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The selective arene alkylation by alpha-chloronorborene catalyzed by electrophilic metallocenium ion pairs has been described. Control experiments and reactivity studies on each component step suggest a mechanism involving participation of the metal electrophiles in the catalytic cycle.

The coordinative/insertive stereoregular homopolymerizations and copolymerizations of styrene and methyl methacrylate mediated by a highly active single-site organotitanium catalyst are described. A new mechanism involving a sequential conjugate addition steps to explain the copolymeric results are suggested.

Several investigations into the energetics of ion-pair formation and reorganization are reported. A detailed investigation of ion-pairing in a series of typical metallocenium salts by both a straightforward colligative method and by pulsed field gradient spin-echo (PGSE) NMR method is carried out.

Single-site polymerization catalysts generated in situ via activation of Cp*MMe3 (Cp* = C5Me5; M = Ti, Zr), (CGC)MMe2 (CGC = C5Me4SiMe2NBut; M = Ti, Zr), and Cp2ZrMe2 with Ph3C+B(C6F5)4- catalyze alkylation of aromatic molecules (benzene, toluene) with α-chloronorbornene at room temperature, to regioselectively afford the 1:1 addition products exo-1-chloro-2-arylnorbornane (aryl = C6H5 (1a), C6H4CH3 (1b)) in good yields. Analogous deuterium-labeled products exo-1-chloro-2-aryl-dn-norbornane-7-d¹ (aryl-dn = C6D5 (1a-d6), C6D4CD3 (1b-d8)) are obtained via catalytic arylation of α-chloronorbornene in either benzene-d6 or toluene-d8. Isolated ion-pair complexes such as (CGC)ZrMe(toluene)+B(C6F5)4- and Cp2ThMe+B(C6F5)4- also catalyze the reaction of α-chloronorbornene in toluene-d8 to give 1b-d8 in good yields, respectively. Small quantities of the corresponding bis(1-chloronorbornyl)aromatics 2 are also obtained from preparative-scale reactions. These reactions exhibit turnover frequencies exceeding 120 h-1 (for the Cp*TiMe3/Ph3C+B(C6F5)4--catalyzed system), and chlorine-free products are not observed. Compounds 1 and 2 were characterized by ¹H, 2H, (13)C, and 2D NMR, GC-MS, and elemental analysis. The aryl group exo-stereochemistry in 1a and 1b is established using ¹H-¹H COSY, ¹H-(13)C HMBC, and ¹H-¹H NOESY NMR, and is further corroborated by X-ray analysis of the product 1,4-bis(exo-1-chloro-2-norbornyl)benzene (2a). Control experiments and reactivity studies on each component step suggest a mechanism involving participitation of the metal electrophiles in the catalytic cycle. [ABSTRACT FROM AUTHOR]