OK. Looks like the ".parsed" was interfering with the call here's what works, with some additions to the request object:
response = access_token.put('https://www.googleapis.com/groups/v1/groups/{email address}') do |request|
request.headers['Content-Type'] = 'application/json'
request.body='{"email": "{email address}"}'
end
# check this
puts response.status
# works if it's 200