The IPA for pinyin x
Help:IPA/Mandarin on Wikipedia has x listed like this:

Wiktionary:ɕ has audio you can listen to too.
This is a bit of a random source but here it is anyway.
《哈尔滨方言词典》[ɕi]

WordyEnglish's Pinyin 拼音, Zhuyin 注音, IPA Comparison also shows:


宣
ɕyɛn

Bopomofo letter ㄒ which represents &quot;x&quot; is also exclusively:

(phoneme) IPA(key): /ɕ/

From《漢語拼音方案》we can see the following:

where x again matches up with zhuyin ㄒ or IPA /ɕ/.

Sh on the other hand is listed as:

Wiktionary:ʂ also has audio you can listen too here.
《哈尔滨方言词典》[ʂɿ]

As you can see the two are very close in sound, and are often confused as such by learners.
Probably the biggest difference is tongue positions:

vs.