Camerano José A, Casado Miguel A, Ciriano Miguel A, Tejel Cristina, Oro Luis A
Departamento de Química Inorgánica, Instituto de Ciencias de Materiales de Aragón, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
Chemistry. 2008;14(6):1897-905. doi: 10.1002/chem.200701209.
Although the pentacoordinated complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(cod)] (1; pz=pyrazolyl, cod=1,5-cyclooctadiene), isolated from the reaction of [{Ir(mu-Cl)(cod)}(2)] with [Li(tmen)][B(allyl)(CH(2)PPh(2))- (pz)(2)] (tmen=N,N,N',N'-tetramethylethane-1,2-diamine), shows behavior similar to that of the related hydridotris(pyrazolyl)borate complex, the carbonyl derivatives behave in a quite different way. On carbonylation of 1, the metal--metal-bonded complex [(Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}CO)(2)(mu-CO)] (2) that results has a single ketonic carbonyl bridge. This bridging carbonyl is labile such that upon treatment of 2 with PMe(3) the pentacoordinated Ir(I) complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PMe(3))] (3) was isolated. Complex 3 shows a unique fac coordination of the hybrid ligand with the allyl group eta(2)-bonded to the metal in the equatorial plane of a distorted trigonal bipyramid with one pyrazolate group remaining uncoordinated. This unusual feature can be rationalized on the basis of the electron-rich nature of the metal center. The related complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PPh(3))] (4) was found to exist in solution as a temperature-dependent equilibrium between the cis-pentacoordinated and trans square planar isomers with respect to the phosphorus donor atoms. Protonation of 3 with different acids is selective at the iridium center and gives the cationic hydrides [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PMe(3))]X (X=BF(4) (5), MeCO(2) (6), and Cl (7)). Complex 7 further reacts with HCl to generate the unexpected product [Ir(CO)Cl{(Hpz)B(CH(2)PPh(2))(pz)CH(2)CH(Me)}(PMe(3))]Cl (9; Hpz=protonated pyrazolyl group) formed by the insertion of the hydride into the Ir-(eta(2)-allyl) bond. In contrast, protonation of complex 4 with HCl stops at the hydrido complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PPh(3))]Cl (8). X-ray diffraction studies carried out on complexes 2, 3, and 9 show the versatility of the hybrid scorpionate ligand in its coordination.
尽管从[{Ir(μ-Cl)(cod)}₂]与[Li(tmen)][B(allyl)(CH₂PPh₂)(pz)₂]（tmen = N,N,N',N'-四甲基乙烷-1,2-二胺）的反应中分离得到的五配位配合物[Ir{(allyl)B(CH₂PPh₂)(pz)₂}(cod)]（1；pz = 吡唑基，cod = 1,5-环辛二烯）表现出与相关氢化三(吡唑基)硼酸配合物相似的行为，但羰基衍生物的行为却截然不同。对1进行羰基化反应时，生成的金属-金属键合配合物[(Ir{(allyl)B(CH₂PPh₂)(pz)₂}CO)₂(μ-CO)]（2）具有单个酮式羰基桥。这种桥连羰基不稳定，以至于用PMe₃处理2时，可分离得到五配位Ir(I)配合物[Ir(CO){(pz)B(η²-CH₂CH=CH₂)(CH₂PPh₂)(pz)}(PMe₃)]（3）。配合物3显示出杂化配体独特的面式配位，烯丙基以η²键合到金属上，位于扭曲三角双锥赤道平面，其中一个吡唑酸根仍未配位。基于金属中心富电子的性质，可以解释这种不寻常的特征。发现相关配合物[Ir(CO){(pz)B(η²-CH₂CH=CH₂)(CH₂PPh₂)(pz)}(PPh₃)]（4）在溶液中以顺式五配位和反式平面正方形异构体之间的温度依赖性平衡存在，这取决于磷供体原子。用不同的酸对3进行质子化反应在铱中心具有选择性，得到阳离子氢化物[Ir{(allyl)B(CH₂PPh₂)(pz)₂}(CO)H(PMe₃)]X（X = BF₄（5）、MeCO₂（6）和Cl（7））。配合物7进一步与HCl反应生成意外产物[Ir(CO)Cl{(Hpz)B(CH₂PPh₂)(pz)CH₂CH(Me)}(PMe₃)]Cl（9；Hpz = 质子化吡唑基），它是由氢化物插入Ir-(η²-烯丙基)键形成的。相比之下，用HCl对配合物4进行质子化反应止于氢化物配合物[Ir{(allyl)B(CH₂PPh₂)(pz)₂}(CO)H(PPh₃)]Cl（8）。对配合物2、3和9进行的X射线衍射研究表明杂化螯合配体在配位方面具有多样性。
