The synthesis, characterization, and reaction chemistry of a cationic Pt(II) solvento complex (2) are described. The complex demonstrates the unprecedented ability to promote polymerization of the electron-rich olefins ethyl vinyl ether (EVE), N-vinylcarbazole (NVC), and 2,3-dihydrofuran (DHF) via cationic initiation and subsequent propagation of the carbocation.

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The cationic iridium(III) complex [IrCF(3)(CO)(dppe)(DIB)][BARF](2) where DIB = o-diiodobenzene, dppe = 1,2-bis(diphenylphosphino)ethane, and BARF = B(3,5-(CF(3))(2)C(6)H(3))(4)(-) undergoes reaction in the presence of dihydrogen to form [IrH(2)(CO)(2)(dppe)](+) as the major product. Through labeling studies and (1)H and (31)P[(1)H] NMR spectroscopies including parahydrogen measurements, it is shown that the reaction involves conversion of the coordinated CF(3) ligand into carbonyl. In this reaction sequence, the initial step is the heterolytic activation of dihydrogen, leading to proton generation which promotes alpha-C-F bond cleavage. Polarization occurs in the final [IrH(2)(CO)(2)(dppe)](+) product by the reaction of H(2) with the Ir(I) species [Ir(CO)(2)(dppe)](+) that is generated in the course of the CF(3) --> CO conversion.

The synthesis of the silyl-protected 1,4-diazabutadiene ligands glyoxal-bis((2-R-triisopropylsiloxymethyl)-6-methylphenyl)diimine (TIPS-6-MPD) and glyoxal-bis((2-R-triisopropylsiloxymethyl)-4-methylphenyl)diimine (TIPS-4-MPD) and their subsequent reactions with trans-Pt(SMe 2 ) 2 (Me)Cl to generate the corresponding complexes (TIPS-6-MPD)Pt(Me)Cl (1a) and (TIPS-4-MPD)Pt(Me)Cl (1b) are described. Cationic complexes of the type [(N,N-chelate)-Pt(Me)(L)]BF 4 (where L ) solvent/olefin and N,N-chelate ) TIPS-6-MPD and TIPS-4-MPD) are generated by the reaction of chloro methyl complexes 1a and 1b with AgBF 4 in the presence of L. Various exchange reactions were examined for [(TIPS-6-MPD)Pt(Me)(NCCH 3 )]-BF 4 ( 2a), in which it was determined that the coordinated solvent reversibly exchanges with acrylonitrile, ethylene, fumaronitrile, cis-pentenenitrile, benzonitrile, dimethyl sulfide, and carbon monoxide to generate the corresponding cationic complexes 3-9, respectively. Kinetics experiments under pseudo-first-order conditions using 10-, 20-, and 30-fold excesses of benzonitrile demonstrate that 2a undergoes ligand exchange via an associative pathway with a bimolecular rate constant k 2 of (3.2 ( 2.0) × 10 -4 M -1 s -1 . Complex 2a was found to initiate the polymerization of various electron-rich monomers. A detailed analysis of the reaction demonstrates that the initiation is cationic in nature. The molecular structure of TIPS-6-MPD has been determined by a single-crystal X-ray diffraction analysis. The free ligand adopts an s-trans conformation with a planar NdCsCdN backbone.

The synthesis of a series of dicationic Ir(III) complexes is described. Reaction of Ir(CO)(dppe)I (dppe = 1,2-bis(diphenylphosphino)ethane)) with RI (R = CH(3) and CF(3)) results in formation of the Ir(III) precursors IrR(CO)(dppe)(I)(2) (R = CH(3) (1a) and CF(3) (1b)). Subsequent treatment with AgOTf (OTf = triflate) generates the bis(triflate) analogues IrR(CO)(dppe)(OTf)(2) (R = CH(3) (2a) and CF(3) (2b)), which undergo clean metathesis with NaBARF (BARF = B(3,5-(CF(3))(2)C(6)H(3))(4)(-)) in the presence of 1,2-diiodobenzene (DIB) forming the dicationic halocarbon adducts [IrR(CO)(dppe)(DIB)][BARF](2) (R = CH(3) (3a) and CF(3) (3b)). Complexes 3a and 3b demonstrate facile exchange chemistry with acetonitrile and carbon monoxide forming complexes 4 and 5, respectively. NMR investigation of the mechanism reveals that the process proceeds through an eta(1)-diiodobenzene adduct, where labilization at the coordination site trans to the alkyl group occurs first. Complex 3a reacts with ethylene forming the cationic iridium(I) product [Ir(C(2)H(4))(2)(CO)(dppe)][BARF] (6), which demonstrates fluxional behavior. Variable-temperature NMR studies indicate that the five-coordinate complex 6 undergoes three dynamic processes corresponding to ethylene rotation, Berry pseudorotation, and intermolecular ethylene exchange in order of increasing temperature based on NMR line shape analyses used to determine the thermodynamic parameters for the processes. The DIB adducts 3a and 3b were also found to promote olefin isomerization of 1-pentene, and polymerization/oligomerization of styrene, alpha-methylstyrene, norbornene, beta-pinene, and isobutylene via cationic initiation.