* Dortmund sneak into knockout stage
* Arsenal through, Napoli out
* Galatasaray, Schalke 04 and Zenit progress
* Milan only Italian team in last 16
* Neymar hat-trick as Barca hit six
By Justin Palmer
LONDON, Dec 11 (Reuters) - Last season's runners-up Borussia Dortmund were spared a Champions League exit when a dramatic late goal from Kevin Grosskreutz sent the German side into the last 16 on Wednesday.
Dortmund, who beat Olympique Marseille 2-1, Arsenal and Napoli all finished on 12 points with the Bundesliga team topping Group F and the Italians proving the odd side out on head-to-head superiority despite a 2-0 victory over the English Premier League leaders.
AC Milan will be Italy's only representatives in the knockout stage as Galatasaray, Zenit St Petersburg and Schalke 04 secured the remaining last 16 places in Monday's draw which will feature four representatives each from the Premier League and Bundesliga.
Barcelona, who should have Lionel Messi back from injury when the competition resumes in February, signed off from the group phase in style with Brazil striker Neymar scoring a hat-trick, his first Champions League goals, in a 6-1 romp over Celtic at the Nou Camp.
Jose Mourinho can also look forward to the draw as Group E winners Chelsea went through the motions in overcoming Steaua Bucharest 1-0 at Stamford Bridge.
Napoli, who drop into the Europa League, are only the second team to be eliminated from the group phase with 12 points from six games after Paris St Germain in 1997-98.
In contrast, Russia's Zenit finished runners-up in Group G by becoming the first team to qualify for the knockout stages with six points.
Injury-hit Dortmund were just minutes away from a trapdoor into Europe's second-tier competition when Grosskreutz found the back of the net with a deflected shot three minutes from time against 10-man Marseille.
"It was great feeling to score and to score such a goal. We deserved it, it was sensational," said the match-winner.
Napoli's victory, secured with late fforts from Gonzalo Higuain and Jose Callejon, the second deep into stoppage-time, could not save Rafa Benitez's side from an agonising exit as Arsenal had to lose by three goals in order to miss out on qualification.
"We are happy to be through because it was very difficult," said Arsenal manager Arsene Wenger.
"Naples played very well tonight but we were a little bit on edge for some minutes, it was nervous in the end, but we got through."
It was the 14th season in a row that Arsenal, who had captain Mikel Arteta sent off for a second bookable offence in the 75th minute, have reached the last 16.
Seven-times European champions AC Milan clung on with 10 men for a point at home against Ajax Amsterdam to finish runners-up behind Barca in Group H and earn some respite in a below-par season.
Milan had captain Riccardo Montolivo sent off midway through the first half but Ajax could not take advantage and secure the victory they needed to leapfrog the hosts.
Christian Poulsen hit the post for the Dutch side after five minutes and Milan keeper Christian Abbiati was forced into a number of saves.
Galatasaray ended the campaign of Italian champions Juve with a 1-0 success in Istanbul, Wesley Sneijder hitting a late winner in a game re-started on Wednesday following Tuesday's abandonment because of heavy snow.
On a slippery pitch, Sneijder broke the deadlock in the 85th minute as Galatasaray's win lifted them above Juve in Group B.
"That goal is very important for me but even more important for the club," Dutch international Sneijder said.
The Turkish side's goal difference of minus 6 is the lowest of any team to qualify from a Champions League group, eclipsing the minus 4 of Norway's Rosenborg in 1996-97.
Zenit went through despite a 4-1 humbling at Austria Vienna, finishing a point ahead of Porto who lost 2-0 at Group G table-toppers Atletico Madrid.
Schalke beat Basel 2-0 to deny the Swiss side second spot in Group E, helped by a fine goal from Julian Draxler and a clearly offside effort from Joel Matip. (Editing by Ed Osmond)