Efficient and chemoselective ethene hydromethoxycarbonylation catalysts based on Pd-complexes of heterodiphosphines o-C6H4(CH2P~tBu2)(CH2PR2)

Tamara Fanjul; Graham Eastham; Mairi F. Haddow

摘要

The synthesis and properties of a series of unsymmetrical diphosphines o-C6H4(CH2P~tBu2)(CH2PR2) are reported where R = C6H5 (L_a); p-CH3C6H4 (L_b); o-CH3C6H4 (L_c); o-CH3CH2C6H4 (L_d); o-CH3OC6H4 (L_e); 2,4,6-(CH3)3C6H4 (L_f); CH(CH3)2 (L_g); or PR2 = PCg (L_h) where PCg is 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamant-6-yl. Hydromethoxycarbonylation of ethene under commercially relevant conditions is catalysed by the Pd complexes of each of the ligands L_(a-h) to give methyl propanoate in >99% selectivity with catalytic activities comparable to those obtained with o-C6H4(CH2P~tBu2)2 (L1) or o-C6H4(CH2PCg)2 (L5). The catalysts derived from L_c, L_d and L_h are more active than the catalyst derived from L_a or L1; these ligands have in common, a PR2 donor that is more bulky than the PPh2 present in L_a. Treatment of [PtCl(CH3)(cod)] with L_(a-h) gave [PtCl(CH3)(L)] as mixtures of 2 isomers 1a-h and 2a-h. The major isomer in each case was 1a-h with the CH3 ligand trans to the P~tBu2 group; the diastereoselectivity of this reaction for products 1a-h ranges from 88% to over 99%. The crystal structures of lb, lc and le have been determined. Fluxionality associated with chelate ring inversion has been detected for lc by variable temperature ~(31)P NMR spectroscopy. The ~(31)P NMR data are compared for the complexes [PtCl(CH3)(L)], [Pt(CH3)2(L)] and [PtCl2(L)] where L = L_h, L1 or L5. The crystal structure of [Pt(CH3)2(L_h)] (4h) has been determined and shows that PCg is sterically less demanding than P~tBu2 in this complex. Treatment of 4h with HCl gave a 1:1 mixture of 1h and 2h that equilibrated over 5 h to a 70:1 mixture. Treatment of an equilibrium mixture of 1h and 2h with isotopically labelled ~(13)CO gas gave a single acyl complex [PtCl(~(13)COCH3)(L_h)] (5h) with retention of configuration at Pt, i.e. the ~(13)COCH3 is trans to the P~tBu2 group. Mechanisms for the CO insertion are discussed which are consistent with the observed stereochemistry. The palladium complexes [PdCl(CH3)(L_h)] (7/8) also reacted with labelled ~(13)CO to give a single acyl species [PdCl(~(13)COCH3)(L_h)]. Treatment of [PdCl(~(13)COCH3)(L_h)] with MeOH rapidly gave CH3~(13)COOMe.

机译：报告了一系列不对称双膦O-C6H4（CH2P〜TBU2）（CH2PR2）的合成和性能，其中r = C6H5（L_A）; P-CH3C6H4（L_B）; O-CH3C6H4（L_C）; O-CH3CH2C6H4（L_D）; O-CH3OC6H4（L_E）; 2,4,6-（CH3）3C6H4（L_F）; CH（CH3）2（L_G）;或PR2 = PCG（L_H），其中PCG为6-磷-2,4,8- trioxa-1,3,5,7-四甲基二甲基烷-6-基。在商业相关条件下乙烯的氢甲氧基殖化作用是由每种配体L_（A-H）的PD复合物催化的，以使甲基丙酸在> 99％的选择性中具有与O-C6H4（CH2P〜TBU2）2（CH2P〜TBU2）2（L1 ）或O-C6H4（CH2PCG）2（L5）。衍生自L_C，L_D和L_H的催化剂比从L_A或L1得出的催化剂更活跃;这些配体具有共同点，一个PR2供体比L_A中存在的PPH2更笨重。用L_（A-H）处理[PTCL（CH3）（COD）]的[PTCL（CH3）（L）]作为2个异构体1A-H和2A-H的混合物。在每种情况下，主要异构体为1A-H，而CH3配体转移到P〜TBU2组; 1A-H产品的该反应的非可映选择性范围从88％到99％以上。 LB，LC和LE的晶体结构已确定。通过可变温度〜（31）P NMR光谱检测到与螯合环反转相关的通量。比较了〜（31）P NMR数据的复合物[PTCL（CH3）（L）]，[PT（CH3）2（L）]和[PTCL2（L）]，其中L = L = L_H，L1或L5。已经确定了[PT（CH3）2（L_H）]（4H）的晶体结构，并表明PCG在该复合物中的要求比P〜TBU2少。用HCL处理4H的1：1混合物为1H和2H，在5小时内平衡至70：1混合物。用同位素标记的〜（13）CO气体处理1H和2H的平衡混合物给出了单个酰基复合物[PTCL（〜（13）COCH3）（L_H）]（5H）]（5H）]（5H），并在PT上保留构型13）COCH3是trans到P〜TBU2组的。讨论了与观察到的立体化学一致的CO插入机制。钯络合物[PDCL（CH3）（L_H）]（7/8）也与标记〜（13）CO的反应得出单个酰基物种[Pdcl（〜（〜（13）Coch3）（L_H）]]。用MEOH处理[PDCL（〜（13）COCH3）（L_H）]的治疗迅速得到CH3〜（13）Coome。

Efficient and chemoselective ethene hydromethoxycarbonylation catalysts based on Pd-complexes of heterodiphosphines o-C6H4(CH2P~tBu2)(CH2PR2)

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