Activation of C–H bond by cis-[Pt(NO3)2(PPh3)2], cyclometallation of tetramethylthiourea

The Role of Anions in Addressing the Outcome of the Reaction of Tetramethylthiourea with cis‐PtII(phos)2 Moieties (phos = PPh3 or ${1 \over 2}$dppe), Cyclometallation vs. Hydrolysis to Monothiocarbamato, and the Crystal Structure of trans‐Bis(N‐dimethylmonothiocarbamato)bis(triphenylphosphane)platinum(II)

“…[1] However, to our surprise, the reaction of 6 with tmtu did not afford 3, but a mixture, which, according to 31 P NMR spectroscopy (Table 1), contains essentially two products 8 and 9 (minor component), with no detectable signal from 3. Slow diffusion of hexane into a CH 2 Cl 2 solution of this mixture gave crystals, which were found to be trans-[Pt(PPh 3 ) 2 (mtc) 2 ] through X-ray analysis, see below.…”

“…Reactions of tmtu with these three complexes, in CH 2 Cl 2 solutions, give the corresponding salts of the cationic cyclometallated complex 3, which were characterised by elemental analyses and by comparison of their NMR spectra with those of the already described nitrate derivative. [1] When the reactions between tmtu and compounds 5 were followed by 31 P NMR spectroscopy, we observed, in both cases, the fast formation of a species 10, which shows [1] .…”

“…We have recently found that the reaction of cis-[Pt-(PPh 3 ) 2 (NO 3 ) 2 ] (1) with tmtu does not give the disubstituted product cis-[Pt(PPh 3 ) 2 (tmtu) 2 ] 2+ , but that the initially formed cis-[Pt(PPh 3 ) 2 (NO 3 )(tmtu)](NO 3 ) (2) transforms into the cyclometallated complex [Pt(PPh 3 ) 2 (tmtu*-C,S)](NO 3 ) (3) [tmtu*, tetramethylthiourea deprotonated at one methyl group], with formation of nitric acid (Scheme 1). [1] This reaction, performed at room temperaScheme 1.…”

“…[1] Such facile cyclometallation is clearly favoured by the lability of the nitrate ion cis to tmtu in 2; detachment of this ionic ligand produces a vacant coordination site which can interact with a C-H bond of a methyl group of tmtu, activating the bond towards deprotonation. [2,3] The proton is then captured by a "free" (i.e.…”

“…uncomplexed) NO 3 -ion to give nitric acid. [1] In order to better understand the role of the anion either as a ligand, or as a base, we decided to investigate the reaction of tmtu with a series of other cisPt II (PPh 3 ) 2 complexes with various anionic ligands and we found that the product of the reaction depends on the nature of the anions present. Thus, while cyclometallation also occurs with cis-[Pt(PPh 3 [4] to the best of our knowledge this is the first X-ray structure of a Ptmtc derivative.…”