211^At-BC8-B10 Before Donor Stem Cell Transplant in Treating Patients With High-Risk Acute Myeloid Leukemia, Acute Lymphoblastic Leukemia, Myelodysplastic Syndrome, or Mixed-Phenotype Acute Leukemia

Inclusion Criteria: * Patients must have AML, ALL, high-risk MDS, or MPAL (also known as biphenotypic) meeting one of the following descriptions: * AML, ALL, or MPAL in first remission with evidence of measurable residual disease (MRD) by flow cytometry * AML, ALL, or MPAL beyond first remission (i.e., having relapsed at least one time after achieving remission in response to a treatment regimen) * AML, ALL, or MPAL representing primary refractory disease (i.e., having failed to achieve remission at any time following one or more prior treatment regimens) * AML evolved from myelodysplastic or myeloproliferative syndromes * MDS expressed as refractory anemia with excess blasts (RAEB) * Chronic myelomonocytic leukemia (CMML) by French-American-British (FAB) criteria * Patients not in remission must have CD45-expressing leukemic blasts. Patients in remission do not require phenotyping and may have leukemia previously documented to be CD45 negative (because in remission patients, virtually all antibody binding is to non-malignant cells which make up \>= 95% of nucleated cells in the marrow) * Patients must be \>= 18 and =\< 75 years of age * Patients should have a circulating blast count of less than 10,000/mm\^3 (control with hydroxyurea or similar agent is allowed) * Patients must have an estimated creatinine clearance greater than 50/ml per minute by the following formula (Cockcroft-Gault); serum creatinine value must be within 28 days prior to registration * Pat…