The situation of the Wittgensteins in Vienna after the Anschluss is discussed by Ray Monk on pp.396-400 of his "Ludwig Wittgenstein: The Duty of Genius" (Jonathan Cape, 1990), which is widely regarded as a model of philosophical biography.
According to Monk, the story has three stages.
First, LW's brother Paul went to Berlin after the Anschluss to ask the Nazis for the family to be treated as Aryans, on grounds of long and patriotic service to the Austrian state, etc., but they refused.
Second, a cousin, Brigitte Zwiauer, attempted to prove that LW's grandfather Hermann Christian Wittgenstein was "really" an Aryan, and that he was the illegitimate offspring of the aristocratic Waldeck family rather than the son of Moses Maier, but this attempt foundered in the face of opposition from LW's three sisters, who didn't want to have anything to do with this nonsense.
Third, in the winter of 1938-9, the Reichsbank became interested in the foreign currency fortune of the Wittgensteins. Monk writes: "Under Nazi law, the Reichsbank was empowered to compel the family to hand this money over to them. Owing to the complicated arrangement under which the wealth was held, however, it was difficult for them to get their hands on it. This circumstance suggested to Gretl [one of LW's sisters] another possibility of securing the safety of her sisters [Helene and Hermine; Gretl had a US passport, so was not really at risk]: they would agree to hand over the foreign currency in return for a written declaration that Hermine and Helene would be treated as Aryans".
After lengthy negotiations the Nazis agreed to accept the report prepared by Zwiauer in return for the transfer of the Wittgenstein funds. Paul -- now living in Switzerland -- opposed doing a deal with the Nazis. Ludwig received his British passport in June 1939 and went to Berlin, Vienna and New York over the summer in order to try to help Gretl reach a settlement, although Monk is vague (possibly because there are no good records) of what he said, and to whom, in the various discussions, commenting only that he "entered into the negotiations with all the considerable precision and tenacity at his disposal". In August 1939, the Wittgenstein wealth was transferred out of a Swiss bank account and the Nazis certified that the Wittgenstein sisters were "Mischlinge" rather than Jews. "Later, in February 1940, the Berlin authorities went further, and issued a proclamation that the regulations covering Mischlinge were not applicable to the descendants of Hermann Christian Wittgenstein...", and Helene and Hermine survived the war in Vienna reasonably untroubled.
So yes, LW did get involved in negotiations with the Nazis, but no, it was not his money, as someone pointed out: he renounced his share of the family wealth after WW1.
Chris.
Chris. --