Well... It's even interesting.
Russian - it's Ukrainian language, and Church-slavonic - it's moscovian language. So you shouldn't compare Church-slavonic to Russian because it have different rules of pronouncing of some letters and different evolution of languages at all.
" Киѣвъ " sounds in English like " Kyjev ", "Kyyev ", " Kyjiv ", " Kyyiv " or " Kyiv ". Because sounding " и " is hard ( Kyi ), not soft ( Kei ). As I wrote, in 12 century name changed to " Киѣвъ " ( or " Кыѣвъ ", " Кіѣвъ " ). At this time all three letters " и, ы, і " merged and had one sound - ɨ
https://en.wikipedia.org/wiki/Close_central_unrounded_vowel ( press " play clip " to listen to it ). So if you want to write it in English use only this symbol - y.
And if you remember before 12 century name of Kyiv was - Кыѥвъ. Where ы had this sound -
https://en.wikipedia.org/wiki/Close_central_unrounded_vowel . And ѥ had - " je " or " ye " sound
https://translate.google.com.ua/?hl=uk&tab=TT&authuser=0#view=home&op=translate&sl=uk&tl=en&text=є ( modern ukrainian letter - є ).
Letter ѣ from 12 century has a lot of pronouncing ( " ɛ ", " ie ", " æ ", " e ", " i " ) but you can see logic here: if 100 years ago Kyiv has " ye " or " je " sounds - Kyjev/Kyyev ( original: Кыѥвъ - Києв ), it should have soft sound in 12 st. too - " ji " or " yi " - Kyjiv/Kyyiv ( original: Киѣвъ - Київ ) .
And right now it's Kyiv. And I think name of this city didn't change a lot from that time ( from 12 to 16 century ).
That's why correct versions of historical name of Kyiv is -
Kyjev, Kyyev, Kyjiv, Kyyiv or Kyiv but not - " kiev ".