Ethynylgold(I) complexes

Reactions between R₃PAuCl, NaOEt, and HCCR′ under mild conditions produce R₃PAuCCR′ in excellent yield. When R′ = H, a second step leading to the formation of R₃PAuCCAuPR₃ can take place. Exchange reactions of ethynyl for chloride between the ethynylgold complexes and HgCl₂, cis-[PtCl₂L₂cis-[PtCl₂(CO)L], and R₂″PAuCl have been monitored, revealing R₃PAuCCR′ to be useful alkynylating agents. In the reaction with cis-[PtCl₂(CO)L], the first substitution step is non-specific.     

Halonickel(I) complexes

Summary The reduction of nickel(II) halides with NaBH₄ in the presence of different ligands, L=PPh₃, AsPh₃, SbPh₃, has been studied. With a molar ratio L/Ni=3, new complexes NiX(SbPh₃)₃, X=Cl, Br, I, were obtained. With a molar ratio L/Ni=2, dimeric species [NiXL₂]₂, X=Cl, Br, I; L=PPh₃, AsPh₃, SbPh₃, were isolated. They are unstable and decompose easily in the solid and rapidly in solution, so that pure samples were only identified for X=Cl, L=PPh₃, AsPh₃, SbPh₃; X=Br, L=PPh₃ and X=I, L=PPh₃. With a molar ratio L/Ni=1, complexes [NiXL]_n (probably polymeric) were obtained. They are very unstable and pure samples could only be isolated when X=Cl, L=PPh₃. Impure substances containing variable amounts of decomposition products were obtained in all the remaining cases. The chemical and structural behaviour of these complexes is discussed.     

Bis-thallium(I) porphyrin complexes

Treatment of octaethylporphyrin ($\text{1}$) or tetraphenylporphyrin ($\text{2}$) with more than two equiv of thallium(I) ethoxide gives the corresponding stable bis[thallium(I)] porphyrin complexes ($\text{5}$) and ($\text{6}$), respectively; these thallium(I) porphyrins are shown to have very different chemical and spectroscopic properties than do the corresponding thallium(III) porphyrin complexes.     

Silver(I) and gold(I) complexes of rhodanine

Summary Some rhodanine (HL) complexes of silver(I) and gold(1) have been prepared and studied by conductivity measurements and by i.r. spectroscopy. Structures for the complexes are proposed.     

Photosensitive azobispyridine gold(I) and silver(I) complexes

The neutral and cationic dinuclear gold(I) compounds [(μ-N-N)(AuR)(2)] (N-N = 2,2'-azobispyridine (2-abpy), 4,4'-azobispyridine (4-abpy); R = C(6)F(5), C(6)F(4)OC(12)H(25)-p, C(6)F(4)OCH(2)C(6)H(4)OC(12)H(25)-p) and [(μ-N-N){Au(PR(3))}(2)](CF(3)SO(3))(2) (N-N = 2-abpy, 4-abpy, R = Ph, Me) have been obtained by displacement of a weakly coordinated ligand by an azobispyridine ligand. The corresponding silver(I) dinuclear [(μ-2-abpy){Ag(CF(3)SO(3))(PPh(3))}(2)] and polynuclear [{Ag(CF(3)SO(3))(4-abpy)}(n)] compounds have been obtained. The molecular structures of [(μ-2-abpy){Au(PPh(3))}(2)](CF(3)SO(3))(2) and [(μ-4-abpy){Au(PMe(3))}(2)](CF(3)SO(3))(2) have been confirmed by X-ray diffraction studies and feature linear gold(I) centers coordinated by pyridyl groups, and non-coordinated azo groups. In contrast the X-ray structure of [(2-abpy){Ag(CF(3)SO(3))(PPh(3))}(2)] shows tetracoordinated silver(I) centers involving chelating N-N coordination by pyridyl and azo nitrogen atoms. The gold(I) compounds with a long alkoxy chain do not behave as liquid crystals, and decompose before their melting point. The soluble gold(I) derivatives are photosensitive in solution and isomerize to the cis azo isomer under UV irradiation, returning photochemically or thermally to the most stable initial trans isomer. The silver(I) derivative [(2-abpy){Ag(CF(3)SO(3))(PPh(3))}(2)] also photoisomerizes in solution under UV irradiation, showing that its solid state structure, which would block isomerization by azo coordination, is easily broken. These processes have been monitored by UV-vis absorption and (1)H NMR spectroscopy. All these compounds are non-emissive in the solid state, even at 77 K.     

Mesomorphic complexes of rhenium(I) and manganese(I)

Abstract

Following our discovery of liquid crystals based on octahedral manganese(I), we have now extended these studies to the synthesis of what we believe to be unique examples of mesomorphic rhenium-based complexes. These complexes offer advantages over the related manganese(I) systems in that they are more thermally stable. Further, modification of the organic backbone has led to lower melting manganese materials.     

