Syntheses of tris(t-butylisocyanide)bis(tri-p-dimethyl- aminophenylphosphine)cobalt(I) and cobalt(II) perchlorates: a reversal of the usual stabilities of cobalt oxidation states

The complexes [Co(CNCMe₃)₃{P(C₆H₄NMe₂-p)₃}₂](ClO₄)₂ and [Co(CNCMe₃)₃{P(C₆H₄NMe₂ -p)₃}₂]ClO₄ are reported. The Co(II) complex, formed by reaction of excess triarylphos-phine with the alkylisocyanide Co(II) complex, is stable and the favoured product. The Co(I) complex, formed by hydrazine reduction of the Co(II) complex, has limited stability in solution, readily oxidizing to the Co(II) species. Upon prolonged irradiation of the Co(II) complex in acetone, [Co{OP(C₆H₄NMe₂-p)₃}₄](ClO₄)₂ is produced.     

Synthesis and selected reactions of pentakis ( t -octylisocyanide)cobalt(II) complexes

The ligand 1,1,3,3-tetramethylbutylisocyanide, CNCMe₂CH₂CMe₃, i.e. t-octylisocyanide, with Co(ClO₄)₂ · 6H₂O or Co(BF₄)₂ · 6H₂O in ethanol, produces pentakis(alkylisocyanide)cobalt(II) complexes, [Co(CNC₈H₁₇-t)₅](ClO₄)₂ (1) and [Co(CNC₈H₁₇-t)₅](BF₄)₂ · 2.0H₂O (2). These Co(II) complexes undergo reduction/substitution upon reaction with trialkylphosphine ligands to produce [Co(CNC₈H₁₇-t)₃{P(C₄H₉-n)₃}₂]ClO₄ (3), [Co(CNC₈H₁₇-t)₃{P(C₄H₉-n)₃}₂]BF₄ (4), and [Co(CNC₈H₁₇-t)₃{P(C₃H₇-n)₃}₂]ClO₄ (5). Complex 3 is oxidized with AgClO₄ to produce [Co(CNC₈H₁₇-t)₃{P(C₄H₉-n)₃}₂](ClO₄)₂ (6). Complex 1 yields [Co(CNC₈H₁₇-t)₄py₂](ClO₄)₂ (7) upon dissolving in pyridine. Reactions with triarylphosphine and triphenylarsine ligands were unsatisfactory. The chemistry of 1 and 2 is therefore more similar to that of Co(II) complexes with CNCMe₃ than with CNCHMe₂, other alkylisocyanides, or arylisocyanides, but shows some behavior dissimilar to any known Co(II) complexes of alkylisocyanides or arylisocyanides. Infrared and electronic spectra, magnetic susceptibility, molar conductivities, and cyclic voltammetry are reported and compared with known complexes. ¹H, ¹³C, and ³¹P NMR data were also measured for the diamagnetic complexes 3, 4, and 5.     

Monocarbonyl cationic rhodium(I) complexes

Summary The preparations and characterisation of cationic complexes of the type [Rh(CO)(MeCN)(PR₃)₂]ClO₄, [Rh(CO)L(PR₃)₂]ClO₄ (L=py or 2-MeOpy), [Rh(CO)(L-L)(PR₃)₂]ClO₄ (L-L = bipy or phen) and [Rh(CO)(PR₃)₃]ClO₄ with PR₃ = P(p-YC₆H₄)₃ (Y=Cl, F, Me or MeO) are described.     

Syntheses of <Emphasis Type="Italic">tetrakis</Emphasis>(benzylisocyanide)<Emphasis Type="Italic">bis</Emphasis>(tri-<Emphasis Type="Italic">i</Emphasis>-propylphosphite) cobalt(III) tetrafluoroborate: comparison with trialkylphosphine–alkylisocyanide complexes of cobalt(III)

Tetrakis(benzylisocyanide)bis(tri-i-propylphosphite)cobalt(III) tetrafluoroborate, [Co(CNCH₂Ph)₄{P(OCHMe₂)₃}₂] (BF₄)₃, has been synthesized by ligand substitution of both [Co(CNCH₂Ph)₄{OAs(C₆H₄Me-p)₃}₂](BF₄)₃ and [Co(CNCH₂Ph)₄(OSbPh₃)₂](BF₄)₃. IR and electronic spectra, magnetic susceptibility, and cyclic voltammetric measurements are reported. The data are consistent with low-spin tetragonal coordination; i.e., trans-[Co(CNCH₂Ph)₄{P(OCHMe₂)₃}₂](BF₄)₃. Comparison is made with tetrakis(alkylisocyanide)bis(trialkylphosphine) cobalt(III) complexes.     

