Create 'Dummy' Rows

Guys - scenario/DDL/DML below

Create table #Periods (Period INT , Frequency INT , startdate datetime NULL , enddate datetime NULL )
insert #Periods (Period , Frequency , startdate , enddate)
select 0 , 3 , '01-Nov-2004' , '30-Nov-2004'
union all
select 1 , 3 , '01-Dec-2004' , '31-Dec-2004'
union all
select 2 , 3 , '01-Jan-2005' , '31-Jan-2005'
union all
select 2 , 6 , '01-Nov-2004' , '30-Nov-2004'
union all
select 3 , 6 , '01-Dec-2004' , '31-Dec-2004'
union all
select 4 , 6 , '01-Jan-2005' , '31-Jan-2005'

select * from #periods
Period Frequency startdate enddate
03 2004-11-01 00:00:00.0002004-11-30 00:00:00.000
13 2004-12-01 00:00:00.0002004-12-31 00:00:00.000
23 2005-01-01 00:00:00.0002005-01-31 00:00:00.000
26 2004-11-01 00:00:00.0002004-11-30 00:00:00.000
36 2004-12-01 00:00:00.0002004-12-31 00:00:00.000
46 2005-01-01 00:00:00.0002005-01-31 00:00:00.000


For any frequency (in this simple example 6) where the 'lowest' period is not 0, I need to create dummy rows
so here I need to create the following
Period Frequency startdate enddate
06 NULL NULL
16 NULL NULL

I've built a temp table to identify the min period for each Frequency but am not sure where to go from here using this to do the inserts ?
select
min(Period) as MinPeriod ,
ResetFrequency
into #Periods2
from #Periods
group by ResetFrequency

select * from #CashFlow2
MinPeriodResetFrequency
03
16