Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
Inorg Chem. 2012 Mar 5;51(5):3212-9. doi: 10.1021/ic202661n. Epub 2012 Feb 22.
The synthesis and characterization of the mononuclear chromium(II) terphenyl substituted primary amido-complexes Cr{N(H)Ar(Pr(i)(6))}(2) (Ar(Pr(i)(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(i)Pr(3))(2) (1), Cr{N(H)Ar(Pr(i)(4))}(2) (Ar(Pr(i)(4)) = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2) (2), Cr{N(H)Ar(Me(6))}(2) (Ar(Me(6)) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) (4), and the Lewis base adduct Cr{N(H)Ar(Me(6))}(2)(THF) (3) are described. Reaction of the terphenyl primary amido lithium derivatives Li{N(H)Ar(Pr(i)(6))} and Li{N(H)Ar(Pr(i)(4))} with CrCl(2)(THF)(2) in a 2:1 ratio afforded complexes 1 and 2, which are extremely rare examples of two coordinate chromium and the first stable chromium amides to have linear coordinated high-spin Cr(2+). The reaction of the less crowded terphenyl primary amido lithium salt Li{N(H)Ar(Me(6))} with CrCl(2)(THF)(2) gave the tetrahydrofuran (THF) complex 3, which has a distorted T-shaped metal coordination. Desolvation of 3 at about 70 °C gave 4 which has a formally two-coordinate chromous ion with a very strongly bent core geometry (N-Cr-N= 121.49(13)°) with secondary Cr--C(aryl ring) interactions of 2.338(4) Å to the ligand. Magnetometry studies showed that the two linear chromium species 1 and 2 have ambient temperature magnetic moments of about 4.20 μ(B) and 4.33 μ(B) which are lower than the spin-only value of 4.90 μ(B) typically observed for six coordinate Cr(2+). The bent complex 4 has a similar room temperature magnetic moment of about 4.36 μ(B). These studies suggest that the two-coordinate chromium complexes have significant spin-orbit coupling effects which lead to moments lower than the spin only value of 4.90 μ(B) because λ (the spin orbit coupling parameter) is positive. The three-coordinated complex 3 had a magnetic moment of 3.79 μ(B).
单核铬(II)三联苯取代的伯酰胺配合物 Cr{N(H)Ar(Pr(i)(6))}(2)(Ar(Pr(i)(6))=C(6)H(3)-2,6-(C(6)H(2)-2,4,6-(i)Pr(3))(2) (1),Cr{N(H)Ar(Pr(i)(4))}(2)(Ar(Pr(i)(4))=C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2) (2),Cr{N(H)Ar(Me(6))}(2)(Ar(Me(6))=C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) (4)和路易斯碱加合物 Cr{N(H)Ar(Me(6))}(2)(THF)(3)的合成和表征。三联苯伯酰胺锂衍生物 Li{N(H)Ar(Pr(i)(6))}和 Li{N(H)Ar(Pr(i)(4))}与 CrCl(2)(THF)(2)以 2:1 的比例反应,得到了配合物 1 和 2,它们是两配位铬的极罕见例子,也是第一个具有线性配位高自旋 Cr(2+)的稳定铬酰胺。与 CrCl(2)(THF)(2)反应的空间位阻较小的三联苯伯酰胺锂盐 Li{N(H)Ar(Me(6))}得到了四氢呋喃(THF)配合物 3,它具有扭曲的 T 形金属配位。在约 70°C 下脱去 3 的溶剂得到了 4,它具有形式上为两配位的亚铬离子,具有非常强烈弯曲的核心几何形状(N-Cr-N=121.49(13)°),与配体的次级 Cr--C(芳基环)相互作用为 2.338(4)Å。磁测量研究表明,两个线性铬物种 1 和 2 在环境温度下具有约 4.20 μ(B)和 4.33 μ(B)的磁矩,低于通常观察到的六配位 Cr(2+)的自旋仅值 4.90 μ(B)。弯曲的配合物 4 在室温下具有类似的磁矩,约为 4.36 μ(B)。这些研究表明,两配位铬配合物具有显著的自旋轨道耦合效应,导致磁矩低于自旋仅值 4.90 μ(B),因为 λ(自旋轨道耦合参数)为正。三配位配合物 3 的磁矩为 3.79 μ(B)。