| This thesis described reactivity of vinyl ethers (CH2=CHOR) with two catalyst systems (alpha-diimine)PdMe+ (alpha-diimine = (Ar)N=C(R)-C(R)=N(Ar)) and (alpha-diimine)PdCl+, and the chemistry of group 4 metal poly(pyrazolyl)borate complexes.In Chapter One, we described that (alpha-diimine)PdMe+ species undergo multiple insertions of CH2=CHOSiPh3 (2), ultimately forming Pd allyl products. The reaction of (alpha-diimine)PdMeCl, [Li(Et2O)2.8][B(C6F5)4] (1 equiv), and 2 (8 equiv) in CH2Cl2 yields [(alpha-diimine)Pd{eta 3-CH2CHCH- CH(OSiPh3)CH2CH(OSiPh 3)Me}][B(C6F5)4] (7-B(C6F 5)4) in 83% NMR yield.In Chapter Two, the reactions of (alpha-diimine)PdMe+ species were investigated. Two pathways were observed. First, 1 initiates the cationic polymerization of 2a-c with concomitant decomposition of 1 to Pd0. Second, 1 reacts with stoichiometric quantities of 2a-g by formation of (alpha-diimine)PdMe(CH2=CHOR)+ (3a-g), insertion to form (alpha-diimine)Pd(CH2CHMeOR)+ (4a-g), reversible isomerization to (alpha-diimine)Pd(CMe 2OR)+ (5a-g), beta-OR elimination of 4a-g to generate (alpha-diimine)Pd(OR)(CH2=CHMe) + (not observed), and allylic C--H activation to yield (alpha-diimine)Pd(eta 3-C3H5)+ (6) and ROH.In Chapter Three, we showed that (alpha-diimine)PdCl+ species catalytically dimerize alkyl and silyl vinyl ethers to CH2=CHCH 2CH(OR)2 acetals, and cyclize divinyl ethers to analogous cyclic acetals. A plausible mechanism comprises in-situ generation of an active PdOR alkoxide species, double vinyl ether insertion to generate Pd{CH 2CH(OR)CH2CH(OR)2} species, and beta-OR elimination to generate the acetal product. In the presence of vinyl ethers, (alpha-diimine)PdCl + species can be used to initiate ethylene polymerization.In Chapter Four, the alkyl hydrido bis(pyrazolyl)borate reagent Tl(MeHB(3-mesityl-pyrazolyl) 2) (Tl(MeBpMs), 1) was prepared and used to generate group 4 metal MeBpMs complexes. The reaction of 1 with ZrCl4 affords (MeBpMs*)2ZrCl 2 (2, MeBpMs* = MeHB(3-mesityl-pyrazolyl)(5-mesityl-pyrazolyl) -). The reaction of 1 with M(CH2Ph)4 yields (MeBpMs)M(CH2Ph)3 (M = Zr (3), Hf (4)), bibenzyl and Tl0, via initial MeBpMs/benzyl exchange to produce 3 or 4 and Tl(CH2Ph), followed by thermal decomposition of Tl(CH2Ph).Chapter Five described that Lewis acids catalyze the reaction of Li[MeBH 3] and Na[BH4] with pyrazoles to yield poly(pyrazolyl)borates under mild conditions. Coordination of the pyrazole to the Lewis acid decreases the pKa of the pyrazole and increases the rate of B-H bond protonolysis. The reaction of Li[MeBH3] with 2 equiv of 3-mesityl-pyrazole (HpzMs) at 23°C (2 days) affords Li[MeB(3-mesityl-pz)2H] (Li[MeBpMs]) and Li[MeB(3-mesityl-pz)(5-mesityl-pz)H] (Li[MeBpMs*]) in 88 % yield (3/1 isomer ratio) in the presence of MeB(OiPr)2 (5 mol % vs. HpzMs) but only 28% yield without this additive.Chapter Six describes the synthesis of Tl[MeTpPh] and [MeTpPhTiCl3] complexes ([MeTpPh] - = MeB(3-phenyl-pyrazolyl)3-). All the attempts to alkylate [MeTpPhTiCl3] complex failed, suggesting that the reactivity of B-H bond is not the sole problem.In Chapter Seven, we described the synthesis, structures and reactivity of several group 4 mixed bispyrazolyl-borate/cyclopentadienyl complexes The core structures of 1-3 are very similar to Cp2ZrCl 2. 1/MAO, 2/MAO, 9, 10, 11 and 12 are highly active ethylene polymerization catalysts, and generate high-molecular-weight polyethylene. (Abstract shortened by UMI.)... |
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