Complexes with the general formula [LnM(CO)m], where [Formula: see text] x = 0–2, n = 1 or 2, M = Mo(0) or W(0), m = 3 or 4, were prepared by thermal or photolytic methods by the reaction of the appropriate 3,5-dimethylpyrazolyl phosphine ligand with M(CO)6, norbornadienemetaltetracarbonyl [C7H8M(CO)4], cycloheptatrienylmetaltricarbonyl [C7H8M(CO)3], [(Me2N(CH2)3NMe2)M(CO)4], [(CH3CN)2M(CO)4], or [(CH3CN)3M(CO)3]. Structural evidence indicates octahedral geometry about the metal atom centre, and several modes of coordination for the ligands in those complexes isolated and characterized. For x = 2, the ligand [Formula: see text] was monodentate, via phosphorus in [Formula: see text] and bidentate in [Formula: see text] where coordination by P and the 2N site of the pyrazolyl ring yielded four-membered [Formula: see text] metallocycles. For x = 1, the [Formula: see text] ligand was bidentate, via the phosphorus atom and one of the 2N sites of one of the pyrazolyl substituents, thus giving the four-membered [Formula: see text] metallocycle in [Formula: see text] and tridentate in [Formula: see text] where three facial CO's, two 2N atoms of the pyrazolyl rings, and a part of the phenyl ring occupy the six coordination sites. For x = 0, the P(Me2pz)3 ligand was tridentate via the 2N atoms of all three pyrazolyl rings, thus giving tricyclic systems [P(Me2pz)3M(CO)3] (VIII, IX).
A further survey in East Caprivi, Chobe National Park, Okavango swamps and Kavango was undertaken in June 1976. No evidence of lechwe schistosomes was found in droppings of African buffalo (Syncerus caffer) nor baboons (Papio ursinus) living in lechwe habitats. It was thought that they were not capable of spreading or maintaining these parasites outside the confines of the known distribution of Kobus sp. The role of goats was equivocal but probably they too are poor hosts.Kavango, an endemic area of S. haematobium and S. mansoni, was thought to be free of all animal schistosomes, thus confirming the hypotheses that (1) cattle and goats are poor hosts of the lechwe schistosomes and (2)S. mattheei was blocked from entering the territory by the presence of lechwe schistosomes in the surrounding areas. Evidence of schistosomes was not found in cattle and goats at Maun for the same reasons. The prevalence of S. mansoni at Maun has increased alarmingly over the past 20 years with a simultaneous disappearance of lechwe from the area. S. margrebowiei and S. leiperi eggs were found in lechwe and tsessebe droppings some 80 km north of Maun.A high proportion of children with negative excreta from “non-endemic” areas in East Caprivi had positive CFT and/or skin tests, suggestive of exposure to lechwe schistosomes resulting in a possible immunity to S. mansoni and S. haematobium.
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