Electronic structures of organo-transition-metal complexes I. Silver(I)-Olefin complexes

By using the closed-shell SCF-MO method with the CNDO type approximation for all valence electron systems, the electronic structures of some Ag⁺-olefin complexes are investigated. The calculated values of -H increase with the increasing number of methyl groups on the double bond and this trend agrees with the experimental result. Also calculation reproduces many experimental results, such as the infrared, Raman, and¹³C NMR spectra. These experimental results are discussed on the basis of the calculated electronic structures of Ag⁺-olefin complexes.     

Bimetallic catalysis involving dipalladium(I) and diruthenium(I) complexes

Dipalladium(I) and diruthenium(I) compounds bridged by two [{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene (L) ligands have been synthesized. The X-ray structures of [Pd(2)L(2)][BF(4)](2) (1) and [Ru(2)L(2)(CO)(4)][BF(4)](2) (2) reveal dinuclear structures with short metal-metal distances. In both of these structures, naphthyridine bridges the dimetal unit, and the site trans to the metal-metal bond is occupied by weakly coordinating oxygen from the amido fragment. The catalytic utilities of these bimetallic compounds are evaluated. Compound 1 is an excellent catalyst for phosphine-free, Suzuki cross-coupling reactions of aryl bromides with arylboronic acids and provides high yields in short reaction times. Compound 1 is also found to be catalytically active for aryl chlorides, although the corresponding yields are lower. A bimetallic mechanism is proposed, which involves the oxidative addition of aryl bromide across the Pd-Pd bond and the bimetallic reductive elimination of the product. Compound 1 is also an efficient catalyst for the Heck cross-coupling of aryl bromides with styrenes. The mechanism for aldehyde olefination with ethyl diazoacetate (EDA) and PPh(3), catalyzed by 2, has been fully elucidated. It is demonstrated that 2 catalyzes the formation of phosphorane utilizing EDA and PPh(3), which subsequently reacts with aldehyde to produce a new olefin and phosphine oxide. The efficacy of bimetallic complexes in catalytic organic transformations is illustrated in this work.     

Copper(I) complexes of rhodanine

Summary Some new crystalline copper(I) complexes of rhodanine (HL) have been prepared and studied by i.r. and conductometric methods. The neutral ligand is bonded to the metal atom through the thiocarbonylic sulphur atom. The Cu(HL)₂OH · 0.5 H₂O complex has a dimeric tetrahedral hydroxyl-bridged structure as have the isostructural halides Cu(HL)₂X (X = Cl, Br and I) for which the halide-bridged stretching bands have been identified. The Cu(HL)₃A (A = ClO₄, BF₄, 0.5 SO₄ and CF₃CO₂) complexes have monomeric distorted tetrahedral structures with the anion bonded to the metal.     

Tetraphosphinite resorcinarene complexes: silver(I) capsule complexes

Resorcinarene tetraphosphinite ligands, P4, react with silver(I) trifluoroacetate or silver(I) triflate, AgX, to give the corresponding [Ag4X4(P4)] complexes. The resorcinarene skeleton in these complexes adopts a boat conformation with the silver(I) phosphinite units on the horizontal, rather than the upright, arene units of the resorcinarene. The [Ag4X4(P4)] complexes react with free P4 ligand to yield the [Ag2X2(P4)] or [AgX(P4)] complexes, which are characterized in solution by NMR spectroscopy to have a conformation opposite to that of the [Ag4X4(P4)] complexes; the silver(I) phosphinite groups are on the upright arene rings of the resorcinarene "boat" instead of the horizontal arene units. There is an easy equilibrium between these complexes. When X = triflate, the [Ag4X4(P4)] complexes disproportionate and add aqua ligands during slow crystallization to give "capsule complexes", which are characterized crystallographically as [Ag10(O3SCF3)10(OH2)6(P4)2], [Ag10(O3SCF3)6(OH2)8(P4)2][O3SCF3]4, or [Ag13(O3SCF3)13(OH2)7(P4)2] depending on the resorcinarene tetraphosphinite ligand P4 used. These unusual capsule complexes are formed by the tail-to-tail self-assembly of pairs of [Ag4(P4)]4+ units linked by additional silver ions that bind to the phenyl substituents of one resorcinarene through {Ag(eta2-C6H5)}+ binding and to the bridging triflate ligands, aqua ligands, or both of the other resorcinarene unit.     

