Syntheses of Phosphinine-Based Tripodal Ligands

Abstract

The syntheses of several tripodal phosphinine‐based ligands are presented. 1,3,2‐Diazaphosphinine (1) undergoes Diels−Alder reactions with tris‐(propynyl)phenylsilane to yield tris‐(1,2‐azaphosphinine)phenylsilane 6. This intermediate serves as precursor for the preparation of two tripodal ligand. First, tris(phosphinine)phenylsilane (7) is obtained from the reaction with trimethylsilylacetylene. Under more drastic conditions, compound 6 reacts with 4‐octyne to yield the tripodal ligand 8 containing six n‐propyl groups. Reaction of 8 with [W(CO)5(THF)] affords the corresponding W(CO)3 complex 9 whose structure was confirmed by an X‐ray crystallographic study. The synthesis of two extended tripodal ligands 12 and 13 containing three phosphinine units each connected to the same CH linker by dimethylsilyl groups was also studied. As a prerequisite, the precursor tris(propynyldimethylsilyl)methane (10) was synthesized by reaction of three equivalents of propynyllithium with tris(bromodimethylsilyl)methane. Reaction of excess 1 with 10 yielded the corresponding tris(dimethylsilyl‐1,2‐azaphosphinine)methane (11) as an intermediate. The formation of ligands 12 and 13 was achieved by reacting 11 with trimethylsilylacetylene or 4‐octyne, respectively, in excess. The reaction of ligand 13 with [W(CO)5(THF)] in toluene yielded the corresponding W(CO)3 complex 14 which was structurally characterized.

Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

“…The two crystallographically-characterized Mo–phosphinine complexes show shorter bond lengths of ca. 2.38 Å for [Mo­(PC 5 H 5 ) 6 ] and 2.3565(4) Å for a bridging dinuclear complex, and seven crystallographically characterized W–phosphinine compounds have bond lengths ranging from 2.36 to 2.57 Å. ,− …”

Multidentate ligand systems featuring dual functionality

“…The rigid and intrinsically welldefined coordination geometry of the ligand is already obvious in the organic precursor in which the central methine C-H group is orientated towards all P-donor moieties. 84 The two-step synthesis of the palladium complex 45 involves pre-coordination of two of the P donor atoms of the ligand to PdCl 2 (square-planar complex) and subsequent reaction with Ag[BF 4 ] producing the trigonal bipyramidal, overall neutral complex 45 with all three phosphane donors residing in the equatorial position (one 31 P NMR signal at d = 49.4). The carbanion (d(Pd-C) = 214 pm) and the chlorine ligand (d(Pd-Cl) = 241.6 pm) occupy the axial positions.…”

Unexpected Multiple Coordination Modes in Silyl-Bridged Bis(phosphinine) Complexes

“…Phosphinines (the phosphorus analogue of pyridine) are fascinating ligands in coordination chemistry because they contain phosphorus in an unusual, multiply bonded environment. − This gives them unique properties including diagnostic 31 P­{ 1 H} NMR resonances at high chemical shifts in an “aromatic” region and variable binding modes such as η 6 binding − and nondirectional η 1 binding. − Electronically, phosphinines function as π-accepting ligands − but can also function as noninnocent ligands due to facile nucleophilic attack at P under certain conditions. − Monodentate phosphinine ligands − and hybrid ligands, where the phosphinine is connected to another donor, − ,,− are being increasingly explored in coordination chemistry and catalysis; however, ligands based on multiple phosphinine units are much rarer. , Examples include a trans -coordinating diphosphinine, diphosphorus analogue of 2,2′-bipyridine ( A , tmbp: 4,4′,5,5′-tetramethyl-2,2′-biphosphinine, Chart ), ,, and very recent work on multidentate phosphanyl phosphinines . Using a very versatile diazaphosphinine methodology, − Mathey, Le Floch, and co-workers synthesized and studied the coordination chemistry of silyl-substituted multidentate phosphinine ligands with Ir, Rh, , Au, and W­(CO) 3 . , A bis­(phos­phinine) with a SiMe 2 linker and featuring 3,3′-Ph substituents was also synthesized (Chart , B ), and although its reduction chemistry was studied in detail...…”

“…43 Using a very versatile diazaphosphinine methodology, 44−47 Mathey, Le Floch, and co-workers synthesized and studied the coordination chemistry of silylsubstituted multidentate phosphinine ligands with Ir, Rh, 46,48 Au, 49 and W(CO) 3 . 46,50 A bis(phosphinine) with a SiMe 2 linker and featuring 3,3′-Ph substituents was also synthesized (Chart 1, B), 45 and although its reduction chemistry was studied in detail, 51 its coordination chemistry was not explored. Building on our recent work on the coordination chemistry and catalytic applications of 2-phosphinophosphinines (Chart 1, C), 20,21,52 including with group 6 carbonyl fragments (Chart 1, D), 53 we have now studied the coordination chemistry of a SiMe 2 -linked bis(phosphinine), and demonstrate key differences in its binding modes as well as the synthesis of the first hydride/phosphinine complex.…”