Reactivity differences between 2,4- and 2,5-disubstituted zirconacyclopentadienes: a highly selective and general approach to 2,4-disubstituted phospholes
作者:Guillaume Bousrez、Florian Jaroschik、Agathe Martinez、Dominique Harakat、Emmanuel Nicolas、Xavier F. Le Goff、Jan Szymoniak
DOI:10.1039/c3dt51158h
日期:——
Cp2ZrCl2/lanthanum system. Reactions of dihalophosphines with these mixtures afforded selectively the corresponding 2,4-disubstituted phospholes and 1,4-disubstituted butadienes. A new series of phospholes was characterized by multi-nuclear NMR spectroscopy and X-ray analysis. A possible explanation for the observed selectivity was obtained from X-ray studies and DFT analysis of the intermediate zirconacyclopentadienes
The reaction of ZrCp2(isoprene) with 1-butene, 2-butene, 1-pentene and 2-pentene proceeds with highlyregioselectivecarbon–carbonbondformation between C2-carbon of alkenes and C4-carbon of isoprene unit. In the presence of excess isoprene, the Zr-complex showed catalysis for selective tail-to-tail linear dimerization of isoprene. The addition of diphenylacetylene resulted in the release of isoprene
Reaction of [η5-C5H5)2ZrH(μ-H)]2 with diphenylacetylene: mechanistic and theoretical considerations
作者:Douglas G. Bickley、Nguyen Hao、Peter Bougeard、Brian G. Sayer、Robert C. Burns、Michael J. McGlinchey
DOI:10.1016/s0022-328x(00)98731-x
日期:1983.4
shown by 1H NMR studies to adopt a dimeric structure with bridging and terminal hydride ligands in both benzene-d6 and toluene-d8 solution. The reaction of the zirconium dihydride with diphenylacetylene has been re-investigated and produces a zirconacyclopentadiene complex 7, contrary to literature suggestions of a dimetallic zirconabenzene structure. A qualitative molecularorbital analysis of the
The Cp2ZrCl(mu-1,4-diphenylbutenyne)PX complexes 7a [-P(C6H5)2] and 10 [-P(C6F5)21 insert tertbutylisonitrile into the Zr-C(sp 2) cr bond to yield the N-inside 17 eta(2)-iminoacyl zirconocene complexes 13a and 13b. X-ray crystal structure analysis of complexes 13a and 13b revealed the presence of a chiral atropisomeric structure with a torsion angle of 74.8(2)degrees (13a) and 72.9(6)degrees (13b), respectively, around the central iminoacyl/alkenyl C(sp(2))-C(sp(2)) a bond. In solution an analogous chiral structure is observed. The barrier of interconversion of the enantiomeric atropisomers of 13a and 13b was determined at Delta G(double dagger) (327K) = 14.9 +/- 0.3 kcal mol(-1) (13a) and Delta G(double dagger) (325K) = 14.8 0.3 kcal mol(-1) (13b) by temperature-dependent dynamic NMR spectroscopy. Reaction of 7a and 10 with methyllithium followed by treatment with B(C6F5)3 gave the corresponding cationic zirconocene complexes 12a and 12b. These complexes took up 2 mol equiv of tert-butylisonitrile to yield the cationic N-inside eta(2)-iminoacyl zirconocene systems 14a and 14b as isonitrile adducts. The cationic complexes 14a and 14b are also axially chiral. The barriers of enantiomerization (Delta G(double dagger) (288 K) = 13.1 0 3 kcal mol(-1) (14a), Delta G(double dagger) (293 K) = 13.4 0.3 kcal mol(-1) (14b)) were also determined by dynamic NMR spectroscopy.