Hydride Complexes of the Transition Metals

TLDR: In this paper, the physical properties of the metal-hydrogen bond are discussed, and the role of transition metal hydrides in homogeneous catalysis has also been discussed.

Abstract: Publisher Summary This chapter discusses those discrete complexes of hydride that contain one or more hydrogen atoms bonded directly to a transition metal by an essentially covalent, two-electron bond. It is convenient and to some extent chemically significant to classify hydrides according to the nature of the other ligands attached to the metal. Accordingly, the following classes are recognized: (1) Complex hydrides with tertiary phosphines and related ligands, (2) Carbonyl hydrides: (a) mononuclear, (b) polynuclear, (3) π-Cyclopentadienylcarbonyl hydrides, (4) Bis(π-cyclopentadienyl) hydrides, (5) Cyanide hydrides, (6) Hydride complexes containing nitrogen ligands, and (7) “Pure” hydrides: complexes with hydride as the sole ligand. The chapter highlights the physical properties of the metal-hydrogen bond. The hydrogen atoms in metal-hydride complexes occupy accepted coordination positions, and the most reliable determinations indicate M–H distances compatible with an essentially normal covalent bond. It appears that the high field shift of M-hydrogens is largest for first-row transition metals; the complexes of metals of the second and third transition series show shifts that are about 25% less than those of the lightest group members. The role of transition metal hydrides in homogeneous catalysis has also been discussed in the chapter.