Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, USA.
Inorg Chem. 2012 Sep 17;51(18):9683-93. doi: 10.1021/ic300923c. Epub 2012 Aug 28.
Unlike some other Ir(III) hydrides, the aminopyridine complex [(2-NH(2)-C(5)NH(4))IrH(3)(PPh(3))(2)] (1-PPh(3)) does not insert CO(2) into the Ir-H bond. Instead 1-PPh(3) loses H(2) to form the cyclometalated species [(κ(2)-N,N-2-NH-C(5)NH(4))IrH(2)(PPh(3))(2)] (2-PPh(3)), which subsequently reacts with CO(2) to form the carbamato species [(κ(2)-O,N-2-OC(O)NH-C(5)NH(4))IrH(2)(PPh(3))(2)] (10-PPh(3)). To study the insertion of CO(2) into the Ir-N bond of the cyclometalated species, a family of compounds of the type [(κ(2)-N,N-2-NR-C(5)NH(4))IrH(2)(PR'(3))(2)] (R = H, R' = Ph (2-PPh(3)); R = H, R' = Cy (2-PCy(3)); R = Me, R' = Ph (4-PPh(3)); R = Ph, R' = Ph (5-PPh(3)); R = Ph, R' = Cy (5-PCy(3))) and the pyrimidine complex [(κ(2)-N,N-2-NH-C(4)N(2)H(3))IrH(2)(PPh(3))(2)] (6-PPh(3)) were prepared. The rate of CO(2) insertion is faster for the more nucleophilic amides. DFT studies suggest that the mechanism of insertion involves initial nucleophilic attack of the nitrogen lone pair of the amide on CO(2) to form an N-bound carbamato complex, followed by rearrangement to the O-bound species. CO(2) insertion into 1-PPh(3) is reversible in the presence of H(2) and treatment of 10-PPh(3) with H(2) regenerates 1-PPh(3), along with Ir(PPh(3))(2)H(5).
与其他一些 Ir(III) 氢化物不同，氨基吡啶配合物 [(2-NH(2)-C(5)NH(4))IrH(3)(PPh(3))(2)] (1-PPh(3)) 不会将 CO(2) 插入 Ir-H 键中。相反，1-PPh(3) 失去 H(2) 形成环金属化物种 [(κ(2)-N,N-2-NH-C(5)NH(4))IrH(2)(PPh(3))(2)] (2-PPh(3))，随后与 CO(2) 反应形成氨基甲酸盐物种 [(κ(2)-O,N-2-OC(O)NH-C(5)NH(4))IrH(2)(PPh(3))(2)] (10-PPh(3))。为了研究 CO(2) 插入环金属化物种中的 Ir-N 键，合成了一系列类型为 [(κ(2)-N,N-2-NR-C(5)NH(4))IrH(2)(PR'(3))(2)] (R = H, R' = Ph (2-PPh(3)); R = H, R' = Cy (2-PCy(3)); R = Me, R' = Ph (4-PPh(3)); R = Ph, R' = Ph (5-PPh(3)); R = Ph, R' = Cy (5-PCy(3))) 和嘧啶配合物 [(κ(2)-N,N-2-NH-C(4)N(2)H(3))IrH(2)(PPh(3))(2)] (6-PPh(3)) 的化合物。亲核性更强的酰胺的 CO(2) 插入速率更快。DFT 研究表明，插入反应的机制涉及酰胺氮孤对电子对 CO(2) 的初始亲核攻击，形成 N 键合的氨基甲酸盐配合物，随后重排为 O 键合的物种。在 H(2) 的存在下，1-PPh(3) 中的 CO(2) 插入是可逆的，用 H(2) 处理 10-PPh(3) 可将其再生为 1-PPh(3)，同时生成 Ir(PPh(3))(2)H(5)。
