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A family of tetra-n-butylammonium salts of bis(oxamato)palladate(II) complexes of formula (n-Bu4N)2[Pd(Lm)2]·pH2O [m = 1–9; L1 = N-phenyloxamate (pma) and p = 2 (1), L2 = N-2-methylphenyloxamate (2-Mepma) and p = 4 (2), L3 = N-4-methylphenyloxamate (4-Mepma) and p = 2 (3), L4 = N-2,3-dimethylphenyloxamate (2,3-Me2pma) and p = 3 (4), L5 = N-2,4-dimethylphenyloxamate (Me2pma) and p = 4 (5), L6 = N-2,5-dimethylphenyloxamate (2,5-Me2pma) and p = 7 (6), L7 = N-3,4-dimethylphenyloxamate (3,4-Me2pma) and p = 6 (7), L8 = N-3,5-dimethylphenyloxamate (3,5-Me2pma) and p = 5 (8)] have been prepared and characterized by spectroscopic methods. The crystal structure of 1 that has been solved by single crystal X-ray diffraction shares main structural features with that reported for (n-Bu4N)2[Pd(L9)2]·2CH3CONH2 [L9 = N-2,4,6-dimethylphenyloxamate (2,4,6-Me3pma) and CH3CONH2 = acetamide] (see F.R. Fortea-Perez et al. (2016)). Each palladium atom in 1 is four-coordinate with two oxygen and two nitrogen atoms from two fully deprotonated pma ligands building a centrosymmetric square-planar surrounding, the Pd N/Pd O bond lengths being 2.020(3)/2.003(2) A. The bis(oxamato)palladate(II) units in 1 are well separated from each other by the bulky organic cations, the resulting value of the shortest metal–metal separation being 9.56 A. This series of very stable, phosphine-free, complexes with well-defined structures were shown to efficiently catalyze the Heck reaction of aryl halides with olefins in DMF at 80 °C in 3 h, most likely involving Pd(II)/Pd(IV) species in the vinylation reaction of aryl halides, as well as the Suzuki coupling of aryl halides with arylboronic acids in the same solvent under similar conditions. The reaction conditions for both Heck and Suzuki couplings were optimized by varying the amount of the catalyst, and their scope was systematically studied by using different olefins and aryl halides. The influence of the number and positions of the methyl substituents from the phenyloxamate ligand on the catalytic activity is analyzed and discussed in the light of the results obtained.

New heterometallic Sn–Cu compound that contains copper atoms in two different oxidation states was obtained by the solid state reaction between Sn(OBut)2 (OBut = tert-butoxide) and Cu(hfac)2 (hfac = hexafluoroacetylacetonate). Single crystal X-ray diffraction study revealed the ionic structure of a compound that can be formulated as {[CuI3Sn2(OBut)6]+[CuII(hfac)3]−} (1) with no significant interactions between complex cation and anion. The anion is comprised of an octahedrally coordinated by three chelating β-diketonate ligands CuII atom that shows a typical tetragonal Jahn–Teller distortion of the polyhedron. The heterometallic [Cu3Sn2(OBut)6]+ cation features a CuI triangle capped by two Sn(OBut)3 units. All alkoxide ligands are μ2-bridging between Sn and Cu atoms providing a trigonal pyramidal geometry around tin that is consistent with lone pair SnII centers. An almost perfect triangular copper core is stabilized by cuprophilic interactions, similar to those in other polynuclear CuI compounds. The cation represents the first example of a CuI triangular arrangement that is not supported by μ3-centering atoms or by μ2-all-side bridging. Multinuclear NMR studies unambiguously confirm the retention of heterometallic cluster in solution as well as the absence of ligand redistribution between the anion and cation. The use of a mixed-ligand approach creates broad opportunities for designing new heterometallic complexes with unusual architectures that are not observed in homoleptic counterparts.

