Synthesis and Characterization of a Series of (Hydroperoxo)-, (Alkylperoxo)-, and (μ-Peroxo)palladium Complexes Containing the Hydrotris(3,5-diisopropylpyrazolyl)borato Ligand (Tp^iPr2): (Tp^iPr2)(py)Pd−OO−X [X = H, <i>t</i>-Bu, Pd(Tp^iPr2)(py)] and (Tp^iPr2)(py)Pd−(μ-κ¹:κ²-OO)−PdTp^iPr2

Dehydrative condensation of the hydroxopalladium complex (TpiPr2)(py)Pd−OH (1) with hydroperoxides (XOOH: X = H, t-Bu) produces the corresponding (hydroperoxo)-, (TpiPr2)(py)Pd−OOH (2a), and (tert-butylperoxo)palladium complexes, (TpiPr2)(py)Pd−OOBut (3). Treatment of 2a with PPh3 results in concomitant ligand displacement giving (TpiPr2)(Ph3P)Pd−OOH (2b) and oxygenation of PPh3 giving OPPh3. Further condensation between 1 and 2a gives the μ-κ1:κ1-peroxo complex (TpiPr2)(py)Pd−OO−Pd(TpiPr2)(py) (4), while condensation between the bis(μ-hydroxo)dipalladium complex (PdTpiPr2)2(μ-OH)2 (7) with 2a affords the unsymmetrical μ-κ1:κ2-peroxo complex (TpiPr2)(py)Pd−OO−PdTpiPr2 (5). These peroxopalladium complexes 2−5 have been fully characterized by a combination of spectroscopic and crystallographic analyses, which lead to description of the O−O moieties in these complexes as peroxide (O22-) with sp3-hybridized oxygen atoms. The OOH moiety in 2b is found to interact with the noncoordinated nitrogen atom of the pendant pyrazolyl group through hydrogen bond. The O2 moieties in 2−5 turn out to be so nucleophilic (basic) as to add across carbon−heteroatom multiple bonds in acetonitrile and acetaldehyde to give the peroxometallacycle (8) (from 2, 4, and 5) and the acetato complex (TpiPr2)(py)Pd−OC(O)CH3 (9) (from 2−4), respectively. Methyl vinyl ether and styrene, CH2CHY (Y = OMe, Ph), are converted to the corresponding methyl ketones, CH3C(O)Y, upon treatment with 2−4.羟基钯配合物(TpiPr₂)(py)Pd−OH (1) 与氢过氧化物(XOOH：X=H, t-Bu)发生脱水缩合反应，生成对应的(氢过氧根合)钯配合物(TpiPr₂)(py)Pd−OOH (2a)以及(叔丁基过氧根合)钯配合物(TpiPr₂)(py)Pd−OOBut (3)。用三苯基膦(PPh₃)处理2a时，可同时发生配体取代与三苯基膦氧化反应，分别得到(TpiPr₂)(Ph₃P)Pd−OOH (2b)与三苯基氧膦(O=PPh₃)。1与2a进一步发生缩合反应，得到μ-κ¹:κ¹-过氧桥双核钯配合物(TpiPr₂)(py)Pd−OO−Pd(TpiPr₂)(py) (4)；而双(μ-羟基)双桥双核钯配合物(PdTpiPr₂)₂(μ-OH)₂ (7)与2a发生缩合反应，则得到不对称μ-κ¹:κ²-过氧桥双核钯配合物(TpiPr₂)(py)Pd−OO−PdTpiPr₂ (5)。本研究通过光谱学与晶体学分析相结合的方法，对上述过氧钯配合物2~5进行了完整表征，确证其O−O基团为过氧根(O₂²⁻)，且氧原子均采取sp³杂化形式。在2b中，其OOH基团可与悬挂吡唑基的未配位氮原子形成氢键相互作用。配合物2~5中的O₂基团表现出显著的亲核性(碱性)，可分别与乙腈及乙醛中的碳-杂原子多重键发生加成反应，得到过氧金属环化合物8(由2、4、5反应生成)与乙酸根合钯配合物(TpiPr₂)(py)Pd−OC(=O)CH₃ (9，由2~4反应生成)。甲基乙烯基醚与苯乙烯(CH₂=CHY，Y=OMe、Ph)在2~4作用下，可转化为对应的甲基酮类化合物CH₃C(=O)Y。