Luminescent rhenium(I)-dipyrrinato complexes

The first Re(I)-dipyrrinato complexes are reported. Complexes with the general formulas fac-[ReL(CO)(3)Cl](-), fac-[ReL(CO)(3)PR(3)], and [ReL(CO)(2)(PR(3))(PR'(3))] have been prepared, where L is one of a series of meso-aryl dipyrrinato ligands. Access to these complexes proceeds via the reaction of [Re(CO)(5)Cl] with the dipyrrin (LH) to produce fac-[ReL(CO)(3)Cl](-). A subsequent reaction with PR(3) (R = phenyl, butyl) leads to displacement of the chloride ligand to generate fac-[ReL(CO)(3)PR(3)], and further reaction with PR'(3) leads to the displacement of the CO ligand trans to the first PR(3) ligand to give trans(P), cis(C)-[ReL(CO)(2)(PR(3))(PR'(3))]. The structures of the complexes were determined in the solid state by X-ray crystallography and in solution by (1)H NMR spectroscopy. Electronic absorption spectroscopy reveals a prominent band in the visible region at relatively low energy (472-491 nm) for all complexes, which is assigned as a π-π* transition of the dipyrrin chromophore. Weak emission (λ(ex) = 485 nm, quantum yields <0.01) was observed for [ReL(CO)(3)Cl](-) and [ReL(CO)(3)PR(3)] complexes, but no emission was generally evident from the [ReL(CO)(2)(PR(3))(PR'(3))] complexes. On the basis of the large Stokes shift (~6000 cm(-1)), the emission is ascribed to phosphorescence from a triplet excited state. The emission intensity is sensitive to dissolved oxygen and methyl viologen; a Stern-Volmer plot in the latter case gave a straight line. Photochemical ligand substitution reactions of [ReL(CO)(3)PR(3)] were induced by excitation with a 355 nm laser in acetonitrile. [ReL(CO)(2)(PR(3))(CH(3)CN)] is formed as a putative intermediate, which reacts thermally with added PR'(3) to produce [ReL(CO)(2)(PR(3))(PR'(3))] complexes.     

Silver(I) complexes of thiourea

Ag^I complexes of thiourea (tu) having the general formula Ag(tu) _x NO₃ (x = 1–4) have been prepared and characterized by elemental analyses, i.r. and n.m.r. (¹H, ¹³C, ¹⁵N and ¹⁰⁷Ag) spectroscopy. Separate i.r. bands were observed for terminal and bridging tu ligands in the complexes. The Ag(tu)NO₃ complex is assumed to be polymeric with all tu groups in the bridging mode. A consistent upfield shift in the ¹³C-n.m.r. chemical shift is observed as the number of tu groups attached to Ag^I increases, whereas the opposite trend is observed for ¹H, ¹⁵N and ¹⁰⁷Ag chemical shifts.     

Aryl- and acetylene-nickel(I) complexes

Reduction of various pentafluorophenylnickel(II) complexes in the presence of phosphines gives unstable nickel(I) compounds but Ni(C₆F₅)(CO)₂(PPh₃)₂ is isolated in the presence of CO. Similar NiR(CO)₂(PPh₃)₂ (R = C₆F₅,C₆Cl₅, 2,3,5,6-C₆Cl₄H) are obtained by reaction of the halogenonickel(I) complex with MgRBr or LiR. Reduction of NiX₂L₂ in the presence of acetylenes gives [NiXL₂]₂(μ-PhCCR) (R = H, X = Cl and R = Ph, X = Cl, Br) when L = P-n-Bu₃ but only NiX(PPh₃)₃ are recovered when L = PPh₃. No reaction with the alkyne is observed for [NiX(PPh₃)₂]_n but [NiCl(PPh₃)]_n reacts with RCCR′ to give paramagnetic NiCl(PPh₃)(CRCR′) (R = Ph, R′= H, COOEt), diamagnetic [NiCl(PPh₃)]₂(μ-PhCCPh) and cyclotrimerization when R = R′ = COOMe. Chemical and structural behaviour of the new nickel(I) complexes is described.     

Gold(I) complexes of thioamides

Summary Gold(I) forms linear [AuL₂]X complexes (X = Cl, Br, I or CIO₄) with thioacetamide and thiobenzamide, AuLX compounds with thiobenzamide (X = CI or Br),N, N-dimethylthioformamide (X = Cl, Br or 1) andN-dimethylthioacetamide (X = CI, Br or 1). Thev(AuS) vibrations are assigned in the 320-260 cm^–1 range. The i.r. spectra further suggest hydrogen bonding between the ligands and the anions. The conductivity measurements indicate dissociation of the [AuL₂]X complexes (X = halide) and coordination of X in solution.Presented in part at the XIX ICCC, Prague, 1978.     

Amino acid dicarbonylrhodium(I) complexes

Summary Dicarhonyrhodium(I) complexes of eleven amino acids were prepared from [AcORh(COD)]₂ and the appropriate amino acid by carboxylato ligand exchange followed by treatment with CO. All complexes are light coloured substances of composition (XY)Rh(CO)₂ (where XYH = amino acid) with square planar geometry andcis-carbonyl ligands, The compounds are transformed by IICI into deep coloured hydrochlorides with more complex structures.COD - 1.5-cycloocladiene.     

Gold(I) complexes of azoles

Summary (Dimethyl sulphide)AuCl reacts with azoles to give adducts [LAuX]₂ [L = N-methylimidazole (N-MeIm), N-ethylimidazole (N-EtIm), N-propylimidazole (N-PrIm), 2-methylbenzoxazole (2-MeBO) and 2,5-dimethylbenzoxazole (2,5-diMeBO); X = Cl or Br] which were characterized analytically and spectroscopically, including ¹H-n.m.r. I.r. and Raman studies showed that the compounds were binuclear with bridging halogen atoms. A nitrogen-containing ligand was coordinated to nitrogen N(3) atom of the azole ring in monodentate fashion.     

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.