Piro Nicholas A, Cummins Christopher C
Department of Chemistry, 77 Massachusetts Avenue, Room 6-435, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2009 Jul 1;131(25):8764-5. doi: 10.1021/ja903860k.
The terminal phosphorus monoxide complex (OP)Mo(N[(t)Bu]Ar)(3), 1 (Ar = 3,5-Me(2)C(6)H(3)), undergoes an O-for-PSiR(3) metathesis reaction with the niobium phosphinidene complex (i)Pr(3)SiPNb(N[CH(2)(t)Bu]Ar)(3), 2, to generate the oxoniobium complex ONb(N[CH(2)(t)Bu]Ar)(3), 3, and the diphosphenido complex (i)Pr(3)SiPPMo(N[(t)Bu]Ar)(3), 4. The structure of 4, as determined by X-ray crystallography, contains a "singly bent" diphosphenido moiety, suggesting that the diphosphenido ligand serves as a 3e(-) donor to a formally d(2) metal center. This bonding characterization was supported by DFT calculations and is unique among known diphosphenido complexes. Diphosphenido 4 was found to react over time to produce products consistent with a bimolecular degradation pathway where the terminal phosphide complex PMo(N[(t)Bu]Ar)(3), 5, serves as a stable leaving group. Mixtures of 4 and PPh(3) were observed to set up an equilibrium (K(eq) = 0.7) between 4, PPh(3), and the products of phosphinidene transfer, 5 and (i)Pr(3)SiP=PPh(3).
末端一氧化磷配合物(OP)Mo(N[(t)Bu]Ar)₃，1（Ar = 3,5-Me₂C₆H₃），与铌磷烯配合物(i)Pr₃SiPNb(N[CH₂(t)Bu]Ar)₃，2发生O-与PSiR₃的复分解反应，生成氧铌配合物ONb(N[CH₂(t)Bu]Ar)₃，3，以及二磷烯配合物(i)Pr₃SiPPMo(N[(t)Bu]Ar)₃，4。通过X射线晶体学确定的4的结构包含一个“单弯”的二磷烯部分，这表明二磷烯配体作为一个3e⁻供体与一个形式上的d²金属中心配位。这种键合特征得到了密度泛函理论计算的支持，并且在已知的二磷烯配合物中是独特的。发现二磷烯4会随着时间反应生成与双分子降解途径一致的产物，其中末端磷化物配合物PMo(N[(t)Bu]Ar)₃，5作为一个稳定的离去基团。观察到4和PPh₃的混合物在4、PPh₃以及磷烯转移产物5和(i)Pr₃SiP=PPh₃之间建立了平衡（K(eq) = 0.7）。
