EFFECT OF THE LIGAND AND METAL ON THE PK(A) VALUES OF THE DIHYDROGEN LIGAND IN THE SERIES OF COMPLEXES [M(H-2)H(L)(2)](+), M=FE, RU, OS, CONTAINING ISOSTERIC DITERTIARYPHOSPHINE LIGANDS, L
EFFECT OF THE LIGAND AND METAL ON THE PK(A) VALUES OF THE DIHYDROGEN LIGAND IN THE SERIES OF COMPLEXES [M(H-2)H(L)(2)](+), M=FE, RU, OS, CONTAINING ISOSTERIC DITERTIARYPHOSPHINE LIGANDS, L
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DOI：
10.1021/ja00087a024
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发表时间：
1994-04-20
影响因子：
15
通讯作者：
SCHWEITZER, CT
中科院分区：
文献类型：
--
作者：
CAPPELLANI, EP;DROUIN, SD;SCHWEITZER, CT
通过二氢配合物MH（2）L（2）与HBF 4反应，合成了新的二氢配合物trans-[MH（H-2）L（2）] BF 4，L = P（C_6 H_4 - 4-R）（2）CH_2CH_2 P（C_6 H_4 -4-R）（2），R = CF_3，M = Fe，Ru，和Os，R = CH_3，M = Fe，R = OMe，M = Ru.根据H-1 NMR T-1和（1）J（HD）测量，自旋H-2配体的H-H键长不作为R的函数显著变化（当M = Fe时从CF 3到CH 3，当M = Ru时从CF 3到OCH 3），而对于Os络合物存在延长。H原子交换的速率常数（反映H-2均裂的容易程度）随着R对给定金属的给体能力的增加而增加，pK（a）值也是如此（反映异裂容易程度的降低）。报道了配合物MH（Cl）L（2）和MH（2）L（2）的电化学性质。正如预期的H-2酸度降低，因为母体氢化物变得更容易氧化，R（相同M）发生变化。作为金属的函数的二氢pK（a）值的趋势，Fe < Os < Ru，与二氢化物络合物M（H）（2）（CO）（4），Fe < Ru < Os，和[M（C5 H5）（H）（2）（PPh（3））（2）]（+），Ru < Os，Ru（2+）配合物trans-[RuH（H-2）L（2）] BF_4的高H-H键能可能是它们比相应的Os（2+）配合物酸性小的原因。对pK（a）值的考虑正确地表明，RuH（2）L（2）/[RuH（H-2）L（2）]（+）混合物在D-2和HO（t）Bu之间的H/D交换中比单独的二氢络合物更有效。
The new dihydrogen complexes trans-[MH(H-2)L(2)]BF4, L = P(C6H4-4-R)(2)CH2CH2P(C6H4-4-R)(2), R = CF3, M = Fe, Ru, and Os, R = CH3, M = Fe, R = OMe, M = Ru, are prepared by reaction of the dihydride complexes MH(2)L(2) With HBF4. The H-H bond length of the spinning H-2 ligand does not change significantly as a function of R (from CF3 to CH3 when M = Fe and from CF3 to OCH3 for M = Ru) according to H-1 NMR T-1 and (1)J(HD) measurements while there is a lengthening for the Os complexes. The rate constants for H atom exchange (reflecting the ease of homolytic splitting of H-2) increase with the increasing donor ability of R for a given metal as do the pK(a) values (reflecting a decrease in ease of heterolytic splitting). The electrochemical properties of some complexes MH(Cl)L(2) and MH(2)L(2) are reported. As expected H-2 acidity decreases as the parent hydride becomes easier to oxidize with this change in R (same M). The trend in dihydrogen pK(a) values as a function of the metal, Fe < Os < Ru, is distinctively different to the trend in pK(a) values of the dihydride complexes M(H)(2)(CO)(4), Fe < Ru < Os, and [M(C5H5)(H)(2)(PPh(3))(2)](+), Ru < Os, The high H-H bond energy of the RU(2+) complexes trans-[RuH(H-2)L(2)]BF4 is probably the reason why they are less acidic than corresponding Os2+ complexes. A consideration of the pK(a) values correctly indicated that a RuH(2)L(2)/[RuH(H-2)L(2)](+) mixture would be more effective at H/D exchange between D-2 and HO(t)Bu than the dihydrogen complex alone.