Solid State NMR Studies of H/CO Dynamics on Multi-nuclear Transition-metal Clusters

本文对H_4Ru_4(CO)_2和H_4Ru_4(CO)_t；12&gt；{P(OMe)_3}进行了变温、MAS和宽线固体核磁共振测量。两个样品的氢化物共振的自旋晶格弛豫时间(Ti)和半强线宽(DELTAupsilonl/2)随温度的变化非常相似，表明氢化物发生了共同的氢化物运动，Ea=17*2LiMo1^&lt；-1&gt；本文报道了(NMe_4)4-x[H_xNi_&lt；12&gt；(CO)_&lt；21&gt；]·S(x=1，S=Me_2CO；x=2，S=1/2THF)的分子结构。这两种阴离子是相似的，由中心的Ni_6(CO)_3(Mu-CO)_6层组成，两侧是两个Ni_3(CO)_3(Mu-CO)_3-层，使得Ni_1；12-香料是六方紧密堆积的。中心Ni6面(B)和外部两个Ni3面(A，C)之间的分离与两个八面体…中的一个(x=1)或两个(x=2)的H占位一致L金属腔较多。报道了这两个簇合物的变温固态^1H MAS和^&lt；13&gt；C CP/MAS核磁共振谱。对于二氢化合物，固态~1H和~(13)GT；C谱从低温到室温保持不变，与X射线结构一致；在室温下，在Ni_6层的两侧有两个与之一致的氢化物共振，高场漂移与它们不在Ni_6-八面体空穴的中心一致。对于[H_2Ni_&lt；12&gt；(CO)_&lt；12-gt；]，溶液和固相CO的化学位移是一致的，除了内桥羰基在溶液中表现为一次共振，而在固体中由于桥联CO位于Ni6平面以上或以下而表现为两次共振。在较高的温度下，有证据表明存在H-运动(可能围绕对称面振荡)，但^&lt；13&gt；C谱表明CO基本上保持静止。对于一氢化合物，三个桥联CO几乎与Ni_6平面共面，一个C6明显向氢化物倾斜，两个CO处于中间位置；低温固态~(13)&gt；CO的核磁共振谱似乎与该结构完全一致。在室温下，~&lt；13&gt；CO的共振峰发生了一定程度的聚合，表明有一定的羰基运动，但没有证据表明H原子从占据的间隙八面体位置迁移到未占据的八面体位置。较少

Variable temperature, MAS and wide-line solid state NMR measurements have been carried out on H_4Ru_4(CO)_<12> and H_4Ru_4(CO)_<12>{P(OMe)_3}. The variation of spin-lattice relaxation time (Ti) and linewidth at half intensity (DELTAupsilonl/2) of the hydride resonance with temperature for both samples are very similar and suggests that a common hydride movement occurs with Ealpha=17 * 2 LI mo1^<-1>. We attribute this movement to a 2-site H-flip about H-occupied Ru-Ru edges which preserves the site symmetry of the crystals.The molecular structures of(NMe_4)4-x[H_xNi_<12>(CO) _<21>].S (x=1, S=Me2CO ; x=2, S=1/2 THF) are reported. Both anions are similar and consist of a central Ni_6(CO)_3(mu-CO)_6 - layer flanked on both sides by two Ni_3(CO)_3(mu-CO)_3-layers such that the Ni_<12>-fragrpent is hexagonal close-packed. The separation between the central Ni_6-plane (B) and the two outer Ni_3-planes (A, C) is consistent with H-occupancy of either one (x=1) or both (x=2) of the two octahedra … More l metal cavities. Variable temperature solid state ^1H MAS and ^<13>C CP/MAS NMR spectra are reported for both clusters. For the dihydride, the solid state ^1H and ^<13>C NMR spectra remain unchanged from low to room temperature and are consistent with the X-ray structure ; at room temperature, there are two hydride resonances consistent with them being on the plane of symmetry on opposite sides of the Ni_6-layer and the highfield shift is consistent with them not being in the center of the Ni_6- octahedral cavity. For [H_2Ni_<12>(CO)_<12>]^<2->, there is close agreement between the solution and solid state ^<13>CO chemical shifts except for the inner bridging carbonyls which appear in solution as one resonance whereas in the solid state occur as two resonances due to the bridging CO's being either above or below the Ni6-plane. At higher temperatures, there is evidence for H-movement (probably oscillation about the plane of symmetry) but ^<13>C spectra indicate that the CO's remain essentially static. For the monohydride, three of the bridging CO's are almost co-planar with the Ni_6-plane, one, C6, is significantly bent towards the hydride and two CO's are in intermediate positions ; the low temperature solid state ^<13>CO NMR spectra appear to be entirely consistent with this structure. At room temperature, there is some coalescence of the ^<13>CO resonances, suggesting some carbonyl-movement, but there is no evidence for H-migration from the occupied interstitial octahedral site to the unoccupied octahedral site. Less