Pt–Ag clusters and their neutral mononuclear Pt(ii) starting complexes: structural and luminescence studies

Abstract

The mononuclear complexes [Pt(bzq)(S^S)] [S^S = pyrrolidinedithiocarbamate (pdtc 1), dimethyldithiocarbamate (dmdtc 2)] were prepared by reaction of [Pt(bzq)(NCMe)(2)]ClO(4) with an equimolecular amount of [NH(4)(pdtc)] and [Na(dmdtc)·2H(2)O] respectively in MeOH. Reactions of 1 and 2 with AgClO(4) in 1 : 1 and 2 : 1 molar ratios rendered the heteropolinuclear compounds [{Pt(bzq)(S^S)Ag}(2)](ClO(4))(2) (S^S = pdtc 3, dmdtc 4) and [{Pt(bzq)(S^S)}(2)Ag](ClO(4)) (S^S = pdtc 5, dmdtc 6) respectively. The X-ray studies on single crystals of 3 and 4 showed that both consist of tetranuclear [Pt(2)Ag(2)] clusters with the Pt-Ag and the Ag-Ag distances in the range of those corresponding to Pt-Ag dative bonds and argentophilic interactions. In 3 the tetranuclear [Pt(2)Ag(2)] clusters are connected into infinite polymeric chains by Pt···Pt metallophilic interactions (Pt···Pt = 3.1890(7) Å). The X-ray study on a single crystal of 5 showed that it is a polymer based on trinuclear [Pt(2)Ag] clusters containing two unsupported Pt-Ag dative bonds and connected by Ag-S bonds in such a way that the "Pt-Ag-S-Pt-Ag-S" atoms draw a zigzag polymeric chain. TD-DFT calculations carried out for 1 indicate that the lowest energy absorption band in CH(2)Cl(2) can be described as a mixture of (1)MLCT, (1)IL and (1)L'LCT transitions. Powdered samples of 1 at 298 K and 77 K show a green-yellow emission band coming mainly from a (3)LC excited state. However complex 2 shows "luminescence thermochromism": the colour of its luminescence changes from green-yellow at 77 K to orange-red at 298 K. The emission of the Pt-Ag clusters, 3-6, in the solid state, are due to excimeric (3)ππ and/or (3)MMLCT (dσ* →π*) low-lying excited states, indicating that the presence of silver in the clusters makes the "Pt(bzq)(S^S)" fragments interact to a large extent through Pt···Pt and/or π-π interactions. Solid 3 is a highly selective vapochromic compound towards acetonitrile although this behaviour is not fully reversible.

Unusual Metal–Metal Bonding in a Dinuclear Pt–Au Complex: Snapshot of a Transmetalation Process

“…[19,20] In [29] with PPh 3 . The crystal structure of 1 has been determined by X-ray diffraction and shows the expected square planar coordination around the platinum (see Figure S3 and Table S1 The crystal structure of 2 has been determined by X-ray diffraction (see Figure 1, and a selection of relevant bond distances and angles is included in the caption.…”

“…A number of metals are known to fulfill this role but Pt II (d 8 ) is the donor center par excellence, [1,4,9,[14][15][16][17][18] while among the acceptors, Ag I (d 10 ) is by far the most representative example. [19,20] In contrast, very few examples of Pt II →Au I (d 10 ) have been fully characterized. [21][22][23][24] From a structural point of view, several binding modes for the coordination of platinum (II) fragments to Lewis acidic metals are known.…”

Neutral benzoquinolate cyclometalated platinum(II) complexes as precursors in the preparation of luminescent Pt–Ag complexes

“…Metal-metal bonds can act as a link between different subassemblies, making them a valuable tool in molecular or crystal engineering, and giving rise to a variety of structures, from simple linear bimetallic compounds to infinite one-dimensional chains [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Furthermore, some of these complexes show interesting photophysical and photochemical properties [1][2][3][4][5]7,8,11,17,27,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48], which in some cases have been exclusively attributed to the presence ...…”

“…M bonds [5,[12][13][14][15][16][17]21,22,26,[28][29][30]46,[49][50][51][52][53][54][55][56][57] the acidic M center being Cu(I), Ag(I), Au(I), Cd(II), Hg(II), Tl(I), Sn(II) and Pb(II). In the course of our recent research, we have studied the use of strong ligand field cyclometalated C^N ligands, such as 7,8-benzoquinolinate (bzq), in the coordination sphere of the Pt precursor [13,14,27,47]. Thus, the use of [Pt(bzq)(C 6 F 5 )(L)] nÀ (L = C 6 F 5 , n = 1 [13,14,27]; L = Me 2 CO, PPh 3 , pyPh 2 , tht, MeCN, n = 0 [30]) allowed us to prepare bimetallic complexes Pt-M (M = Cd [14], Ag [13,27,30]), trimetallic ''sandwich'' complexes Pt-Ag-Pt [13,30], or metallic infinite chain systems Á Á ÁPt-Ag-Pt-Ag-PtÁ Á Á [27,47].…”

“…In the course of our recent research, we have studied the use of strong ligand field cyclometalated C^N ligands, such as 7,8-benzoquinolinate (bzq), in the coordination sphere of the Pt precursor [13,14,27,47]. Thus, the use of [Pt(bzq)(C 6 F 5 )(L)] nÀ (L = C 6 F 5 , n = 1 [13,14,27]; L = Me 2 CO, PPh 3 , pyPh 2 , tht, MeCN, n = 0 [30]) allowed us to prepare bimetallic complexes Pt-M (M = Cd [14], Ag [13,27,30]), trimetallic ''sandwich'' complexes Pt-Ag-Pt [13,30], or metallic infinite chain systems Á Á ÁPt-Ag-Pt-Ag-PtÁ Á Á [27,47]. The Pt-Ag complexes, in addition to the intermetallic bonds, also contain very unusual g 1 bonding interactions between the silver(I) center and the C ipso of the bzq ligand and pÁ Á Áp stacking interactions between the aromatic rings of the bzq ligands are present.…”