Two complexes, cis ( 1 ) and trans ( 2 ) (Au p NBT) 2 dppee ( p NBT = p -nitrobenzenethiol; dppee = bis(diphenylphosphino)ethylene) have been synthesized and characterized. X-ray diffraction studies reveal that cis -(Au p NBT) 2 dppee has an intramolecular gold–gold distance of 3.0036(3) A while the trans -(Au p NBT) 2 dppee crystal is a dimer with an intermolecular gold–gold distance of 3.1201(4) A. We have used UV–Vis spectroscopy, 1 H NMR, and 31 P { 1 H} NMR to investigate the photochemical reactivity of both complexes. In a range of organic solvents with λ > 230 nm cis -(Au p NBT) 2 dppee readily isomerizes to the trans isomer. Under these same conditions, the trans isomer does not isomerize to cis -(Au p NBT) 2 dppee, but undergoes a photochemical substitution reaction. In chlorinated solvents (CH 2 Cl 2 , CH 3 Cl) trans -(Au p NBT) 2 dppee reacts to form trans -(AuCl) 2 dppee ( 3 ) which crystallizes into an extended chain of molecules linked via intermolecular gold–gold distances of 3.0203(2) A. TDDFT calculations support the observed experimental results. We propose that at high energies the reaction is initiated by chlorine radicals from direct photolysis of the solvent. At longer wavelengths the excited state of the metal complex is the photoactive species, abstracting a chlorine radical from the solvent.

The reaction of Re 2 (O 2 CC 6 H 5 ) 4 Cl 2 with PMe 3 in ethanol in the presence of traces of air or a small amount of H 2 O 2 affords the unusual compound [Cl(PMe 3 ) 3 Re(μ-O 2 CC 6 H 5 )Re(O)] 2 (μ-O) 2 ( 1 ). The crystal structure of this new rhenium ‘dimer of dimers’ type compound has been established by X-ray crystallography. In this centrosymmetric molecule each dirhenium unit is supported by one benzoate ligand and further ligated by Cl, PMe 3 and O-ligands; the two dinuclear units are united by two μ-O atoms. Interestingly, the rhenium centers have rarely observed distinctly different coordination environments within the dimers, namely ReClOP 3 ReO 4 , which can be formally considered as Re(II)Re(IV) or Re(I)Re(V).

New dinuclear TiIV and TiIII complexes with the calix[4]arene ligand C28H20O4H4 (H4L) have been isolated from the reaction of Ti(NMe2)4, H4L, and Na (or KC8) in THF. X-ray analyses revealed a similar core structure for the two complexes Na4(THF)8[TiIV 2(μ-O)2L2] (1) and K4(THF)8[TiIII 2(μ-NMe2)2L2] (2). Two titanium atoms are bridged by two oxygen atoms in 1 and by two dimethylamido groups in 2 and are also supported by two deprotonated calix[4]arene ligands in a cone conformation. This resulted in a similar Ti⋯Ti separation of about 3.29 A in 1 and 3.28 A in 2 and in a distorted octahedral environment for each Ti center in both complexes. In contrast, in a novel complex 3, Na2(THF)6[TiIII 2L2], two TiIII atoms are supported only by two deprotonated ligands. This results in a five-coordinate environment for both titanium(III) centers with the separation between them being 3.133(1) A.

The reaction between the dirhenium(III,III) anion, [Re2Cl8]2−, and the secondary phosphine, PCy2H, yields a mixture of products as a result of disproportionation, namely, a dirhenium(II,III) chloride–phosphine complex 1,3,6-Re2Cl5(PCy2H)3 (1) and a dirhenium(IV) face-sharing bioctahedral compound with bridging phosphido groups, [Bun 4N][Re2(μ-PCy2)3Cl6] (2). The diphenylphosphine analogue of 2, [Bun 4N][Re2(μ-PPh2)3Cl6] (3) has been similarly prepared from the reaction of [Re2Cl8]2− with PPh2H. An interesting dirhenium(III,III) complex, [Bun 4N]2[Re2(μ-PPh2)2(PPh2H)2Cl6] (4) having both neutral terminal phosphines and anionic phosphido bridges, has also been isolated as an intermediate in the latter system. Crystal structures of 1–4 have been determined by X-ray crystallography. The compounds were also characterized by cyclic voltammetry, IR and 31P NMR spectroscopy.

