They did. I'll copy some relevant sections of an answer I wrote about foreign intervention in the Russian Civil War:

The Bolshevik government had asked for an armistice with Germany on December 15, 1917, and after very long, complicated and rancorous negotiations, the Bolsheviks and the Central Powers had signed the Treaty of Brest Litovsk on March 3, 1918 (the Bolshevik government heatedly debated this treaty and narrowly approved it). One of the major reasons that the Bolshevik government decided to sign was that the Germans had rejected the "neither war nor peace" position advocated by Trotsky (ie, that the Bolsheviks would neither continue fighting a war against the Central Powers, but also not sign a formal peace treaty). This had led to a resumption of hostilities on February 18 and a massive offensive by Central Powers forces, leading to the occupation of the Baltic region and Ukraine.

These peace terms saw Russia cede Finland, Poland, the Baltics and Ukraine (as well as bits of the Caucasus) . These territories contained maybe half of the population of the former Russian Empire, much of its industry, and most of its resources such as coal mines, oil fields, and crucially Ukrainian wheat. Something like a million Central Powers troops occupied those ceded territories. The Bolshevik government and the German Empire established formal diplomatic relations, and even exchanged ambassadors, and while the Bolshevik government repudiated tsarist-era debts, a financial agreement with Germany in August 1918 saw compensation offered to German bondholders in an attempt to get German industrialists and financiers to invest in Russian reconstruction (the German Foreign Ministry had a standing committee including representatives from Krupp and Deutsche Bank to look into the matter).

All of this occurred at a time that the Central Powers launched massive spring offensives on the Western Front. Germany even drew up a military contingency plan in September 1918, known as Operation Capstone, which would have seen German and Finnish forces occupy Petrograd at the invitation of Lenin's government. In the event, Lenin understandably wasn't interested, and the reversal of fortunes on the Western Front plus opposition from the German Foreign Ministry saw this plan shelved.