A Study of Through-Space and Through-Bond J_PP Coupling in a Rigid Nonsymmetrical Bis(phosphine) and Its Metal Complexes

Abstract

A series of representative late d-block metal complexes bearing a rigid bis(phosphine) ligand, iPrP-Ace-PPh (L, Ace = acenaphthene-5,6-diyl), was prepared and fully characterized by various techniques, including multinuclear NMR and single-crystal X-ray diffraction. The heteroleptic nature of the peri-substituted ligand L allows for the direct observation of the J couplings in the P{H} NMR spectra. Magnitudes of J are correlated with the identity and geometry of the metal and the distortions of the ligand L. The forced overlap of the phosphine lone pairs due to the constraints imposed by the rigid acenaphthene skeleton in L results in a large J of 180 Hz. Sequestration of the lone pairs, either via oxidation of the phosphine or via metal chelation, results in distinct changes in the magnitude of J. For tetrahedral d complexes ([LMCl], M = Zn, Cd, Hg), the J is comparable to or larger than (193-309 Hz) that in free ligand L, although the P···P separation in these complexes is increased by ca. 0.4 Å (compare to free ligand L). The magnitude of J diminishes to 26-117 Hz in square planar d complexes ([LMX], M = Ni, Pd, Pt; X = Cl, Br) and the octahedral Mo complex ([LMo(CO)], 33 Hz). Coupling deformation density calculations indicate the through-space interaction dominates in free L, while in metal complexes the main coupling pathway is via the metal atom.

Using JPP to Identify Ni Bidentate Phosphine Complexes In Situ

“…Two-bond couplings, such as the J PP values arising from the through-Ni coupling pathway, are expected to have a negative sign. 47,70,89,90 Simulations show that this is not always true for Ni bidentate phosphine complexes, with many complexes having a positive J PP (Figure 2). Generally, the 3C complexes have more a negative J PP in comparison to 2C complexes by ∼40 Hz, and Ni II complexes have a more negative J PP in comparison to Ni 0 by ∼60 Hz regardless of linker length.…”

Sterically Encumbered 4,5‐Bis(diphenylphosphino)acenaphthene Ligand and Its Ni(II), Pd(II), Pt(II), and Cu(I) Complexes

“…Peri ‐substituted bis‐phosphino acenaphthenes are usually prepared from 5,6‐dibromoacenaphthene by stepwise halogen–lithium exchange followed by P–C coupling with the desired chlorophosphine. [ 25 ] In this scheme the two phosphorus substituents are introduced on the aromatic scaffold in two different steps preparing first the 5‐bromo‐6‐phosphino derivatives and, after a second bromine–lithium exchange, the bis‐phosphine compound thus allowing to obtain also non‐symmetrically substituted acenaphthenes. However, being our target a symmetrically substituted derivative we attempted a single step reaction in which the bis‐lithium derivative was produced directly from 5,6‐dibromoacenaphthene using 2 equivalents of n BuLi and reacted with chlorodiphenylphosphine.…”

“…[ 24 ] Recently, the group of Kilian has reported a detailed study of the coordination chemistry of the unsymmetrical ligand i Pr 2 P‐Ace‐PPh 2 (Figure 1) with several transition metal ions showing that the ligand forms square‐planar complexes with group 10 d 8 metal ions {[( i Pr 2 P‐Ace‐PPh 2 )MX 2 ], M = Ni, Pd, Pt; X = Cl, Br}. [ 15,25 ] This type of complexes are potentially relevant for our studies on anion carriers but we realized that the simple symmetric Ph 2 P‐Ace‐PPh 2 ( L , Figure 1) was not described in the literature. We therefore prepared Ph 2 P‐Ace‐PPh 2 and here we describe its synthesis and the characterization of the ligand and of its complexes with Pd(II), Pt(II), Ni(II), and Cu(I), including single‐crystal X‐ray structure determination, along with a preliminary study of the ionophoric activity of the Pd and Cu complexes.…”

Stabilization of the Elusive Antimony(I) Cation and Its Coordination Complexes with Transition Metals

“…Notably,t he 31 P{ 1 H} spectrum of L in CDCl 3 gives as ingle resonance at À6.4 ppm. Thec rystal structure [25] of L (Figure S73) exhibits bonding parameters very similar to the related bis(phosphine)s. [26] Compound 1 has been obtained in moderate yield (45 %) as crystals from the reaction combining SbCl 3 , L and trimethylsilyl triflate (TMSOTf) taken in THF in 1:2:3r atio at room temperature;a long with the formation of colorless crystals (40 %y ield) of the PÀPb onded diphosphonium dication 2 (Scheme 1a). Orange crystals of Sb I cation 1 settles at the bottom of the undisturbed THF solution in aflask upon standing,w hile the lighter crystals of 2 remained floating in the upper meniscus.T hus,b oth the compounds could be separated quantitatively by simple decantation techniques.…”