First-half headers from McDonald and Gary Caldwell looked to have put the home side into an unassailable lead but the Scottish Premier League champions were pegged back by Adam Coakley's 65th-minute strike.

The Spiders substitute - on for Ian Watt five minutes earlier - was shown a yellow card for celebrating his goal before he was sent off 11 minutes from the end after picking up a second caution for a foul on Celtic defender Lee Naylor.

Falkirk secured its first win at Hearts in almost 14 years to book a quarter-final place after an incredible second half at Tynecastle.

Steve Lovell's hotly-disputed 59th-minute winner handed the Bairns a 1-0 victory in a fifth-round tie which saw both teams finish with 10 men.

Hearts had looked the side most likely to break the deadlock before Lovell struck, with the visitors thankful to a superb display in goal from Dani Mallo.

Further controversy raged soon after Lovell's goal when referee Dougie MacDonald awarded Hearts a penalty only to change his mind after consulting with his assistant.

Marius Zaliukas and Scott Arfield both saw red late on - nine cautions and two reds were dished out in all - as John Hughes' men survived to seal a fine win.

A Chris Swailes double saw Hamilton book their place in the quarter-finals as Dundee United once again failed to overcome the Accies.

It was United which looked set to progress in the competition when Danny Grainger opened the scoring and provided the visitors with a first-half lead.

But two goals from Swailes within 10 minutes of the restart put the Accies in the driving seat and they held on to win 2-1 and ensure their name would be in the hat for the last-eight draw.

Inverness were comfortable 2-0 winner against Kilmarnock.

Latvian defender Pavels Mihadjuks gave Caley Thistle a half-time lead when he rose highest to head home Ian Black's centre.

Killie then had Kevin Kyle sent off before Adam Rooney's stoppage-time strike sent them back down the weather-hit A9 empty handed.

Stephen Hughes kept Motherwell in the competition with a second-half equaliser against St Mirren in a poor 1-1 draw on a terrible Fir Park pitch.

Andy Dorman gave Saints an early lead and Motherwell struggled with their passing game on the bumpy surface.

But they pushed more men forward after the break and finally carved out a chance for Hughes to finish in the 65th minute.

Aberdeen's clash with East Fife was postponed, with the roads in the surrounding area deemed unsafe.

Airdrie's tie with Dunfermline was also called off due to a frozen pitch.