PCRE regex to sed regex -

first of sorry bad english. i'm german guy.

the code given below working fine in php:

$string = preg_replace('/href="(.*?)(\.|\,)"/i','href="$1"',$string); 

now t need same sed. thought should be:

sed 's/href="(.*?)(\.|\,)"/href="{$\1}"/g' test.htm 

but gives me error:

sed: -e expression #1, char 36: invalid reference \1 on `s' command's rhs

sed -e 's|href=\"\(.[^"][^>]*\)\([.,]\)\">|href="\1">|g' file