Severity: Warning
Message: file_get_contents(https://...@pubfacts.com&api_key=b8daa3ad693db53b1410957c26c9a51b4908&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 176
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 176
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 250
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3122
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
Chiral rhodium-diphosphine complexes have been incorporated into self-assembled thiolate monolayers (SAMs) on gold colloids. Catalysts of this type are of interest because they combine properties of homogeneous and heterogeneous systems. In addition, it should be possible to influence the catalytic properties of the metal center by the neighboring thiolate molecules. Colloids with a diameter of ca. 3 nm, coated with a mixed monolayer of n-octanethiolates and thiolates with chiral rhodium-PYRPHOS end groups, were studied as hydrogenation catalysts. With methyl alpha-acetamido-cinnamate as substrate, virtually the same enantioselectivities (up to 93% ee) and full conversion were obtained as with the corresponding homogeneous [Rh(COD)(PYRPHOS)]BAr(F) catalyst. The colloids were easily recovered by filtration and reused as catalysts three times without loss of enantioselectivity. STM studies of analogous SAMs on Au(111) gave a detailed picture of the structure and dynamics of mixed monolayers of this type. The STM images showed that the catalyst-bearing thiolates are distributed statistically on the surface and that the ordered structure of the n-octanethiolate SAM can be retained during incorporation of the catalyst-bearing thiols using the place-exchange methodology.
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Source |
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http://dx.doi.org/10.1021/ja0500714 | DOI Listing |
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