NiCl2 diene complex

When 2,3,4,5-tetraphenylzirconacyclopentadiene was treated with NiCl2(dppe) under reflux, the 2,3,4,5-tetraphenylnickelacyclopentadiene-dppe complex 36 was obtained as a red solid in 78% isolated yield, along with Cp2ZrCl2 (98% yield by NMR) (Eq. 2.27) [8a]. This complex was the same as that prepared from NiCl2(dppe) and l,4-dilithio-l,2,3,4-tetraphe-nyl-1,3-diene [30], In the case of NiCl2(PPh3)2, a similar transmetalation can proceed. Using this method, benzene and pyridine formation and CO insertion have been developed [8a,8b,46],... 

In contrast to palladium and rhodium catalyzed monohydroboration of 1,3-dienes,no 1,4-addition and only 1,2-addition products were obtained with an//-Markovnikov regioselectivity. Acyclic dienes were more reactive than cyclic dienes, and styrene was unreactive. Among iron(II) and cobalt(II) chloride complexes with dppe, dppp and dppb only CoCbCdppp) showed catalytic activity albeit lower than NiCl2(dppe). 

Some alkenes undergo a skeletal rearrangement reaction through cleavage of C-C bonds when treated with a transition metal complex. For example, 1,4-diene 5 isomerized to 1,4-diene 9 by action of a nickel catalyst (Scheme 7.3) [4]. Mechanistically, an Ni-H species is initially generated from NiCl2[P( -Bu)3]2... 

Both nickel(0)- and nickel(n)-phosphine complexes, e.g. [Ni(C2H4)(diphos)], [NiCl2(diphos)], can catalyse hydrosilylation of alkenes. An induction period is observed with the nickel(ii) system and it appears that an important step with these catalysts is reduction of nickel(ii) to nickel(0). The reduction does not occur below 100 °C. A possible mechanism for the reaction is given in Scheme 27. Asymmetric hydrosilylation of styrene and cyclic dienes with HSiCls can... 

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