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The selective attachment of halide ions to a triply bridging site in the complex cation [Pd3(µ3-CO)(µ-dppm)3]2+(dppm = Ph2PCH2PPh2) has been established and the structure of the chloride adduct determined; the chloride ligand is very weakly bound to the Pd3 unit and is shielded by a ring of phenyl groups from the dppm ligands.

The 58-electron cationic cluster complex [Pt4(µ-H)(µ-CO)2(µ-dppm)3(dppm-P)]+, dppm = Ph2PCH2PPh2, has been characterized in solution by n.m.r. spectroscopy and in the solid by X-ray analysis of the PF6– salt; the cation displays novel fluxionality with rapid rotation of a µ-H below and a µ-Pt(CO)2(dppm-P) unit above a Pt3(µ-dppm)3+ triangle.

Reaction of Pd(OAc)2 with Ph2PCH2PPh2 under CO in a solvent containing excess of CF3CO2H yields the first example of a dicationic cluster of palladium, [Pd3(µ3-CO)(µ-Ph2PCH2PPh2)3]2+, the structure of which has been established by X-ray crystallography.

An X-ray diffraction study of the title compound reveals that it contains a PtII→PtII donor–acceptor bond and confirms the other features of its novel structure previously deduced from n.m.r. evidence.

Platinum(II) chloride complexes of MeSCF2CH2SMe, CF3SC2H4SCF3, and CF3SCHMeCH2SCF3 have been prepared as mixtures of isomers in solution: the crystal structure of one form of [PtCl2(CF3SCHMeCH2SCF3)] has been determined.

X-Ray diffraction study of the title compound has shown that [Pt2(µ-Ph2PCH2)3] adopts a ‘manxane’-type (bicyclo[3.3.3]undecane-type) structure, with trigonal planar co-ordination of the platinum atoms and approximate C3h molecular symmetry.

Spectroscopic and crystallographic data are presented for trans-[PtCl(CH2SiMe3)(PMe2Ph)2]; by comparison of data for cis-[Pt(CH2Y)2(PMe2Ph)2] and trans-[PtCl(CH2Y)(PMe2Ph)2](Y = H, Ph, or Me3Si) it is concluded that the trans-influence of the ligands decreases in the order Ph2MeSi– > YCH2–, and that the group Y has a minor role.

Notable differences between corresponding bond lengths and interbond angles in the complexes blue cis-mer-[MoOCl2(PMe2(Ph)3] and green cis-mer-[MoOCl2(PEt2Ph)3] are caused by ligand repulsions; an explanation of the isomerism of mer-[MoOCl2(PMe2Ph)3] is suggested in terms of the structures of the above complexes.

The crystal and molecular structure of the title compound has been determined by X-ray analysis. Crystals are orthorhombic, space group Pbca, with Z= 8 in a cell of dimensions a= 15·818(7), b= 15·742(6), c= 11. 608(6)A. The structure was solved by direct methods and refined to R 0·098 by the method of full-matrix least-squares, by use of 926 intensity data measured on a diffractometer. The crystals contain discrete molecules of almost exact C8 symmetry. The [P–N]2 ring is slightly puckered and the chlorine atoms are mutually cis. There are no significant differences between chemically equivalent bond lengths, and mean values are P–N 1·689(4) P–Cl 2·105(9), N–C 1. 498(11), and C–C 1·564(8)A.

Octaethylporphin, oepH2, and [RhCl(CO)2]2 react in hot chloroform to form a complex, which has been shown by chemical analysis, spectroscopic studies, and X-ray analysis to be [oepH4]2+2{cis-[RhCl2(CO)2]}–. Crystals are tetragonal, space group P4/n, Z= 4, with cell dimensions a= 24·604(3) and c= 8·231(1)A. The structure has been refined by Fourier and least-squares methods to R 0·089 for l439 diffractometric intensity data. A novel feature of the structure is the essential planarity of the [oepH4]2+ dication. Other new complexes to have been prepared are Co(oep)(PR3)2, [Co(oep)(PR3)2]+Br–, and Co{N:C(CF3)2}(oep).

Reaction of the title ligand (dpdo) with nickel(II) salts leads to the isolation of [Ni(dpdo)X2](X = Cl, Br, I, or NCS) complexes. In the solid state the previously prepared complex [Ni(dpdo)I2] is distorted square planar, whilst [Ni(dpdo)X2](X = Cl or Br) are pseudo-tetrahedral; all are planar in methylene chloride. A single-crystal X-ray analysis of the thiocyanate complex shows a monomeric planar species possessing a P–M–P angle of 175.9°. The ligand co-ordinates as a trans-bidentate diphosphine. The subtle effects governing the co-ordination properties of this ligand are illustrated by the isolation of the blue planar [Ni(dpdo)Br2]·C6H5Me complex, The pseudooctahedral complex [Ni(dpdo)Cl2]·4H2O and the planar [Ni(dpdo)(H2O)2][BF4]2 have also been isolated.

