Partial and exhaustive hydrolysis of lanthanide N,N-dialkylcarbamato complexes. A viable access to lanthanide mixed oxides

Abstract

Partial hydrolysis (H 2 O/Ln molar ratio = ¼) of lanthanum di-iso-propylcarbamato complex, [La(O 2 CN i Pr 2) 3 ], 1, afforded the tetranuclear µ-oxo derivative [La 4 O(O 2 CN i Pr 2) 10 ], 2, which was structurally characterized by single crystal X-Ray diffraction studies. The carbonatocarbamato derivative of lanthanum, [La 4 (CO 3)(O 2 CNBu 2) 10 ], 3, was prepared by extraction of lanthanum ions from aqueous solution into heptane by the NHBu 2 /CO 2 system. Partial hydrolysis (H 2 O/Ln molar ratio = ½) of N,N-di-iso-propylcarbamato complexes of neodymium, europium, gadolinium and terbium, [Ln(O 2 CN i Pr 2) 3 ], yielded the derivatives [Ln 2 (CO 3)(O 2 CN i Pr 2) 4 ] (Ln = Nd, 4, Eu, 5, Gd, 6). Exhaustive hydrolysis of [Ln(O 2 CNR 2) 3 ] (Ln = Nd, Tb, R = Bu; Ln = Eu, Gd, R = i Pr, Bu) produced hydrated lanthanide carbonates, Ln 2 (CO 3) 3 · n H 2 O. For sake of comparison with a block d metal, the exhaustive hydrolysis of two copper(II) carbamato complexes, [Cu(O 2 CNEt 2) 2 (NHEt 2)] 2 and [Cu(O 2 CNiPr 2) 2 ], was carried out with formation in both cases of the hydrated basic carbonate Cu 2 (OH) 2 (CO 3)·nH 2 O. The exhaustive hydrolysis of mixtures of cerium and lanthanum or cerium and terbium N,N-dibutylcarbamato complexes allowed the preparation of mixed oxides containing the two metals in the desired molar ratio, via the intermediate formation of the corresponding mixed carbonates.

Recent Advances in the Chemistry of Metal Carbamates

“…Indeed, the extraction method described above related to homoleptic lanthanide complexes (Section 3.1) proceeds to the formation of mixed carbonato-carbamato species, [NH 2 Bu 2 ] 2 [Ln 4 (CO 3 )(O 2 CNBu 2 ) 12 ] (Ln = Tb, Sm, Eu, Tm) (Scheme 33c), in case the separated organic phase is not promptly dried. This is probably ascribable to the quite fast reaction of carbamato ligands with residual traces of water [151,153] [146]. Accordingly, the exhaustive hydrolysis of some lanthanide carbamates (Ln = Ce, Nd, Eu, Gd, Tb) and [Y(O 2 CNBu 2 ) 4 ] led to the carbonates M 2 (CO 3 ) 3 and not the oxides [146,152,154].…”

“…This is probably ascribable to the quite fast reaction of carbamato ligands with residual traces of water [151,153] [146]. Accordingly, the exhaustive hydrolysis of some lanthanide carbamates (Ln = Ce, Nd, Eu, Gd, Tb) and [Y(O 2 CNBu 2 ) 4 ] led to the carbonates M 2 (CO 3 ) 3 and not the oxides [146,152,154].…”

“…For instance, MnCl 2 (THF) 1.6 and FeCl 2 (THF) 1.5 were used in the syntheses of [M(O 2 CNEt 2 ) 2 ] 6 and [M(O 2 CN i Pr 2 ) 2 ] n (M = Fe, Mn) [ 143 ]. In the case of lanthanides, the use of LnCl 3 (ether) x allowed straightforward preparation of [Ln(O 2 CN i Pr 2 ) 3 ] 4 ( Scheme 17 b) and [Ln(O 2 CNBu 2 ) 3 ] (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) [ 23 , 144 , 145 , 146 , 147 ].…”

“…The structure of [Bi(O 2 CN i Pr 2 ) 3 ] 4 is tetrameric, each Bi being coordinated by one chelating ( C/1 ), one bridging ( B/2 ) and one bridging-chelating ( C/2 ) carbamato groups in a distorted pentagonal bipyramidal environment ( Scheme 16 b) [ 135 ]. Instead, N , N -diisopropyl carbamates of Ln(III) (Ln = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb, Lu) are isostructural and exhibit a tetrameric structure with C 2 symmetry and heptacoordinated metal centers ( Scheme 17 b) [ 23 , 145 , 146 , 147 ]. In these complexes, the carbamato ligands adopt three different coordination modes, binding one ( C/1 ), two ( B/2 ) or three ( B/3 ) metal centers, respectively.…”

“…1.65 Tb 0.35 O 3.82 , Ce 1.80 La 0.20 O 3.90 , La 2 CuO 4 , Y 3 Al 5 O 12 and Y 2.98 Nd 0.02 Al 5 O 12 , are finally produced (Scheme 42b)[146,154,297].…”