Reger Daniel L, Gardinier James R, Gemmill William R, Smith Mark D, Shahin Ahmed M, Long Gary J, Rebbouh Leila, Grandjean Fernande
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
J Am Chem Soc. 2005 Feb 23;127(7):2303-16. doi: 10.1021/ja044900h.
Sonogashira coupling reactions of terminal alkynes with Fe[(p-IC6H4)B(3-Mepz)3]2 (pz = pyrazolyl ring) yield Fe[(p-PhC2C6H4)B(3-Mepz)3]2 (2), Fe[(p-Me3SiC2C6H4)B(3-Rpz)3]2 (R = H, 3a, R = Me, 3b), and Fe[(p-HC2C6H4)B(3-Mepz)3]2 (R = H, 4a, R = Me, 4b), a series of new complexes containing "third generation" poly(pyrazolyl)borate ligands. Complex 2 undergoes a fairly gradual iron(II) electronic spin-state crossover with a 30 K hysteresis, whereas complex 3b is an unusual example of a complex with equivalent iron(II) sites in the high-spin form that shows an abrupt 50% spin crossover. For complex 4b, 50% of the iron(II) sites undergo a gradual spin-state transition between 185 and 350 K with an activation energy of 1590 +/- 30 cm(-1) and a T(1/2) = 280 K and, for the remaining iron(II) sites, an abrupt cooperative spin-state crossover between 106 and 114 K. The crystal structures of 4b obtained for each of the three distinct electronic spin states reveal two crystallographically different iron(II) sites, and analysis of the molecular/supramolecular structures indicates that the difference in the degree of pyrazolyl ring tilting in the ligands between the two sites, rather than the strength of the intermolecular forces, play a prominent role in determining the temperature of the spin-state crossover.
端炔烃与Fe[(p - IC6H4)B(3 - Mepz)3]2（pz = 吡唑基环）的Sonogashira偶联反应生成了Fe[(p - PhC2C6H4)B(3 - Mepz)3]2（2）、Fe[(p - Me3SiC2C6H4)B(3 - Rpz)3]2（R = H，3a；R = Me，3b）和Fe[(p - HC2C6H4)B(3 - Mepz)3]2（R = H，4a；R = Me，4b），这是一系列含有“第三代”聚（吡唑基）硼酸盐配体的新型配合物。配合物2经历了相当平缓的铁（II）电子自旋态转变，滞后为30 K，而配合物3b是一个不寻常的例子，其处于高自旋形式的铁（II）位点等价，显示出50%的突然自旋转变。对于配合物4b，50%的铁（II）位点在185至350 K之间经历逐渐的自旋态转变，活化能为1590±30 cm⁻¹，T(1/2) = 280 K，而对于其余的铁（II）位点，在106至114 K之间发生突然的协同自旋态转变。在三种不同电子自旋态下获得的4b的晶体结构揭示了两个晶体学上不同的铁（II）位点，对分子/超分子结构的分析表明，两个位点之间配体中吡唑基环倾斜程度的差异，而非分子间作用力的强度，在决定自旋态转变温度方面起了重要作用。
