Q. Since Y’kum Purkan was meant as a prayer to be recited by the Chazan, and according to our Minhag, when in Shul only the Chazan says it aloud, does one refrain from saying it if there is no Minyan?
A. Most Sidurim instruct that Yikum Purkan should not be said when there is no minyan present. Some maintain that then only the second one should be avoided or at least the words addressing the ‘Kahalo Kadisho Hadein'(This Holy Congregation) should be omitted (Seder Tefilah p. 443).
A reason mentioned why it is not recited without a minyan is that when no minyan is present there is a lack of the proper presence of the Shechina to accept the Tefilos said and the Malachim (angels) also do not attend to the Aramaic language (Bonim Chavivim 359 and others).
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a