Copper polyhydrides

Abstract

We continue1 here our exploration of soluble phosphine complexes of Cu(I) hydrides directed toward improved understanding of the conversion of CO/H2 mixtures to methanol catalyzed by oxides of copper and zinc.1 2 We established previously the unusual (positive value) *H chemical shift and fluxionality of the hydride ligands in [HCuP(p-tolyl)3]6,1 but two X-ray diffraction studies3 have failed to establish the structural preference of the hydride ligands in such polyhydrides. We report here the resolution of this question, as well as the surprising variability of aggregate size in these clusters.Hydrogenolysis of Cu-O-t-Bu bonds (eq 1, in THF) is a quite y4(CuO-í-Bu)4 + L + H2 -7"(HCuL)" + Z-BuOH (1) versatile synthetic method for copper phosphine polyhydrides. Thus, for L = P(NMe2)3 we isolate red crystals of H6Cu6[P-(NMe2)3]6. The analogous deuteride (from D2 in eq 1) shows an infrared spectrum identical (400-4000 cm"1) with that of the hydride, precluding location of metal hydride vibrations. If NMR spectra are recorded at -70 °C, a 31P['Hj singlet (112 ppm) and 'H(31P¡ NMe singlet (2.81 ppm) are detected.4 The 2H NMR spectrum of D6Cu6[P(NMe2)3]6 exhibits a D-Cu resonance at 2.57 (-70 °C, full width at half-height = 7 Hz) devoid of detectable D/P coupling. A single-crystal X-ray diffraction structure determination (Figure 1 A)5 reveals a trigonal-antiprismatic array of six coppers, each with a terminal phosphorus ligand.6 7The Cu6 unit lacks rigorous octahedral symmetry in that the Cu/Cu distances are of two types: six longer ones (2.804 Á) form two parallel equilateral triangles on opposite faces of the trigonal antiprism. The apices of these triangles are interconnected (15)

The Intermetalloid Cluster [(Cp*AlCu)6H4], Embedding a Cu6 Core Inside an Octahedral Al6 Shell: Molecular Models of Hume–Rothery Nanophases

“…Similar anomalies were also seen in compounds such as [(R 3 PCuH) 6 ] (R = Ph, NMe 2 ) and polymeric CuH. [15] The spectroscopic and analytical data are consistent with the proposed composition and structure of 2, and the molecular structure was unambiguously determined by single-crystal X-ray diffraction analysis (Figure 1). Crystal data, the details of the structure determination, and selected bond lengths and angles are given in the Supporting Information, Table S1 and S2.…”

Mechanistic Studies of Copper(I)-Catalyzed 1,3-Halogen Migration

“…Although we suspected that the phosphine-supported copper(I) hydride was the active catalyst, these species are known to form dimers and other higher-order oligomers and aggregates, which could complicate the mechanistic picture. 12 Fortunately, we have recently developed an asymmetric version of the 1,3-halogen migration reaction, which permitted a nonlinear effects study to gain insight into the nuclearity of the catalyst (Figure 1). 3 The absence of nonlinear effects support the assumption that the active catalyst in solution is monomeric in nature and argues against the presence of off-cycle organocopper dimers or higher order aggregates.…”

Molecular Magnesium Hydrides

“…[7] The existing structures and bonding are now well understood and the synthetic methodologies have become ar outine.W ith rational ligand design and advanced synthetic tools,i ncreasing numbers of such compounds are expected to be reported. [17d] Despite being an electropositive s-block metal, the molecular hydride chemistry of magnesium is surprisingly rich, especially with the multi-metallic hydride clusters.T he Mg À Hb onds apparently have areasonably covalent character when in suitable ligand environments.T he high Lewis acidity of Mg 2+ together with the variability of its coordination numbers help to expand the range of nuclearity and the resulting structures.T his diverse class of compounds is gradually coming of the age to allow comparison with the numerous hydride clusters of copper [42] or of the rare-earth metals. [16] Thechemistry of low-valent Mg I and one-electron transfer processes involving the MgÀHbond are new endeavors.…”

“…[16] Thechemistry of low-valent Mg I and one-electron transfer processes involving the MgÀHbond are new endeavors. [17d] Despite being an electropositive s-block metal, the molecular hydride chemistry of magnesium is surprisingly rich, especially with the multi-metallic hydride clusters.T he Mg À Hb onds apparently have areasonably covalent character when in suitable ligand environments.T he high Lewis acidity of Mg 2+ together with the variability of its coordination numbers help to expand the range of nuclearity and the resulting structures.T his diverse class of compounds is gradually coming of the age to allow comparison with the numerous hydride clusters of copper [42] or of the rare-earth metals. [43] We hope that this Review will inspire chemists to develop new magnesium-hydride-based materials and to find useful applications of this earthabundant element.…”