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The reaction between [Pd2(dba)3]·solvent (dba 4;= 4;dibenzylideneacetone, solvent 4;= 4;CHCl3 or C6H6) and PBz3 (Bz 4;= 4;benzyl) in the presence of SO2 led to either [Pd2(µ-SO2)(µ-dba)(PBz3)2] 1 or [Pd3(µ-SO2)3(PBz3)3] 2 depending on the absence or presence of an excess of SO2 in solution or in the recrystallisation. The crystal structure of 2 shows it to be a regular triangulo-cluster with Pd–Pd bond distances 2.7225(9) Å. Complex 1 reacted with dppm with displacement of dba to give [Pd2(µ-SO2)(µ-dppm)(PBz3)2] 3. The crystal structure of 3 shows it to have a much shorter Pd–Pd bond length than 1 [2.670(2) Å for 3 cf. 2.885(2) Å for 1], which can be rationalised on the basis of the palladium atoms having been formally oxidised to PdI and the SO2 reduced to SO22–. Complex 1 reacted with PBz3 to give two mononuclear complexes, the previously characterised [Pd(dba)(PBz3)2] and the new complex [Pd(SO2)(PBz3)2] 4 which was characterised by a single crystal X-ray analysis. Complex 4 forms a distorted T-shaped structure with the P–Pd–P angle 163.67(14)°. It contains a η1-pyramidal SO2 ligand, and is the first mononuclear palladium SO2 complex to be crystallographically characterised. Complex 1 reacts with CO to give a mixture of the triangulo-clusters [Pd3(µ-CO)2(µ-SO2)(PBz3)3] 5 and [Pd3(µ-CO)(µ-SO2)2(PBz3)3] 6. Reaction with an excess of CO converted 6 into 5, and the crystal structure of 5 reveals relatively short Pd–Pd bond lengths consistent with a 42-electron cluster. Complex 1 reacted with CNBut to give [Pd3(µ-SO2)2(CNBut)2(PBz3)3] which has also been crystallographically characterised.

The lability of the ligand with a potential hydrogen bond donor–hydrogen bond donor arrangement was found to be the predominant factor in determining the structures of the adducts formed between zinc(II) complexes of thiourea [tu, NH2C(S)NH2] and thiosemicarbazide [tsc, NH2C(S)NHNH2] and the terephthalate anion [tere, C6H4(CO2–)2-1,4]. Reaction of [Zn(tsc)2][NO3]2, containing the bidentate thiosemicarbazide ligand, with sodium terephthalate led to a hydrogen-bonded structure, [Zn(tsc)2(OH2)2][tere]·2H2O, 1, in which the cations and anions are linked into chains through charge-augmented double hydrogen bonds between two NH protons on the tsc ligands and two oxygen lone pairs on the carboxylate. This chain formation is similar to that previously observed for related nickel complexes, although there are major differences in the way in which these chains are linked together into sheets. In contrast to the thiosemicarbazide complex, the reaction of [Zn(tu)4][NO3]2, containing unidentate thiourea ligands, with sodium terephthalate led to the formation of a co-ordinatively-bonded polymer, [Zn2(µ-tu)(tu)2(µ-tere)2]·4H2O, 2, in which the terephthalate anions have displaced some of the thiourea ligands from each zinc co-ordination sphere. The zigzag tapes formed by the terephthalate ligands bridging zinc atoms are linked together into double strands via bridging thiourea ligands.

The reactions between the palladium compounds [Pd4(3-CH)(-Cl)3(PBut 3)4] or [Pd2(-X)2(PBut3)2 ] (X = Br or I) and [Co2(CO)8] have led to the novel palladium–cobalt tetranuclear compounds [CoPd3(3-X)(-CO)3(3 -CO)(CO)(PBut3)3] (X = Cl, Br or I). Structural characterisation of one of them (X = Cl) has shown that the metal cluster geometry is intermediate between a tetrahedron and a butterfly. A second product detected in this reaction {and additionally with [Fe2(CO)9] and [Pd2(-Br)2(PBut3) 2]} is also reported and has been structurally characterised as [Pd6(-Br)4(-CO)4(PBut 3)4] (when X = Br). This hexanuclear cluster has triangular cluster moieties linked by double bromide bridges.

