An investigation of Cu(II) and Ni(II)-catalysed hydrolysis of (di)imines

The reactions of six diimine ligands with Cu(II) and Ni(II) halide salts have been investigated. The diimine ligands were Ph₂CN(CH₂)_nNCPh₂ (n = 2 (Bz₂en, 1a), 3 (Bz₂pn, 1b), 4 (Bz₂bn, 1c)), N,N′-bis-(2-tert-butylthio-1-ylmethylenebenzene)-2,2′diamino-biphenyl (2), N,N′-bis-(2-chloro-1-ylmethylenebenzene)-1,3-diaminobenzene (3) and N,N′-bis-(2-chloro-1-ylmethylenebenzene)-1,2-ethanediamine (4). Reactions of 1a-c, 2-4 with CuCl₂·2H₂O in dry ethanol at ambient temperature led to complete or partial hydrolysis of the diimine ligands to ultimately form copper diamine complexes. The non-hydrolyzed complexes of 1b and 1c, [Cu(L)Cl₂] (L = 1b, 1c), could be isolated when the reactions were carried out at low temperatures, and the half-hydrolyzed complex [Cu(Bzpn)Cl₂] could also be identified via X-ray crystallography. Similarly, reactions of 1a or 1b with NiCl₂·6H₂O or [NiBr₂(dme)] led to rapid hydrolysis of the imines and Ni complexes containing half-hydrolyzed 1a (Bzen; [trans-[Ni(Bzen)₂Br₂]) and 1b (Bzpn; [Ni(Bzpn)Br₂] could be isolated and identified via single crystal X-ray analysis. Kinetic studies were made of the hydrolyses of 1a, 1b in THF and 2 in acetone, in the presence of Cu(II), and of 1a in acetonitrile, in the presence of Ni(II). Activation parameters were determined for the latter reaction and for the copper-catalyzed hydrolysis of 2; the relatively large negative activation entropies clearly indicate rate-determining steps of an associative nature.     

2-(1-(Dimethylamino)ethyl)phenylpalladium(II) complexes 5-functionalized with fluorous silyl tails

New fluorous-organometallics based on the chiral ligand α-methyl-N,N-dimethylbenzylamine (TMBA) were prepared by treatment of fluorous silyl bromide reagents with in situ 4-lithiated TMBA to give fluorous N,N-dimethyl(α-methyl-4-trialkylsilylbenzyl)amine ligands 1a-1c that vary in the number of fluorous tails attached to the Si atom. Ligands 1a-1c were successfully cyclo-palladated by treatment with Pd(OAc)₂/LiCl in methanol to furnish the corresponding chloride-bridged dimeric arylpalladium(II) complexes 2a-2c in good yields. The latter derivatives could be converted into monomeric Lewis-base adducts by complexation with pyridine (3a-3c), or triphenylphosphine (4a-4c). The crystal structure of triphenylphosphine complex 4a has been elucidated. To probe their fluorophilicity, the partition coefficient of each of the derivatives in the fluorous biphasic solvent (FBS) system perfluoromethylcyclohexane/n-octane has been determined.     

Synthesis of 1,6-Diaryl-5,7-dioxo(dithio)imidazo[1,2-a] [1,3,5]triazines. A Novel Pathway for Imidazo[1,2-a] [1,3,5]triazine Systems Obtained via 1-(Imidazolin-2-yl)urea and Thiourea Derivatives

Novel 1,6-diaryl-5,7(1H)dioxo(dithio)-2,3-dihydroimidazo[1,2-a][1, 3, 5]triazines 8, and 9 were synthesized by cyclization of the respective 1-(imidazolin-2-yl)ureas 4 or thioureas 6 with phosgene or thiophosgene in the presence of bases. 1-Aryl-2-aminoimidazolines 1 reacting with arylisocyanates 2 or arylisothiocyanates 3 form a mixture of isomeric imidazolin-2-yl 4 and 6 and imidazolin-3-yl 5 and 7 urea or thiourea derivatives. Isomers 4 and 6 can be easily separated and used for the cyclization reaction. The structures of the main intermediates and the final target compounds were confirmed by ¹H-NMR spectral analysis. Discussion of the possible course of the reactions is also presented.     

