Evaluation of the Rh(II)鈥揜h(II) Bond Dissociation Enthalpy for [(TMTAA)Rh]2 by 1H NMR T2 Measurements: Application in Determining the Rh鈥揅(O)鈥?BD

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• 作者：Gregory H. Imler ; Michael J. Zdilla ; Bradford B. Wayland
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：October 7, 2013
• 年：2013
• 卷：52
• 期：19
• 页码：11509-11513
• 全文大小：275K
• 年卷期：v.52,no.19(October 7, 2013)
• ISSN：1520-510X

文摘

Toluene solutions of the rhodium(II) dimer of dibenzotetramethylaza[14]annulene ([(TMTAA)Rh]₂; (1)) manifest an increase in the line widths for the singlet methine and methyl ¹H NMR resonances with increasing temperature that result from the rate of dissociation of the diamagnetic Rh^II鈥揜h^II bonded dimer (1) dissociating into paramagnetic Rh^II monomers (TMTAA) Rh (2). Temperature dependence of the rates of Rh^II鈥揜h^II dissociation give the activation parameters for bond homolysis 螖H_app = 24(1) kcal mol^鈥? and 螖S_app = 10 (1) cal K^鈥? mol^鈥? and an estimate for the Rh^II鈥揜h^II bond dissociation enthalpy (BDE) of 22 kcal mol^鈥?. Thermodynamic values for reaction of 1 with CO to form (TMTAA)Rh鈥揅(O)鈥揜h(TMTAA) (3) 螖H₁掳 = 鈭?4 (1) kcal mol^鈥?, 螖S₁掳= 鈭?0(3) cal K^鈥? mol^鈥?) were used in deriving a (TMTAA)Rh鈥揅(O)鈥?BDE of 53 kcal mol^鈥?.