Strontium or barium metal granules reacted with an excess of HOSiMe2But in an ammoniacal toluene solution at -40 °C to produce the corresponding [M(OSiMe2But)2]n. The strontium complex was also obtained from silanolysis of the strontium ethoxide [{Sr(OEt)2(HOEt)4}n] with an excess of HOSiMe2But in hot toluene solution. Similarly, the reaction of [{Sr(OEt)2(HOEt)4}n] in hot toluene, with 1 molar equivalent of HOSiPh3 and Htmhd (2,2,6,6-tetramethylheptane-3,5-dione) yielded the trimeric complex [Sr3(tmhd)3(OSiPh3)3] ·0.5C6H5Me. The reaction of strontium or barium metal granules with 2 molar equivalents of diphenylsilanediol [Ph2Si(OH)2] in ammoniacal toluene solution at -40 °C yielded the polymeric complexes [{M[O(SiPh2O)2](H2O)(NH3 )x}n] [M = Ca (x = 0.3), Sr (x = 1) or Ba (x = 0.3)]. Similar reactions for strontium and barium in the presence of an excess of hmpa [OP(NMe2)3] produced [Sr3{O(SiPh2O)2}3 (hmpa)5]·C6H5Me and [Ba3{O(SiPh2O)2}3 (hmpa)5(H2O)], respectively. Alternatively, when these reactions were performed in the presence of tetraglyme [CH3O(CH2CH2O)4CH3 ] the water- and NH3-free complexes [M3{O(SiPh2O)2}3 (tetraglyme)2]·0.5C6H5Me were obtained (M = Sr or Ba). All complexes have been characterised by elemental analyses and IR, NMR (1H, 13C and 29Si, in selected cases 31P) spectroscopy and also by TGA/DSC studies. The complexes [Sr3(tmhd)3(OSiPh3)3] ·0.5C6H5Me and [Sr3{O(SiPh2O)2}3 (tetraglyme)2]·0.5C6H5Me have been characterised by X-ray crystallography. The structure of the former reveals a trimer of strontium cations stabilised by three tmhd ligands, and one - and two 3-bridging triphenylsiloxy ligands. Relatively short Sr · · ·   C (methyl) and Sr · · ·   C (phenyl) contacts have also been identified in this compound. In contrast, the three strontium cations in the latter are arranged in an almost linear array within a Sr3O9Si6 core.

Two new DTPA (diethylenetriaminepentaacetic acid) functionalised bis(amides) with pendant uracil moieties have been synthesised from the condensation reaction between DTPA bis(anhydride) and 5-aminouracil or 5,6-diaminouracil. These ligands are representative of an increasing number of ligands capable of forming triple hydrogen bonds with complementary organic bases. However, these ligands are unusual since they form water soluble complexes with a variety of metal ions. In this paper, the syntheses of the two DTPA-uracil ligands, seven metal complexes and the crystal structure of the bismuth complex of DTPA bis(4,5-diamino-6-hydroxy-2-mercaptopyrimidine) L1 are reported. The most important feature of this solid state structure is that the two arms on which the uracil moieties are situated have a high degree of rotational freedom and this allows these groups to form multiple hydrogen bonds involving both uracil moieties on one side of the molecule.

The insertion of carbon disulfide into the M–O bonds of the alkaline-earth-metal ethoxides and isopropoxides has been studied. The resulting products have been characterised by IR, 1H and 13C NMR spectroscopy, mass spectrometry and thermogravimetric analysis. Two of these complexes have been structurally characterised by single crystal X-ray crystallography and the data have confirmed the insertion of CS2 into both Ba–O bonds of [{Ba(OEt)2(EtOH)4}n] giving the polymer [{Ba(S2COEt)2}∞] and into both Ca–O bonds of [{Ca(OEt)2(EtOH)4}n] giving the monomer [Ca(S2COPri)2(PriOH)3]·2PriOH.

