Anthony R. J. Genge

Multinuclear NMR studies of diphosphine, diphosphine–dioxide and diarsine complexes of tin(IV) halides. Structures of [SnI4{o-C6H4(AsMe2)2}] and [SnI4{o-C6H4(P(O)Ph2)2}]

The complexes [SnX4(L–L)] (X=Cl or Br, L–L=Me2PCH2CH2PMe2, Ph2PCH2CH2PPh2, o-C6H4(PPh2)2, o-C6H4(AsMe2)2, Ph2AsCH2CH2AsPh2) have been isolated from reaction of SnX4 with the ligand in anhydrous CH2Cl2. The complexes have been characterised by analysis, IR and multinuclear NMR (1H, 31P and 119Sn) spectroscopy. Rare examples of complexes with SnI4 have been isolated with all the above ligands except Ph2AsCH2CH2AsPh2 and similarly characterised. The multinuclear NMR studies reveal reversible ligand dissociation in some of the chloro- and bromo-complexes in solution, the extent varying with the neutral ligand involved, but all the iodo-complexes are extensively dissociated in solution. Complexes of PMe3 and the diphosphine–dioxide o-C6H4(Ph2PO)2 are also described. X-ray structures of [SnI4{o-C6H4(AsMe2)2}] and of [SnI4{o-C6H4(Ph2PO)2}] and its CH2Cl2 solvate are reported.

Radical cyclisations of methylenecyclopropyl azetidinones—synthesis of novel tricyclic β-lactams

Addition of lithium bis(methylenecyclopropyl)cuprates to acetoxy azetidinones gives methylenecyclopropyl azetidinones, which can be converted to various radical cyclisation precursors. Attempted 4- exo cyclisation of 3 led only to reduced product, while cyclisation of 5 , using CuCl/bipy, gave a carbacephem, via a 5- exo cyclisation, but in low yield. Cyclisation of 6 and 7 , however, gave novel tricyclic β-lactams, as the result of 7- endo cyclisation, in good yield, and a cyclisation of bromide 23 led to the tricyclic β-lactam 24 , via a radical cascade sequence.

Structural characterisation of solution species implicated in the palladium-catalysed Heck reaction by Pd K-edge X-ray absorption spectroscopy: palladium acetate as a catalyst precursor

Energy dispersive EXAFS (EDE), Quick EXAFS (QEXAFS), 13C NMR and X-ray crystallography have been used to probe the co-ordination sphere of palladium in the course of the phosphine free Heck reaction. [Pd2I6][NBu3H]2 has been isolated from the precatalytic solution and its crystal structure determined. EDE and QEXAFS spectra of the complexes Pd(OAc)2, Pd(PPh3)4 and [Pd2I6][NEt3H]2 illustrated the value of the technique in structure elucidation. EXAFS of the precatalytic solution detects [Pd2I6]2− and no co-ordinated carbon. EXAFS of the catalytic solution shows a first co-ordination sphere of 2 carbon atoms and a second of 2–2.5 iodines. A scheme involving an equilibrium between the oxidative addition product and the olefin co-ordination species, has been proposed to explain these results.

Complexes of distibinomethane ligands ☆: 3. Manganese and rhenium carbonyl complexes

Abstract Photolysis of Mn2(CO)10 with the distibinomethanes Ph2SbCH2SbPh2 (dpsm) and Me2SbCH2SbMe2 (dmsm) yields [Mn2(CO)6(dpsm)2] and [Mn2(CO)8(dmsm)], respectively, which have been characterised by IR, 1H, 13C{1H} NMR spectroscopies and fast atom bombardment (FAB) mass spectrometry. Similar photolysis of the ligands with Re2(CO)10 yields axially substituted [Re2(CO)9(η1-distibinomethane)]. The X-ray crystal structure of [Mn2(CO)6(dpsm)2] reveals two dpsm ligands, each bonding to the two metal centres [Mn–Mn 3.098(2), Mn–Sb 2.487(2)–2.500(2) A].

