Use Oracle 11.2 and check supported platforms using My Oracle Support notes:
As of Oracle Database 11g, Data Guard provides increased flexibility for Data Guard configurations in which the primary and standby systems may have different CPU architectures, operating systems (for example, Windows & Linux), operating system binaries (32-bit/64-bit), or Oracle database binaries (32-bit/64-bit).
This increased mixed-platform flexibility is subject to the current restrictions documented in the My Oracle Support notes 413484.1 and 1085687.1 at http://support.oracle.com. Note 413484.1 discusses mixed-platform support and restrictions for physical standbys. Note 1085687.1 discusses mixed-platform support and restrictions for logical standbys.
The same release of Oracle Database Enterprise Edition must be installed on the primary database and all standby databases, except during rolling database upgrades using logical standby databases.
quoted from http://download.oracle.com/docs/cd/E11882_01/server.112/e17022/standby.htm#i72053.