Neutron diffraction analysis of the first stable hydride derivative of a divalent group-14 metal

A single-crystal neutron diffraction study at 20 K has revealed accurate hydride ligand positions in the first stable hydride derivative of a divalent group-14 metal, [2,6-Trip2C6H3Sn(\u3bc-H)]2\ub74C6H6, Trip = 2,4,6-tri-isopropylphenyl [B.E. Eichler, P.P. Power, J. Am. Chem. Soc. 122 (2000) 8785]. In the solid state this dimeric complex assumes a trans C2h geometry with two bridging hydrides (Sn\u2013H 1.943(7) \uc5, angle C\u2013Sn\u2013H 92.4(2)\ub0, angleSn\u2013H\u2013Sn\u2032 106.9(3)\ub0, angle H\u2013Sn\u2013H\u2032 73.1(3)\ub0). The bulky Trip ligand serves to stabilize the Sn\u2013H bonds. The tin atoms carry lone pairs, and, as determined previously by X-ray diffraction and reported by Eichler and Power, the tin coordination accordingly is pyramidal as evidenced by the sum of the three bond angles around tin of 257\ub0. To our knowledge this is the first neutron diffraction study of a tin hydride complex to be reported. The neutron diffraction measurements were carried out using the time-of-flight Laue SCD instrument at the Argonne Intense Pulsed Neutron Source

Terminal gold-oxo complexes

In contradiction to current bonding paradigms, two terminal Au-oxo molecular complexes have been synthesized by reaction of AuCl3 with metal oxide-cluster ligands that model redox-active metal oxide surfaces. Use of K10[alpha2-P2W17O61].20H2O and K2WO4 (forming the [A-PW9O34]9- ligand in situ) produces K15H2[Au(O)(OH2)P2W18O68].25H2O (1); use of K10[P2W20O70(OH2)2].22H2O (3) produces K7H2[Au(O)(OH2)P2W20O70(OH2)2].27H2O (2). Complex 1 crystallizes in orthorhombic Fddd, with a=28.594(4) A, b=31.866(4) A, c=38.241(5) A, V=34844(7) A3, Z=16 (final R=0.0540), and complex 2 crystallizes in hexagonal P6(3)/mmc, with a=16.1730(9) A, b=16.1730(9) A, c=19.7659(15) A, V=4477.4(5) A3, Z=2 (final R=0.0634). The polyanion unit in 1 is disorder-free. Very short (approximately 1.76 A) Au-oxo distances are established by both X-ray and 30 K neutron diffraction studies, and the latter confirms oxo and trans aqua (H2O) ligands on Au. Seven findings clarify that Au and not W is present in the Au-oxo position in 1 and 2. Five lines of evidence are consistent with the presence of d8 Au(III) centers that are stabilized by the flanking polytungstate ligands in both 1 and 2: redox titrations, electrochemical measurements, 17 K optical spectra, Au L2 edge X-ray absorption spectroscopy, and Au-oxo bond distances. Variable-temperature magnetic susceptibility data for crystalline 1 and 2 establish that both solids are diamagnetic, and 31P and 17O NMR spectroscopy confirm that both remain diamagnetic in solution. Both complexes have been further characterized by FT-IR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and other techniques