Reactivity of the unsaturated anion decacarbonyltetra-μ-hydrido-tri-rhenate(1-) toward phenols. Crystal and molecular structures of the tetraethylammonium salts of the triangular cluster anion [re3(μ-H)3(μ-OC6F5)(CO) 10]- and

full title:Reactivity of the unsaturated anion decacarbonyltetra-μ-hydrido-tri-rhenate(1-) toward phenols. Crystal and molecular structures of the tetraethylammonium salts of the triangular cluster anion [re3(μ-H)3(μ-OC6F5)(CO) 10]- and of the binuclear anion [re2(μ-OC6H5)3(CO) 6]- The reactions of [Re3(μ-H)4(CO)10]- with phenols have been investigated under different conditions. The acidity of phenols is sufficient to abstract one hydride of the Re(μ-H)2 Re system leading to compounds [Re3(μ-H)3(μ-OC6R5)(CO) 10]- (R = H or F) or, under a CO atmosphere, to neutral [Re3(μ-H)3(CO)12]. The NEt4+ salt of the pentafluorophenoxide derivative has been investigated by X-ray analysis. The crystals are monoclinic, space group P21/c, with a = 9.304(1), b = 19.357(3), c = 18.063(3) Å, β = 94.72(1)°, and Z = 4. The structure was solved and refined on the basis of 3 897 significant counter data, to a final R 0.028. The anion contains an isosceles triangle of Re atoms, with two longer hydride-bridged edges [3.215(1) and 3.243(1) Å] and one shorter edge [2.975(1) Å] doubly bridged by a hydride and the phenoxide ligand [Re-O 2.176(5) Å]. Reaction of [Re3(μ-H)4(CO)10]- with an excess of phenol at high temperature leads to cluster degradation, with formation of the binuclear anion [Re2(μ-OC6H5)3(CO) 6]-. The NEt4+ salt of the latter has been studied by single-crystal X-ray analysis: orthorhombic, space group Pc21n (non-standard setting of Pna21), with a = 9.568(1), b = 18.865(3), c = 18.948(3) Å, and Z = 4. The structure solution and refinements were based on 2 168 significant counter data, the final R value being 0.031. The anion contains two Re(CO)3 units, joined through three phenoxide bridges. The mean Re-O bond length is 2.14 Å, and the non-bonding Re ⋯ Re contact is 3.154(1) Å. Pyrolysis in n-heptane of [Re3(μ-H)3(μ-OC6H5)(CO) 10]- gives selectively [Re3(μ-H)3(μ3-OC6H 5)(CO)9]-, in a reaction that is readily reversed under CO at room temperature.