Spectral and Structural Characterization of Amidate-Bridged Platinum−Thallium Complexes with Strong Metal−Metal Bonds

Abstract

The reactions of [Pt(NH3)2(NHCOtBu)2] and TlX3 (X = NO3-, Cl-, CF3CO2-) yielded dinuclear [{Pt(ONO2)(NH3)2(NHCOtBu)}Tl(ONO2)2(MeOH)] (2) and trinuclear complexes [{PtX(RNH2)2(NHCOtBu)2}2Tl]+ [X = NO3- (3), Cl- (5), CF3CO2- (6)], which were spectroscopically and structurally characterized. Strong Pt-Tl interaction in the complexes in solutions was indicated by both 195Pt and 205Tl NMR spectra, which exhibit very large one-bond spin-spin coupling constants between the heteronuclei (1J(PtTl)), 146.8 and 88.84 kHz for 2 and 3, respectively. Both the X-ray photoelectron spectra and the 195Pt chemical shifts reveal that the complexes have Pt centers whose oxidation states are close to that of Pt(III). Characterization of these complexes by X-ray diffraction analysis confirms that the Pt and Tl atoms are held together by very short Pt-Tl bonds and are supported by the bridging amidate ligands. The Pt-Tl bonds are shorter than 2.6 Angstrom, indicating a strong metal-metal attraction between these two metals. Compound 2 was found to activate the C-H bond of acetone to yield a platinum(IV) acetonate complex. This reactivity corresponds to the property of Pt(III) complexes. Density functional theory calculations were able to reproduce the large magnitude of the metal-metal spin-spin coupling constants. The couplings are sensitive to the computational model because of a delicate balance of metal 6s contributions in the frontier orbitals. The computational analysis reveals the role of the axial ligands in the magnitude of the coupling constants.

New structural motifs of silver and gold complexes of pyridine-functionalized benzimidazolylidene ligands

“…[Ag(L2)Cl] (7), generated from the reaction of 1-benzyl-3-picolylbenzimidazolium chloride and Ag 2 O, reacted with AgBF 4 led to isolation of the coordination polymer 8 (Scheme 2). The compound shows a singlet at 188.7 ppm in its 13 C NMR spectrum assignable to the carbene carbon atom, and the chemical shift is well consistent with those of the known silver-NHC complexes in the range of 213.7-163.2 ppm [59][60][61] (10), shown in Scheme 3. Compounds 7 and 10 did not show the resonance signals of carbenic carbons in their 13 C NMR spectra.…”

“…Our recent research focuses on the design and preparation of multinuclear metal complexes or coordination polymers containing direct metal-metal interactions, and a number of metal complexes having short Pt-Ag, Pt-Tl, Pt-Pt, Pt-Pd, Ag-Ag, and Cu-Cu contacts have been characterized [58][59][60][61][62]. Heteroarene functionalized N-heterocyclic carbene ligands have proven to be good donating ligands for the assemblage of new metal clusters [63][64][65][66][67][68][69][70] 2 ](PF 6 ) 2 , (L1 = 1,3-bis(picolyl)benzimidazolylidene, L2 = 1-benzyl-3-picolylbenzimidazolylidene, L3 = 1,4-di(Nbenzylbenzimidazoliumyl)but-2-yne) containing bidentate or tridentate functionalized benzimidazolin-2-ylidene ligands.…”

Magnitude of Finite‐Nucleus‐Size Effects in Relativistic Density Functional Computations of Indirect NMR Nuclear Spin–Spin Coupling Constants

“…Like the Hg 2 2 + crown ether system, M6 is a "record holder", in this case for the largest indirect spin-spin coupling between two different nuclei. [51,52] The finite nucleus effects for the couplings between Pt and light atomic ligands are not as large as those for Hg, around 9 %, but still quite substantial. For the coupling between the two heavy metals, PtÀTl in the complex M6, the finite-nucleus effects cause a reduction of around 20 %, in between that for the Hg 2 2 + crown ether complex and the bare Hg 2 2 + ion calculated with the TZ2P3 basis ( Table 2).…”

NMR properties of platinumthallium bonded complexes: analysis of relativistic density functional theory results

“…The second series of complexes, [fPt NO 3 NH 3 2 L 2 gTl NO 3 29 Their structures are depicted in Fig. 2.…”

“…9 Previously, we reported preliminary DFT computations of the Pt-Tl coupling constants of complex VI. 29 The importance of the bulk solvent effects to reproduce accurately the experimental data was already highlighted. In the present work, the calculation of the Pt-Tl coupling constants was extended to the complex VII.…”