The insertion reactions of COS into the metal–alkoxide bonds of some alkaline-earth metals have been investigated. The resulting compounds have been studied spectroscopically (IR, 1H and 13C NMR), and by analytical techniques (TGA). The crystal structures of the strontium complex [{Sr(OCSOPri)2(PriOH)2}n] and the magnesium complex [Mg(OCSOPri)2(PriOH)4]·2PriOH have shown that whereas the former has a three dimensional structure the latter is monomeric.

The reaction between the dianhydride of ethylenedinitrilotetraacetic acid (edta) 1 and aminouracil derivatives was utilised to synthesize bifunctional, chelating ligands capable of co-ordinating to a metal centre via the edta backbone, while simultaneously being able to form complementary intermolecular hydrogen bonds via the uracil moieties. 5-Aminouracil 2, 5-aminoorotic acid 3, 5,6-diaminouracil 4 and 5,6-diamino-2-thiouracil 5 were treated with 1 in dry dmf or dmso to give functionalised dicarboxamide derivatives H2L1–H2L4 in 15–90% yield. The 5,6-diaminouracils 4 and 5 reacted with the dianhydride exclusively via the 5-amino position. The reaction of H2L1–H2L4 with basic metal salts [e.g. KVO3 and Zn(O2CMe)2] in aqueous solutions led to the formation of metal complexes of the anionic ligands L1–L4: K[VO2L1]·5H2O, [Zn(OH2)L1]·4H2O and [Zn(OH2)L3]·5H2O were characterized by single-crystal X-ray crystallography. The solid state structures of these complexes show that the uracil moieties are situated on pendant side-arms. The high degree of rotational freedom of these hydrogen-bonding groups makes this class of metal complex promising in terms of specific binding to water-soluble biomolecules having complementary hydrogen-bonding sites.

The new complexes [NEt3H][M(HL)(cod)] (M 4;= 4;Rh 1 or Ir 2; H3L 4;= 4;2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, orotic acid; cod 4;= 4;cycloocta-1,5-diene) have been prepared by the reaction between [M2Cl2(cod)2] and orotic acid in dichloromethane in the presence of Ag2O and NEt3. They crystallise as dichloromethane adducts 1·CH2Cl2 and 2·CH2Cl2 from dichloromethane–hexane solutions. These isomorphous structures contain doubly hydrogen-bonded dimers, with additional hydrogen bonding to NEt3H+ cations and bridging CH2Cl2 molecules to form tapes. The use of NBun4OH instead of NEt3 gave the related complex [NBun4][Rh(HL)(cod)] 1′ which has an innocent cation not capable of forming strong hydrogen bonds and in contrast to 1 exists as discrete doubly hydrogen-bonded dimers. Complex 1′ cocrystallises with 2,6-diaminopyridine (dap) via complementary triple hydrogen bonds to give [NBun4][Rh(HL)(cod)]·dap·CH2Cl2 3. Complex 3 exhibits an extended sheet structure of associated [2 4;+ 4;2] units, with layers of NBun4 cations separating the sheets. These structural data together with those reported previously for platinum orotate complexes suggest that the steric requirements of the other ligands co-ordinated to the metal are important in influencing their hydrogen-bonding abilities. The solvent of crystallisation, the hydrogen-bonding propensity of the coligand and the nature of the counter ion also determine the type of association in the solid state.

The in situ reactions of the tetraethanol-solvated alkaline-earth metal ethoxides [{M(OEt)2(EtOH)4}n] (M = Ca, Sr or Ba) with selected β-diketones and multidentate amines, resulted in the formation of tight cation–anion pairs, [H(L–L)]2[M(β-diket)4] [β-diket = 1,1,1-trifluoropentane-2,4-dionate (tfpd) or 1,1,1,5,5,5-hexafluoropentane-2,4-dionate (hfpd); L–L = N,N,N′, N′-tetramethylethane-1,2-diamine (tmen) or N,N,N′,N′,N″-pent amethyldiethylene-triamine (pmdien)] in relatively low yields. The products have been characterised by microanalysis, IR, 1H and 13C NMR and mass spectrometry. The complex [Htmen]2[Sr(tfpd)4] has been further characterised by X-ray crystallography. The structure contains a monomeric eight-co-ordinate [Sr(tfpd)4]2- dianion in which the four chelating tfpd ligands are in a square-prismatic arrangement, while the protonated tmen ligands are strongly hydrogen bonded to the tfpd chelates. The Sr–O distances lie in the range 2.530(2)–2.593(2) Å, average 2.571 Å.

