Synthesis, characterization, and crystal structure of bis(triphenylphosphine)iminium carbidoheneicosacarbonyl(triphenylphosphite)heptarhenate(1-). Illustration of a polar intermediate stage in cluster decapping

Methylene Complexes of Higher Nuclearity Clusters: [PPN][Re7C(CO)21(.mu.-CH2)] and [PPN]2[Re6C(CO)18(.mu.-CH2)]

“…The sharp signal at lowest field corresponds to the carbonyl ligands bonded to the capping rhenium atom (e). 6 The specific assignments of sets d and a are not individually definitive but correspond to previous assignments for [Re7C(CO)22]-. 6 The carbonyls flanking the bridging methylene (set b) clearly have a significant barrier to local 3-fold rotation, and intemuclear steric interactions with set c may increase its barrier as well.…”

“…* 1•2 A particularly promising method for relatively robust anionic clusters is "oxidative substitution," viz., two-electron oxidation coupled with addition of an electron pair donor. [2][3][4][5][6] In particular, [Re7C(CO>2i]3has been found to react with either carbon monoxide or triphenyl phosphite upon oxidation to give [Re7C(CO)22l-5 or [Re7C(CO)2iP(OPh)3l-,6 respectively. We report here that an oxidative substitution reaction of [Re7C(CO)2i]3with diazomethane provides [Re7C(CO)2i(//-CH2)]-and that "decapping" the latter compound provides also [Re6C(CO)i8(/<-CH2)]2-.…”

Low-valent Organorhenium Compounds

“…51 Further reaction of (11) with ynamine at 68 °C gives dinuclear metallacyclopentadiene products (12), resulting from head-to-head, head-to-tail, and tail-to-tail coupling of two ynamines (Scheme 2). Reduction of (11) with H 2 (10 atm, 70 Reaction of [Re 2 (CO) 9 (NCMe)] with electrophilic alkynes results in alkyne insertion into the rhenium-rhenium bond to give dimetallated alkene complexes (14) (Equation (3)). 54 The reaction is proposed to occur by initial alkyne substitution for the nitrile ligand, migration of the a-carbon to the adjacent rhenium, cleavage o f the metal-metal bond and coordination of the ester oxygen.…”

“…As such, the complex may represent a polar intermediate in cluster-decapping reactions. 70 Reaction of the trianion (21) with acids gives a 44% yield of the monohydride [Re 7 (H)(C)(CO) 21 ] 2 ", which exists as a mixture of two isomers in solution. 71 On the basis of x-ray data, one isomer appears to have the hydride ligand bridging an edge of the basal triangle, whereas the less symmetric isomer has the hydride at an interlayer edge.…”

“…Decomplexation results from treatment with acid to give the unsaturated organic esters. Metallacycle formation is proposed to occur by oxidative addition o f the alkyne C-H bond to give a seven-coordinate rhenium acetylide hydride, which rearranges to a vinylidene intermediate (70) (Equation (19)). Rearrangement o f the carbon-bound enolate to an oxygen-bound enolate and attack at the electrophilic vinylidene a-carbon then generates the metallacycle.…”