Anionic Bidentate Ligand Research Articles

Synthesis, spectroscopy and structure of cis,cis,trans:N,N;P,P;S,S-[bis(triphenylphosphine)] [bis(pyrimidine-2-thiolato)]ruthenium(II)

Reaction of RuCl2(PPh3)3with pyrimidine-2-thione (HpymS) in a 1:2 mol ratio in dry benzene in the presence of triethylamine as base yielded a complex of stoichiometry [Ru(pymS)2(PPh3)2] (1). This has been characterized using analytical data and IR, 1H, 13C and 31P NMR spectroscopy. 1H NMR confirmed the deprotonation of HpymS. 31P NMR spectra showed a single peak confirming equivalent P atoms. Complex 1 crystallizes in space group Pī and HpymS acts as a η2-N,S-deprotonated bidentate anionic ligand. The coordination geometry around the Ru center is distorted octahedral with cis dispositions of P atoms, as well as two N atoms of pymS– and trans S atoms of pymS–. Important bond distances and angles are: Ru–N, 2.119(2), 2.106(2); Ru–S, 2.4256(8), 2.4413(8); and Ru–P, 2.3266(7), 2.3167(7) Å; P(2)–Ru(1)–P(1), 96.07(3); N(21)–Ru(1)–N(11), 83.46(9); and S(1)–Ru(1)–S(2), 153.02(3)°.

A new family of pyrazolyl-based anionic bidentate ligands and crystal structure of bis( N-phenyl-2-pyrazolyl-1-carboximidothioato)copper(II)

Three new N,S-donor bidentate pyrazolyl-based ligands abbreviated as [PhNCSPz] −, 1, [PhNCSPz Me2] −, 2, and [PhNCSPz Ph2] −, 3, have been synthesized in THF by direct mixing of phenylisothiocyanide with suspension of appropriate sodium-pyrazolate salts and characterized by the common spectroscopic and analytical methods. The Cu(II) complexes of these anionic chelate ligands have been characterized and the crystal structure of Cu(PhNCSPz) 2, 4, has been determined. The space group of complex is P2 1 c, with a = 5.9313(3), b = 21.206(1) Å, c = 8.0667(4) Å, β = 103.822(1)°.

Polymer Complexes: supramolecular assemblies and structures of poly[N‐(2′‐pyridyl)propenamide] complexes

AbstractA number of new polymer complexes of palladium(II), platinum(II) and copper(II) containing homopolymer (N‐(2′‐pyridyl)propenamide; APH) and various anions (Cl−, Br−, I− or NO3−) have been synthesized and characterized by elemental analyses, magnetic susceptibility, electron paramagnetic resonance, IR and reflectance spectral measurements. The homopolymer shows three types of coordination behavior. In the mononuclear polymer complexes 1–6 and 9 it acts as a neutral bidentate ligand chelated through the pyridine‐nitrogen and amide‐oxygen atoms, whereas in the square‐planar [Pd(APH)2X2] (X = Cl, Br) unidentate APH is coordinated through the pyridine‐nitrogen atom alone. Under alkaline conditions APH is deprotonated in the presence of palladium(II) to form [Pd(AP)2] (10), AP being an anionic bidentate ligand and chelating through the pyridine‐nitrogen and amide‐oxygen atoms. The poly‐chelates are of 1:1 and 1:3 (metal:homopolymer) stoichiometry and exhibit six‐coordination. The polymer complexes of stoichiometric [(APH)2CuX2] contain square planar (APH)2 Cu2+ units and the anions X− are in the axial positions, giving distorted octahedral configurations. From the electron paramagnetic resonance and spectral data, the orbital reduction factors were calculated. Copyright © 2004 John Wiley & Sons, Ltd.

