Synthesis and X-ray structures of silver and gold guanidinate-like complexes. A Au(ii) complex with a 2.47 Å Au–Au distance

Abstract

The structures of the tetranuclear silver(I), [Ag4(hpp)4], and the dinuclear gold(II), [Au2(hpp)2Cl2], (hpp = 1,3,4,6,7,8-hexahydro-pyrimido[1,2-a]pyrimidinate) guanidinate-like bases are reported and show a silver-silver distance of 2.8614(6) A and a gold-gold distance of 2.4752(9) A, the shortest Au-Au bond heretofore reported.

Dimethyl-, diphenyl- and cyclotetramethylene silylchloride derivatives of guanidine, their synthesis and structure. Formation of pentacoordinated silicon compounds and an unexpected diionic disila-diguanidinium dichloride

“…Published similar structures consist of one Sn compound (hpp) 2 Sn 2 Cl 2 by Foley [28] and structures of the type (hpp) 2 M 2 (M = Au-Cl [29], Cu [30], AlMe 2 [31]) all containing chelating N ! M bonds.…”

“…To investigate the k n Si-coordination patterns and the possibility of dimeric structures, single crystal X-ray analysis (XRD) ( Table 1) and 29 Si NMR analyses of the compounds were carried out. Analytically pure crystals of 2 and 3 for XRD analysis were obtained from cold pentane and of 4 from cold toluene.…”

“…The N(5)-C(10) = 1.325(3) Å distance in 4 is the longest N(5)-C(10) bond length of the complexes 2-4 (Scheme 3). Compounds 2-4 were also analysed in solution with 29 Si NMR over the range 60 to À190 ppm. The in solid-state pentacoordinate compound 3 shows one signal in C 2 D 2 -Cl 4 at À77.3 ppm and in CDCl 3 at À77.2 ppm.…”

“…1 H and 13 C NMR show the compounds to have a symmetric guanidine unit in solution. 29 Si NMR analysis shows the structures, in selected solvents, to be of k 5 Si-type for 3 and to the major part for 2. Compound 4, on the other hand, is of ionic k 4 Si-type.…”

Cupriphication of gold to sensitize d 10 –d 10 metal–metal bonds and near-unity phosphorescence quantum yields

“…Additional theoretical insights for 3d σ -5d σ /3d π -5d π /3d δ -5d δ bonding are addressed based on dispersive density functional theory (DFT) computations (discussed below). To end this crystallographic argument, however, we consider the quintuple M-M bond by Power and coworkers (14) for trigonal Cr(I) d 5 centers and the related less-than-quintuple M-M bonds in trigonal paddlewheels of non-d 5 systems recently reviewed by Murillo (15) in terms of the role of symmetry reduction in increasing the M-M bond order (16). In a similar manner, the symmetry reduction from an idealized D ∞h to C 2v in the coordination sphere of especially the Cu1 atom in 4a crystals renders stronger mixing of 3d σ/π/δ orbitals with the corresponding 5d σ/π/δ orbitals of the Au1 atom in the next-neighbor molecule at the expense of mixing with the orbitals of the two pyrazolate ligands or the Au2 and Au1 atoms in the same molecule.…”