Alkyne reactions with rhenium(V) oxo alkyl phosphine complexes - phosphine displacement versus apparent Re-P insertion

Zwitterionic Organometallates

“…[23b] 12, [24] or 13, [25] among many others, are stabilized by a non-polar resonance form and often adopt a trans configuration across the CϭC bond.…”

Reactions of [ReOX3(PPh3)2] Complexes (X = Cl, Br) with Phenylacetylene and the Structures of the Products

“…Structurally characterized alkyne complexes of rhenium with the metal in higher oxidation states are still rare 1. Cationic [ReOMe 2 (bipy)( R C≡C R ′)] + complexes were prepared from [ReOMe 2 (bipy)(CH 3 CN)][PF 6 ] and a variety of alkynes 2, whereas reactions of substituted acetylenes with [ReOMe 3 (PMe 3 )] gave the adducts [ReOMe 3 ( R C≡C R ′)] ( R = R ′ = Me, Et, or Ph; R = Me or Ph and R ′ = H) 3. Reduction of the metal ion and formation of unusual rhenium(III) oxo complexes of the composition [ReOI( R C≡C R ′) 2 ] ( R = various alkyl or aryl) was observed with [ReO(I) 3 (AsPh 3 ) 2 ] as precursor 4 Similar reactions with the analogous phosphane complexes [ReO X 3 (PPh 3 ) 2 ] ( X = Cl, Br, I) gave mixtures of products, from which neither the Re III complexes nor other products could be isolated or unambiguously characterized by spectroscopic methods 4.…”

Insertion of alkynes into molybdenum–phosphine and –carbon bonds. Crystal structures of the alkyne–ylide complex [MoO(SC6H2Pri3-2,4,6)2{η2-CHC(tol)}{C(tol)CHPMePh2}] (tol = C6H4Me-4) and the phosphonium–alkylidene complex [MoO(SC6H2Pri3-2,4,6)3{C(Ph)CHC(Ph)CH2PMe2Ph}]

“…The C᎐C distances in the ylide ligands of the above complexes are close to olefin distances (1.34 Å for ethylene): The P᎐C᎐ ᎐ C angle in 2a, 127(3)Њ, is wider than the corresponding angle in the above rhenium complex [124.4(8)Њ]. 10 Thus it is olefinic in nature [122.5(5)Њ] 10 and very similar to the P᎐C᎐ ᎐ C angle in the related manganese complex above [126.9(2)Њ]. 11 The C( 16 Thus the above structural data indicate that compound 2a can be regarded as an ylide complex and its bonding can be represented essentially by two resonance forms, viz.…”

“…In this structure the Mo᎐O bond distance [1.69(2) Å] is similar to the Re᎐O bond distance [1.700(6) Å] in the related compound [ReOR 3 (CHCHPMe 3 )] (R = CH 2 SiMe 3 ). 10 The Mo᎐C (ylide) distance in 2a [2.12(3) Å] is slightly longer than the Mn᎐C distance in the phosphonium ylide complex [Mn- 11 and also longer than the Re᎐C distance [1.996(9) 10 The metal-carbon bonds in the above complexes have distances which are at the long end of the observed range of M᎐ ᎐ C values (1.81-2.02 Å) 12,13 but shorter than M᎐C single bonds (2.01-2.29 Å), 13 indicating that they have some multiple bond character.…”