Modification of Metal Alkoxide Precursors by Organofunctional Bidentate Ligands: Chemical Problems and Opportunities for Materials Syntheses

ABSTRACTBidentate ligands are potentially useful to modify metal alkoxides precursors for sol-gel processing. However, anionic bidentate ligands are needed to get a strong coordination, while diamines as neutral bidentate ligand form coordination polymers [Ti2(OR)8(diamine)2]∞ when reacted with Ti(OR)4. The Lewis acidity of metal alkoxides may cause organic side reactions. The first is the formation of ester and water in the reaction with carboxylic acids, and therefore carboxylate-substituted metal oxide clusters of the general composition MnOx(OH/OR)y(OOCR)z are obtained instead of substituted monomeric precursors. The second side reaction discussed is the cleavage of β-diketones by metal alkoxides. Despite this side reaction, 3-acetyl-6-trimethoxy-silyl-hexane-2-one is a useful compound to prepare single-source precursos for silica/metal oxide composites.

Synthesis, spectroscopic investigation and X-ray structure of mononuclear and binuclear oxo complexes of rhenium(V) with pyrazolato ligands

The [{Re(O)Cl(PPh3)}2(μ-O)(μ-N2C3H3)2] (1), [{Re(O)Br(PPh3)}2(μ-O)(μ-N2C3H3)2] (2), [ReOCl2{η2-N2C3H3CMe2O}(PPh3)] (3) and [ReOBr2{η2-N2C3H3CMe2O}(PPh3)] (4) complexes have been synthesized by reacting [ReOX3(PPh3)2] with an excess of pyrazole under different conditions. The rhenium(V) centers of (1) and (2) are linked through two bridging pyrazolato anions and an oxo group. The rhenium(V) atoms in mononuclear complexes (3) and (4) are six coordinated in an octahedral environment with a trans arrangement of the oxo group and oxygen atom of anionic bidentate ligand C3H3N2C(Me)2O− formed in the reaction of pyrazole and Me2CO.

Electrochemical Synthesis of Cobalt Complexes with 4‐Methyl‐ N ‐(2‐pyridylmethyl)benzenesulfonamide (HL) − Crystal Structures of HL, [Co II L 2 ] and [Co III L 2 L o ] [L o = {HNC(CH 3 )} 2 C(CN)

Electrochemical oxidation of cobalt in a solution of 4-methyl-N-(2-pyridylmethyl)benzenesulfonamide (HL, 1) in acetonitrile afforded the compounds [CoIIL2] (2) or [CoIIIL2Lo] (3). When 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) was added to the electrolytic phase, [CoIIL2bipy] (4) and [CoIIL2phen] (5) were obtained. The crystal structures of HL (1), [CoIIL2] (2) and [CoIIIL2Lo] (3) were determined by X-ray diffraction techniques. The compound [CoIIL2] is mononuclear and has a distorted tetrahedral [CoN4] geometry, with each amide ligand acting as an anionic (NamideNpy) bidentate ligand. In the monomeric complex [CoIIIL2Lo] the cobalt atom is in a distorted octahedral [CoN6] environment defined by the amide and pyridyl nitrogen atoms of two L− anionic ligands and the two nitrogen atoms of the NH groups of a new anionic ligand Lo, which is formed by trimerisation of three acetonitrile molecules in the electrolytic cell. The electronic, IR and FAB spectra of the compounds are discussed. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Reactions of the cationic diruthenium carbonyl complex [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)] + with bidentate ligands; intramolecularly assisted stereospecific synthesis via the second-sphere face-to-face π–π stacking interactions

The reactions of the diruthenium carbonyl complexes [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)]X (X=BF 4 − ( 1a) or PF 6 − ( 1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-(L,L)) 2]X n ((L,L)=acetate (O 2CMe), 2,2′-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)] + either migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru 2(μ-dppm) 2(CO) 4(μ,η 2-O 2CMe)] + ( 1) with 2,2′-bipyridine produces [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe) 2] ( 2), [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe)(η 2-bpy)] + ( 3), and [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-bpy) 2] 2+ ( 4). Alternatively compound 2 can be prepared from the reaction of 1a with MeCO 2H–Et 3N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone–Et 3N produces [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-O 2CMe)(η 2-acac)] ( 5) and [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-acac) 2] ( 6). Compound 2 can also react with acetylacetone–Et 3N to produce 6. Surprisingly [Ru 2(μ-dppm) 2(μ-CO) 2(η 2-quin) 2] ( 7) was obtained stereospecifically as the only one product from the reaction of 1b with 8-quinolinol–Et 3N. The structure of 7 has been established by X-ray crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere π–π face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV–vis spectrum.

