Single-Crystal ³¹P NMR and X-ray Diffraction Study of a Molybdenum Phosphine Complex: (5-Methyldibenzophosphole)pentacarbonylmolybdenum(0)

The molecular structure of (5-methyldibenzophosphole)pentacarbonylmolybdenum(0), 1, has been determined by X-ray crystallography. The crystal is monoclinic C2/c, Z = 8, with unit cell dimensions of: a = 31.113(2) Å, b =7.7917(5) Å, c = 17.9522(12) Å, and β = 122.135(4)°. Least-squares refinement converged to R(F) = 0.0245 for 2407 independent reflections. The molecular structure is typical of phosphine-substituted metal carbonyls. It contains an approximate mirror plane which bisects the dibenzophosphole framework. Phosphorus-31 NMR spectra of powder and single-crystal samples of 1 have been obtained with cross-polarization and 1H high-power decoupling. The 31P CP/MAS NMR spectra exhibit exceptionally well-resolved satellites due to spin−spin coupling interactions with 95,97Mo (I = 5/2). Using first-order perturbation theory, the multiplets have been analyzed to yield 1J(95,97Mo,31P) = 123(2) Hz and estimates of the molybdenum nuclear quadrupolar coupling constants, χ(95Mo) = −0.87 MHz and χ(97Mo) = 10.1 MHz. Phosphorus-31 NMR spectra of a large single crystal of 1 have been investigated as a function of orientation about three orthogonal axes in the applied magnetic field. Analysis of the data yields the three principal components of the phosphorus chemical shift tensor, δ11 = 112 ppm, δ22 = −23 ppm, and δ33 = −40 ppm; δ22 lies close to the Mo−P bond (8°), while δ11 lies in the approximate mirror plane. The phosphorus chemical shift tensor determined for 1 is compared with the limited anisotropic phosphorus shift data available in the literature.本研究通过X射线晶体学（X-ray crystallography）测定了(5-甲基二苯并膦杂环)五羰基钼(0)（化合物1）的分子结构。该晶体属于单斜晶系，空间群为C2/c，晶胞内化学式单元数Z=8，晶胞参数如下：a=31.113(2) 埃（Å），b=7.7917(5) 埃，c=17.9522(12) 埃，β=122.135(4)°。最小二乘精修收敛后，针对2407个独立衍射点得到R(F)=0.0245。该分子结构符合膦取代金属羰基配合物的典型特征，其存在一个近似镜面，可将二苯并膦杂环骨架平分。 针对化合物1的粉末与单晶样品，本研究采用交叉极化（cross-polarization）结合1H高功率去耦技术采集了磷-31（31P）核磁共振谱。31P 交叉极化/魔角旋转（CP/MAS NMR）核磁共振谱展现出分辨率极佳的卫星峰，这源于与自旋量子数I=5/2的95,97Mo之间的自旋-自旋耦合（spin−spin coupling interactions）相互作用。基于一阶微扰理论（first-order perturbation theory）对该多重峰进行解析，得到耦合常数1J(95,97Mo,31P)=123(2) Hz，并估算出钼核的四极耦合常数：χ(95Mo)=−0.87 MHz，χ(97Mo)=10.1 MHz。 本研究还针对一块大尺寸单晶样品，探究了在外磁场中沿三个正交轴改变取向时的31P核磁共振谱。对实验数据进行解析后，得到磷化学位移张量（chemical shift tensor）的三个主分量：δ₁₁=112 ppm，δ₂₂=−23 ppm，δ₃₃=−40 ppm；其中δ₂₂与Mo−P键的夹角仅为8°，而δ₁₁位于前述近似镜面内。最后，本研究将化合物1的磷化学位移张量与现有文献中有限的各向异性磷位移数据进行了对比。