8-Quinolinolato complexes of ruthenium(II) and (III)

Reduction of RuQ₃ (1a, Q = 8-quinolinolato) with Zn/Hg in the presence of various π-acceptor ligands in ethanol affords RuQ₂L₂ (L₂ = (dimethylsulfoxide)₂ (2); (4-picoline)₂ (3); N,N′-dimethyl-1,4-diazabuta-1,3-diene, dab (4); cyclooctadiene, COD (5); norborna-2,5-diene, nbd (6)). Compound 6 is isolated as an equimolar mixture of cis,trans (6a) and trans,cis (6b) isomers, which can be separated by column chromatography. DFT calculations have been performed on 6a and 6b. Oxidation of 3 and 6b affords the corresponding ruthenium(III) species 7 and 8, respectively. The structures of 2, 3, 4 and 6 have been determined by X-ray crystallography.     

N(4)-Tolyl-2-acetylpyridine thiosemicarbazones and their platinum(II,IV) and gold(III) complexes: cytotoxicity against human glioma cells and studies on the mode of action

Complexes [Au(2Ac4oT)Cl][AuCl₂] (1), [Au(H_py2Ac4mT)Cl₂]Cl·H₂O (2), [Au(H_py2Ac4pT)Cl₂]Cl (3), [Pt(H2Ac4oT)Cl]Cl (4), [Pt(2Ac4mT)Cl]·H₂O (5), [Pt(2Ac4pT)Cl] (6) and [Pt(L)Cl₂OH], L = 2Ac4mT (7), 2Ac4oT (8), 2Ac4pT (9) were prepared with N(4)-ortho- (H2Ac4oT), N(4)-meta- (H2Ac4mT) and N(4)-para- (H2Ac4pT) tolyl-2-acetylpyridine thiosemicarbazone. The cytotoxic activities of all compounds were assayed against U-87 and T-98 human malignant glioma cell lines. Upon coordination cytotoxicity improved in 2, 5 and 8. In general, the gold(III) complexes were more cytotoxic than those with platinum(II,IV). Several of these compounds proved to be more active than cisplatin and auranofin used as controls. The gold(III) complexes probably act by inhibiting the activity of thioredoxin reductase enzyme whereas the mode of action of the platinum(II,IV) complexes involves binding to DNA. Cells treated with the studied compounds presented morphological changes such as cell shrinkage and blebs formation, which indicate cell death by apoptosis induction.     

Synthesis and characterization of bis(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato) strontium and barium adducts with O- and N- ancillary ligands; crystal structure of Sr(tftb)2(batcp)

Complexes of type [M(tftb)₂L_n] [M=Sr; n=1, L=tetraglyme (4), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (5), n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (6); M=Ba; n=1, L=tetraglyme (7), 2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp) (8); n=2, L=2,2^′-bipyridine-N,N^′ (bipy) (9)] were prepared by in situ reactions of 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htftb) (1) with M(OH)₂ [M=Sr (2a); Ba (2b)] in the presence of the ancillary ligands L (3a: L=tetraglyme; 3b: L=2,3-benzo-10-aza-1,4,7,13-tetraoxacyclopentadeca-2-ene (batcp); 3c: L=2,2^′-bipyridine-N,N^′ (bipy)) in aqueous ethanol. The compounds were obtained in high yields and characterized by elemental analysis, ¹H NMR, mass spectrometry and IR analysis. Molecular structure of the [Sr(tftb)₂(batcp)] (5) has been determined by X-ray single crystal analysis.     

Synthesis and Reactions of Some 2-Aminobenzothiazoles

N-(2-Benzothiazolyl)- and N-(6-methoxy-2-benzothiazolyl)cyanoacetamides 4, 5 resulted in the reaction of 2-aminobenzothiazole 1 or its 6-methoxy derivative 2 with 1-cyanoacetyl-3,5-dimethylpyrazole 3. Both cyanoacetylamides 4 and 5 have been transformed into the corresponding 2-oxo-2H-pyrimido[2,1-b]-benzothiazole-3-carbonitrile 8 and its 8-methoxy derivative 9 by reaction with triethyl orthoformate, followed by cyclization.     

