Vanadium Alkylidyne Initiated Cyclic Polymer Synthesis: The Importance of a Deprotiovanadacyclobutadiene Moiety

作者：Mehrafshan G. Jafari, John B. Russell, Hanna Lee, Bimal Pudasaini, Digvijayee Pal, Zhihui Miao, Michael R. Gau, Patrick J. Carroll, Brent S. Sumerlin, Adam S. Veige, Mu‐Hyun Baik, Daniel J. Mindiola · 发表于：Journal of the American Chemical Society · 年份：2024 · DOI：10.1021/jacs.3c08149 · 被引用次数：20 · 研究领域：Synthetic Organic Chemistry Methods、Organometallic Complex Synthesis and Catalysis、Oxidative Organic Chemistry Reactions

Reported is the catalytic cyclic polymer synthesis by a 3d transition metal complex: a V(V) alkylidyne, [(dBDI)V≡C t Bu(OEt 2 )] ( 1–OEt 2 ), supported by the deprotonated β-diketiminate dBDI 2– (dBDI 2– = ArNC(CH 3 )CHC(CH 2 )NAr, Ar = 2,6- i Pr 2 C 6 H 3 ). Complex 1–OEt 2 is a precatalyst for the polymerization of phenylacetylene (PhCCH) to give cyclic poly(phenylacetylene) ( c -PPA), whereas its precursor, complex [(BDI)V≡C t Bu(OTf)] ( 2–OTf; BDI – = [ArNC(CH 3 )] 2 CH, Ar = 2,6- i Pr 2 C 6 H 3, OTf = OSO 2 CF 3 ), and the zwitterion [((C 6 F 5 ) 3 B–dBDI)V≡C t Bu(OEt 2 )] ( 3–OEt 2 ) exhibit low catalytic activity despite having a neopentylidyne ligand. Cyclic polymer topologies were verified by size-exclusion chromatography (SEC) and intrinsic viscosity studies. A component of the mechanism of the cyclic polymerization reaction was probed by isolation and full characterization of 4- and 6-membered metallacycles as model intermediates. Metallacyclobutadiene (MCBD) and deprotiometallacyclobutadiene (dMCBD) complexes (dBDI)V[C( t Bu)C(H)C( t Bu)] ( 4– t Bu ) and (BDI)V[C( t Bu)CC(Mes)] ( 5–Mes ), respectively, were synthesized upon reaction with bulkier alkynes, t Bu– ( t BuCCH) and Mes–acetylene (MesCCH), with 1–OEt 2 . Furthermore, the reaction of the conjugate acid of 1–OEt 2, [(BDI)V≡C t Bu(OTf)] ( 2–OTf ), with the conjugated base of phenylacetylene, lithium phenylacetylide (LiCCPh), yields the doubly deprotio-metallacycle complex, [Li(THF) 4 ]{(BDI)V[C(Ph)CC( t Bu)C...