First-row transition-metal-diborane and -borylene complexes
Abstract
A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}<sub>2</sub>] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH<sub>4</sub>⋅thf at −78 °C, followed by room-temperature reaction with three equivalents of [Mn<sub>2</sub> (CO)<sub>10</sub>] yielded a manganese hexahydridodiborate compound [{(OC)<sub>4</sub>Mn}(η<sup>6</sup>-B<sub>2</sub>H<sub>6</sub>){Mn(CO)<sub>3</sub>}<sub>2</sub> (μ-H)] (1) and a triply bridged borylene complex [(μ<sub>3</sub>-BH)(Cp*Co)<sub>2</sub> (μ-CO)(μ-H)<sub>2</sub>MnH(CO)<sub>3</sub>] (2). In a similar fashion, [Re<sub>2</sub> (CO)<sub>10</sub>] generated [(μ<sub>3</sub>-BH)(Cp*Co)<sub>2</sub>(μ-CO)(μ-H)<sub>2</sub>ReH(CO<sub>)3</sub>] (3) and [(μ<sub>3</sub>-BH)(Cp*Co)<sub>2</sub> (μ-CO)<sub>2</sub> (μ-H)Co(CO)<sub>3</sub>] (4) in modest yields. In contrast, [Ru<sub>3</sub> (CO)<sub>12</sub>] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(μ-H)<sub>3</sub>Ru<sub>3</sub>(CO)<sub>9</sub>B] (5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron–boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using <sup>1</sup>H, <sup>11</sup>B, <sup>13</sup>C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B[BOND]H[BOND]Mn, a weak B[BOND]B[BOND]Mn interaction, and an enhanced B[BOND]B bonding in 1Similar works
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