New acylhydridorhodium(III) complexes containing terdentate PNN ligands from the reaction of diolefinic rhodium(I) complexes with o-(diphenylphosphino)benzaldehyde in the presence of chelating amino ligands

[{Rh(cod)Cl}₂] (cod=1,5-cyclooctadiene) reacts with o-(diphenylphosphino)benzaldehyde (PPh₂(o-C₆H₄CHO)) (Rh:P=1:1) in the presence of aromatic diamines or 8-aminoquinoline (NN) to give acylhydride [Rh(Cl)(H){PPh₂(o-C₆H₄CO)}(NN)] species. The oxidative addition of PPh₂(o-C₆H₄CHO) in the presence of (NN) and PPh₃ gives cationic species [Rh(H){PPh₂(o-C₆H₄CO)} (PPh₃)(NN)]⁺ containing mutually trans phosphorus atoms. When (NN)=8-aminoquinoline, a mixture of two isomers is obtained. These isomers differ in the nitrogen cis to the hydride, amino or quinolinic. By using Rh:PPh₂(o-C₆H₄CHO)=1:2 stoichiometric ratios, oxidative addition of one PPh₂(o-C₆H₄CHO) and P-coordination of another PPh₂(o-C₆H₄CHO) occurs. The aldehyde group undergoes then a condensation reaction with the coordinated amine to afford new PNN terdentate ligands, phosphine-amino-imine when (NN)=diamine or phosphine-diimine when (NN)=8-aminoquinoline. These reactions give selectively the corresponding complexes [Rh(H){PPh₂(o-C₆H₄CO)}(PNN)]⁺ containing trans phosphorus atoms and the hydride cis to the new imino group. X-ray diffraction studies of the PNN complexes are reported.     

Novel palladium(II) and platinum(II) complexes of biocidal benzisothiazolinone (Bit); X-ray crystal structures of co-crystallised Bit/BitO and cis-Pd(en)(Bit−1H)2·H2O

Reaction of benzisothiazolinone (Bit), a well-known biocide, with the Pd(II) and Pt(II) am(m)ine precursors cis-[Pd(en)(H₂O)₂](NO₃)₂ and cis-[Pt(NH₃)₂(H₂O)₂](NO₃)₂ yielded cis-Pd(en)(Bit_−1H)₂ and cis-Pt(NH₃)₂(Bit_−1H)₂, respectively. Bit is bound to the metal centres in both cases through the deprotonated isothiazolinone N. The crystal structures of a Bit/BitO co-crystal and cis-Pd(en)(Bit_−1H)₂·H₂O are also described.     

Novel p-tolylimido rhenium(V) complexes incorporating quinoline-2-carboxylate ion - Synthesis, X-ray studies, spectroscopic characterization and DFT calculations

Novel p-tolylimido rhenium(V) complexes trans-[Re(p-NC₆H₄CH₃)X₂(quin-2-COO)(PPh₃)] and cis-[Re(p-NC₆H₄CH₃)X₂(quin-2-COO)(PPh₃)]·MeCN have been obtained in the reactions of [Re(p-NC₆H₄CH₃)X₃(PPh₃)₂] (X = Cl, Br) with quinoline-2-carboxylic acid. The compounds were identified by elemental analysis IR, UV-Vis spectroscopy and X-ray crystallography. The electronic structures of trans- and cis-halide isomers of [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] have been calculated with the density functional theory (DFT) method. Additional information about binding in the compounds [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] with cis- and trans-halide arrangement has been obtained by NBO analysis. The electronic spectra of trans and cis isomers of [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.     

Rhodium(III) cis-dihydrido complexes with 3,6-bis(2′-pyridyl)pyridazine (dppn) and bidiazines. Crystal and molecular structure of [Rh(H)2(dppn)(PPh3)2]PF6· CH2Cl2

The acetone complex [Rh(H)₂(acetone)₂(PPh₃)₂]- PF₆ reacts with bidiazines and 3,6-bis(2′-pyridyl)- pyridazine (dppn) giving the air stable cis-dihydrido rhodium(III) [Rh(H)₂(L)(PPh₃)₂]PF₆ complexes. The structure of the dichloromethane solvate of [Rh(H)₂(dppn)(PPh₃)₂]PF₆ has been determined by X-ray crystal structure analysis. Crystals are monoclinic, space group P2₁/a, with a = 18.629(6), b = 15.339(5), c = 17.146(5) Å, β = 101.02(3)° and Z = 4. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by block-matrix least-squares to R = 0.076 for 6225 observed reflections. In the structure discrete [Rh(H)₂(dppn)(PPh₃)₂]⁺ cationic complexes, PF₆⁻ anions and dichloromethane solvent molecules are present. The Rh atom is octahedrally surrounded by two cis hydride ligands and by two cis nitrogen atoms from a dppn molecule acting as a bidentate chelating ligand through two neighbouring pyridyl and pyridazinyl nitrogen atoms. Two P atoms from PPh₃, ligands in trans apical positions complete to octahedral the coordination of Rh.     

