Dithiocarbamatocarboxylate (DTCC) Ligands—Building Blocks for Hard/Soft-Heterobimetallic Coordination Polymers

Abstract

Four zinc/platinum(II) heterobimetallic coordination polymers with dithiocarboxylate-functionalized carboxylate (DTCC) ligands were prepared by different synthetic approaches and characterized by elemental analyses, IR and NMR ( 1 H, 13 C, and 195 Pt) spectroscopy, thermal analyses coupled with mass spectrometry (TG/DTA/MS), and single-crystal and powder X-ray diffraction studies. Sequential syntheses via the carboxylic acid substituted platinum dithiocarbamates and zinc acetate revealed crystalline products in good to excellent yields. One-pot preparations from potassium DTCC salts, K 2 PtCl 4 , and ZnCl 2 led to comparable products, thus demonstrating the high selectivity of the two donor groups toward platinum(II) and zinc. [SSC-N(Me)CH 2 COO] 2− and [SSC-N(CH 2 COO)-(CH 2 COOH)] 2− , DTCC ligands derived from sarcosine and iminodiacetic acid, respectively, were found to form planar zigzag chains with zinc and platinum(II) ions, while the use of the L-proline-derived ligand [SSC-NC 4 H 7 COO] 2− results in a helical structure. In the case of [SSC-N(CH 2 COO) 2 ] 3− , two-dimensional arrays are formed. All compounds are thermally stable up to 240−400 °C under nitrogen.

From zero- to three-dimensional heterobimetallic coordination polymers with the [Pt{SSC-N(CH2COO)2}2]4− metalloligand

“…The IR spectra of compounds 2 containing transition metals display two or three strong ν(C=O) bands between 1590 and 1480 cm -1 , which is significantly shifted to smaller wavenumbers as compared to the parent [Pt(H2L)] (1; 1701 and 1682 cm -1 ) and indicates therefore the full deprotonation of the carboxylic acid moieties. 9 However, the spectra of some compounds (hydrated 2-Mg, 2-Ba, 2-Co, and 2-Cu) show additional bands above 1600 cm - [16][17][18][19][20] and those favouring highly bridging coordination modes (Ca-Ba, Cd). [21][22][23][24] Moreover, the IR spectra do not necessarily reflect the binding situations in the crystal structures, as in the products the carboxylate coordination can change in the course of isolation as a result of crystal water loss.…”

“…Figures S10 and S11). 9 The temperature of decomposition of the ligand scaffold is very different and ranges from 182 °C (2-Cu) to 470 °C (2-Sr). Interestingly, among the alkaline-earth metal derivatives 2-Sr is the thermally most stable product, while the decomposition temperatures for 2-Ca and 2-Ba are significantly lower and similar at 430 °C.…”

“…Solution NMR spectroscopy in D2O revealed the typical picture that has been previously observed with 2-Zn. 9 This comprises one 1 H NMR singlet signal at ca. 4.2 ppm (CH2), which is broadened for 2-Ni due to moderate paramagnetism and not visible for 2-Mn, 2-Co, and 2-Cu (tentatively due to strong paramagnetism).…”

“…In recent contributions, we have shown that dithiocarbamate-functionalized carboxylates (DTCCs) can coordinate selectively to a to a soft (thiophilic) and a hard (oxophilic) metal center at the same time. 9,10 DTCCs are readily available from cheap starting materials, allowing an amino acid to react with carbon disulfide under alkaline conditions (Scheme 1). 11 Heterobimetallic CPs with DTCC ligands are most conveniently synthesized in a sequential approach.…”

“…The heterobimetallic target products are subsequently obtained when the protonated metalloligand is treated with an acetate of an oxophilic metal. Following this approach, we have prepared Zn/Pt CPs with various DTCC ligands, 9 as well as Zn/Pd and Zn/Ni CPs with the iminodiacetic acid derived ligand {SSC-N(CH2COO)2} 3-(= L). 10 The CPs having bis(carboxylate) Pt(II) metalloligands derived from sarcosine and L-proline extend in one dimension, while the tetrakis(carboxylate) metalloligands [M(L)2] 4-(M = Ni, Pd, Pt) form two-dimensional assemblies with Zn 2+ ions in the solid state.…”