A tetrameric complex [Re(CO)3(μ-CH3CO2)(THF)]4 (1) is formed in high yield when the reaction product of Re(CO)5Cl with acetic acid in refluxing 1,2-dichlorobenzene is dissolved in THF. The use of Re2(CO)10 instead of rhenium pentacarbonyl chloride also affords 1. The characterization of 1·3THF·0.5C6H14 has been accomplished by X-ray crystallography. The structure of the tetrameric molecule 1 consists of four rhenium(I) atoms bridged by four acetate ligands. The coordination of each metal center is fulfilled by three CO groups and one THF molecule in a way that all carbonyls are trans to oxygen atoms. The geometry of each acetate bridge is anti–syn providing a Re to Re separation of 5.40 A. This bonding mode is seen here for the first time in rhenium carboxylates. Different coordination types for Re–RCO2 interaction are also discussed in the paper.

The reactions of W 2 Cl 4 (NR 2 ) 2 (NHR 2 ) 2 (R=Et, Bu n ) with a stoichiometric amount of bis(diphenylphosphino)methane (dppm) readily resulted in the isolation of two new triply-bonded ditungsten(III) compounds cis,cis -W 2 Cl 4 (NR 2 ) 2 (dppm) (R=Et ( 1 ), R=Bu n ( 2 )) in moderate yields. The molecular structures of both compounds have been determined by X-ray crystallography and their crystallographic data are as follows: 1 ·CH 2 Cl 2 , monoclinic, space group C 2/ c , a =38.729(5), b =11.662(1), c =19.045(2) A, β =113.57(1)°, V =7884(2) A 3 , Z =8, R =0.026, wR 2=0.055; 2 , monoclinic, space group P 2 1 / n , a =14.4962(5), b =18.6305(8), c =17.1667(6) A, β =97.974(4)°, V =4591.4(3) A 3 , Z =4, R =0.043, wR 2=0.102. Both molecules are characterized by a W 2 6+ core with a σ 2 π 4 bond of order three and the W–W distances are 2.3350(3) and 2.3463(4) A, respectively, for 1 and 2 . They entail an essentially staggered rotational geometry and exhibit significant torsion angles in the solid state. Similar procedure has also been used to prepare similar W 2 6+ complexes containing bis(diphenylphosphino)amine (dppa) ligands and complexes of the type W 2 Cl 4 (NR 2 ) 2 (dppa) (R=Et ( 3 ), R=Bu n ( 4 )) have been characterized by 31 P{ 1 H} NMR spectroscopy at room temperature. In leading to the reaction pathway of complexes of this kind, the time sequences for the formation of 1 and 2 have been followed by variable temperature 31 P{ 1 H} NMR spectroscopic method. In all cases, the trans,trans -isomers of W 2 Cl 4 (NR 2 ) 2 (L–L) (R=Et, Bu n ; L–L=dppm, dppa) are the kinetically favored products while the cis,cis -isomers are the thermodynamic products. The corresponding cis,trans compounds are believed to be the likely intermediate complexes. In the course of a synthetic program directed towards the preparation of a dppa substitution complex of W 2 Cl 4 (NHCMe 3 ) 2 (NH 2 CMe 3 ) 2 , an unexpected ditungsten compound W 2 Cl 3 (NHCMe 3 ) 2 (NH 2 CMe 3 )(PPh 2 NPOPh 2 ) ( 5 ) has been prepared and structurally characterized. Compound 5 crystallizes in the triclinic space group P 1 , a =11.269(2), b =12.020(5), c =18.182(2) A, α =93.27(1), β =89.72(1), γ =93.275(2)°, V =2455(1) A 3 , Z =2, R =0.068, wR 2=0.153. The W–W distance in 5 is 2.3030(8) A and the molecule consists of an anionic bridging ligand [N(OPPh 2 )PPh 2 ] − , forming a six-membered metallacycle with the ditungsten unit.

The title compound, Rh2(O2CCF3)4, without any exogenous axial ligands, has been obtained in crystalline form by sublimation. Its crystal structure has been determined: space group P 1 with α = 5.2499(5), b = 8.491(2), c = 9.172(2) A , α = 88.80(2), β = 88.53(1), γ = 76.43(1)°, V = 397.3(1) A 3 , Z = 1 . The molecules are linked by axially ligating each other to form infinite chains. The Rh-Rh distance is 2.3813 (8) A. The volatility of Rh2(O2CCF3)4 should allow spectrospcopic study of the isolated molecules and therefore the electronic structure has been treated by the SCF-Xα-SW method. The level ordering and composition show significant differences from those of Rh2(O2CH)2, although in both molecules there is a strong Rh-Rh σ bond. Ionizatio potential have been estimated by the transition state method.