Berben Louise A, Kozimor Stosh A
Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA.
Inorg Chem. 2008 Jun 2;47(11):4639-47. doi: 10.1021/ic702275g. Epub 2008 May 6.
Reaction of trans-(dmpe) 2CrCl2 (dmpe=1,2-bis(dimethylphosphino)ethane) with one equivalent of LiCCSiMe3 and one equivalent of nBuLi in THF under a dinitrogen atmosphere affords dark orange trans,trans-[(Me 3SiCC)(dmpe)2Cr]2(micro-N2).hexane (1). Under similar conditions but in the absence of acteylide ligand, the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of nBuLi yields the previously characterized complex trans-(dmpe)2Cr(N2)2 (2), while the reaction of trans-(dmpe)2CrCl2 with 2 equivalents of LiCCSiMe3 in THF yields trans-(dmpe)2Cr(CCSiMe3)2 (3). Compound 3 can also be synthesized by irradiating a mixture of trans-(dmpe)2CrMe2 and HCCSiMe3 or by reduction of HCCSiMe3 with compound 2. The magnetic properties, electrochemistry, and crystal structure of trans,trans-[(Me3SiCC)(dmpe)2Cr]2(micro-N2) are consistent with the complex containing two CrI ions bridged by a neutral N2 moiety, with a 1.178(10) A N[TRIPLE BOND]N bond distance. For complex 1 redox processes centered at E1/2=-1.69 V (DeltaEp=185 mV) and -1.43 V (DeltaEp=182 mV) versus Fe(Cp)2/Fe(Cp)2+ are assigned to the CrICrI/CrICrII and CrICrII/CrIICrII couples, respectively. For trans-(dmpe)2Cr(CCSiMe3)2 a reversible couple assigned as the CrII/III couple was observed at -1.59 V (DeltaEp=242 mV) versus Fe(Cp)2/Fe(Cp)2+. The dinuclear CrI-dinitrogen complex 1 has a room temperature magnetic moment of 2.77 microB while compound 3 displays a moment of 2.55 microB. Density-functional theory calculations performed on a model compound of 1, namely, trans,trans-[(HCC)(dpe)2Cr]2(micro-N2) (dpe=diphospinoethane), indicate that oxidation of the molecule should result in weakening of the dinitrogen triple bond.
在氮气气氛下，反式-(dmpe)₂CrCl₂（dmpe = 1,2 - 双(二甲基膦基)乙烷）与一当量的LiCCSiMe₃和一当量的正丁基锂在四氢呋喃中反应，得到暗橙色的反式,反式-[(Me₃SiCC)(dmpe)₂Cr]₂(μ-N₂).己烷(1)。在类似条件下但没有乙炔基配体时，反式-(dmpe)₂CrCl₂与2当量的正丁基锂反应生成先前已表征的配合物反式-(dmpe)₂Cr(N₂)₂(2)，而反式-(dmpe)₂CrCl₂与2当量的LiCCSiMe₃在四氢呋喃中反应生成反式-(dmpe)₂Cr(CCSiMe₃)₂(3)。化合物3也可以通过照射反式-(dmpe)₂CrMe₂和HCCSiMe₃的混合物或用化合物2还原HCCSiMe₃来合成。反式,反式-[(Me₃SiCC)(dmpe)₂Cr]₂(μ-N₂)的磁性、电化学性质和晶体结构与该配合物含有两个由中性N₂部分桥连的Crⁱ离子一致，N≡N键长为1.178(10) Å。对于配合物1，相对于Fe(Cp)₂/Fe(Cp)₂⁺，中心位于E₁/₂ = -1.69 V (ΔEp = 185 mV)和 -1.43 V (ΔEp = 182 mV)的氧化还原过程分别归属于CrⁱCrⁱ/CrⁱCrⁱⁱ和CrⁱCrⁱⁱ/CrⁱⁱCrⁱⁱ电对。对于反式-(dmpe)₂Cr(CCSiMe₃)₂，相对于Fe(Cp)₂/Fe(Cp)₂⁺，在 -1.59 V (ΔEp = 242 mV)观察到一个归属于Crⁱⁱ/Crⁱⁱⁱ电对的可逆电对。双核Crⁱ - 二氮配合物1在室温下的磁矩为2.77 μB，而化合物3的磁矩为2.55 μB。对1的模型化合物反式,反式-[(HCC)(dpe)₂Cr]₂(μ-N₂)（dpe = 二膦基乙烷）进行的密度泛函理论计算表明，分子的氧化应导致二氮三键的减弱。
