No. They were both enormously influential, though.
IBM S/360 got there before the PDP-11 (1964 vs 1970) -- but it probably also wasn't the first.
https://en.wikipedia.org/wiki/IBM_System/360
Unix was developed on a PDP-11 (I ignore the first, embryonic, version on an 18-bit PDP-7 because that version was in assembler and couldn't really do much more than host Space War). The real, grown-up, version of Unix with proper virtual memory was developed on a VAX (as part of BSD Unix). Sockets also came from BSD Unix, developed on VAX.
IEEE floating-point is largely based on their floating-point format -- but it is incompatible and has a number of extra bells and whistles that William Kahan insisted on.
They were also used for developing various experimental programming languages.
Windows NT is in many ways a reimplementation of DEC's VMS operating system for the VAX.
The PDP-11/74 was an early experimental 4-way SMP machine -- that quickly taught the OS developers that they didn't know as much as they thought about how to write SMP software!
