A facile regioselective switch for nickel-catalyzed hydroarylation of vinylarenes with benzothiazoles has been developed, which relies on the simple structural variation of novel Ni­(II) complexes of the type Ni­(NHC)­[P­(OR)3]­Br2. Using magnesium turnings as the reductant, Ni­(IMes)­[P­(OEt)3]­Br2 afforded branched products, while Ni­(IPr*OMe)­[P­(OEt)3]­Br2 created steric demand to afford linear products. This work also provides a rare example of the rational design of heteroleptic Ni­(II) complexes that display the required air stability, reactivity, and regioselectivity via synergism between NHC and phosphite ligands.

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respectively. Attempt to synthesize mono-ligand Fe(II) bromide by the 1:1 molar ratio of NaL to FeBr 2 is unsuccessful, and the same complexes of 3 and 4 were obtained. Both 3 and 4 have been depicted by elemental analysis and X-ray structure determination. Preliminary studies show that both 3 and 4 can be used as single-component catalyst for the ring-opening polymerization of ε-caprolactone, and the catalytic activity of 3 is higher than that of 4. iron complex, functionalized N-heterocyclic carbene, ε-caprolactone, ring-opening polymerization Over the past decade, the application of N-heterocyclic carbenes (NHCs), as alternatives to traditional phosphines, in ligand designs and modifications has played a crucial role for developing late transition metal-based catalysts [1,2] . Up to date, the most of current attention has been focused on ruthenium, rhodium, palladium, and nickel-based systems. However, the chemistry of NHC systems of iron is considerably less developed. To the best of our acknowledge, only several kinds of ironbased NHC complexes have been reported, including the mononuclear Fe(II) halides of Fe(NHC) 2 X 2 [3] , the pianostool Fe(II) complexes of CpFe(CO) 2 (NHC)X [4] , the pincer Fe(II)/Fe(III) complexes of Fe[2,6-bis(NHC)-pyridine] X n (n = 2 or 3) [5,6] , and binuclear Fe(II) complexes of Fe 2 (μ-S(CH 2 ) 3 S)(CO) 6-x (NHC) x (x = 1, 2) [7] . Among these complexes, only the complex of Fe(NHC) 2 X 2 has been found to show good catalytic activity for the atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate [3] . Considering the currently increasing attention on iron-based systems [8,9] , further study on the synthesis of iron-based complexes with NHC ligand and their reactivity in homogeneous catalysis is valuable.Very recently, we have designed a novel kind of phenolate chelating NHC ligands [10] and synthesized the first anionic functionalized NHC complex of Fe(II) [11] . It is also found that this kind of iron complex could be used as single-component initiator for the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) [11] . However, the complex of this type is extremely sensitive to air and moisture, resulting in difficulty to detailed reactivity investigation. Frequently, stability is one of the significant points for the purpose of constructing a new kind of metal-based catalyst. This prompted us to modify the reported phenolate chelating NHC ligand to an enolate form (Scheme 1). Recently, enolate chelating

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The dearomative [5 + 1] annulation of 2-methylindoles with new five-membered synthon was developed through cascade [1,5]-hydride transfer/dearomative cyclization in HFIP for the synthesis of spirochromanes bearing the 2-methylindolenine skeleton.