In the past, Internet Explorer versions 4.0 to 8.0 had a non-standard "filter" property that is now deprecated, IE 11 no longer supports this property.
To achieve greyscaling in IE 11, you could utilize an SVG overlay. Here's an example:
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
img.grayscale:hover {
filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'1 0 0 0 0, 0 1 0 0 0, 0 0 1 0 0, 0 0 0 1 0\'/></filter></svg>#grayscale");
}
svg {
background: url(http://4.bp.blogspot.com/-IzPWLqY4gJ0/T01CPzNb1KI/AAAAAAAACgA/_8uyj68QhFE/s400/a2cf7051-5952-4b39-aca3-4481976cb242.jpg);
}
svg image:hover {
opacity: 0;
}
</style>
</head>
<body>
<svg xmlns="http://www.w3.org/2000/svg" id="svgroot" viewBox="0 0 400 377" width="400" height="377">
<defs>
<filter id="filtersPicture">
<feComposite result="inputTo_38" in="SourceGraphic" in2="SourceGraphic" operator="arithmetic" k1="0" k2="1" k3="0" k4="0" />
<feColorMatrix id="filter_38" type="saturate" values="0" data-filterid="38" />
</filter>
</defs>
<image filter="url("#filtersPicture")" x="0" y="0" width="400" height="377" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://4.bp.blogspot.com/-IzPWLqY4gJ0/T01CPzNb1KI/AAAAAAAACgA/_8uyj68QhFE/s1600/a2cf7051-5952-4b39-aca3-4481976cb242.jpg" />
</svg>
</body>
(source: )
Simplified JSFiddle: http://jsfiddle.net/KatieK/qhU7d/2/
For more information about SVG filters, you can visit this blog post.
If SVG filter doesn't work for you, consider using the CSS Opacity property as an alternative method.