Kinetic studies on the reactions of HCl with trans-[MoL(CNPh)(Ph2PCH2CH2PPh2)2] (L=N2, H2 or CO)

The kinetics of the reactions between anhydrous HCl and trans-[MoL(CNPh)(Ph₂PCH₂CH₂PPh₂)₂] (L=CO, N₂ or H₂) have been studied in thf at 25.0 °C. When L=CO, the product is [MoH(CO)(CNPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺, and when L=H₂ or N₂ the product is trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. Using stopped-flow spectrophotometry reveals that the protonation chemistry of trans-[MoL(CNPh)(Ph₂PCH₂CH₂PPh₂)₂] is complicated. It is proposed that in all cases protonation occurs initially at the nitrogen atom of the isonitrile ligand to form trans-[MoL(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺. Only when L=N₂ is this single protonation sufficient to labilise L to dissociation, and subsequent binding of Cl⁻ gives trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. At high concentrations of HCl a second protonation occurs which inhibits the substitution. It is proposed that this second proton binds to the dinitrogen ligand. When L=CO or H₂, a second protonation is also observed but in these cases the second protonation is proposed to occur at the carbon atom of the aminocarbyne ligand, generating trans-[MoL(CHNHPh)(Ph₂PCH₂CH₂PPh₂)₂]²⁺. Addition of the second proton labilises the trans-H₂ to dissociation, and subsequent rapid binding of Cl⁻ and dissociation of a proton yields the product trans-[MoCl(CNHPh)(Ph₂PCH₂CH₂PPh₂)₂]. Dissociation of L=CO does not occur from trans-[Mo(CO)(CHNHPh)(Ph₂PCH₂CH₂PPh₂)₂]²⁺, but rather migration of the proton from carbon to molybdenum, and dissociation of the other proton produces [MoH(CO)(CNPh)(Ph₂PCH₂CH₂PPh₂)₂]⁺.     

Optically active iridium complexes with cyclopentadienyl-phosphine ligands: synthesis and oxidative addition of methyl iodide

The dimer [Ir(μ-Cl)(C₈H₁₄)₂]₂ reacts with the ligands (S)-(C₅H₄CH₂CH(Ph)PPh₂)Li and (R)-(C₅H₄CH(Cy)CH₂PPh₂)Li to give (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(C₈H₁₄)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(C₈H₁₄)], which upon treatment with CH₃I at room temperature afford the cationic iridium(III) compounds (S,S_Ir)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(C₈H₁₄)][I] as a single diastereomer, and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(C₈H₁₄)][I] as a 9:1 mixture of two diastereomers. If the oxidative addition reaction is performed at reflux in methylene chloride, the starting complexes convert to the neutral compounds (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(I)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(I)] as 1.6:1 and 3.3:1 mixtures of diastereoisomers, respectively. Carbonyl iridium complexes are synthesized by reacting [IrCl(CO)(PPh₃)₂] with the ligands to afford (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CO)] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CO)]. They give upon treatment with CH₃I the cationic species (S)-[Ir(η⁵-C₅H₄CH₂CH(Ph)PPh₂-κP)(CH₃)(CO)][I] and (R)-[Ir(η⁵-C₅H₄CH(Cy)CH₂PPh₂-κP)(CH₃)(CO)][I] as 1.6:1 and 3:1 mixture of diastereomers, respectively. No migratory-insertion of the methyl group into the carbonyl-metal bond has been observed even after prolonged heating.     

