Mononuclear and Dinuclear Copper(I) Complexes of Bis(3,5-dimethylpyrazol-1-yl)methane: Synthesis, Structure, and Reactivity

The synthesis and structures of a mononuclear copper(I) carbonyl complex [Cu(OClO3)(CO)(H2CP

)] (3) and a
dinuclear copper(I) carbonyl complex [{Cu(CO)(H2CP

)}2(μ-pyrazine)](ClO4)2 (4), where H2CP

=
bis(3,5-dimethylpyrazol-1-yl)methane, are described. These two compounds were generated by the carbonylation
of the corresponding copper(I)-acetonitrile complexes, [Cu(H2CP

)(MeCN)](ClO4) (1) and [{Cu(H2CP

)(MeCN)}2(μ-pyrazine)](ClO4)2 (2). Alternatively, treatment of mononuclear 1 and 3, respectively, with pyrazine in a
molar ratio of 2:1 produces the pyrazine-bridged dinuclear CuI complexes 2 and 4. Each of the complexes 1−4 can
react with PPh3 to generate a common three-coordinated copper(I) complex [Cu(PPh3)(H2CP

)](ClO4) (5). The
structures of complexes 1−5 were all confirmed by X-ray crystallography. Comparison of the CuI−C(CO) bond
distances and the CO stretching frequencies of 3 and 4 indicates the back-donating properties of dπ(Cu)−π*(pyrazine)
bonds in 4, and accordingly, stabilizes the mixed-valence species generated from 2. Complex 3, stabilized by the
strong interaction between copper(I) ion and perchlorate counteranion (CuI−O(ClO4) = 2.240(3) Å), is a potential
precursor for polynuclear copper(I) carbonyl complexes.

本研究报道了单核铜(I)羰基配合物[Cu(OClO₃)(CO)(H₂CP)]（编号为配合物3）以及双核铜(I)羰基配合物[{Cu(CO)(H₂CP)}₂(μ-吡嗪)](ClO₄)₂（编号为配合物4）的合成与结构表征，其中缩写H₂CP指代双(3,5-二甲基吡唑-1-基)甲烷（bis(3,5-dimethylpyrazol-1-yl)methane）。上述两种配合物均可通过对应的铜(I)-乙腈配合物经羰基化反应制得：分别为单核配合物[Cu(H₂CP)(MeCN)](ClO₄)（配合物1）以及双核桥联配合物[{Cu(H₂CP)(MeCN)}₂(μ-吡嗪)](ClO₄)₂（配合物2）。此外，以摩尔比2:1分别向单核配合物1和单核配合物3中加入吡嗪时，同样可以得到吡嗪桥联双核铜(I)配合物2和4。配合物1至4均可与三苯基膦（PPh₃）发生反应，得到同一种三配位铜(I)配合物[Cu(PPh₃)(H₂CP)](ClO₄)（配合物5）。配合物1~5的分子结构均经X射线单晶衍射得以确认。通过比较配合物3与配合物4中的Cu(I)-C(CO)键长以及CO伸缩振动频率，可以发现配合物4中存在dπ(Cu)-π*(吡嗪)键的反馈π配位特性，借此可稳定由配合物2原位生成的混合价态物种。配合物3凭借铜(I)阳离子与其抗衡阴离子高氯酸根之间形成的强相互作用（Cu(I)-O(ClO₄⁻)键长为2.240(3) Å）得到稳定，不失为多核铜(I)羰基配合物合成的潜在前驱体。