Magnetic structure and covalence in tetrachlorobis(N-phenylacetamidinato)rhenium(IV) by neutron diffraction
Magnetic structure and covalence in tetrachlorobis(N-phenylacetamidinato)rhenium(IV) by neutron diffraction
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通过中子衍射研究四氯化双(N-苯基乙脒)铼(IV)的磁性结构和共价
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发表时间：
1999
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通讯作者：
David Martín yMarero
中科院分区：
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作者：
P. A. Reynolds;B. Figgis;David Martín yMarero
在2 K和20 K下对络合物cis-[ReCl4(NHCMeNHPh)2]进行了粉末中子衍射测量。在9.7(1)K处，衍射强度对磁有序的变化在Shubnikov群Pc 'n中被拟合到一个反铁磁有序的磁结构中，在这个正交晶体中自旋沿着c排列。每个分子中的铼位点上有2.58(6)µB的矩，而由于共价自旋离域，每个氯位点的自旋居群为1.03(8)µB。另外两种配体的N-C-N区各有-1.86（10）µB的自旋居布，表明电子相关效应导致了相当大的自旋极化。反铁磁结构与早先单晶磁化数据的重新解释一致。分子内观察到的大量自旋转移在这种重金属配合物中并不意外，并且在定性上是合理的，因为两种配体类型之间存在协同相互作用。先前观察到的这种晶体中的超磁转变被解释为是由分子内倾斜角度的变化驱动的，从紧密地沿着c排列到分子的对半部分倾斜不同的排列，具有小但重要的+b和-b分量。因此，分子内部的磁化方向并不完全平行。
Powder neutron diffraction measurements have been made at 2 and 20 K for the complex cis-[ReCl4(NHCMeNHPh)2]. The changes in diffracted intensities on magnetic ordering at 9.7(1) K were fitted in the Shubnikov group Pc′c′n to an antiferromagnetically ordered magnetic structure in which the spins are aligned along c in this orthorhombic crystal. A moment of 2.58(6) µB resides on the rhenium site in each molecule, while each chlorine site has a spin population of 1.03(8) µB due to covalent spin delocalisation. The N–C–N region of the other two ligands each has a spin population of –1.86(10) µB, indicating a substantial spin polarisation resulting from electron correlation effects. The antiferromagnetic structure is consistent with a reinterpretation of earlier single crystal magnetisation data. The very large amounts of spin transfer observed within the molecule are not unexpected in this heavy metal complex, and qualitatively reasonable given a synergistic interaction between the two ligand types. The previous observation of a metamagnetic transition in this crystal is explained as being driven by a change in canting angles within the molecule, from alignment closely along c to an arrangement in which opposite halves of the molecule are differently canted, with small but significant +b and –b components. The direction of magnetisation within the molecule is thus not all parallel.