Cp2Zr

Bridging and terminal nitrogens have been compared ia [Cp2Zr(N2)]2N2. The bridging N2 has a longer N—N distance (0.118 vs 0.1115 nm) and shorter Zr—N distances. In addition, the bridging N2 stretching frequency is very low, 1578 cm (248). 

SCHWARTZ Hydrozirconalion Hydrozirconation with Cp2Zr(CI)H and Michael addition of the Zr reagent... 

Complexes in which two metal centres are linked by one or two [NSN] ligands, e.g., [Na(15-crown-5)]2[F5Mo( -NSN)MoF5] and Cp2Zr( -NSN)2ZrCp2, are known. The cyclic zirconium system is prepared by a metathetical reaction (Eq. 7.14). However, the formation of polymers in which metal centres are linked by NSN units has not been achieved. 

Cp2Zr H2O, 50-98% yield. Allyl ethers are cleaved faster than allyl-amines that are also cleaved (66%)." ... 

Cp2Zr, then water, 66% yield.O-Allyl ethers are cleaved at a faster rate THP, acetonide. Bn ethers, and benzoates are stable. 

Thermolysis of the t]-coordinated zirconium complex of thiophene Cp2Zr(SiMc3) (C4H3S) is a thienyl ring cleavage reaction (920M1646). 

Diazametallacycles of the type Cp2Zr[Bu NC( = NR )NR ] have been prepared according to Scheme 92 from terminal zirconium imides and carbodiimides. A second series of analogous compounds was synthesized starting... 

The group of Protasiewicz, who has reported Cp2Zr complexed phosphinidenes with very bulky substituents and phosphine ligands, has explored the interchange of ligands and the formation of diphosphenes [113]. 

Fig.8 The molecular structure of Cp2Zr(Me)0B[0Si(0 Bu)3]2 generated from the crystallographic data of 1 of the 18 independent molecules from the asymmetric unit, with all hydrogen atoms omitted for clarity...

Attempts to hydroaminate ethylene, aUylbenzene, and norbornene with ArNH2 in the presence of zirconium bisamides Cp2Zr(NHAr)2 (Ar = 2,6-Me2CsH3, o-MeQH4) at temperatures up to 160°C have been unsuccessful [126]. 

In 1992, Bergman et al. reported that zirconium bisamides Cp2Zr(NHR)2 catalyze the intermolecular hydroamination of alkynes with sterically hindered primary amines to give enamines or their tautomeric imines (e.g., Eq. 4.77) [126]. 

Although zirconium bisamides Cp2Zr(NHAr)2 do not catalyze the hydroamination of alkenes (see above), they are catalyst precursors for the hydroamination of the more reactive double bond of allenes to give the anti-Markovnikov addition product (Eq. 4.96) [126]. 

Throughout this chapter we will use in the different Schemes the abbreviation [Zr] = CpjZrCl- thus [Zr]-H = [Cp2Zr(H)Cl]n (1) and [Zr]-R = Cp2Zr(R)Cl. Most of the compounds described in this chapter have metal centers with 16 electrons, and it is important to emphasize that any coordinatively unsaturated zirconocene (IV) complexes can potentially exist as dimeric, oligomeric, or polymeric aggregates. 

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