Platinum(II) complexes with aryl tellurols and diaryl ditellurides: Syntheses and spectral investigations

Arytellurol complexes [PtCl(TeAr)(PPh₃)₂] (I) and [Pt(TeAr)₂(PPh₃)₂] (II) are readily obtained from cis-[PtCl₂(PPh)₃)₂] and NaTeAr (Ar = C₆H₅, 4-CH₃OC₆H₄ and 4-CH₃CH₂OC₆H₄) in ethanolbenzene at room temperature. ³¹P NMR spectra of (I) and (II) indicate their trans configuration in solution. Metathetical reactions between I (Ar = 4-CH₃OC₆H₄) and NaX (X = I, Br, SCN) occur in methanol to give [Pt(X)(TeC₆H₄OCH₃-4)(PPh₃)₂]. ¹H NMR shows that equimolar proportions of NaTeC₆H₅, NaTeC₆H₄OCH₂CH₃-4 and cis-[PtCl₂(PPh₃)₂] give a mixture of three complexes: II, Ar = C₆H₅; II, Ar = 4-CH₃CH₂OC₆H₄; and [Pt(TeC₆H₅)(TeC₆H₄OCH₂CH₃-4)(PPh₃)₂]. Polymeric complexes [PtCl(TeAr)]_n (III) and [Pt(TeAr)₂]_n (IV) result from reaction between K₂[PtCl₄] and NaTeAr in aqueaous ethanol. They react with excess of PPh₃ in CDCl₃ to yield monomeric complexes I and II respectively which were characterized in situ by ¹H and ³¹P NMR of the reaction mixtures. IR spectra indicate the presence of bridging chloride ligands in III. An alternating chloride and tellurol bridged chain structure for III and a tellurol bridged for IV have been proposed. Reaction between equimolar amounts of III and PPh₃ in dichloromethane yielded a tellurol bridged dimeric complex [PtCl(μ-TeAr)(PPh₃)]₂ (V) with terminal chloride ligand as suggested by IR study. Ethanolic solutions of diarylditellurides also react readily with an aqueous solution of K₂[PtCl₄] at 10 °C to give complexes for which the structure trans-[PtCl₂(ArTeTeAr)₂] (VI) is suggested from their elemental analyses, IR, Raman (in one case only), ¹H, ¹²⁵Te (in one case only), and ¹⁹⁵Pt NMR spectra and reactions with triphenylphosphine which liberated free ditellurides. At 40 °C or above the same ditellurides form polymeric complexes III with K₂[PtCl₄] in aquaeous ethanol.     

Facile anaerobic oxidative dehydrogenation promoted by bases: The case of copper-2,4-dihydro-1H-benzo[d][1,3]oxazine complexes

Two new 2,4-dihydro-1H-benzo[d][1,3]oxazines (L₁ and L₂) were prepared by condensation of 2-quinolinecarboxaldehyde and 2-amino-benzyl alcohols and tested as N,N’-bidentate ligands toward CuCl₂. Treatment of the resulting copper(II) derivatives with Et₃N promoted an oxidative dehydrogenation yielding the corresponding copper(I) [Cu(L-ox)Cl] complexes, 2, (L-ox = 4H-benzo[d][1,3]oxazine). The [Cu(L₂-ox)Cl] species, 2b, was characterized by single crystal X-ray diffraction, showing a trigonal geometry at the metal center and reacted with PPh₃ and CO, affording [Cu(L₂-ox)(PPh₃)Cl], 4b, and [Cu(L₂-ox)(CO)Cl], 6b, respectively. The latter species, stable in the solid state, was structurally characterized by diffraction methods and showed tetrahedral coordination of the Cu(I) ion.     

Kinetics study of the substitution reaction of fac-[Fe(CN)2(CO)3I] with PPh3

Substitution reaction of fac-[Fe^II(CN)₂(CO)₃I]⁻ with triphenylphosphine (PPh₃) produced mono phosphine substituted complex cis-cis-[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻. Crystal structure of the product showed that carbonyl positioned trans- to iodide was replaced by PPh₃. The substitution reaction was monitored by quantitative infrared spectroscopic method, and the rate law for the substitution reaction was determined to be rate = k[[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻][PPh₃]. Transition state enthalpy and entropy changes were obtained from Eyring equation k = (k_BT/h)exp(−ΔH^≠/RT + ΔS^≠/R) with ΔH^≠ = 119(4) kJ mol⁻¹ and ΔS^≠ = 102(10) J mol⁻¹ K⁻¹. Positive transition state entropy change suggests that the substitution reaction went through a dissociative pathway.     

