Improved Access to {[ω-(Phosphanyl)alkyl]cyclopentadienyl}cobalt(I) Complexes: Decomplexation of the Phosphane Arm; Alkyne Complexes; Synthesis of Mononuclear Vinylidenecobalt(I) Complexes

Synthesis and characterization of manganese(ii) complexes supported by cyclopentadienyl-phosphine ligands

A series of manganese(ii) complexes supported by cyclopentadienyl-phosphine ligands have been synthesized and characterized. [LMn(μ-Cl)]₂ served as a precursor to organomanganese(ii) derivatives.

The First Cyclopentadienylalkylphosphane Nickel Chelates: Synthesis, Structures, and Reactions

The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta-4,6-diene with lithium di-tert-butylphosphide was treated with NiCl2 to yield [eta(5):kappa(1)-(di-tert-butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile-stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl- and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper-mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X-ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.

Syntheses and Structures of Sterically Congested Linear and Branched Cobalta[n]triangulanes

Treatment of {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}cobalt(I) chloride (5) with methylenecyclopropane (3) or bicyclopropylidene (4), as well as with their spirocyclopropanated analogues methylenespiropentane (7), cyclopropylidenespiropentane (10), or 7,7'-bi(dispiro[2.0.2.1]heptylidene) (15) in the presence of sodium amalgam at -50 degrees C, furnished the stable cobalt complexes 6, 9, 8, 11, and 16, respectively, in 72, 83, 84, 86, and 54 % isolated yield, respectively. The complexes 14 and 16 were also obtained by ligand exchange of the ethene complex {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}(eta(2)-ethene)cobalt(I) (12) with 13 and 15 in 79 and 52 % yield, respectively. The X-ray crystal-structure analyses of complexes 9, 14, and 16, as well as the NMR-spectroscopic data of all complexes, reveal that they can be regarded as linear and branched cobalta[n]triangulanes. The thermal stability of complexes 6, 8, and 9 up to 109, 145, and 160 degrees C was determined by differential thermal analysis-thermogravimetry (DTA-TG) analysis.

The first cobalt catalyzed [2 + 2 + 2] alkyne cyclotrimerization in aqueous medium at room temperature

Chelate complex 1 (5 mol%) was found to catalyze the [2 + 2 + 2] cyclization of terminal alkynes in good yields in a 80/20 mixture of water and ethanol at room temperature without further activation.

Cobalt-mediated synthesis of angular [4]phenylene: structural characterization of a metallacyclopentadiene(alkyne) intermediate and its thermal and photochemical conversion

[reaction: see text] The first X-ray crystal structure of a mononuclear metallacyclopentadiene(alkyne) complex has been obtained. This type of metallacycle is believed to be the key intermediate in the cobalt-mediated [2 + 2 + 2]cycloaddition of alkynes. Thermal treatment leads to the generation of angular [4]phenylene, the X-ray structural details of which are described. Under photochemical conditions, the cobaltacycle isomerizes to a highly strained (cyclobutadieno)dibenzocyclooctatrienyne complex.

Transition Metal Derivatives of a ((Dimethylamino)ethyl)cyclopentadienyl Ligand. Synthesis and Structures of Amino-Containing Cyclopentadienyl Derivatives of Cobalt(I) and -(III) Including Water-Soluble Compounds

The synthesis of monometallic cobalt(III) and -(I) complexes of ((dimethylamino)ethyl)cyclopentadienyl are reported. The presence of the basic amino group facilitates these synthesis using the corresponding cyclopentadiene complexes as starting material. A cobaltocenium green complex [{eta(5)-C(5)H(4)(CH(2))(2)N(H)Me(2)}(2)Co(III)](3+)(Cl(-))(3) (3) was obtained from C(5)H(5)(CH(2))(2)NMe(2) (1) or from its salt M[C(5)H(4)(CH(2))(2)NMe(2)] (M = Na, Li) (2) upon reaction with Co(II)Cl(2) in THF. The structure of the complex [{(eta(5)-C(5)H(4)(CH(2))(2)NMe(2))(eta(5)-C(5)H(4)(CH(2))(2)N(H)Me(2))}Co(I)(II)](PF(6))(2) (4), prepared from 3 by treatment with NH(4)PF(6) in aqueous solutions, was solved in the triclinic space group P&onemacr; with one molecule in the unit cell, the dimensions of which were a = 6.314(2) Å, b = 7.137(2) Å, c = 13.452(2) Å, alpha = 103.66(2) degrees, beta = 90.25(2) degrees, gamma = 92.89(2) degrees, and V = 588.2(3) Å(3). Adjacent molecules in the unit cell of 4 are hydrogen bonded via a H(+) through their -NMe(2) side chains. The reaction of Co(2)(CO)(8) with C(5)H(5)(CH(2))(2)NMe(2) (1) leads to the formation of [{eta(5)-C(5)H(4)(CH(2))(2)NMe(2)}Co(I)(CO)(2)] (5). Treatment of 5 with HBF(4) in ether solutions yielded [{eta(5)-C(5)H(4)(CH(2))(2)N(H)Me(2)}Co(I)(CO)(2)](+)BF(4)(-) (6). Oxidation of 5 with I(2) or Cl(2) gas yielded [{eta(5)-C(5)H(4)(CH(2))(2)NMe(2)}Co(III)I(2)] (7a) and [{eta(5)-C(5)H(4)(CH(2))(2)NMe(2)}Co(III)Cl(2)] (7b). Addition of HBF(4) to complex 7a resulted in the breaking of the Co(III)-NMe(2) bond, producing the dimeric complex [{(eta(5)-C(5)H(4)(CH(2))(2)N(H)Me(2))Co(III)I(2)}(2)](2+)(BF(4)(-))(2) (9). The bridged diiodo dimer 10, [{(eta(5)-C(5)H(4)(CH(2))(2)NMe(2))CoI}(2)](2+)(BF(4)(-))(2), on the other hand, could be obtained from complex 7a upon addition of AgBF(4) in CH(2)Cl(2).