Synthesis, crystal structure and biological activity of thiophene-2-carboxaldehyde thiosemicarbazone and its tin complexes

Thiophene-2-carboxaldehyde thiosemicarbazone, C 4H 3S–CHN–NH–C(S)NH 2 (tctscH) obtained by the condensation reaction of thiophene-2-carboxaldehyde with thiosemicarbazide forms SnPh 2Cl(tctsc), 1 and SnCl 2(tctsc) 2, 2 with SnPh 2Cl 2 and SnPhCl 3 in 1:1 and 1:2 tin:ligand molar ratios, respectively. The crystal structure determination shows that in both 1 and 2, tctscH is deprotonated and functions as an anionic bidentate ligand, co-ordinating to the tin atom through its azomethine- N and thiol- S atoms. The geometry about the tin atom for complex 1 is distorted trigonal bipyramidal whereas for complex 2 is distorted octahedral. Note that dephenylation occurs during the formation of complex 2. Fungitoxicity and cytotoxicity of the two tin complexes and tctscH have been evaluated and the biological activity is more remarkable in complex 1 in comparison to the other.

Synthesis and Reactivity of some Aromatic Sulfides Substituted by an Ortho-Phosphonyl Group

As phosphorus-based members of the biologically relevant thiosalicylic acid, monoesters of ortho-sulfinylated phenylphosphonic acids such as 3 and 4 (series a, R1=Me; b, R22-C6H4C02H) are of special interest. They might act both as potential sources of new anionic bidentate ligands for the synthesis of cisplatin analogues[1] and as suitable precursors of phosphorus-containing endocyclic sulfoximides and hypervalent organo-sulfur species. We have therefore undertaken the synthesis of these compounds. The starting phenylphosphonic acid diisopropylesters 1 were formed by using a LDA-induced thiophosphate-mercaptophosphonate rearrangement[2] described earlier and converted into their dimethyl counterpans 2 by means of a trans-silylation procedure followed by alkylation. We have now performed the selective half-hydrolysis of phosphonic acid diesters 1.2 and sulfoxidation of the resulting monoesters.

A novel palladium complex catalyst for carbonylation of alkynes under mild conditions

Carbonylation of alkynes has been carried out using a catalyst system consisting of Pd(OAc)2, a monophosphine, p‐toluene sulphonic acid and semilabile anionic bidentate ligands such as pyridine or piperidine carboxylic acids. Turnover frequencies (TOF) upto 3500 h−1 and 98% selectivity to 2‐substituted 2‐propenoic acid/ester have been achieved under mild CO pressures of 1–3 atm at 373 K.

Phosphaalkyne Hydrometalation: Synthesis and Reactivity of the Complexes [Ru(PCHCMe3)Cl(CA)(PPh3)2] (A = O, S)

The reaction of [RuHCl(CO)(PPh3)3] (1a) with P⋮CCMe3 results in the formation of the phosphaalkenyl complex [Ru(PCHCMe3)Cl(CO)(PPh3)2] (2a). Being coordinatively unsaturated, 2a reacts reversibly with CO to provide [Ru(PCHCMe3)Cl(CO)2(PPh3)2] (3) and with isonitriles (CNR) to provide [Ru(PCHCMe3)Cl(CNR)(CO)(PPh3)2] [R = CMe3 (4a), C6H3Me2-2,6 (4b)]. With an excess of CNCMe3, the salt [Ru(PCHCMe3)(CNR)2(CO)(PPh3)2]Cl 5(Cl) is obtained. The anionic bidentate ligand K[H2B(bta)2] (bta = benzotriazolyl) reacts with 2a via chloride displacement to provide [Ru(PCHCMe3){H2B(bta)2}(CO)(PPh3)2] (6) while the facially tridentate macrocycle 1,4,7-trithiacyclononane ([9]aneS3) provides [Ru(PCHCMe3)(CO)(PPh3)([9]aneS3)]Cl 7(Cl). The thiocarbonyl complex [Ru{PCHCMe3)Cl(CS)(PPh3)2] (2b), obtained from [RuHCl(CS)(PPh3)3] (1b) and P⋮CCMe3, reacts with [Et2NH2][S2CNEt2] or [9]aneS3 to provide [Ru(PCHCMe3)(S2CNEt2)(CS)(PPh3)2] (8) and [Ru(PCHCMe3)(CS)(PPh3)([9]aneS3)]Cl 9(Cl), respectively. The salt 5(Cl) or the neutral comp...

