Reactions of Dienes with a Mo(0) Complex with Tetraphosphine Coligand [Mo(P4)(Ph₂PCH₂CH₂PPh₂)] (P4 = Meso‐o‐C₆H₄(PPhCH₂CH₂PPh₂)₂)

Abstract

Reaction of tetraphosphine complex [Mo(κ4‐P4)(Ph2PCH2CH2PPh2)] (1; P4 = meso‐o‐C6H4‐(PPhCH2CH2PPh2)2) with E‐1,3‐pentadiene in toluene at 60 °C gave the η4‐diene complex [Mo(η4‐E‐1,3‐pentadiene)(κ4‐P4)] (2), which is present as a mixture of two isomers due to the orientation of the Me group in the diene ligand. Treatment of 1 with Z‐1,3‐pentadien also resulted in the formation of 2 as the sole product after heating the reaction mixture at 90 °C. Whereas the reaction of 1 with 1,3‐cyclohexadiene at 60 °C afforded the η4‐diene complex [Mo(η4‐cyclohexadiene)(κ4‐P4)] (6), that with cyclopentadiene led to the C‐H bond scission product [η5‐C5H5)MoH(κ3‐P4)] (7). Detailed structures were determined by X‐ray crystallography for 2, 6,and 7, and fluxional feature of 6 in solution was clarified based on the VT‐NMR studies.

A molybdenum complex bearing a tetraphosphine ligand as a precursor for heterobimetallic complexes

“…The Mo center adopts a four-legged piano stool geometry, which exhibits no significant differences to that in 2. 14 The Ru and Ir centers exhibit standard three-legged piano stool structures 26,27 and are entirely separated from the Mo center by more than 7 Å, neglecting any bonding interactions between two metal atoms. Regarding the Ru center in 6, the Hmb ring is staggered relative to the other three ligands.…”

“…The complex [CpMoH(κ 3 -P4)] (2) was prepared according to a literature method. 14 Other reagents were commercially available and used as received. 1 H (400 MHz) and 31 P{ 1 H} (162 MHz) NMR spectra were recorded on a JEOL alpha-400 or a JEOL ECS400 spectrometer at 20 °C.…”

“…8e,11-13 Recently, we have reported that the reaction of 1 with cyclopentadiene produces the hydride-cyclopentadienyl complex [CpMoH(κ 3 -P4)] (2; Cp = η 5 -C 5 H 5 ), in which the P4 ligand coordinates to the Mo center in a κ 3 -mode through the arm-off of one terminal PPh 2 group (eqn (1)). 14 To synthesize dinuclear complexes bridged by P4, 2 is a desirable precursor in comparison with P4 complexes containing the dppe ligand, because dppe may otherwise bind to the added metal sources to result in complexity and fragmentation. It is also advantageous that the other ligands are hydride and Cp, which are sterically much smaller than any sets of dppe with a certain two-electron donor as widely seen in previously synthesized complexes.…”