Complete Chalcogenation of Tin(II) Centers in an Imidotin Cluster

Abstract

The use of inorganic rings or clusters as precursors to industrially important materials such as inorganic polymers, [1] nanomaterials, [2] or semiconductors [3] represents an active area of contemporary inorganic chemistry. In the latter category the design of suitable precursors for the low bandgap semiconductors SnE (E = Se, Te), which have applications in thermoelectric devices and for optoelectronic materials, is of current interest. [4,5] Suitably chosen complexes containing terminal Sn = E bonds would appear to be candidates for this purpose.[6] In particular, imidotin chalcogenides of the type [(ESnm 3 -NR) 4 ] (E = Se, Te) may act as singlesource precursors of these binary semiconductors by the energetically favorable elimination of the diazene RN = NR. However, investigations of the reactions of the neutral cluster 4 ] with chalcogens have revealed that oxidation is limited to one tin(ii) center for E = Te (A) or two tin(ii) centers in the case of E = Se (B). [7] To address this synthetic challenge, we have adopted a strategy that was successful for the generation of the previously inaccessible PÀTe ligands[8]That approach involved the formation of anionic imidophosphorus(iii) reagents by metalation with NaH or nBuLi, prior to reaction with tellurium.[8]Application of this methodology to imidotin cages involves the use of the amido/imido seco-cube [Sn 3 (m 3 -NtBu)(m 2 -NtBu)(m 2 -NHtBu) 2 ] (1) reported by Veith et al. [9] We disclose here that the anionic cluster in [Li(thf) 4 ] [(thf)LiSn 3 (m 3 -NtBu) 4 ] (2 a), which is readily generated by dilithiation of 1 with nBuLi, exhibits a dramatic increase in the reactivity of the tin(ii) centers towards chalcogens compared to that of the neutral cluster 4 ] with three equivalents of C 10 H 7 NHLi.[10] The 1 H NMR spectrum of complex 2 a exhibits two resonances in a 3:1 ratio for the tBu protons, and a single resonance is observed in the 119 Sn NMR spectrum; both of these observations are consistent with local C 3 symmetry for the anion in 2 a. The 7 Li NMR spectrum of 2 a shows two well-separated resonances, indicating that the [Sn 3 Li(m 3 -NtBu) 4 ] cluster remains intact, even in THF solution.The reaction of 2 a with slightly more than three equivalents of selenium in THF readily produces the tristannaselone 3 a in essentially quantitative yields within several minutes at room temperature. Complex 3 b was obtained in a similar manner from 2 b and selenium. The tristannatellone 4 can also be synthesized from 2 a and a slight excess of tellurium at room temperature in about 1 h. However, the reaction proceeds more rapidly with gentle heating (20 min, 40 8C) to give 4 in 73 % yield. The mild reaction conditions necessary to produce the fully chalcogenated complexes 3 a, 3 b, and 4 are in striking contrast to those used to prepare the partially chalcogenated complexes A and B, which require boiling toluene and long reaction times (24-48 h).[7] Clearly, the negative charge in the anion of 2 a results in a dramatic enhancement of the susceptibility of ...

A Tin Analogue of Carbenoid: Isolation and Reactivity of a Lithium Bis(imidazolin‐2‐imino)stannylenoid

“…Attempts to obtain an analytically pure sample of 5 by recrystallization of the crude product were not successful. Hydrogen atoms are omitted for clarity.S elected bond lengths [] and bond angles [8 8]: Sn1ÀN1 2.216(4), Sn1ÀN1# 2.179(5), Sn1ÀCl1 2.525(3), C1ÀN1 1.286 (7), C1À N2 1.384(8), C1ÀN3 1.399 (7);N1-Sn1-N1#78.18 (18), Sn1-N1-Sn1# 101.82 (18), N1-Sn1-Cl1 86.60 (15), N1#-Sn1-Cl1 88.85 (15). [13] However,t he Sn À Na nd Li À Nb ond lengths in 1 and 5 differ only slightly and do not indicate that the structural deviation between the LiN 2 Sn cores (butterfly Figure 3.…”

