Rare Neutral Diphosphine Complexes of Scandium(III) and Yttrium(III) Halides

Abstract

Reaction of MePCHCHPMe or o-CH(PMe) (L-L) with a suspension of ScI or YI in MeCN solution under rigorously anhydrous and oxygen-free conditions produced the highly unusual complexes [ScI(L-L)], [YI(MePCHCHPMe)], and [YI{o-CH(PMe)}MeCN]. X-ray crystal structures reveal that the scandium complexes adopt seven-coordinate, pentagonal-bipyramidal geometries with chelating diphosphines, while the eight-coordinate [YI{o-CH(PMe)}MeCN] is dodecahedral. The complexes were characterized by microanalysis and IR and multinuclear NMR spectroscopy. Solid-state NMR data (Sc, Y,P) and variable-temperature solution NMR data (H, P{H}, Sc) are presented and compared, leading to the conclusion that the same species are present in both the solid state and CHCl solution. Attempts to prepare complexes with other scandium halides and with aryl diphosphines and o-CH(AsMe) are briefly described.

Trimethylscandium

“…Furthermore, a 45 Sc NMR experiment showed only one signal at 290.8 ppm, corroborating that complex 1 is the single scandium-containing product formed in this reaction (Figures and S4, Table ). The chemical shift of 290.8 ppm for 1 ranges at the low-field end previously observed for six- to eight-coordinate complexes. − For direct comparison, tetrahydroborato coordination seems to result in better shielded species ([Sc­(BH 4 ) 3 ], 113.3 ppm). The 45 Sc shift range for diamagnetic compounds has been found to span approximately 450 ppm (e.g., 396 ppm for [Sc­{N­(SiMe 3 ) 2 } 3 ] to −50 ppm for [Sc­(tetramethylcarbamide) 6 ] 3+ ), while δ iso of the 45 Sc nuclei was shown to increase for lower coordination numbers. , …”

“…34−40 ] 3+ ), while δ iso of the 45 Sc nuclei was shown to increase for lower coordination numbers. 34,38 X-ray diffraction (XRD) measurements revealed the solidstate structure of 1 to be consistent with the known rare-earth metal tetramethylaluminate complexes (Figure 3). 7,21−26 Also, the experimental solid-state structure of [Sc(AlMe 4 ) 3 ] confirms the structure calculated in an earlier publication quite well.…”

Group 3 metal trihalide complexes with neutral N-donor ligands – exploring their affinity towards fluoride

“…The modest quadrupole moment of 45 Sc (I = 7/2) means that resonances are observed in many systems, but couplings to other nuclei are often lost in the line broadening, unless the scandium is in a high symmetry environment. 17,34,38,39 Since these complexes are the first examples of scandium fluoride species with neutral ligands, there are no comparable literature data, but the chemical shifts of the chloro-species are reasonable compared to data on other ScCl 3 adducts. 34,38,39 Adding further small aliquots of [NMe 4 ]F in CH 3 CN initially led to depletion of the resonances assigned to the mixed chloro/fluoro complexes, and enhancement of the broadened quartet at δ = 104 ppm, attributed to [ScF 3 (Me 3 -tacn)] (Fig.…”

“…In work with other early d-block systems, we noted that the corresponding metal iodides and iodo-complexes were often more soluble in weakly coordinating solvents, probably due to lower lattice energy, although the gain in solubility comes at the cost of even greater moisture sensitivity. 17,33,34 In the present study we synthesised complexes with Me 3 -tacn and terpy, which give examples of pseudo-octahedral complexes with fac and mer geometries for scandium, respectively, although for Y and La higher coordination numbers were often produced. The known 26 The reaction of [ScCl 3 (thf ) 3 ] with terpy in anhydrous CH 3 CN gave mer-[ScCl 3 (terpy)] (Fig.…”

Neutral and cationic tungsten(vi) fluoride complexes with tertiary phosphine and arsine coordination

“…Through judicious choice of the metal source and the specific pnictine, recent work has established the existence of homoleptic phosphine complexes with Group 1 cations, including the distorted octahedral [M{o-C 6 H 4 (PMe 2 ) 2 } 3 ] + cations (M = Li, Na) 7 and a series of seven-and eight-coordinate complexes with the hard, oxophilic Sc(III) and Y(III) ions. 8 Tungsten hexafluoride, which contains tungsten in its highest possible oxidation state, is known to form complexes with a variety of hard Lewis bases, mostly neutral N-donor ligands. [9][10][11][12][13][14][15][16][17] Well-documented examples including [WF 6 (2-F-py)] (capped trigonal prism), 13 [WF 6 (py) 2 ] (bicapped trigonal prism), 14 [WF 6 (2,2 0 -bipy)] (structure unknown) 16 and the [WF 4 (2,2 0 -bipy) 2 ] 2+ cation (distorted dodecahedron).…”