Abstract
The reactions between (mu-eta-6:eta-6-C7H8)[Cr(Nacnac)Dipp]2 (1) and organic azides were investigated and generated a variety of novel complexes. Treatment of p-TolN3 (p-Tol = 4-MeC6H4) with 1 produced not only a bisimido chromium complex, Cr(Nacnac)Dipp(N-p-Tol)2 (4), but a five-membered-ring compound Cr(Nacnac)Dipp[eta-2-(p-Tol)N-N=N-N -(p-Tol)] (5). However, the reaction of 1 with Me3SiN3 resulted in the formation of a three-coordinate amido complex Cr(Nacnac)Dipp(N(SiMe3)2) (6) and an azido bridged complex [Cr(Nacnac)Dipp(mu-eta-1:eta-1-N3)]2 (7). In contrast, treatment of organic azides with its vanadium analog, namely (mu-eta-6:eta-6-C7H8)[V(Nacnac)Dipp]2 (2), afforded a family of four-coordinate bisimido complexes, V(Nacnac)Dipp(NR)2 (R = SiMe3, 8; p-Tol, 9; 1-Ad, 10). While the reaction of 2 with TsN3 (Ts = p-TolSO2) furnished a tetravalent penta-coordinate complex, V(Nacnac)Dipp(O)[eta-2-O-S(O)(p-Tol)-O] (11). These four-coordinate bisimido complexes 8 and 9 are found to be effective catalysts towards the dimerization of aldehydes to form their corresponding carboxylic esters, namely the Tischenko reaction, and the cyclotrimerization of terminal alkynes respectively. Moreover, a series of Ru(II) complexes supported by beta-diketiminate ligand with general formula of Ru(Nacnac)(X)(□6-Ar) (X = H, Cl, OTf; Ar = p-cyemene, p-xylene, toluene; 14-19) were successfully synthesized and fully characterized. Reduction of Ru(Nacnac)Dipp(Cl)(eta-6-p-cymene) (14) with KC8 furnished a novel, low coordinate, half sandwich and monovalent ruthenium complex, Ru(Nacnac)Dipp(eta-6-p-cymene) (20). The univalent Ru(I) complex 20 can promote the C-H bond activation of the coordinated p-cymene ligand and an intermolecular C=C double bond formation through oxidative dehydrogenative coupling of sp3 C-H bond in the presence of strong oxidase. Moreover, the reaction between 20 and NO afforded trinitrosyl complex, Ru(Nacnac)Dipp(NO)3 (25b), a dinuclear ruthenium complex, (mu-eta-1:eta-1-O-N=N-O)[Ru(Nacnac)Dipp(NO)2]2 (25a) with trans-hyponitrite bridged resulted from N-N coupling of two NO ligand, and, of particular interest, an oxo-bridged, amido diruthenium complex, [Ru(Nacnac)Dipp(NH2)(NO)(mu-O)]2 (26), resulted from cleavage of NO. On the other hand, the reaction of 20 with CO, led to the formation of Ru3(CO)12 and Ru(Nacnac)Dipp(H)(CO)2 (29) surprisingly. A series of three-legged piano-stool complexes with formula of [Ru(RCNN)(eta-6-Ar)]Cl (CNN = [(2,6-MeC6H3)N=C(Me)]2CH[(R)C=CH], Ar = toluene, R = Ph, 30a; SiMe3, 30b; Ar = p-cymene, R = Ph, 30c) were successfully synthesized through reaction of Ru(Nacnac)Dmp(eta-6-Ar)Cl (Ar = toluene, 15; p-cymene, 16) with RCCH (R = Ph, SiMe3). Treatment of 30a-c with NaHBEt3 resulted in the nucleophilic addition of the hydride to aromatic CH of coordinated arene and formation of Ru(RCNN)(eta-5-4-X-C6H5Me) (X =H; R = Ph, 31a; R = SiMe3, 31b; X = i-Pr, R = Ph, 31c). Reduction of 30a with KC8, however, gave rise to the dehydrogenation of the Me into CH2 of ligand backbone and afforded the divalent ruthenium complex, Ru(PhCNN)*(eta-6-toluene) (PhCNN* = [(2,6-MeC6H3)N-C=CH2]CH[(2,6-MeC6H3)N=C(Me)] [(R)C=CH], 32). All new complexes presented were structurally characterized by mult-nuclear NMR spectroscopy and X-ray diffraction.