“…[11a] Notably,high dative bond character was attributed to the Sn À N imino interaction in stannyliumylidene VII and the respective bond length had been determined to be 2.197 (2) . [12d] In contrast to [LiNIPr] 2 ,compound 1 exhibits no contact between the lithium atom and one of the ipso-carbon atoms of the Dip groups.A si sc ommon for lithium stannates that bear nitrogen donor ligands, [15] no bonding interaction between the lithium and the tin atom is detected for 1,a se videnced by the Sn···Li distance of 2.943(9) t hat is larger than the sum of the covalent radii of these atoms (2.67 ). [12d] In contrast to [LiNIPr] 2 ,compound 1 exhibits no contact between the lithium atom and one of the ipso-carbon atoms of the Dip groups.A si sc ommon for lithium stannates that bear nitrogen donor ligands, [15] no bonding interaction between the lithium and the tin atom is detected for 1,a se videnced by the Sn···Li distance of 2.943(9) t hat is larger than the sum of the covalent radii of these atoms (2.67 ).…”

“…[11a] TheL i ÀNb ond lengths of 1.946(9) a nd 2.004(9) i n 1 are comparable to those in the iminolithium dimer [LiNIPr] 2 (1.841(6)-1.992 (6) ). [12d] In contrast to [LiNIPr] 2 ,compound 1 exhibits no contact between the lithium atom and one of the ipso-carbon atoms of the Dip groups.A si sc ommon for lithium stannates that bear nitrogen donor ligands, [15] no bonding interaction between the lithium and the tin atom is detected for 1,a se videnced by the Sn···Li distance of 2.943(9) t hat is larger than the sum of the covalent radii of these atoms (2.67 ). [16] The 119 Sn{ 1 H} NMR spectrum of 1 in [D 8 ]THF displays as inglet at d = À18 ppm, which is significantly shifted to lower field as compared to monomeric trigonal-pyramidal coordinate tin chloride complexes of various 1,3-diketiminato-based ligands (for example (1,3diketimino)SnCl: d( 119 Sn) in ar ange from À118 ppm to À337 ppm).…”

Formation and Reactivity of Organo‐Functionalized Tin Selenide Clusters

“…[20] In all of these cases, intramolecular NÀSn bonding occurs, whichi si mportant for the stabilityo ft he structures; similart o otherp olynuclear aggregates with N!Sn stabilized Sn=Eu nits (E = S, Se, Te ). [21] An example for the extension of the inorganic core is given by the reactiono f[ (SnR 1 ) 4 S 6 ]w ith Na 2 S( as as ul-fide source to initially break up the original clusters caffold) and [Cu(PPh 3 ) 3 Cl].T his yielded[ (R 1 Sn) 2 (CuPPh 3 ) 6 S 6 ], ac luster compound with at ernary inorganic core. [16] The chemistry of discrete organotin selenide compounds shows al ower diversity thus far,even thoughs everal examples based on binuclear Sn/Se units, as mentioned above for the lighter homologs, have been reported.…”

“…[16] The chemistry of discrete organotin selenide compounds shows al ower diversity thus far,even thoughs everal examples based on binuclear Sn/Se units, as mentioned above for the lighter homologs, have been reported. [21][22][23][24] The first clusters with DC or AD topologies, respectively,[ (SnCp(CO) 2 Fe) 3 Se 4 Cl] and [(SnCp(CO) 2 Fe) 4 Se 6 ]( Cp = cyclopentadienyl), were synthesized by using {Cp(CO) 2 Fe}SnCl 3 as ap recursor. [24] The first DCtype tin selenide clusterw ith purely organic ligandstob ep ublished was [Na(MeOH) 2 ][R COO (R COO H) 2 Sn 3 Se 4 ][R COO 2 (R COO H)Sn 3 Se 4 ], obtainedb yi ns itu generation of Na 2 Se in liquid ammonia and subsequenta ddition of R COO HSnCl 3 .…”