Effect of the phosphine steric and electronic profile on the Rh-promoted dehydrocoupling of phosphine-boranes.
Effect of the phosphine steric and electronic profile on the Rh-promoted dehydrocoupling of phosphine-boranes.
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DOI：
10.1021/ic500032f
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发表时间：
2014-04-07
影响因子：
4.6
通讯作者：
Manners I
中科院分区：
文献类型：
--
作者：
Hooper TN;Huertos MA;Jurca T;Pike SD;Weller AS;Manners I
本文报道了仲、伯膦硼烷H3 B·PR 2 H [R = 3，5-（CF 3）2C 6 H3; p-（CF 3）C6 H4; p-（OMe）C6 H4;金刚烷基，Ad]与H3 B·PCyH 2化学计量脱氢偶联分别生成金属键合的线性二硼膦H3 B·PR 2BH 2·PR 2 H和H3 B·PRHBH 2·PRH 2的电子效应和空间效应。[Rh（L）（η6-FC 6 H5）][BArF 4] [L = Ph 2 P（CH 2）3 PPh 2，ArF = 3，5-（CF 3）2C 6 H3]与2当量的H3 B·PR 2 H反应得到[Rh（L）（H）（σ，η-PR 2BH 3）（η1-H3 B·PR 2 H）][BArF 4]。这些配合物经脱氢偶联反应生成二硼膦配合物[Rh（L）（H）（σ，η2-PR 2·BH 2 PR 2·BH 3）][BArF 4]。当膦硼烷上有吸电子基团时，B-P裂解产物[Rh（L）（PR_2H）_2][BArF_4]平行形成，而当膦硼烷上有给电子基团时，则不形成平行产物。对于大体积的富电子H3 B·P（Ad）2 H，没有观察到脱氢偶联反应，但形成了中间体Rh（I）σ膦硼烷配合物[Rh（L）{η2-H3 B·P（Ad）2 H}][BArF 4]，其经历B-P键断裂得到[Rh（L）{η1-H3 B·P（Ad）2 H}{P（Ad）2 H}][BArF 4]。H3 B·PR 2 H（R =芳基）的脱氢偶联反应速率表明，吸电子取代基越多，脱氢偶联反应越快，但P-B键断裂也会导致平行产物的生成. H3 B·PCyH 2经历类似的脱氢偶联过程，并产生由前手性P-H键活化产生的所得金属结合的二硼膦的立体异构体的混合物，其中一种立体异构体是有利的。该非对映异构体混合物也可以通过使用手性膦配体来偏置。对催化脱氢偶联反应的选择性和效率也作了简要的讨论。本文报道了改变伯和仲膦-硼烷H3 B·PR 2 H（R = H，芳基，金刚烷基）中膦的空间和电子分布对铑催化脱氢偶联形成金属键合的线性二硼膦的影响。
The electronic and steric effects in the stoichiometric dehydrocoupling of secondary and primary phosphine–boranes H3B·PR2H [R = 3,5-(CF3)2C6H3; p-(CF3)C6H4; p-(OMe)C6H4; adamantyl, Ad] and H3B·PCyH2 to form the metal-bound linear diboraphosphines H3B·PR2BH2·PR2H and H3B·PRHBH2·PRH2, respectively, are reported. Reaction of [Rh(L)(η6-FC6H5)][BArF4] [L = Ph2P(CH2)3PPh2, ArF = 3,5-(CF3)2C6H3] with 2 equiv of H3B·PR2H affords [Rh(L)(H)(σ,η-PR2BH3)(η1-H3B·PR2H)][BArF4]. These complexes undergo dehydrocoupling to give the diboraphosphine complexes [Rh(L)(H)(σ,η2-PR2·BH2PR2·BH3)][BArF4]. With electron-withdrawing groups on the phosphine–borane there is the parallel formation of the products of B–P cleavage, [Rh(L)(PR2H)2][BArF4], while with electron-donating groups no parallel product is formed. For the bulky, electron rich, H3B·P(Ad)2H no dehydrocoupling is observed, but an intermediate Rh(I) σ phosphine–borane complex is formed, [Rh(L){η2-H3B·P(Ad)2H}][BArF4], that undergoes B–P bond cleavage to give [Rh(L){η1-H3B·P(Ad)2H}{P(Ad)2H}][BArF4]. The relative rates of dehydrocoupling of H3B·PR2H (R = aryl) show that increasingly electron-withdrawing substituents result in faster dehydrocoupling, but also suffer from the formation of the parallel product resulting from P–B bond cleavage. H3B·PCyH2 undergoes a similar dehydrocoupling process, and gives a mixture of stereoisomers of the resulting metal-bound diboraphosphine that arise from activation of the prochiral P–H bonds, with one stereoisomer favored. This diastereomeric mixture may also be biased by use of a chiral phosphine ligand. The selectivity and efficiencies of resulting catalytic dehydrocoupling processes are also briefly discussed. The effect of changing the steric and electronic profile of the phosphine of primary and secondary phosphine−boranes H3B·PR2H (R = H, aryl, adamantyl) on the Rh-catalyzed dehydrocoupling to form metal-bound linear diboraphosphines is reported.
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影响因子：
16.6
作者：
Helten, Holger;Dutta, Barnali;Manners, Ian
通讯作者：
Manners, Ian
影响因子：
16.6
作者：
Chaplin, Adrian B.;Weller, Andrew S.
通讯作者：
Weller, Andrew S.
影响因子：
4.3
作者：
Clark, Timothy J.;Lee, Kajin;Manners, Ian
通讯作者：
Manners, Ian
影响因子：
4.9
作者：
Huertos, Miguel A.;Weller, Andrew S.
通讯作者：
Weller, Andrew S.
影响因子：
4.6
作者：
Dorn, H;Vejzovic, E;Manners, I
通讯作者：
Manners, I