Synthesis and reactivity of some isocyanide complexes of iridium(I)

Several isocyanide complexes [Ir(RNC)₄]X (I) (R = p-CH₃C₆H₄, X = I; R = p-CH₃OC₆H₄, X = I and PF₆) and [Ir(RNC)₂(PPh₃)₃] ClO₄(II) (R = p-CH₃C₆H₄ and p-CH₃OC₆H₄) have been prepared by the reactions of [Ir(COD)Cl]₂ and [Ir(COD)(PPh₃)₂]ClO₄ (COD = l,5-cyclooctadiene) with aryIisocyanides, respectively. Oxidative addition reactions of I and II with halogens, and II with π-acids such as tetracyanoethylene(TCNE), fumaronitrile, maleic anhydride, dimethyl fumarate, acrylonitrile, and dimethyl acetylenedicarboxylate are described. The structures of I, II and the π-acid addition products of II, [Ir(p-CH₃C₆H₄NC)₂ (PPh₃)₂ (π-acid)]ClO₄ (IV) (π-acid = TCNE, fumaronitrile, maleic anhydride, and acetylene dicarboxylate), are discussed on the basis of their electronic, IR, and NMR spectra. Especially, I is suggested to have an unusual layer structure involving Ir to Ir interaction, the result of which is relatively low reactivity in oxidative addition reactions. Trigonal bipyramidal configurations are suggested for IV with the two isocyanides in the trans and cis positions for the olefin and acetylene adducts, respectively.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe,V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V^[1]. – Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand^* The lithium and sodium salts of the [C₅H₅CH₂C₅H₄]^- anion, 1 and 2 , react with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [Ir(CO)₃Cl]n to give predominantly the mononuclear complexes [(C₅H₅-CH₂C₅H₄)M(CO)₂] ( 3, 5, 7 ) together with small amounts of the dinuclear compounds [CH₂(C₅H₄)₂][M(CO)₂]₂ ( 4, 6, 8 ). The ¹H- and ¹³C-NMR spectra of 3, 5 , and 7 prove that the CH₂C₅H₅ substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [C₅H₅TiCl₃] the heteronuclear complexes [CH₂(C₅H₄)₂][M(CO)₂][M′(CO)₂] ( 11–13 ) and [CH₂(C₅H₄)₂]-[Ir(CO)₂][C₅H₅TiCl₂] ( 17 ) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH₂(C₅H₄)₂][M(CO)(μ-CO)M′(CO)] ( 14, 15 ). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH₂(C₅H₄)₂][Rh₂(CO)₂(μ-CO)] ( 16 ).     

Reactions of [Re(NO)2(PR3)2][BArF 4] complexes with phenylacetylene

The reaction of [Re(NO)₂(PR₃)₂][BAr^F ₄] (R = cyclo-C₆H₁₃ (1a), Prⁱ (1b); [BAr^F ₄]^– = [B(3,5-(CF₃)₂C₆H₃)₄]) with phenylacetylene in the presence of a non-nucleophilic base, like 2,6-bis(tert-butyl)pyridine (BTBP) or Bu^tOK, affords the phenylethynyl complexes [Re(CCPh)(NO)₂(PR₃)₂] (R = cyclo-C₆H₁₃ (2a); Prⁱ (2b)) in moderate yields. In the absence of a base, complexes 1a and 1b are transformed into the compounds [Re(CCPh)(CH=C(Ph)ONH)(NO)(PR₃)₂][BAr^F ₄] (3a and 3b, respectively). The structure of complex 3a was confirmed by X-ray diffraction analysis. The latter reaction is proposed to be initiated by deprotonation of the terminal alkyne H atom by the bent nitrosyl ligand followed by the subsequent 1,3-dipolar addition of the ReN(H)O moiety to phenylacetylene.     

