Synthesis, structural characterization and reactivity study of novel twelve-, thirteen, and fourteen-vertex carboranes and their derivatives.

摘要

By introducing a linkage between two cage carbon atoms, C,C'-linked nido-carborane salts Na2[(CH2)nC 2B10H10] (n = 5, 6) and arachno-carborane salts Li4[(CH2)nC2B10H 10] (n = 3, 4) were synthesized. The trimethylene linked carborane 1,2-(CH 2)3-1,2-C2B10H10 is a good starting material for polyhedral expansion reactions. The sequential sodium reduction followed by capitation reaction with RBX2 gave 13-vertex carboranes 3-R-1,2-(CH2)3-1,2-C2B11 H10 in moderate yields. Electrophilic substitution reactions of 1,2-(CH2)3-1,2-C2B11H 11 with suitable electrophiles gave partially substituted products 8,9,10,11,12,13-X 6-1,2-(CH2)3-1,2-C2B11H 5 (X = Me, Br, I). 13-Vertex closo-carboranes can be reduced to form 13-vertex nido-species [(CH2) 3C2B11H10R]2- by groups 1 and 2 metals. Capitation reactions of Na2[(CH2) 3C2B11H11] with dibromoborane or suitable metal halides afforded 14-vertex carborane 2,3-(CH2)3-2,3-C 2B12H12 or metallacarboranes 2,3-(CH2) 3-8-L-8,2,3-NiC2B11H11 (L = dppe, dppen) and 2,3-(CH2)3-1-(p-cymene)-1,2,3-RuC 2B11H11. Reduction of 14-vertex closo -carborane yielded 14-vertex nido-species Na 2[(CH2)3C2B12H12]. It reacted with dibromoborane to afford a new 14-vertex carborane 2,13-(CH 2)3-2,13-C2B12H12, rather than a 15-vertex one. However, a 15-vertex ruthenacarborane 1,4-(CH2 )3-7-(p-cymene)-7,1,4-RuC2B 12H12 was obtained by the capitation reaction of Na 2[(CH2)3C2B12H12] with [(p-cymene)RuCl2]2.;The reaction of Cp2ZrCl2 with Li2C 2B10H10 gave Cp2Zr(mu-Cl)(mu-C 2B10H10)Li(OEt2)2. Its reactivity toward unsaturated polar organic substrates CyN=C=NCy, PhN3, tBuNC, and PhCN resembled that of zirconocene-carboryne complex yielding a series of insertion products. The Zr-carboryne complexes (eta 5-C5Me5)(eta3-C2B 10H10)Zr(mu-Cl)2Li(THF)2, (eta 5-C5Me5)(eta3-C2B 10Me8H2)Zr(mu-Cl)2Li(OEt2) 2, and (eta5-C5Me5)Zr[eta 3-CyNC(Me)NCy](eta3-C2B10H 10) were synthesized by salt metathesis method. Among them, (eta 5-C5Me5)Zr[eta3-CyNC(Me)NCy](eta 3-C2B10H10) was active toward unsaturated polar organic substrates. Some late transition metal-carboryne complexes (PPh 3)2M(eta2-C2B10H 10) (M = Ni, Pd, Pt) were obtained from the reactions of Li2C 2B10H10 with (PPh3)2MCl 2. The ligand substitution reactions of (PPh3)2Ni(eta 2-C2B10H10) with different phosphines were studied, which revealed the labile property of the coordinated PPh 3. Different from the Zr-carboryne complexes, (PPh3) 2Ni(eta2-C2B10H10) showed regioselective [2+2+2] cycloaddition toward less bulky internal alkynes affording highly substituted benzocarboranes.