Preparation and Reactions of Molybdenum and Tungsten Hydride Complexes Containing the Tetraphosphane Ligand meso‐o‐C₆H₄(PPhCH₂CH₂PPh₂)₂

Abstract

The reaction of [Mo(κ2‐dppe)(κ4‐P4)] (1a) {dppe = PPh2CH2CH2PPh2, P4 = meso‐o‐C6H4(PPhCH2CH2PPh2)2} with 1 atm of H2 at room temperature selectively gave [MoH2(κ2‐dppe)(κ3‐P4)] (3a). The W analogue of 1a reacted with 1 atm of H2 at 80 °C to form a mixture of [WH2(κ2‐dppe)(κ3‐P4)] and [WH4(κ4‐P4)] (5b), the latter of which could be cleanly prepared by the reduction of [WBr2(κ4‐P4)] with NaBH4 in ethanol at 50 °C. The molecular structure of complex 5b differed from that of the related complex [WH4(dppe)2] and showed much higher reactivity. Insertion into the W–H bonds took place in the reaction of 5b with CS2 at 50 °C to give the methylenedithiolate complex [W(κ2‐S2CH2)(κ4‐P4)] (6) as the sole product, and the hydride ligands in 5b were replaced by isocyanides at 80 °C to form [W(CNR)2(κ4‐P4)] {R = tBu (7), 2,6‐Me2C6H3 (8)} in moderate yields. The detailed structures were determined by X‐ray crystallography for 3a, 5b, 6, and 7, while the fluxional behavior of 3a in solution was clarified by variable‐temperature NMR (VT NMR) spectroscopic studies.

Linear Connection of Four Nitrile Molecules on the Tetraphosphine Complexes of Tungsten and Molybdenum

“…Although various nitriles insert into the W–H bonds of 1 , this pathway is unlikely to lead to the tetrameric chain that contains no additional H atoms. On the other hand, 1 is capable of liberating two H 2 to generate a coordinatively unsaturated W(0) species with high electron-donating ability. , It is reasonable to postulate that two molecules of highly electron-accepting Ar F CN undergo reductive C–C coupling on this W center to yield the tungstacyclodiimine ring (or its resonance structure κ 2 -diimido complex) as illustrated in Scheme . A similar five-membered metallacycle formation from Zr(II) and p -tolunitrile has been reported by Bercaw et al, and a doubly N-protonated product (diimine complex) has been prepared through reduction of an Fe–MeCN complex by Mutterties and co-workers .…”

Transformations of aryl isothiocyanates on tetraphosphine tungsten complexes and reactivity of the resulting dithiocarbonimidate ligand

“…7 Our previous studies on Mo and W complexes have revealed structures and reactivity specific to P4, and recently the tetrahydride complex [WH 4 (k 4 -P4)] (3) has been synthesized. 8 The structure of 3 is different from the analogous complex [WH 4 (dppe) 2 ] in some points, and moreover, the reactivity of 3 is much higher than [WH 4 (dppe) 2 ], probably owing to a highly strained geometry around the W centre and the ability of P4 to change hapticity. 9 Subsequent study on the reactions of 3 with CS 2 and RNC (R = Bu t , 2,6-Me 2 C 6 H 3 ) has resulted in isolation of [W(k 2 -S 2 CH 2 )(k 4 -P4)] and [W(CNR) 2 (k 4 -P4)], proving that 3 is not only a strong hydride donor but also a good precursor of coordinatively unsaturated species.…”

“…revealed that double hydride insertion takes place in the reaction of 3 with a related heterocumulene CS 2 to give [W(k 2 -S 2 CH 2 )(k 4 -P4)] 8. Although the result of the reaction with ArNCS appears contrasting, a mechanism involving the corresponding complex [W(k 2 -13d Complex 3 reacted with alkyl isothiocyanates in different ways, and the products could not be identified.…”

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

“…We have been investigating the coordination chemistry of the linear tetradentate phosphine ligand meso-o-C 6 H 4 (PPhCH 2 CH 2 PPh 2 ) 2 (P4) using its Mo and W complexes [M(κ 2 -dppe)(κ 4 -P4)] (M = Mo (1), W; dppe = Ph 2 PCH 2 CH 2 PPh 2 ) as the precursors. 2 Research on reactivity toward various small molecules such as nitriles, isocyanides, CO, 3 H 2 , 4 CO 2 , and iso-thiocyanates 5 has revealed that the terminal PPh 2 groups in P4 readily dissociate to generate open coordination sites. In contrast, two internal P atoms maintain metal-P bondings owing to the rigid o-phenylene linkage and, as a result, the denticity of P4 changes between κ 4 , κ 3 , and κ 2 .…”

“…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. [3][4][5] This may allow the second metal atom trapped by the terminal PPh 2 to approach the Mo center easily. In this work, the reactivity of 2 at the Mo center is examined, and efficient formation of early-late bimetallic complexes is † Electronic supplementary information (ESI) available: X-ray crystallographic data in CIF format, additional information and diagrams of crystallographic studies, and NMR spectra of new compounds.…”