Reaction of Al(tBu)3 with [R2Al{μ-O(CH2)nNMe2}]2: dependence on the extent of intra-molecular Al · · · N coordination

Reaction of Al(tBu)3 with (tBu)3Al[O(H)CH2CH2CH2NMe2] yielded the Lewis acid–base complex [(tBu)2Al{µ-OCH2CH2CH2N(Me)2Al(tBu)3}]2 1. Compound 1 is also formed directly when 2 equivalents of Al(tBu)3 reacts with 1 equivalent of [(tBu)2Al(µ-OCH2CH2CH2NMe2)]2. In contrast, the reaction of 2 equivalents of Al(tBu)3 with 1 equivalent of [Me2Al(µ-OCH2CH2NMe2)]2 yielded Me2Al(µ-OCH2CH2NMe2)Al(tBu)3 2. The molecular structure of compound 2 shows the AlMe2 moiety chelate bound to the anionic bidentate ligand, while the Al(tBu)3 unit is bonded to the anionic terminus of the ligand. The formation of compound 1 is proposed to occur via the tert-butyl analog of compound 2, i.e., (tBu)2Al(µ-OCH2CH2CH2NMe2)Al(tBu)3, which is unstable due to significant tBu· · ·tBu inter-ligand interactions. The implications of the differences in products is discussed with respect to the extent of intra-molecular Al· · ·N coordination in compounds of the general formula [R2Al{µ-O(CH2)nNMe2}]2.

Crystal structures, spectroscopic and nonlinear optical properties of metal complexes of Schiff-base ligands containing nitrogen and sulfur donors

ML2 type CuII chelates with the Schiff base ligands R-C6H4CHNNHC(S)SCH2Ph (R=NMe2 or -OMe) have been prepared and characterized. Spectroscopic data suggest that the Schiff bases act as singly charged anionic bidentate ligands, forming stable neutral metal complexes. Magnetic and e.s.r. data support a square-planar coordination geometry for both complexes. Single crystal X-ray diffraction analysis of the complexes has established that the Schiff base ligand is deprotonated to give the thiol tautomer, coordinated via the thiolato sulfur and β-nitrogen. The geometry around the metal is square-planar with two equivalent Cu-N and Cu-S bonds; the two phenyl rings and the donor atoms are in one plane forming an extensive electronic delocalization system. Third-order optical nonlinearity measurements show that the complexes exhibit fairly large second-order hyperpolarizabilities.

Competing mechanisms in the carbonylation of neutral palladium(II) complexes containing bidentate ligands: theoretical insights

Correlated ab initio calculations identify the rate-determining step in the carbonylation reaction of palladium(II) complexes of mixed bidentate anionic ligands, and supply new evidence for the participation of five-coordinate intermediates and transition structure.

Synthesis and reactivity of coordinatively unsaturated osmium and ruthenium stannyl complexes

