Remarkable Product Diversity in the “Self-Organized” Reaction of Deprotonated Acetonitrile with Chlorophosphines

Functional Short-Bite Ligands: Synthesis, Coordination Chemistry, and Applications of N-Functionalized Bis(diaryl/dialkylphosphino)amine-type Ligands

The aim of this review is to highlight how the diversity generated by N-substitution in the well-known short-bite ligand bis(diphenylphosphino)amine (DPPA) allows a fine-tuning of the ligand properties and offers a considerable scope for tailoring the properties and applications of their corresponding metal complexes. The various N-substituents include nitrogen-, oxygen-, phosphorus-, sulfur-, halogen-, and silicon-based functionalities and directly N-bound metals. Multiple DPPA-type ligands linked through an organic spacer and N-functionalized DRPA-type ligands, in which the PPh2 substituents are replaced by PR2 (R = alkyl, benzyl) groups, are also discussed. Owing to the considerable diversity of N-functionalized DPPA-type ligands available, the applications of their mono- and polynuclear metal complexes are very diverse and range from homogeneous catalysis with well-defined or in situ generated (pre)catalysts to heterogeneous catalysis and materials science. In particular, sustained interest for DPPA-type ligands has been motivated, at least in part, by their ability to promote selective ethylene tri- or tetramerization in combination with chromium. Ligands and metal complexes where the N-substituent is a pure hydrocarbon group (as opposed to N-functionalization) are outside the scope of this review. However, when possible, a comparison between the catalytic performances of N-functionalized systems with those of their N-substituted analogs will be provided.

Bis[bis(diphenylphosphinoyl)acetonitrile-κ2O,O′]copper(II)

The title complex, [Cu(C₂₆H₂₀NO₂P₂)₂], contains a central Cu^II atom surrounded by two homoleptic bidentate ligands, which form two five-membered chelate rings. The Cu atom binds to four O atoms, resulting in a four-coordinate square-planar complex. The asymmetric unit contains half of the complex, the other half being completed by inversion symmetry. The Cu—O bond lengths have similar distances, viz. 1.9153 (10) Å for the pair opposite (trans) each other and 1.9373 (10) Å for the other (trans) pair. The P—O bond lengths are 1.5250 (11) Å, indicating significant electron delocalization across the O—P—C—P—O atoms in the chelate ring, resulting in a longer P—O bond length when compared to a formal double-bond P=O character (much shorter at approximately 1.47 Å). The two inter­secting O—Cu—O angles are both linear at 180°, whilst the remaining L-shaped O—Cu—O bond angles are 88.26 (5) and 91.74 (5)°. The C—C N fragment is slightly distorted from linearity at 177.44 (19)° and the C N bond length of 1.151 (2) Å indicates predominantly triple-bond character.

[μ-Bis(diphenylphosphanyl)acetonitrile-κ2P:P]bis[chloridogold(I)]

The title complex, [Au₂Cl₂(C₂₆H₂₁NP₂)], has an intra­molecular Au⋯Au inter­action of 3.1669 (4) Å, but no inter­molecular Au⋯Au inter­actions in the solid state. The Cl—Au—P bond angle of 176.84 (7)° is slightly distorted from linearity. The P—C bond length to the phenyl group is shorter [1.810 (7) Å] than the P—C bond length [1.876 (7) Å] to the bridging carbon, indicative of the flexibility of the bidentate bite of the ligand. The C—C N fragment is essentially linear at 179.5 (9)° and the C N bond length of 1.125 (11) Å indicates predominantly triple-bond character. In the crystal packing, there are no hydrogen-bonding or aurophilic inter­actions between the mol­ecules.