Reactions of [MCl2(PhCN)2](M = Pd or Pt) and K2[PtCl4] with S,S-dimethyl-N-heteroaromatic sulphimides Me2SNR (R = 2-pyridyl, 4-methyl-2-pyridyl, 2-pyrimidinyl, 4-methyl-2-pyrimidinyl, or 2-pyrazinyl) give 1 : 1 adducts trans-[M2Cl2(µ-Cl)2(Me2SNR)2](1) in which the sulphimide appears to co-ordinate through the ylide nitrogen according to 1H n.m.r. studies. Reaction of [MCl2(PhCN)2] with Me2SNPh gives a bis(sulphimide) complex trans-[MCl2(Me2NSPh)2](2) when M = Pd but when M = Pt a phenylnitrene derivative cis-[PtCl2(Me2SNPh)(NPh)](3) is obtained. Reactions of complexes (1) with phosphines L = PEt3, PMe2Ph, PMePh2, or PPh3, give 1 : 1 adducts [MCl2L(Me2SNR)][M = Pd; R = 2-pyridyl, L = PEt3, PMe2Ph, PMePh2, or PPh3, (4a)–(4d); M = Pt, R = 2-pyridyl, L = PEt3(4e); M = Pd, R = 2-pyrimidinyl, L = PPh3(4f)]. An X-ray analysis of cis-[PdCl2(PPh3)(Me2SNC4H3N2)]·CH2Cl2(4f) revealed that the pyrimidine rather than the sulphimide N atom is the point of attachment of the sulphimide ligand to Pd. Conformational energy calculations suggest that electronic rather than steric factors determine which N atom acts as donor to Pd. The crystals are monoclinic, space group P21/n, with a= 17.307(6), b= 9.182(1), c= 17.960(2)A, β= 97.15(2)°, R= 0.024 for 1 999 independent reflections with I > 3σ(I). N.m.r. studies suggest a trans structure for complex (4e) with sulphimide co-ordination via the pyridyl nitrogen. The isomerism and fluxional behaviour of (4c) and (4d) was studied by variable-temperature n.m.r. spectroscopy.

The crystal structure of the title compound has now been studied by neutron diffraction, based on some 300 independent reflexions, and refined by anisotropic least-squares to R 8·3%. The main features determined previously by X-ray diffraction of this highly symmetrical (cubic) structure are confirmed; the positions and vibrational motions of the hydrogen atoms have been elucidated.The short hydrogen bond, lying across a two-fold axis between tow crystallographically equivalent acetate groups, has O ⋯ O 2·475(14)A, and O ⋯ H ⋯ O 176(2)°, implying that the bond is not significantly bent. There is a large amplitude of internal libration of the methyl groups, estimated at ca. 26°(root-mean-square). This is discussed in relation to the packing of the methyl groups, which is evidently loose, in spite of there being two C ⋯ C contacts much closer than twice the conventional van der Waals radius of methyl carbon (2·0 A).

The synthesis and structure of 1,1-dimethyl-2,5-diphenyl-1-silacyclopentadienetricarbonylruthenium are reported, along with the structure of the uncomplexed ligand.

Marked differences have been found in the nucleophilic reactivity, basicity, and photoelectron spectra of geometrical isomers of the cyclodiphosph(III)azanes, (XPNBut)2(X = NMe2 or OMe), whose structures were assigned by reference to the crystal structure of cis-(C5H10N·PNBut)2.

Further reactions of perfluoroalkynes with metallic and organometallic derivatives will be described. The new reactions will include those of [(η5-C5H5)(OC)3M(μ-SR)M′(CO)5] and [(η5-C5H5)W(CO)3H] with hexafluorobut- 2-yne. The products include [(η5-C5H5)(OC)(CF3C2CF3)- W(μ-SMe)W(CO)5], [(η5-C5H5)(OC)2 WC(O)C(CF 3 )= C(CF3)H] and [(η5-C5H5)- (OC)([MeO]3P) WC(O)C(CF 3 = C(CF3)H] for which crystal structures will be described. The position of attack of alkynes upon bimetallic species will be rationalised. Spectroscopic and structural parameters of the complexes will be correlated with the presence of the perfluoroalkyl groups. The work has been supported by SERC, NATO and CNPq- Brazil.

The compounds trans-[M(CNR)2(dpe)2](M = Mo or W; R = Me, But or aryl; dpe = Ph2PCH2CH2-PPh2) have been prepared, and they can be protonated at one or both nitrogen atoms giving carbyne-like ligands, but alkylated at only one; X-ray structure analysis shows that the CNMe angle in trans-[Mo(CNMe)2(dpe)2] is 156(1)°.

Reaction of tin(II) chloride with Li(CPhCPh2) at –78 °C in diethyl ether–hexane–tetrahydrofuran affords a deep red solution whose colour fades on warming, and which we believe contains the (unstable) first dialkenyltin(II) species. The latter survives long enough at low temperatures to undergo intermolecular oxidative addition, and one such adduct leads ultimately to the formation of Sn(CPhCPh2)3Bun, which has been fully characterised including a crystal and molecular structure study. The mechanism of formation of the final product has been examined and results are reported.

Reaction of CF3CCCF3 with (π-C5H5)2Ni gives C6(CF3)6, C5H5Ni[C5H5(CF3CCCF3)2], [C5H5NiCF3CCCF3]4, and C5H5)2Ni3(CF3CCCF3)3 in addition to known products; the molecular structure of [C5H5NiCF3CCCF3]4 has been determined by X-ray analysis.

X-ray analysis of (Me3CNPCl)2 establishes that the (N–P)2 ring is slightly puckered; the exocyclic P–Cl bonds are unexpectedly long; and there are significant differences in the co-ordination of the chemically equivalent nitrogen atoms.