Abstract Treatment of MHCl(CO)(PPh 3 ) 3 (MRu, Os) with (CH 2 CH)SnR 3 is a good general route to the coordinatively unsaturated osmium and ruthenium stannyl complexes M(SnR 3 )Cl(CO)(PPh 3 ) 2 ( 1 : MRu, RMe; 2 : MRu, R = n-butyl; 3 : MRu, R = p -tolyl; 4 : MOs, RMe). These coordinatively unsaturated complexes readily add CO and CN- p -tolyl to form the coordinatively saturated compounds M(SnR 3 )Cl(CO)L(PPh 3 ) 2 ( 5 : MRu, RMe, LCO; 6 : M;Ru, R = n-butyl, LCO; 7 : MRu, R = p -tolyl, LCO; 8 : MOs, RMe, LCO; 9 : MRu, RMe, LCN- p -tolyl; 10 : MRu, R = n-butyl, L  CN - p -tolyl; 11 : MOs, RMe, LCN- p -tolyl). In addition, the chloride ligand in Ru(SnR 3 )Cl(CO)(PPh 3 ) 2 proves to be labile and treatment with the potentially bidentate anionic ligands, dimethyldithiocarbamate or diethyldithiocarbamate, affords the coordinatively saturated compounds Ru(SnR 3 )( η 2 -S 2 CNR′ 2 )(CO)(PPh 3 ) 2 ( 12 : RMe, R′ = Me; 13 : RMe, R′ = Et; 14 : R = n-butyl, R′ = Me; 15 : R = p -tolyl, R′ = Me; 16 : R = p -tolyl, R′ = Et). Chloride is also displaced by carboxylates forming the six-coordinate compounds Ru(SnR 3 )( η 2 -O 2 CR′)(CO)(PPh 3 ) 2 ( 17 : RMe, R′ = H; 18 : RMe, R′ = Me; 19 : RMe, R′ = Ph; 20 : R = n-butyl, R′ = Me; 21 : R = p -tolyl, R ′ = Me ). IR and 1 H NMR spectral data for all the new compounds and 31 P and 119 Sn NMR spectral data for selected compounds are reported.

Preparation and reactivity of five-membered phosphonickelocycles

The complexes trans-[[graphic omitted])L][L = PMe2Ph 1a, PEt31b, P(CH2Ph)31c or PPh31d], and [{[graphic omitted])}2] containing the bidentate anionic ligand o-C6H4CH2PPh2(P–C) have been prepared. The molecular structure of 1c has been determined by single-crystal X-ray crystallographic methods: space group P21/c, a= 20.641(6), b= 9.794(3), c= 17.047(5)A, β= 102.05(3)° and Z= 4. Complexes 1 showed a conformational interconversion of the metallocyclic ring. Different amounts of cis and trans isomers were observed in the solutions of [[graphic omitted])L] compounds by NMR spectroscopy, depending on the size of the phosphine and the anionic ligands. With [[graphic omitted]){P(CH2Ph)3}] only the cis product is obtained. The ionic compounds [[graphic omitted])(PMe2Ph)2]BF4 and [[graphic omitted])(MeCN){P(CH2Ph)3}]BF4 were synthesised by reaction of [[graphic omitted]] with 1 equivalent of TIBF4 in the presence of free ligand. The five-co-ordinate compound [[graphic omitted])(PMe2Ph)2] was obtained from 1a and PMe2Ph. The reactivity of the Ni–C bond of compounds 1 in the presence of CO, SO2, CS2, CO2, alkynes and olefins was studied. Acyl or S-sulfinate compounds containing six-membered rings [[graphic omitted]Ph2)L][L = PEt3 or P(CH2Ph)3] and [[graphic omitted]Ph2){P(CH2Ph)3}] were obtained from the reactions with CO and SO2. The reaction with diphenylacetylene or ethyl phenylpropiolate of compounds 1a and 1c gave one isomer of [[graphic omitted]Ph2}L][L = PEt3 or P(CH2Ph)3] and [[graphic omitted]Ph2}{P(CH2Ph)3}], with the alkenyl fragment cis with respect to the substituents of the alkyne. The geometry of the latter was confirmed by single-crystal X-ray structure determination: space group P21/c, a= 11.386(3), b= 14.715(3), c= 26.000(5)A, β= 90.03(4)° and Z= 4. Decomposition products after insertion of ethylene under pressure in 1c and [[graphic omitted]){P(CH2Ph)3}] were also observed. No evidence of insertion reactions was obtained with CS2 and CO2 even under pressure.