The structure of 1,3-diphenyl-1,3-propandionatobis(triphenylantimony)diphenylrhodium(III)dibenzene

1,3-Diphenyl-1,3-propandionatobis(triphenylantimony)diphenylrhodium(III)dibenzene, [Rh(DPD)(SbPh₃)₂Ph₂]·2(C₆H₆) has been isolated as the product of the reaction between the Rh(I) complex 1,3-diphenyl-1,3-propandionatodicarbonylrhodium(I), [Rh(DPD)(CO)₂], and triphenylantimony in acetone and in n-hexane medium. The crystal and molecular structure was determined from single crystal X-ray diffractometer data. The unit cell is triclinic with a = 19.083, b = 13.167, c = 13.536 Å, α = 81.81°, β = 111.59°, γ = 100.49°, Z = 2 and space group P_$\text{1}$. The structure was refined to a R-value of 0.079 for 6637 contributing reflections. The coordination polyhedron can be described as a slightly distorted octahedron in which the Rh-atom is coordinated by two phenyl groups, two oxygen atoms of a chelate ring, which are in cis position to one another, and two antimony-atoms of the two SbPh₃ ligands, which are in trans positions.     

Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn₂(Hphth)₂(phen)₄] · 2Hphth · 6H₂O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)₂(H₂O)] · 2.5H₂O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H₂O)₂]_n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H₂O)₂]_n · 2nH₂O (4) (H₂phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn-syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]_n · nH₂O (5) with dehydration in warm solution.     

Directing iridium-catalyzed C-C bond formation by selection of the ancillary ligands: Polymerization and cyclotrimerization of alkynes

The ability of organoiridium derivatives of catalyzing oligomerization and polymerization of terminal alkynes is markedly influenced by the nature of non-participative ligands coordinated to the metal. The dimeric species [Ir(cod)Cl]₂ and [Ir(cod)(OMe)]₂ (cod = 1,5-cyclooctadiene) as well as the phosphine complexes HIr(cod)(PR₃)₂ (PR₃ = PPh₃, P(p-MeOC₆H₄)₃, P(o-MeOC₆H₄)Ph₂, PCyPh₂) catalyze the polymerization reaction, whereas the diphosphine derivatives HIr(cod)(P-P) (P-P = Ph₂P(CH₂)_nPPh₂ (n = 1-4), o-C₆H₄(PPh₂)₂) promote the regioselective formation of 1,2,4-trisubstituted benzenes. On the other hand, the iridium complexes with nitrogen chelating ligands Ir(cod)(N-N)X and Ir(hd)(N-N)X (hd = 1,5-hexadiene; N-N = 1,10-phenanthroline and substituted derivatives; X = halogen) catalyze alkynes polymerization. In most cases one catalytic reaction predominates over the other possible routes, so that polymerization often takes place in the absence of oligomerization side reactions, and conversely cyclotrimerization is rarely accompanied by formation of either polyene or dimers.     

Synthesis and characterization of [Pt(COD)Cl(NO3)] and [Pt(COD)(NO3)2] and the use of [Pt(COD)Clx(NO3)2−x] in the preparation of cis[Pt(PPh3)2Clx(NO3)2−x] (x=0, 1, 2) and [Pt(PPh3)3L](NO3) (L=Cl,NO3)

[Pt(COD)Cl₂] (COD=1,5-cyclooctadiene) is a versatile starting material for the synthesis of Pt(II) compounds. The preparations of the new compounds [Pt(COD)Cl(NO₃)], [Pt(COD)(NO₃)₂] and [Pt(PPh₃)₃(NO₃)](NO₃) and also of the known compounds cis[Pt(PPh₃)₂Cl₂], cis [Pt(PPh₃)₂Cl(NO₃)], cis[Pt(PPh₃)₂(NO₃)₂] and [Pt(PPh₃)₃Cl](NO₃)are reported. The compounds are characterized by elemental analysis, ³¹P{¹H} NMR spectroscopy and IR spectroscopy.     

Quantification of cis and trans influences in [PtX(PPh3)3] complexes. A P NMR study

In [PtX(PPh₃)₃]⁺ complexes (X = F, Cl, Br, I, AcO, NO₃, NO₂, H, Me) the mutual cis and trans influences of the PPh₃ groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P_(cis) and P_(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh₃)₃](BF₄) (2), [PtI(PPh₃)₃](BF₄) (3), [Pt(AcO)(PPh₃)₃](BF₄) (4), [Pt(NO₃)(PPh₃)₃](BF₄) (5), and the two isomers [Pt(NO₂-O)(PPh₃)₃](BF₄) (6a) and [Pt(NO₂-N)(PPh₃)₃](BF₄) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH₂Cl₂·0.25C₃H₆O have been determined. From the ¹J_PtP values of all compounds we have deduced the series: I > Br > Cl > NO₃ > ONO > F > AcO > NO₂ > H > Me (cis influence) and Me > H > NO₂ > AcO > I > ONO > Br > Cl > F > NO₃ (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh₃)₂] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.     

