Pentahydridobis trimethylphosphine iridium V

A 250-ml. three-necked flask is fitted with a magnetic stirring bar and a condenser surmounted by an N2 inlet and bubbler system. The flask is charged with 1 g. (1.7 mmoles) of trimethylphosphonium tetrachlorobis(trimethylphosphine)iridate(l — ) [an equivalent amount oftrichlorotris(trimethylphosphine)iridium(III) may be used] 

Pentahydridobis(trimethylphosphine)iridium(V) is a white crystalline solid which melts with decomposition at 70°. It decomposes rapidly in air and slowly in an inert atmosphere, though repurification through sublimation is easy. The infrared spectrum contains a strong metal-hydrogen stretching absorption at 1920 cm.-1. The 1H spectrum in toluene-d8 consists of a pseudo-triplet of intensity 18 at t8.26 (/p CH3 = 4 Hz.) for the methyl protons and a triplet of intensity 5.5 at t19.73 (,/P lrH = 14 Hz.). The 31P spectrum, after selective decoupling of the methyl protons, consists of a sextet at + 192.1 p.p.m. from external trimethyl phosphite. 

In benzene the complex slowly decomposes with elimination of hydrogen to give a new species whose structure is uncertain. The pentahydride (or its decomposition products) catalyzes the exchange of benzene hydrogen with gaseous deuterium.8 Reaction with trimethylphosphine is rapid with loss of hydrogen to yield a 

Shriver, The Manipulation of Air-sensitive Compounds, McGraw-Hill Book Company, New York, 1969. 

Tetrakis(organophosphorus)metal hydrides (containing one, two, three, or four hydride nuclei) have recently attracted considerable attention in connection with their stereochemical behavior1 and reaction chemistry.2 Detailed nuclear magnetic resonance studies and line-shape analyses have substantiated stereochemical nonrigidity in many of these complexes in solution and have yielded mechanistic information about the intramolecular-exchange processes.3 

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