Solution homolytic bond dissociation energies of organotransition-metal hydrides
Solution homolytic bond dissociation energies of organotransition-metal hydrides
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DOI：
10.1021/ja00199a034
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发表时间：
1989-08
影响因子：
15
通讯作者：
M. Tilset;V. Parker
中科院分区：
文献类型：
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作者：
M. Tilset;V. Parker
单核金属羰基氢化物配合物（5-C5H5） M (CO) 3H （M= Cr, Mo， W）、（7,5 - c5me5） Mo (CO) 3H、（rj5-C5H5） W (CO) 2 (PMe3) H、（r, 5-C5H5） M (CO) 2H （M= Fe, Ru）、H2Fe (CO) 4、Mn (CO) 4PPh3H、Mn (CO) 5H、Re (CO) 5H和CO (CO) 3LH （L= CO, PPh3）的均裂键离解能（BDEs）P (OPh) 3)在乙腈溶液中通过使用热化学循环来估计，这需要了解金属氢化物pMa及其共轭碱（阴离子）的氧化电位。用这种方法得到的BDE值在50-67千卡/摩尔之间。在大多数情况下，这些结果与文献数据一致。我们的数据有力地支持了通常的假设，即第三行和第二行金属的MH键能比第一行金属大，差值为5-11千卡/摩尔。在该方法的误差范围内，既不能检测到膦或亚磷酸盐取代对MH键能的影响，也不能检测到环戊二烯环过甲基化对MH键能的影响。结果与先前的MH BDE估计和金属氢化反应模式有关。有机过渡金属氢化物（MH）配合物是一类重要的化合物，由于其参与许多化学计量和催化过程而受到广泛关注。很明显，氢化物键的强度对金属氢化物的性质有重要的影响，对决定氢化物键强度的因素的详细了解将极大地帮助我们理解许多过程中的反应模式。例如，配位不饱和过渡金属配合物对烷烃碳氢键的活化是一个正在大力研究的过程。4 . MH和MC键的形成
The homolytic bond dissocation energies (BDEs) of the mononuclear metal carbonyl hydride complexes (5-C5H5) M (CO) 3H (M= Cr, Mo, W),(7, 5-C5Me5) Mo (CO) 3H,(rj5-C5H5) W (CO) 2 (PMe3) H,(r, 5-C5H5) M (CO) 2H (M= Fe, Ru), H2Fe (CO) 4, Mn (CO) 4PPh3H, Mn (CO) 5H, Re (CO) 5H, and Co (CO) 3LH (L= CO, PPh3, P (OPh) 3) havebeen estimated in acetonitrile solution by the use of a thermochemical cycle that requires knowledge of the metal hydride pMa and the oxidation potential of its conjugate base (anion). The BDE values obtained by this method fall in the range 50-67 kcal/mol. In most cases, these results agree well with literature data. Our data provide strong support for the common assumption that the MH bond energies are greater for third-row and for second-row metals than for first-row metals, the difference being 5-11 kcal/mol. Effects of neither phosphine or phosphite substitution nor permethylation of the cyclopentadienyl ring on the MH bond energies could be detected within the error limits of the method. The results are discussed inrelation to previous MH BDE estimates and metal hydridereactivity patterns.Organotransition-metal hydride (MH) complexes constitute an important class of compounds and have received considerable attention particularly because of their involvement inmany stoichiometric and catalytic processes. 2 It is clear that the MH bond strengths exert a major influence on the properties of metal hydride compounds, and a detailed knowledge of the factors that determine the MH bond strengths would greatly aid in understanding reactivity patterns in many processes. 3 For example, the activation of alkane carbon-hydrogen bonds by coordinatively unsaturated transition-metal complexes is a process that is being vigorously pursued. 4 The formation of MH and MC bonds