David H. Kohn

The effect of replacing carbonyl groups by other ligands on the catalytic properties of arenechromium carbonyl complexes

Abstract The activities of a series of areneCr(CO) 2 L complexes in catalytic hydrogenation has been studied and found to be poorer than those of the Cr(CO) 3 analogs. The IR v (CO) changes of these complexes in THF have been shown to have value in predicting catalytic properties.

Structural and catalytic activity studies on phosphine—and phosphite—dicarbonylchromium complexes of phenanthrene and naphthalene

The syntheses of phenanthreneCr(CO)2L (L = PEt3, PBu3, PPh3, SbPh3, P(OMe)3, P(OEt)3, P(OBu)3 and P(OPh)3) and naphthaleneCr(CO)2L (L = PEt3, PBu3, PPh3 and P(OPh)3) are reported. The behaviour of these complexes as catalysts for hydrogenation of dienes is described and X-ray structural features of two complexes, phenanthreneCr(CO)2PEt3 and naphthaleneCr(CO)2P(OPh)3 are discussed in relation to their behaviour in catalytic reactions. It is suggested that stereoelectronic factors determine the catalytic properties of these complexes.

The use of conventional ventilators for high frequency positive pressure ventilation.

Ten randomly selected patients were ventilated for defined periods with 2 ventilatory modes: (a) high frequency positive pressure ventilation (HFPPV) (frequency 66-70 min; tidal volume 1-3 ml/kg body weight), (b) conventional IPPV (frequency 16/min; tidal volume (VT) 10-15 ml/kg). This was done successfully using conventional ventilators, and keeping other variables (FIO2, PEEP) constant. Various ventilatory and hemodynamic variables were measured and compared during both modes of ventilation. The most prominent finding was a considerable reduction of cardiac output (CO) and stroke volume (SV) during intermittent positive pressure ventilation (IPPV) compared with HFPPV. Peak tracheal pressure was significantly lower during HFPPV. An increase in mean systemic arterial pressure and in oxygen transport was observed during HFPPV, whereas transpulmonary shunt and pulmonary vascular resistance (PVR) decreased during HFPPV. These findings are in accordance with previously reported advantages of HFPPV, and might be of importance in the treatment of patients with bronchopleural fistula, adult respiratory distress syndrome (ARDS), left ventricular failure and other conditions in which conventional positive pressure ventilation (PPV) fails.