#1 - you're over the cap
#2 - Plekanec is worth a 2nd alone at trade deadline to a cup contender.
#3 - what do the habs get for retaining salary and helping out the Pens? (nothing is free in this world and they're not gonna retain half his salary out of the goodness of their hearts).

#1 - Cap is pro rated, which is not reflected in this site. Pens could make this work cap wise.
#2/#3 - Almost no contenders have room for a 6 million dollar player at this point in the season, and Plek's play has been much more like a $3M center rather than a $6M one. Most of his salary has been paid out already so the Habs retaining really doesn't cost the Habs much actual money at this point. Retaining salary is a necessary thing for dealing to contenders at the deadline. I highly doubt you are getting a 1st round pick for a mediocre, expiring 3C.

nobody mentioned getting a 1st.
Actually, this site does take into account pro rated cap space>
PROJECTED CAP HIT Tooltip : $74,884,690
PROJECTED LTIR USED Tooltip : $84,259
PROJECTED CAP SPACE Tooltip : $199,569
CURRENT CAP SPACE Tooltip : $713,843
DEADLINE CAP SPACE Tooltip : $927,996
TODAYS CAP HIT Tooltip : $75,713,021

Even with the pro rate - the PENS have no cap space - so at the very least a similar roster player (6M) has to be coming back in return in order to land Pleks.
If not, then the Habs can retain half his salary and at even then a roster player with 3M cap hit has to be coming back in return - and they're not going to do that for free.
So, like I said before a 2nd rounder + a roster player is bare minimum if they're retaining salary.

1. A player’s cap is prorated daily against a team’s salary allotment, with the trade deadline timing a team would be assuming approximately 25% of the remaining ca p hit for the season. In Plekanec’s case this is ~$1.5mil. Assuming 50% retention that’s $750k. The above estimate from Capfriendly indicates an estimated $970k available to the Pens so they have the room to add him.
2-3. Montreal fans grossly overestimate the value of Plekanec on the trade market. Any team looking to acquire him knows he won’t return to them next year, and any trade will likely have a conditional pick based on where he signs as a UFA. Other less talented players have drawn higher picks because a team is expecting the possibility of retaining that asset. Moving Plekanec is also contingent on whether the Rangers or Senators move any of their far more valuable center assets, taking away more likely suitors in San Jose or elsewhere looking for center depth.
Likely deal is a 3rd with a conditional 2nd upgrade based on where Plekanec goes as a UFA.

where are those nay sayers now??????

I called it and everyone said I was overrating Pleks.
He's worth a 2nd rounder alone - retained salary throws more moving pieces MTL way.
Glad to see I was right in the recent trade with Tor.