Lapenta Rosita, Buonerba Antonio, De Nisi Assunta, Monari Magda, Grassi Alfonso, Milione Stefano, Capacchione Carmine
Department of Chemistry and Biology, University of Salerno , via Giovanni Paolo II, 132 Fisciano, I-84084 Salerno, Italy.
Interuniversity Consortium Chemical Reactivity and Catalysis, CIRCC , via Celso Ulpiani 27, 70126 Bari, Italy.
Inorg Chem. 2017 Mar 20;56(6):3447-3458. doi: 10.1021/acs.inorgchem.6b02987. Epub 2017 Mar 7.
The synthesis and characterization of a series of group 4 metal complexes of general formula {OSSO}M(OR) (X = R = Bu, M = Zr (1); X = cumyl, M = Zr, R = Bu (2); X = cumyl, M = Ti, R = Pr (4); X = cumyl, M = Hf, R = Bu (5)) and {OSSO}Zr (X = Cl (3)) supported by o-phenylene-bridged bis(phenolato) ligands (OSSO-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-di-tert-butyphenol); OSSO-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-bis(2-phenylpropan-2-yl)phenol); OSSO-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-dichlorophenol)) are described herein. Complexes 1-5 were readily obtained by σ-bond metathesis reactions between the proligand and the appropriate homoleptic metal precursor. The reaction with OSSO yielded the bis-ligand complex{OSSO}Zr (3) regardless of the OSSO-H/Zr(OBu) molar ratio or experimental conditions. All complexes were characterized in solution using NMR spectroscopy and, in the case of 2, by single-crystal X-ray diffraction experiments. These complexes show a fac-fac ligand wrapping and a cis relationship between the other two monodentate ligands; zirconium and hafnium complexes 1-3 and 5 are configurationally stable, whereas titanium complex 4 is fluxional in solution at room temperature. The complexes tested in the ring-opening polymerization (ROP) of racemic-lactide showed, except in the case of 3, moderate rates and good levels of polymerization control. Upon addition of an exogenous alcohol (isopropyl alcohol or tert-butyl alcohol) efficient binary catalytic systems were achieved. Polymerizations were well-controlled, as testified by the linear growth of the molecular weight as polymerization proceeded, narrow polydispersity indices, and molecular weights close to those expected on the basis of added alcohol amounts. Experimental and theoretical evidence is provided that ROP reactions operate according to an activated monomer mechanism.
本文描述了一系列通式为{OSSO}M(OR)（X = R = Bu，M = Zr (1)；X = 枯基，M = Zr，R = Bu (2)；X = 枯基，M = Ti，R = Pr (4)；X = 枯基，M = Hf，R = Bu (5)）以及{OSSO}Zr（X = Cl (3)）的第4族金属配合物的合成与表征，这些配合物由邻亚苯基桥连的双（酚盐）配体（OSSO-H = 6,6'-((1,2-亚苯基双（硫烷二基）)双（亚甲基）)双（2,4-二叔丁基苯酚）；OSSO-H = 6,6'-((1,2-亚苯基双（硫烷二基）)双（亚甲基）)双（2,4-双（2-苯基丙烷-2-基）苯酚）；OSSO-H = 6,6'-((1,2-亚苯基双（硫烷二基）)双（亚甲基）)双（2,4-二氯苯酚））支撑。配合物1 - 5可通过前体配体与合适的均配金属前体之间的σ键复分解反应轻松获得。与OSSO的反应无论OSSO-H/Zr(OBu)摩尔比或实验条件如何，都生成双配体配合物{OSSO}Zr (3)。所有配合物在溶液中通过核磁共振光谱进行表征，对于配合物2，还通过单晶X射线衍射实验进行表征。这些配合物呈现出fac - fac配体包裹以及另外两个单齿配体之间的顺式关系；锆和铪配合物1 - 3和5构型稳定，而钛配合物4在室温下在溶液中是易变的。在外消旋丙交酯的开环聚合（ROP）中测试的配合物，除了配合物3的情况外，显示出中等的反应速率和良好的聚合控制水平。加入外源醇（异丙醇或叔丁醇）后，实现了高效的二元催化体系。聚合反应得到良好控制，这通过聚合过程中分子量的线性增长、窄的多分散指数以及接近基于加入醇量预期的分子量得到证明。提供了实验和理论证据表明ROP反应按照活化单体机理进行。