Quantifying the electronic cis effect of phosphine, arsine and stibine ligands by use of rhodium(I) Vaska-type complexes

The cis effects of phosphine, arsine and stibine ligands have been evaluated by measuring the IR stretching frequency in dichloromethane of the carbonyl ligand in a series of Rh(I) Vaska-type complexes, trans-[RhCl(CO)(L)₂]. These data were correlated with those obtained by Tolman for the electronic trans influences in the [Ni(L)(CO)₃] complexes. The electronic contribution, χ_Fc, of ferrocenyl was determined as 0.8 from these plots by evaluating PPh₂Fc as ligand. In order to accommodate arsine and stibine ligands an additional correction term, to compensate for differences in the donor atom, was added to Tolman’s equation for calculation of the Tolman electronic parameter of phosphine ligands. In the resulting equation: ν(CO_Ni)=2056.1+∑_i=1³χ_i+C_L values for C_L of C_P=0, C_As=−1.5 and C_Sb=−3.1 are suggested for phosphine, arsine and stibine ligands, respectively. The crystal and molecular structures of trans-[RhCl(CO)(PPh₂Fc)₂] · 2C₆H₆, trans-[RhCl(CO){P(NMe₂)₃}₂] and trans-[RhCl(CO)(AsPh₃)₂] are reported. The Tolman cone angles for PPh₂Fc and P(NMe₂)₃ were determined as 169° and 166°, while the effective cone angles for PPh₂Fc, P(NMe₂)₃ and AsPh₃ were determined as 171°, 168° and 147°, respectively.     

Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid

The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]·2CHCl₃ shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh₃ ligands. This allows the O₃P-CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.     

Ruthenium mediated C-H activation of benzaldehyde thiosemicarbazones: Synthesis, structure and, spectral and electrochemical properties of the resulting complexes

Reaction of five 4R-benzaldehyde thiosemicarbazones (R = OCH₃, CH₃, H, Cl and NO₂) with [Ru(PPh₃)₃(CO)(H)Cl] in refluxing methanol in the presence of a base (NEt₃) affords complexes of two different types, viz. 1-R and 2-R. In the 1-R complexes the thiosemicarbazone is coordinated to ruthenium as a dianionic tridentate C,N,S-donor via C-H bond activation. Two triphenylphosphines and a carbonyl are also coordinated to ruthenium. The tricoordinated thiosemicarbazone ligand is sharing the same equatorial plane with ruthenium and the carbonyl, and the PPh₃ ligands are mutually trans. In the 2-R complexes the thiosemicarbazone ligand is coordinated to ruthenium as a monoanionic bidentate N,S-donor forming a four-membered chelate ring with a bite angle of 63.91(11)°. Two triphenylphosphines, a carbonyl and a hydride are also coordinated to ruthenium. The coordinated thiosemicarbazone ligand, carbonyl and hydride constitute one equatorial plane with the metal at the center, where the carbonyl is trans to the coordinated nitrogen of the thiosemicarbazone and the hydride is trans to the sulfur. The two triphenylphosphines are trans. Structures of the 1-CH₃ and 2-CH₃ complexes have been determined by X-ray crystallography. All the complexes show intense transitions in the visible region, which are assigned, based on DFT calculations, to transitions within orbitals of the thiosemicarbazone ligand. Cyclic voltammetry on the complexes shows two oxidations of the coordinated thiosemicarbazone on the positive side of SCE and a reduction of the same ligand on the negative side.     