Cytotoxic activity of iron(III), cobalt(III), nickel(II), zinc(II), and cadmium(II) complexes of 2-acetylpyrazine thiosemicarbazone: crystal structure of the cobalt(III) complex

Transition metal complexes [Fe(HL)₂]Cl₃ ? 1.5H₂O (1), [Co(L)₂] ? ClO₄ ? H₂O (2), Ni(HL)₂(ClO₄)₂ ? 2H₂O (3), Zn(HL)L ? BF₄ ? 2H₂O (4), and Cd(HL)₂(ClO₄)₂ ? 2H₂O (5), where HL = C₇H₉N₅S, 2-acetylpyrazine thiosemicarbazone, have been synthesized. Complex 2 was characterized by elemental analysis, infrared spectra, mass spectra, and single-crystal X-ray diffraction. Preliminary in vitro screening showed that 1, 4, and 5 exhibit higher antitumor activity than 2 and 3 against K562 leucocythemia cancer cell line.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe. VIII. Zweikernige Cobaltkomplexe mit dem Dianion des Bis(cyclopentadienyl)methans und des Bis(tetramethylcyclopentadienyl)dimethylsilans als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes. VIII. Dinuclear Cobalt Complexes with the Dianion of Bis(cyclopentadienyl)methane and Bis(tetramethylcyclopentadienyl)dimethylsilane as Bridging Ligands The dinuclear cobalt complex [CH₂(C₅H₄)₂][Co(CO)₂]₂ ( 4 ) which is obtained from [Co(CO)₄I] ( 2 ) and Li₂[CH₂(C₅H₄)₂] ( 3 ) in 75% yield reacts with PMe₃, PiPr₃, P₂Me₄, Me₂PCH₂CH₂PMe₂ and (EtO)₂POP(OEt)₂, to the compounds 5–9 substituting one CO ligand per cobalt atom. Oxidative addition of CH₃I to [CH₂(C₅H₄)₂][Co(CO)(PMe₃)]₂ ( 5 ) leads to the formation of the dinuclear cobalt(III) complex [CH₂(C₅H₄)₂][Co(COCH₃)(PMe₃)I]₂ ( 11 ). The reaction of 4 with iodide generates [CH₂(C₅H₄)₂][Co(CO)I₂]₂ ( 12 ) which with PMe₃, P(OMe)₃, P(OiPr)₃, and CNMe reacts under CO substitution to [CH₂(C₅H₄)₂][Co(L)I₂]₂ ( 13–16 ) and with PMe₂H to {[CH₂(C₅H₄)₂][Co(PMe₂H)₃]₂}I₄ ( 17 ). The electrophilic addition reactions of NH₄PF₆ and CH₃I to [CH₂(C₅H₄)₂][Co(PMe₃)₂]₂ ( 20 ) produce the complex salts {[CH₂(C₅H₄)₂][CoR(PMe₃)₂]₂}X₂ ( 21 : R = H; 22 : R = CH₃). From 22a (X = I) and LiCH₃ the dinuclear tetramethyldicobalt compound [CH₂(C₅H₄)₂] · [Co(CH₃)₂(PMe₃)]₂ ( 23 ) is obtained which further reacts, via the intermediate 24 , to the chiral complex {[CH₂(C₅H₄)₂] · [CoCH₃(PMe₃)P(OMe)₃]₂}(PF₆)₂ ( 25 ). The reaction of 20 with C₂(CN)₄ and E- or Z-C₂H₂(CO₂Me)₂ gives the olefin(trimethylphosphine) cobalt(I) derivatives 26 und 27 . The synthesis of the dinuclear compounds 31–38 with [Me₂Si(C₅Me₄)₂]^2? as the bridging unit is also described.     

