FULL PAPER N,N-Dialkylcarbamato Lanthanide Complexes, a Series of Isotypical Coordination Compounds Ulrich Baisch, [a,b] Daniela Belli Dell’Amico,* [a] Fausto Calderazzo, [a] Luca Labella, [a] Fabio Marchetti, [a] and Alessandra Merigo [a,c] Keywords: Coordination modes / Lanthanides / Lanthanide contraction The preparations of the N,N-dialkylcarbamato complexes with analytical formulae [Ln(O 2 CNR 2 ) 3 ] (Ln = Pr, Nd, Eu, Gd, Ho, Er, Yb, Lu, R = iPr; Ln = Nd, Eu, Gd, R = Bu; Ln = Nd, R = Et), using [LnCl 3 (ether) x ] (ether = THF or dimethoxyethane, DME), NHR 2 , and CO 2 are reported. X-ray diffraction of the diisopropylcarbamato derivatives, including a reinvestig- Introduction The synthesis, characterization, and reactivity of N,N-di- alkylcarbamato transition metal complexes have been ex- tensively studied in these laboratories and elsewhere. [1-6] As far as lanthanide (Ln) derivatives are concerned, the struc- turally characterized examples have resulted from work car- ried out within this research group, [7,8] with the sole excep- tion of the heteroleptic binuclear complex [Sm 2 (C 5 Me 5 ) 4 (THF){μ-η 2 -:η 1 -NN(CO 2 )Ph 2 }], prepared [9] by carbonation of the precursor [Sm 2 (C 5 Me 5 ) 4 {μ-η 2 -:η 1 - NNPh 2 }]. Moreover, structurally defined homoleptic de- rivatives of lanthanides with oxygen donors are rather rare. A literature survey has in fact shown that, with these re- strictions, even the well-established classes of the β- diketonato [10-12] and carboxylato [13,14,15] complexes are not extensively represented. However, it appears that when bulky coordinated ligands are present, isostructural be- havior may be more easily observed. This is evidenced by the synthesis of the isopropoxy μ 5 -oxo derivatives of general formula [Ln 5 (μ 5 -O)(OiPr) 13 ] which have been shown to crystallize in the P2 1 /n (no. 14) space group for Ln = Nd, Gd, Er, i.e. over a range of nine atomic numbers. [16] Recently, a preliminary communication from these laboratories showed that the metrical data of the isotypical tetranuclear complexes [Ln 4 (O 2 CNiPr 2 ) 12 ] allowed the lan- [a] Universita ` di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, 56126 Pisa, Italy E-mail: belli@dcci.unipi.it [b] Present address: Department Chemie der Ludwig-Maximilians- Universität München, Butenandtstrasse 5-13 (Haus D), 81377 München, Germany [c] Present address: Lucchini C. R. S., Viale della Resistenza 2, 57025 Piombino, Livorno, Italy Eur. J. Inorg. Chem. 2004, 1219-1224 DOI: 10.1002/ejic.200300649  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1219 ation of [Yb 4 (O 2 CNiPr 2 ) 12 ], showed these complexes to be tetranuclear and isotypical over a range of 12 atomic num- bers. The lanthanide contraction has been evaluated based on the lengths of four different types of Ln-O bond. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) thanide contraction in these complexes to be evaluated in the sequence from neodymium to ytterbium. [17] In this paper, the preparation of the derivatives [Ln(O 2 CNR 2 ) 3 ] (R = iPr, Ln = Pr, Nd, Eu, Gd, Ho, Er, Lu; R = Et, Ln = Nd; R = Bu, Ln = Nd, Eu, Gd) and the full details of the crystal and molecular structures of the isotypical com- pounds [Ln 4 (O 2 CNiPr 2 ) 12 ] (Ln = Nd, Eu, Gd, Ho, Er, Yb, Lu) are reported. Results and Discussion The carbamato complexes [Ln(O 2 CNR 2 ) 3 ] have been mainly prepared [7,8,17] starting from the derivatives [LnCl 3 (ether) x ] (ether = THF or dimethoxyethane, DME), [18] which have a low nuclearity and react promptly with NHR 2 and CO 2 according to Equation (1). [LnCl 3 (ether) x ] + 6 NHR 2 + 3 CO 2  (1) [Ln(O 2 CNR 2 ) 3 ] +3 [NH 2 R 2 ]Cl + x ether As previously reported, in the cases of erbium and ytter- bium, [7,8,17] the unsolvated chlorides LnCl 3 have been found to be useful starting materials for the synthesis of the carba- mato complexes. Consistent with the fact that erbium and ytterbium are late lanthanide elements, and in the hypoth- esis that the chemical properties of these compounds are mainly governed by the ionic radius of the central metal cation, the preparation of the carbamato derivative was also attempted with lutetium trichloride. This has now been found to react with the NHiPr 2 /CO 2 system giving the cor- responding carbamato derivative in good yield. Conversely, this synthetic route met with failure for the lighter lantha-