After changing my List vom ng-repeat to collection-repeat ng-click is not working properly

I had a List like this:

<ion-item ng-repeat="item in items" ng-click="itemClick({{item[0]}})">
    ...
</ion-item>

now I changed it to:

<ion-item collection-repeat="item in items" ng-click="itemClick({{item[0]}})">
    ...
</ion-item>

while having the following code in my controller:

$scope.itemClick = function (index) {
    // index is undefined
};

before making the change from ng-repeat to collection-repeat all works fine. Now I get index as undefined.

Whats wrong here?

EDIT:

Here are my items:

var items = {
    [1, "foo"],
    [2, "bar"], 
    ...
}

{{}} Iterpolation won't work inside ng-click, you can directly mention variable name that will directly gets fetched from their respective variable.

ngClick clearly states that it accepts an expression: http://docs.angularjs.org/api/ng.directive:ngClick

Markup

<ion-item collection-repeat="item in items" ng-click="itemClick(item[0])">
    ...
</ion-item>

try this 

<ion-item collection-repeat="item in items" ng-click="itemClick(item[0])">
    ...
</ion-item>

if you want only index value, then try this below 

<ion-item collection-repeat="item in items" ng-click="itemClick($index)">
    ...
</ion-item>

{{}} won't work inside ng-click, just del{{}}, use itemClick(item[0]).