Nickel carbonyl physical properties

During occupational exposure, respiratory absorption of soluble and insoluble nickel compounds is the major route of entry, with gastrointestinal absorption secondary (WHO 1991). Inhalation exposure studies of nickel in humans and test animals show that nickel localizes in the lungs, with much lower levels in liver and kidneys (USPHS 1993). About half the inhaled nickel is deposited on bronchial mucosa and swept upward in mucous to be swallowed about 25% of the inhaled nickel is deposited in the pulmonary parenchyma (NAS 1975). The relative amount of inhaled nickel absorbed from the pulmonary tract is dependent on the chemical and physical properties of the nickel compound (USEPA 1986). Pulmonary absorption into the blood is greatest for nickel carbonyl vapor about half the inhaled amount is absorbed (USEPA 1980). Nickel in particulate matter is absorbed from the pulmonary tract to a lesser degree than nickel carbonyl however, smaller particles are absorbed more readily than larger ones (USEPA 1980). Large nickel particles (>2 pm in diameter) are deposited in the upper respiratory tract smaller particles tend to enter the lower respiratory tract. In humans, 35% of the inhaled nickel is absorbed into the blood from the respiratory tract the remainder is either swallowed or expectorated. Soluble nickel compounds... 

The lack of any knowledge on the structure and bonds of these compounds was responsible for the poor results. In fact, when tetracarbonyl-nickel was first prepared, Werner s theory had not as yet been postulated, and even later the theory was not extended to the carbonyls because they were considered anomalous compounds, owing to their chemical and physical properties. 

The physical properties have the expected trend, while the thermal instability of the palladium derivative appears anomalous and can perhaps be attributed to a combination of kinetic and thermodynamic factors. (Platinum should be thermodynamically more unstable but kinetically stable.) In any case, it appears that Ni(PF3)4 is more stable than nickel carbonyl, and this confirms that the palladium and platinum tetratri-fluorophosphine derivatives could be prepared. 

While the physical properties of the metal carbonyls are distiiiatly different from those of both carbon monoxide and the particular metal, much of the chemical behavior of the carbonyls is typical of that of the metal and of carbon monoxide. Thus, nickel carbonyl reacts vigorously with bromine to form nickel bromide and hberate carbon monoxide ... 

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