To do that you will need two blocks: division by 9 and multiplication by 2 ..
2/9 = 1/4.5 ..
To multiply be 2 you can use XOR gates (7486) and generate two pulses: one at the falling edge and one at the rising edge ..
To divide by 9 you can use 7490 decimal counter in :9 configuration ..
.. see pictures below ..
there is pdf called clock dividers made easy... i think it will be available in this forum... it contains synthesisable circuits for all sort of clock dividers withn explainations... try searching it...