Brennessel William W, Kucera Benjamin E, Young Victor G, Ellis John E
Department of Chemistry, 120 Trustee Road, University of Rochester, Rochester, NY 14627, USA.
Department of Chemistry, 207 Pleasant Street SE, University of Minnesota, Minneapolis, MN 55455, USA.
Acta Crystallogr C Struct Chem. 2019 Aug 1;75(Pt 8):1118-1127. doi: 10.1107/S205322961900963X. Epub 2019 Jul 11.
Structures and spectroscopic characterization of the divalent complexes cis-dibromidotetrakis(2,6-dimethylphenyl isocyanide)iron(II) dichloromethane 0.771-solvate, [FeBr(CHN)]·0.771CHCl or cis-FeBr(CNXyl)·0.771CHCl (Xyl = 2,6-dimethylphenyl), trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)iron(II), [FeBr(CHN)] or trans-FeBr(CNXyl), trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)cobalt(II), [CoBr(CHN)] or trans-CoBr(CNXyl), and trans-dibromidobis(2,6-dimethylphenyl isocyanide)nickel(II), [NiBr(CHN)] or trans-NiBr(CNXyl), are presented. Additionally, crystals grown from a cold diethyl ether solution of zero-valent Fe(CNXyl) produced a structure containing a cocrystallization of mononuclear Fe(CNXyl) and the previously unknown dinuclear Fe(CNXyl), namely pentakis(2,6-dimethylphenyl isocyanide)iron(0) tris(μ-2,6-dimethylphenyl isocyanide)bis[tris(2,6-dimethylphenyl isocyanide)iron(0)], [Fe(CHN)][Fe(CHN)]. The (M)C-N-C(Xyl) angles of the isocyanide ligand are nearly linear for the metals in the +2 oxidation state, for which the ligands function essentially as pure donors. The νCN stretching frequencies for these divalent metal isocyanides are at or above that of the free ligand. Relative to Fe, in the structure containing iron in the formally zero-valent oxidation state, the Fe-C bond lengths have shortened, the C[triple-bond]N bond lengths have elongated, the (M)C-N-C(Xyl) angles of the terminal CNXyl ligands are more bent, and the νCN stretching frequencies have shifted to lower energies, all indicative of substantial M(dπ)→π* backbonding.
介绍了二价配合物顺式-二溴四（2,6-二甲基苯基异腈）铁（II）二氯甲烷0.771溶剂合物，[FeBr₂(CNXyl)₄]·0.771CH₂Cl₂ 或顺式-FeBr₂(CNXyl)₄·0.771CH₂Cl₂（Xyl = 2,6-二甲基苯基）、反式-二溴四（2,6-二甲基苯基异腈）铁（II），[FeBr₂(CNXyl)₄] 或反式-FeBr₂(CNXyl)₄、反式-二溴四（2,6-二甲基苯基异腈）钴（II），[CoBr₂(CNXyl)₄] 或反式-CoBr₂(CNXyl)₄ 以及反式-二溴双（2,6-二甲基苯基异腈）镍（II），[NiBr₂(CNXyl)₂] 或反式-NiBr₂(CNXyl)₂ 的结构和光谱表征。此外，从零价Fe(CNXyl) 的冷乙醚溶液中生长出的晶体产生了一种结构，其中包含单核Fe(CNXyl) 和先前未知的双核Fe₂(CNXyl)₆ 的共结晶，即五（2,6-二甲基苯基异腈）铁（0）三（μ-2,6-二甲基苯基异腈）双[三（2,6-二甲基苯基异腈）铁（0）]，[Fe(CNXyl)₅][Fe(CNXyl)₃]。对于处于 +2 氧化态的金属，异腈配体的（M）C-N-C（Xyl）角接近线性，此时配体基本上起纯供体的作用。这些二价金属异腈的νCN 伸缩频率等于或高于游离配体的频率。相对于Fe，在含有形式上零价氧化态铁的结构中，Fe-C 键长缩短，C≡N 键长伸长，末端CNXyl 配体的（M）C-N-C（Xyl）角更弯曲，并且νCN 伸缩频率已移至更低能量，所有这些都表明存在大量的M(dπ)→π* 反馈键。
