Complex formation between nickel(0) and a phosphaalkene: Influence of the second ligand on the η1- and η2-coordination mode

Golden Age of Fluorenylidene Phosphaalkenes–Synthesis, Structures, and Optical Properties of Heteroaromatic Derivatives and Their Gold Complexes

“…Immediate reaction can also be judged by the intense color change, i.e., red-shifted absorption, upon addition of the gold­(I) solution. Complex [AuCl* 3 ] showed a 31 P NMR resonance of 182.4 ppm, which corresponds to a coordination shift (Δδ 31 P) of −87.2 ppm and is indicative of a strong Au–P interaction. − Notably, the proton in proximity to the Au center was shifted to higher frequencies (9.91 ppm compared to 8.58 ppm), while the proton at position-1, which was directly positioned in the ring current of the Mes* substituent, was shifted further to lower frequencies (5.27 ppm compared to 5.43 ppm). The corresponding disubstituted derivative 2 showed similar behavior upon complexation to gold­(I).…”

Structural Diversity and Dynamics of Nickel Complexes with Ambidentate Phosphorus Heterocycles

“…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.…”

“…Among the aforementioned unsaturated bonds, the PC bond is of particular interest: typically the phosphorus LP σ orbital and the π orbital of the P–C bond are HOMOs of nearly equal energies, and the level of the π* LUMO is low. − Therefore, it might be expected that phosphaalkenes in complexes with transition metals will exhibit either η 1 coordination via the phosphorus LP or η 2 coordination of the Dewar–Chatt–Duncanson (DCD) type via the P–C bond. , Significant progress has been made to this end in the coordination chemistry of the phosphorus analogues of usual unsaturated organic ligands that demonstrate abundant coordination chemistries partially due to the phosphorus LP. For example, there are η 1 - through η 6 -coordinated, phosphorus-substituted ligands. − …”

Protonation‐Induced Rearrangement of an Oxaphosphirane Complex

“…[25] Herein, we report that the protonation of a coordinated oxaphosphirane leads to a complex bearing a novel side-onbonded PÀC ligand, which can be described as a methylene phosphonium ion; DFT calculations provide information on the low-energy pathway to its formation and the effects of substituents on the process.The oxaphosphirane complex 1 [17] was reacted with triflic acid in dichloromethane to selectively yield complexes 2 a,b in 86:14 ratio (Scheme 1). Product 2 a displayed a 31 P signal at d = 73.8 ppm in the NMR spectrum with a very small tungsten-phosphorus coupling constant 1 J W,P = 113.2 Hz, indicative of side-on bonding to the metal complex moiety, [26] whereas 2 b showed a 31 P signal at d = 72.3 ppm with even smaller 1 J W,P coupling (97.9 Hz). Neither 1 H and 13 C NMR spectroscopy nor IR spectroscopy on 2 a,b were particularly informative, and attempts to separate 2 a from 2 b by column chromatography or crystallization failed.The superior crystallizing properties of carborane anions as counterions for reactive cations [27] suggested that X-ray structural information on 2 a,b might be obtained using a carborane acid instead of triflic acid.…”

“…The oxaphosphirane complex 1 [17] was reacted with triflic acid in dichloromethane to selectively yield complexes 2 a,b in 86:14 ratio (Scheme 1). Product 2 a displayed a 31 P signal at d = 73.8 ppm in the NMR spectrum with a very small tungsten-phosphorus coupling constant 1 J W,P = 113.2 Hz, indicative of side-on bonding to the metal complex moiety, [26] whereas 2 b showed a 31 P signal at d = 72.3 ppm with even smaller 1 J W,P coupling (97.9 Hz). Neither 1 H and 13 C NMR spectroscopy nor IR spectroscopy on 2 a,b were particularly informative, and attempts to separate 2 a from 2 b by column chromatography or crystallization failed.…”