Syntheses and structures of cobalt(III) alcoholate complexes formed by addition of a water molecule across 2-pyridyl substituted imine function

Schiff bases L1-L5 {N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L1), 3-methyl-N-[1-pyridine-2-ylmethylidene]pyridine-2-amine (L2), 3-methyl-N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L3), 4-methyl-N-[1-pyridine-2-ylmethylidene]pyridine-2-amine (L4), 4-methyl-N-[1-pyridine-2-ylethylidene]pyridine-2-amine (L5)} were synthesized and on reaction with Co(NO₃)₂·6H₂O, complexes having the molecular formulae [Co(L1O)₂]NO₃ (1), [Co(L2O)₂]NO₃·xH₂O (2a, x = 2; 2b, x = 3), [Co(L3O)₂]NO₃ (3), [Co(L4O)₂]NO₃·4H₂O (4), [Co(L5O)₂]NO₃ (5) were isolated from the respective imines. The salt [Co(L2O)₂]PF₆ (2c) was obtained by treating 2 with KPF₆. Complexes 1-5 were formed as a result of addition of a water molecule across the imine function and the resultant alcohol binds in its deprotonated form. The alcoholate ion remained bound in a facial tridentate fashion to the low-spin cobalt(III). X-ray crystal structure determination confirmed the presence of trans-trans-trans-N_AN_PO (A = aminopyridyl and P = pyridyl) disposition in 2a and cis-cis-trans-N_AN_PO in 2b, 2c and 4. Water dimers in 2a, 2b, 4 and water-nitrate ion network in 2a were other notable features.     

New insight in coordination of vic-dioximes: Bis- and tris(E,E-dioximato)Ni(II) complexes

N,N′-Bis[allylamino]glyoxime, N,N′-bis[anilino]glyoxime, and N,N′-bis[1,2,3,4-tetrahydro-5-naphthalenamino]glyoxime have been prepared from corresponding amines and (E,E)-dichloroglyoxime. These ligands gave orange-red compound with NiCl₂ in less acidic medium (pH ∼ 5) that are bis(E,E-dioximato)nickel(II) complexes {[(E,E)-Ni(HL)₂]} (1a-3a) and green compounds in acidic medium (pH ∼ 2) that are tris(E,E-dioximato)nickel(II) dichloride complexes {[(E,E)-Ni(LH₂)₃]Cl₂} (1b-3b). The crystal structures of all complexes have been determined by X-ray diffraction on a single crystal. The study of absorption spectra of these two types of complexes shows that they may be converted to each other by addition of acids (1a-3a) or bases (1b-3b) and there is no way for the amphi form.     

Octahedral Co(III) complexes of 2-(phenylimino)pyrrolyl ligands: Synthesis and structural characterisation

The reactions of CoCl₂ with three equivalents of 2-(phenylimino)pyrrolyl sodium salts, performed under a nitrogen atmosphere, lead to the formation of the Co(III) complexes [Co(κ²N,N′-NC₄H₃C(H)N-C₆H₅)₃] (2a), [Co(κ²N,N′-NC₄H₃C(CH₃)N-C₆H₅)₃] (2b) and [Co(κ²N,N′-NC₁₆H₉C(H)N-C₆H₅)₃] (2c), accommodating three chelating iminopyrrolyl ligands. Complexes 2a-c were obtained in moderate yields, and their characterisation by ¹H, ¹³C NMR and X-ray diffraction show they are diamagnetic and have an octahedral geometry about the cobalt centre, respectively. Uncharacterised products were obtained in the same reaction involving ligand precursors such as 2-(2,6-dimethylphenylimino)pyrrolyl sodium salts, which is attributed to a greater steric hindrance in the coordination of three of these bulkier ligands. The redox behaviour of complexes 2a-c shows an irreversible reduction wave with a peak potential in the range −3.2 to −3.7 V. Upon reduction, the complexes decompose giving rise, in the case of 2a, to a redox pattern compatible with the formation of [Co(κ²N,N′-NC₄H₃C(H)N-C₆H₅)₂].     