‘Synthetic prospecting’ using an electrospray ionisation mass spectrometry directed survey of the alkylation and arylation chemistry of [Pt2(μ-S)2(PPh3)4]

Electrospray ionisation mass spectrometry (ESI-MS) has been used as an analytical tool in a wide-ranging scoping study of the alkylation and arylation reactions of [Pt₂(μ-S)₂(PPh₃)₄]. From these experiments, the factors that influence the formation of different product species - formed by mono- or di-alkylation - are determined. If the alkylating agent is an alkyl chloride or sulfate, monoalkylation followed by dialkylation of the two sulfido groups occurs, dependent on the alkylating power of the reagent used. For example, n-butyl chloride gives solely [Pt₂(μ-S)(μ-SBu)(PPh₃)₄]⁺ while dimethyl sulfate gives [Pt₂(μ-SMe)₂(PPh₃)₄]²⁺. This species, previously unisolated is stable in the absence of good nucleophiles, but the addition of potassium iodide results in rapid conversion to [Pt₂(μ-SMe)₂(PPh₃)₃I]⁺. This iodo complex is also observed from the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess MeI, after the initial formation of mono- and di-methylated species. In these reactions, the iodide presumably displaces a phosphine ligand, which is then quaternised by excess alkylating agent. Changing the alkylating agent to a longer chain alkyl iodide or methyl bromide decreases the rate of alkylation of the sulfide in the initially formed [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺. Mixed-thiolate species of the type [Pt₂(μ-SMe)(μ-SR)(PPh₃)₄]²⁺ are easily generated by reaction of [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ with excess Me₂SO₄ and is also dependent on the avoidance of nucleophiles. Reactions towards α,ω-dialkylating agents are surveyed; the chain length is found to have a dramatic effect on the rate of the second intramolecular cyclisation process, illustrated by a competitive reactivity study involving a mixture of Br(CH₂)₄Br and Br(CH₂)₅Br; on completion of the reaction the former gives [Pt₂{μ-S(CH₂)₄S}(PPh₃)₄]²⁺ while the latter predominantly gives monoalkylated[Pt₂(μ-S){μ-S(CH₂)₅Br}(PPh₃)₄]⁺. The reactivity of o- and p-dihaloxylenes has been explored, with the reaction with p-BrCH₂C₆H₄CH₂Br giving the bridged species [(PPh₃)₄Pt₂(μ-S)(μ-SCH₂C₆H₄CH₂S)(μ-S)Pt₂(PPh₃)₄]²⁺. Arylation reactions of [Pt₂(μ-S)₂(PPh₃)₄] with halobenzenes and 2-bromoheterocyclic compounds (pyridine, thiophene) are also described.     

Phosphane effects on formation and reactivity of [Ru(L)(PR3)(`N2Me2S2')] complexes with L=N2, N2H4, NH3, and CO

Metal-sulfur complex fragments, to which small molecules like N₂, N₂H₂, N₂H₄, NH₃, or CO can bind, are desirable model compounds concerning enzymatic N₂ fixation.This paper reports on the effects of the phosphane co-ligand on formation and reactivity of [Ru(L)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [`N₂Me₂S₂'²⁻=1,2-ethanediamine-N,N^′-dimethyl-N,N^′-bis(2-benzenethiolate)(2−)] complexes with nitrogenase relevant ligands, especially N₂, N₂H₄, NH₃, and CO.Treatment of [Ru(NCCH₃)₄Cl₂] with Li₂`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>', excessive LiOMe, bulky PPh<sub>3</sub> or PCy<sub>3</sub>, respectively, led to the formation of two series of [Ru(L)(PR<sub>3</sub>)(`N₂Me₂S₂')] complexes [for R=Ph: 1b, 1c (L=NCCH₃), 6b (L=N₂H₄), 7b (L=N₂), 8b_1-3 (L=CO), 9b (L=NH₃); for R=Cy: 1a (L=NCCH₃), 6a (L=N₂H₄), 7a (L=N₂), 8a (L=CO), 9a (L=NH₃)]. While the use of PPh₃ (θ=145°) yielded cis,trans and cis,cis isomers of [Ru(NCCH₃)(PPh₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] (1b, 1c), no isomer formation was observed with the bulkier phosphane PCy<sub>3</sub> (θ=170°). Sterically less demanding phosphanes (θ=118-132°) afforded bisphosphane complexes [Ru(PR<sub>3</sub>)<sub>2</sub>(`N₂Me₂S₂')] [2d (R=Me), 2e (R=Et), 2f (R=nPr), and 2g (R=nBu)], which were practically inert and could only be converted in two cases and under drastic reaction conditions into the CO complexes [Ru(CO)(PR₃)(`N<sub>2</sub>Me<sub>2</sub>S<sub>2</sub>')] [4e (R=Et), 4f (R=nPr)]. The chelating bidentate phosphane dppe (bisdiphenylphosphanoethane) yielded exclusively the mononuclear complex [Ru(dppe)(`N₂Me₂S₂')] (3).