I'm afraid the docs published on the website are a bit outdated, specifically they don't mention MongoDB yet.
This is a copy/paste from the documentation preview relative to MongoDB:
To use Hibernate OGM with MongoDB there are four properties to configure:
hibernate.ogm.datastore.provider to set to org.hibernate.ogm.datastore.mongodb.impl.MongoDBDatastoreProvider
hibernate.ogm.mongodb.host which is the hostname of the mongodb instance. The default value is 127.0.0.1
hibernate.ogm.mongodb.port which is the port used by the mongodb instance. The default value is 27017
hibernate.ogm.mongodb.database which is the database to connect to
To enable the safe mode (which means WriteConcern.SAFE for all operations) you have to use hibernate.ogm.mongodb.safe and set it to true
To build the documentation yourself (it's in docbook format in the sources, so you already have it):
mvn org.jboss.maven.plugins:maven-jdocbook-plugin:2.3.5:translate org.jboss.maven.plugins:maven-jdocbook-plugin:2.3.5:resources org.jboss.maven.plugins:maven-jdocbook-plugin:2.3.5:generate
So assuming you are using the default port, your persistence.xml looks like correct.
As mentioned, the exception you have shown means you are using the wrong version of Hibernate core. You must use Hibernate-core v. 4.1.4 , as indicated in the root pom.xml