Synthesis and Structure of [η⁵-1,2,4-(Me₃Si)₃C₅H₂]₂Th(bipy) and Its Reactivity toward Small Molecules

Abstract

Halide exchange of (Cp^3tms)₂ThCl₂ (<b>1</b>; Cp^3tms = η⁵-1,2,4-(Me₃Si)₃C₅H₂) with Me₃SiI furnishes (Cp^3tms)₂ThI₂ (<b>2</b>), which is then reduced with potassium graphite (KC₈) in the presence of 2,2'-bipyridine to give the thorium bipyridyl metallocene (Cp^3tms)₂Th(bipy) (<b>3</b>) in good yield. Complex <b>3</b> was fully characterized and readily reacted with various small molecules. For example, <b>3</b> may serve as a synthetic equivalent for the (Cp^3tms)₂Th(II) fragment when exposed to CuI, Ph₂S₂, organic azides, and CS₂. Moreover, upon the addition of thiobenzophenone Ph₂CS, <i>p</i>-methylbenzaldehyde (<i>p</i>-MeC₆H₄)CHO, benzophenone Ph₂CO, amidate PhCONH(<i>p</i>-tolyl), seleno-ketone (<i>p</i>,<i>p</i>'-dimethoxy), selenobenzophenone (<i>p</i>-MeOPh)₂CSe, di(<i>p</i>-tolyl)methanimine (<i>p</i>-tolyl)₂C═NH, 1,2-di(benzylidene)hydrazine (PhCH═N)₂, and nitriles PhCN, PhCH₂CN, and Ph₂CHCN C-C coupling results to give (Cp^3tms)₂Th[(bipy)(Ph₂CS)] (<b>8</b>), (Cp^3tms)₂Th[(bipy)(<i>p</i>-MePhCHO)] (<b>9</b>), (Cp^3tms)₂Th[(bipy)(Ph₂CO)] (<b>10</b>), (Cp^3tms)₂Th[(bipy){(<i>p</i>-tolylNH)(Ph)CO}] (<b>11</b>), (Cp^3tms)₂Th[(bipy){(<i>p</i>-MeOPh)₂CSe}] (<b>12</b>), (Cp^3tms)₂Th[(bipy){(<i>p</i>-tolyl)₂CNH}] (<b>13</b>), (Cp^3tms)₂Th[(bipy)(PhCHNN═CHPh)] (<b>14</b>), (Cp^3tms)₂Th[(bipy)(PhCN)] (<b>16</b>), (Cp^3tms)₂Th[(bipy)(PhCH₂CN)] (<b>17</b>), and (Cp^3tms)₂Th[(bipy)(Ph₂CHCN)] (<b>18</b>), respectively. However, when thiazole is added to <b>3</b>, the dimeric sulfido complex [(Cp^3tms)₂Th]₂[μ-(bipy)CH₂NCHCHS]₂ (<b>15</b>) can be isolated. Moreover, the addition of isonitriles such as Me₃CNC and PhCH₂NC to <b>3</b> results in C-N bond cleavage and C-C coupling processes to form the thorium isocyanido amido complexes (Cp^3tms)₂Th[4-(Me₃C)bipy](NC) (<b>19</b>) and (Cp^3tms)₂Th[4-(PhCH₂)bipy](NC) (<b>20</b>), respectively. Nevertheless, upon exposure of <b>3</b> to (trimethylsilyl)diazomethane Me₃SiCHN₂, the bis-amido complex (Cp^3tms)₂Th[5,6-(Me₃SiCH)bipy] (<b>21</b>), concomitant with N₂ release, is isolated.