Utilizar BD SQL Server 2012

Olá Gabriel, eu tenho uma projeto com SQL Server, segue um exemplo de persistence.xml, faça os testes e ajuste as configurações conforme suas necessidades.

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <!-- SQL SERVER Persistence Unit -->
    <persistence-unit name="YOUR_UNIT">
        <description>Persistence Unit for all project!</description>
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.SQLServer2008Dialect" />
            <property name="hibernate.cache.use_second_level_cache"
                value="false" />
            <property name="hibernate.cache.use_query_cache" value="false" />
            <!-- dados da conexao -->
            <property name="javax.persistence.jdbc.driver" value="net.sourceforge.jtds.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:jtds:sqlserver://server/banco" />
            <property name="javax.persistence.jdbc.user" value="USER" />
            <property name="javax.persistence.jdbc.password" value="PASSWORD" />

            <!-- Disable the second-level cache -->
            <property name="cache.provider_class" value="org.hibernate.cache.NoCacheProvider" />
            <property name="hibernate.show_sql" value="false" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
        </properties>
    </persistence-unit>
</persistence>

Quanto ao Driver estou usando http://jtds.sourceforge.net, porem a própria Microsoft tem um driver para Java https://docs.microsoft.com/pt-br/sql/connect/jdbc/download-microsoft-jdbc-driver-for-sql-server.