Diorganozinc compounds

Properties of zinc salts of inorganic and organic salts are Hsted in Table 1 with other commercially important zinc chemicals. In the dithiocarbamates, 2-mercaptobenzothiazole, and formaldehyde sulfoxylate, zinc is covalendy bound to sulfur. In compounds such as the oxide, borate, and sihcate, the covalent bonds with oxygen are very stable. Zinc—carbon bonds occur in diorganozinc compounds, eg, diethjizinc [557-20-0]. Such compounds were much used in organic synthesis prior to the development of the more convenient Grignard route (see Grignard reactions). 

Structural Studies of Diorganozinc Compounds Bearing a-Bound Ligands 326... 

Well-defined Diorganozinc Compounds in Polyolefin Catalysis 328... 

Diorganozinc Compounds Bearing Monodentate Donor Ligands 332... 

Diorganozinc Compounds Bearing Bidentate Donor Ligands 333... 

Organozinc Cations from the Protonolysis of Diorganozinc Compounds 340... 

The simplest diorganozinc compounds, ZnMe2 and ZnEt2, are commercially available from many vendors. All other diorganozinc compounds can be synthesized by one or more of the following synthetic methods, which are detailed in Figure 2 ... 

Functionalized olefins may be converted to the corresponding diorganozinc compounds via hydroboration and subsequent boron-zinc exchange, as shown in Scheme 4.28... 

Highly efficient syntheses of both hetero- and homoleptic diorganozinc compounds, such as 6 and 7, were achieved by the UV (X > 280 nm) irradiation of mixtures of functionalized organoiodides and diethyl- or diisopropylzinc (Scheme 7).34 Irradiation with ultraviolet light avoids the use of a large excess of diethylzinc, which often furnishes homoleptic diorganozincs rather than the desired heteroleptic ones. Reaction times rarely exceed 2 h and conversions from 55 to 95% were commonly achieved. 

Despite the extensive history of organozinc chemistry, the first solid-state structure of a Lewis base-free diorganozinc compound with cr-bound ligands, namely diphenylzinc, was not reported until 1990.37 Diphenylzinc was synthesized by the transmetallation of diphenylmercury with metallic zinc (Scheme 10) and, after multiple sublimations, obtained halide free in 67% yield. 

Table 3 Selected thermodynamic data of some diorganozinc compounds... 

The relatively low reactivity of diorganozinc compounds is demonstrated by the fact that even the addition of 2 or 3equiv. of ZnPh2 to [NbCl2 N(SiMe3)2 2] gave only the monophenyl product [NbCl N(SiMe3)2 2Ph].61... 

The addition of a large excess of bis(cj-alkenyl)zinc compounds to the TiC -catalyzed polymerization of propene resulted in an increased polymer yield, but a reduction in the molecular weights of the polymers.64 This suggests that the diorganozinc compounds are both co-catalysts and chain-transfer agents in this polymerization. The catalyst activity decreased in the order bis(3-butenyl)zinc < bis(7-octenyl)zinc < chlorodiethylaluminum. Bis(7-octenyl)zinc was co-polymerized with propene to afford hexylzinc side chains, whose zinc-carbon moieties were converted to vinyl groups by the addition of allyl bromide. 

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