Polymorphism and weak antiferromagnetic interactions in dibromo[(−)-sparteine-N,N]copper(II)

Two polymorphic crystal structures of the title compound, dibromo[(−)-sparteine-N,N^′]copper(II), 1, were determined. The structures of two isomorphs of 1, 1a [orthorhombic, P2₁2₁2₁, a=11.0463(9) Å, b=11.9839(15) Å and c=12.7835(19) Å] and 1b [orthorhombic, P2₁2₁2₁, a=7.6779(9) Å, b=12.0927(14) Å and c=18.090(2) Å], are composed of the same basic structural unit, Cu(C₁₅H₂₆N₂)Br₂. The bond distances in the molecular structures of 1a and 1b are identical to each other within the esds. However, there are slight differences in the bond angles around the Cu(II) center and considerable differences in their packing structure. Crystal 1a exhibits weak anti-ferromagnetism (J=−1.89 cm⁻¹) as opposed to the magnetically isolated paramagnetism observed for the analogous dichloro[(−)-sparteine]copper(II), 2. The results of a magneto-structural investigation of 1a and 2, and other supporting evidence, suggest that the pathway for the weak antiferromagnetic super-exchange in 1a might be through a Cu-Br ? Br-Cu contact.     

Synthesis and structural diversity of 2-pyridylmethylideneamine complexes of zinc(II) chloride

The addition reactions of zinc(II) chloride to N-substituted pyridine-2-carbaldimines [Py-CHNR, R = Me (1a), Ph (1b), Bz (1c), allyl (1d)] lead to different complexes dependent on the N-bound substituent R. The 1:1 complexes show molecular structures of the type [(Py-CHNR)ZnCl₂] for R = methyl (2a), phenyl (2b), and allyl (2d) with a distorted tetrahedral environment for the zinc atom. The zinc complex with the N-methylated pyridine-2-carbaldimine also forms a dimer of the type [(Py-CHNR)ZnCl₂]₂ (2a)₂ with a square pyramidal coordination sphere of zinc. A 3:2 stoichiometry is observed for R = benzyl and an ion pair of the type [Zn(Py-CHNR)₃]²⁺ [ZnCl₄]²⁻ (2c) is found in the solid state.     

Coupling of cationic olefin complexes of platinum(II) with potential ambident nucleophiles

The reactivity of [PtCl(η²-CH₂CHR)(tmeda)]⁺ (R = H, 1a, or Me, 1b; tmeda = N,N,N′,N′-tetramethyl-1,2-diaminoethane) towards some ambident nucleophiles like anilines and phenolate anion has been tested. The reaction of 1a with N-methylaniline gives immediately N-addition to the coordinated ethene (3a), but, in the presence of an inorganic carbonate, a partial rearrangement, with the para carbon of the phenyl ring taking the place of nitrogen, is observed (4a and 5a). Reaction with a tertiary aromatic amine, such as N,N-dimethylaniline, leads exclusively to the C-coupled species. The phenolate anion acts initially as an oxygen donor, however the resulting species (6a), in contact with free phenol, rearranges to C-bonded species (7a). For free phenol/6a ratios ? 5 the rearranged product has an isomeric ortho/para ratio of ≈3. For lower free phenol/6a ratios (? 1) oligomeric complexes, in which two or three platinum ethanide moieties are bound to the same phenol ring, are also formed. In the case of 1b, the above described reactivity has to compete with the base-induced deprotonation of propene, leading to formation of the allyl-bridged platinum dimer [{PtCl(tmeda)}(μ-η¹:η³-CHCHCH₂){Pt(tmeda)}]⁺. The X-ray crystal structure of 1b has also been determined; the structural parameters are very similar to those previously reported for 1a. DFT calculations have shown a similar activation of the two complexes towards nucleophilic addition at the coordinated olefin, although in 1b the electrophilic character of the olefin is masked by the Brønsted acidity of the propene methyl protons.     

