Chelate Ligand‐Controlled η¹‐η² Change of Coordination in Amino(imino)phosphane Ligands and Their Conversion into a Nickelaazadiphosphetidine

Abstract

Amino(imino)phosphanes, compounds containing triply bonding phosphorus of coordination number two, are versatile ligands.".*'Reaction of the nickel complex 1 and the amino(imino)phosphane 2 (molar ratio 1 :3) affords the synthetic building block 3 with terminal P-coordination of the ligand 2. The tridentate ligand 7 reacts with 3 such that the q'-type coordination of the amino(imin0)phosphane ligand is retained in 4, whereas in the reaction of 3 with dppe to give 5 , a change of coordination from the q'-to the q2-type of coordination takes place.[31 5 is the first example of a compound containing a classical side-on coordinated P=N ligand.'4.121 The reaction is steered in a completely different fashion by bpy. Two P=N functions form, via coupling of a P-N bond, the nickelaazadiphosphetidine 6 , the first P2N2 four-membered ringf5] in which a nitrogen atom is replaced by a metal atom (Ni). 3, 4, and 6 form dark red to brownish-black crystals, while 5 forms yellowish-orange crystals;[61 in each case the crystals are readily soluble in benzene, moderately (3 and 4 readily) soluble in pentane, and only very sparingly soluble in acetonitrile.The "P('H}-NMR signal (Table 1) of the nbonded -P=N-ligand in 5 is shifted upfield by about 260 ppm compared to that of free 2 (6=327), the largest shift so far observed in the case of coordinated amino(imino)phosphane ligands (cf. the upfield shift of ca. 155pm in the case of p3-$ coordination[*]). One of the two R2N groups of 6 exhibits hindered P-N rotation at room temperature.The crystal structure analysis"' shows that 2 is side-on coordinated in 5 (Fig. 1) 180.5 (s, A'-P), -4.8 (s, X -P )

Quantum Chemical Calculations of 31P NMR Chemical Shifts in Nickel Complexes: Scope and Limitations

“…Thus, a comparative analysis of calculated versus experimental 31 P NMR shifts for compound 12 allows simple and reliable assignment of its structure as the π complex. This is in full agreement with the X-ray data …”

“…Another example is that of the Ni complexes with amino­(imino)­phosphane ligands, in which a chelate ligand controlled η 1 –η 2 change of coordination may occur. In general, such complexes can be realized as the η 2 and as well as the η 1 complexes (Figure ).…”

Reversal of polarization in amidophosphines: neutral- and anionic-κP coordination vs. anionic-κP,N coordination and the formation of nickelaazaphosphiranes

“…Unfortunately the reaction of [NiCl 2 (PPh 3 ) 2 ] with Li(PhNPPh 2 ) did nor furnish a threemembered ring, but produced instead a dinuclear nickel-nickel bonded species with a bridging anionic PhNPPh 2 moiety. 34 A better structure match for the title compounds is the pseudo square-planar nickel complex I, 35 although here the nickelaazaphosphirane is composed of a nickel(0) center and a neutral amino(imino)phosphine ligand. Not unexpectedly, the three bonds of this metalacycle, namely, Ni-P 2.231(1), Ni-N 1.908(2), P-N 1.646(2) A ˚, are somewhat different from those in the title complexes.…”

Structural Diversity and Dynamics of Nickel Complexes with Ambidentate Phosphorus Heterocycles

“…The majority of cases in the literature concerning transition-metal complexes with coordination to the LP of heteroatom (η 1 type) or to the π system (η 2 , η 3 , η 4 type etc.) of a heterocycle have been described. ,− ,− When both types of binding modes to the same unsaturated bond are presented, e.g., the XC unit (X = N, P), there is an equilibrium between both coordination types, which can be biased toward either, depending on the ligands. ,,,,, In some cases, η 2 bonding may lead to a metallacycle with the creation of two covalent bonds with the atoms at the expense of a double-bond disruption between them. ,,,− , In the case comprising several π systems in the ligand, an exchange between complexes with coordination to different π sites may also occur. ,,,,, …”

“…In this regard, compounds with electron-donor heteroatoms and/or unsaturated bonds are of particular interest as ligands due to the presence of lone pairs (LPs) and π bonds, which provide binding sites to transition metals. − There are many such examples in the literature, e.g., ligands that incorporate CC, − CN, ,− CO, CP, − PN, , and PP , bonds.…”