Formation of 18e− and 16e− Acyl(η3‐cyclooctenyl)rhodium(III) Complexes in the Reaction of Cationic (Cycloocta‐1,5‐diene)rhodium(I) Compounds with 2‐(Diphenylphosphino)benzaldehyde

The reaction of cationic diolefinic rhodium(I) complexes with 2‐(diphenylphosphino)benzaldehyde (pCHO) was studied. [Rh(cod)₂]ClO₄ (cod=cycloocta‐1,5‐diene) reacted with pCHO to undergo the oxidative addition of one pCHO with (1,2,3‐η)cyclooct‐2‐en‐1‐yl (η³‐C₈H₁₃) formation, and the coordination of a second pCHO molecule as (phosphino‐κP)aldehyde‐κO(σ‐coordination) chelate to give the 18e⁻ acyl(allyl)rhodium(III) species [Rh(η³‐C₈H₁₃)(pCO)(pCHO)]ClO₄ (see 1 ). Complex 1 reacted with [Rh(cod)(PR₃)₂]ClO₄ (R=aryl) derivatives 3 – 6 to give stable pentacoordinated 16e⁻ acyl[(1,2,3‐η)‐cyclooct‐2‐en‐1‐yl]rhodium(III) species [Rh(η³‐C₈H₁₃)(pCO)(PR₃)]ClO₄ 7 – 10 . The (1,2,3‐η)‐cyclooct‐2‐en‐1‐yl complexes contain cis‐positioned P‐atoms and were fully characterized by NMR, and the molecular structure of 1 was determined by X‐ray crystal diffraction. The rhodium(III) complex 1 catalyzed the hydroformylation of hex‐1‐ene and produced 98% of aldehydes (n/iso=2.6).     

Ni(II), Pd(II), Cu(II) And Zn(II) complexes with N-(2-Pyridyl)Carbonylaniline (L), Syntheses and X-Ray Crystal structures of [Cu(L)2(H2O)2](No3)2, [Cu(L)2(H2O)2](Clo4)2 and [Zn(L)2(H2O)2](Clo4)2

Reaction of the N-(2-pyridyl)carbonylaniline ligand (L) with Cu(NO₃)₂, Cu(ClO₄)₂, Zn(ClO₄)₂, Ni(NO₃)₂ and PdCl₂ gives complexes with stoichiometry [Cu(L)₂(H₂O)₂](NO₃)₂, [Cu(L)₂(H₂O)₂](ClO₄)₂, [Zn(L)₂(H₂O)₂] (ClO₄)_2, [Ni(L)₂(H₂O)Cl](NO₃) and PdLCl₂. The new complexes were characterized by elemental analyses and infrared spectra. The crystal structures of [Cu(L)₂(H₂O)₂](NO₃)₂, [Cu(L)₂(H₂O)₂](ClO₄)₂, and [Zn(L)₂(H₂O)₂](ClO₄)₂ were determined by X-ray crystallography. The cation complexes [M(L)₂(H₂O)₂] contain copper(II) and zinc(II) with distorted octahedral geometry with two N-(2-pyridyl)carbonylaniline (L) ligands occupying the equatorial sites. The hexa-coordinated metal atoms are bonded to two pyridinic nitrogens, two carbonyl oxygens and two water molecules occupying the axial sites. Both the coordinated water molecules and uncoordinated amide NH groups of the N-(2-pyridyl)carbonylaniline (L) ligands are involved in hydrogen bonding, resulting in infinite hydrogen-bonded chains running in one and two-dimensions.     

Synthesis, spectroscopic, thermal Studies, antimicrobial activities and crystal structures of Co(II), Ni(II), Cu(II) and Zn(II)-orotate complexes with 2-methylimidazole

The 2-methylimidazole complexes of Co(II), Ni(II), Cu(II) and Zn(II) orotates, mer-[Co(HOr)(H₂O)₂(2-meim)₂] (1), mer-[Ni(HOr)(H₂O)₂(2-meim)₂] (2), [Cu(HOr)(H₂O)₂(2-meim)] (3) and [Zn(HOr)(H₂O)₂(2-meim)] (4), were synthesized and characterized by elemental analysis, spectral (UV–Vis and FT-IR) methods, thermal analysis (TG, DTG and DTA), magnetic susceptibility, antimicrobial activity studies and single crystal X-ray diffraction technique. The complexes 1 and 2 have distorted octahedral geometries with two monodentate 2-methylimidazole and one bidentate orotate and two aqua ligands. The complexes 3 and 4 have distorted square pyramidal and trigonal bipyramidal geometry, respectively, with one 2-methylimidazole, bidentate orotate and aqua ligands. The orotate coordinated to the metal(II) ions through deprotonated nitrogen atom of pyrimidine ring and oxygen atom of carboxylate group as a bidentate ligand. The antimicrobial activities of 1 and 4 were found to be more active gram (+) than gram (−) and 4 could be use for treatment Staphylococcus aureus.     

