Coordination of a Diphosphine–Ketone Ligand to Ni(0), Ni(I), and Ni(II): Reduction-Induced Coordination

Abstract

The coordination chemistry of the diphosphine− ketone ligand 2,2′-bis(diphenylphosphino)benzophenone ( Ph dpbp) with nickel is reported. The ketone moiety does not bind to Ni(II) in the complex ( Ph dpbp)NiCl 2 , whereas reduction to Ni(I) or Ni(0) induces η 2 (C,O) coordination of the ketone to form the pseudotetrahedral complexes ( Ph dpbp)NiCl and ( Ph dpbp)Ni(PPh 3 ). DFT calculations indicate that the metal− ketone bond is dominated by π back-donation; hence, Ph dpbp functions as a hemilabile acceptor ligand in this series of complexes.

Periodic Trends in the Binding of a Phosphine‐Tethered Ketone Ligand to Fe, Co, Ni, and Cu

“…As imilart rend was found for the bands in ATR-IR spectroscopy;t he C=O Figure 1. [15] Both of theset rends suggest that the C=Ob ond is increasingly,a lthough only slightly,w eakened upon the complexation of Ph dpbp to Fe, Co, and Ni. Aco-crystallized toluene molecule and hydrogen atoms are omitted for clarity;ellipsoids are shown at 50 %p robability level.…”

“…1 HNMR signals that range from À1.4 to 14.1 and À3.7t o1 8.7 ppm for products 2 and 3,r espectively,i ndicate the formation of paramagnetic complexes. [15] As ystematic comparison of the series of compounds 2-4 provides further insight into the interaction between the un-boundC =Of ragment and the metal. [19] Single-crystal X-ray structure determinations of complexes 2 and 3 revealed that both exhibit ad istorted tetrahedral geometry aroundt he M II centerwithout coordination of the C=Omoiety,which is analogous to the previously reported( Ph dpbp)NiCl 2 complex (4).…”

“…The latter,l ess common binding mode has been proposed in intermediate structures for the Cu-catalyzed addition of Grignardr eagents, [5,6] Ru-catalyzed hydrogenation reactions, [7,8] and oxidative additiono fa rylketone CÀCb onds. [15] The ketone moiety does not bind to the Ni II Cl 2 fragment butb inds in an h 2 (C,O) fashion upon reduction of the nickel center from Ni II to Ni I or Ni 0 ;h ence,i ta cts as a hemilabile acceptor ligand. [12] The IrÀ(CÀO) motif was described as the intermediate betweena nh 2 ketone complex (Ir III )a nd an iridaepoxide( Ir V ) structure.…”

“…[13,14] Seekingadirect access to ketone-based p complexeso ff irst-row transition metals,w er ecently investigated the coordination chemistry of the diphosphine-ketone ligand 2,2'-bis(diphenylphosphino)benzophenone [8] ( Ph dpbp, 1)w ith nickel( Scheme 1). [15] The ketone moiety does not bind to the Ni II Cl 2 fragment butb inds in an h 2 (C,O) fashion upon reduction of the nickel center from Ni II to Ni I or Ni 0 ;h ence,i ta cts as a hemilabile acceptor ligand.…”

Formation of Palladium η2‐Bound Chalcogenoketones across a Pd+−C− Bond

“…The C−Pd distance (2.176(3) Å) was also lengthened compared to values found in similar complexes . The 13 C NMR shift for the ketone carbon was observed as a broad singlet at 160.4 ppm, significantly upfield from the corresponding value in 2,2′‐bis(diphenylphosphino)benzophenone (196.8 ppm) . Interestingly, the 31 P NMR spectrum exhibits two broad singlets at 39.4 ppm ( Pi Pr 2 ) and −37.2 ppm ( P Me 3 ) instead of the similar AX 2 spin system observed in 2 , 3 , and 4 .…”