Adduct Formation of Tantalum(V)‐ and Niobium(V) Fluoride with Neutral Group 15 Donor Ligands, an Example for Ligand Induced Self‐Ionization

Abstract

Abstract. The complexes [MF 4 (py) 6 ]·½CH 3 CN (M = Nb, Ta) were obtained from niobium and tantalum pentafluoride by reaction with the donor ligands pyridine (py), 2,2Ј-bipyridine (2,2Ј-bipy), and bis(diphenylphosphanyl) ethane (dppe) in acetonitrile solution. The complexes were characterized by their vibrational spectra and, in case of the pyridine and dppe adducts, by their crystal structure. The pairs of corresponding

Six-coordinate NbF5 and TaF5 complexes with tertiary mono-phosphine and -arsine ligands

“…The chemical shifts were little changed on cooling the solution to 193 K, but the latter feature resolved into the characteristic 10 line pattern of [NbF 6 ] À ( 1 J NbF = 334 Hz) (Fig. 2b) 6 ] which showed a 1:2:1 triplet ( 2 J PF = 70 Hz) confirming the presence of two phosphines as the trans isomer (Fig. 3).…”

“…Reactions of MF 5 with monodentate pnictogen ligands. The reaction of the MF 5 and PMe 3 in Et 2 O using a 1:3 molar ratio of metal pentafluoride:PMe 3 was undertaken in an attempt to prepare the self-ionisation products with eight-coordinate cations, [MF 4 (PMe 3 ) 4 ][MF 6 ], analogous to the diphosphine complexes described recently [5]. These reactions initially precipitated the neutral [MF 5 (PMe 3 )] species which were identified by their characteristic NMR spectra.…”

“…with PMe 3 , using a similar method were unsuccessful, since the MeCN preferentially coordinated to the hard metal centres [5]. The complexes [MF 4 (Ph 2 PCH 2 CH 2 PPh 2 ) 2 ][MF 6 ] are also known [6].…”

“…Both types of complex with O-, N-and S-donor ligands have been well characterised in recent studies [1][2][3][4], and we reported very recently [5] the first complexes with neutral bidentate phosphorus or arsenic donor ligands, [MF 4 (diphosphine) 2 ][MF 6 ] (M = Nb or Ta, diphosphine = o-C 6 H 4 (PMe 2 ) 2 , Me 2 P(CH 2 ) 2 PMe 2 , Et 2 P(CH 2 ) 2 PEt 2 or o-C 6 H 4 (PPh 2 ) 2 ) and the diarsine analogues [MF 4 (o-C 6 H 4 (AsMe 2 ) 2 ) 2 ][MF 6 ]. These were prepared by reaction of the appropriate MF 5 with the Group 15 donor ligand in anhydrous MeCN, and spectroscopic and X-ray structural data showed that they all contain distorted eightcoordinate cations and regular octahedral anions.…”

“…Niobium and tantalum pentafluorides are very strong, hard Lewis acids which form complexes with many neutral donor ligands; the commonest stoichiometries are the six-coordinate [MF 5 L] (L = monodentate ligand) and the ''self ionisation'' products [MF 4 L 2 ][MF 6 ] and [MF 4 L 4 ][MF 6 ] with six-and eight-coordinate cations, respectively [1]. Both types of complex with O-, N-and S-donor ligands have been well characterised in recent studies [1][2][3][4], and we reported very recently [5] the first complexes with neutral bidentate phosphorus or arsenic donor ligands, [MF 4 (diphosphine) 2 ][MF 6 ] (M = Nb or Ta, diphosphine = o-C 6 H 4 (PMe 2 ) 2 , Me 2 P(CH 2 ) 2 PMe 2 , Et 2 P(CH 2 ) 2 PEt 2 or o-C 6 H 4 (PPh 2 ) 2 ) and the diarsine analogues [MF 4 (o-C 6 H 4 (AsMe 2 ) 2 ) 2 ][MF 6 ].…”