Kinetic Analysis of Thermogravimetric Data XXXII. DSC Study of Some [Co(Diox·H)2(amine)2]X and H[Co(Diox·H)2(N3)2] Type Complexes with Alicyclic α-dioximes

14 mixed Co(III) dioximine chelates of the types [Co(Diox·H)₂(amine)₂]X (X = Br, I, NO₃, ClO₄) and H[Co(Diox·H)₂(N₃)₂], respectively (Diox·H₂-1,2-cyclohexane dione dioxime (nyoxime), 1,2-cycloheptane dione dioxime (heptoxime) 1,2-cyclooctane dione dioxime (octoxime) were obtained and their thermal decompositions were studied in an argon atmosphere. After the dehydration of the crystallohydrates, both types of complexes exhibit 3 decomposition stages. For the [Co(Diox·H)₂(amine)₂]X type complexes (X = Br, I) the first endothermal stage is the substitution of an amine molecule for the external sphere anion and this process is followed by two exothermal decomposition stages. With H[Co(Diox·H)₂(N₃)₂] type complexes the first and third processes are relatively slow, but the second process is very fast, corresponding to a vertical portion of the TG curves. From the TG curves kinetic parameters were derived for 11 processes and the validity of a non-linear compensation law was observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Zur Darstellung und Reaktivität von Tetraalkylcyclobutadienplatin(II)-Komplexen [PtCl2(C4R4)L]

Preparation and Reactivity of Platinumcyclobutadiene Complexes [PtCl₂(C₄R₄)L] H[PtCl₃(C₄H₈)], prepared by reduction of H₂[PtCl₆] with n-butanol reacts with 2-pentyne to give equal amounts of the regioisomers [PtCl₂(C₄Et₂Me₂)] ( 3 a, 3 b ). An equimolar mixture of 2-butyne/3-hexyne reacts under the same conditions to give [PtCl₂(C₄Me₄)] ( 1 ), [PtCl₂(C₄Et₄)] ( 2 ) and [PtCl₂(C₄Et₂Me₂)] ( 3 a ) in a molar ratio 1:1.3:6.6. 1 and 2 react with ligands L (L = py a , p-tol b , PPh₃ c , AsPh₃ d , SbPh₃ e ) to give complexes of the type [PtCl₂(C₄R₄)L]. The complexes were characterized by microanalysis as well as by i.r., ¹H- and ¹³C-n.m.r. spectroscopy.     

Kinetic studies on the reactions of some tetrakis(arylisocyanide)cobalt(II) complexes with pyridine in 2,2,2-trifluoroethanol

The interaction of pyridine with four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR)₄(ClO₄)₂] R = 2,6-Me₂C₆H₃ (A), 2,4,6-Me₃C₆H₂ (B), 2,6-Et₂C₆H₃ (C) and 2,6-iPr₂C₆H₃ (D), have been studied in 2,2,2-trifluoroethanol medium. The kinetics of the reactions were investigated over the 293–318 K temperature range. The reaction profile exhibited two distinct processes, proposed to be an initial fast substitution followed by a slow reduction, for each of the reactions. The pseudo first-order rate constants for both processes increased with increasing concentration of pyridine with the reduction processes exhibiting saturation kinetics at high pyridine concentrations. Steric hindrance plays a significant role in the rates of the reactions, as the rates decrease in the order k(A) > k(B) > k(C) > k(D). The activation enthalpies, ΔH^‡, increase from A to D while the activation entropies, ΔS^‡, are relatively similar for the four reactions, indicating similar transition states and hence similar mechanisms. Complex B was first synthesized and characterized in this study.     

