Periodic trends in metal hydride donor thermodynamics:: Measurement and comparison of the hydride donor abilities of the series HM(PNP)2+ (M = Ni, Pd, Pt; PNP = Et2PCH2N(Me)CH2PEt2)
Periodic trends in metal hydride donor thermodynamics:: Measurement and comparison of the hydride donor abilities of the series HM(PNP)2+ (M = Ni, Pd, Pt; PNP = Et2PCH2N(Me)CH2PEt2)
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DOI：
10.1021/om0342816
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发表时间：
2004-02-02
期刊：
影响因子：
2.8
通讯作者：
DuBois, DL
中科院分区：
文献类型：
--
作者：
Curtis, CJ;Miedaner, A;DuBois, DL
通过将PNP分别加入到Pd（CH 3CN）（4）（BF 4）（2）和（COD）PtCl 2中，合成了配合物M（PNP）（2）（2+）（M = Pd，Pt，PNP = Et 2 PCH 2N（Me）CH 2 PEt 2）。以Pd（PNP）（2）（2+）、H2-和四甲基胍（TMG）为原料，在乙腈中反应合成了Pd（PNP）（2）。通过在CH 3CN中NEt 3存在下氢的异裂来测量HPt（PNP）（2）（+）（54.7 kcal/mol）的热力学氢化物供体能力Δ G度（H）（-）。通过测量氢化物直接转移到Pt（PNP）（2）（2+）的平衡常数来确定HPd（PNP）（2）（+）（51.1 kcal/mol）的氢化物供体能力。的M（II）配合物进行可逆的，在苯甲腈的两个电子的还原。在热力学循环中使用所测量的还原电位来估计HPd（PNP）（2）（+）和HPt（PNP）（2）（+）的去质子化的pK（a）值分别为22.1和27.6。氢化钯具有与氢化镍相等的酸度，并且是比镍和铂类似物更好的氢化物供体。这表明，过渡金属卤化物可以同时作为酸和氢化物给体。
The complexes M(PNP)(2)(2+) (M = Pd, Pt, PNP = Et2PCH2N(Me)CH2PEt2) were synthesized by addition of PNP to Pd(CH3CN)(4)(BF4)(2) and (COD)PtCl2, respectively. Pd(PNP)(2) was synthesized by reaction of Pd(PNP)(2)(2+) with H-2 and tetramethylguanidine (TMG) in CH3CN. The thermodynamic hydride donor ability, DeltaGdegrees(H)(-), for HPt(PNP)(2)(+) (54.7 kcal/mol) was measured by heterolytic cleavage of hydrogen in the presence of NEt3 in CH3CN. The hydride donor ability of HPd(PNP)(2)(+) (51.1 kcal/mol) was determined by measuring the equilibrium constant for direct hydride transfer to Pt(PNP)(2)(2+). The M(II) complexes undergo reversible, two-electron reductions in benzonitrile. The measured reduction potentials were used in a thermodynamic cycle to estimate pK(a) values of 22.1 and 27.6 for deprotonation of HPd(PNP)(2)(+) and HPt(PNP)(2)(+), respectively. The palladium hydride has an acidity equal to that of the nickel hydride and is a better hydride donor than both the nickel and platinum analogues. This shows that it is possible for transition metal hydrides to act simultaneously as both acids and hydride donors.