Carbon−Phosphorus Bond Cleavage in Allyldiphenylphosphine by a Heterobimetallic Ni═Mo Complex and Formation of an Electronically Unsaturated NiMo₂ μ-Diphenylphosphido Cluster

Abstract

The unsaturated nickel-molybdenum complex [(η-C 5 Me 5 )NidMo(CO) 3 (η-C 5 H 5 )] (NidMo), 1, reacts with allyldiphenylphosphine (ADPP) to give the complex [(η-C 5 Me 5 )Ni(µ-CO) 2 Mo(CO)(κ 1 (P)-PPh 2 CH 2 CHdCH 2 )(η-C 5 H 5 )] (Ni-Mo), 2, which is in equilibrium with the starting materials at ambient temperature. Nevertheless, orange crystals of complex 2 could be isolated from the solution, and a single-crystal X-ray diffraction study confirmed that the phosphine ligand is bound to the molybdenum atom via the phosphorus atom alone. Prolonged heating of complex 1 with excess ADPP led to activation of the P-C allyl bond and to the isolation of the unsaturated trinuclear NiMo 2 µ-diphenylphosphido cluster [(η-C 5 Me 5 )NiMo 2 (η-C 5 H 5 ) 2 (µ 3 -CO)(µ-PPh 2 )(CO) 2 ], 3. The structure of this 46-electron cluster was established spectroscopically and by a single-crystal X-ray diffraction study. It is electronically unsaturated and contains a formal ModMo double bond that is spanned by a µ-PPh 2 ligand; the molecule exhibits effective mirror plane symmetry in solution, and in the solid state, an approximate mirror plane is also observed.

Allylnickel(II) and Allylpalladium(II) Derivatives of [(2-(Diphenylphosphino)ethyl)cyclopentadienyl]tricarbonylmetalates: Reactions with Free Radicals

“…Diagnostic structural parameters that define the M′{Ni(η 3 -L)}(CO) 3 (μ-η 5 :η 1 -Cp PPh ) fragments of 1 − 6 are nearly identical to those of four-legged piano stool M′{CuPMe 3 }(CO) 3 (μ-η 5 :η 1 -Cp PPh ) (M′ = Cr ( 13 ), Mo ( 14 ); Figure ) . While the phosphine and η 3 -L units render the Ni centers of 1 − 6 electronically unsaturated like Ni(η 5 -C 5 Me 5 ), 1 − 6 and W{Ni(η 5 -C 5 Me 5 )}(CO) 3 (η 5 -C 5 H 4 Me) ( 15 ; Figure ) feature dramatically different M′−Ni binding modes. In paramagnetic 15 the W(CO) 3 (η 5 -C 5 H 4 Me) group interacts with the Ni(η 5 -C 5 Me 5 ) unit via three semibridging CO ligands and a Ni−W bond with significant multiple-bond character; 15 is isolobal with nickelocene.…”

Coordination and Dehydrogenation of Diphosphine–Borane Ph2PCH2PPh2·BH3 at a Heterometallic MoRe Center to Give an Agostic Boryl-Bridged Derivative

“…Binuclear heterometallic complexes displaying metal–metal multiple bonds are a particularly interesting group within this large family of species, as the intermetallic multiple bond additionally provides electronic and coordinative unsaturation to the dimetal center, which further enhances its reactivity . Research in this area, however, has been relatively ill-developed for organometallic complexes, due to scarcity in the number of available substrates suitable for extensive reactivity studies …”

Trapping of an Heterometallic Unsaturated Hydride: Structure and Properties of the Ammonia Complex [MoMnCp(μ-H)(μ-PPh2)(CO)5(NH3)]

“…However, there are precedents indicating that organometallic substrates with heterometallic multiple bonds have a large potential for the stoichiometric and catalytic activation of small molecules. For instance, Chetcuti et al studied complexes with Co=Ni bonds able to induce under mild conditions different isomerisation processes, as well as regiospecific C-C couplings and P-C bond cleavages [8,9], while Suzuki et al studied unsaturated complexes with Zr(µ-H) 3 Ir or TaIr(H) 2 centres able to activate C-H, N-H and O-H bonds [10,11]. The same group found that the unsaturated hydride [Cp*Ru(µ-H) 4 OsCp*] undergoes addition reactions at a rate much higher than the rates measured for the corresponding homonuclear complexes having Ru-Ru or Os-Os bonds [12].…”

“…However, there are precedents indicating that organometallic substrates with heterometallic multiple bonds have a large potential for the stoichiometric and catalytic activation of small molecules. For instance, Chetcuti et al studied complexes with Co=Ni bonds able to induce under mild conditions different isomerisation processes, as well as regiospecific C-C couplings and P-C bond cleavages [8,9] [14]. Given the similarity between the above Re complex and the ammonia complexes mentioned above, we wondered if the latter could also be used as synthetic equivalents of the elusive [MoMCp(μ-H)(μ-PR2)(CO)5] hydrides.…”