Anil,
I am not sure what module or routed port on the 3745 that you tried to configured port-channel.
If you are using 16 etherswitch module, you can configure up to 8 interfaces per Etherchannel.
The EtherSwitch modules support a maximum of eight interfaces per EtherChannel when you have set all interfaces in the EtherChannel at the same speed/duplex.
Make sure you have the same speed/duplex
Hope it helps