DYNAMIC ETA-1-BENZYLBIS(TRIETHYLPHOSPHINE) AND ETA-3-BENZYLBIS(TRIETHYLPHOSPHINE)PALLADIUM(II) CATIONS - MECHANISMS OF INTERCONVERSION
DYNAMIC ETA-1-BENZYLBIS(TRIETHYLPHOSPHINE) AND ETA-3-BENZYLBIS(TRIETHYLPHOSPHINE)PALLADIUM(II) CATIONS - MECHANISMS OF INTERCONVERSION
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DOI：
10.1021/ja00471a031
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发表时间：
1978-01-01
影响因子：
15
通讯作者：
STILLE, JK
中科院分区：
文献类型：
--
作者：
BECKER, Y;STILLE, JK
(S)-(-)-铱-氯(7;,-α-氘代苄基)双(三乙基膦)钯(II)(6)与四苯基硼酸钠的反应得到(S)-(+)-(i)3-α-氘代苄基)双(三乙基膦)钯(II)四苯基硼酸(7)，α-苄基钯阳离子，在溶液中保留其光学活性。用氯化物从 7 再生苄基络合物 6，得到苄基碳构型净保留率为 94% 的产物。类似的未氘化 3 配合物（四氟硼酸盐）在氯仿中显示出该苄基物质的 31P 和 NMR 光谱特征；然而，在低温下的腈溶剂中，可以观察到 3 和 ' 配合物。在升高的温度下，两者迅速发生相互转化，显示出一种 3IP 膦单线态和一种苄基单线态。这些结果与重排机制最一致，该重排机制涉及苄基物种的快速表面转移，以及通过苄基中间体进行的反面重排。具有流变特征的苄基配体代表了与过渡金属的不寻常的配位类型。尽管这种类型的键合最近才在络合物(对3-苄基)-(对5-环戊二烯基)二羰基钼中被认识到，2它代表了许多有机金属转化和催化反应中重要的中间体类型。铂族-苄基络合物通过暗示或直接观察参与了许多此类反应。双(1,2,3-对3-苄基)二-/异-氯-镍(II)(Ia)可能是羰基镍催化的苄基卤化物与联苄基和苯偶酰的偶联反应中的中间体。 3 钯类似物 (lb) 是一种反应性络合物
The reaction of (S)-(—)-iranr-chloro (7;,-a-deuteriobenzyl) bis (triethylphosphine) palladium (II)(6) with sodium te-traphenylborate gives (S)-(+)-(i) 3-a-deuteriobenzyl) bis (triethylphosphine) palladium (II) tetraphenylborate (7), a-benzylpalladium cation, that retains its optical activity in solution. Regeneration of-benzyl complex 6 from 7 with chloride gives a product with 94% net retention of configuration at thebenzyl carbon. The analogous undeuterated 3 complex (tetrafluoro-borate) in chloroform shows 31P and NMR spectra characteristicof this-benzyl species; however, in nitrile solvents at low temperatures, both the 3 and the'complexes can beobserved. At elevated temperature, interconversion of the two takes place rapidly, displaying one 3IP phosphine singlet and one benzyl singlet. These results are most consistent with a rear-rangement mechanism involving rapid suprafacial shifts of the-benzyl species, and an antarafacial rearrangement that pro-ceeds through the-benzyl intermediate.The-benzyl ligand, possessing fluxional character, represents an unusual type of coordination to a transition metal. Although thistype of bonding was first recognized only re-cently in the complex (p3-benzyl)-(p5-cyclopentadienyl) dicarbonylmolybdenum, 2 it represents an important type of in-termediate in a number of organometallic transformations and catalytic reactions.-Benzyl complexes of the platinum group are involved in a number of such reactions, either by implication or direct observation. Bis (l, 2, 3-p3-benzyl) di-/i-chlo-ro-nickel (II)(la) is probably an intermediate in the nickel carbonyl catalyzed coupling of the benzyl halides to bibenzyl and benzil. 3 The palladium analogue (lb) is a reactive complex