The FSB is the maximum speed the memory can have. not the only speed it can have. When these processors came out DDR3 was a research topic, like DDR4 is now. To use 1600MT RAM you will need DDR3, or severely overclocked DDR2 (thinking 1066 with some mad FSB adjustments). Either way, DDR2 will not hold you back unless you are using a program that is heavily dependent on memory bandwidth.
Basically I am assuming you are asking if there is DDR2 that will work with 1600MT FSB processors. That is a yes. The question you asked, no that does not exist. Memory does not have a front side bus.