Synthesis, Fluxionality, and Propene Insertion Reactions of Zirconium Boryldiene Complexes with Sterically Undemanding Cp Ligands
详细信息 查看全文
- 作者：Marco M. Corradi ; Gerardo Jimé ; nez Pindado ; Mark J. Sarsfield ; Mark Thornton-Pett ; and Manfred Bochmann
- 刊名：Organometallics
- 出版年：2000
- 出版时间：March 20, 2000
- 年：2000
- 卷：19
- 期：6
- 页码：1150 - 1159
- 全文大小：197K
- 年卷期：v.19,no.6(March 20, 2000)
- ISSN：1520-6041
文摘
The reduction of CpRZrCl3(dme) (CpR = Cp (a), C5H4SiMe3 (b), C5H4Me (c), Ind (d)) withsodium amalgam in the presence of isoprene, followed by the addition of allylmagnesiumchloride, gives the diene complexes CpRZr(
3-allyl)(4-isoprene) (2a-d). The preparationsare conveniently carried out as one-pot reactions. The reaction of 2a-d with B(C6F5)3 intoluene solution at -78 
C proceeds quantitatively to give the thermally unstable zwitterioniccomplexes CpRZr(3-allyl){1:3-CH2CMeCHCH2B(C6F5)3} (3a-d), which on warming decompose under C-H activation and propene elimination to give CpRZr(C6F5){4-CH2CMeCHCHB(C6F5)2} (4a-d). The complexes are stabilized by the coordination of one o-Fatom of a boryl-C6F5 ring to the metal center. Compounds 4 are fluxional. The rotation ofthe Zr-C6F5 ligand is influenced by the steric demand of the Cp ligands (
G
= 43-49 kJmol-1), while there is little variation in the rotational barriers of the B-C6F5 substituents(G = ca. 47 kJ mol-1). Recrystallization of 4a from diethyl ether affords the 16-electroncomplex 4a·OEt2, in which fluorine coordination is replaced by an ether ligand. The structureof this complex has been determined; unlike its C5Me5 and C5H3(SiMe3)2 congeners, it showsthe boryldiene moiety to occupy a prone (endo) conformation. Propene inserts into the CH2terminus of the boryldiene ligand under ambient conditions to give the metallacycles CpRZr(C6F5){1:3-CH2CH(Me)-CH2C(Me)CHCHB(C6F5)2} (5a-d), with complete regioselectivityand very high stereoselectivity. The insertion process is reversible; propene extrusion occursvia 
-alkyl elimination from the major chair conformation isomer.
3-allyl)(4-isoprene) (2a-d). The preparationsare conveniently carried out as one-pot reactions. The reaction of 2a-d with B(C6F5)3 intoluene solution at -78 C proceeds quantitatively to give the thermally unstable zwitterioniccomplexes CpRZr(3-allyl){1:3-CH2CMeCHCH2B(C6F5)3} (3a-d), which on warming decompose under C-H activation and propene elimination to give CpRZr(C6F5){4-CH2CMeCHCHB(C6F5)2} (4a-d). The complexes are stabilized by the coordination of one o-Fatom of a boryl-C6F5 ring to the metal center. Compounds 4 are fluxional. The rotation ofthe Zr-C6F5 ligand is influenced by the steric demand of the Cp ligands (G = 43-49 kJmol-1), while there is little variation in the rotational barriers of the B-C6F5 substituents(G = ca. 47 kJ mol-1). Recrystallization of 4a from diethyl ether affords the 16-electroncomplex 4a·OEt2, in which fluorine coordination is replaced by an ether ligand. The structureof this complex has been determined; unlike its C5Me5 and C5H3(SiMe3)2 congeners, it showsthe boryldiene moiety to occupy a prone (endo) conformation. Propene inserts into the CH2terminus of the boryldiene ligand under ambient conditions to give the metallacycles CpRZr(C6F5){1:3-CH2CH(Me)-CH2C(Me)CHCHB(C6F5)2} (5a-d), with complete regioselectivityand very high stereoselectivity. The insertion process is reversible; propene extrusion occursvia -alkyl elimination from the major chair conformation isomer.