Hydrides ligands

Further surveys of the reactivity of HB(C6F5)2 with simple organometallic compounds have led to the discovery of more novel boron-based ligand systems. For example, reactions with Schrock s tungsten methylidyne family L4W(X)=CH63 (L = phosphine, X = Cl, OTf) result in electrophilic attack on the methylidyne ligand hydride abstraction... 

Addition of PF3 to a coordinatively unsaturated complex has been used (method G), and mixed PF3-ligand hydrides can be converted to the corresponding hydrochloride or dichloride systems by treatment with HX (usually HC1 or HBF4) and Et4NCl (method H). 

Hydride ligands are the most versatile of all organometallic ligands. Hydrides can coordinate to a single metal (terminal coordination), bridge two p-R, 4) or three (/U.3-H, 5) metal atoms, or occupy an interstitial position inside a metal polyhedron (6). Hydrides bound to transition metal clusters most commonly bridge two metal atoms. Interconversion... 

The mechanistic steps parallel that of monometallic hydroformylation cycles. Oxidative addition of H2 to the 16e- four-coordinate Rh side of lOr generates the transient intermediate species A. We do not have any spectroscopic data directly supporting any of the complexes labeled with letters in Fig. 7. DFT calculations on all the species in Fig. 7, along with all likely isomers, support the indicated structures. The optimized structures from the DFT calculations generally have somewhat unsymmetrical bridging ligands (hydrides or carbonyls) and more distorted structures than those drawn here for clarity. Complex A rapidly closes up to form the hydride and carbonyl-bridged complex Hr, which is the... 

Electrons from the ligands this depends, naturally on the ligands. For hydrocarbon ligands, the number is equal to the hapto number. Single-bonded ligands (hydride, halide etc) count as 1 (although a bridging halide counts as 2 - a lone-pair donor), while carbenes and carbynes count as 2 and 3, respectively. Lone-pair donors, such as phosphines and CO, count as 2. 

These kinds of studies have been restricted to carbon monoxide ligands, hydride ligands and some organic ligands as isocyanides. With carbon monoxide the ligand migration may occur between ... 

If a complex contains both carbonyl and unsaturated hydrocarbyl ligands, hydride addition may follow both of the available pathways. Not all of the factors controlling the directions taken by such reactions have been elucidated. Generally, - formyl complexes are the kinetic products, whereas, the attack of hydride on unsaturated hydrocarbyl ligands gives file thermodynamic products. 

---