Extreme N⋮N Bond Elongation and Facile N-Atom Functionalization Reactions within Two Structurally Versatile New Families of Group 4 Bimetallic “Side-on-Bridged” Dinitrogen Complexes for Zirconium and Hafnium

Chemical reduction of (η5-C5Me4R)M[N(R‘)C(X)N(R‘)]Cl2 (M = Zr or Hf, X = NMe2 or Me, R = H or Me, R‘ = i-Pr, Et) with 3 equiv of potassium graphite (KC8) in tetrahydrofuran (THF) provides modest isolated yields of the corresponding “side-on-bridged” dinitrogen complexes, {(η5-C5Me4R)M[N(R‘)C(X)N(R‘)]}2(μ-η2:η2-N2) (1−6). Single-crystal X-ray analyses of these compounds provide d(N−N) bond length values of 1.518(2), 1.581(4), 1.600(6), 1.611(4), 1.630(4), and 1.635(5) Å for 1−6, respectively, that correlate with an increasing fold angle of the M2N2 core for an increase in d(N−N). Compounds 1−6 all undergo hydrosilylation and hydrogenation with PhSiH3 and H2 to provide the corresponding N-functionalized products, 7 and 8, resulting from single addition of these reagents at 25 °C. Compounds 5 and 6 reacted with ethylbromide at 25 °C to provide the N-alkylated products 9a and 9b, respectively, while reaction of 5 with 1 equiv of Br2 provided a near quantitative yield of the diazene dibromide 10 which was obtained as a minor co-product in the N-alkylation of 5.

以3当量的石墨酸钾(KC8)在四氢呋喃(tetrahydrofuran, THF)中对(η5-C5Me4R)M[N(R‘)C(X)N(R‘)]Cl2（其中M为锆(Zr)或铪(Hf)，X为二甲氨基(NMe2)或甲基(Me)，R为氢(H)或甲基(Me)，R‘为异丙基(i-Pr)或乙基(Et)）进行化学还原，可获得中等分离收率的相应"侧桥联"双氮配合物{(η5-C5Me4R)M[N(R‘)C(X)N(R‘)]}2(μ-η2:η2-N2)（编号1~6）。对上述化合物开展单晶X射线衍射分析，测得化合物1至6的N-N键长分别为1.518(2)、1.581(4)、1.600(6)、1.611(4)、1.630(4)及1.635(5)埃(Å)，该键长数值与M2N2核的折叠角增大呈现正相关，即随N-N键长增加，M2N2核的折叠角同步升高。化合物1至6均可与苯基硅烷(PhSiH3)和氢气(H2)发生硅氢化反应与氢化反应，在25 ℃下通过这些试剂的单分子加成得到对应的氮官能化产物7和8。化合物5和6在25 ℃下与溴乙烷(ethylbromide)反应，分别得到N-烷基化产物9a和9b；而化合物5与1当量的溴(Br2)反应时，可获得近乎定量收率的二溴二氮烯(10)，该产物在化合物5的N-烷基化反应中仅作为次要副产物生成。