2-Phenylpyridine ruthenacycles as effectors of glucose oxidase activity: inhibition by RuII and activation by RuIII

Cyclometalated Ru^II derivatives of 2-phenylpyridine (Hphpy) [Ru(phpy)(bpy)₂]Cl (1a) and [Ru(phpy)(phen)₂]Cl (1b) (bpy is 2,2′-bipyridine, phen is 1,10-phenanthroline) behave as noncompetitive inhibitors of glucose oxidase from Aspergillus niger in the enzyme-catalyzed oxidation of d-glucose by O₂ into the corresponding lactone at pH 5.0 and 25 °C. The enzymatic activity has been measured by monitoring the O₂ consumption. The inhibition constants K _i are 0.036 and 0.017 M for 1a and 1b, respectively, indicating that 1b inhibits the enzymatic activity more efficiently than 1a. The well-known coordination compound [Ru(bpy)₃]Cl₂ (2) behaves, in contrast, as a competitive inhibitor, with K _i = 0.018 M under the same conditions. The monophasic consumption of O₂ in the case of 1a, 1b, and 2 is replaced by a distinct two-phase kinetics in the presence of the cyclometalated Ru^III compound [Ru(phpy)(bpy)₂]Cl₂ (3), which was obtained from 1a in the presence of a large excess of H₂O₂ and the iron TAML activator. Interestingly, the rates of the first and the second phases are influenced by 3 in a different way. The rate of the first phase is noticeably higher in the presence of Ru^III, although the dependence is nonmonotonic and maximal acceleration is observed at the lowest loadings of 3. The rate of the second phase decreases monotonically on increasing the concentration of the ruthenium complex in solution. The nonmonotonic action of 3 was confirmed by using the doubly cyclometalated Ru^III derivative [Ru(phpy)₂(bpy)]Cl. The diverse rate variations induced by 3 accounted for acceleration by Ru^III of the O₂ reduction by the reduced form of glucose oxidase during the first phase, which ceases after the enzymatic reduction of Ru^III to the Ru^II species, the latter behaving similarly to 1a as the inhibitor of the enzyme.     

Macrocyclic dinuclear gold(I) and silver(I) NHCs complexes

The ligands bis-(imidazolium) hexafluorophosphate (Himy = -C₃N₂H₃-, imidazolium; R = 1-naphthylmethylene, 1a; 9-anthracenylmethylene, 1b) with an oxoether chain were easily prepared by the reaction of substituted imidazole with the diglycol diiodide, followed by exchange of anions with . 1a and 1b reacted with Ag₂O in DMSO or CH₃CN to yield [2 + 2] dinuclear Ag(I) NHCs macrocyclic complexes 2a and 2b, which showed much different conformation in solid corresponding to the R- substituent. Carbene transmetalation reactions of 2a-b with Au(SMe₂)Cl give dinuclear Au(I) analogs 3a and 3b. The new NHCs complexes were characterized by elemental analyses, ¹H NMR, ¹³C NMR and the structures of 2a-b and 3a were confirmed by X-ray diffraction determination.     

Synthesis and complexation of tetrakis(diphenylphosphinomethyl)calix[4]arene adopting the 1,3-alternate conformation

Novel upper-rim modified tetraphosphinocalix[4]arenes (5a-b) adopting 1,3-alternate conformation have been synthesized. Reaction of 5,11,17,23-tetrachloromethyl-25,26,27,28-tetrahydroxycalix[4]arene (1) with Ph₂POEt gave 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrahydroxycalix[4]arene (2). Tetra-O-substitution of 2 with n-propyl iodide or benzyl bromide in the presence of K₂CO₃ carried out to afford 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,26,27,28-tetrapropoxy-(3a) or -benzyloxycalix[4]arene (3b), whereas di-O-substituted calix[4]arene, 5,11,17,23-tetrakis(diphenylphosphinoylmethyl)-25,27-dipropoxy-26,28-dihydroxycalix[4]arene (4), was obtained exclusively when Na₂CO₃ was used as base. Reduction of 3a-b with PhSiHCl₂ afforded 5,11,17,23-tetrakis(diphosphinomethyl)-25,26,27,28-tetrapropoxy-(5a) and -tetrabenzyloxycalix[4]arene (5b). ¹H and ¹³C NMR analysis reveals that the phosphines (5a-b) and the tetra-O-substituted phosphine oxides (3a-b) adopt 1,3-alternate conformation, while the parent tetrahydroxy-(2) and the di-O-propylated phosphine oxide (4) adopt cone-conformation. The X-ray structure indicates that the calix[4]arene moieties in 4 a pinched-cone conformation in solid state. Complexation of the phosphine ligand (5a) with [RuCl₂(p-cymene)]₂ affords the tetranuclear complexes, [{RuCl₂(p-cymene)}₂ · 5a] (6), as 1,3-alternate conformer.     

