The obtained enantiopure thioethers underwent chemical oxygenation at the sulfur atom to give the corresponding ferrocenyl sulfoxides with settled central/planar chirality.