No abstract

No abstract

Thermolysis of Os 3 (CO) 11 (SbPh 3 ), 1, in refluxing octane gave initially the clusters Os 3 (µ-SbPh 2 )(µ-H)(µ 3 ,η 2 -C 6 H 4 )(CO) 9 , 2, and Os 6 (µ 3 -SbPh)(µ 3 ,η 2 -C 6 H 4 )(CO) 20 , 3. Prolonged heating gave the cluster Os 6 (µ 4 -Sb)(µ-H)(µ 3 ,η 4 -C 12 H 8 )(µ 3 ,η 2 -C 6 H 4 )(CO) 16 , 4, as the major product. In contrast, thermolysis in hexane at 115 °C in a Carius tube gave Os 6 (µ 4 -Sb)(µ-SbPh 2 )(µ-H) 2 -(µ 3 ,η 4 -C 12 H 8 )(µ 3 ,η 2 -C 6 H 4 )(CO) 15 , 5, Os 6 (µ 4 -Sb)(µ-SbPh 2 )(µ-H)(µ 3 ,η 2 -C 6 H 4 ) 2 (C 6 H 5 )(CO) 16 , 6, and Os 6 (µ 4 -Sb)(µ-SbPh 2 )(µ-H)(µ 3 ,η 6 -C 6 H 4 )(µ 3 ,η 2 -C 6 H 4 )(C 6 H 5 )(CO) 15 , 7, besides 2 and 3. It has been demonstrated that cluster 6 was formed from 2, while clusters 5 and 7 were formed from the further decomposition of 6. The reaction of 5 with SbPh 3 afforded a monosubstituted derivative, Os 6 (µ 4 -Sb)(µ-H) 2 (µ-SbPh 2 )(µ 3 ,η 2 -C 6 H 4 )(µ 3 ,η 4 -C 12 H 8 )(CO) 14 (SbPh 3 ), 8. The clusters 2-8 were all shown by single-crystal X-ray crystallographic studies to have a benzyne moiety acting as a four-electron donor to a triosmium fragment. In addition, 4 and 8 contain a novel µ 3 ,η 4 -biphenylene moiety bound to a triosmium framework, while 7 was found to have a µ 3 ,η 1 :η 1 :η 6 -C 6 H 4 ring.

A total of 134 bird species were recorded at Jianfengling, Hainan Island, in China from May 2000 to September 2004, of which 44 participated in one or more of 134 mixed‐species flocks. These flocks averaged 3.8 ± 0.2 species and 20.3 ± 1.2 individuals. Flocking propensity in a given species ranged from 1.5 to 100%. For flocking species, frequency of flocking and number of individuals in flocks was positively correlated with frequency and number in point counts. Among all species pairs with flocking frequency above 5%, cluster and correlation analysis indicated there were two principal groups of flocking birds – canopy species and understorey species: associations were positive within a group, but negative between groups. Canopy birds had a higher flocking propensity than understorey birds. They also made significantly less use of inner branches and trunks and greater use of middle branches, and foraged at a significantly greater height when in mixed‐species flocks than when solitary. For understorey bird species, there were no significant differences in foraging locations between solitary and mixed‐species flocks. Higher flocking frequency occurred in the wet season for canopy birds, but in the dry season for understorey birds. Overall patterns were consistent with the explanation that flocking enables an expansion of foraging niche by reducing the risk of predation.

No abstract