is the reason you can't intsall 10.7 because of the new connector, or because iOS 6 requires 10.7? (if it's the latter issue, you're stuck unable to update)
The reason is because OS X releases starting at 10.6 Snow Leopard no longer support PowerPC.
http://en.wikipedia.org/wiki/Mac_OS_X_Snow_Leopard
This is also the first Mac OS release since System 7.1.1 that does not support Macs that use PowerPC processors, as Apple now intends to focus on its current line of Intel-based products.
http://en.wikipedia.org/wiki/Mac_OS_X_Snow_Leopard#System_requirements