De Leede starred with bat and ball, picking up a first ODI five-for before smashing 123 with the bat to haul the Netherlands home and punch their tickets to India later this year.
Having put Scotland into bat, Netherlands made the perfect start as Logan van Beek (1/49) struck in the first over to dismiss Matthew Cross (0).
But Scotland steadied the ship through Christopher McBride (32) and Brandon McMullen (106) before opener McBride became the first of De Leede’s five scalps, pulling straight into the hands of Van Beek at midwicket with George Munsey (9) falling shortly after.
But McMullen began to take control of the innings on the way to the second century of his career alongside Richie Berrington (64).
The pair combined for a stand of more than 150 runs to leave Scotland in rude health at 201 for four by the time McMullen was eventually caught behind by Scott Edwards off the bowling of Ryan Klein.
Klein then bowled Michael Leask (1) before De Leede removed Berrington’s middle stump, but Scotland rallied through an unbeaten 38 off 28 balls from Tomas Mackintosh as well as a useful knock from Chris Greaves (18) to set the Dutch 278 in 44 overs to book their place at the World Cup.
Netherlands began their innings quickly, with openers Max O’Dowd (20) and Vikramjit Singh (40) taking just 8.2 overs to bring up their 50 partnership, before Leask trapped O’Dowd leg before.
Leask repeated the trick in his next over, this timing sending Singh back to the hutch as Scotland began to slow the run rate.
Having starred with the bat, McMullen then made his first contribution with the ball with the wicket of Wesley Barresi (11) to leave Netherlands on 94 for three after 20 overs.
Teja Nidamanuru (10) was next to fall four overs later as Chris Greaves earned his first scalp of the afternoon but De Leede (123) and Scott Edwards (25) combined to rejuvenate the Dutch chase, bringing up 50-run stand in just 40 balls before Edwards fell to Mark Watt LBW.
De Leede then opened up, powering past 50 in 55 balls before reaching his century in just 84 alongside Zulfiqar (33), as the pair combined to produce a huge final few overs to surmount the 50 runs required from the final four overs to seal qualification in stunning fashion.
UAE edge USA for ninth
An unbeaten 151 from Asif Khan powered UAE to a narrow victory over USA by just a single run in Harare.
Khan produced an impressive knock to help his side post 308 for four, their highest total of the tournament, but middle over contributions for USA from Monank Patel (61), Aaron Jones (75), and Gajanand Singh (69) set up a grandstand finish.
But the American tail were unable to get their side over the line, as two wickets in the final over from Sanchit Sharma sealed victory.
It was the opening partnership that proved so devastating for UAE, as Sharma (57) and Khan combined for an initial stand of 107 before the former was caught and bowled by Nosthush Kenjige.
Khan was simply unstoppable for UAE, inspiring his side’s total to the brink of 300 alongside Basil Hameed (44), before hitting his 18th boundary of the innings to set USA 308 to win.
USA started brightly in their chase, with Saiteja Mukkamalla hitting a quickfire 21 off 17 balls alongside Sushant Modani (9) as the Americans raced to 32 off the first six overs before Mukkamalla fell to Muhammad Jawadullah.
Modani followed just two balls later to leave USA 32 for two but Patel and Jones combined to lift their side to a much healthier 144 for three before Patel was bowled by Aayan Afzal Khan with 20 overs remaining.
A rapid 69 from just 44 balls from Singh then shifted the momentum of the match with USA left needing 62 from the remaining 46 balls as Singh was eventually dismissed by Junaid Siddique.
Shayan Jahangir (32) led the final run chase to set up a nervy finish, with USA requiring 11 from the final over to win.
But Sharma dismissed both Nisarg Patel and Ali Khan in the final over to ensure UAE sneaked over the line and sealed ninth.
Sri Lanka and Windies round off Super Six
The Super Six comes to a close tomorrow, as already qualified Sri Lanka take on West Indies in Harare.
Windies have endured a torrid time so far in Zimbabwe, but will be hopeful of ending their campaign with what would be an impressive victory over table-toppers Sri Lanka.
The Lions now know they will face Netherlands in Sunday’s final and will hope to continue their momentum with another strong display.