Synthese,Struktur und Photochemie von Olefiniridium(I)‐Komplexen mit Acetylacetonatoliganden

Synthesis, Structure, and Photochemical Behavior of Olefine Iridium(I) Complexes with Acetylacetonato Ligands The bis(ethene) complex [Ir(κ²‐acac)(C₂H₄)₂] ( 1 ) reacts with tertiary phosphanes to give the monosubstitution products [Ir(κ²‐acac)(C₂H₄)(PR₃)] ( 2 – 5 ). While 2 (R = iPr) is inert toward PiPr₃, the reaction of 2 with diphenylacetylene affords the π‐alkyne complex [Ir(κ²‐acac)(C₂Ph₂)(PiPr₃)] ( 6 ). Treatment of [IrCl(C₂H₄)₄] with C‐functionalized acetylacetonates yields the compounds [Ir(κ²‐acacR^1,2)(C₂H₄)₂] ( 8 , 9 ), which react with PiPr₃ to give [Ir(κ²‐acacR^1,2)(C₂H₄)(PiPr₃)] ( 10 , 11 ) by displacement of one ethene ligand. UV irradiation of 5 (PR₃ = iPr₂PCH₂CO₂Me) and 11 (R² = (CH₂)₃CO₂Me) leads, after addition of PiPr₃, to the formation of the hydrido(vinyl)iridium(III) complexes 7 and 12 . The reaction of 2 with the ethene derivatives CH₂=CHR (R = CN, OC(O)Me, C(O)Me) affords the compounds [Ir(κ²‐acac)(CH₂=CHR)(PiPr₃)] ( 13 – 15 ), which on photolysis in the presence of PiPr₃ also undergo an intramolecular C–H activation. In contrast, the analogous complexes [Ir(κ²‐acac)(olefin)(PiPr₃)] (olefin = (E)‐C₂H₂(CO₂Me)₂ 16 , (Z)‐C₂H₂(CO₂Me)₂ 17 ) are photochemically inert.     

tris-(Benzimidazol-2-yl-methyl)-amine as a Versatile Building Block in Ru(II) Polypyridyl Chemistry

Summary.  tris-(Benzimidazol-2-yl-methyl)-amine, H₃ ntb, was prepared and used in the synthesis of dinuclear Ru(II) polypyridyl and polynuclear Ru(II)–Co(III) complexes of the type [Ru₂(H₂ ntb) (bpy)₄]³⁺, [Ru₂(Hntb)(phen)₄]²⁺, [(Ru₂(H₂ ntb)(bpy)₄)₂Co(en)₂]⁹⁺, and [(Ru₂(Hntb)(phen)₄)₂ Co(en)₂]⁷⁺ (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, en = 1,2-diaminoethane). The complexes were characterized by elemental analysis as well as spectroscopic and redox data. The luminescent properties of the complexes were also studied. The complexes showed significant antitumour and anti-HIV activities. Received May 9, 2001. Accepted (revised) June 7, 2001     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

Steric and Electronic Influences in Os3(CO)11(PR3) Structures

The structures of Os₃(CO)₁₁(PR₃) with R=F, OPh, Et, p-C₆H₄Me, o-C₆H₄Me, p-C₆H₄(CF₃) and C₆H₁₁, and with PR₃=P(OCH₂)₃CMe have been determined. The Os–Os bond lengths in these compounds are compared to the Os–Os lengths for the other structures of Os₃(CO)₁₁(PR₃) clusters reported in the literature. In most cases, the Os–Os bond length remote from the P ligand [range, 2.8666(4)–2.9044(4) Å] and that in the pseudo-trans position [range, 2.8712(5)–2.900(1) Å] show little variation as the steric and electronic properties of the P ligand are varied. The Os–Os length cis to PR₃ shows more variation [range, 2.879(1)–2.9429(4) Å] and is sensitive to both the size and the -donor/-acceptor properties of the PR₃ ligand: larger or better donor PR₃ ligands cause an increase in the Os–Os bond length. The Os–P distances [range, 2.15(2)–2.478(1) Å] show a similar dependence on the steric and electronic properties of the PR₃ ligand.