Diamine- N,N′-diacetatochromate(III) complexes with oxalate and malonate anions. Crystal structure of (−) 589-[Co(en) 2(C 2O 4)] [formula omitted](−) 546-[Cr(1,3-pdda)(mal)]·H 2O

The uns-cis-[Cr(1,3-pdda)(L)] − complexes (1,3- pdda = 1,3-propanediamine- N,N′-diacetate; L = oxalate or malonate) were prepared and resolved. The corresponding s-cis-[Cr(edda)L] − complexes (edda = ethylenediamine- N,N′-diacetate) have been partially resolved. The infrared absorption and circular dichroism (CD) spectra are reported. Rotational strengths of the uns-cis-[Cr(1,3-pdda)(L)] − complexes decrease with increasing chelate ring size of the bidentate anionic ligands. (−) 589-[Co(en) 2- (C 2O 4)] uns-cis-(−) 546-[Cr(1,3-pdda)(mal)]·H 2O crystallizes in the space group P2 1 of the monoclinic crystal system with a = 7.832(3), b = 14.207(6), c = 10.801(3) Å, β = 98.46(3)° and Z = 2. In the anionic chromium complex, the six-membered diamine ring assumes the stable chair conformation; the equatorial glycinate ring is puckered; and the axial glycinate ring is in the ‘envelope’ conformation. The absolute configuration of the chromium complex ion is ΔΔΔΛ.

Seven-coordinated molybdenum(II) complexes containing carbonyl, triphenylphosphine, and O-donor or S-donor anionic bidentate ligands

A series of seven-coordinate molybdenum(II) complexes containing carbonyl, triphenylphosphine, bromide and/or O-donor and S-donor anionic bidentate ligands have been prepared in high yield. The synthesis involves the reaction of the six-coordinate complex Mo(CO)2(PPh3)2Br2 with the sodium salt of the appropriate ligand, in dichloromethane/methanol solution. The new complexes Mo(CO)2(PPh3)2Br(XOCR) (X = O, R = H, Me, Et, Ph, Cl3C; X = S, R = Me, Ph). Mo(CO)2(PPh3(XOCR)2(X = O, R = H, Me, Et, Ph; X = S, R = Me, Ph), Mo(CO)(PPh3)2(SOCR)2 (R = Me, Ph) and Mo(CO)2(PPh3)2Br(NO3) have been characterized by elemental analysis, IR spectroscopy, and conductivity measurements. An improved synthesized of Mo(CO)2(PPh3)2(S2COCH3)2 is described.

2-methyl- and 2-ethylamino-3-pieoline N-oxide complexes formed from various copper(II) salts

Copper(II) complexes with 2-methylamino-3-picoline N-oxide (3MMH) and 2-ethylamino-3-picoline N- oxide (3MEH) have been prepared from the following salts: tetrafluoroborate, nitrate, chloride, bromide and acetate. Solids of the general formula [Cu(LH) 4]- (X 2) (where LH = either ligand when X = BF 4 tau; and LH = 3MMH when X = NO 3 tau; ); [Cu(3MEH) 2- (ONO 2) 2]; [Cu(LH)X 2] (where LH = either ligand and X = Cl tau; , Br tau; ) and CuL 2 (where L = either ligand's conjugate base) were characterized using spectral methods ( i.e., IR, UV-Vis and ESR). Both coordinate as monodentate ligands via their N-oxide oxygen in their complexes with salts having polyatomic anions. They bond as neutral bidentate ligands in their halide complexes, but as anionic bidentate ligands in the complexes formed from copper(II) acetate. The bonding to Cu(II) ccnters via the N-oxide oxygen is the strongest tor these two ligands based on spectral data than any of the 2-aminopyridine N-oxides or 2- aminopicoline N-oxides studied to date.

Studies on ruthenium(II) complexes with ligands containing the amide group

Reactions of RuCl 2(DMSO) 4 with some of the biologically active polydentate ligands containing an amide group yielded a number of stable complexes, effecting partial or complete displacement of DMSO groups from the complex, depending on the type of ligand. The interaction of anionic bidentate ligands with RuCl 2(DMSO) 4 yielded neutral complexes of the type Ru(DMSO) 2(LL) 2 (LL = AAB,BAB, MA, ACB, PACB and NACB) displacing only two DMSO groups and the two chlorides. With uninegative terdentate ligands, all the DMSO groups were displaced and complexes of the formula Ru(L) 2(L = ABAB, APACB and ABB) were obtained. A complex RuCl 2(DMSO) 2(ABA) 2 was also obtained by a similar method. The infrared and proton NMR spectra of these complexes have been found to be useful in identifying and characterising them.