Insertion protonolysis and photolysis reactivity of a thorium monoalkyl amidinate complex

摘要

The reactivity of the thorium monoalkyl complex Th(CH2SiMe3)(BIMA)3 [>1, BIMA = MeC(NⁱPr)2] with various small molecules is described. While steric congestion prohibits the insertion of N,N′-diisopropylcarbodiimide into the Th–C bond in >1, the first thorium tetrakis(amidinate) complex, Th(BIMA)4 (>2), is synthesized via an alternative salt metathesis route. Insertion of p-tolyl azide leads to the triazenido complex Th[(p-tolyl)NNN(CH2SiMe3)-κ²N^1,2](BIMA)3 (>3), which then undergoes thermal decomposition to the amido species Th[(p-tolyl)N(SiMe3)](BIMA)3 (>4). The reaction of >1 with 2,6-dimethylphenylisocyanide results in the thorium iminoacyl complex Th[η²-(CN)-2,6-Me2-C6H3(CH2SiMe3)](BIMA)3 (>5), while the reaction with isoelectronic CO leads to the products Th[OC(CH₂)SiMe₃](BIMA)₃ (>6) and Th[OC(NⁱPr)C(CH₂SiMe₃)(C(Me)N(ⁱPr))O-κ²O,O′](BIMA)₂ (>7), the latter being the result of CO coupling and insertion into an amidinate ligand. Protonolysis is achieved with several substrates, producing amido (>9), aryloxide (>10), phosphido (>11a,b), acetylide (>12), and cationic (>13) complexes. Ligand exchange with 9-borabicyclo[3.3.1]nonane (9-BBN) results in formation of the thorium borohydride complex (BIMA)₃Th(μ-H)₂[B(C₈H₁₄)] (>14). Complex >1 also reacts under photolytic conditions to eliminate SiMe₄ and produce Th(BIMA)₂(BIMA*) [>15, BIMA* = (ⁱPr)NC(CH₂)N(ⁱPr)], featuring a rare example of a dianionic amidinate ligand. Complexes >2, >3, >5, >6, >11a, and >12–15 were characterized by ¹H and ¹³C{¹H} NMR spectroscopy, FTIR, EA, melting point and X-ray crystallography. All other complexes were identified by one or more of these spectroscopic techniques.