Synthesis, solution and magic angle spinning tin-119 nuclear magnetic resonance studies and crystal structures of dithioether complexes of tin(IV) halides

The compounds SnX4 reacted with 1 molar equivalent of dithioether, L–L, in dry CHCl3 solution to give the six-co-ordinate species [SnX4(L–L)][X = Cl, L–L = MeS(CH2)nSMe, o-C6H4(SMe)2 or PhS(CH2)nSPh (n= 2 or 3); X = Br, L–L = MeS(CH2)nSMe or o-C6H4(SMe)2] in high yield as white or pale yellow powdered solids. Using SnBr4 and PhS(CH2)nSPh or SnI4 with MeS(CH2)nSMe did not produce isolable products, although solution 119Sn-{1H} NMR spectroscopy provided evidence for their existence at low temperatures. X-Ray structural studies on [SnCl4{MeS(CH2)2SMe}], [SnCl4{MeS(CH2)3SMe}], [SnCl4{o-C6H4(SMe)2}], [SnCl4{PhS(CH2)3SPh}] and [SnBr4{MeS(CH2)3SMe}] confirmed an S2X4 donor set with the dithioether acting as a bidentate chelate. Variable-temperature solution 1H and 119Sn-{1H} NMR spectroscopic studies showed that the complexes are extremely labile and ligand dissociation and pyramidal inversion are fast except at low temperatures. Magic angle spinning 119Sn NMR data for [SnCl4(L–L)] are reported. The crystal structure of cis-[SnI4{MeS(O)(CH2)3SMe}2], obtained as a decomposition product from the SnI4–MeS(CH2)3SMe reaction, shows monodentate sulfoxide (O) co-ordination.

Hydrates of tin tetrachloride.

The crystal structures of the tri- and tetrahydrate of tin tetrachloride, viz. diaquatetrachlorotin(IV) monohydrate, [SnCl(4)(H(2)O)(2)].H(2)O, and diaquatetrachlorotin(IV) dihydrate, [SnCl(4)(H(2)O)(2)].2H(2)O, are reported and shown to contain the cis-[SnCl(4)(H(2)O)(2)] species and water molecules in both cases. The trihydrate contains chains of the tin species linked by a single hydrogen-bonded water molecule, whilst the tetrahydrate has a three-dimensional network. In addition, there are O-H.Cl interactions present.

Bismuth(III) thioether chemistry: the synthesis and structure of [Bi4Cl12(MeSCH2CH2CH2SMe)4]n·nH2O, a highly unusual network involving Bi4Cl4 rings and bridging dithioether ligands

The structure of [Bi4Cl12(MeSCH2CH2CH2SMe)4]n·nH2O involves Bi4Cl12(η1-MeSCH2CH2CH2SMe)4 tetrameric units which are linked by bridging dithioether ligands to give a three-dimensional polymeric network; the Bi4Cl4 core is an eight-membered heterocycle which adopts an open cradle conformation.

SYNTHESIS, MULTINUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC STUDIES AND CRYSTAL STRUCTURES OF MONO- AND DI-SELENOETHER COMPLEXES OF TIN(IV) HALIDES

Reaction of SnX 4 (X = Cl or Br) with Me 2 Se or diselenoether ligands in dry CHCl 3 produced white or yellow solids [SnX 4 L 2 ] in high yield [X = Cl, L 2 = MeSe(CH 2 ) n SeMe, PhSe(CH 2 ) n SePh (n = 2 or 3), C 6 H 4 (SeMe) 2 -o or 2Me 2 Se; X = Br, L 2 = MeSe(CH 2 ) n SeMe (n = 2 or 3), C 6 H 4 (SeMe) 2 -o or 2Me 2 Se]. These compounds have been characterised by a combination of variable-temperature 1 H, 119 Sn-{ 1 H} and 77 Se-{ 1 H} NMR, IR spectroscopy and microanalyses. Single-crystal X-ray diffraction studies on trans-[SnX 4 (SeMe 2 ) 2 ], [SnX 4 {C 6 H 4 (SeMe) 2 - o}] (X = Cl or Br) and [SnCl 4 {MeSe(CH 2 ) 3 SeMe}] confirm distorted octahedral geometry at Sn IV in each case, with the bidentate ligands chelating. The C 6 H 4 (SeMe) 2 -o complexes adopt the meso arrangement, while the ligand is in the DL form in [SnCl 4 {MeSe(CH 2 ) 3 SeMe}]. The trends in d(Sn–X) and d(Sn–Se) reveal that the trans influence of halide is greater than that of selenium in these systems. In comparable systems d(Sn–Se) is longer in the bromo than in the chloro systems, consistent with the greater Lewis acidity of SnCl 4 . The NMR studies revealed that pyramidal-inversion and ligand-dissociation processes are facile. In the SeMe 2 complexes both cis and trans isomers are present, while in the diselenoether systems the meso and DL forms are both apparent at low temperatures. The co-ordination shifts in the 77 Se-{ 1 H} NMR spectra are markedly dependent upon chelate-ring size; the first time this has been observed for complexes of a p-block metal.

