Synthesis and x-ray crystal structure of the cyclopentadienyl nitrito complex of ytterbium(III), (C5H5)2Yb(NO2) · THF

Nitrite complexes of the rare earth elements

“…In [14], the Ag atom is disordered over two positions which were refined with occupancy parameters constrained to sum to unity. (10) 31.8726 (10) 17.8243 (8) 17.7881 517.8054 710.1729(5) ], all the nitrite ions, both coordinated and free, and the pyridine ligand, are disordered over two positions (sharing one nitrogen atom for one nitrite ion and one oxygen atom for another one), which have been refined with occupancy parameters constrained to sum to unity (fixed to 0.5 for the free nitrite which is disordered around an inversion centre). Restraints on bond lengths and displacement parameters had to be applied for the free nitrite anion, and the two positions of the pyridine molecule, close to one another, were refined as idealized hexagons.…”

“…In the two isomorphous complexes [PPh 4 ] 2 [8] and [PPh 4 ] 2 [9], the three nitrite ions are disordered: two of them (containing N1 and N2) have two components nearly orthogonal to one another while only one oxygen atom is disordered over two positions in the third (N3). The occupancy parameters of all these positions have been refined to values very close to 0.5, then fixed to this value to allow for the mixing of the different positions and their symmetry equivalents (some positions being mutually incompatible).…”

“…5 This series was completed in 2004 with the isolation of La(NO 2 ) 3 , as a coordination polymer. 6 Only six molecular nitrite complexes have been reported with REEs, namely [(Tp Me2,4-Et ) 2 Sm(NO 2 )], 7 [(C 5 H 5 ) 2 Yb(NO 2 )(THF)], 8 [Ln(L)(NO 2 )-(H 2 O)] (Ln = Sm, Eu, L = 2,2′-(biphenyl-4,4′-diylbis(oxy))diacetate), 9 10 From a structural point of view, the rational synthesis and the characterization of well-defined REEs nitrite complexes would therefore afford molecular models to better apprehend the redox chemistry of nitrogen oxides in lanthanide chemistry. Additionally, it has been recently shown that the nitrite anion NO 2 − behaves as an attractive one electron oxidant in the coordination sphere of uranium(III) and uranium(IV), to access uranium-oxo functionalities.…”

“…First, in the absence of a Lewis acidic countercation, pentanitrito REEs complexes ([PPh 4 ] 2 [X], X = 1, 2,4,6,10,11,12) are formed selectively across the series. The formation of hexanitrito complexes is available for all the elements and it requires the presence of Ag + as a cation, presumably to balance the electrostatic inter-ligand repulsion through coordination (as shown in [PPh 4 ] 2 [X], X = 3,7,8,9, 13,14). Nonetheless, the coordination of the REE cation varies and it is directly controlled by the metal ionic radius.…”

“…. In complexes [PPh 4 ] 2 [X] (X = 3,6,8,9, 13,14), the nitrito ligands adopt two different coordination modes, namely κ 2 -(O,O) and κ 1 -(O), and we found that the M-O bond distance is ∼0.16 Å shorter for the κ 1 -(O)-bound nitrito ligand, regardless of the nature of the REE or the coordination of Ag I . This finding is in agreement with the 0.15 Å bond difference observed in [PPh 4 ] 2 [UO 2 (κ 2 -NO 2 ) 2 -(κ 1 -NO 2 ) 2 ] 4.…”