Diborane(6) and Its Analogues Stabilized by Mono-, Bi-, and Trinuclear Group 7 Templates Combined Experimental and Theoretical Studies
Résumé
Irradiation of [Re(CO)] in the presence of BH·thf resulted in the formation of several rhenium diborane(6) species, for example, [{(OC)Re}{Re(CO)}(μ-η:η:η-BH)(μ-H)], ; [{(OC)Re}{Re(CO)}(μ-η:η:η-BH)(μ-H)], ; and [{(OC)Re}(μ-η:η-BH)], , comprising diverse coordination modes of the [BH] ligand. Compound contains a tris(bidentate) [BH] unit, whereas consists of an unsymmetrically bound [μ-η:η:η-BH] ligand. In contrast, the irradiation of [Mn(CO)] with BH·thf yielded only the Mn analogue of , [{(OC)Mn}{Mn(CO)}(μ-η:η:η-BH)(μ-H)], . In an attempt to generate the bimetallic Mn-diborane(6), we have carried out the reaction of with PCy under photolytic conditions. The reaction led to the formation of two single base stabilized unsymmetrical diborane(5) species, [{Mn(CO)}{Mn(CO)PCy}(μ-η:η-BH·PCy)(μ-H)], , and [{Mn(CO)PCy}(η-BH·PCy)], . As [BH] and [BH·PCy] are isoelectronic, the bondings in and are analogous to that of diborane(6) species -. All the new species have been characterized spectroscopically, and their structures were further confirmed by single-crystal X-ray diffraction studies. DFT-type quantum chemical calculations were carried out that provided insight into the bonding interaction of [BH] and [BH·PCy] with the M(CO) fragments.