SQL Server 2012 :: Why Partition Function Works For Datetime2 But Not For Datetime1

DECLARE @DatePartitionFunction nvarchar(max) = N'CREATE PARTITION FUNCTION DatePartitionFunction (datetime) AS RANGE RIGHT FOR VALUES (';
DECLARE @i datetime = '2007-09-01 00:00:00.000';
WHILE @i < '2008-10-01 00:00:00.000'
BEGIN
SET @DatePartitionFunction += '''' + CAST(@i as nvarchar(10)) + '''' + N', ';

[Code] ....

Msg 7705, Level 16, State 2, Line 1
Could not implicitly convert range values type specified at ordinal 1 to partition function parameter type.

However if I change to datetime2 it works

DECLARE @DatePartitionFunction nvarchar(max) = N'CREATE PARTITION FUNCTION DatePartitionFunction (datetime2) AS RANGE RIGHT FOR VALUES (';
DECLARE @i datetime2 = '2007-09-01 00:00:00.000';
WHILE @i < '2008-10-01 00:00:00.000'
BEGIN
SET @DatePartitionFunction += '''' + CAST(@i as nvarchar(10)) + '''' + N', ';

[Code] ...

Is the data type of the column used for partitioning. All data types are valid for use as partitioning columns, except text, ntext, image, xml, timestamp, varchar(max), nvarchar(max), varbinary(max), alias data types, or CLR user-defined data types.

In this case why isn't datetime works?

version is as follow:

Microsoft SQL Server 2012 (SP1) - 11.0.3128.0 (X64)
Dec 28 2012 20:23:12
Copyright (c) Microsoft Corporation
Enterprise Evaluation Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)

from [URL] .....

Table and index partitioning is supported in this edition

so I don't know why it fails!