This invention relates to a protected organotin-based catalyst system for polyurethane synthesis that is useful in coatings applications. The catalyst has a formula according to; R1aR2bR3cSn[CH(OX)R4]d, wherein R1, R2, and R3 are the same or different and represent an optionally substituted hydrocarbyl, aromatic, alkoxide, amide, halide or stannyl group, R4 represents an optionally substituted hydrocarbyl or optionally substituted aryl group. a, b, and c are independently 0, 1, 2, or 3; d is 1, 2 or 3; and a+b+c+d=4; and X is an acid-labile or moisture-labile protecting group. When a coating mixture comprising the catalyst is sprayed and/or applied to a substrate as a thin film in air, the catalyst is activated. For solvent-based refinish systems comprising hydroxyl and isocyanate species at high solids levels, the catalyst system therefore provides extended viscosity stability, i.e., pot life.