The reaction of the Group 2 metal hydroxides, oxides or carbonates in 95% ethanol in the presence of a suitable glyme ligand L–L [i.e. Me(OCH2CH2)nOMe, n = 3, 4 or 7] and a β-diketone, has yielded either [M(β-diket)2(L–L)] or [{M(β-diket)2}2(L–L)] [M = Mg–Ba; β-diket = Htmhd (2,2,6,6-tetramethylheptane-3,5-dione), Hhfpd (1,1,1,5,5,5-hexafluoropentane-2,4-dione), Hdppd (1,3-diphenylpropane-1,3-dione) or Hfod (1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dione, L–L = tri-, tetra- or hepta-glyme)]. The crystal structure of the complex [{Ca(hfpd)2}2(heptaglyme)] has been determined, revealing it to contain two Ca(hfpd)2 units linked by a glyme ligand in an unusual symmetrical bridging/chelating mode.

The [Au(NCPh)2]+ cation has been isolated and synthesized in high yields by the oxidation of gold powder in the presence of NOBF4. It represents a labile form of gold(I), which has been shown to be a valuable synthon for the synthesis of a wide range of gold(I) complexes and especially of a variety of gold(I) amines which have opened new synthetic routes for the isolation of organometallic gold(I) complexes.

Some compounds of the alkaline-earth metals, which result from the insertion of COS into metal–ethoxide bonds, have been synthesized and characterised. The crystal structure of the first linear trinuclear metal strontium complex [Sr3(OCSOEt)6(EtOH)8] 2, which resulted from the reaction of [{Sr(OEt)2(EtOH)4}n] with COS gas, has been determined. The octahedral monomer [Mg(OCSOEt)2(EtOH)4] 1 resulted from the insertion of a molecule of COS into the ethoxide bonds of [{Mg(OEt)2(EtOH)4}n]. The structures demonstrate three alternative co-ordination modes of the OCS(OR)- ligand.

The synthesis, spectroscopic charcterisation and single crystal structure are reported for the novel tetranuclear cluster compound [Pd4(µ-SO2)2(µ3-S(CO)(PBz3)4], obtained when[Pd2(µ-dba)(µSO2)(PBz3)2] dba 4;= 4;dibenzylideneacetone, Bz 4;= 4;benzyl) is reacted with COS which fragments to give independent CO and S ligands on a tetrahedral cluster.

Microwave dielectric heating of the gas phase decomposition of H2S catalysed by metal sulfides on a γ-Al2O3 support results in significant apparent shifts in the equilibrium constant, which have been attributed to the development of hot-spots in the catalytic beds; X-ray diffraction and electron microscopy measurements have indicated the formation of hot-spots with dimensions of 90–1000 µm and which involve not only the active phase, but also the support.

The syntheses, characterisation and crystal structure (when X = Br) of [Pd4(3-CF)(-X)3(PBut 3)4] (X = Cl, Br) are reported; the 3-CF moiety is hydrogenated to CFH3 under mild conditions and serves as a model for the heterogeneous hydrogenation of CFCs to HCFCs.

The isolation and structural characterisation of square planar [Ni(atu)2] (Hatu = amidinothiourea) has provided a rational basis to synthesise the novel mixed-metal cage compounds [Ni4Pd2(atu)8X]X3 (X = Cl, Br); one of these cages (when X = Cl) has been crystallographically characterised showing that the chloride anion is encapsulated in the centre of the cage forming eight hydrogen-bonds with N–H groups from the ligands and two Lewis acid–base interactions with two palladium(II) ions.

In the presence of templating anions, 2:3 molar mixtures of triphos and silver(I) cations unexpectedly give novel hexanuclear cages, which result from an unusual ‘endo-methyl’ geometry of the triphos ligands.