Structural and spectroscopic studies on copper, silver and gold complexes of mixed phosphathia ligands and their chalcogenide derivatives

Reaction of [Cu(MeCN)4]PF6 or AgBF4 with 1 molar equivalent of Ph2P(E)(CH2)2SZS(CH2)2(E)PPh2[Z =(CH2)2, E = S (L1b) or Se (L1c); Z =(CH2)3, E = none (L2a), S (L2b) or Se (L2c); Z =o-C6H4, E = none (L3a), S (L3b) or Se (L3c)] in degassed acetone followed by addition of diethyl ether yielded the mononuclear complexes [ML]X (M = Cu, X–= PF6–; M = Ag, X–= BF4–) in high yield. The gold(I) species [AuL]PF6 were obtained by reaction of L (= L1b, L1c, L2b, L2c or L3a–L3c) with 1 molar equivalent of [AuCl(tht)](tht = tetrahydrothiophene) and TlPF6. All of these products have been characterised by 1H, 31P-{1H}(and in some cases 77Se-{1H} and 109Ag) NMR and IR spectroscopy, FAB or electrospray mass spectrometry and microanalyses. The data indicate four-co-ordination for all of the copper(I) and silver(I) species and this assignment has been confirmed by single-crystal structure determinations on three copper(I) examples. Spectroscopic studies on [AuL]PF6 indicated linear two-co-ordination on average, via the phosphine, phosphine sulfide or phosphine selenide functions as appropriate. Variable-temperature 31P-{1H}(and 77Se-{1H}) studies showed that the chalcogenide complexes are considerably more labile in solution than the phosphathia ligand complexes. Crystal structure determinations on [CuL3a]+, [CuL1c]+, [AgL1c]+ and [CuL2b]+ each showed the metal ion co-ordinated to all four donor atoms of a single ligand in the solid state, giving an overall distorted-tetrahedral stereochemistry. In the case of [CuL1c]+ there is a slight lengthening of the P–Se bond length compared to that of the unco-ordinated form of L3c. Syntheses for the new pro-ligands are also detailed.

Complexes of late transition metals containing the mixed donor ligands 2,6-(RSCH2)2C5H3N (R = Ph, Me): Crystal structures of [{Cu(2,6-(PhSCH2)2C5H3N)(μ-X)}2] (X = Cl, Br) and [Ni(2,6-(PhSCH2)2C5H3N)Br2]

A range of NiX2 and CuX (X = halide) complexes containing the tridentate NS2 ligands 2,6-bis(methylthiomethyl)pyridine (L1) and 2,6-bis(phenylthiomethyl)pyridine (L2) were prepared. Reaction of CuX with 1 molar equivalent of L1 or L2 afforded the binuclear species [{CuL(μ-X)}2] (L = L1, X = Cl; L = L2, X = Cl, Br, I). These compounds have been characterised by IR and 1H NMR spectroscopies, mass spectrometry and microanalysis. Crystal structure determinations of [{CuL2(μ-X)}2] (X = Cl, Br) confirm the dimeric nature of these complexes through bridging halide centres, with the NS2 ligands coordinated through their pyridyl nitrogens and one of the sulfur atoms in a bidentate manner. Reaction of NiX2 with 1 molar equivalent of L1 or L2 afforded mononuclear species for [NiLX2] (L = L1, X = I; L = L2, X = Br, I) and binuclear species for [NiLX2]2 (L = L1, X = Cl, Br; L = L2, X = Cl). These compounds have limited solubility and were characterised through IR and UV-Vis reflectance spectroscopies and microanalysis. The crystal structure determination of [NiL2Br2] confirms the compound to be monomeric with a five-coordinate, square pyramidal nickel centre.