Synthesis and characterization of cobalt(II)-salicylate complexes derived from N4-donor ligands: Stabilization of a hexameric water cluster in the lattice host of a cobalt(III)-salicylate complex

The syntheses and structural characterization of four cobalt(II)-salicylate complexes, [(TPA)Co^II(HSA)](ClO₄) (1), [(isoBPMEN)Co^II(HSA)](BPh₄) (2), [(TPzA)Co^II(HSA)](ClO₄) (3) and [(6Me₃TPA)Co^II(HSA)](BPh₄) (4) [TPA = tris(2-pyridylmethyl)amine, isoBPMEN = N¹,N¹-dimethyl-N²,N²-bis(2-pyridylmethyl)ethane-1,2-diamine, TPzA = tris((3,5-dimethyl-1H-pyrazole-1-yl)methyl)amine and 6Me₃TPA = tris(6-methyl-2-pyridylmethyl)amine] are described. While 2, 3 and 4 are unreactive towards dioxygen, 1 reacts slowly with molecular oxygen to a cobalt(III)-salicylate complex, [(TPA)Co^III(SA)](ClO₄) (1a). Two different crystalline forms, 1a and 1a·4H₂O were isolated depending upon the condition of oxidation and crystallization. The solid-state structures of cobalt(III)-salicylate unit in both 1a and 1a·4H₂O show a six-coordinate distorted octahedral coordination geometry at the cobalt(III) center ligated by the tetradentate ligand (TPA) where the dianionic salicylate (SA) binds in a bidentate fashion through one carboxylate and one phenolate oxygen. The hydrated form 1a·4H₂O reveals a hexameric water cluster formation in the inorganic lattice host. The complex cation and the perchlorate counterion are involved in stabilizing the (H₂O)₆ cluster in a rare ‘pentamer planar+1’ conformation. A one-dimensional water tape consisting of edge-shared water hexamers is observed. The water tape represents a subunit of ice structure.     

New names,combinations, and lectotypifications in Heterotheca (Compositae: Astereae)

The following new names and combinations are proposed:Heterotheca barbata (Rydb.) Semple,H. horrida subsp.cinerascens (S. F. Blake) Semple,H. fulcrata vararizonica Semple,H. fulcrata var.senilis (Wooton & Standley) Semple,H. oregona var.compacta (Keck) Semple,H. oregona var.rudis (Greene) Semple,H. oregona var.scaberrima (A. Gray) Semple,H. pumila (Greene) Semple,H. villosa var.pedunculata (Greene) V. Harms ex Semple, andH. zionensis Semple. The following chromosome numbers are reported for the first time:H. fulcrata var.arizonica, 2n=9 _II ;H. horrida subsp.cinerascens, 2n=18 _II ;H. pumila, 2n=9 _II ,2n=18 _II ;H. zionensis, 2n=9 _II .     

Synthesis and characterization of ruthenium(II) complexes bearing the bis(2-pyridylmethyl)amine ligand

The reaction of [Ru(CO)₂Cl₂]_n with bis(2-pyridylmethyl)amine (bpma) in refluxing ethanol followed by anion exchange yields two products: cis,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1a, 71%) and trans,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1b, 29%). Reaction of 1a with AgBF₄ in acetone, followed by acetonitrile and then anion exchange gave cis,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2a). In the same way, 1b afforded trans,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2b). Reaction of depolymerized [Ru(CO)₂Cl₂]_n with bpma in ethanol at room temperature afforded cis,cis-[Ru(η²-bpma)(CO)₂Cl₂] (3). In refluxing ethanol, 3 was converted to cis,fac-[Ru(bpma)(CO)₂Cl]Cl (1a-Cl). Heating 3 in chlorobenzene afforded 1b-Cl, exclusively; heating 3 in ethylene glycol gave mainly 1a-Cl. Heating 1a-Cl in ethanol resulted in no isomerization, but heating in chlorobenzene gave a mixture of 3 and 1b-Cl. Anion exchange for PF₆ with 1a-Cl and 1b-Cl afforded 1a and 1b, respectively, whereas anion exchange for BPh₄ afforded 1a-BPh₄. Compounds 1a, 1b, 2a and 3 have been structurally characterized.